ABSTRACT
Positron emission tomography (PET) aims to quantitatively measure the distribution of a radiotracer injected into a subject. The injected tracer is generally chosen to target bioprocesses of interest occurring in specic cells or tissues.1 Among tracers, the
6.1 Introduction .................................................................................................. 151 6.2 Physics of PET Scanners .............................................................................. 152 6.3 Trade-offs in Scanner Designs ..................................................................... 157 6.4 Typical Electronics Chain for PET ............................................................... 161
6.4.1 The Crystal ....................................................................................... 163 6.4.2 Common Detectors in PET ............................................................... 165
6.4.2.1 The Photomultiplier Tube and Its Amplication Stage ..... 165 6.4.2.2 Avalanche Photodiode-Based Detectors and Their
Amplication Stage ........................................................... 167 6.4.2.3 Noise Issues for APD-Based Detectors ............................. 167 6.4.2.4 Silicon Photomultipliers (SiPMs) ....................................... 171 6.4.2.5 Baseline Restoration and Holding ..................................... 172 6.4.2.6 Energy and Timing Measurement ..................................... 173
6.5 Multimodality ............................................................................................... 174 6.6 Conclusion .................................................................................................... 174 References .............................................................................................................. 175
most widely used in PET is indisputably the uorodeoxyglucose (FDG) for cancer studies and diagnosis.2 Currently, researchers focus on new tracers aimed at better understanding human gene properties or disorders and support development of new drugs.3 The imaging research under this perspective is better known as molecular imaging, where animal models play a crucial role.4 According to the results of a 2003 survey,5 discoveries in this research eld are so important that molecular imaging has been considered among the 10 technologies that will most affect human health. Since 2000, many small-animal PET scanners have been proposed to answer genomic and proteomic requirements.6,7 In contrast with clinical PET, small-animal imaging faces two major challenges originating from (a) the animal model’s small internal organ sizes and from (b) geometric side effects caused by the scanner’s small diameter. Many issues such as spatial resolution, sensitivity, and high count rates, along with the ability to support multimodality imaging, depict the modern challenges where trade-offs are constantly and carefully considered.
