Performance and perspectives of a gamma camera based on CdZnTe for medical imaging

Techniques and systems for a CZT gamma camera head based on an array of CZT pixels and associated front-end electronics are being developed at CEA-LETI in an exclusive joint development with Saint-Gohain Crystals and Detectors (SCCD) who in turn are commercializing the technology. In a first section, we describe the performance of a small 256 pixel (16x16) CZT imager in terms of homogeneity, energy resolution and detection efficiency. The array is composed of groups of 16 single pixels (4×4×6 mm³ each) each group served by a 16-channel multiplexed ASIC preamplifier. The present work compares the performance (sensitivity, spatial resolution, contrast) of this small prototype imager and an Anger NaI(Tl) scintillation gamma camera using phantom images with small cold zones in a high scatter environment. In a second section, we present an approach to the next generation of this technology, a gamma camera with a segmented monolithic CZT detector associated with depth of interaction correction: using the electron Bi-Parametric (BP) spectrum which in addition to depth of interaction information also allows correction for spectral tailing and dramatically improves both detection efficiency and energy resolution. Results with and without BP correction are given for a 10×10×5 mm³ CZT monolithic detector (16 pixels, 2×2 mm pixel, 2.5 mm pitch) associated with 16 single ASIC preamplifier: an energy resolution lower than 2.5% FWHM at 122 keV has been obtained on 16 pixels after BP correction.