Naomasa Narihiro    Department   Kawasaki University of Medical Welfare  ,    Position   Associate Professor
Language	English
Title	Calculation of oblique surface dose in high energy X-ray therapy
Conference	The European Society of Radiology (ESR)2020
Conference Type	International society and overseas society
Presentation Type	Poster notice
Lecture Type	General
Publisher and common publisher	◎Naomasa Narihiro, Masataka Oita, Yoshihiro Takeda
Date	2020/07/15
Venue (city and name of the country)	vienna, Austria WEB
Summary	Purpose Understanding the skin dose of high energy x-ray therapy is essential in predicting the occurrence of radiation damage. When the incident is oblique to the skin surface, the skin dose increases. The oblique surface dose was measured using a small OSL dosimeter of the Optically Stimulated Luminescence Dosimeter (OSL Dosimeter). A calculation formula that can easily calculate the oblique surface dose was derived from the measured values. Materials and Methods Sixty-six small OSL dosimeters (nanoDot, Nagase Landauer, LTD.) were used in this study. First, the variation and angular dependence of the OSL dosimeters were evaluated with 4MV X-ray beams. Next, the OSL dosimeters embedded in the surface of the SOLID WATER phantom were irradiated with changing the irradiation field size and incidence angle. The absorbed dose per monitor unit (MU) of the OSL dosimeters were obtained from the measured values, and a calculation formula that can simply estimate the oblique surface dose was derived. Results The coefficient of variation of those 66 nanoDot OSL dosimeters was a minimum value of 0.33% and a maximum value of 1.71%. The angular dependence was 1.37, the maximum dose ratio for each angle to 0 degrees. A calculation formula that can calculate the oblique surface dose from the measured values was derived. Conclusion A calculation formula that can simply estimate the oblique surface dose was derived. This will help to predict the occurrence of radiation skin disorders.