Modeling of couch transmission in the RayStation treatment planning system |
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| Institution: | 1. Medical Physics Department, AUSL 4 Teramo – Hospital G. Mazzini, Piazza Italia 1, 64100 Teramo (TE), Italy;2. Post-graduate School in Medical Physics, University of L’Aquila, Piazzale Salvatore Tommasi 1, 67100 L’Aquila (AQ), Italy;1. Department of Radiology, Universitair Ziekenhuis, Gent, Belgium;2. Department of Gastroenterology, Universitair Ziekenhuis, Gent, Belgium;3. Department of Vascular and interventional Radiology, Universitair Ziekenhuis, Gent, Belgium;1. Royal Brisbane and Women’s Hospital, Butterfield Street, Herston, QLD 4029, Australia;2. Genesis Cancer Care Queensland, 1/40 Chasely Street, Auchenflower, QLD 4066, Australia;3. School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia;1. Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, the Netherlands;1. Department of Physics, Duke University, Durham, NC 27708, USA;2. Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA;1. Servicio de Radiofísica y Protección Radiológica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, Spain;2. Servicio de Oncología Radioterápica, Consorcio Hospitalario Provincial de Castellón, Castellón de la Plana, Spain;3. Departamento de Oncología, Hospital General Universitario Gregorio Marañón Madrid, Spain;4. Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain;5. Facultad de Medicina, Universidad Complutense de Madrid, Spain;6. Instituto de Técnicas Energéticas, Universidad Politécnica de Cataluña, Barcelona, Spain;7. Facultad de Medicina, Universidad Cardenal Herrera-CEU, Castellón de la Plana, Spain |
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| Abstract: | PurposeTo present our methods and results regarding the modeling of a carbon fiber couch (Varian Exact IGRT) in the RayStation treatment planning system (TPS).MethodsThree geometrical-models (GMs) were implemented in the TPS to represent the three different regions of the couch (thick, medium and thin). The materials and densities of each GM component were tuned to maximize the agreement between measured and calculated attenuations. Moreover, a couch computed-tomography (CT) scan was acquired and dosimetrically compared with the GMs. For validation, plan-specific quality assurance (QA) of VMAT plans (TG-119 cases, 5 prostate and 5 H&N clinical cases) was performed by comparing measured dose distributions with doses computed with and without including the GMs in the TPS.ResultsCouch attenuations up to 4.3% were measured (energy: 6MV). Compared to couch CT, GMs could be modified to optimize the agreement with measurements and reduce dependence on the dose grid resolution. For both couch CT and GM, absolute deviations between measured and calculated attenuations were within 1.0%. When including the GMs in plan-specific QA, global 2%/2 mm γ-pass rates showed an average improvement of 4.8% (p-value < 0.001, max +18.6%). The couch reduced the mean dose to targets by up to 2.4% of the prescribed dose for prostate cases and up to 1.4% for H&N cases.ConclusionsRayStation accurately considers the implemented couch GMs replicating measured attenuations within an uncertainty of 1.0%. Materials and densities are proposed for the Varian Exact IGRT couch. The results obtained justify introducing couch GMs in clinical routine. |
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| Keywords: | Couch modeling Carbon fiber couch Varian IGRT couch RayStation treatment planning system |
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