Development of an ultrasensitive small animal PET with 4-layer DOI detectors for sub-second dynamic rodent imaging

Objective.Dynamic positron emission tomography (PET) imaging is important for preclinical research since it can visualize the functional information of rodent models as a function of time. However, the temporal resolution of small animal PET imaging has been limited to a scale of seconds due to low sensitivity, and it is not sufficient to capture cardiac or brain function accurately. Here, we present an ultrasensitive small-animal PET scanner with total-body coverage for sub-second dynamic imaging of a rat.Methods.The ultrasensitive small animal PET scanner has a 155 mm inner diameter and 325.6 mm axial coverage. The PET scanner has six rings, each of which has 10 depth-of-interaction (DOI) detectors. Each DOI detector consists of a four-layer Zr-doped gadolinium oxyorthosilicate crystal array (2.85 mm pitch, 30 mm total thickness) and 8 × 8 multi-anode photomultiplier tubes. The physical PET performance was evaluated based on the National Electrical Manufacturers Association NU4 protocol. Sub-second dynamic rat imaging was performed with¹⁸F-FDG tracer.Main results.The peak absolute sensitivity was 20.2% and spatial resolution was 2.6 mm at the center of the field of view with an energy window of 400-600 keV. Total-body images of a rat were obtained with a single bed position. The cardiac function of a rat was visualized with 0.25 s temporal resolution, which was hardly possible with conventional small animal PET scanners.Significance. The developed ultrasensitive animal PET enabled sub-second dynamic PET imaging in rodent models with total-body coverage. In conclusion, the ultrasensitive small animal PET scanner can serve as a useful molecular imaging tool for preclinical research with its long axial coverage sub-second temporal resolution.