Dosimetry for Quantitative Analysis of the Effects of Low-Dose Ionizing Radiation in Radiation Therapy Patients

We have developed and validated a practical approach to identifying the location on the skin surface that will receive a prespecified biopsy dose (ranging down to 1 cGy) in support of in vivo biological dosimetry in humans. This represents a significant technical challenge since the sites lie on the pa-tient’s surface outside the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery, and TLDs were used for validation on phan-toms and for confirmation during patient treatment. In the developmental studies, the Monte Carlo simulations consis-tently underestimated the dose at the biopsy site by approxi-mately 15 % (of the local dose) for a realistic treatment con-figuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinica