Chapter 6-Scan Parameters - Hitachi Healthcare€¦ · Scan Parameters 0 Figure 6-9. The Scan...

Chapter 6-Scan Parameters

QS4·53287v4

This chapter describes the Scan Parameters area of the Exam window and

provides detailed information about each parameter. These selections allow you

to customize your scans and processing in various ways.

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0AS Is~ MRI System Reference Manual T'hoe htlent MqiMt

Scan Parameters Area

6-2

The default location of the Scan Parameters area is on the right side of the Exam

window, as shown in figure 6- 1. The Scan Parameters area can be displayed on

either side of the Exam window. To change the display location, refer to the

"Displaying the Scan Parameters Area" section in this chapter.

Figure 6-1. The default location for the Scan Parameters area.

This area contains two tabs:

• Basic-Contains the 12 default parameters and any parameters that have been

added to the tab.

• All -Contains a ll the parameters in the Oasis MR System, including the

default parameters listed on the Basic tab.

These tabs are described in the fo llowing sections.

Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

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Scan Parameters 0 Basic Tab

The Basic tab contains the following 12 default parameters, as shown in figure

6-2:

• FOV

• TR

• TE

• FA

• Thickness

• Interval

• Multi slice

• Freq#

• Phase#

• NSA

• Sync. Stop Watch

• Gating

FOV 340

1800

150 0

90 __=} .. 1 ... ]

-l.__~~o-o --===?]-+: 1::::::::: 1

-~ r:r:l - ....... 2s_s--==--=-I.. ..

164 =--r_TI Sync Srop•Natct·, off

- off

Figure 6-2. The 12 default parameters on the Basic tab.

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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt

6-4

This tab also contains any parameters that have been added. To add a parameter

to the Basic tab, follow these steps:

I. Click the All tab and drag the scroll box to the bottom of the scro ll bar to

reveal the Config button, as shown in figure 6-3 .

Click MIP Image

DC Level

W-VV1dthl

VV·Levell

Slice Ord A

Slice Ord S

Slice Ord C

Plane Order

Rad1al Stack

L1ne/Box

Gu1de Line

1:.1nM

Sync

ReceiVer C01l

Mode

TM Program

Figure 6-3. Adding a parameter to the Basic tab.

Drag scroll box to bo:tom of scroll bar


Note: Changes made to the Basic tab apply to all Exam windows, not just the one currently in use.

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Scan Parameters 0 2. Click the Config button. The Config Setting window opens, as shown in

figure 6-4. Parameter check boxes that are selected and unavailable are the

Basic tab default parameters.

Conflg Setting Slice Plane -- -:l

D 2o13o D Sequence D Echo Time Mode D ShimMode D Oblique

FOV TR TE FA

D IR Pulse Thickness Interval Multi slice

D Multi Echo D Multi Acquisition D Mode D Stacks

Freq# Phase#

OK

..,

Figure 6-4. The Config Setting window.

3. C lick to select each parameter check box that you would like to add to the

Basic tab.

4. C lick OK to add the parameter(s) to the Basic tab and close the Config

Setting window.

To remove a parameter from the Basic tab, follow these steps:

I. C lick the All tab and drag the scroll box to the bottom of the scrol l bar to

reveal the Config button.

2. Click d1e Config button. The Config Setting window opens.

3. Click to clear each parameter check box you wish to remove. The check

mark will be removed and the parameter will not be displayed on the Basic

tab.

4. Click OK to remove the parameter(s) from the Basic tab and close the

Config Setting window.

6·5

0AS Is~ MRI System Reference Manual T'MhtJent MqHt

6-6

All Tab

The All tab, pa1tially shown in figure 6-5, displays all of the scan parameters

including the defaul.t parameters. Because there are so many sca11 parameters,

not all of them can be displayed at once in this sma ll space. Use the scroll bar to

locate the desired set of parameters, or c lick the Overview button (figure 6-5) to

open the ScanParameterList window, which is shown in figure 6-7 and

described in the next section.

Sl1ce Plane

20/30

Sequence

EchoT1me Mode ShortiET

Sh1m Mode ( off - ( Limited

.Parameter

IR Pulse

Thickness

Interval

lv1ultr shce

Figure 6-5. The All tab.


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Scan Parameters 0 Scan Parameters Area Buttons

The top of the Scan Parameters area (figure 6-6) contains the following buttons:

Reset

Figure 6-6. The buttons at the top of the Scan Parameters area.

Reset- Resets al l changed parameters to the previously-saved default values.

Overview - Opens the ScanParameterList window, as shown in figure 6-7.

All of the various parameters found under the All tab can be viewed and

changed in this convenient window, rather than scrolling through the categories

in the Scan Parameter· area. Scanning can also be started and scan time can be

mon itored in this window.

Figure 6-7. The ScanParameterList window.

Dy namic scan time table- Opens the Dynamic scan time table window,

which provides a visual display of the execution plan for dynamic scans.

The buttons at the bottom of the Scan Parameters area are used during scanning

and are described in the "START, STOP, and Other Buttons" section in Chapter

5, " Exam Window Scanning Functions."

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0AS Is~ MRI System Reference Manual TIN hUM llb,pet

Note: Refer to the "Launcher Buttons" section of Chapter 3, ''System Overview, " for a detailed description of menu customization for Launcher too/bar buttons.

Changing the Scan Parameters Area Display Location

The Scan Parameters area can be displayed on the right or left side of the Exam

window. To change the display location, use the following procedure:

I. On the System Settings Launcher button menu, click Window Setting (this

command appears if the System Settings Launcher button menu has been

customized). The Window Setting window opens as shown in figure 6-8.

2. Click the Exam Window tab on the Window Setting window.

3. Click the desired graphical representation for the Scan Parameters area

location. Additionally, the Protocol Properties area can be displayed either

graphically or by task name from this tab as well (figures 6-8 and 6-9).

4. Click OK to save your choices and close the Window Setting window. The

changes made take effect when the next Exam window is opened.

Figure 6-8. The Scan Parameters area on left of Exam window, graphical display of task list (Protocol Properties area) selected.

6-8 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

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Scan Parameters 0

Figure 6-9. The Scan Parameters area on right of Exam window, task name display of task list {Protocol Properties area) selected.

Scan Parameters Descriptions

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The scan parameters are separated into the following sets of related parameters:

Sequence- ! ncludes parameters related to the scan to be performed, such as

slice plane, sequence type, and acquis ition mode.

Seq . Parameter- Includes parameters re lated to pulse sequences (TR, TE, and

NSA) and slices (thickness, interval, and number).

Advanced - Includes parameters related to add itional functions, such as phase

direction, presaturation, and bandwidth.

RADAR (RADial Acquisition Regime)- Includes parameters related to the

sampling of K-space in a radial pattern.

Saturation- Includes parameters related to the suppression of specific s ignals,

such as fat, water, and silicone.

6·9


Definition: 30 MRA refers to threedimensional magnetic resonance angiography. A slab refers to a collection of slices to be excited with a single excitation pulse, used in 30 acquisitions.

6. 10

T2WPrep (optionai)-A prepulse that enhances the T2 contrast of the imaging

target. When T2WPrep is appl ied to the BASG sequence, tissue contrast

improves but the SNR drops slightly.

MTC (Magnetization Transfer Contrast) - Includes parameters used to change

the contrast of images by moving magnetization from bound protons to free

protons.

VENC (Velocity ENCoding) - Includes parameters related to the use of phase

information to determine the rate and direction of blood flow.

SSP (Sloped Slab Profile) - lncludes parameters related to a sloped slab used to

suppress blood flow saturation in 3D MRA.

MPG (Motion Probing Gradient)- lnc ludes parameters related to scann ing

with the application of a gradient magnetic field to emphasize proton diffusion.

This is used with Diffusion Weighted Imaging (DWI).

Scan Control- Includes parameters related to the tim ing of contrast-enhanced

scans in various scan modes, such as wait t imes, delays, and contrast agents.

RAPID (Rapid Acquisition through a Parallel Imaging Design)- Includes

parameters related to the reduction of phase encode steps, which reduces scan

time.

Gating- Includes parameters used with ECG-, pulse-, and respiratory-gated

scans.

NAVI (NAVIgator Echo) - lncludes parameters related to Nav igator

acquisitions, which are used to reduce a1tifacts produced in a scan region, such

as the heart, where breathing can change the scan position.

PAPE (PA1tial Phase Encode)- Includes parameters related to PAPE, which

improves temporal resolution whi le maintaining image spatial resolution.

F ilter/PostProcessing-Includes parameters related to improving an image's

visual characteristics, as well as other post-processing selections.

Positioning- Includes parameters related to scan position, such as slice order

and plane order.

Others - Includes parameters fo r receiver coils and morning QA functions.

You can change parameter values by selecting from a list of options or by

clicking the up or down arrows (to change a numerical value in a box). You can

also change numerical values by highlighting the value in the box, typing the

new value, and then pressing the ENTER key. Parameters that have a grayed

out appearance are unavailable; th is occurrence depends on the combination

of parameters that have been selected. The Reset button at the top of the Scan

Parameters area resets all parameters to their previously saved default values.

The parameters are described in the remainder of this chapter.


Note: The values that can be set may be limited by the Sequence that is selected and related scan parameters.

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Scan Parameters 0 Sequence

The Sequence section of the ScanParameterList window (figure 6-1 0) contains

the fo llowing parameters:

Figure 6-10. The Sequence section of the ScanParameterList window.

Slice Plane - Provides the following options for the plane of the slices, as

shown in figure 6-11:

• AX- Axial

• SAG - Sagittal

• COR-Coronal

• SA-Sagittal and axial

• CA- Coronal and axial

• SC-Sagittal and coronal

• SCA- Sagittal, coronal, and axial

Figure 6-11 . Slice Plane options.

20 /30 - Provides the following options for the acquisition mode, as shown in

figure 6-12:

• I D - One-dimensional acqu isition. Used only in spectroscopy (lD is

automatically selected when Sequence is MRSSE).

• 2 0 - Two-dimensional acquisition. One slice is acquired per TR.

• 3D- Three-dimensional acquisition. ln 3D acquisitions, data encoded with

s lice pos ition information is collected, in addition to phase encoding and

frequency encoding. Multiple slices of image data are reconstructed us ing the

3D Fourier conversion. 30 acquisitions can produce images with varying s lice

thicknesses.

Figure 6-12. Acquisition mode options.

6. 11

0AS Is~ MRI System Reference Manual ThehtlentMqiMt

Note: With 30 measurements, the SNR of images is lower at the top and bottom of each slab compared to the center area, making the images susceptible to artifact when using the BASG sequence. Therefore, position the region of interest so that it comes to the center of the slab and set the number of slice encode a little higher.

Note: If homogeneity of the magnetic field is poor, BASG is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. To minimize this effect, be sure to carry out volume shimming before performing the BASG scan.

Note: Slice scan, slab scan, and pre-saturation pulses should be positioned to maximize the TOF effect when scanning with TOF MRA.

Note: If the blood currents often run parallel to scanned slice or slab, if they wind drastically, or if their transit paths substantially differ between the right and left vessels, the MRA image should be carefully interpreted.

Note: Check original images concurrently while interpreting TOFMRA.

6. 12

Sequence-Provides the following options for pulse sequence, as shown in

figure 6-13:

SE (Spin Echo)-Produces images with

proton density, T I, and/or T2 weighting.

• IR (I nversion Recovery) - Uses a 180° inverting radio

frequency (Rf) pulse prior to the 90° excitation pulse to

acquire images with specific suppression.

• GE (Gradient Echo) - Uses a variable flip angle to

acqu ire images with Tl or T2* contrast. The contrast

weighting is primari ly determined by the flip angle .

SE

SE IR GE SARGE RSSG TRSG BASG uTE FSE FIR pnmeFSE pnmeFIR TOF PC SEEPI GEEPI OW EPI RSSGEPI Shim S-Map MRSSE

• SARGE (Steady State Acquisition with Rewound

Gradient Echo) - Uses closely-spaced RF

excitation pulses and short TR (repetition time)

to create a steady-state signal. This sequence

produces images with T I and T2 weighting. Figure 6-13. Pulse Sequence

options.

• RSSG (RF Spoiled SARGE)- Uses closely

spaced RF excitation pulses with variable phase shifts. This sequence

produces images with Tl weighting.

• TRSG (Time Reversed SARGE)- Acquires the signal that was excited by the

prior RF pulse. This sequence produces images with heavy T2 weighting.

• BASG (Balanced SARGE)- Uses a short TR and acquires the signal under a

steady state, with slice-, phase-, and frequency-rewinder pulses. Th is sequence

produces images with high signal-to-noise ratio (SNR), mixed TI /T2 contrast,

and bright fluid.

• FSE (Fast Spin Echo) - Uses multiple 180° RF pulses to more rapidly

produce images with proton density, T l , and/or T2 weighting.

• FIR (Fast Inversion Recovery)- Uses a 180° inverting RF pu lse prior· to the

90° excitation pulse to acquire images with specific tissue suppressions.

• primeFSE- Similar to FSE, except that the user can enter TE and bandwidth

values, rather than values for the Inter E.Time (echo interval) and Echo Shift

parameters (these parameters are described later in this chapter).

• primeFIR-Similar to FlR, except that the user can enter TE and bandwidth

values, rather than Inter E. Time and Echo Shift parameter values.

• TOF (Time of Flight)- Used to produce MRA using flow/ inflow results of

blood.

• PC (Phase Contrast)-Optional. Produces MR ru1giographs using phase

information of blood flow.


Note: Image quality with EPI depends largely on the homogeneity of magnetic field. Volume shimming is required before running SE EPI to achieve good image quality.

Note: In the 5-Map sequence, scanning is carried out with the coil used for the mam scan and the TR body coil.

The 5-Map sequence is sensitive to patient movement. Keep the patient as still as possible while S-Map scanning to avoid artifact.

When scanning the abdominal region, breath holds are required in an 5-Map sequence when Mode is Nanna/.

When Wait mode is ON, the system pauses twice: after the prescan and in the middle of the 5-Map sequence.

Tic wide area is to be scanned using the TR body coil. The scanogram should be used with the coil for the main scan. Therefore, make sure that the area which is not scanned through the scanogram does not cause artifact.

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Scan Parameters 0 • SE EPI (Spin Echo using Echo Planar Imag ing)- Produces images with T l

o r T2 weighting using very sh011 acquis ition t imes.

• GE EPI (Gradient Echo using EPI) - Produces images with T2* weighting

using very short acquisition times.

• OW EPI (Diffusion Weighted EPI)- Produces diffusion-weighted images,

which depict the restriction of water molecule diffusion.

• RSSG EPI (RF Spoiled SARGE using EPI)- Optional. Produces images with

Tl weighting using short acquisition times.

• Shim (Shimming)- Performs highly-precise corrections of the static

magnetic field.

• S-Map (Sens itivity Map)- A sequence dedicated to 30 sensitivity map

acquisition. Acquires 30 sensitivity data to be used for shading correction

and RAPID measurement. In this sequence, images (acquired data) are not

displayed.

• MRSSE (MR Spectroscopy using Spin Echo) - Optional. Acquires molecular

dens ities of metaboliz ing substances in the human body.

EchoT ime Mode- Sets the range for the echo time (figure 6-14).

When Sequence is SE, choose one of the following:

• Normal-Use fo r normal scanning.

• Short T E- Use to acquire images with shorter T E than the Normal setting;

however, some parameters such as Dual Slice and Multi Echo will be

restricted.

When Sequence is FSE, FIR, primeFSE, or primeFIR, choose one of the

fol lowing:

• Short! ET- Use to acquire images with short Inter E. Times, such as 12 and

below. In figure 6- 14, Short I ET is selected.

• Longi ET - Use to acquire this s lice images with Inter E.Times of 12 and

above. This selection is used in FIR imaging.

• Optimized- Use to acquire the higher SNR and less aliasing image with

same Inter E.Time as ShortiET. Optimized is avai lable for 3D acquisition

only.

Figure 6-14. The Echo Time Mode scan parameter.

6. 13

0AS Is· MRI System Reference Manual n. htJ•t llqJMt

Note: When scanning a patient with an orientation other than feet first supine, the output image has it's orientation rotated, but shimming is not affected.

Note: When scanning with the patient oriented feet first, the output images are in the reverse order of the slice order being set, but shimming is not affected.

6- 14

Mode-Selects the sequence mode.

• Normal - Normal measurement is performed.

• YASC-ASL (optionai) -Creates an image of fluids, such as labeled blood

flow, using a spatial selection lR pulse. When VASC-ASL is selected, IR P ulse is displayed and set to Selective.

• GElR- Performs segment measurement using an IR pulse as a prepulse.

When GEIR is selected, IR Pulse is displayed and set to Segmented. As a

segment becomes larger, contrast may be slightly blurred.

• TIGRE-Performs a high-speed Tl contrast measurement in combination

with a fat suppression pulse for frequency selection. When TIGRE is

selected, Saturation is displayed and set to Segment FS.

• Nest- Collects signals using the receiver coi l and Transmit/Receive Body

coil at nearly the same time during the S-Map sequence. A sensitivity map

not easily affected by movement can be created for regions where movement,

such as breathing, is monitored.

