Assessment of computed tomography dose index (CTDI) using the platform GEANT4/GATE

Absorbed dose during a CT exam can be estimated by the computed tomography dose index (CTDI). The aim of this study is to validate a simulated CTDI with measured data for a 16-slice CT system. To measure the CTDI we have used an ion chamber, electrometer and two polymethylmethacrylate (PMMA) phantoms (head and body). GATE (GEANT4 Application for Tomographic Emission) platform is a Monte Carlo code for medical physics applications, especially dosimetry studies. CTDI and CTDIw were recorded to compare simulated results for different X-ray tube currents and voltages with experimental data at different positions in the phantom. The results obtained for all conditions applied show a difference less than 2.6% and 4.3% for head and body phantom, respectively. It was demonstrated that GATE is a good tool to simulate CTDIw values and to study of the influence of tube current and voltage on the absorbed dose.