SmartPET The HPGe PET System

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SmartPET The HPGe PET System
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What is SmartPET ?

• Small Animal PET Demonstrator
• High Purity Germanium Detectors
• Application of GRT PSA
• Novel PET System (?)

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Why SmartPET?

• Existing technology relies on scintillator
  technology
• Limited position resolution
• High patient dose requirement
• Poor energy resolution ( 30 _at_ 511keV)
• Will not function in large magnetic field

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What can we achieve?

• Use scattered events
• Reduce patient dose
• Increase patient throughput
• Improve image quality (?)

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Germanium Detectors
What do HyperPure Germanium detectors provide?

• Excellent Energy Resolution
• The use of Digital Acquisition Systems
• The application of Pulse Shape Analysis (PSA)
• The application of Gamma Ray Tracking (GRT)
  algorithms
• Ultimately A highly efficient PET system

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Gamma Ray Tracking

• Follow the path of incident gamma ray photons
• Pinpoint interaction positions
• Knowledge of energy, time and position
• Deduce first point of interaction
• Define LORs

All by the implementation of Pulse Shape Analysis
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Pulse Shape Analysis

• Analyse Detector Response Pre-amp charge pulse
• Real charge pulse Rise time Depth
  of interaction
• Image Charge Analysis Asymmetry
  x-y position
• Generate Database of Simulated pulse shapes
  (E-Field Sim)
• Use database for online PSA Track photon
  interaction positions through the detector
  (GRT)

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Whats in a Charge Pulse?
T90
100 of pulse amplitude
T60
90
60
T30
Amplitude
30
10
Time
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PSA Depth
Q(t)
Incident gamma ray
e-
h
Time

• The shape of the charge pulse is position
  dependent
• Rise times at T30, T60 and T90 can be used to
  find interaction depth
• Time difference method time to collect
  electrons vs. holes

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PSA x-y Position

• Drift of charge carriers induces a signal on
  adjacent electrodes
• Magnitude depends on the position of interaction
  relative to the electrode
• Image Charge Asymmetry parameter
• Vertical and horizontal position

V
0
e-
h
-1800V
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The Outcome

• 1mm x 1mm x 1mm position resolution
• Excellent energy resolution ( 0.5 _at_ 511keV)
• Ability to use high proportion of events
• High patient throughput
• High quality diagnostic imaging
• Integrated PET/MRI systems

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A.J. Boston, H.C. Boston, R.J. Cooper, J.R.
Creswell, J. Dobson, A.N. Grint, C.Hall, I.
Lazarus, A. R. Mather, P.J. Nolan, D. Scraggs,
G.Turk