Shim Mode- Provides options for the use of shimming results (figure 6- 15).

• off- Does not use shimming results.

• Volume-Uses volume shimming results. Shimming results are not used

when there are changes in a patient or coils.

• Auto Volume- When measurement conditions include shim measurements,

shimming is automatically performed during prescanning.

• Regional- Performs regional shimming in a specific area designated by the

purple box on the positioning screen. Upon opening a scan task, the regional

sh im box moves along with any movement of the slice group. However, once

the regional shim box is activated, the slice group and regional shim no longer

move together.

A Caution

off Volume AutoVolume ReQ•onal

Figure 6-15. Shim Mode options.

If an error occurs during shimming, contact Hitachi service.

Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Q54-53287v4

Scan Parameters 0 Additional Notes fo r t be Mode parameter:

The values that can be set may be limited by the selected Sequence and related

scan parameters.

Since GEIR is 3D measurement, the SN R of images is lower at the top and

bottom of each slab compared to the center area. Therefore, position the region

of interest so that it comes to the center of the slab and set the number of slice

encode a little higher.

Pre-saturation pulses may be used with the 30 GEm sequence, however MTC

and FatSat pulses canno t be used.

Additional Notes fo r tbe Sbim Mode parameter:

Estimated fie ld distributions are displayed after volume shimming, however they

are not displayed after regional shimming.

The volume of interest (VOl) must be within the region of volume shimming.

The results of shimming are canceled and become ineffective when the patient

name or receiver coi I is changed, when Shim Mode is off and any measurement

is carried out, or when Prescan is O N and any measurement is carried out.

When Shim Mode is set to anything other than Regional, the VOl is deleted.

The region of shimming, region of imaging, and the direction of phase encoding

shou ld be identical.

The center of shimming should be identical with the center ofthe magnetic field.

Additional Notes for the S-Map pa rameter :

The posit ion and the scan parameters should be set in a way that prevents

aliasing artifact from occun·ing in the area selected fo r the main scan.

Planes to be scanned will vary depending on d1e anatomical region being

scanned. Therefore to avo id a liasing artifact, COR and SAG planes are

recommended because the direction of the body axis is the readout direction.

When setting FOY, it is recommended to set it 20 to 30 percent larger than the

one for the main scan.

S lab thickness should be set according to the size of the region to be scanned,

adjusting S. Encoding.

SNR can be too low when FOV is small. Therefore, it is necessary to ensure

adequate SNR by setting the appropriate NSA.

6. 15


Note: If performing a Black Blood scan with Multi Slice and Multi Acquisition= 1, adjacent slices are excited in 1 TR, so image quality can be degraded. Perform scans with the slice interval larger than the slice thickness of the Double IR Pulse and STIR Pulse or with Mufti Acquisition ;:: 2.

Note: The values that can be set may be limited by the selected Sequence and related scan parameters.

6. 16

Oblique-Provides methods for determining whether or not scans can be

performed, based on the angulation of slices. Options are (figure 6-16):

• Full -Allows ful l angulation of sl ices, but will require protocol changes if a

steep angle is used.

• Limited- Allows a limited degree of angulation, so that the protocol

paTameters selected for the acquisition can be used.

Seq. Parameter

P!ii limtted Full Limited

Figure 6-16. Oblique methods.

The Seq. Parameter section of the ScanParameterList window (figure 6-17)

contains the following parameters:

Figure 6-17. The Seq. Parameter section of the ScanParameterList window.

FOV- Indicates the size in millimeters ofthe visual fie ld to be reconstructed

fol lowing the scan.

FOV2-Sets the size (in millimeters) of the longitudinal visual field

reconstructed following the scan. The crosswise visual fie ld is set by the FOV

parameter. Used only in spectroscopy (FOV2 is displayed when Sequence is

MRSSE).

TR- Indicates the repetition time in milliseconds of the pulse sequence. During

gated scans, TR values a re automatically set when Trigger is selected for the

Gate or Resp mode.


Note: T£2. TE3. and TE4 are used only tor multiple echoes.

Note: Additional/A pulse options (Double, Triple) are associated with the CardioSuite, which is a purchasable option.

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Scan Parameters 0 TE- Indicates the echo period in milliseconds for the first echo. This value is

automatically set when the following are selected from the Sequence list:

• BASG

• FSE

• FIR

• Shim

TE2- Indicates the echo period for the second echo. This setting is displayed

when the selected Sequence is SE, GE, SARGE, RSSG, or FSE, and the

Multi Echo parameter is set to 2 or more. (When FSE is selected, TE2 is

automatically set based on other parameters, such as E.Factor.)

TE3- Indicates the echo time for the th ird echo. This setting is displayed when

the selected Sequence is SE and d1e Multi Echo parameter is set to 3 or more.

TE4- Indicates the echo time for the fourth echo. This setting is displayed

when the selected Sequence is SE and the Multi Echo parameter is set to 4 or

more.

Figure 6-18 shows settings for the TE through TE4 parameters.

~-i . j .. l

Figure 6·18. Example settings for TE, TE2, TE3, and TE4 boxes.

FA (Flip Angle)- The angle of excitation to which the net magnetization is

tipped relative to the main magnetic field.

IR Pulse (Inversion Recovery Pulse)- Indicates if an IR pu lse will be used for

tissue saturation. This is primarily used with Cardiac scanning.

This parameter can be selected when Sequence is SE, BASG, FSE, DW EPI,

SE EPI, or GE EPl.

The following options are available, as shown in figure 6-19:

• Off- Does not perform tissue saturation; this is the recommended setting.

• Single- Perfonns tissue saturation with des ignated T l.

• Double- Executes blood saturation via Double-IR. When Double is selected,

Tl becomes available.

• Triple (optional) - Executes fat saturation via STIR pulse and blood

saturation via Double-JR. When Triple is selected, T l and Tl2 become

available.

6·17


Note: Tl and FatSat cannot be combined simultaneously in the STIR type fat suppression.

Note: Optimum T1 of the Black Blood scan varies depending on orientation of the slice plane. When reduction of blood signal is small, modify T1 and retry the scan.

Note: For a FLAIR sequence of the brain, theIR Thk.Ratio should be set to 4.0.

6. 18

• Segmented-Performs segment measurement using the STIR pulse as a

fat suppression prepulse. Segmented is selectable with 3D RSSG (GEIR

imagi11g). When Segmented is selected, TI ru1d Segment become available.

• Se lective-Applies a spatial selection IR pulse. Selective is selectable with

VASC-ASL imaging. When Selective is selected, TI and Segment become

available.

Figure 6-19. Example IR Pulse options.

TI- Sets the Inversion Time, which is the time period between the initial 180° inversion pulse and the 90° excitation pulse in an IR pulse sequence. This box

is available when the selected Sequence is IR or FIR, the ECG Gate Mode is

Delayed or MyoPer, or when IR Pulse is Single. The measurement of the Tl

will be calcu lated as follows:

• W11en Sequence is IR or FIR, or IR P ulse is Single, Tl is the interval

between the STIR pulse and the excitation pulse.

• When Gate Mode is Delayed or MyoPer , Tl is the interval between the STIR

pulse and the zero encode excitation pulse.

• When IR P ulse is Double or Triple, TI is the interval between the Double-IR

pulse and the excitation pulse.

• When IR Pulse is Segmented or Selective, TI is the elapsed time from the

STIR pulse to the zero encoded excitation pulse.

TI2 - Sets the interval (in milliseconds) from the STIR pu lse to the excitation

pulse. Specify a TI2 setting when IR Pulse is Triple.

Segm ent-Sets the number of echoes to be acqu ired after appli cation of one

STIR pulse. Specify a Segment setting when IR Pulse is Triple.

IRFA-Sets the excitation angle (i111 degrees) ofthe IR Pulse spin. Specify an

IRFA setting when Gate Mode is MyoPer.

IR T hk.Ra1io- lndicates the slice thickness selection ofthe in itial 180° pulse

relative to the s lice th ickness of the main scan. The normal setting for this

paramet·er is 1.3. You can use th is pa:rameter when Sequence is FIR or Prime

FIR, or when Sequence is FSE or Prime FSE; and IR Pulse is Single. In figure

6-20, the Sequence is FIR and theIR Thk.Ratio is set to a value of 1.3.


Note: The gap between slices can be calculated as. Interval- Thickness = Gap

Q54-53287v4

Scan Parameters 0

Figure 6-20. /R Thk.Ratio example.

BBIR Thk.Ratio - Sets the s lice thickness ratio of the Double-IR Pulse for the

main scan sl ice thickness. Specify a BBJR Tbk.Ratio when Sequence is FSE

or primeFSE and IR Pulse is Double or Triple.

Thickness - Indicates the slice thickness (in millimeters).

Inten ral - lndicates the spacing (in mil limeters) between slices, measured

from the center of one s lice to the center of the next sl ice. The interval in 20

multi-slice acquisitions is between parallel slices; the interval in 3D multi-slab

acqu is itions is betv.-een parallel slabs.

Multi slice- Indicates the number of slices to be acquired during one scan.

Th is setting is displayed for 20 acquisitions on ly.

Multi Echo- Indicates the number of echoes to be collected in one scan. As

the Multi Echo value is increased, additional numbered TE boxes (TE2, TE3,

and so on) become available on the ScanParametcrList window. M ulti Echo is

available when Sequence is SE, FSE, GE, SARGE, or RSSG. In figure 6-21 ,

Sequence is GE and Multi Echo is set to a value of2.

Figure 6-21. Multi Echo example.

6. 19


6 • .20

Multi slab- Available for 3D acquisitions only. Indicates the number of slice

slabs to be acqu ired in one scan. In figure 6-22, Sequence is TOF and Multi

slab is set to a va lue of 4.

Figure 6-22. Multi slab example.

Recon P itch - A llows the desired thickness of the reconstructed slices to be

input. Recon P itch can be a value no less than one-half of the acquired slice

thickness (the Thickness parameter).

Recon Pitch will automatically adjust to maintain the ratio between T hickness

and Recon Pitch values. Additionally, Recon Pitch automatically reverts to

upper and lower lim its when an entered value exceeds e ither limit (the upper

limit is Thickness, and the lower limit is one-half of Thickness).

Recon Slice- The number of slices to be reconstructed for the acquisition.

Slice Reject[% ]- lndicates a percentage of sl ices at the slab ends that wi ll not

be reconstructed. This is useful for 3D acquisitions that may have decreased

SNR at the slab ends. One half of the value that is selected is rejected fi·om each

end of the slab (for example, if20 percent is selected, 10 percent of the total slab

will be rejected from each end).

Overlap[% J- Indicates a percentage amount of slab overlap, which is used

to improve the signal continuity between s lab intervals in 3D TOF multi-slab

acquisitions. The Multi slab parameter must have a value greater than I.


Q54-53287v4

Scan Parameters 0 Figure 6-23 shows the Slice#, Slice Reject [%], and Overlap[% ] parameters set

for a 3D TOF series.

Figure 6-23. Slice#, Slice Reject[%], and Overlap[%] example.

Multi Acquisition- Indicates the number of acquis itions. This setting is

available when the Mode parameter is Interleaved or Sequentia l.

When Mode is Stack, the value in M ulti Acquisition is unavailable, but wi ll be

the same as the value set in the Stacks box, as shown in figure 6-24.

"' • Figure 6-24. Multi Acquisition example.

When the M ode parameter is SingleSiice, M ulti Acquisition is unavai lable.

However, the displayed number of acquisitions will be the same as the number

set in M ulti slice for 2D acquisitions, or the number set in Multi slab for 3D

acquisitions, as shown in figure 6-25.

Multi slice

-~ l@ft#iiijli!Fii* 5

Multi slab

Figure 6-25. SingleS/ice Mode examples for 20 and 30 acquisitions.

The following examples explain how the M ulti Acquisition, Mode, and

Multi slice parameters can be set in various combinations to acquire images

differently.

Example 1: M ulti slice is 6, Mode is Interleaved, and M ulti Acquis ition is 2.

The value of2 in the Multi Acquis ition box divides the slices into two groups

of three s lices each. The Interleaved mode acquires the top and bottom s lices,

then the middle slice in each group, all with the same TR. For these parameter

settings, the first acquisition would be slices I and 3, and then slice 2; the second

acquis ition would be slices 4 and 6, and then slice 5.

6. 21


6 . .2.2

Example 2: M ulti Slice is 6, Mode is Sequential, and M ulti Acquisition is 2.

The value of2 in the M ulti Acquisition box divides the sl ices into two groups

of three slices each. The Sequential mode acqu ires the slices in numerical order,

one group at a time, all with the same TR. For these parameter settings, the first

acquisition would be slices I, 2, and 3; the second acquisition wou ld be slices 4,

5, and 6.

Example 3: M ulti Slice is 6, Stacks is 2, and Mode is Stack.

Stack mode can be used when slices are set at different angles, such as in axial

lumbar imaging. Stack mode acquires the slices in the first stack, then the slices

in the second stack, all with the same TR. For these parameter settings, the

setting of the Stacks value at 2 with Mode set to Stack causes the M ulti Slice

box to be updated and disp lay a total of 12 slices (6 slices x 2 stacks= 12 total

slices).

Example 4: M ulti Slice is 6 and Mode is SingleSlice.

SingleSiice mode is used to acquire one slice per TR, as in 20 TOF sequences.

For these parameter settings, each slice (of the 6 total slices) will be acquired

individually.

Mode-Specifies the acquisition mode. The options, as shown in figure 6-26,

are:

• Interleaved -Slices are acquired in an odd- and even-numbered fashion (such

as slice numbers 1, 3, 5, 7, then slice numbers 2, 4, 6, 8).

• Sequentia l-Slices are acquired in order of sl ice number (such as 1, 2, 3, 4).

• Stack-Slices are acquired for each angle.

• SingleSlice-Each slice is acquired as a separate acquisition, with the

selected parameters (one slice per TR).

"!¥'

Figure 6-26. Mode options.


Q54-53287v4

Scan Parameters 0 Slice#- Indicates the number of slices to be reconstructed for 3D acquisitions

(figure 6-27).

Figure 6-27. Slice# example.

Stacks- Indicates the number of groups when acqu iring multiple groups with

different angles.

Freq#- lndicates rhe number of sampl ing steps in the frequency axis, as shown

in figure 6-28. Hold the mouse pointer over the Freq# box to view the range that

is available.

IM §s6 ::J .. ' ..

Figure 6-28. The Freq# parameter.

Phase# - Indicates the number of sampling steps in the phase axis, as shown in

figure 6-29. Hold the mouse pointer over the P hase# box to view the range that

is available.

Figure 6-29. The Phase# parameter.

Freq Point- Sets the frequency resolution. Used only in spectroscopy (Freq

Point is displayed when Sequence is MRSSE).

ReconMatrix - lndicates the reconstruction matrix for the image. A value

larger than the frequency encoding value (from the Freq# box) and/or the

phase encoding value (from the Phase# box) can be set. Figure 6-30 shows

ReconMatrix options.

'*'""" "-=5:..;.;12=-------f 128 256 512 1024 2048

Figure 6-30. ReconMatrix options.

6· 23


Note: A value must be entered in the APR[%} box to make Half Scan available.

NSA (Number of Signals Averaged)- Indicates the number of s ignal

acquisitions to be averaged. Increasing NSA will improve the SNR ofthe image,

but also increases scan time. Doubling NSA doubles the scan time, but only

increases the SNR by approximate ly 40% because increased noise accompanies

the increased number of signals.

APR[%] (Asymmetric Projection Rate)- lndicates a percentage ofK-space

that w ill not be acquired in the phase encoding d irection. K-space as a whole is

I 00%; the APR[%J parameter can be set to values between 0% and 45% and

can be changed by 5% intervals. This parameter is used in conjunction w ith

Half Scan.

The position of the non acquired K-space region changes for each of the echo

layouts, as shown in figure 6-31. In addition, processing of the non acquired

region c hanges according to the setting of the Half Scan parameter (described

next in this section).

Frequency Frequency Frequency Frequency

PhaseW 4 PhaseW 1 PhaseF 1 Phase~ 5

6-24

3 2 2 4 2 3 3 3 1 4 2 1 4 1

APR APR APR APR

Centnc Ant1 Centnc Sequential ADA

Slice

Phaser, APR

Slice

Phaser, 1 3 2

1 3 2 4 6 5

4 6 5 7 9 8

8 7 9 11 10 12

11 10 12 APR

PEAKS RPEAKS

Figure 6·31. K-space filling for various echo layouts.

Half Scan -Enables image acquisition in a sha tter time by limiting the

sampling of the phase axis inK-space. Spatial resolution is maintained, but

SNR is reduced. Images are created using the acquired data, combined with the

interpo lated data used to fi II the non acquired region of K-space. Acquisitions

are performed in accordance with the val ues set for the phase direction in the

APR[%] parameter. The options, as shown in figure 6-32, are:


Note: OW/ is sensitive to movement smce the MPG pulse is applied. In multi-shot measurements, use gated scanning with the scan region immobilized to reduce motion artifacts.

