Sensitivity analysis of the efficiency of Compton camera to the detector parameters using the GEANT4 computer code

Compton imaging is an imaging technique in which Compton scattering is used to produce images from a gamma-ray source. Compton imaging systems are also known as Compton camera. The basic design of Compton imaging systems consists of two-position detectors that are sensitive to the position and energy scattered from gamma rays. Compton camera efficiency is defined as the fraction of photons entering the scatterer (disperse) detector that undergoes only one Compton scattering and is then photoelectrically absorbed in the absorber detector. In the present study, the efficiency of a Compton camera was investigated based on semiconductor detectors using the GEANT4 simulation toolkit. In this study, the sensitivity of the efficiency of the Compton imaging systems to the distance between the source and the scatterer detector, the distance between the two detectors, dimensions, and thickness of the absorber and scatterer detectors, number of scatterer detectors with different thicknesses, the energy of radioisotope of the source, and semiconductor's type in the scatterer and absorber detectors were performed. To this end, the Compton camera was modeled using the GEANT4 simulation toolkit. In addition, the code was developed in C++ to get the correct events of efficiency in the Compton camera. The simulation model includes the details of the detector geometry, detector segmentation, and energy discrimination levels of the scatterer and absorber. According to the results, ¹¹C has the maximum efficiency as a radioactive source."GaAs" and "Ge" as the scatterer detector and "CdTe" and "HgI2" as the absorber detector are the best choices. According to the results, the shorter the distance between the source and the two detectors, the higher the efficiency of the Compton camera. Of course, this distance must be selected according to the application used. According to the results in the research, with increasing the dimensions of the scatterer detector plate, the amount of efficiency increases up to the dimensions of the absorber detector plate, but a size larger than the absorber detector, it reaches a degree of saturation. Also, by increasing the thickness of the scatterer detector, the efficiency first increases and then reaches the maximum value and then decreases, and increasing the thickness of the absorber detector increases efficiency. The results of the simulation in the present paper have an acceptable agreement with the experimental several types of research in the world. The results of this simulation can be considered for the design of Compton cameras.