Electrical delay line multiplexing for pulsed mode radiation detectors

Medical imaging systems are often composed of a large number of radiation detectors to provide high resolution imaging. For example, whole-body Positron Emission Tomography (PET) systems are typically composed of thousands of scintillation crystal elements, which are coupled to photosensors. PET systems would greatly benefit from methods to reduce the number of data acquisition channels, such that the cost and complexity can be kept at a minimum. In this paper we present an electrical delay line multiplexing scheme that can significantly reduce the number of readout channels, while the signal integrity is preserved for good time resolution performance. A 4 × 4 LYSO crystal array, with each crystal element having 3 mm × 3 mm × 5 mm dimensions, was coupled to 16 Hamamatsu MPPC S10931-050P SiPM elements. For proof-of-concept, 4 SiPM elements of the array were connected to the multiplexing stage. Results show that each SiPM element could be accurately identified. The method is flexible to allow multiplexing configurations across different block detectors, and is scalable to an entire ring of detectors.