Q54-53287v4

Scan Parameters 0 • off-Does not use Half Scan.

• ON-Uses Half Scan.

"'""' off ·~ off ON

Figure 6-32. K-space filling for various echo layouts.

The following examples explain how the APR(%} and Half Scan parameters

function together:

Example 1: APR(%] set at 25 percent and Half Scan is ON (figure 6-33)

This is the equivalent of~ Scan. Data is acquired from three-foUJths (~)or 75% of K-space; one-foUJth ('.!.!)or 25% of K-space is interpolated.

:1*'1'111[5 :J .. €MIA*'' ( ON ·I

Figure 6-33. The equivalent of three-quarter scan.

Example 2: APR(%] set at 45 percent and Half Scan is ON (figure 6-34)

This is the equivalent of 1/ 2 Scan. Data is acquired from 55% of K-space; 45% of

K-space is interpolated.

1'1''1'1111~~45=-~~---IMIP*ii I ON • )

Figure 6-34. The equivalent of one-half scan.

Shot Num.- Indicates the number of RF excitations, or TR periods, needed to

acquire data, as shown in figure 6-35. A lower shot number results in a faster

scan time. The shot number can be calculated using the fo llowing equation:

Phase# "'" E. Factor = Shot Num.

Figure 6-35. Shot Num. example.

Shot Num. is available when Sequence is SE EPl, DW EPL or GE EPI. Hold

the mouse pointer over the Shot Num. list to display the range of settings.

6· 25


Note: When Echo A/foe. is Centric and if# RF Prep is extremely small, good images cannot be obtained since data acquisition starts while steady state has not yet been reached.

6 • .26

Shot Num. is displayed, but unavai lable, in the following cases:

• Sequence is FSE, FIR, RSSG or EPI.

• Sequence is Prime FSE or Prime FIR, and Echo Alloc. is Centric.

E.Factor - The number of echoes to be used to create a s ingle image. An

acceleration rate is obtained based on the number of echoes used. However, the more the echo is delayed, the weaker the signa l strength becomes due to the decay of signal amplitude (T2 or T2*). As the E.Factor increases, the SNR and

resolution decrease.

E.Factor is avai lable when Sequence is FSE, FIR, or RSSG EPJ.

E.Factor is displayed but unavailable in the following cases:

• Sequence is SE EPI, DW EPI, or GE EPI.

OR

• Sequence is P rime FSE or Prime FIR, and Echo Alloc. is ADA.

Inter E. Time- The time between echoes. Inter E.Time is displayed when

Sequence is any of the following: FSE, FIR, SE EPI, DW EPI, GE EPI, or RSSG EPI. When Sequence is FSE or FIR, an effective TE is calcu lated by the system. This TE calculation inc ludes the E.Factor, Echo Alloc., Echo Shift, and Inter E. Time parameters to determine image weighting.

Echo Shift-Adjusts image contrast by changing the location of the effective TE in K-space, without changing the number of echoes. An Echo Shift of 1

changes the effective TE by an increment equa l to the value displayed in Inter E. Time. Echo Shift is available when Sequence is FSE, FIR, SE EPI, GE EPI, RSSG EPI, or DW EPI. Echo Shift is displayed but unavailable when

Sequence is Prime FSE or Prime FIR.

Echo Shift2 - AIIows Echo Shift to be selected for the second echo. Echo Shift2 is available when Sequence is Prime FSE or Prime FIR.

Echo Alloc. - AIIows the echo layout method to be selected. A pa11ial listing of options is shown in figure 6-36.

The options are:

• Sequential

• Centric

• AntiCentric

Centric Ant1Centnc

Figure 6-36. Echo A/foe. options.


Q54-53287v4

Scan Parameters 0 • ADA (Asymmetric Data Allocation)

• PEAKS (optional)

• RPEAKS (optional)

• TPEAKS (optional)

• Seq-Seq (optional)

• Cent-Cent (optional)

• Cent-Seq (optional)

Sequence determines which Echo Alloc. options are available. Sequential, Centric, AntiCentric, and ADA are frequency/phase 2D echo layouts (figure

6-37).

The non acqu ired reg ion will be determined in combination with the value set in

the APR[% 1 parameter. Processing of the non acquired region will change

according to the Half Scan paramete r value. For example, Half Scan is

automatically set when ADA is selected.

Frequency

PhasefC 4

Frequency

PhaseW 1

Frequency

Phase.fe 1

Frequency

PhaseW 8 3 2 2 7 2 3 3 6 1 4 4 5 1 4 5 4 2 3 6 3 3 2 7 2 4 1 8 1

Centnc Ant1 Centnc Sequential ADA

Figure 6-37. Frequency/phase 20 echo layouts.

PEAKS and RPEAKS are optional phase/s lice 2D echo layouts (figure 6-38),

wh ich are used during 30 contrast-enhanced MRA. Acquisition is started

in the direction of the epicenter of K-space. When the epicenter is acquired,

acquisition is pe1formed receding from the epicenter. When the APR[%] parameter is 0, there is no difference between PEAKS and RPEAKS. However,

when the APR I% J parameter is set to anything above 0, the non acquisition

reg ion d iffers. Processing of the non acquired region changes according to the

Ha lf Scan parameter value.

6· 27


6 . .28

Slice

Phaser,

1

4

8

11

APR 3 2

6 5

7 9

10 12

PEAKS

Slice

Phaser, 1

4

7

11

3 2

6 5

9 8

10 12

APR

RPEAKS

Figure 6-38. PEAKS and RPEAKS optional phase/slice 20 echo layouts.

TPEAKS is an optional phase/slice 2D echo layout, which is used during 3D contrast-enhanced MRA in the same way as PEAKS and RPEAKS. The

distance between the center of the phase/slice plane and each acquisition point is

used as the standard to set the acquisition order. As shown in figure 6-39,

acquisition is performed from the center of the phase/slice plane, with the time

that K-space data collection begins as the peak of the contrast agent density.

Acquisition is then performed on the side closest to the center.

Slice

Phaser,--------------~

4

Figure 6-39. TPEAKS optional phase/slice 20 echo layout.

Seq-Seq is selectable on ly with 3D RSSG (GEJR imaging). The measurement

order of both phase encode and slice encode is Sequential. With Seq-Seq, temporal efficiency is better than Cent-Seq and Cent-Cent since data is

acquired before the Tl time.

Cent-Cent is used with 30 RSSG (GEIR) or TIGRE imaging. Echo allocation

for both the phase and slice encode directions is Centric. When using this echo

allocation, #RF Prep must be increased. However, increasing #RF Prep results

in the reduction of fat suppression by the FatSat pulse.


Q54-53287v4

Scan Parameters 0 Cent-Seq is an echo allocation option for TIGRE imaging. Echo allocation for

the phase encode direction is Centric, while the echo al location for the sl ice

encode direction is Sequentia l. Centric scans from the center of K-space toward

the peripheral region, while Sequential scans from the peripheral region toward

the center, sequentially.

Figure 6-40 illustrates the Seq-Seq, Cent-Cent, and Cent-Seq echo allocation

options.

I

I

1

2

3

4

5

Seq-Seq

Q) '0

8 c: w

~ t Q.

4 3

r---1 2

Slice Encode

I I

3 2

1

1 2

3

Cent-Seq

Q)

8 c: w

~ t Q.

l

-3 2

1

I

3 2

1

1

2

3

Cent-Cent

4

Slice Encode

---'1 1

2 3

Slice Encode

Figure 6-40. Seq-Seq, Cent-Cent, and Cent-Seq echo allocation options.

3D Acq. Mode-Selects the measurement field of the ky-kz plane (K-space), as

shown in figure 6-41.

II II II C1rcular · I Normal I C1rcular I ... ~

Figure 6-41. 3D Acq. Mode options.

6· 29


6-30

• Normal - Measures the rectangular field in the ky-kz plane (figure 6-42), when

Cent-Cent or Cent-Seq echo allocations are used with TIGRE.

-.ky Normal

Figure 6-42. Norma/3D Acq. Mode K-space measurement field concept.

• Circular - Measures the inscribed circle in the rectangular fie ld of the ky-kz

plane (figure 6-43), when the Sequence parameter is RSSG and the Mode

parameter is TIGRE.

kz

I __..v 1""---

I t'\

\. v .......

1""--- v /

-.ky Circular

Figure 6-43. Circular 3D Acq. Mode K-space measurement field concept.

Chemical Shift- Indicates the optimum polarity ofthe phase-encoding

grad ient magnetic field. The po larity can be changed to minimize the effects

of image distortion. C hemical Shift is available when Sequence is SE EPI,

GE EPI, DW EPI, or RSSG EPI, and Echo Alloc. is Sequentia l or ADA. As

shown in figure 6-44, the options are:

• Normal -Normal polarity of the phase encoding gradient magnetic field.

• Reverse- Reverse polarity of the phase encoding gradient magnetic field.

Normal

Normal Reverse

Figure 6-44. Chemical Shift options.


Note: The values that can be set may be limited by the selected Sequence and related scan parameters.

Q54-53287v4

Scan Parameters 0 DE Pulse (Driven Equi librium Pulse)-An additiona l pulse that can be used

fo llowing s ignal collection to possibly decrease TR and consequently decrease

scan time, while maintaining T2 contrast. A DE pulse converges the transverse

relaxation of the magnetization and forces it to longitudina l relaxation. DE

Pulse is available when Sequence is FSE, FIR, P rime FSE, or Prime FlR. The

following options are available, as shown in figure 6-45:

• off-Does not add the DE pulse.

• ON-Adds the DE pulse.

II++ off ~ I I off ON

Figure 6-45. DE Pulse options.

M ulti Voxei- Indicates the number ofvoxels acqui red in one scan. Used only

in spectroscopy (M ulti Voxel is displayed only when Sequence is MRSSE).

Advanced

The Advanced section of the ScanParameterList window (figure 6-46)

contains many additional parameters that can be used during image acquisitions.

Figure 6-46. The Advanced section of the ScanParameterLfst window.

P resat (Presaturation)-AIIows presaturation pulses to be applied that can

reduce artifacts by control ling the signals from movable areas (such as blood

flow signal or the abdominal wall).

Presaturation is a technique that uses repeated RF excitation of structures

adjacent to the anatomy of interest to reduce or e liminate the phase effect

artifacts that can be caused by flowing nuclei in these adjacent structures. The

signal from the flowing nuclei is saturated, and therefore llullified, upon entering

the FOV.

6. 31

0AS Is~ MRI System Reference Manual nt.hU•tMqJMt

Note: Refer to chapter 3-2 of the Oasis How-to Manual for complete presaturation pulse details.

6-32

You can set a maximum of eight presats, with the Presat box displaying the total

number. The first two presats are automatically set as parallel regions adjacent to

the sl ice surface. These two regions prevent the blood flow signal from flowing

into the slice plane to be scanned. Presats are displayed in blue. The mouse can

be used to rotate, move, or magnify the presat regions.

Normal - Applies presats for each slice acqu isition. Figure 6-46a shows a

normal presat.

Figure 6-46a. A Normal presat.


Q54-53287v4

Scan Parameters 0 Walking -Allows the position of the presat region to move, or "walk," for

each s lice acquired (or each slab in 30). In this manner, the presat always

remains adjacent to the slice. This is used when acquiring blood vessel images

in angiography.

Walking is available when Sequence is TOF or BASG. If a wa lking presat is

selected, it is the first presat d isplayed in the viewport, and it is d isplayed in

green. On ly one walking presat is avai lable. The mouse can be used to rotate,

move, or magnifY the walking presat region . The number displayed in the

P resat box is the total number of presats, including the walking presat. Figure

6-47 shows a walking presat.

Figure 6-47. A Walking presat.

Intermittent- Applies presats for each repetition time (which is the va lue set

in the TR parameter): normally, the presat is applied for each sl ice acquisition.

Intermittent presats will allow you to increase the number of slices; however as

the TR increases, the effectiveness of the presat decreases.

The max imum number of intermittent presats available is 2. The intermittent

presats will be displayed in light blue. The mouse can be used to rotate, move,

or magnify the intermittent presats. The number displayed in the P resat box is

the total number ofpresats, including the intennittent presats.

Figures 6-48 and 6-49 show the Inte rmittent parameter with values of I and 2

respectively.

6-33

0AS Is~ MRI System Reference Manual 11141 htlet~t olllqHt

6-34

Figure 6-48. Intermittent set to 1.

Figure 6-49. Intermittent set to 2.

Segment - May improve presat resu lts. Available when Sequence is BASG, and

one or more presats have been selected. Figure 6-50 shows Segment set to l.

Figure 6-50. The Segment parameter.


QS4-53287v4

Scan Parameters 0 Dual Slice-Acquires twice as many images with the same scan parameters

by acquiring two parallel slices at a time. The number that can be entered in the

M ulti slice box is doubled. An even number is required in the NSA parameter

box. Dual Slice is available when Sequence is SE, IR, or GE. The options for

Dual Slice, as shown in figure 6-51 , are:

• off-Does not use dual slice.

• ON -Uses dual s lice.

l'.i@II!EIIIII~Jo~ff------~·1 ~N I

Figure 6-51. Dual Slice options.

Rephase (Flow Compensation) - Used to suppress flow artifacts, such as blood

and CSF. The options, as shown in figu re 6-52, include:

• off-No rephase.

• Slice- Rephase is applied along the sl ice direction only.

• Freq- Rephase is applied along the frequency direction only.

• Slice_Freq- Rephase is applied along the slice and frequency directions.

off off Shce Freq Shce Freq

Figure 6-52. Rephase options.

The available Rephase options depend on the selected Sequence. For multi

echo acquisitions, the presence or absence of Rephase for each echo is as

follows:

Sequence 1 Echo 2 Echoes

SE No rephase Rephase

GE Rephase Rephase

SARG E Rephase Rephase

RSSG Rephase Rephase

FSE Rephase Rephase

primeFSE Rephase Rephase

6· 35

0AS/S~ MRI System Reference Manual n.ratJentlll.q:net

Note: As the frequency bandwidth of the reception signal is reduced, the SNR of the image increases. However, chemical shift artifacts (a phenomena where the difference in the resonance frequencies between water and fat diverge on the image) will become noticeable.

6-36

Bandwidth[kHz]-lndicates the frequency bandwidth (kHz) ofthe reception

signal, as shown in figure 6-53. Since noise is distributed evenly across a ll

frequency bandwidthsj reducing the frequency bandwidth value reduces noise

and improves the SNR; however, chemical shift artifacts may become more

noticeable.

Figure 6-53. The Bandwidth[kHz] parameter.

Bandwidth2[kHz]- Indicat es the frequency bandwidth (kHz) of the reception

signal for the second and subsequent echoes during a multi-echo acquisition.

This parameter is available when Sequenc~ is SE, GE, SARGE, or RSSG, and

Multi Echo (under Seq. Parameter) is 2 or more.

In figure 6-54, M ulti Echo is set to 2, and Bandwidth2[kHz] is set to I 0.

04 17 1 1m3 ..

Figure 6-54. A Bandwidth2[kHz] parameter example.


Note: The larger the AMI[%] value, the shorter the TE. However, if Half Echo is off, there may be a degradation of spatial resolution.

Note: Half Echo uses frequency direction data in the same manner that Half Scan uses phase direction data.

Q54-53287v4

Scan Parameters 0 AMII %1 (Asymmetric Measurement Imaging)- Indicates the percentage

(usually 20% to 30%) of the early portion of the echo signal that wi ll not be

measured, as there is more noise in the beginning of the echo signal (as shown

in figure 6-55). Asymmetric measurement imaging allows the user to shor1en the

TE and increase the number of slices, and may result in improved contrast on

T l-weighted images. However, if AMI[%) is set to 30% or higher without

setting Half Echo to ON, spatial resolution may be degraded (Half Echo is

described next in this section).

_j: 100% ~ ; Frequency ~ . ~ d

. t" GC Asymmetnc measurem nt rrec ron imaging (%)

L Echo signa1---_J

Figure 6-55. AMI[%] illustration.

Half Echo- Prevents degradation of spatial resolution during AMI[%].

Half Echo creates an image by estimating the uncollected data (based on the

collected data) in the frequency direction. It allows for the use of a shor1er TE,

or lower bandwidth. The options are:

• off- Does not use half echo.

• ON- Uses half echo.

Echo Type- Indicates the echo allocation method. and is fixed as Half.

Used only in spectroscopy (Half is automatical ly selected when Sequence is

MRSSE).

Rect.FOV (Rectangu lar Field ofView)- Reduces the number of acquisition

points in the phase direction (set in the Phase# parameter). R ect.FOV is used to

match the size of the phase encod ing direction for the scan target, as well as for

the FOV that has been set.

The scan time will be reduced by the amount that the va lue of P hase# is

reduced. Although dle spatia l resolution is the san1e as for a normal scan, the

SNR wi ll be reduced in accordance with the number of reductions in the phase

encoding d irection.

6·37


6-38

As shown in figure 6-56, the options inc lude:

• off- Does not use Rect.FOV.

