A depth-of-interaction PET detector using a stair-shaped reflector arrangement and a single-ended scintillation light readout.

Positron emission tomography (PET) detectors with the ability to encode depth-of-interaction (DOI) information allow us to simultaneously improve the spatial resolution and sensitivity of PET scanners. In this study, we propose a DOI PET detector based on a stair-pattern reflector arrangement inserted between pixelated crystals and a single-ended scintillation light readout. The main advantage of the proposed method is its simplicity; DOI information is decoded from a flood map and the data can be simply acquired by using a single-ended readout system. Another potential advantage is that the two-step DOI detectors can provide the largest peak position distance in a flood map because two-dimensional peak positions can be evenly distributed. We conducted a Monte Carlo simulation and obtained flood maps. Then, we conducted experimental studies using two-step DOI arrays of 5  ×  5 LuYSiO:Ce crystals with a cross-section of 1.7  ×  1.7 mm and different detector configurations: an unpolished single-layer (S) array, a polished single-layer (S) array and a polished stacked two-layer (T) array. For each detector configuration, both air gaps and room-temperature vulcanization (RTV) silicone gaps were tested. Detectors S and T showed good peak separation in each scintillator with an average peak-to-valley ratio (PVR) and distance-to-width ratio (DWR) of 2.09 and 1.53, respectively. Detector S showed lower PVR and DWR (1.65 and 1.34, respectively). The configuration of detector T is preferable for the construction of time-of-flight-DOI detectors because timing resolution was degraded by only about 40 ps compared with that of a non-DOI detector. The performance of detectors S and S was lower than that of a non-DOI detector, and thus these designs are favorable when the manufacturing cost is more important than timing performance. The results demonstrate that the proposed DOI-encoding method is a promising candidate for PET scanners that require high resolution and sensitivity and operate with conventional acquisition systems.