3/12/2010 - Indiana University Bloomingtonmri/seminars/slides/Basic Neuro and Ortho MRI... ·...
Transcript of 3/12/2010 - Indiana University Bloomingtonmri/seminars/slides/Basic Neuro and Ortho MRI... ·...
3/12/2010
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MRI Techniques for Neuro and MSK Imaging
Chen Lin, PhD
Indiana University School of Medicine & Clarian Health Partners
Declaration of Conflict of Interest or Relationship
Research support from Siemens Healthcare
Chen Lin, PhD 3/2010
Typical Neuro Protocols
Routine Brain
• LOC 3PL
• SAG T1 SE
• SAG T2 FLAIR
• AX T2 FLAIR
• AX T1 SE
• AX T2 TSE FS +C
• AX DW EPI +C
• AX T1 3D IRSPGR +C
• COR T1 SE FS +C
• SAG T1 SE +C OPT
• AX T1 SE +C OPT
Routine Spine
• LOC 3PL
• SAG COR LOC
• SAG T1 TSE
• SAG STIR
• AX T1 TSE
• SAG T2 TSE +C (3D)
• Sag T1 TSE FS +C
• AX T1 TSE +C
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Typical Ortho Protocols
Routine Knee
• AX LOC
• SAG COR LOC
• AX T2 TSE FS
• AX GRE
• SAG PD TSE
• SAG T2 TSE
• COR PD TSE
• COR STIR
• OCOR T2 ACL
• OSAG T2 ACL
Routine Shoulder
• AX LOC
• SAG COR LOC
• AX PD TSE FS
• AX GRE
• COR PD TSE
• SAG PD TSE
• COR MOD IR
• SAG T2 TSE FS
• SAG T2 TSE
• COR T2 TSE
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Outlines
• Conventional Spin Echo (CSE)
• Fast Spin Echo (FSE / TSE)
– 2D and 3D Fast Spin Echo (SPACE, CUBE)
× Single Shot Fast Spin echo (SSFSE, HASTE)
• Multi Contrast Spin Echo (T2 Mapping)
• Inversion Recovery (IR)
– FLAIR
– T1-FLAIR
– IR-FSE
– IR-SPGR / MP-RAGE
– Phase Sensitive ReconChen Lin PhD 3/2010
The Structure of MR Pulse SequencesMagnetization Preparation Section• Chemical Shift Selective Saturation / Excitation• Spatial Selective Saturation• Magnetization Transfer (MT), CHESS water suppression• Inversion Recovery (IR)
Data Acquisition Section• Slice/Slab Selective Excitation• Phase Encoding(s)• Signal Generation
• Spin Echo (SE), Fast SE (FSE/TSE), Single-shot FSE (SSFSE/HASTE)• Gradient Recalled Echo (GRE), Single-shot GRE (EPI)
• Diffusion Weighting (DWI/DTI) and Gradient Moment Nulling (GMN)• Frequency Encoding• Filling of K-space
Magnetization Recovery Section• Spoiling• Driven Equilibrium
Increment Phase
Encoding
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Conventional Spin Echo
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TE/2TE/2
Excitation Refocusing
Phase Encoding
Frequency Encoding
TRNext Excitation
rBW–Min. FOV–Chem. Shift–Distortion–SNR
Signal and Contrast of CSE
Max. signal when:
Excitation = 900
Refocusing = 1800
When TR>>TE:
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Short TR / Greater T1 Contrast
Long TE / Greater T2 contrast
PD
T1 ?
T2
Low SNR !
/ 1 / 2
0 (1 )TR T TE TS M e e
More Efficient Use of MR Signal
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t
900 x 1800 +y
SE
B1 / Mxy
FID
900 x 1800 +y
SEFID
TR = 400 – 4000 ms
TE = 10 – 200 ms
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Fast Spin Echo and CPMG Condition
