In phantom assessment of superficial doses under TomoTherapy irradiation |
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| Institution: | 1. Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, Italy;2. Azienda Ospedaliero Universitaria Careggi, Firenze, Italy;3. INFN-Dipartimento di Ingegneria Industriale, Università di Roma “Tor Vergata”, Roma, Italy;1. Department of Basic Medical Sciences, Faculty of Health Sciences, Ghent University, Ghent, Belgium;2. Department of Mathematical Modeling, Statistics, and Bioinformatics, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium;3. National Institute for Applied Statistics Research Australia, University of Wollongong, Wollongong, New South Wales, Australia;4. Department of Data Analysis, Faculty of Psychology and Educational Sciences, Ghent University, Ghent, Belgium;6. Division of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany;5. Translational Radiobiology Group, Institute of Cancer Sciences, Radiotherapy Related Research, Christie Hospital NHS Trust, University of Manchester, Manchester, United Kingdom;1. Department of Radiation Oncology, ERESA, Hospital General Universitario de Valencia (CHGUV), Spain;2. Department of Radiophysics, ERESA, Hospital General Universitario de Valencia (CHGUV), Spain;3. Department of Dermatology, Hospital General Universitario de Valencia (CHGUV), Spain;1. Department of Medical Physics, San Raffaele Scientific Institute, Milan, Italy;2. Department of Radiotherapy, San Raffaele Scientific Institute, Milan, Italy;3. Department of Urology, San Raffaele Scientific Institute, Milan, Italy |
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| Abstract: | PurposeAim of this work is the assessment of build-up and superficial doses of different clinical Head&Neck plans delivered with Helical TomoTherapy (HT) (Accuray, Sunnyvale, CA). Depth dose profiles and superficial dose points were measured in order to evaluate the Treatment Planning System (TPS) capability of an accurate dose modeling in regions of disequilibrium. Geometries and scattering conditions were investigated, similar to the ones generally encountered in clinical treatments.MethodsMeasurements were performed with two dosimeters: Gafchromic® EBT3 films (Ashland Inc., Wayne, NJ) and a synthetic single crystal diamond detector (PTW-Frieburg microDiamond, MD). A modified version of the Alderson RANDO phantom was employed to house the detectors. A comparison with TPS data was carried out in terms of dose difference (DD) and distance-to-agreement (DTA).ResultsDD between calculated data and MD measurements are within 4% even in points with high spatial dose variation. For depth profiles, EBT3 data show a DDmax of 3.3% and DTAmax of 2.2 mm, in low and high gradient regions, respectively, and compare well with MD data. EBT3 superficial points always results in measured doses lower than TPS evaluated ones, with a maximum DTA value of 1.5 mm.ConclusionsDoses measured with the two devices are in good agreement and compare well with calculated data. The deviations found in the present work are within the reference tolerance level, suggesting that the HT TPS is capable of a precise dose estimation both in superficial regions and in correspondence with interfaces between air and PMMA. |
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| Keywords: | TomoTherapy Superficial dosimetry Radiochromic films Diamond detector |
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