Author: Jeremy S. Bredfeldt, Daniel W. Cail, Maria A. Czerminska, Cindy I. Hancox, David Hu, Benjamin Karasko, Claire Keun Sun Park π¨βπ¬
Affiliation: Department of Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Brigham and Women's Hospital, Brigham and Womenβs Hospital and Dana Farber Cancer Institute, Harvard Medical School π
Purpose: To develop a robust clinical protocol for in vivo dosimetry in radiotherapy using the myOSLchip Optically Stimulated Luminescent Dosimeter (OSLD) system by performing characterization and evaluating its application across diverse clinical scenarios.
Methods: A retrospective analysis of 78 clinical cases utilizing OSLD measurements was conducted, supplemented by a Rando Phantom case study of a 10-week pregnant patient. Dosimeter sensitivity loss was examined post-erasure for low- and high-dose exposures. Signal degradation following multiple readings and a re-read factor accounting for dose dependency and signal depletion were evaluated experimentally. A dose conversion equation was derived, based on TG-191 recommendations. The proposed clinical protocol stratifies cases into two categories: low-dose and high-dose applications, further categorized into pacemaker/Implanted Cardiac Defibrillator (ICD) monitoring and bolus skin measurements.
Results: For pacemaker/ICD cases, mean dose (range) was 14.90 (0.14β161.92) cGy, while bolus skin applications showed a mean dose (range) of 241.34 (209.14β313.91) cGy. For the pregnant patient, the OSLD-measured dose was 0.08 cGy, adhering to TG-36 guidelines. The protocol designates workflows for low-dose (<1 cGy) cases, such as pregnancy and personal dose monitoring. High-dose applications including pacemaker/ICD management (TG-203 compliant) and bolus skin applications, employing a universal re-read factor (1.017) in dose conversion to facilitate re-use for high-dose applications without compromising dosimetric accuracy, provided the residual dose remained significantly lower than the expected dose. The approach is adaptable to Total Body Irradiation (TBI) skin measurements (200β300 cGy per fraction).
Conclusion: This study establishes a comprehensive protocol for in vivo dosimetry with the myOSLchip system. System characterization and incorporation of a universal re-read factor enhances accuracy and reliability in high dose measurements, offering superior precision compared with conventional in vivo dosimetry systems and broad applicability across diverse clinical scenarios.