Organ doses from a proton gantry-mounted cone-beam computed tomography system characterized with MCNP6 and GATE |
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| Institution: | 1. Medical Radiation Physics, Department of Physics, Stockholm University, Stockholm, Sweden;2. Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden;3. The Skandion Clinic, Uppsala, Sweden;1. High-Temperature Superconducting Wire Group, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan;2. Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan;1. School of Energy Systems, Lappeenranta University of Technology, Lappeenranta, Finland;2. Department of Electronics and information systems, Ghent University, Ghent, Belgium;1. Department of Medical Physics and Biomedical engineering, School of Medicine, Tehran University of Medical Science, Tehran, Iran;2. Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran;3. Department of Radiology, Johns Hopkins University, Baltimore, MD, USA;4. Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, MD, USA;5. Electrical Engineering Department, Sharif University of Technology, Tehran, Iran;6. Department of Nuclear Medicine, Vali-Asr Hospital, Tehran University of Medical Sciences, Tehran, Iran;1. Institute of Medical Physics, School of Physics, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia;2. Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Australia;3. Ingham Institute for Applied Medical Research, Sydney, NSW, Australia;4. Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark;5. Institute of Clinical Research, University of Southern Denmark, Odense, Denmark;6. Illawarra Cancer Care Centre, Wollongong, NSW, Australia;7. Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia;8. South Western Sydney Clinical School, University of New South Wales, Sydney, NSW, Australia |
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| Abstract: | PurposeTo determine organ doses from a proton gantry-mounted cone-beam computed tomography (CBCT) system using two Monte Carlo codes and to study the influence on organ doses from different acquisition modes and repeated imaging.MethodsThe CBCT system was characterized with MCNP6 and GATE using measurements of depth doses in water and spatial profiles in air. The beam models were validated against absolute dose measurements and used to simulate organ doses from CBCT imaging with head, thorax and pelvis protocols. Anterior and posterior 190° scans were simulated and the resulting organ doses per mAs were compared to those from 360° scans. The influence on organ doses from repeated imaging with different imaging schedules was also investigated.ResultsThe agreement between MCNP6, GATE and measurements with regard to depth doses and beam profiles was within 4% for all protocols and the corresponding average agreement in absolute dose validation was 4%. Absorbed doses for in-field organs from 360° scans ranged between 6 and 8 mGy, 15–17 mGy and 24–54 mGy for the head, thorax and pelvis protocols, respectively. Cumulative organ doses from repeated CBCT imaging ranged between 0.04 and 0.32 Gy for weekly imaging and 0.2–1.6 Gy for daily imaging. The anterior scans resulted in an average increase in dose per mAs of 24% to the organs of interest relative to the 360° scan, while the posterior scan showed a 37% decrease.ConclusionsA proton gantry-mounted CBCT system was accurately characterized with MCNP6 and GATE. Organ doses varied greatly depending on acquisition mode, favoring posterior scans. |
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