Monte carlo simulation study of a novel parallel-hole collimator with a CdTe pixelated semiconductor SPECT system

Recently, many studies have investigated the use of a pixelated semiconductor detector to improve spatial resolution. The purpose of this study was to evaluate novel parallel-hole collimator geometric designs with a CdTe pixelated semiconductor single-photon-emission computed tomography (SPECT) system. The pixelated semiconductor detector was modeled as a PID 350 detector (Ajat Oy Ltd., Finland) with small pixels (0.35 × 0.35 mm2) by using Geant4 Application for Tomographic Emission (GATE) software. We designed a novel parallel-hole collimator consisting of two overlapping parallel-hole collimators. Each hole size was four times that of the pixelated parallel-hole collimator. The overlap ratios of these collimators were 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, and 4:1. To evaluate the performance of this system, we evaluated the sensitivity and the spatial resolution. The results for our new parallel-hole collimator indicated that the evaluated sensitivity averages using overlap ratios of 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, and 4:1 were 4.45, 7.56, 7.51, 12.76, 12.65, 20.01, and 19.90 times higher, respectively, than those of the pixelated parallel-hole collimator. The evaluated averages of the spatial resolution varied depending on the source-to-collimator distances. In conclusion, we successfully designed a novel parallel-hole collimator with various overlap ratios of the collimator septal heights with a CdTe pixelated semiconductor SPECT system. Based on our results, we recommend using this collimator with a CdTe pixelated semiconductor SPECT system.