SU‐E‐T‐229: Clinical Implementation and Validation of Optically Stimulated Luminescence Dosimeters (OSLDs) for Radiotherapy Dosimetry

Abstract

Purpose: To experimentally validate and clinically implement a new OSLDs system containing Al2O3: C for measuring skin dose for the patients undergoing radiotherapy treatment. Methods and materials: The calibration measurements of the commercially available OSLDs were performed in a solid water phantom using therapeutic photon and electron beams. All measurements were carried out in a standard clinical set‐up using 100 cm SSD, 10 ×10 cm2 field size, and dmax depth for each photon and electron beam energies. In total, 100 OSLDs were irradiated with the same dose. Inter‐OSLD response variation was calculated by taking the difference between the average value and each OSLD response. A simple optical bleaching system was applied for the OSLDs using a regular fluorescent light. The accuracy of the OSLD measurement was assess by comparing with the expected ion chamber reading and MOSFET measurements carried out under the identical condition in patients. Results: In the phantom study, the overall inter‐OSLD response variations were 2.8% and 6.4% for 10 MV photon and 10MeV e‐beam, respectively. OSLD response variation between the different energies was clinically insignificant. Optical bleaching took less than 2 hours while using fluorescent light with residual signal of less than 0.3%. For the patient study, the OSLDs reading were comparable to MOSFET measurement. Summary and Discussion: Our preliminary results using OSLDs show good agreement with clinically used MOSFET measurement in patients. Screening of general purpose OSLDs is highly recommended before using in patient. The OSLDs are accurate, can be readout/use multiple times, single readout does not anneal the chip, and more importantly it is convenient to put in the patientˈs body. Further validation and clinical implementation of OSLDs for all therapeutic‐beams as well as on‐board‐imaging system will be advantageous for more accurate clinical dosimetry for advanced radiotherapy procedures such as SBRT, IGRT.