Characterization of Detector-Specific Correction Factors for Optically Stimulated Luminescence Dosimeter-Based Surface Dosimetry
Abstract
Purpose
While optically stimulated luminescence dosimeters (OSLD) offer advantages in reusability and efficiency, they overestimate the surface dose due to thick effective point of measurement. The aim of this study is to investigate the detector-specific correction factor for two commercial OSLDs to correct surface dose overestimation in breast radiotherapy plans.
Methods
This study was conducted using two OSLD systems, MyOSLchip (RadPro International GmbH, Germany) and nanoDot (Landauer, USA). Gafchromic EBT4 film (Ashland, USA) was used as reference for surface dose measurement. Surface dosimetry was performed on a female anthropomorphic phantom. 3D-conformal radiotherapy, Field-in-Field technique, intensity-modulated radiotherapy, and volumetric-modulated arc therapy plans were generated for whole breast with a prescription dose of 2 Gy per fraction. OSLD and film measurements were performed at six positions on the phantom surface, and repeated three times per treatment technique. The detector-specific correction factor was derived individually for MyOSLchip (CFmyosl) and for nanoDot (CFnano), using linear least-squares fitting of film responses against OSLD responses. The relative dose difference between film and OSLD were calculated before and after applying CF to OSLD readings.
Results
Compared to EBT4 film, myOSLchip and nanoDot overestimate surface dose by 17.70%-46.71% and 7.69%-21.48%, respectively, depending on measurement position and treatment technique. CFmyosl and CFnano values were calculated as 0.73 and 0.88, respectively. After applying CFmyosl and CFnano, the relative dose difference between EBT4 film and corrected OSLDs was reduced, ranging from -8.88% to 14.98% for myOSLchip and from -11.28% to 9.07% for nanoDot.
Conclusion
Detector-specific correction factors were effective to mitigate overestimation of OSLD in surface dosimetry. The proposed factors may be easily applied in clinics. Additional correction methods incorporating beam incidence angle, field size, and other factors affecting the detector response are needed to further reduce the dose difference ratio between surface dose and corrected OSLD.