Development of a proof of concept system for multi-modal compatible PET: Flexible PET

Recently, various PET-MRI systems with silicon photomultiplier (SiPM) arrays have been developed by many research groups [1-3]. We previously proposed the concept of a multi-modal compatible “flexible” PET scanner [4]. The scanner consists of adjustable two detector heads and scans a patient lying on a bed equipped with another medical device such as CT, MR and radiotherapy device. In this study, we have developed a proof-of-concept (POC) MR-compatible PET system that consists of two detector heads and the data acquisition (DAQ) system. The single detector module consists of 16 × 16 LGSO crystal array, a light guide and a 6 × 6 SiPM array. The size of each crystal element was 2.9 mm × 2.9 mm × 20.0 mm with a special reflector arrangement for four-layer DOI encoding. Two detector heads each consists of six detector modules are positioned in front of a permanent magnet (1.5 T) open MRI scanner. We evaluated the mutual interference between PET and MRI by the sequential PET/MRI experiments, and finally performed small animal imaging studies. These results showed MR-compatibility of our detectors and encouraged the concept of the “flexible” PET.