University of Washington
Division of Nuclear Medicine
Introduction to PET Physics

[Table of contents] [List of figures] [List of tables]
[References] [List of abbreviations] [Copyright notice]


Table of Contents

1. Introduction

2. The physical principles of PET

2.1 Introduction
2.2 Positron emission and annihilation
2.3 Coincidence detection and electronic collimation
2.4 Photon interactions in human tissue and correction for gamma-ray attenuation
2.5 Types of coincidence events

3. 2D mode and 3D mode

3.1 Principles of operation
3.2 Sensitivity to true coincidence events
3.3 Sensitivity to scattered events
3.4 Sensitivity to random events
3.5 Effect of camera geometry

4. Image reconstruction

4.1 Introduction
4.2 Notation and mathematical theorems used
4.3 Analytic image formation in 2D PET
4.4 Filtered Back-Projection in 3D and 3D-RP

5. Detection systems in PET

5.1 Introduction
5.2 Scintillators and scintillation detectors
5.3 Pulse processing
5.4 Coincidence processing
5.5 Dead-time
5.6 Block detectors
5.7 Camera configurations in PET

6. Corrections for quantitative PET in 2D and 3D mode

6.1 Introduction
6.2 Attenuation correction
6.3 Correction for random coincidences
6.4 Scatter correction
6.5 Detector normalisation
6.6 Dead-time correction

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List of Figures

Figure 1

Positron emission and annihilation

Figure 2

Coincidence detection in a PET camera

Figure 3

Variation of point source response function (psrf) with position P in SPECT and in PET

Figure 4

Coincidence detection in an attenuating object

Figure 5

Types of coincidences in PET

Figure 6

Axial cut-away view of a multi-ring PET camera (not to scale) operating in 2D mode, showing direct and cross-plane rebinning

Figure 7

Axial cut-away view of a PET camera in 2D and 3D mode showing how the number of possible LORs can increase when the septa are removed

Figure 8

Predicted sensitivity from the number of LORs used in 2D and 3D mode

Figure 9

Effect of septa removal on sensitivity to scattered coincidences

Figure 10

Effect of septa removal on sensitivity to single events

Figure 11

3D co-ordinate system for a full-ring PET camera

Figure 12

Projections generated from a single central point source (3 projections shown)

Figure 13

Back-projections of a point source. With finite numbers of back-projection angles, "star" artefacts are seen

Figure 14

The Ramp and Hanning filters

Figure 15a

Parallel projections in 2D. Note that he LORs become closer together towards the edge of the FOV. To correct for this, the data must be re-sampled (arc corrected) prior to reconstruction

Figure 15b

Parallel projections in 3D

Figure 16

Axial cut-away diagram of a PET camera operating in 3D mode, showing the extent of the projection sets as a function of angle j

Figure 17

Features of a typical energy distribution for electrons involved in interactions with 511 keV photons

Figure 18

Features of a typical energy distribution measured by a scintillation detector system exposed to 511 keV photons

Figure 19

Schematic diagram showing coincidence processing in a PET camera

Figure 20

A block detector

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List of Tables

Table 1

Examples of radiotracers and their applications

Table 2

Properties of commonly used positron emitting radio-isotopes

Table 3

Notation for spatial and Fourier quantities

Table 4

Examples of scintillators and their properties

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Last revised by:

Ramsey Badawi

Revision date:

12 Jan 1999