Abstract
Positron emission tomography (PET) plays important roles in cancer diagnosis and molecular imaging research; but potential points remain for which big improvements could be made, including resolution, sensitivity and costs. For example, the sensitivity of present PET scanners does not exceed 10%. This means that more than 90% of the gamma-rays emitted from a subject are not utilized for imaging. Therefore, research on next generation PET technologies remains a hot topic worldwide. In this paper, we introduce some research trends by describing PET physics research in the National Institute of Radiological Sciences (NIRS). A depth-of-interaction (DOI) detector, for which various methods have been studied, will be a key device to get any significant improvement in sensitivity while maintaining high spatial resolution. DOI measurement also has a potential to expand PET application fields because it allows for more flexible detector arrangement. As an example, we are developing the world's first, open-type PET geometry “OpenPET”, which is expected to lead to PET imaging during treatment. The DOI detector itself continues to evolve with the help of recently developed semiconductor photodetectors, often referred to as silicon photomultipliers (SiPMs). We are developing a SiPM-based DOI detector to achieve sub-mm spatial resolution, which is reaching the theoretical limitation of PET imaging.