• Auto-Acquires the size of the patient in the phase encoding direction, and

then automatically determines the fOY actually acquired and the number of

acquisition points in the phase direction.

• Manual- Allows the user to select the size of the rectangular FOV.

off Auto Manual

Figure 6-56. Rect.FOV options.

Size[%] - Available when Rect.FOV is Manual. Allows you to enter the size

of the rectangular FOV to be acquired; this value is displayed as a percentage of

the current FOV parameter (under Seq. Parameter). Figure 6-57 shows

Size[%] set to 80, meaning the FOY will be reduced by 20% in the phase

encoding direction.

Figure 6-57. Size[%] example.

Anti.aliasing- Removes a liasing artifacts that are produced when the patient

is larger than the FOY in the phase encoding direction. Anti-aliasing is also

effective in reducing motion artifacts in certain anatomic regions (such as the

chest or abdomen).

As shown in figure 6-58, the options include:

• off-Does not use anti-aliasing.

• Auto- Acquires the size of the patient in the phase encoding direction. The

FOV that is actua11y acquired and the number of acquisition points in the

phase direction are automatically determined based on the value of the Mode

parameter, which is described next in this section. The available Mode options

are Res and Time.

• Manual- Allows the FOV size to be entered in the Size[% ] box. The

available Mode options are Res, T ime, and TimeRes.

off

off Auto Manual

Figure 6-58. Anti.aliasing options.


Note: If# RF Prep is set to an extremely low value, data with large signal variations will be acquired. causing artifact.

054·53287v4

Scan Parameters 0 Mode-Specifies the manner in which anti-aliasing is perfonned: maintaining

spatial resolution, maintaining scan time, or both. The following options are

always available:

• Res- Spatial Resolution Mode. Increases the number of acquisition points

in the phase direction according to the value of the Size I% I parameter. The

spatial resolution is maintained, but the scan time increases based on the value

of the SizcJ% 1 parameter.

• Time-Scan Time Mode. Increases the acquisition FOV according to the

value ofthe Size[% ] parameter, but does not change the number of acquisition

points in the phase direction. The scan time is maintained, but the spatial

resolution decreases based on the value of the Size[%] parameter.

The following additiona l option is available when Aoti.aliasing is Manual:

• TimeRes-Scan Time/Spatial Resolution Mode. Doubles the number of

acq uisition points in the phase direction and reduces the effective NSA by

half. The NSA parameter must be set to an even number. The SNR, scan time,

and spatial resolution are all maintained.

Figure 6-59 shows the Mode options.

lilllll I Auto I .::11111111 I Manual ·I .

'' [Res · ] WI ~Res ·) Res I Res I Time T1me

TimeRes

(a) (b)

Figure 6-59. Mode options when Antl.aliaslng is Auto (a) and Manual (b).

Size[% ] - Tndicates the size ofthe FOY that is measured when Anti.aliasing is

Manual. This number represents a percentage of the number entered in the

FOV parameter (under Seq. Parameter). If Mode is TimeRes, Size[% ]

defaults to 200. Figure 6-60 shows the Size[% ] parameter set to 150.

Figure 6-60. Size[%] parameter option.

# RF P rep-Allows you to enter the number of reserve RF excitations prior to

scanning. This value can affect both image contrast and artifacts.# RF Prep is

avai lable when Sequence is BASG.

DummyEcho- AIIows the short TE s ignal component to be skipped when

acqu iring heavi ly T2-weighted images. DummyEcho is available when

Sequence is Prime FSE or Prime Fm.

6· 39

0AS Is~ MRI System Reference Manual T'MhtJen.t MqMt

6-40

NaviEcho - Determines if the navigation echo used for compensation is

acquired. NaviEcho is automatical ly set to ON when Sequence is DW EPI and

Shot Num. is 2 or more.

• off- The navigation echo is acquired .

• ON- The navigation echo is acquired and compensation is implemented.

RF P hase- Allows you to enter the phase angle of the RF pulse when the RF

pulse is used to control the previous excitation s ignal. The un it is degrees. RF Phase is available when Sequence is BASG or PBSG. RF P hase is displayed

but unavailable when Sequence is RSSG, TOF, PC, or RSSG EPI.

Figure 6-61 shows that Sequence is BASG, with# RF Prep set to 37 and RF

Phase set to 11 7.

o4 44 s lii:!:II EIII

Figure 6-61. RF Phase parameter example.

P hase D ilr. A- Specifies the phase encod ing direction for t he axial (AX) plane.

Phase Dilr. A is available when Slice Plane is AX, SA, CA, or SCA. As shown

in figure 6-62, the options are:

• A-P- Sets the phase encoding direction as Anterior-Posterior.

• R-L- Sets the phase encoding direction as Right-Left.

Figure 6-62. Phase Oir. A options.


Note: More echoes need to be acquired to fill the measurement space in order to acquire images with the same spatial resolution as~atofNonnaiScan. Th~

results in a longer scan time than that of Nonnal Scan.

Note: If chemical shift occurs when using RADAR, the fat in the image may be blurred ..

QS4-53287v4

Scan Parameters 0 Phase Dir. S-Specifies the phase encoding direction for the sagittal (SAG)

plane. P hase Dir. Sis available when Slice Plane is SAG, SA, SC, or SCA. As


• A-P- Sets the phase encoding direction as Anterior-Posterior.

• H-F - Sets the phase encoding direction as Head-Foot.

Figure 6-63. Phase Dir. S options.

Phase Dir. C - Specifies the phase encoding direction for the coronal (COR)

plane. Phase Dir. Cis avai lable when Slice P lane is COR, CA, SC, or SCA. As


• R-L-Sets the phase encoding direction as Right-Left.

• H-F - Sets the phase encoding direction as Head-Foot.

RADAR

IQ144Q!I ~R-L R-L 1-1-F

Figure 6-64. Phase Dir. C options.

RADAR (RADial Acquisition Regime) is a nonorthogonal sampling scan

function, which samples K-space in a radial pattern. It is used to reduce motion

artifacts.

The RADAR section of the ScanParameterList window (figure 6-65) contains

the following parameters:

Figure 6-65. The RADAR section of the ScanParameterList window.

A Caution RADAR can create artifacts in the tangential and circumferential directions,

unlike artifacts that may occur with conventional scan methods. Care should be

taken to avoid a potential misdiagnosis.

RADAR- Specifies whether the RADAR function is ON or off. RADAR can

be used when Sequence is FSE, FIR, primeFSE, primeFffi, SE, or BASG.


Note: If homogeneity of the magnetic field is poor, FatSat is vulnerable to magnetic field distortion and the fat suppression effect is lowered due to the generation of artifacts. Therefore, be sure to carry out volume shimming

FfJPJ~ performing FatSat.

Blade refers to a segmented area that rotates in the measurement space.

Phase

6-42

Mode-Specifies measurement mode. As shown in figure 6-66, the options are:

• Res - Scan time increases while resolution is maintained.

• Time-Scan time is maintained and resolution decreases.


Proj#- Displays the total number of acquired echoes. Proj# is set

automatically, according to the value of Phase# (under Seq. Parameter).

E . Factor-Sets the number of echoes acquired per Blade. As E . Factor

increases, scan time decreases.

Blade-Displays the number of Blades used in the RADAR acquisition. The

system automatica lly calcu lates and displays the number of Blades, based on the

values of the Proj.# and E. Factor parameters. Blade approximates the Proj.#

value divided by the E. Factor value (Blade = Proj.# + E. Factor).

Figure 6-67 shows the relationship between Blade and E. Factor values.

Blade Phase

Figure 6-67. The relationship between Blade and E. Factor values.

Block- Indicates the number of partitions for the entire scan. Block is avai lable

when Sequence is BASG and Saturation is FatSat, or when Sequence is

BASG and Gating is anything but off.

Segment- Indicates the number of segments per FatSat pulse. Segment is

automatically calcu lated by the system using the val ues in the E.Factor, Blade,

and Block boxes as fo llows:

Segment = (Blade x E .Factor) +Block

Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Note: When STIR-type fat suppression is carried out using Tl time. do not set Saturation to FatSat.

Note: If you have not set a TR value that makes the phases for water and fat opposite (around 6.8{ms]) when Saturation is PhaseCycle, the fat suppression results may be insufficient.

QS4-53287v4

Scan Parameters 0 Saturation

The Saturation section of the ScanPat·ameterList window contains the

fo llowing parameters:

Satura tion-Provides the fo llowing options for suppressing specific signals, as

shown in figure 6-68:

• off-Does not perform signal suppression.

• FatSat- Suppresses MR signals produced by fat e lements by eliminating

specific RF waves. Clicking FatSat from the Saturation list a lso displays the

Wave, Duration, and RF amp.[%] parameters. The maximum number that

can be set in the M ulti slice box (in the Seq. Parameter area) may be reduced

ifTR is to be maintained. In addition, the SNR may decrease and contrast may

change, depending on the settings for the Duration and Off.Freq parameters.

• Segment FS-Segmented fatsat pulse used with TIGRE sequences to

maintain fat suppression in dynamic scans.

• PhaseCycle -Scanning is performed multiple times and fat signals are

selectively suppressed. M ulti scan mode (in the Scan Cont rol area) must be

set to F luoro or Dyna mic and Sequence must be BASG.

• Water Excitation- Water magnetization is selectively excited and fat

magnetization is suppressed. Sma ller composite pu lses (that add up to 90

degrees) are used; only water protons are fl ipped to the transverse plane and

can emit a signal.

• Water Saturation-Particular RF waves are irradiated to suppress MR signals emitted from water. Used only in spectroscopy (Water Saturation is

automatically selected when Sequence is MRSSE).

•w!Fi•

[A Caution

off

off FatSat Phase Cycle Water ExcJtabon

~·-·m•liiliilll off · )

I ~:tSat SegmentFS Water Excrtabon

Figure 6-68. Saturation options.

Be sure to carry out shimming before starting a water excitation measurement.

6· 43


Definition: Precession refers to the secondary spin of hydrogen nuclei when placed within a magnetic field.

6. 44

Additional Parameters when FatSat is selected

When FatSat is selected from the Saturation list, as shown in figure 6-69, the

fo llowing additional parameters are avai lable:

Figure 6-69. Clicking FatSat from the Saturation list displays additional parameters.

Wave- Provides options for the waveform of the fatsat pulse, as shown in

Figure 6-70. Each of these waveforms maintains a minimum TR, which limits

the number of slices available. H-Sinc Light suppresses lipids. H-Sinc Heavy

suppresses lipids and fatty protons, which precess at the same frequency as

water.

S1nc H-Sinc Ught H-Sinc

Figure 6-70. Wave options.

When acquiring T2-weighted images with a large FOY, the fo llowing settings

are recommended:

• Sine- When Sequence is DW EPI

• H-Sinc Light or H-Sinc Heavy- When Sequence is FSE or P r ime FSE

Duration -Allows the time (in milliseconds) for the fatsat pu lse to be entered.

Duration determines the fi·equency bandwidth fo r the patient signal that is

suppressed by the fatsat pulse. Time and frequency bandwidth are inversely

related (for example, a shorter time results in a wider bandwidth).

RF amp.[% ]- AIIows the strength (RF amplitude) of the fatsat pulse to be

entered. IfRF amp. [% ] is changed, the suppression effects offat signals will

change. l 00% of the initial value is the optimal strength calculated fi·om the

Wave and Dura tion parameters.

Off.F req[Hz]- Disp lays the frequency difference (in Hz) between the fat peak

and the water peak. Off.Fa·eq[Hz] is field-strength-dependent and should not be

changed. At l.2T, the value is - 173Hz. Off.Freq [Hz] is unavailable when F req.

graph is Auto or ON.


Q54-53287v4

Scan Parameters 0 Segment- May be used to improve fat suppression results when Sequence is

BASG and Saturation is FatSat. Increasing the segment number divides the

fatsat pulse into segments. This may decrease scan time, but also decreases the

effectiveness of the fatsat pulse.

Additional Parameters when Segment FS is selected

When Saturation is Segment FS (for use with TIGRE sequences), Wave

options include Sine and H-Sinc, as shown in figure 6-71. The recommended

wave is H-Sinc, as it provides more consistent fat suppression.


Additional Parameters when Phase Cycle is selected

When Saturation is P base Cycle, the fo llowing additional parameter is

available, as shown in figure 6-72:

Quasi TimeRcs- May improve time resolution by sharing data. Quasi

T imeRes is available only when Multi scan mode (in the Scan Control area) is

F luoro or Dynamic.

off

off ON

Figure 6-72. Quasi TimeRes options.

Additional Parameters when Water Excitation is selected

When Saturation is Water Excitation, as shown in figure 6-73, the following

additional parameter is available:

Saturation

IM~M~!!~I == Water Exc1ta11o • •• 1- 1

1-1 1-2-1 1-3-3-1


Wave- Indicates the wave for the RF excitation pulse; each group of composite

pulses add up to 90 degrees. As the pulse number increases (and the total pulse

is longer), the water selection increases and the fat suppression effects improve;

however, the images will have more noise. The following options are available:

6-45


6-46

• 1-1 -0ne 45° pulse, one 45° pulse.

• 1-2-1 - 0ne 22.5° pulse, one 45° pulse (2x22.5°), one 22.5° pulse.

• 1-3-3- 1-0ne 11.25° pulse, one 33.75° pulse (3x 11.25°),

one 33.75° pulse (3 x 11.25°), one 11.25° pulse.

Additional Parameters when Water Saturation is selected

When Saturation is Wate•· Saturation, the following additional parameters are

available:

Wave- Displays the water saturation pulse excitation waveform.

Water Sat BW -Sets the water saturation pulse bandwidth (ppm).

Freq. Graph Parameter

All Saturation selections include the Freq. graph parameter, which is

explained below.

Freq. gra ph- Determines whether or not to display a frequency graph in

the Frequency Pt·escan window, which is described in the next section. The

following options are available, as shown in 6-74:

• off-Does not display the frequency graph.

• Auto- When the offset frequency for the fatsat pulse is determined in the

Exam window, that value is used during the acquisition. Auto can only be

used when Saturation is FatSat.

• ON-Displays the frequency graph . .. ,., off

off Auto ON

Figure 6-74. Freq. graph options.


Note: Hitachi recommends using the Peak method because the Weighted method is prone to error (e.g., metal in field when the field homogeneity is distorted).

Q54-53287v4

Scan Parameters 0 Frequency Prescan Window

The Frequency P rescao window, as shown in figure 6-75, displays the

frequency graph results. This window appears at the beginning of a scan when

Freq. graph is ON or when Freq. gra ph is Auto and Satura tion is FatSat.

:y Prescan Water peak

Figure 6-75. The Frequency Prescan window.

This window contains the following features:

F req uency (MHz)-Displays the center frequency of water (MHz).

Offset F requency (MHz)- Represents the precessional frequency difference

(Hz) between fat and water. This value is field-strength-dependent and should

not be changed. At 1.2T, the value is -173Hz; this is the frequency of the fatsat

pulse.

Noise Threshold (%)-Used when Weighted is selected for the Search

Mode, which is described next in this section. Noise Threshold (%) allows the

threshold percentage to be selected for determin ing the center frequency by the

center of gravity method.

Search Mode-Allows the search method to be selected for determining

frequency values from the fo llowing options:

o Peak - Peak method, where the center frequency is set at the signal's

maximum frequency value.

o Weighted - Center of gravity method, where the center frequency is set to the

center of gravity for signal values at or greater than the threshold.

Reset Param - Returns the va lues on this window to their initial settings.

CONT lNUE button - Restarts the scan.

STOP button - Stops the scan.

6·47

0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet

6-48

The graph display, as shown in figure 6-76, has the fo llowing features:

Offset frequency (fat peak)

Signal value axis

Center frequency (water peak)

Frequency (MHz) axis

Figure 6-76. Frequency Prescan window features.

• Vertical axis-Signal value

• Horizontal axis - Frequency MHz)

• Green vertical line-Offset frequency (fat peak)

• Blue ve11icalline- Center frequency (water peak)

• Red horizonta l line- Threshold when using the center of gravity method (not

shown in figure 6-76)

• Orange poi.nt-Acquisition data point (not shown in figure 6-76)

A Caution If the center frequency is changed on the graph of the frequency prescan results,

there will be an offset produced in the position of the acquisition plane. The

reference image (scanogram) should be rescanned.

While the graph is displayed, if prescann ing is canceled using the Stop

button on the Frequency Prescan window or the Abort button on the control

panel, the frequencies that have been set will not be applied to all subsequent

acqu isitions.

In addition, once the center frequency and offset frequency have been set, they

will be maintained until one of the following types of acquisitions is performed:

• Acquisition with Freq. grapb set to ON.

• Acquisition with Prescan set to ON.

• Acquisition with the Exam window changed (for example, Sequence or other

parameters have been changed).

• Acquisition with the receiver coil changed.


Note: Hitachi recommends clicking Sine from the Wave list for more uniform frequency response and better uniformity.

Q54-53287v4

Scan Parameters 0 T2W Prep (available with CardioSuite)

T2W P rep - A prepulse that enhances the T2 contrast of the imaging target.

