Prototip bir X-ray görüntüleme sisteminin daha iyi bir dedeksiyon verimi için modellenmesi

Main goal of this thesis was to use Geant4 to model and design an x-ray imaging system based on Si-PIN photodiodes. After validation of the model with other methods and experiments, the model was used for determining several parameters' influence on image quality in an x-ray imaging system. The model has two sections of Geant4 codes which can be run independently. The first section includes the code for x-ray production and the second section includes the one for image construction. Production code produces the x-ray beam from x-ray tube with a stationary anode and imaging code retrieves this energy spectrum from the simulation results and use it as an input to simulate an x-ray imaging system. X-ray imaging system consists of an x-ray beam gun, targets to be imaged, two different anti-scatter grid options to reduce the number of scattering photons that degrades the contrast in the image and a detector to obtain the signal. All of the parameters related to these components were set to be adjustable. X-ray production validation was accomplished by comparing the simulation results with experimental and other methods. In general, spectral comparison was in good agreement except the amplitudes of the characteristic peaks. This is expected since all the comparisons in literature have shown the same behavior when comparing simulation with experimental result. The simulation was used for calculating the inherent filter thickness of an x-ray tube with a simple interpolation. Different types of anodes, effects of additional filters, detection area and source-to-detector distance were studied. Detector response of Amptek XR-100CR was simulated and compared with the experimental results to validate the success of determination of efficiency by the simulations. Simulations of x-ray imaging system were conducted to investigate the effects of parameters changing the image quality such as contrast and spatial resolution. For validation, a simulation was performed and the image obtained was compared with experimental study. A line test was included into the simulation to obtain the spatial frequency of designed x-ray imaging system. Optimization of grid/collimator studies were conducted to improve the contrast of the image. An anti-scatter grid with cylindrical holes and parallel plates were added as the simulation parameters with adjustable grid size. X-ray tube high voltage and pixel size on the detector were studied to investigate their effects on the image quality. Two separate graphical user interfaces XRTS (X-Ray Tube Simulations) and XRIS (X-Ray Imaging Simulations) were also prepared to modify some basic parameters in the Geant4 codes practically. Both of the applications are aimed to be open source codes for educational and research purposes.