Performance and quality control of Clear-PEM detector modules

Clear-PEM is a dedicated PET scanner for breast and axilla cancer diagnosis, under development within the framework of the Crystal Clear Collaboration at CERN, aiming at the detection of tumors down to 2 mm in diameter. The camera consists of two planar detector heads with active dimensions 16.0 x 14.5 cm(2). Each head has 96 Clear-PEM detector modules consisting of 32 LYSO:Ce pixels with dimensions 2 x 2 x 20 mm(3) packed in a 4 x 8 BaSO4 reflector matrix compressed between two Hamamatsu S8550 APD arrays in a double-readout configuration for Depth-of-Interaction (DoI) determination. The modules are individually measured and characterized before being grouped into Supermodules (comprised of 24 modules). Measured properties include photo-peak position, relative gain dispersion, energy resolution, cross-talk and Dol resolution. Optical inspection of matrices was also performed with the aid of a microscope, to search for pixel misalignments and matrix defects. Modules' performance was thoroughly evaluated with a 511 keV collimated beam to exactly determine Dol resolution. In addition, a fast quality control (QC) procedure using flood irradiations from a (CS)-C-137 source was applied systematically. The overall performance of the 24 detector modules complies with the design goals of the Clear-PEM detector, showing energy resolution around 15%, Dol resolution of about 2 mm and gain dispersion among pixels of 15%. (c) 2007 Elsevier B.V. All rights reserved.