Miyaoka Summer 2006

Nuclear MedicineImaging Systems:

The Scintillation Camera

Miyaoka Summer 2006

List of Nuclear MedicineRadionuclides

• Tc99m 140.5 keV 6.03 hours• I-131 364, 637 keV 8.06 days• I-123 159 keV 13.0 hours• I-125 35 keV 60.2 days• In-111 172, 247 keV 2.81 days• Th-201 ~70, 167 keV 3.044 days• Ga-67 93, 185, 300 keV 3.25 days

From: Physics in Nuclear Medicine (Sorenson and Phelps)

Miyaoka Summer 2006

The Planar Gamma Camera

Siemens e.cam

Miyaoka Summer 2006

Gamma Camera Instrumentation

Electronicsboards

crystalLG

PMT

acquisitionand

processingcomputer

collimator

Miyaoka Summer 2006

The Scintillation Camera:Detector System

Miyaoka Summer 2006

Crystal and light guide

NaI(Tl)Density 3.67 g/cm3

Attenuation Coefficient (@140 keV) 2.64 cm-1

PE fraction ~80%Light output 40K/MeVDecay time 230 nsecWavelength 410 nm

Crystal

LightGuide

3/8” thick

Miyaoka Summer 2006

Detection Efficiency

0.64

Miyaoka Summer 2006

Light response function versus position(spatial resolution)

x

E

x7x6x5x4x3x2x1

!

ˆ x =

xi "Eii

#

Ei

i

#

CrystalLG

PMT

Miyaoka Summer 2006

Spatial Positioning

From: The Essential Physics of Medical Imaging (Bushberg, et al)

Miyaoka Summer 2006

Techniques to optimize shape of lightresponse function

Siemens Medical Solutions product literature

Miyaoka Summer 2006

Scatter

detector - NaI(Tl)

PMTs

All scatter counts are within the object (unlike in PET)

Miyaoka Summer 2006

Gamma Camera Energy Spectra

Miyaoka Summer 2006

0

1 104

2 104

3 104

4 104

5 104

6 104

0 50 100 150 200

Nai(Tl) Energy Spectra (140 keV)

10% ER20% ER

Coun

ts

energy (keV)

Gamma Camera Energy Spectra

140 keV photons, 9.5 mm crystal

Miyaoka Summer 2006

The Scintillation Camera:Collimators

Miyaoka Summer 2006

Parallel Hole Collimator

detector - NaI(Tl)

PMTs

le

Miyaoka Summer 2006

Collimators - Septal Penetration

!

t "

6dµ

l # 3µ( )

Minimum septa thickness, t,for <5% septal penetration:

From: Physics in Nuclear Medicine (Cherry, Sorenson and Phelps)

Detector

l

d t

Collimatorsepta

Miyaoka Summer 2006

Collimator Efficiency

Collimators typically absorb wellover 99.95% of all photons emittedfrom the patient.

Trade-off between spatialresolution and detection efficiency.

Miyaoka Summer 2006From: The Essential Physics of Medical Imaging (Bushberg, et al)

Collimator Resolution

Miyaoka Summer 2006

Gamma Camera - spatial resolution

!

Rs

= Ri

2 + Rc

2( )

From: Physics in Nuclear Medicine (Cherry, Sorenson and Phelps)

Miyaoka Summer 2006

Types of Collimators

From: The Essential Physics of Medical Imaging (Bushberg, et al)

magnification

Miyaoka Summer 2006From: Physics in Nuclear Medicine (Cherry, Sorenson and Phelps)

Collimator: Resolution and Sensitivity

Miyaoka Summer 2006

Collimator: Resolution and Sensitivity

From: The Essential Physics of Medical Imaging (Bushberg, et al)

Miyaoka Summer 2006

The Scintillation Camera:Corrections and QA

Miyaoka Summer 2006

Gamma Camera Processing Electronics(energy correction)

2

3

45

6

7

8

10

11

12

131415

9

16

17

18

19

1

0

1 104

2 104

3 104

4 104

5 104

6 104

0 50 100 150 200

Energy channel vs. event location

10% ER (between)10% ER (over)

Co

un

ts

energy (keV)

Miyaoka Summer 2006

Gamma Camera Processing Electronics(with and without energy correction)

Miyaoka Summer 2006

Gamma Camera Processing Electronics(linearity correction)

2

3

45

6

7

8

10

11

12

131415

9

16

17

18

19

1

From: Physics in Nuclear Medicine (Cherry, Sorenson and Phelps)

Miyaoka Summer 2006

Gamma Camera Processing Electronics(linearity correction)

Miyaoka Summer 2006

Additional Gamma Camera Correction(sensitivity / uniformity)

Acquired from long uniform flood after energy andlinearity corrections have been applied

Multiplicative correction

Adjusts for slight variation in the detection efficiencyof the crystal

Compensates for small defects or damage to thecollimator

Should not be used to correct for large irregularities

Miyaoka Summer 2006

Daily Gamma Camera QA Tests

Photopeak window

Flood uniformity

From: The Essential Physics of Medical Imaging (Bushberg, et al)

Miyaoka Summer 2006

Multienergy spatial registration (e.g., Ga-67 (93-, 185-, and 300 keV) gamma rays)

From: The Essential Physics of Medical Imaging (Bushberg, et al)

properly adjusted improperly adjusted

Miyaoka Summer 2006

Spatial Resolution Test

From: The Essential Physics of Medical Imaging (Bushberg, et al)

FWHM of LSF = 1.7 x (size of smallest bar resolved)

Miyaoka Summer 2006

Pulse Pile-up

From: Physics in Nuclear Medicine (Sorenson and Phelps) and (Cherry, Sorenson and Phelps)

Energy spectra

Pile-up in image

Miyaoka Summer 2006

The Scintillation Camera:Image Acquisition

Miyaoka Summer 2006

Image Acquisition• Frame mode (data stored as an image)

- static- single image acquisition- can have multiple energy windows

- dynamic- series of images acquired sequentially

- gated- repetitive, dynamic imaging- used for cardiac imaging

• List-mode (data stored event by event)- time stamps are included within data stream- allows for flexible post-acquisition binning- can result in very large data files

Miyaoka Summer 2006

Gated Acquisition

From: The Essential Physics of Medical Imaging (Bushberg, et al)

Miyaoka Summer 2006

Region of Interest (ROI) and Time-ActivityCurves (TAC)

From: The Essential Physics of Medical Imaging (Bushberg, et al)