Potential advantages of tapered detector in PET

Modular detectors have attracted extensive attention in position emission tomography (PET) system design. Various detector system layouts can be constructed from modular detectors to match the different performance requirements from different applications. In the modular detector design, the lightguide or the fiber is commonly used to construct large continuous arrays to eliminate the gaps introduced by the inactive areas at the edges of photosensors. However, the lightguide or fiber would cause light loss, which worsens the detector´s energy and timing performance. To solve this problem, we propose using tapered crystals in the modular detector design. The tapered crystal can eliminate the gaps between detectors without the help of lightguides or fibers, simplify the detector´s structure and increase the light output. The increased light output implies better energy and timing performance, which may reduce the randoms and scatters in data and finally improve the quality of reconstructed image. In this paper, we developed two tapered lutetium yttrium orthosilicate (LYSO) array detectors and evaluated their position profile, energy resolution, timing resolution, sensitivity and phantom image. Tapered detectors are compared with detectors using the lightguide. The results show that the tapered detector has a better energy and timing determination ability and a decreased sensitivity, while the quality of the position profile and phantom image are almost unchanged.