Image quality of Medipix2 assemblies with silicon detectors of two different thicknesses

Silicon pixel detectors of 300 and 700 μm thick were coupled to Medipix2 [Medipix collaboration web site: http://medipix.web.cern.ch/MEDIPIX; Proceedings of the IEEE Nuclear Science Symposium and Medical Imaging Conference, San Diego, California, 4–10 November 2001, M7-4] read-out chips and tested for use in X-ray imaging. After the evaluation of the flat-field correction gain map [Nucl. Instr. and Meth. A 460 (2001) 81; Nucl. Instr. and Meth. A 509 (2003) 146], the functionality of the Medipix2 discriminator threshold setting was investigated using an X-ray source providing a selection of monochromatic X-rays. A phantom designed for mammography and a commercial X-ray source were used to measure the response versus the radiographic dose of the different assemblies to test objects of varying, known contrast. Results are presented in terms of recorded Signal-to-Noise Ratio (SNR) and of a direct evaluation of the Detective Quantum Efficiency (DQE) of the system, for both the assemblies.