When T2W Prep is applied to the 3D BASG sequence with FatSat, the tissue

contrast improves but the SNR drops slightly. The available options are:

• off- T2W Prep pulses are not in·adiated.

• ON- T2W Prep pulses are irradiated. When ON is selected, Duration is

displayed.

Dura tion - Sets the duration (in milliseconds) of the T2W P1·ep prepulse

application.

MTC The MTC (Magnetization Transfer Contrast) section of the ScanPa ra meterList

window (figure 6-77) contains the fol lowing parameters:

MTC 1

ON ·l S1nc

10 0

10 0

1 200

Figure 6· 77. The MTC section of the ScanParameterList window.

MTC- Changes the contrast of images by changing the magnetization

movement between bound water and free water. The MTC pulse is activated

prior to slice plane excitation.

Wave- Selects the waveform ofthe MTC pulse, as shown in figure 6-78.

QH Sine

S1nc Gauss1an


6· 49


6-50

Wave options are Sine and Gaussian, which differ in function as shown in

figure 6-79.

Sine function type Gaussian function type

Duration Duration IIIII ~

~v

1 RF amp. 1 RF amp.

Figure 6-79. Function comparison for Wave options.

Duration-Indicates the activation time in milliseconds for the MTC pulse.

This value determines the frequency bandwidth of the MTC pulse. A shorter

duration produces a wider frequency bandwidth and a longer duration time

produces a narrower frequency bandwidth.

RF amp.IIJ.Tl -lndicates the activation strength (RF amplitude) of the MTC

pulse.

Off.F req[kz] -Indicates the offset frequency (in kHz) of the MTC pulse.

VENC

The VENC (Velocity Encoding) function uses phase information to acquire the

flow rate and flow direction of blood. The VENC section of the

ScanParameterList window (figure 6-80) contains the fo llowing parameters:

Figure 6-80. The VENC section of the ScanParameterList window.


Q54-53287v4

Scan Parameters 0 VENC-Available when Sequence is PC (Phase Contrast). When VENC is

ON, a flow encode pulse is applied to target the blood flow.

The following parameters are available when VENC is ON:

Ta rget Vel. - lndicates the flow rate for the target vessel in centimeters per

second. This value is a vector volume with size and direction. The value of this

parameter is the maximum value that can be acquired on the flow rate image;

however, flow rates that exceed the value set wi ll be acquired as flows in the

reverse direction.

VENC Dir#- lndicates the number of axes where the flow encode pulse will

be applied. Provides the fo llowing options, as shown in figure 6-81 :

• 1 - Applies the flow encode pulse to one axis. Use the VENC Dir. parameter

(described next in this section) to select this axis.

• 3 -Applies the flow encode pulse to the following three axes: the A- P axis

(front-back direction), the R-L axis (right-left direction), and the H-F axis

(body axis direction).

Figure 6·81. VENC Dlr# options.

VENC Dir. - Available when VENC Dir# is 1. Allows you to select the one

axis to which the flow encode pulse will be applied. As shown in figure 6-82, the

options are.

• A-P- Applies the flow encode pulse to the A-P axis.

o R-L-Applies the flow encode pulse to the R-L axis.

o H-F - Applies the flow encode pulse to the H-F axis.

•••• IEJF 9

A-P R-L H-F

Figure 6-82. VENC Dir. options.

Vel. Image- Reconstructs a flow velocity image in each axis, in addition to the

differential combination image.

Comb. Image- Reconstructs the differential combination image (angiography

image); defaults to ON. These images can be used for the Ml P post-processing

task. This task is described in the "Task MIP" section of Chapter 8, " Post

Processing Tasks."

6. 51


Note: When a multi-slab scan is performed using SSP, the following must be considered when selecting the Rate parameter:

Since the slab is excited when sloped in the slice direction with SSP, the flip angle varies at the higher and lower parts. The difference of this flip angle appears as contrast.

The difference of contrast of stationary tissue appears as the edge of a step between slabs. However, the step is not always the same, and will not be prominent if Rate is low, but will be if Rate is high.

Note: Single-slab scanning is recommended with SSP.

6-52

SSP The SSP section of the ScanParameterL ist window (figure 6-83) contains the

following parameters:

SSP .• •· (ON ·J .... 11 5 I· I· ! 1!§!1.11 F < H I H<F

F<H .....

Figure 6-83. The SSP section of the ScanParameterList window.

SSP (Sloped Slab Profile)- Applies an RF pulse using gradient profile

excitation to minimize the saturation of blood flow within a volume (slab).

SSP is available when Sequence is TOF and 2D/3D is 3D. Changing the RF

excitation angle inside the slab affects the spins (in the flowing blood) as they

move through the volume. A smaller angle is needed for blood entering the

volume; the angle shou ld increase as the blood flows tlll'ough the volume.

Rate - Indicates the RF pulse ratio (slope) of inflow region to outflow region.

A larger volume demands a steeper slope, as it takes more time for blood to flow

through this larger area. The options are:

• 1.5 - The ratio is 1:1.5 (smallest slope).

• 2 - The ratio is I :2.

• 2.5 - The ratio is I :2.5.

• 3 - The ratio is 1:3 (steepest slope).

Direction - Specifies the RF pulse gradient direction. Select one of the

following options to increase the RF pulse in the specified direction:

• F<H- Increases from feet to head.

• H <F- Increases from head to feet.

• R <L- In creases from right to left.

• L<R-Jncreases from left to right.

• A<P- Increases from anterior to posterior.

• P<A- lncreases from posterior to anterior.

The options that can be selected for each sl ice plane are as follows:

• For AX-F<H and H<F

• For SAG- R<L and L<R

• For COR- A<P and P<A

Example: For the Circle of Wi llis (COW), the F<H direction would be used.

Th is places the smaller angle at the feet, where the blood enters the volume.

Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.

Note: Since MPG pulses are applied in Diffusion Tensor Imaging, it is sensitive to motion. In multishot measurements. to reduce artifacts due to motion. use pads to immobilize the patient as much as possible and use gating.

Q54-53287v4

Scan Parameters 0 MPG

Motion Probing Grad ients (MPG) are the gradient magnetic fields used in

diffusion weighted imaging. These gradients are needed when imaging the

proton diffusion phenomenon. The MPG section is avai lable when Sequence is

DW EPI.

The MPG section of the ScanParameterList window contains the following

parameters:

MPG (Motion Probing Gradient) - Specifies if the MPG function is ON or off.

MPG Dir#-Selects the number of <L'\es to which the MPG pulse is applied.

The fo llowing options are available, as shown in figure 6-84:

• Single-Applies the MPG pu lse to the A-P, R-L, or H-F axis.

• Trace-Applies the MPG pulse to the three axes in sequence.

• Tensor6- Applies the MPG pulse to six axes, which inc ludes A-P, R-L, H-F,

and three oblique directions: A-P with R-L, A-P with H-F, and H-F with R-L

(this is a purchasable option associated with the Diffusion TensorSuite).

• Tensor7-Applies the MPG pulse to seven axes (this is a purchasable option

associated with the Tensor Suite).

• Tensorl3-Applies the MPG pulse to 13 axes (this is a purchasable option


• Tensor21 - Applies the MPG pulse to 21 axes (this is a purchasable option


I' &•• ll Single

S1rgle Trace Tens011l Tensor7 Tensor13 Tensor21

Figure 6-84. MPG Dir# options.

G rad ient Mode- Indicates the mode to which the MPG pulse is applied. The

following options are provided, as shown in figure 6-85:

• Single- Applies the MPG pulse to the axis selected in MPG Dir #.

• Complex-Applies the MPG pulse to the three axes (A-P, R-L, H-F).

This parameter is unavailable when MPG Dir# is Tensor6, Tensor7, Tensor13,

or Tensor21.

IAIEFIIIW Single . [I Single Complex

Figure 6-85. Gradient Mode options.

6· 53

0AS Is~ MRI System Reference Manual Th41hU ... tMqnet

Note: Hitachi recommends using a b-factor of 1000, which is the clinical standard. Different b-factors can be used based on radiologist preference.

6-54

b-factor-AIIows the b-factor ofthe MPG pulse to be entered. The application

time and application strength of the MPG pulse are automatically calculated

based on the b-factor value.

MPG Dit·. -AIIows you to select the application axis. MPG Dir. is avai lable

when MPG Dir# is Single. The following options are provided, as shown in

figure 6-86:

• A-P-Applies the MPG pulse to the A-P axis.

• R-L-Applies the MPG pulse to the R-L axis.

• H-F - Applies the MPG pulse to the H-F axis.

Figure 6-86. MPG Dir. options.

Scan Control

The Scan Control section of the ScanParameterList window (figure 6-87),


·T ·T

Mi.@,!. ON @ii .. A.I· (Fo=ff=---..,. r

'''11'·1.& I off • l 5*"3- r off ·1 ij.IMMHI[ ott . ]

iiiJ¥!i Auto

Figure 6-87. The Scan Control section of the ScanParameterList window.


Q54-53287v4

Scan Parameters 0 Scan mode -Specifies the mode, if scans are to be repeated. The following

options are provided, as shown in figure 6-88:

• Once- Repeats only once.

• Discontinuous- The system asks with each repetition whether to perform the

scan or not.

• Every - Perfonns a scan the number of times equal to the va lue specified in

the R epeat Number parameter, described later in this section.

IIIIIII~JE~w~~~----~ Once

Figure 6-88. Scan mode options.

Multi scan mode- Specifies the performance mode for the scan. The following

options are available, as shown in figure 6-89:

• Normal--Performs a normal scan.

• Dynamic -Perfonns a scan that repeats multiple times. The time interval for

scans to be repeated can be set.

• Fluoro--Repeats a scan a number oftimes in as short a period as possible.

During scanning, parameters can be changed in real time.

IIMF!,I,;;ea Normal ~----'-------1

Normal Oynam1c Fluoro

Figure 6-89. Multi scan mode options.

Wait mode--Specifies the scan wait mode. The fo llowing options are

available, as shown in figure 6-90:

• off- Does not pause before starting a scan.

• Auto - When Wait# is used to perform a multi-acquisition scan with multiple

breath holds, Auto enables the Auto Voice function to automatically give

breath-hold instructions for each acquisition. The user does not have to press

the CONTINUE button for each acqu isition to be acquired.

• ON- Pauses before starting the scan once the prescan is fi nished; timing of

the pause is detenn ined by the value in Wait#.

*iiMf ~o~ff----'-------1 off Auto ON

Figure 6-90. Multi scan mode options.

6· 55


6-56

Wait#- Indicates the number of acquisitions the system will perform prior to

pausing. Wait# is avai lable when Multi scan mode is N01·mal or Dynamic,

Wait mode is ON, and Multi Acquisition (in the Seq. Parameter area) is 2 or

more. Wait# must be one number lower than the va lue in Multi Acquisition.

The following options are available:

• 0- Scanning is petformed continuously.

• ! - Pauses once before starting the main acqu isition; the system counts the

prescan as the first acquisition.

• 2 or more- Pauses after performing two or more acquisitions, depending on

the number of acqu isitions set in Multi Acquisition . For example, with Multi

Acquisition set to 5, and Wait# set to 3 , the system will perform the prescan

and two additional acqu isitions before pausing.

After pausing, click the CONTINUE button (figure 6-9 1) to resume scan ning.

Figure 6-91. Click CONTINUE to resume scanning.

BH T ime- Indicates the longest of scan times from standby status to next

standby status. BH Time is displayed when Wait# is not 0.

Sta r t wait time-Sets the wait time before the scan sta1ts. This is displayed as

minutes:seconds.tenths-of-seconds, as shown in figure 6-92. Start wait time is

only available when Multi scan mode is Normal and Wait mode is off.

@fh@lii!i loo·oo o

Figure 6-92. Start walt time.

Repeat Number - Specifies the number of repetitions of the scan. Repeat

Number is only available when M ulti scan mode is Normal and Wait mode is

off.

No of scan set-Antows you to specify the num ber of scan repetitions and the

repetition interval (or wait) for each set (scans can be divided into a number of

sets with a maximum of 3). No of scan set is available when Multi scan mode

is Dynamic.


Q54-53287v4

Scan Parameters 0 Pre-Cont. (Pre-Contrast) - Specifies the number of repetitions for the first set of scans. Figure 6-93 indicates three repetitions for this first set.

delay time (for Pre-Cont.) - Specifies the wait time for the start of the first set.

This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Pre-Cont.)-Specifies d1e interval (in seconds) between

repetitions of the first set. Pre-Cont. must be set to 2 or more.

Scan#1 1st Gap Time

Scan#2 1st Gap Time

Scan#3

.. • .. ... .. • Individual Scan Time Individual Scan Time Individual Scan Time

Figure 6-93. Pre contrast illustration.

wait mode (for Pre-Cont.) - Provides the following options for the first set of repetitions:

• off- Does not pause when sta1ting.

• Every -Pauses with each repetition. When Every is selected, gap time is

hidden from view.

• Once- Pauses only for the first repetition.

After pausing, c lick the CONTINUE button to resume scanning.

Ea rly Post Cont. (Early Post Contrast)- Specifies tbe number of repetitions

for the second set of scans. Early Post Cont. is available when No of scan set is

set to 2 or 3.

delay time (for Early Post Cont.)-Specifies the wait time for the start of the

second set. This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Early Post Cont.) - Specifies the interval (in seconds) between

repetitions of the second set. Early Post Coot. must be 2 or more.

wait mode (for Early Post Cont.)- Provides the following options for the

second set of repetitions:

• off- Does not pause when starting.

• Every- Pauses with each repetition. When Every is selected, gap time is hidden from view.

• Once- Pauses only for the first repetition.

After pausing, click the CONTINUE button to resume scanning.

6·57


6-58

Late Post Cont. (Late Post Contrast) - AIIows you to specify the number of

repetitions for the third set of scans. Late Post Cont. is available when No of scan set is set to the maximum va lue of3, as shown in figure 6-94.

Figure 6-94. Late Post Cont. is available when No of scan set is 3 (max. value).

delay time (for Late Post Cont.) -Specifies the wait t ime for the start of the

third set. This is displayed as minutes:seconds.tenths-of-seconds.

gap time (for Late Post Cont.)- Specifi es the interval (in seconds) between

repetitions of the third set. gap time is avai lable when Late Post Cont. is 2 or

more.

wait mode (for Late Post Cont.) - Provides the following options for the third

set of repetitions.

• off- Does not pause when starting.

• Every- Pauses w ith each repetition. When Every is selected, gap time is

hidden from view.

• Once- Pauses on ly for the first repetition.

After pausing, c lick the CONTINUE button to resume scann ing.


Q54-53287v4

Scan Parameters 0 Contrast agent-Allows a contrast agent to be specified , when scanning with a

contrast agent (figu re 6-95). If Multi scan mode is Dyna mic, No of scan set

must be a value greater than I to make Contrast agent available. The list of

contrast agent options can be customized in the Patient Registration Setting

window. Refer to Chapter 4, "Patient In formation Functious," fo r complete

contrast agent option list customization details.

HM(ott ·I off None Femseltz Feme arrvnon1um crtrate Fendex Ferumax>des ProHance Gadotendol Magn..,st MegiUilWle gadapentetate Gad PrimCMst

Figure 6-95. Contrast agent options.

Volumelml] - Volume[ml] is available when a Contrast agent is selected. Sets

the volume of contrast agent to be used in milliliters, as shown in figure 6-96.

Figure 6-96. Volume[ml] example.

Travel T ime- Used during contrast-enhanced magnetic resonance angiography

(CE-MRA). Enter the time it will take for contrast to arrive at the target area,

wh ich is determined from the test injection during the dynam ic scan

measurement (figure 6-97).

MM+g;;w Gad

... [30:0"" =r 9 I £ 0

"i'"IA I oo 24 o I

Figure 6-97. Travel Time example.

Additional parameters displayed under Travel Time include:

OffsetT ime-Used during CE-MRA. Displays the time that should be the

initial setting for the stop watch. The contrast agent is to be injected when the

stop watch reaches zero.

ContinueTime-Uscd during CE-MRA. Displays the timing when the contrast

agent is injected and the CONTINUE button is c licked.

6· 59

0AS Is· MRI System Reference Manual n. htJ•t llqJMt

6-60

O rg. I mage- Specifi es whether or not to reconstruct the source images, as

shown in figure 6-98. Org. Image is avai lable when M ulti scan mode is

Dynamic or F luoro, and Sub. Image (described next in this section) is Fixed,

Moved, or FxMv.

i¥1Qipiil ON

J, off ON

Miiii' ON

@ii;,pi!l Fixed

Figure 6-98. Org. Image and Sub. Image settings to reconstruct source images.

Sub. Image-Specifies the method for creating subtraction images for dynamic

scans. Sub. Image is available when Multi scan mode is Dynamic or Fluoro.

The fo llowing options are available, as shown in figure 6-99:

• off- Does not create a subtraction image.

• Fixed-Creates subtraction images using the first scan as the mask for all

subsequent scans (fixed mask).

• Moved- Creates subtraction images in wh ich each scan uses the previous

scan as its mask (moved mask).

