Author: Brett G Erickson, Joseph P. Kowalski, Xinyi Li, Qiuwen Wu, Sua Yoo 👨🔬
Affiliation: Duke University, Mayo Clinic - Department of Radiation Oncology, Duke University Medical Center 🌍
Purpose: Characterization and commissioning of the BeO-based myOSLchip system was performed (per TG191) to assess its feasibility as a full replacement for the recalled Landauer aluminum oxide OSL in vivo dosimetry system.
Methods: OSL irradiations were performed using a Varian TrueBeam linear accelerator and a bolus/solid water phantom at depths of 10 cm (photons) and dmax (electrons). Correction factor and clinical measurements were performed 24 hours and 30 minutes post-irradiation, respectively. Correction factors were determined for fading, linearity, beam quality, and angular dependence in accordance with TG191. Additionally, element sensitivity variation as a function of accumulated dose and signal loss per reading were also measured. Clinical performance was assessed for TSET, TBI, clinical electrons, and out-of-field measurements and compared against that of nanoDots.
Results: Linearity correction factors ranged from -0.5% to +3% for dose levels spanning 0.1 to 20 Gy. Beam quality correction factors (relative to 6 MV) ranged from -4.5% (2.5FFF) to +4.5% (15MV) for photon beams and +1.9% (6 MeV) to +4.3% (20 MeV) for electron beams. An average (µ) signal loss per reading of -2.13% ±0.20% was measured, however greater signal loss was observed in the first reading (µ=-2.6%±0.46%). A decline in element sensitivity relative to baseline was observed from 0-15 Gy cumulative dose (µ=-1.98%±0.55%), with negligible further deterioration from 15-32 Gy (µ=-2.38%±0.85%). Post-irradiation, there was a transient OSL signal that decayed with a half-life of 1.8 min; this enhancement was +5% at t+5m and +1% at t+15m relative to 24 hours. Dosimeter response was not dependent on average dose rate in the range of 100-2500 MU/min. Clinically, equivalent or superior performance compared with nanoDots was observed across all tested techniques.
Conclusion: myOSLchip is a robust and convenient in vivo dosimetry system that is capable of serving as a complete replacement for the Landauer microStar/nanoDot system.