Current Status of Cherenkov-Based Gamma Detectors for TOF-PET and Proton Range Verification

Time-of-flight positron emission tomography (TOF-PET) and proton range verification (PRV) in proton therapy are based on the detection of gamma photons. Despite the difference in the ultimate goal and status of each of these two modalities, both heavily rely on the gamma detectors used in associated imaging systems. The emission of Cherenkov light has been studied extensively over the last decade as a gamma-detection signature in different detector configurations for TOF-PET and PRV. This review aims at: 1) capturing the breadth of works that report on using Cherenkov light for these applications from a detector instrumentation perspective and 2) summarizing barriers encountered by these approaches in their path toward commercial adoption. This review is structured in seven sections: I) brief introduction of TOF-PET and PRV needs that might be addressed with Cherenkov-based gamma detectors; II) physics of Cherenkov emission, propagation, and detection; experimental efforts in detector characterization grouped by the nature of the signals involved in the detector, i.e., III) simultaneous emission of Cherenkov and scintillation light; IV) pure Cherenkov emitters; and V) semiconductor detectors with simultaneous Cherenkov emission; Section VI consolidates the information with a special attention to challenges and potential strategies to overcome them; and Section VII concludes with a short paragraph. We hope this comprehensive review of the extensive work of researchers in this field in the last decade triggers further discussion and sparks inspiration among the community.