• FxMv-Creates both types of subtraction images: fixed and moved.

A Caution

off Fixed Moved rxMv

Figure 6-99. Sub. Image options.

When subtraction is pe1formed, immobilize the patient as much as possible so

the images are as unsusceptible as possible to body movements.

The examples show how fixed and moved subtraction images are created:

Example: In fixed subtraction, scan I is subtracted from scan 2, scan 1 is

subtracted from scan 3, and so on. The mask is fixed using scan 1 (figure 6-1 00).

Fixed-subtracts 2-1 3-1 4-1

Figure 6-100. A fixed subtraction example.


Q54-53287v4

Scan Parameters 0 Example: In moved subtraction, scan 1 is subtracted from scan 2, scan 2 is

subtracted from scan 3, and so on. The mask moves from scan to scan (fi gure

6-10 1).

Moved-subtracts 2-1 3-2 4-3

Figure 6-101. A moved subtraction example.

Sub. Mask Start#- A IIows you to enter the number of the scan that statts the

subtraction processing when M ulti scan mode ( in the Scan Con trol area) is

Fluoro or Dyna mic. A black image (an image with a ll pixel values set to 0) is

output until the start of subtraction processing. The examp·les show how images

are created when the va lue for th is parameter is set to 3.

Example: Fixed mask subtraction, where scan 3 is the mask scan (figure 6-1 02).

Figure 6-102. Fixed mask subtraction using a Sub. Mask Start# value of 3.

Example: Moved mask subtraction where scan 3 is the first mask scan (figure

6-103).

Figure 6-103. Moved mask subtraction using a Sub. Mask Start# value of 3.

6-61


Note: If moving the patient table during volume shimming correction, the shimming correction effect is lost. Therefore, movement of the patient table by the Centering option is disabled when the center of scan position is included within the volume shimming scan region. If the center of scan position is not included within the volume shimming scan region, the result of volume shimming is canceled and the patient table is moved.

Note: Static magnetic field distribution data of the volume shimming to be used in regional shimming needs to be acquired again when moving the patient table with the Centering option.

Note: When Shading is NATURAL or when RAPID Mode is RCM, a warning message is displayed prompting you to redo the S-Map measurement if the patient table is moved approximaely 2 inches (Scm) or more by the Centering option. When aliasing artifact or nonuniformity of sensitivity occurs in a scanned image, redo the S-Map measurement.

6-62

When Multi scan mode is Dynamic, Sub. Mask Start# cannot be greater than

the sum of the Pt·e-Cont., Early Post Cont., and Late Post Cont. values.

Disk save-Available when Multi scan mode is Fluoro. Provides the

following options for saving images to the database (figure 6-1 04 ).

• off- Only the images for which the SAVE butto11 on the Exam window was

clicked wi ll be saved to the database.

• ON- Saves all images to the database.

Figure 6-104. Disk save options.

Table move-Provides the following options for moving the patient table, as

shown in figure 6-l 05:

• off- Does not move the table.

• Centering- Moves the table to the center of the magnetic field , depending on

the position of the acquisition plane.

• Manual-Moves the table to the position that has been entered in the

Position[mm] parameter (described next in this section).

off

off Centering Manual

Figure 6-105. Disk save options.

Posit ion[mm]- Available when Table move is Manual. Allows you to enter

the distance of patient table movement in mill imeters, as shown in figure 6-106.

==·= r Manual •J :;;..§ =:J· l· l

Figure 6-106. The Position[mm] parameter.


Note: When Auto Voice is ON, the following parameter checks and recalculations are made:

If gap time between each scan (Pre-Cont .. Early Post Cont., and Late Post Cont. l in Dynamic scan mode is shorter than the voice output time (SCANEND(Every) t SCANSTART(Every)). then gap time ts recalculated. If wait mode is set to Every, delay time is recalculated.

When wait mode is off for each scan in Dynam1c scan mode and delay time is shorter than the voice output time (SCANEND(Every) t SCANSTART(Every)). delay time is recalculated.

When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the SCANSTART(Once) or SCANSTART(Every) time, de/a}' time is recalculated.

Note: When Multi scan mode is Fluoro (or Normal and Wait mode is off and a Repeat Number value is specified). phrases are not output during each scan repetition even if SCANEND(Every) and SCANSTART(Every) are set to ON.

054·53287v4

Scan Parameters 0 Table Wait Mode- Enables/disables the patient table wait mode:

• off- Wait mode is not activated.

• ON- Wait mode is activated. Press the CONTINUE button to move the table.

C hime (available only when Auto Voice option is not r·egiste red) - Enables/

disables the chime sound when the patient table is moved:

• o ff- The chime does not sound when the patient table is moved.

• ON- The chime sounds before the table is moved ..

Auto Voice- Specifies whether or not to output an auto voice pattern. The

auto voice pattern can be created in the A uto Voice Setting window, as shown

in figure 6-107. For more information about creating an auto voice pattern, see

the "Auto Voice Setting Window" section of Chapter 9, "Additional Launcher

Functions."

When Auto Voice is off, Start wait time (when Multi scan mode is Normal

or Fluoro) or any of the delay time text boxes (when Multi scan mode is

Dy namic) automatically reset (display 00:00.0 instead ofthe minutes, seconds,

and tenths of seconds that were entered).

After creating a new auto voice pattern, you will need to close and reopen the

Exam window. Auto Voice then becomes available.

Figure 6-107. The Auto Voice Setting window.

6· 63


Note: • When performing RAPID

sequences, use RAPID receiver coils.

• Some RAPID coils have a restriction on the phase encode direction available for scanning.

• The RAPID factor and direction is different for each RAPID coil.

• Image quality could be reduced if the imaging center deviates greatly from the receiver coil center.

• Image quality could be reduced if slab thickness is set to a smaller value during a RAPID sequence in the slice direction.

Note: With EPI sequence and primeFSE!primeFIR sequence (only EchoAI/ocation is ADA), RAPID measurement makes that E. Factor decreases with Shot Num. fixed and the total scan time does not decrease.

6-64

Sync. StopWatch -Starts the timing in the StopWatch window simulta neous ly

with the acquisition. Choose from the following options, as shown in figure

6~108:

• off- Does not synchronize the start of the StopWatch window with the

acquis ition.

• ON- Synchronizes the start ofthe StopWatch w indow with the acquisition.

f .IMMMNM off off ON

Figure 6-108. Sync. StopWatch options.

P rescan- Specifies the prescan mode. Choose from the following options, as

shown in figu re 6-109:

• Auto-Automatically performs appropriate prescan measurements based on

data from the previous scan.

• ON - Performs prescan measurements at the beginning of the first scan,

acquiring new data. Th is setting should be used on the first scan for each new

patient.

RAPID

144*§ Auto Auto ON

Figure 6-109. Prescan options.

The Rapid Acquisition through a Parallel imaging Design (RAPID) function

shortens the scan time. By using multichannel receiver coils, phase encoding is

decreased during the acqu isition according to the value set in the RAPID box.

Generally, when decreasing the phase encod ing for an acquisition, aliasing

is produced in the image following reconstruction. The RAPID acquisition

function acquires the data using multichannel receiver coil s. It develops the

image using a sensitivity map of the receive r coils, thus e liminating aliasing

and shortening the scan time. The SNR of the image is reduced as the value of

RAPID is increased.

You cannot use RAPID unless you perform an S-map that covers the imaging

region. When performing an S-map with RCM, set the imaging region so that it

sufficiently covers the area of interest. If this area is not sufficiently covered, an

error wi ll occur when starting the main scan.

Duri.ng S-rmp with RCM, a wide imaging region is captured using the TR Body

coil. S ince the scanogram is performed using the RF coi l, care is required so that

even regions that are not captured in the scanogram do not cause wrap artifacts.


Note: Using ADA and RAPID results in a decrease in Echo factor per shot. so that the slice number can be increased without increasing scan time. When RAPID is utilized and Echo A/Joe. is set to ADA for EPI, Prime FSE. or Prime FIR sequences. image blurring and distortion are minimized. resulting in improved image quality.

Q54-53287v4

Scan Parameters 0 For example: When taking images of the trunk of a patient's body, the patient's

anns outside the FOV might cause wrap artifacts during S-map acquisition.

Th is could lead to faulty sensitivity correction in the main scan, and therefore

care is required when specify ing the settings. Similarly, when taking images

of lower extremities such as the knees or upper extremities such as the e lbows,

other body areas outside the FOV might cause wrap artifacts during S-map

acquis ition. This could lead to faulty sensitivity correction in the main scan, and

therefore care is required when specifying the settings.

Since the system is sensitive to any movement by the patient, it is important

to have the patient remain as still as possible during S-map Normal mode

acqu is ition. To accommodate for patient motion such as breathing and

peristalsis, we recommend the Nest mode ofthe S-Map sequence.

ln addition, the following precautions are required to acquire effective three

dimens ional sensitivity distribution data when using S-Map:

• Specific positioning and imaging parameter settings to prevent wrap a11ifacts

in the region where the main scan is to be perfonned.

• A I though the cross-section to be acquired depends on the a rea where imaging

is being performed, to avoid wrap artifacts we recommend that you select

COR or SAG, in which the frequency direction is usually along the axis of the

patient's body.

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0AS Is~ MRI System Reference Manual Th41hU ... tMqnet

Note: Figure 6-110 shows how the RAPID function creates images.

Because aliasing artifact appears stronger in the center area of the

image when performing RAPID 0 scans, it is necessary to set a slightly larger FOV and to set the imaging area in the phase direction to cover the entire Coil sensitivity map

imaging object using the Anti.aliasing function.

6-66

Aliased image

Image development anti-aliasing

Figure 6-110. /mage creation using RAPID.

0 Resulting image

The RAPID section of the ScanParameterList window contains the following

parameters:

RAPID(Phase), RAPID(Siice) - Decreases the phase and slice encod ing

in the acquisition according to the values entered, resulting in reduced scan

duration. RAPID(Phase) and RAPID(Siice) values range from 1.0 to 4.0,

with a precision of 0.1 step. As va lues are entered in the RAPID(Phase) and

RAPID(Siice) boxes, RAPID(Total) is automatically calculated and updated.

For example, when RAPID(Phase) is 1.4 and RAPID(Siice) is I .6,

RAPID(Total) will be 2.2 (the second digit to the right of the decimal point

is omitted). RAPID acquisition is not performed when RAPID(Phase) and

RAPID(Siice) are both 1.0, wh ich is the defau lt va lue.

RAPID(Siice) is available when 2D/3D is 3D and Sequence is RSSG or

BASG. RAPID(Siice) is a lso available when 2D/3D is 3D, EchoTime Mode is

Optimized, and Sequence is FSE, FIR, primeFSE, or pl"imeFSR.

RAPID(Total)- Disp lays the product of the values entered in the

RAPID(Phase) and RAPID(Siice) boxes. This calculation is based on the

equation: RAPID(Phase) x RAPID(Siice) = RAPID(Total).


Note: Because the timing to acquire a coil sensitivity map is different depending on the RAPID Mode (even if the same RAPID factor is set). the reduction rates of the scan times are different.

Note: Because data for a sensitivity map is acquired during the prescan in PCM mode. the prescan time is longer than that of other modes.

Note: Because data for a sensitivity map is acquired during the main scan in SCM mode, the scan time of the main scan is longer than that of other modes. However. the prescan time is the same as that of a normal scan.

Note: RCM mode uses an S-Map to prepare the 30 sensitivity map in advance. Acquisition of a 30 sensitivity map using an S-Map urder typical imaging conditions takes approximately 40 seconds.

Q54-53287v4

Scan Parameters 0 Mode- Specifies the calibration method for the RAPID acquis ition. The

method may be selected automatically, based on the Sequence that has been

selected. The following options are ava ilable, as shown in figure 6-111:

• PCM (Prescan Calibration Method)-Acquires the coil sensitivity map during

prescan. T he additional options available with this mode are described next in

this section.

• SCM (Self Calibration Method)-Acquires the coil sensitivity map during the

RA PID scan. This is the default mode when certain sequences are selected.

• RCM (Reference Calibration Mode)- Uses the sensitivity map acquired

duri ng the S-map scan.

RCM I SCM PCM

Figure 6-111. RAPID Mode options.

When Mode is PCM, the fol lowing additional parameters are available:

PCM Mod e-Determines the control method for collecting a coil sensitivity

map during prescan. The default value is Auto, as shown in figure 6-112.

Auto

Figure 6-112. The PCM Mode parameter.

The following options are available, as shown in figure 6-113:

• Auto- Automatically determines whether or not to use the coil sensitivity

map collected during the previous prescan. If it can be used, reacquisition

ofthe coil sensitivity map is not performed. If there is no previous coil

sensitivity map, it is collected. Reacquisition of the sensitivity map wi II not

be performed if the fo llowing conditions are the same as during the previous

collection:

- Slice position, oblique angle, slice interval

-Slice plane, phase direction

- Multi-sl ice, multi-acquisition

- FOV, reconstruction matrix

• ON- Collects a sensitivity map during each prescan.

Au10 ON

Figure 6-113. PCM Mode options.

6·67


6-68

PCM Wait mode- Specifi es whether or not to have a wait mode before

collecting a coi l sensitivity map during the prescan. Choose from the following

options, as shown in figure 6-114:

• off-Does not go to standby before collecting a coil sensitivity map.

• ON - The status changes to standby before co llecting a coil sensitivity map.

Figure 6-114. PCM Wait mode options.

PCM NSA-Sets the number of signal averages when collecting the co il

sensitiv ity map duri11g the prescan. The larger the value, the better the image

quality becomes; however, the prescan time is increased. The default (init ial

value) is I , with a maximum value of 8.

Gating

The Gating section of the ScanParameterList window contai ns the following

parameters:

Gating-Allows the type of gated scan to be selected. Choose from the

fo llowing options, as shown in figure 6-1 15:

• off-Gated scan not selected.

• MS-ECG- Eiectrocardiograph (pu lse wave) gated scan selected.

• Cine-Cine gated scan selected.

• Resp- Respiratory gated scan selected .

• ij (off · P off MS.ECG Cine Resp

Figure 6-115. Gating options.

The additional parameters that are available will vary with the type of gating

selected, the Sequence that is selected, and related scan parameters. In the

fo llowing parameter descriptions, applicable gating types are included in

parentheses after the parameter names, as shown in the example:

Example: Beat Rate (MS-ECG, C ine, Resp) indicates that the Beat Rate parameter applies to MS-ECG, Cine, and Resp gati ng.

Beat Rate (MS-EC, C ine, Resp)-Enter the heart rate (in beats per minute) for

MS-ECG and Cine gating. Enter the respirato1y rate for Resp gating. The heart/

respirat01y rate is displayed in the WaveForm window.


Q54-53287v4

Scan Parameters 0 # HB Prep (Cine [available with CardioSuite])-lndicates the reserve heart rate

prior to petforming the acquisition. The Gate Mode parameter (located two

parameters below# HB Prep) must be Delayed, as shown in figure 6- 11 6.

Mil& C1ne . ·1 .•. , 66 I· '· ' ""1141 2 I· ... #1111·A111' ECG :1 Mil' ll Delayed _______:]

Figure 6-116. The # HB Prep parameter with the Delayed Gate Mode requirement

Gating Source (MS-ECG, Cine, Resp)- lndicates the signal source for the

gated scan. Select from the following options:

• ECG - Indicates the electrocardiograph as the signa I source. ECG can be

selected when Gating is MS-ECG or Cine, as shown in figure 6-117.

• Pulse- Indicates the peripheral pulse as the signal source. Pulse can be

selected when Gating is MS-ECG or Cine, as shown in figure 6- 117.

ECG Pulse

Gating is MS-ECG

ECG Pulse

Gating is Cine

Figure 6-117. Gating Source options.

• Resp- lndicates respiration as the signal source. Resp is the fixed default

when Gating parameter is Resp.

Gate Mode (MS-ECG, Cine) - Ind icates the electrocardiographic synchronous

mode. Choose from the fo llowing options, as shown in figure 6-118:

• Gate- Gate method

• Trigger- Trigger method

• Delayed-Delayed enhanced method (available with CardioSuite)

• MyoPer- Myocardial perfusion method (available with CardioSuite)

*I"' Gate

Gate Tngger Delayed

Per

Figure 6-118. Gate Mode options.

6· 69


6-70

Resp Mode (Resp)- Indicates the respiratory synchronous mode; the fixed

default is Trigget·, as shown in figure 6-119 .

•• ,, Trigger

Figure 6-119. The Resp Mode parameter.

Count (MS-ECG, Cine, Resp) - lndicates the number ofR-wave intervals or

respiratory cycles needed to collect the desired amount of slices. The Count

value is dependent on the heaJt rate (a higher heart rate, with shorter R-R

intervals, requires an increased Count to obtain more slices). When Gate Mode

or Resp Mode is Trigger, Count affects the TR. The value of 1 is automatically

set when Gate Mode is Gate.

Multi Phase (Ci ne) - lndicates the number of images to be taken at the same

position but at different heart phases. In figure 6-120, Gating is Cine and Multi

Phase is 24.

