Abstract
The present work uses the Eclipse treatment planning system (TPS) to investigate the accuracy of skin dose calculations. Micro‐MOSFETs (metal oxide semiconductor field effect transistors) were used to measure skin dose for a range of irradiation conditions (open fields, physical wedges, dynamic wedges, various source‐to‐surface distances) for 6‐MV and 10‐MV beams, and the results were compared with the calculated mean dose to a “skin” structure 2 mm thick for semi‐cylindrical phantoms (representative of a neck or breast). Agreement between the calculated and measured skin dose values was better than ±20% for 95% of all measured points (6‐MV and 10‐MV X‐ray spectra alike). For a fixed geometry, the TPS correctly calculated relative changes in dose, showing that minimization of skin dose in intensity‐modulated radiation therapy will be effective in Eclipse.PACS numbers: 87.53.Bn, 87.53.Dq, 87.66.Pm, 87.66.Xa
Highlights
Skin dose can be the limiting factor in radiation therapy treatments, and it is a fairly common cause of interruptions in radiation therapy treatment
Skin dose is of particular concern when intensity-modulated radiation therapy (IMRT) is used to treat head-and-neck cancer.[1]. The use of thermoplastic head-and-neck immobilization devices increases skin dose,(1,2) and the use of multiple tangential beams can increase it
The objective of the present work was to evaluate the accuracy of skin dose calculations in the Eclipse treatment planning system (TPS) (Varian Medical Systems., Palo Alto, CA) for a wide range of irradiation conditions
Summary
Skin dose can be the limiting factor in radiation therapy treatments, and it is a fairly common cause of interruptions in radiation therapy treatment. Skin dose is of particular concern when intensity-modulated radiation therapy (IMRT) is used to treat head-and-neck cancer.[1] The use of thermoplastic head-and-neck immobilization devices increases skin dose,(1,2) and the use of multiple tangential beams (common in IMRT treatments) can increase it. Despite the clinical importance of skin dose, the literature contains little detail concerning the expected accuracy of skin dose calculations. Fraas et al[4] (American Association of Physicists in Medicine Task Group 53) reported the collective expectations of the Radiation Therapy Committee Task Group members for pass–fail criteria in the buildup region during the commissioning of a treatment planning system (TPS) as 20% of the central ray normalization dose for regular open fields, increasing to 40% for source-to-surface distance (SSD) variations, and 50% for wedged fields. Using thermoluminescent dosimeters and parallel-plate ionization chambers, Mutic and Low[6] found that a tomotherapy TPS underestimated doses to the surface and first few millimeters below the surface by approximately 15%
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