Feasibility of a CdTe-based SPECT for high-resolution low-dose small animal imaging: a Monte Carlo simulation study

Abstract

Dedicated single-photon-emission computed tomography(SPECT) systems based on pixelated semiconductors such as cadmium telluride(CdTe) are in development to study small animal models of human disease. Inan effort to develop a high-resolution, low-dose system for small animalimaging, we compared a CdTe-based SPECT system and a conventionalNaI(Tl)-based SPECT system in terms of spatial resolution, sensitivity,contrast, and contrast-to-noise ratio (CNR). In addition, we investigatedthe radiation absorbed dose and calculated a figure of merit (FOM) for bothSPECT systems. Using the conventional NaI(Tl)-based SPECT system, weachieved a spatial resolution of 1.66 mm at a 30 mm source-to-collimatordistance, and a resolution of 2.4-mm hot-rods. Using the newly-developedCdTe-based SPECT system, we achieved a spatial resolution of 1.32 mm FWHM ata 30 mm source-to-collimator distance, and a resolution of 1.7-mm hot-rods.The sensitivities at a 30 mm source-to-collimator distance were 115.73 counts/sec/MBq and 83.38 counts/sec/MBq for the CdTe-based SPECT andconventional NaI(Tl)-based SPECT systems, respectively. To comparequantitative measurements in the mouse brain, we calculated the CNR forimages from both systems. The CNR from the CdTe-based SPECT system was 4.41,while that from the conventional NaI(Tl)-based SPECT system was 3.11 whenthe injected striatal dose was 160 Bq/voxel. The CNR increased as a functionof injected dose in both systems. The FOM of the CdTe-based SPECT system wassuperior to that of the conventional NaI(Tl)-based SPECT system, and thehighest FOM was achieved with the CdTe-based SPECT at a dose of 40 Bq/voxelinjected into the striatum. Thus, a CdTe-based SPECT system showedsignificant improvement in performance compared with a conventional systemin terms of spatial resolution, sensitivity, and CNR, while reducing theradiation dose to the small animal subject. Herein, we discuss thefeasibility of a CdTe-based SPECT system for high-resolution, low-dose smallanimal imaging.