Monte Carlo Simulation of the Computed Tomography Dose Index (CTDI) Using GATE
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ADIOBIOLOGY, ECOLOGY AND NUCLEAR MEDICINE
Monte Carlo Simulation of the Computed Tomography Dose Index (CTDI) Using GATE M. Mkimela, b, *, R. El Baydaouia, M. R. Mesradia, Z. Tahiric, K. Talasmatd, A. Halimia, M. Krima, E. Saada, and A. Hilalia aLaboratory of health sciences and technologies, High Institute of Health Sciences, Hassan 1st University Settat, Settat, Morocco b
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Department of radiology public hospital, Settat, Morocco Laboratory of radiation protection and hybrid imaging, faculty of medicine and pharmacy, Rabat, Morocco d National Center for Energy Science and Nuclear Techniques Rabat, Rabat, Morocco * e-mail: [email protected] Received November 2, 2019; revised March 3, 2020; accepted March 10, 2020
Abstract—This work relates to the study and characterization of the CTDI (Computed Tomography Dose Index) for the 16 slices CT scanner. The CTDI has been simulated with the Monte Carlo code GATE for PMMA (polymethylmethacrylate) digital phantoms of various diameters (1–50 cm) at various kVp (80, 110, 130) and mAs (100, 200, 300, 400 mAs) levels. After using a High-Performance Computing (HPC) station, a good agreement was observed (less than 1.18% for head phantom and 1.85% for body phantom for all applied voltages) between simulations and experimental measurements with standard PMMA phantoms. Results of simulations demonstrated the following. Firstly, GATE is an adapted tool to estimate CTDI values and can be used to optimize CT parameters in clinical applications. Secondly, Monte Carlo simulation may be able to estimate the absorbed dose when the CTDI method has limitations (use of homogeneous standards cylindrical phantom, the dose measurement in air not in tissue). Keywords: CT, CTDI, PMMA, GATE, Monte Carlo DOI: 10.1134/S1547477120060084
1. INTRODUCTION Computed tomography is a reference technique in medical imaging that can help practitioner in the diagnostic of many pathologies. CT examination represents 5% of all X-ray examinations but for the total medical dose received it represents between 40 to 67% [1] and the use of CT continues to grow by 10–15% per year [2]. In Morocco, an increase in the number of CT examinations has been observed over the last few years. However, this technique of medical imaging is the most irradiating if compared with other techniques. It can deliver a dose of 50 to 500 times more than a standard radiological examination [3]. This level of exposure to ionizing radiation in CT may be responsible for a long-term carcinogenesis process (stochastic effect) [4, 5]. In fact, the determination of diagnostic reference levels (DRL) [6–8] is a good tool to optimize the dose delivered to patients in medical imaging. Currently in Morocco, there are no DRLs in CT exam. CTDI is the major factor to determine the DRLs in CT exam; it represents the absorbed dose along the longitudinal CT scanner axis, during a single X-ray tube rotation [9]. This work is a part of a project in our laboratory, which will process the optimization of the dose delivered to patients in CT using GATE
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