A New Rapid Acquisition Solid State Imaging System for Cardiac

SPECT Imaging

S.S. Gambhir M.D., Ph.D.Nuclear Medicine Grand Rounds

September 2007

SPECT vs. PET

• SPECT has potential for multiplexing• SPECT can achieve very high spatial

resolution• SPECT isotopes have some advantages

but also key disadvantages• SPECT is limited by sensitivity and

inability to do dynamic rapid acquisition

Gamma Camera/SPECT

GAMMA CAMERA (GC)

GC GC

COLLIMATOR

NaI CRYSTALS

PHOTOMULTIPLIER TUBES

TO COMPUTER

GAMMA RAYS

SUBJECT INJECTED WITH GAMMA-EMITTING PROBE

SCHEMATIC OF A GAMMA CAMERA

Nuclear Cardiac Imaging

Stress

Rest

Scintillation Cameras for Cardiac Imaging

A. Dual Head, Variable Angle

GE Infinia

B. Dual Head, Fixed 90o

GE Ventri

C. Compact Dual Head, Fixed 90o

Siemens C-Cam

Current SPECT Technology

• Detectors– Dual-Head– NaI(Tl) Scintillation

Cameras– Fixed 90o geometry

• Data Acquisition– Rotation – 90o

– No. of frames – 60 – Acquisition – 180o

Objectives of New SPECT System• Designed specifically for cardiac imaging• Improved energy resolution• Improved spatial resolution• Significant reductions in imaging times (x10)• Improved patient comfort

– Imaging in an upright or reclining position– Reduction of claustrophobia– Elimination of need for arms over head

• Small footprint to fit in ED, offices, exam rooms, etc.

D-SPECT™ Cardiac ScannerSpectrum-DynamicsHaifa, Israel

Dynamic SPECT(D-SPECT)

Detector Configuration

10 rotatingcolumns

Detector Configuration

D-SPECT™ detector head

D-SPECT Detector Configuration

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

64 elements~160 mm

16 elements~40 mm

2.46 mm

2.46 mm

Detector Column Detail

5 mm thick CZTDetector Element

1024 elementsper column

DetectorColumn

Column Collimator

Detector Array Direct conversion of photonenergy to voltage pulse

Detector Characteristics

Detector ThicknessEffective

Atomic No.Density

(gm/cm3)Intrinsic Efficiency

(140 keV)

5 mm 88%

90%9.5 mm(3/8 in)

Energy Resolution(140 keV)

CZT 49 5.7 6%

NaI(Tl) 50 3.7 10%

Rel

ativ

e co

unts

Tc-99mHALF LIFE = 6.02 Hours

140.5 KeV18.5 KeV

100

7

CZT Energy Resolution6%

NaI(Tl) Energy Resolution10%

Sources of Improvements in Sensitivity

• Sensitivity– Use of wide angle collimators with high geometric efficiency– Unique ability to concentration acquisition on region-of-

interest (ROI-centric scanning)

Sources of Improvementsin Spatial Resolution

• Spatial Resolution– Data collection from many angles– Decreased distance between detectors and ROI– Improved energy resolution– Use of proprietary BroadviewTM reconstruction

algorithms based on the ML-EM method

D-SPECT Collimator

GE LEHR Collimator

Collimator HoleShape

Material Septum(mm)

Length(mm)

Hole Dia.(mm)

GeometricEfficiency

D-SPECT Square Tungsten 0.2 21.7 2.26 0.000748

GE LEHR Hex Lead 0.2 35 1.5 0.0000985

Ratio 7.6

Collimator Comparison

No lead x-rays to interfere with 201Tl imaging

15 cm

7.5 cm

Spatial Resolution (mm)

Point # X Y

1-outer 4.7 5.2

2-outer 5.5 4.7

3-central 7.0 6.5

Average 5.7 5.5

13.612.63-central

12.813.4Average

12.412.82-outer

12.414.81-outer

YXPoint #

Spatial Resolution (mm)

2.11.83-central

2.32.3Average

2.62.32-outer

2.43.11-outer

YXPoint #

RatioA-SPECT/D-SPECT

15 cm

Spatial Resolution NEMA NU1 2001

A-SPECTD-SPECTAnger Camera SPECT

(A-SPECT)Dual Head 90O

60 frames, 180O

Circular orbitLEHR Collimators

Resolution and SensitivityCo-57 line source 2.5 million counts

A-SPECT

1 mm

D-SPECT

Measured at 100 mm

System SpatialResolution

(mm)

Time(sec)

A-SPECT 10.4 600

D-SPECT 5.5 49

Ratio 1.9 12.3

Gated Acquisition

• Acquired data are encoded during acquisition with EKG signal so that gated images may be reconstructed after data acquisition is complete

Torso Phantom Studies

D-SPECTA-SPECT

Anthropomorphic torso phantomActivity in liver, background, myocardium

No defect

D-SPECTA-SPECT

D-SPECTA-SPECT

Anthropomorphic torso phantomActivity in liver, background, myocardium

20 mm; 50% activity defect

D-SPECTA-SPECT

D-SPECTA-SPECT

Anthropomorphic torso phantomActivity in liver, background, myocardium

10 mm defect

D-SPECTA-SPECT

Dual Isotope Phantom Studies

D-SPECT

SPECT

Virgin Thallium

Dual Thallium

Virgin Thallium

Dual Thallium

10.58.47.0SensitivityGain (SD/GE)

*990,00095,000*920,000110,000*950,000136,000Counts/minfrom Myocardium

73.1%8.3%71.1%8.9%71%9.5%% MyocardiumCounts

1.981.18*1.831.43*1.901.70MyocardiumCounts (M)

*2.7114.26*2.6116.15*2.6817.08Total Counts (M)

212.5212.5212.5Duration (min)

10:339:2514:2511:5519:2117:08Start Acq

26.5 mCi at 08:4023.4 mCi at 11:1028.3 mCi at 16:13Administration

Raw Data

SDGESDGESDGE

Patient #130Patient #126Patient #125

*After decay correction

47 y/o male, overweight, hypertensive,chest pain - Stress/Rest

AXIS, Philips Medical Systems

D-SPECT, Spectrum Dynamics

Rest2 min

Stress4 min

Rest11 min

Stress19 min

44 y/o male, hypertensive, elevated cholesterol levels, asymptomatic - Stress/Rest

AXIS, Philips Medical Systems

D-SPECT, Spectrum Dynamics

Rest2 min

Stress4 min

Rest11 min

Stress19 min

Future ProductsD-SPECT/CT

Patient personalized RFID-tagged Syringe

Information transmitted to

D-SPECT Scanner; settings

adjusted automatically

Patient demographics acquired and transmitted to

®-Scan Wristband

Verification & Authentication

®-Scan Wristband:Patient demographics integrated

with dose and injection time

D-SPECT Cardiac Scanner System features the ®-SCAN data transfer system based on RFID technology.

Conclusions• D-SPECT is a new cardiac SPECT system that has

been developed using a radically new data acquisition technology. This system exhibits:– Factor of ~2 improvement in spatial resolution– Factor of ~10 improvement in sensitivity– Factor of ~1.7 improvement in energy resolution

• Systems will be in nuclear medicine laboratories in late 2007

• Clinical trials are just starting

Acknowledgments

• Dalia Dickman and Miki Nagler, Spectrum Dynamics

• Web Site:– www.Spectrum-Dynamics.com