Engineering the Next-Generation PET Detectors

Positron emission tomography (PET) is a functional imaging modality where image contrast is generated by exploiting the biochemical activity of the lesion of interest. The technique is widely used in the clinic, mainly for staging of cancerous lesions and monitoring their response to therapy. This chapter discusses recent research and engineering efforts aimed at improving images obtained with clinical PET cameras. We want to provide the reader with an overview of novel techniques that potentially will make it into clinical PET systems. After introducing PET and the current state-of-the-art commercially available clinical systems, we will discuss characteristics of current and novel scintillating materials and introduce improvements in spatial resolution through depth-of-interaction measurements and novel optical photon extraction methods. Next will be a discussion of various photodetectors: we present photomultiplier tubes, the current clinical workhorse in PET, as well as silicon-based solid-state photodetectors: avalanche photodiodes (APDs) and silicon photomultipliers (Si-PMs). We also briefly discuss semiconductor detectors that do not require photodetectors. Improved time resolution and its consequences for time-of-flight (TOF) imaging is the next topic of focus. Accurate TOF information significantly improves image SNR. Furthermore, we present the challenges involved in combining PET with MR systems and improvements in image reconstruction speed using GPUs.