Development of a New PET Detector with Depth-Encoding Capability Using Wavelength-Shifting Fiber Readout

A new concept of positron emission tomography detector with depth-encoding capability is proposed and developed for small-animal imaging. The detector module is based on wavelength-shifting (WLS) fibers coupled to both sides of a scintillator array having a unique pattern. The scintillator array consists of 15× 15 lutetium yttrium orthosilicate crystals with three different heights: 18, 20, and 22 mm. On the every other line, crystals having 2 mm shorter height are arranged to the x -direction on the top and the y -direction on the bottom of the array to make grooves for WLS fiber insertion. WLS fibers are inserted into these grooves and one end of each WLS fiber is coupled to a single channel silicon photomultiplier to detect scintillating lights trapped in the fiber. Field-programmable gate array combined 64-channel data acquisition (DAQ) system is used for DAQ and data processing, such as position, energy, and time decoding. The performance parameters, including pixel identification, energy resolution, depth of interaction (DOI) resolution, and timing resolution, were evaluated for proof of concept. The results proved that the design of detector allows not only to provide reasonable DOI information, but also to reduce the number of channels for sensors and electronics dramatically.