Evaluation of the Attenuation Rate for Clinical Application of a Flexible Skin Dosimeter in Radiotherapy

During radiotherapy, some patients owing to the variability in skin sensitivities, may experience adverse skin reactions for doses at which other patients are asymptomatic. Hence, when abnormal symptoms appear on a patient’s skin, the etiology should be verified. Accordingly, a surface dosimeter on the skin can help ascertain whether accurate doses are irradiated. Furthermore, surface doses are measured in the field junction gaps during craniospinal irradiation or during large-area radiotherapy to avoid adverse reactions due to cumulative skin doses from multiple beams. However, the point dose measurement errors of surface dosimeters exceed approximately 10% and have low-positional accuracies because the attachment sites are approximated with the help of the naked eye. Moreover, accurate information on field junction gaps cannot be obtained. Therefore, in clinical practice, a flexible array dosimeter is required as it can measure the dose distribution on the body surface by adapting its shape to the body curvatures. In this study, we implemented a flexible array dosimeter and, based on its constituent materials, evaluated the attenuation rate associated with its use. A polyester (PET) film was used as the underlying substrate. HgI2 and PbI2 photoconductors were used for their good performances in films. Furthermore, the measurement accuracy was verified through comparisons with Monte Carlo simulation outcomes. The resulting PET film had an attenuation rate of 2.22% at a 50-µm thickness. At the minimum material thickness of 25 µm, the attenuation rates for HgI2 and PbI2 were 4.69% and 5.72%, respectively. Further research is needed to fabricate HgI2-based digital skin dosimeters with a thickness under 25 µm. Radiation detection and pixel resolution should be evaluated to accurately confirm the field junction gap.