An Investigation of the Dosimetric Uncertainties in the myOSLchip System: The Impact of Contributing Factors on Measurement Accuracy.

Abstract

The use of in vivo dosimetry (IVD) is integral to radiation oncology, particularly for treatments involving custom boluses or superficial electron lesions. In this report, the "myOSLchip" system, comprising beryllium oxide (BeO)-based optically stimulated luminescent chips and hand-held readers, was evaluated for clinical use. Each 4.7 × 0.5 mm chip, housed in plastic with an effective measurement point 1 mm below the surface, was calibrated under standard 6 megavoltage (MV) photon conditions using a 10 × 10 cm² field at 100 cm SSD and 1.5 cm depth in solid water. Calibration factors were assessed for energy dependence, dose linearity, time to readout, repeat measurements, and angular dependence. Results showed high measurement accuracy and linearity up to 10 Gy, with separate calibration factors needed per reader. The chips exhibited significant under-response at low energies (down to 16.82 keV), but minor variation in the megavoltage range for both photons and electrons. Repeat use showed an average signal loss of 1.2% after the first bleaching and 0.35% per subsequent cycle. A stable readout required at least four hours post-irradiation, with earlier readings (30-60 minutes) showing 2-3% error. No angular dependence was observed. With appropriate calibration and consideration of these factors, the myOSLchip system delivers dose measurements within the clinically accepted 3-5% accuracy range.