X-ray surface dose measurements using TLD extrapolation

Abstract

Surface dose measurements in therapeutic x-ray beams are of importance in determining the dose to the skin of patients undergoing radiotherapy. Measurements were performed in the 6-MV beam of a medical linear accelerator with LiF thermoluminescence dosimeters (TLD) using a solid water phantom. TLD chips (surface area 3.17x3.17 cm2) of three different thicknesses (0.230, 0.099, and 0.038 g/cm2) were used to extrapolate dose readings to an infinitesimally thin layer of LiF. This surface dose was measured for field sizes ranging from 1X 1 cm2 to 40 x 40 cm2. The surface dose relative to maximum dose was found to be 10.0% for a field size of 5X5 cm2, 16.3% for 10x10 cm2, and 26.9% for 20x20 cm2...