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

We present techniques and systems for a CZT gamma camera head based on an array of discrete CZT detectors and associated front-end electronics. In Section I, we describe the performance of a small 256 detector (16 × 16) CZT imager in terms of homogeneity, energy resolution, and detection efficiency. The array is composed of groups of 16 single detectors (4×4×6 mm³ each), each group served by a 16-channel multiplexed ASIC preamplifier. The electron bi-parametric (BP) spectrum with the depth of interaction information is used to improve detection efficiency. The present work compares the performance (sensitivity, spatial resolution, and 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 Section II, we present an approach to the next generation of this technology, a gamma camera with a segmented monolithic CZT detector associated with the electron BP spectrum, which 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, and 2.5-mm pitch) associated with 16 individual ASIC preamplifiers: an energy resolution close to 2% FWHM at 122 keV has been obtained on 16 pixels after BP correction.