37 Simulation of CTDI using GATE for 2, 16, 64 slices CT system

Abstract

Introduction Since the introduction of the computed tomography in the clinical application in the 1971’s, the CT has revolutionized the medical imaging techniques. It well known that Doses from CT examinations are higher if we compared with other medical imaging modalities. Many studies considered that CT may be responsible of radiation-induced diseases, especially carcinogenic processes so it’s important to justify and optimize the radiation dose during CT procedures. In this work, we aimed to estimate the computed tomography dose index (CTDI) using the Monte Carlo code Geant4 Application for Tomographic Emission (GATE) for 3 CT acquisition system. Methods CTDI is the most important indicator of the CT radiation dose. We have evaluated the CTDI with the experimental method using a pencil ion chamber and two phantoms PMMA (PolyMethylMethAcrylate) for simulating head and body. A code based on Monte Carlo simulation named GATE was used for modeling CT geometry for the simulation method. A comparison between simulated and measured CTDI was established for the 3 CT system. Result Results of the simulation are presented and good agreements are observed between measured and simulated CTDI. For dual slices (less than 1.18% for head phantom and l.85% for body phantom for all applied voltages). For 16 slices (less than 3.7% for head phantom and 3.8% for body phantom for all applied voltages). For 64 slices (less than 1.7% for head phantom and 2% for body phantom for all applied voltages). These differences observed can be geometry explained by the difficulty to model a precise geometry and the random errors in the simulated CTDI. We demonstrated that the CTDI values can be characterized as functions of the voltage (kVp), the current (mAs) and diameter of phantoms. Conclusion Based on these results, it is possible to optimize the CT parameters in clinical applications using the Monte Carlo code GATE.