MO‐FF‐A1‐05: Quantitative Radiation Therapy Dosimetry Using Reusable Storage Phosphor KCl:Eu2+

Purpose: To investigate the quantitative use of a novel [formula omitted] dosimeter for radiation therapy dosimetry. Methods and Materials: Cylindrical [formula omitted] dosimeters 7 mm in diameter and 1 mm thick were fabricated. Dosimetric properties were studied with an in‐house optical readout system after irradiation by a linear accelerator. The overall experimental uncertainty was estimated to be within ±2.5%. Results: 1) [formula omitted] showed satisfactory radiation hardness. There was no significant change in the stimulation spectra after irradiation up to 200 Gy when compared to a fresh sample, indicating that this material could be reused at least 100 times if 2 Gy per use was assumed, e.g., for a patient‐specific IMRT QA; 2) [formula omitted] exhibited supra‐linear response to dose after irradiation from zero cGy to 800 cGy; 3) After x‐ray irradiation the PSL signal decayed with time and eventually reached a plateau (0.1% per hour) after 12 hours, which was significantly better than a commercial CR (computed radiography) plate; 4) The sensitivity of the dosimeter was independent of the dose rate ranging from 15 cGy/min (underneath a MLC) to 1000 cGy/min; 5) The sensitivity showed no energy dependence for either open x‐ray or megavoltage electron fields; 6) Over‐response to low‐energy scattered photons was comparable to radiographic film, e.g., a Kodak EDR2 film. Reduction of dosimeter thickness to tens of microns would minimize the energy dependence. Conclusion: We have demonstrated that [formula omitted] dosimeters have many desirable dosimetric characteristics and that [formula omitted] has great potential to replace [formula omitted] as the primary storage phosphor material for radiation therapy dosimetry. In the future, a large‐area [formula omitted] based CR plate created using modern thin film techniques would provide a reusable, quantitative, high‐resolution two‐dimensional dosimeter with minimal energy dependence. This work is supported in part by an NIH grant CA131690.