I Jornadas RSEF / IFIMED de Física Médica

Towards using large and thick monolithic scintillators with high DOI performance

No programado

Parque Científico. Salon de Actos Edificio de Cabecera (IFIC-Valencia)

Descripción

Clinical and organ-dedicated PET systems typically require a high efficiency imposing the use of thick scintillators, normally through crystal arrays. When depth of interaction (DOI) information is required, 2 layers in the staggered or phoswich approach are mounted, resulting in a higher material cost. An alternative we are proposing in this work is the use of thick and large monolithic crystals. In order to return accurate 3D photon impact coordinates, both planar and DOI, but also good energy resolution are required. We have tested three surface treatments for a 50x50x20 mm3 LYSO block. We left the lateral walls black painted and the exit face coupled to the photosensor (12x12 SiPM array) polished. The entrance face was (i) black painted, (ii) covered with a specular film (ESR) and (iii) coupled to a retro-reflector (RR) layer. (i) and (iii) keep a good DOI linearity and, on average, reached 5 mm DOI FWHM. Approaches using ESR and RR layers return constant and good energy resolutions nearing 14%. The best result concerning the detector spatial resolution was obtained when the RR was used, being as good as 2.0 mm at the entrance crystal layer and 1.3 mm in the layer closest to the photosensor (without source finite size corrections).