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t
900 x
1800 +y 1800 -y 1800 +y
SE SE SE
B1 / Mxy
t 2t 2t
1. Refocusing RF pulses are 90 deg out of phase with respect to excitation RF pulse.
2. Identical spacing between refocusing RF pulses.
3. Identical phase accumulation between refocusing RF pulses.
Fast/Turbo Spin Echo Train
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Rewind
Echo Spacing
Echo Train Length (Turbo Factor)
Available TEeff in FSE/TSE
Echo Train Length = ? & Echo Spacing = ?Chen Lin PhD 3/2010
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RARE, FSE/TSE Sequence
t
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Short TEEffective Long TEEffective
B1 / Mxy
t 2t 2t
FSE/TSE Artifact
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CSE TE=30ms TSE ETL=30 EP=10ms TE=30ms
TSE ETL=30 EP=10msTE=130ms
ky
I
ky
I
ky
I
T2 Blurring and Edge Ringing
ky
kx
ky Y
II
Multi-shot FSE/TSE
I-space Point Spread Function
FT
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K-space Intensity Profile
Blurring
Ringing/Ghosting
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CSE FSE CSE FSE
FSE/TSE versus CSE
MT Effect
PD T2
Contrast
DifferenceBright FatChen Lin PhD 3/2010
T1 SE vs TSE of Hip Joint
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rBW = 485Hz/pix, ETL=5rBW = 485Hz/pix, ETL=1
Bright Fat with due to J-coupling
Lipid Mxy
TE(ms)
FSE/TSE with short echo spacing
CSE
CC
H
H
H
80 160
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CSE and TSE of Knee
SE, TE 14, 14cm, 3mm,
208 x 320, 3:04
TSE, Fat Sat, TE 14, 14cm,3mm,
208 x 320, 3:55
Cou
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Cen
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Driven Equilibrium (Fast Recovery, Restore)
• Add 180y + 90-x RF pulses to refocus and flip the Mxy
back to Z axis.
• Allow shorter TR ( ~2000ms) while maintaining T2w or PDw.
t
180y 90-x
X
Z
Y
Z
Y
90x
XChen Lin PhD 3/2010
Restore Example
TSE4 min
TSE with Restore2.4 min
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Stimulated Echo & CPMG
Mxy
t
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900 x
a10 y
SE SE + STE SE + STE
a20 y a30 y
Refocusing Flip Angle (RFA) < 1800
Contrast Difference between FSE and CSE
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RFA = 1500
RFA = 1800 RFA = 1200
CSE
Contrast Difference between FSE and CSE
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200
400
600
800
1000
1200
1400
1 2 3 4 5 6 7 8 9 101112131415161718
CSE
TSE_180
TSE_150
TSE_120
1300
1500
1700
1900
2100
2300
2500
2700
1 2 3 4 5 6 7 8 9 101112131415161718
CSE
TSE_180
TSE_150
TSE_120
TR/TE/ETL=2000/86/10TR/TE/ETL=2000/8.6/10
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3D FSE, SPACE, CUBESamplingPerfection withApplication optimizedContrast using different flip angleEvolutions
3D FSE/TSE w. variable refocusing flip angle schedules:
• Constant: same as 3D TSE
• PD Variant: optimized for short TE
• T2 Variant: optimized for longer TE
Constant Refocusing Flip Angles
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T2 Var. Refocusing Flip Angles
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Variations of 3D SPACE
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T1 SPACE1 x 1 x 3 mm³
FLAIR SPACE 1 x 1 x 1 mm³
T2 SPACE 1 x 1 x 1 mm³
Isotropic Hires T2 SPC of Brain
3D SPACE, GRAPPA 2, 0.9 x 0.9 x 0.9 mm3 4:27 min
s
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3D FLAIR SPACE of Brain
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3D T2 SPACE of IAC
Acoustic Nerve
3D SPACE with 0.3 mm isotropic resolution in 6 min
3D T2 SPACE of Spine
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Reducing Susceptibility Artifact w. SPACE
2D TSE T2 MPR of 3D SPACE T2
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3D SPACE of Pelvis
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AX MPR of 3D Cor PD/T2 of Hip
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3D T1 FSE of Brain @ 3T
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3D T1 FSE of Pelvis @ 1.5T
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TR = 700ms TR = 553ms
3D SPACE Features
• Offers 3D imaging with isotropic resolution.
• Can be reformated to other planes or thicker 2D to improve SNR.
• Useful when multiple 2D of same contrast but different orientations are desired.
• Produces better image quality for PD and T2 than T1.
• Reduces SAR @ 3T.
• Helps minimize artifact from susceptibility.
