Performance Study of a Large Monolithic LYSO PET Detector With Accurate Photon DOI Using Retroreflector Layers

• Published in: IEEE transactions on radiation and plasma medical sciences Vol. 1; no. 3; pp. 229 - 237
• Main Authors: Gonzalez-Montoro, Andrea, Benlloch, Jose M., Gonzalez, Antonio J., Aguilar, Albert, Canizares, Gabriel, Conde, Pablo, Hernandez, Liczandro, Vidal, Luis F., Galasso, Matteo, Fabbri, Andrea, Sanchez, Filomeno
• Format: Journal Article
• Language: English
• Published: IEEE 01.05.2017
• Subjects: Crystals; Detectors; Energy resolution; Face; Monolithic scintillators; photodetector technology; photon depth of interaction (DOI); Photonics; positron emission tomography; Scintillators; Spatial resolution
• ISSN: 2469-7311; 2469-7303
• DOI: 10.1109/TRPMS.2017.2692819

Clinical and organ-dedicated PET systems typically require a high efficiency imposing the use of thick scintillators, normally through crystal arrays. To provide depth of interaction (DOI) information, two or more layers are sometimes mounted in the staggered or phoswich approach. In this paper, we are proposing an alternative using thick and large monolithic crystals. We have tested two surface treatments for a 50 mm × 50 mm × 20 mm LYSO block. We provide data in this paper as close as 5 mm to the lateral walls. We left those walls black painted and the exit face coupled to the photosensor (12 × 12 SiPM array) polished. The entrance face was: 1) black painted or 2) coupled to a retroreflector (RR) layer. These configurations keep a good DOI linearity and, on average, reached 4 mm DOI resolution, measured as the full width at half of the maximum. Approaches using RR layers return constant and good energy resolutions nearing 12%, compared to a range of 15%-16% in the case of totally black painted blocks. The best result concerning the detector spatial resolution was obtained when one of the smallest RR was used (120 um corner cube size), being 1.7 mm at the entrance crystal layer and 0.7 mm in the layer closest to the photosensor. These values worsen at least 30% for the black treatment case.