Exhibit Hall | Forum 7
Purpose: While OSLD and TLD have been studied in carbon beams, the details of a high-precision framework for dose measurements have not been established due to the variable dose response by LET, and the dosimeters have not been routinely used for carbon dosimetry. This research characterized the dosimeter correction factors for dose calculation in a therapeutic carbon beam at CNAO.
Methods: The carbon linearity, fading, beam quality, and depletion (OSLD only) correction factors were determined for OSLD nanoDots and TLD-100 powder capsules used by the IROC QA Center, and were compared to the correction factors used for photon beams.
Results: The OSLD and TLD linearity were statistically different between photon and carbon beams up to 7 Gy (linear regression, p<<0.05). The OSLD and TLD carbon fading corrections were not statistically different from photon beam corrections (linear regression, p>0.05). The OSLD and TLD carbon beam quality corrections (kQ) were compared to beam range, LET, and microdosimetric values. kQ could be characterized by a third order polynomial based on the distance from measurement point to the practical beam range (R10), similar to the Rres value used in carbon beam calibration. This fit applied to irradiations in both pristine and spread-out Bragg peaks. This fit accommodates the differences from LET response without requiring direct calculation of LET. The OSLD depletion was determined to be statistically different between photon and carbon beams over 60 sequential readings, but not statistically different over the course of the standard 5 sequential readings (univariate analysis of variance, p<<0.05; p>0.05).
Conclusion: OSLD and TLD were characterized for high-precision carbon dosimetry. This characterization of passive detector response will facilitate easy second-checks and remote audits of carbon beam output.
Funding Support, Disclosures, and Conflict of Interest: This work is supported by a grant from the National Cancer Institute.
Not Applicable / None Entered.