Skin dose measurement by using ultra-thin TLDs

The treatment schedule for radiation therapy is often interrupted because of complicated skin reactions. Quantitative information relating beam parameters and skin reactions will be helpful. Measurements were performed for 6–15 MV photons and 6–21 MeV electrons with ultra thin TLD films (GR-200F, surface area 0.5×0.5 cm2, nominal thickness 5 mg cm−2). The skin doses for various field sizes, ranging from 10×10 to 40×40 cm2, and various incident angles of beam from 0° to 80° were measured. The ratios of skin dose to maximum dose in phantom for 10×10 cm2 are 16.10±0.68%, 14.03±1.04% and 10.59±0.64% for 6, 10 and 15 MV, respectively. Such ratios increase with a larger field size. For electrons the ratios are 72.59±1.72%, 78.52±2.99%, 78.89±2.86%, 86.08±2.62%, 87.75±1.94% and 86.33±3.09% for 6, 9, 12, 15, 18 and 21 MeV, respectively. They also increase with a larger size. The oblique factors also increase with larger incident angle.