Cine

''"' ll

Figure 6-119. The Mult Phase parameter.

Segment (MS-ECG [with CardioSuite], Cine) - lndicates the segment number.

Increasing the segment number allows less slices per R-R waveform. Segment

can be specified in the following cases, as shown in figure 6- 120:

• When Gate Mode is Gate

• When Gate Mode is Trigger and Sequence is BASG, SARGE, or RSSG

• When Gate Mode is Delayed and Sequence is BASG

Gate Mode is Gate, Segment is 3 Gate Mode is Trigger, Segment is 3

Figure 6-120. The Segment parameter.


Q54-53287v4

Scan Parameters 0 DelayMode (Resp) - lndicates the input unit for Delay measurement. Select

from the following:

• Time - Sets the Delay in milliseconds (ms). The Delay represents the time

from the trigger signal to the initial slice TE.

• Rate- Sets the Delay as a percentage(%). The Delay represents a percentage

of the breathing cycle from the trigger signal to the TE of the initial slice.

Delay[ms] (MS-ECG, C ine, Resp) - Indicates the time in milliseconds from the

trigger signal until the TE of the initially acquired slice.

Delay (%) ( Resp)-Indicates a percentage of the breathing cycle as the delay

from the trigger s ignal to the TE of the initial slice.

Interval (MS-ECG, Cine, Resp)- Indicates the time interval between the

collection of each s lice or each phase.

Echo Alloc. (MS-ECG, Cine)- AIIows selection of the echo allocation method.

This setting can be specified in the fo llowing cases:

• When Gate Mode is Gate

• When Gate Mode is Trigger and Sequence is BASG

Choose from the fo llowing options:

• Sequential - Arranges segments sequentially.

• Centric - Arranges segments centrica lly. Centric is available when Sequence

is BASG (2D), BASG (3D, with Gate Mode set to Trigger), SARGE (2D),

RSSG, PC, TOF, or RSSG EPI.

Figure 6-121 illustrates the allocation of acquisition data for the two Echo Alloc.

methods.

Phase encoding direction

Segment#1 Segment#4

Segment#2 Segment#3

Segment#3 Segment#2

Segment#4 Segment#1 Segment#5 Segment#1

Segment#6 Segment#2

Segment#? Segment#3

Segment#4

Sequential Centric

Figure 6-121. Allocation of acquisition data comparison for the Echo Alloc. methods.

6. 71

0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet

Note: When a gating procedure is started with Beat Rejection set to ON, use the value displayed in the WaveForm window (the patient's heart rate) to enter in the Beat Rate box (in the Gating section of the ScanParameterList window), and don't excessively narrow the range of the regular beat.

Note: When a gating procedure is started with Beat Rejection set to ON and 16 consecutive irregular heart beats are recorded, Beat Rejection is automatically switched to off.

6-72

Echo Shift-Allows the number of echo shifts to be entered. The range is

dependent on the number of segments. Figure 6- 122 shows the implementation

of echo shifts .

Phase encoding direction

Segment#1 Segment#2 Segment#3

Segment#6

Segment#1

Segment#2 j Segment#3

Segment#2

Segment#1

Segment#3

Segment#3

Segment#2 Segment#4 Segment#3 Segment#1 Segment#1 Segment#5 Segment#4 Segment#2 Segment#1 Segment#6 Segment#5 Segment#3 Segment#2

Sequential/shift: 0 Sequential/shift: 1 Centric/shiift: 0 Centric/shift: 1

Figure 6-122. An Echo Shift illustration.

Beat Rejection-An irregular hea11 rhythm or pulse (arrhythmia) can cause

image quality deterioration when Gating is MS-ECG or Cine. Beat Rejection

eliminates data acquired when arrhythmia occurs. Choose from the fo llowing

options:

• off-Data acquired when arrhythmia occurs is not eliminated.

• ON- Data acquired when arrhythmia occurs is eliminated. When Beat

Rejection is ON, Skip Beat, L level[%], and H level[%] are accessible.

A Caution The beat rejection function is not effective for patients that suffer from

arrhythmia due to cardiac disease.

Skip Beat -Specifies the number of normal beats sk ipped after an arrhythmia.

L level[% j- Enter the shortest regular hea11beat cycle (as a percentage of the

regular heartbeat cycle). The regular heartbeat cycle corresponds to the R-R

interval, which the system calculates based on Beat Rate.

H levei[%]- Enter the longest regular heartbeat cycle (as a percentage ofthe

regular heartbeat cycle). The regular heartbeat cycle corresponds to the R-R

interval, which the system calculates based on Beat Rate.

Summary of Gating Parameters

The following table provides a summary of scan conditions and the various

parameters that are available when Gating is MS-ECG, Cine or Resp, and

instructions for how the parameters should be set.


Scan Parameters 0 Parameters When the Gating parameter is:

Available MS-ECG C ine R esp

Beat Rate Enter the heart rate Enter the heart rate Enter the respiratory rate

Indicates reserve hea1t rate; # HB Prep Unavailable range is 0 to 2. Gate Mode Unavailable

must be set to Delayed1•

Gating Specify ECG or Pulse Specify ECG or Pulse Resp

Source

Gate Mode Specify Trigger, Gate, Specify Trigger, Gate,

Unavailable Delayed 1, or MyoPer1

• Delayed 1, or MyoPet·1•

Resp Mode Unava ilable Unavailable Trigger

Indicates the number of R Indicates the number of R Indicates the number of

Count waves; I is set if Gate Mode waves; I is set if Gate Mode respiratory cycles

is Gate. is Gate.

Indicates the number of Multi Phase Unavailable images at same position, but Unavailable

differing heart phases.

Enter a number if Gate Mode Enter a number if Gate Mode is: is: •Gate •Gate

OR OR

Segment •Trigger, with Sequence •Trigger, with Sequence

Unavailable set to BASG, SARGE, or set to BASG, SARGE, or RSSG RSSG

OR OR • Delayed 1, with Sequence set • Delayed 1, with Sequence set to BASG to BASG

Delay Mode Unavailable Unavailable Select Time (ms) or Rate(%)

Delay[ms] Indicates time from trigger Indicates time from trigger l t~dicates time from trigger signal to initial slice TE signal to initial slice TE s ignal to initial s lice TE

Enter rate(%) of breathing Delay(%) Unava ilable Unavailable cycle from trigger signal to

TE of initia l slice

Tntet-val Indicates scan time interval Indicates scan time interval lt1dicates scan time interval for each slice or phase for each slice or phase for each s lice or phase

Echo Alloc.- Choose from: Choose from: Gate Mode •Sequential • Sequential must be Gate OR OR

Unavailable (or Trigger •Centric (with SARGE, •Centric (with SARGE, with BASG RSSG, BASG, TOF, PC, or RSSG, BASG , TOF, PC, or sequence) RSSG EPI) RSSG EPI)

Beat Unavailable

Select off or ON. If ON, enter Unavailable

Rejection a Skip Beat value.

1 Available with CardioSuite.

OS4-53287v4 6. 73

0AS/S~ MRI System RefeTence Manual n.. Pau ... .._

Parameters Available

Skip .Beat

L level[%]

H level[%]

Note:

When the Gating parameter is:

MS-ECG Cine Resp

Specifies the number of Unavailable normal beats skipped after an Unavailable

arrhythmia.

Sets a measurable range for Sets a measurable range for Sets a measurable range for trigger intervals when the beat trigger intervals when the beat trigger intervals when the beat parameter is off. When .Beat parameter is off. When Beat parameter is off. When .Beat Rejection is ON, sets the R-R Rejection is ON, sets the R-R Rejection is ON, sets the R-R interval ratio for the shortest interval ratio for the shor1est interval ratio for the shortest regular heartbeat cycle. regular heartbeat cycle. regular heartbeat cycle.

Sets the R-R interval ratio for

Unavailable the longest regular heartbeat.

Unavai lable Use when .Beat Rejection is ON.

NAVI

The NaviPulse (navigator acqu isition function) is an optional function used to

reduce scann ing artifacts in regions (such as the heart) where the position is

moved by breathing.

Navigator echo position and main scan region must be kept apart.

With this function , breathing movement is monitored by acquiring an additional

echo, called a navigator echo, from the region perpendicular to the diaphragm.

Using the monitored change in the position of the diaphragm, scann ing

is performed with the patient " free-breathing." The slice position can be

adjusted according to the displacement observed from the monitored breathing

movement.

6. 74

Figure 6-123 shows how the NaviPulse function works.

