CTDIs (computed tomography dose indices) can be directly measured using an ion chamber or can be estimated using computer simulation techniques to the determine radiation dose. The purpose of this study was to demonstrate CTDI estimation by using GATE (geant4 application for tomographic emission) simulations and to extend the techniques to various CT applications. We simulated various phantom sizes to estimate values for different patients. The simulations were performed using a single axial scan with standard PMMA (polymethylmethacrylate) head and body phantoms. Simulations of exposure in air were performed to compare simulated results with physically measured data. Simulations of the absorbed dose in PMMA digital phantoms were performed to compare simulated results with physically measured data in corresponding PMMA physical phantoms at five different positions (at center and 12-h, 3-h, 6-h, 9-h positions in the phantoms). Additional simulations were performed for PMMA digital phantoms of various diameters (1 - 50 em) at various kVp (80, 100, 120, 140 kVp) and mAs (100, 200, 300, 400 mAs) levels. For the PMMA head and body phantoms, the results of the simulations showed an agreement with the measured data, with a maximum percent difference of 8.3 % (head) and 4.1 % (body) for all energies applied. For the different positions, the results of simulations showed an agreement with measured data, with a maximum per position difference of 4.7 % (head) and 5.1 % (body) for 120 kVp. Within these limitations, for various kVp and mAs levels, the results showed that the values nonlinearly decreased as a function of diameter. For various diameters, the results showed that the values nonlinearly and linearly increased as functions of kVp and mAs, respectively. The results of the GATE simulations demonstrated that values can be characterized as functions of the diameter of phantoms, kVp and mAs so that we may be able to optimize the CT parameters in clinical applications
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한국학술지인용색인(NRF)
