Dose calculation validation of a convolution algorithm in a solid water phantom |
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| Institution: | 1. Medical Physics Department, University Hospital, Lille, France;2. Medical Physics Department, Centre Bordet, Brussels, Belgium;1. Radiation Application Research School, Nuclear Science and Technology Research Institute (NSTRI), Tehran, Iran;2. Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;3. Medical Physics Department, School of Medicine, Iran University of Medical Sciences, P.O. Box: 14155-6183 Tehran, Iran;1. Cancer Center of Southeastern Ontario, 25 King Street West, Kingston, Ontario K7L 5P9, Canada;2. Simcoe Muskoka Regional Cancer Centre, Royal Victoria Regional Health Centre, 201 Georgian Drive, Barrie, Ontario L4M 6M2, Canada;3. R.S. McLaughlin Durham Regional Cancer Centre, Lakeridge Health Oshawa, 1 Hospital Court, Oshawa, Ontario, L1G 2B9, Canada;4. Odette Cancer Centre, Sunnybrook Health Sciences Centre, T-wing 2075 Bayview Avenue TG 260, Toronto, Ontario M4N 3M5, Canada;5. Princess Margaret Cancer Centre, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2C1, Canada;6. Juravinski Cancer Centre – Hamilton Health Sciences, 699 Concession Street, Hamilton, Ontario L8V 5C2, Canada;1. Department of Medical Imaging, Nimes University Hospital, Univ Montpellier, Medical Imaging Group Nimes, EA 2992, France;2. Department of Medical Physics, CHU Nimes, Univ Montpellier, Montpellier, France;3. ISERIS Imagerie médicale, 25 rue de Clémentville, Montpellier, France;1. Fujita Health University, Faculty of Radiological Technology, School of Health Sciences, 1-98 Dengakugakubo Kutsukake-cho, Toyoake, Aichi 470-1192, Japan;2. Nagoya Proton Therapy Center, Nagoya City University West Medical Center, 1-1-1 Hirate-cho Kita-ku, Nagoya, Aichi 462-8508, Japan;3. Nagoya University Hospital, 65 Tsuruma-cho Shouwa-ku, Nagoya, Aichi 466-8560, Japan;1. Politecnico di Milano, Dipartimento di Energia, via La Masa 34, Milano, Italy;2. INFN-Laboratori Nazionali di Legnaro, viale dell’Università 2, Legnaro, Padova, Italy;3. INFN-sezione di Milano, via Celoria 16, Milano, Italy;4. INFN-Laboratori Nazionali del Sud, via S. Sofia 62, Catania, Italy;5. Dipartimento di Fisica “E. Pancini” Università degli Studi di Napoli Federico II & INFN-sezione di Napoli, Complesso Universitario di Monte S. Angelo, 80126 Napoli, Italy |
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| Abstract: | PurposeThe dose calculated using a convolution algorithm should be validated in a simple homogeneous water-equivalent phantom before clinical use. The dose calculation accuracy within a solid water phantom was investigated.MethodsThe specific Gamma knife design requires a dose rate calibration within a spherical solid water phantom. The TMR10 algorithm, which approximates the phantom material as liquid water, correctly computes the absolute dose in water. The convolution algorithm, which considers electron density miscalculates the dose in water as the phantom Hounsfield units were converted into higher electron density when the original CT calibration curve was used. To address this issue, the electron density of liquid water was affected by modifying the CT calibration curve. The absolute dose calculated using the convolution algorithm was compared with that computed by the TMR10. The measured depth dose profiles were also compared to those computed by the convolution and TMR10 algorithms. A patient treatment was recalculated in the solid-water phantom and the delivery quality assurance was checked.ResultsThe convolution algorithm and the TMR10 calculate an absolute dose within 1% when using the modified CT calibration curve. The dose depth profile calculated using the convolution algorithms was superimposed on the TMR10 and measured dose profiles when the modified CT calibration curve was applied. The Gamma index was better than 93%.ConclusionsDose calculation algorithms, which consider electron density, require a CT calibration curve adapted to the phantom material to correctly compute the dose in water. |
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| Keywords: | CT calibration curve Electron density Solid water phantom Dose calculation algorithm |
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