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Multi Contrast Spin Echo
t
Mxy (TEn) = M0 exp(-TEn/T2)
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TE3TE2TE1
B1 / Mxy
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Cell
Water/
mobile
ions
GAG
+
-
++
++
+
+
+ +
+
+
+
+
+
++
-
- -
-
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-
-
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--
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Morphology
Collagen
Biochemical Composure
Cartilage T2 Mapping
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T2 Mapping of MCPJ for JRA
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11.5ms 23ms 34.5ms 46.0ms
57.5ms 69.0ms 80.5ms T2 MapT2 Map
RF
GS
ADC
GR
GP
180°
M0
Inversion Recovery
Tissue magnetization
Magnetization Preparation by IR
90° 180° 180° 180° 180° 180° 180°
Acquisition
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Variations of IR Technique
Inversion Options:
• Non-selective
• Slice-selective
• Spectral selective
• Adiabatic
• Flow-induced Adiabatic
• Combination of multiple inversions
Acquisition Options:
• Unlimited (TSE and TFL are common)
• 2D and 3D
• View ordering and correction of k-space modulation can be important.
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Applications of IR
• Selectively suppress tissue / background signal based on T1 differences– STIR, SPIR, SPAIR– FLAIR
• Improve T1 contrast (Phase Sensitive Recon)– MP-RAGE, IR-SPGR, IR-TFE– T1FLAIR– T1IR
• T1 Measurement / T1 Mapping• Tagging / Labeling
– Arterial Spin Labeling (ASL)
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T1 of Various Tissue Types
Tissue T1 @ 1.5T (msec)
T1 @ 3.0T (msec)
CSF 4400 4500
WM 780 850
GM 920 1330
Blood 1200 1500
Muscle 870 1160
Fat 220 260
TInull = 0.69 x T1
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STIR, FLAIR, TI and TINull
STIR: Short Tau Inversion Recovery, TRIM
FLAIR: FLuid Attenuated Inversion Recovery, “Dark Fluid”
TInull (Water)
Fat signal
Fluid signal
Inversion RF Pulse
Signal
TInull(Fat)
Time
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Interleave of Inversion & Acquisition
ACQ4
IR1
ACQ5
IR2
ACQ1
IR3
ACQ2
IR4
ACQ3
IR5
TI
ACQ1
IR1
TI
ACQ1
IR1
ACQ2
IR2
ACQ3
IR3
ACQ4
IR4
ACQ5
IR5
TI
IR2 IR3 IR4 IR5
ACQ2 ACQ3 ACQ4 ACQ5
STIR
FLAIR
T1IR
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FLAIR Optimization
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TI=2250ms TI=2500ms TI=2700ms
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From FLAIR to T1FLAIR
SignalLong TI and TRShort TI and TR
T1-weighted FLuid-Attenuated Inversion Recovery (T1FLAIR)
• Axial T1 FLAIR @ 3T with TR/TE/TI/ETL = 2100/9.5/900/3
• Improves T1 contrast at 3.0T
• High SAR limits number of slices and coverage
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T1 FLAIR of Spine
• Use shorter TR and TI than FLAIR (Modified FLAIR)• Suppress CSF and provides good T1 contrast
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Faster HR→ Shorter RR→ Less Recovery → Shorter TI
TI
TI
Adjust TI according to TR
Lock TI and TR for Tissue Suppression
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Double IR for Brain
Dark Fluid Dark Fluid & Dark WM
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Better Lesion Detection with DIR
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Watt
jes M
P e
t al A
JN
R 2
007 2
8(1
):54
MP-RAGE, IR-SPGR
Either with Inversion Recovery or Saturation Recovery
Chen Lin, PhD 11/09
TI
Mz
IR
SPGR
MP-RAGE versus MP-EFGRE @ 3.0T
MP-RAGE 9:14 MP-EFGRE 6:30
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T1-weighted Imaging for Brain @ 3.0T
2D SE 60 2D T1 FLAIR 2D FLASH 3D FLASH 3D MPRAGE
IQ=4 IQ=6 IQ=4 IQ=5 IQ=5
IQ: The median perceived overall image quality
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Po
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03
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IR with Phase Sensitive (PS) Recon
Inversion
Signal
Time
Blood
Myocardium
True IR (Real IR) for Brain
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PS T1IR
PS T1IR T1SE T2 FLAIR
Ho
u e
t al
. AJN
R 2
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5 2
6 (
6):
14
32
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Phase Sensitive Reconstruction
• An image reconstruction option, no additional scan time
• Improve contrast
• May produce artifact.
Ask for both magnitude recon and PS recon images.
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Look-Locker IR for T1 mapping
Kim
elm
anT
et a
l. In
vest
Rad
iol.
20
06
Feb
;41
(2):
19
8
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Summary
• Main characteristics of spin echo pulse sequence.
• Variations of spin echo pulse sequence and their applications for Neuro and Ortho imaging.
• Key issues for optimizing spin echo based techniques.
Chen Lin PhD 3/2010
Thank You !
www.indiana.edu/~mri