Development of an optimised LSO/LuYAP phoswich detector head for the ClearPET camera

The paper describes the LSO/LuYAP phoswich detector head developed for the ClearPET small animal PET scanner demonstrator that is under construction within the Crystal Clear Collaboration. The detector head consists of a dual layer of 8/spl times/8 LSO and LuYAP crystal arrays coupled to a multi-channel photomultiplier tube (Hamamatsu R7600-M64). Equalisation of the LSO/LuYAP light collection is obtained through partial attenuation of the LSO scintillation light using a thin aluminium deposit of 20-35 nm on LSO and appropriate temperature regulation of the phoswich head between 30 to 60 /spl deg/C. At 511 keV, typical FWHM energy resolutions of the pixels of a phoswich head amounts to (28/spl plusmn/2)% for LSO and (25/spl plusmn/2)% for LuYAP. The LSO versus LuYAP crystal identification efficiency is better than 98%. Six detector modules have been mounted on a rotating gantry. Axial and tangential spatial resolutions were measured up to 4 cm from the scanner axis and compared to Monte Carlo simulations using GATE. FWHM spatial resolution ranges from 1.3 mm on axis to 2.6 mm at 4 cm from the axis.