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http://www.nuclear.kth.se/diploma/PetProject/intro.html

Development of a Time-of-Flight and 3D Demonstration Set-up for Positron Emission Tomography

Mikael Steén and Per Uhlén

Abstract

This report describes the development of a time-of-flight and 3D demonstration set-up for positron emission tomography (PET). The detector system consists of 48 barium fluoride (BaF2) scintillators arranged in a ring.

In the initial phase of the development, measurements of the characteristics of two detector prototypes differing in the shapes of the scintillators, were performed. The measurements were then complemented by Monte-Carlo simulations of the entire set-up, in which the measured energy and time response of the detector prototypes were included. The data from the simulations where then processed by conventional image reconstruction algorithms. The results formed the basis for the overall design of the detector system.

The set-up will be used in the undergraduate as well as graduate student training program in Physics at the Royal Institute of Technology. Therefore, this report contains a general overview of the physics and instrumentation associated with positron emission tomography.

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• 1 Introduction
• 1.1 Basic Physics in PET
• 1.1.1 Beta Decay
• 1.1.2 Annihilation Radiation
• 1.1.3 Interactions of Gamma Radiation with Matter
• 1.1.3.1 The Interaction Cross-Section
• 1.1.3.2 The photoelectric effect
• 1.1.3.3 Compton Scattering
• 1.1.3.4 The Stopping Power
• 1.1.3.5 The Concept of Resolution
• 1.1.3.6 Detector Efficiency
• 1.1.3.7 Scintillation Detectors
• 1.1.3.8 Photomultiplier Tubes
• 1.2 The Principles of PET and TOFPET
• 1.2.1 Basic Function
• 1.2.2 Coincidence Detection
• 1.2.3 PET versus TOFPET
• 1.2.4 Multi-Ring Scanner
• 1.2.5 Intrinsic Limitations
• 1.2.5.1 Positron Range
• 1.2.5.2 Noncollinearity
• 1.2.5.3 Statistical Limitations
• 1.2.5.4 Geometrical Limitations
• 1.3 Clinical PET Systems
• 2 Performance Measurements
• 2.1 Measurement Electronics
• 2.1.1 Constant Fraction Discriminator
• 2.1.2 Time to Pulse Height Converter
• 2.1.3 Multichannel Analyser
• 2.2 Results
• 2.2.1 Energy Resolution
• 2.2.2 Time Resolution
• 2.2.3 Efficiency
• 3 Simulations
• 3.1 GEANT
• 3.2 Simulations of the TOFPET System - General Approach
• 3.3 Simulation of Measured Efficiency in Singles Mode
• 3.4 Simulations of Ring Performance
• 3.4.1 Expected Spatial Resolution
• 3.5 The Steén Phantom
• 4 Image Processing
• 4.1 Raw Data
• 4.2 2D Image Reconstruction
• 4.3 Forward Projection
• 4.4 Reconstruction from Parallel Projections -The Central Slice Theorem
• 4.4.1 Back Projection
• 4.4.2 Filtered Back Projection
• 4.5 3D Image Reconstruction
• 4.6 Additional Notes on Image Reconstruction
• 4.6.1 Iterative Reconstruction Methods
• 4.6.2 Shannon's Sampling Theorem
• 4.7 Samples of Images
• 4.7.1 2D PET and TOFPET Images
• 4.7.2 3D TOFPET Images
• 5 Design
• 5.1 The Detectors
• 5.2 The Mechanical Support Structure
• 5.3 Electronics and Data Acquisition
• 6 Conclusions
• 7 Acknowledgements
• 8 References
• Appendix One MATLAB Code for Image Processing
• Appendix Two FORTRAN Code for GEANT Simulations