The PET detectors consist of three rings with each having eight detector modules/arrays. Each array is made up by 144 SiPMs, arranged in 12 by 12 rows and columns, covering an active area of approximately 50 × 50 mm². Each SiPM array is directly connected to a readout circuit that provides output for each row and column of the array. The row and column signals are digitalized with custom high-speed ADC electronic boards capable of processing up to 66 channels. The PET crystal is a 50 x 50 mm² Lutetium Yttrium Orthosilicate (LYSO) crystal that is 10 mm thick and cut into a pyramidal shape. The impinging coordinates of the gamma-ray are not determined by the localization of the pixel containing all the emitted light, but by the determination of the gravity center of the detected light. Such detection is performed by photodetector anodes. The system employs silicon position sensitive photomultipliers for light detection. Each detector module provides information of both X and Y projections of the complete scintillation light distribution and calculates the centroid of the X and Y coordinates and the photon depth of interaction DOI.

The output signals for each row and column, in addition to the summed trigger signal and the temperature sensor information, are transferred with flexible boards 30 cm away from the PET detector without any additional connections in between. This design avoids the use of nickel containing connectors which might interfere with the MR main field and prevents eddy currents in metallic structures that are induced by rapidly switching gradient fields of the MRI-gradient-system.

The PET detector readout electronics consists of: