Validation and optimization studies of small animal SPECT using GATE Monte Carlo simulation

Abstract

Small animal imaging has been widely considered for the development and evaluation of new radiopharmaceuticals. For this purpose, simulations are primarily used for the design and optimization of new and existing imaging devices, the assessment of acquisition and processing protocols. In this paper, the methodology follows two basic steps: (I) A validation of a small animal SPECT scanner which is based on CsI(Na) pixelated scintillator detector and a lead hexagonal parallel-hole collimator. In this phase, experimentally obtained results were directly compared to Geant4 Toolkit for Emission Tomography (GATE) simulation data. (II) The optimization studies with different collimator and semiconductor materials by using GATE simulation. The simulated and experimental planar sensitivities of the system were obtained 51.06 and 48.65 cps/MBq on the collimator surface, respectively. The difference between simulated spatial resolution and experimental value at 2.5 cm distance from the collimator surface was 3.27 %. Also, sensitivity of lead collimator was 18, 63.37, and 65.21% higher than tantalum, tungsten and gold collimators, respectively but gold collimator had the best spatial resolution. CdTe semiconductor detector usually has some superiority to the other semiconductors in energy resolution, spatial resolution, sensitivity, and detection efficiency. Very good agreement between GATE simulation and experimental results indicates that the GATE Monte Carlo simulation is appropriate and reliable tool for simulating imaging systems. Also, HiReSPECT has high resolution and sensitivity for imaging of small animals such as mice and rats. In the following, our study highlights that the collimator and crystal materials can significantly affect the camera performance. As well as developments in semiconductor detector technology can provide an appropriate substitution for scintillation detectors according to high sensitivity, better energy resolution, and also high spatial resolution.