Initial assessment of the Monte-Carlo simulation of SPECT recording with the new region-centric CZT “DSPECT” camera

Abstract

Significant improvements have been achieved recently for gamma-cameras dedicated to myocardial perfusion imaging such as the DSPECT camera. These cameras involve new Cadmium-Zinc-Telluride (CZT) detectors and original "heart-centric" collimation systems and up to now, they have not been analyzed through Monte-Carlo simulations modeling systems. This study was aimed at analyzing the DSPECT camera by using the "Geant4 Application for Emission Tomography" (GATE). This Monte-Carlo simulation tool is commonly used for SPECT and PET imaging and is based upon a modeling of detectors response and of radiations interactions. The DSPECT gamma-camera involved 9 mobile blocks of pixelated CZT detectors with a wide-angle square-hole tungsten collimator system. A total of 120 projections is recorded by each block by means of a 'region-centric' acquisition. Placements and movements of detector-blocks were tried to be simulated by GATE, as well as the detector response in terms of count sensitivity and spatial and energy resolutions. This simulation was applied to point and linear sources of 99mTc and simulation results were compared to what was obtained by the real recording of such a point source. The real and simulated recorded data were both reconstructed by a specific algorithm of iterative reconstruction, which compensates for the collimatorrelated loss in spatial resolution. Excellent agreement was documented between simulated and real recording: 1) for count sensitivity with an <; 1 % difference, 2) for energy resolution, with only a 5% difference for the full width at half maximum (FWHM) of the 99mTc photopeak and 3) for spatial resolution with only a 7% difference for the full width at half maximum of the point source (simulated recording: 7.9 mm and real recording: 7.4 mm). The modeling of the recording of a point sourc