Head

[ Feet

Heart ... ·· This scan plane

~~~~·· ····· · · · ·· · · ·· ······· ····· · ···· r ~$~~~· ........ .... Diaphragm F I Breath gating for this scan I

i ··.. Acquisition position

for navigator echo --- I Monitoring breath movement I

Figure 6-123. NaviPulse illustration.


Q54-53287v4

Scan Parameters 0 The Navi section of the ScanParameterList window (figure 6- 124), contains


Figure 6-124. The Navi section of the ScanParameterList window.

NaviPulse- Provides the fo llowing options, as shown in figure 6-125:

• off- Does not perform navigator acquisition.

• NaviGate- Performs navigator acquis ition.

• SlicePos- Available only when Sequence is BASG, performs navigator

acquisition and adjusts the slice position to compensate for s lice variation due

to respiratory movement.

off

off NavtGate Sl1cePos

Figure 6-125. NaviPulse options.

GateWiodow- lndicates the gate window width in millimeters. The

acquisition data is effective only when the position of the diaphragm is in the

gate window prescribed by this width. The default (initial value) is 3 mm.

Data Number - Indicates the number of acquis ition points for the navigator

data. The selection can be 64, 128, or 256 points, as shown in figure 6-1 26 .

•••• ,.,_64;,;_ ___ --r 64 128 256

Figure 6-126. Data Number options.

CorrCoeff-Available when NaviPulse is SlicePos. CorrCoeff sets the ratio

of variation in sl ice position (due to respiratory movement) to the value of the

position adjustment. For example, if the respiratory movement detected by the

navigator monitor is I Omm and the CorrCoeff is set to 0.6, the slice is adjusted

by6mm.

6. 75


6-76

NaviMonitor - Indicates the method for the NaviMonitor acquisition during

the prescan. Choose from the following options, as shown in figure 6-127:

• ON-NaviMonitor acquisition is always performed prior to an acquisition.

• Auto-In cases where the monitor acquisition has been performed for the same

acquisition, the system decides if the data is usable or not. If it is usable, the

acquisition will start without the petformance of a monitor acquisition during

the prescan. If it is not usable, a NaviMonitor acquisition will be perfonned.

Figure 6-127. NaviMonitor options.

Monitor Time-Indicates the time for the NaviMonitor acquisition.

PAPE Partial Phase Encode (PAPE) is an optional function used to improve temporal

resolution while maintaining the spatial resolution of the image.

The PAPE section of the ScanParameterList window (figure 6- 128) contains

the following parameters:

PAPE ljj ON

e;;.iil.;; lr-oo-·-17_3_~..,,

Wj,jj§ [s ! ... "': ' 11!fiDIM[4o I I- '

L-....,--~

*!·*'! 8

F;gure 6-128. The PAPE section of the ScanParameterList window.

PAPE - Provides the following options:

• off- PAPE is off.

• ON- PAPE is on.

PAPE can be set to ON when Multi scan mode is Dynamic or Fluoro, and one

of the following combinations are selected from the 2D/3D and Sequence lists:

• 2D and SARGE

• 2D and BASG

• 2D and TRSG

• 2D and RSSG

• 3D and RSSG

Scan Time-Displays time, but is unavailable. This is the time needed to perform the acquisition, while ignoring the K-space high frequency waves.


Note: It is recommended to set Data Rate[%] higher when scanning a region with movement.

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Scan Parameters 0 Segment- Indicates the number of segments to be partitioned for K-space. As

the number of segments increases, the scan time per image becomes shorter,

but the update interval for high frequency data becomes longer. The selections

include 3, 5, 7, or 9.

Data Ra teJ% 1- lndicates the ratio for low-frequency data that will definitely

be measured(%). As this rate is increased, image quality improves but temporal

resolution degrades. The range is from I 0 to 60 percent, in five percent

increments.

Scan Cycle- Displays the number of cycles. Scan Cycle is set automatically

and remains at one number lower than the setting for Segment. Scan Cycle

options include: 2, 4, 6, orR.

Filter/PostProcessing

The F ilter/PostProcessing section of the ScanParameterList window conta ins


Ot·g.Jmage- Specifies whether or not to reconstruct original images. Org.

Image is available when Sequence is PC (Phase Contrast). Choose from the

following options, as shown in figure 6- 129:

• off- Does not reconstruct original images.

• ON- Reconstructs original images.

l6aPI!Miii •• l~~-~-------f·l1

Figure 6·129. Org.lmage options.

Calc.Image- Specifies whether or not to create differential images for scanned

images. Depending on sequence selected and imaging conditions, the Calc.

Image options might not be available, might be set automatically, or may not

even be displayed. Available options are:

• off- Does not create differential images.

• Sub-Creates differential images.

6. 77


6-78

Image Type-Specifies the type of images to be displayed. Image Type may

be available, or may be set automatically (unavailable), depending on the option

selected from the Sequence list.

The following options are available when Sequence is IR or FIR (figure 6- 130):

• Abs- Displays absolute value images.

• Real- Displays Real images.

••+ 1'-A_b.:....s ----t Abs Real

Figure 6-130. Image Type options.

The following option is automatically set when Sequence is Shim (figure 6-13 I):

• Phase- Displays Phase images.

QM·i· Phase

Figure 6-131. Image Type option when Sequence is Shim.

RawData Save-Available to Hitachi fie ld serv ice engineers. Specifies whether

or not to save the raw data to the database before image reconstruction. As


• off- Does not save raw data to the database.

• ON -Saves raw data to the database.

ptD@Moff off ON

Figure 6-132. RawData Save options.

Truncation - Filtering that can be used to reduce artifacts that may appear

when data collection conditions a llow the system to acquire fewer than the

required encoding numbers (for example, low phase encod ing settings of 128 or

160). Choose from the fol lowing options, as shown in figure 6-133:

• off - Does not use the truncation fi Iter.

• ON- Uses the truncation fi Iter. Hitachi recommends this setting for use with

T2 FSE sequences.

• Auto- Automatically uses the truncation filter according to the number of

acquisition points.

off ON Auto

Figure 6-133. Truncation options.


Note: When acquiring the S-Map data in preparation for the NATURAL option, make sure the area to be scanned is adequately covered.

Q54-53287v4

Scan Parameters 0 Shading-Filtering that corrects for signal intensity differences throughout the

image. Choose from the following options, as shown in figure 6-134:

• off- Does not use the shading con·ection filter.

• N ATURAL- Uses the shading correction with 3D sensitivity map. It is

necessary to first acquire the 3D sensitivity map using the S-Map Sequence.

• Hybrid - When used with multiple images that are scanned in the same

position (such as with Dynamic mode), the degree of correction in the first

scan is applied to later scans. When used with multiple images that are not

scanned in the same pos ition (such as 3D scans), the degree of correction is

kept constant along the sl ice direction.

• Manual - Uses the shading correction filter. The Correction parameter

(described next in this section) will be displayed.

off NATURAL Hybnd Manual

Figure 6-134. Shading options.

Correction - indicates the intensity of the shading correction. The higher the

value, the stronger the correction will be. Correction is available when Shading

is NATURAL, Hybrid or Manual. The options range from Typel to TypeS

when Shading is Hybrid or Manual. The options are off, Typel or Type2

when Shading is NATURAL (figure 6-1 35) .

*M5!Fi' Type1

Type I Type2 Type3 Type4 T e5

(a)

........

(b)

off off Type1 T e2

Figure 6-135. Correction options when Shading is (a) Hybrid or Manual and (b) NATURAL.

T2 correct.-Corrects for T2 decay that occurs with long echo train sequences.

The options are shown in figure 6-1 36.

I~EE .. iil4iilllll~to_ff ______ ~~~1 off Manual

Figure 6-136. T2 correct. options.

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6-80

Levei[% ]- Sets the level of the T2 Amp litude Correction Filter. The larger the

value, the stronger the correction. Level[%] is avai table when T2 correct. is

Manual (figure 6-137).

Figure 6-137. Level[%} and T2 Target parameters.

T2 Target- Sets the T2 value for the T2 ampl itude correction area. T2 Target

is available when T2 correct. is Manual (figure 6-137). T2 Target should be

set to match the TE value.

Adaptive F ilter - Performs fi lter processing for the scanned image (figure

6- 138). For more adaptive filter infonnation, refer to the "Review Task

Window" section of Chapter 7, "Review and Filming Functions".

BM¥11§ off ~ I '

off Sm1Sh0 Sm1Sh1 Sm1Sh2 Sm2Sh0 Sm2Sh1 Sm2Sh2 Sm3Sh0 Sm3Sh1 Sm3Sh2 Sm4Sh0 Sm4Sh1 Sm4Sh2 Min Med Max MRAMin MRAMax

Figure 6-138. Adaptive Filter options.

Edge enhance- Performs edge enhancement for the scanned image. For more

edge enhancement infom1ation , refer to the "Review Task Window" section of

Chapter 7, "Review and Filming Functions" .

MIP Image-Specifi es whether or not to create MIP reference images

automatically after the scan is finished. Choose from the following options, as

shown in figure 6-1 39:

• off- Does not create MIP reference images.

• ON-Creates MIP reference images automatically after the scan is finished.

Figure 6-139. MIP Image options.


Note: When Diffusion Analysis is ON, the DW EPI sequence is vulnerable to magnetic field distortion. If homogeneity of the magnetic field is poor image degradation and artifacts may occur. To reduce this effect be sure to carry out volume shimming before starting Diffusion Tensor Imaging.

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Scan Parameters 0 When MIP Image is O N, the following parameters become available:

MJP Edge E nh.-Adjusts the quality of the MlP refe rence images that are

created. The adjustment range is from -5 to 5. The image smoothness increases

as it approaches - 5, and the image sharpness increases as it approaches 5.

MIP Dir. - Selects the view direction of MJP reference images. Choose from

the fo llowing options, as shown in figure 6-140:

• front- Creates MlP reference images viewed from the same direction as the

direction set in Slice P lane.

• AX- Creates MIP reference images viewed from the axial direction.

• COR-Creates MIP reference images viewed from the coronal direction.

• SAG - Creates MIP reference images viewed from the sagittal direction.

• SA- Creates MJP reference images viewed from the sagittal and axial directions.

• CA- Creates MI P reference images viewed from the coronal and axial directions.

• SC-Creates MIP reference images viewed from the sagittal and coronal directions.

• SCA- Creates MIP reference images viewed from the sagittal, coronal, and

axial directions.

IMF! lAX front

·t AX COR SAG SA CA sc SCA

Figure 6-140. MIP Dir. options.

For more information about MIP reference images, refer to the "Task MIP''

section of Chapter 8, "Post-Processing Functions."

Diffusion Analysis - Specifies whether or not to create di ffus ion analysis

images automatically after the scan is finished. Diffusion Analysis is available

only when Sequence is DW EPI. Choose from the following options:

• off- Does not create diffus ion analysis images automatically.

• ON - Creates diffusion analysis images automatically after the scan is

fin ished.

When Diffusion Analysis is ON, the fo llowing parameters become ava ilable:

ADC-Avai lable when MPG Dir# is Single or T race. If Single is selected,

ADC defaults to ON. If Trace is selected, the following options become

available:

• off- ADC images are not created automatica lly after scanning.

• ON- ADC images are created automatically after scanning.

6. 81


Note: The b-factor value summarizes the influence of the gradients in OWl. The higher the b-factor value, the stronger the diffusion weighting. Hitachi recommends a b-factor of 1000.

6-82

DWI tr ace-Available when MPG Dir# is Trace, Tensor6, Tensor7,

Tensor13, or Tenso r21 (optional). Choose from the following options, as shown

in figure 6= 141:

• off- OWl trace images are not created automatically after scanning.

• ON (with bO) - DWI trace images are created automatically after scanning,

inc luding bO image.

• ON (without bO) - OWl images are created automatical ly after scanning,

without bO images .

ON(without bO) •

off ON(with bO) ON(without bO)

Figure 6-141. DWI trace options.

FA ( Fractional Anisotropy)- (Associated with the Diffusion TensorSuite,

wh ich is a purchasable option.) Avai lable when MPG Dir# is Tensor6,

Tensor7, Tensor13, or Tensor21. Calculates an index FA showing the

anisotropy of diffus ion from the obtained diffusio11 tensor, and creates an FA

map reflecting an FA value. The options are;

• off- FA images are not created automatically after scanning.

• ON -FA images are created autonnatically after scanning.

MD (Mean Diffusibi lity)-(Associated with the Diffusion TensorSuite, which

is a purchasable option.) Available when MPG Dir# is Tensor6, Tensor7,

Tensor-13, or Tenso r·21 . Calculates the mean of the intrinsic values of

diffusibility and creates an image reflecting the MD. The options are:

• off- MD images are not created automatically after scann ing.

• ON-MD images are created automatically after scanning.

Figure 6-142 shows the FA and MD parameters .

. ,. '%3

Figure 6-142. FA and MD parameters.

Save Corr.Image- When Save Corr.Image is ON, the original images and the

distortion-corrected images are saved in the system database. When Save Corr.

Image is off, the corrected images are not created automatically after scanning.

Noise Threshold - Indicates a threshold value to eliminate background noise.

The range is 0 to l 00; increasing the value eliminates more noise.


Note: Distortion correction settings will vaty depeflding on the body part being scanned.

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Scan Parameters 0 Correct Distortion-Specifies whether or not to correct distortion of the input

image. The options a re:

• off- Image distortion is not corrected for the FA map, MD map, and DWI

Trace images.

• ON - Image distortion is corrected for the FA map, MD map, and DWI Trace

images.

D.C.Levei- Corrects image distortion generated by nonlinearity in the gradient

magnetic field. The options are:

• off- Image distort ion is not corrected.

• Auto - The system applies distortion correction as needed.

• GC- (Gradient Correction) Distortion correction is a lways applied.

When D.C.Level is Auto or GC, Region Cut is displayed.

Region Cut- Regions that cannot be corrected by the distortion correction

function may appear on the edge of the image. Region Cut options (as fo llows)

determine whether or not the uncorrected regions are cut from the image:

• off- The regions are not cut from the image. This is the recommended option

when scanning la rge anatomical regions (such as large abdomens), to ensure

that a ll of the anatomy of interest is included.

• Auto - T he regions are cut from the image when there are regions that cannot

be corrected by the distortion correction function.

W-Widtbl - Indicates the window width of the display for one echo. The set

value becomes the default wi ndow width for displaying images. After an image

is displayed, the wi ndow width can be changed.

W-Levell - lndicates the window level of the display for one echo. The set

value becomes the default window level for displaying images. After an image

is displayed, the window level can be changed.

W-Width2- Available when Multi Echo (in the Seq. Parameter area) is 2 or

greater. Indicates the window width of the display for two echoes. This value

becomes the default window width for displaying images. After an image is

displayed, the window width can be changed.

W-Levei2 - Available when Multi Echo (in the Seq. Parameter area) is 2 or

greater. Indicates the window level of the display for two echoes. Th is value

becomes the default window level for displaying images. After an image is

displayed, the window level can be changed.

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6-84

Figure 6-143 shows the window width and level parameters.

p¥111

••• JWIIf

Figure 6-143. Window width and window level parameters.

Positioning

Positioning parameters allow you to select various options involved with the

scanning and viewing of images.

The Positioning section ofthe ScanParameterList window (figure 6-144)


H-F

S-C-A

off

Lme

ON

off

Figure 6-144. The Positioning section of the ScanParameterList window.

Slice Ord. A -Specifies the direction in which the axial plane slices wi ll be

scanned and displayed. Choose from the following options, as shown in figure

6-145:

• H-F - From head to feet

• F-H -From feet to head

i§Hilijf H-F f--H---F-------1

F-H

Figure 6-145. Slice Ord. A options.


Note: Plane Order cannot be changed, but the slice order within a plane can be.

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Scan Parameters 0 Slice Ord. S-Specifies the direction in which the sagittal plane slices will be

scanned and displayed. Choose from the following options, as shown in figure 6-1 46:

• R-L- From right to left

• L-R- From left to right

l.i.Efllflii¥41111~(R_·L~----~~J I ~-~ I

Figure 6-146. Slice Ord. S options.

Slice Ord. C-Specifies the direction in which the coronal plane s lices will be

scanned and displayed. Choose from the following options, as shown in figure

6-147:

• A-P- From anterior to posterior

• P-A- From posterior to anterior

I ~p ~I P-A _

Figure 6-14 7. Slice Ord. C options.

Plane Order - Displays the scanning order of the s lice planes. Plane Order is

for display only, it cannot be changed.

The following planes are available for display:

• AX- Axial plane

• SAG -Sagittal plane

• COR-Coronal plane

• S-A- Sagittal plane, axial plane

• S-C- Sagittal plane, coronal plane

• C-A- Coronal plane, axial plane

• S-C-A- Sagittal pane, coronal plane, axial plane

Figure 6- I 48 shows a Plane O rder of S-C-A.

l§llh9@ S-C-A

Figure 6-148. The Plane Order parameter.

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6-86

Radial Stack-Allows easier radial slice stack positioning for MRCP

exams. When Radial Stack is ON, the radial stacks move as a group, making

posit ioning at a central point easier.

To use radial stack positioning, make sure Radial Stack is ON, then enter the

number of radial stacks to be performed in the Stacks box (located in the Seq.

Parameter area of the ScanParameterList window).

Slice Allocation- [ndicates the order of slice excitation for multi-slice

scanning. Slice Allocation is available when:

• 2D/3D is 2D

• Sequence is GE, SARGE, or RSSG

• The Mode parameter of Multi Acquisition is Interleaved

As shown in figure 6-149, Slice Allocation options include:

• Default- Scans from one side of the sl ices to the other side.

• Convergence-Scans from both sides of the s lices towards the center.

[Qff4idliii!MI--'o::..::e.;..:cfau::..::k __ --t Oefauk Convergence

Figure 6-149. Slice Allocation options.

Line/Box- Specifies the manner in which 2D imaging slice lines appear when

they are displayed in the viewp01ts for positioning. Line/Box is not displayed

when 3D is selected from the 2D/3D box. The following options are available,

as shown in figure 6-150:

• Line- Displays the slice surface as a line.

• Box-Displays the sl ice surface as a box.

line Bo:<

Figure 6-150. LineiBox options.


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Scan Parameters 0 Guide L ine -Specifies whether or not guidelines w ill appear when changing

s lice position or number of slices. Guide lines are the dotted lines displayed at

the top and bottom of the slice group. The fo llowing options are available:

• Yes- The dotted lines are longer than the s lice lines and continue to be

displayed when s lices are moved. Figure 6- 151 shows the results when Guide

Line is Yes.

Figure 6-151. The Guide Line parameter set to Yes.

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0AS Is~ MRI System Reference Manual 11141 htlet~t olllqHt

6-88

• No- The dotted lines are approximately the same length as the slice lines and

are displayed around the outer edges of the slice group. The dotted lines will

elongate and display during slice movement. Figure 6-152 shows the results

when Guide Line is No.

Figure 6-152. The Guide Line parameter set to No.

G.Intvl -Specifies whether or not the slice interval can be changed for each

slice stack or slab group for scans that involve multiple stacks or slabs. The

following options are available, as shown in figures 6-153 and 6-154:

• off- The slice interval for each slice or slab group can be changed. When

G.Intvl is off, the Interval box is displayed in the Scan Positioning

Information bar at the bottom of the Task View area. Figure 6- I 53 shows the

G.Intvl parameter set to off.

~~I'IMIIIIIII ~lo~ff--------~·1

Figure 6-153. G.lntvl set to off.


Q54-53287v4

Scan Parameters 0 • ON - The slice intervals for each slice or slab group are set to the same value

and cannot be changed individually. When G.lntvl is ON, Interval is

displayed in the Seq. Parameter area of the ScanParameterList wi ndow.

Figure 6-154 shows the G.Intvl parameter set to ON .

•• I ON

Figure 6-154. G.lntvl set to ON.

Sync.- Specifies whether to simultaneously change all plane settings when the

settings for pos ition, angle, and slice number are changed, and multiple planes

have been selected. Sync. is available only when Slice P lane is SA, SC, CA, or

SCA. Choose from the fo llowing options, as shown in figure 6-155:

• off- Does not change the settings of all planes.

• ON -Changes the settings of all planes.

Others

1*!1 -off

off ON

Figure 6-155. Sync. options.

The Others section of the ScanPa ra meterList window contains the fo llowing

parameters:

Receiver Coil-Select the receiver coil name from the list of connectab le

receiver coils, as shown in figu re 6-156. If Receiver Coil is Auto, the receiver

coil name is recognized automatically.

~4¥-YIMif¥1111 111~~--o ______ ·~J, Auto CTL LargeJomt PI/ QD Flex Body(L) QD Flex Body(Xl.) QOHead RAPID Body RAPID Breast RAPID C.Sp1ne RAPID Foot RAPID Head RAPID Knee RAPID I# RAPID Shoulder RAPID Wrist TRBo

Figure 6-156. Receiver Coil options.

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6-90

Mod e-Specifies the receiver coil mode for multi-mode coils, such as the CT L

and RAPID Foot co ils. A mode can be selected from the Mode list that is

available for the receiver coil chosen from the Receiver Coil list , as shown in

figure 6-1 57.

RAPID Foot

Bil Ext Full

811 Ext Full Bil Ext Full Lt Bil Ext Full Rt Bil Ext Foot Bil Ext Foot U Bil Ext Foot Rt


If Receiver Coil is Auto, Mode changes to Auto, as shown in figure 6-158. T he

system will set the most common mode for the receiver coil that is being used.

Figure 6-158. Mode is Auto when Receiver Coil is Auto.

MorningQA- Specifies checks to be performed during the morning quality

assurance (QA) procedure. When starting the system, scanning is performed

with fixed parameters to confi rm that the system is operating correctly. All

parameters that a re current ly set are disabled, and the fi xed parameters are set.

Choose from the fo llowing options, as shown in figure 6-1 59:

• off- Does not perform MorningQA.

• GC Check - FlO-Acquires the FID (free induction decay) signal.

• GC C heck - X- Checks X-axis gradient movement.

• GC Check - Y -Checks Y-axis gradient movement.

• GC C heck - Z-Checks Z-axis gradient movement.

• Coil Check-Checks each cham1el of t he coil.

1$1,jl.i!,l,lf off

off GC Check- FlO GCCheck-X GCCheck- Y GCCheck- Z Coil Check

Figure 6-159. Morning QA options.


Note: The TIGRE measurement sequence is a fat-suppression imaging method using a fatsat pulse. To obtain the high fatsuppression effect. homogeneity of the static magnetid field is important. Therefore, be sure to carry out volume shmming prior to performing TIGRE sequence scan Utilizing the regional shimming function (available as an option) together with volume shim data can provide consistent fat suppression.

Note: With a 30 acquistion, the SNR of the images at the top and bottom edges of the slab is lower compared to that at the center region. Therefore, position the region of interest at the center of the slab and set the number of slice encodes to a slightly higher value.

Note: Hitachi recommends Circular 30 Acq. Mode with TPEAKS Echo Alloc. for all TIGRE acquisitions.

Q54-53287v4

Scan Parameters 0 Soft Sound - Specifies the Soft Sound mode, which decreases the noise level

for certa in pu lse sequences. Activation of the Soft Sound mode requires an

increase in TR, and, consequently, an increase in scan time. Choose from the

fo llowing options, as shown in figure 6-160:

• ofT - Acquisition is not performed in Soft Sound mode.

• ON-Acquisition is perfom1ed in Soft Sound mode.

M!Fiiii!i!

Figure 6-160. Soft Sound options.

TIGRE

The TIGRE sequence is a 30 fast, T l-weighted, RF-spoiled SARGE sequence

using a fatsat pulse. Th is sequence can be used for T l-weighted, fat-suppressed,

dynamic imaging with contrast. A segmented fatsat pulse is used to maintain

fat suppress ion and provide suffic ient temporal resolution for dynamic scans.

Shimming must be performed before the TTGRE acquisition.

The specific parameter selections that are required or recommended for TIGRE

are described below.

Sequence Area

Select the following:

• 20 /30 - Select 30.

• Sequence- Select RSSG.

Seq. Parameter Area

• Echo Alloc.-Select either Cent-Cent or Cent-Seq, as shown in figure

6-161:

Cent-Cent-Echo allocation for phase encode and slice encode directions

are both Centric. The #RF Prep value should be increased (as compared

to the Cent-Seq value) to suppress artifacts, even though this reduces the

effects of fat suppression.

Cent-Seq - Echo allocation for the phase encode direction is Centric,

while echo allocation for the slice encode direction is Sequentia l.

Figure 6-161. Seq. Parameter area settings.

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0ASJS~ MRI System Reference Manual T1Mthtr .. tllapet

Note: When 3D Acq. Mode is Circular, Slice# and Segment may be restricted.

Note: If Segment is set to an extremetly large value, longitudinal magnetization of fat is recovered and the fat suppression effect may be reduced.

6-92

• 3D Acq. Mode- When Circular is selected, Echo Alloc. is TPEAKS and the

outer corners of K-space are not acquired, which reduces scan time.

Advanced Area

For #RF P rep, Hita·chi recommends using a value of about 5 when Echo Alloc. is Cent-Seq, or a value higher than that when Echo Alloc. is Cent-Cent. This

va lue represents the number of dummy RF pulses needed to maintain the steady

state afte1· the application of the segmented fatsat pulse. Larger lilllmbers may

improve artifact suppression but a lso reduce the effect of fat suppression.

Saturation Area

Select the following, as shown in figure 6-162:

• Saturation-Select Segment FS.

• Wave- Select H-Sinc.

• RF amp.[%] -Enter 100.

• Segment- Hitachi recommends a value of about 32.

Figure 6-162. Saturation area settings.


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