Author: Amar K. Basavatia, Lee C. Goddard, Rachel Grimm, Wolfgang A. Tomé 👨🔬
Affiliation: Montefiore Medical Center 🌍
Purpose: To characterize the “MyOSL Chip” OSLD system for clinical use and compare the response of multiple readers to allow for utilization in a multi-clinic environment.
Methods: Dose calibration curves were generated for three different readers utilizing five “high dose” chips per reader. Read time corrections were determined by re-reading five chips at multiple time points. Chip specific re-read depletion correction factors were determined by performing 10 sequential readouts for each chip and determining the average depletion factor. Once corrections had been applied the linearity of each chip and chip specific sensitivities were determined. Energy dependance was examined for multiple photon and electron energies (6-15MV, 6-16MeV).
Results: The average re-read depletion correction was found to be 1.5% per measurement (1.0%-2.4%). An increase of ~4.5% was found when reading 10 minutes vs 240 minutes post irradiation. The fifteen chips utilized to build calibration curves demonstrated excellent linearity with R2>0.995 for all chips in the 0.25-10.0 Gy range. A statistically significant (p<0.001) difference was found in the response of individual readers when the ANOVA was calculated for the average light count per gray (LC) of the fifteen chips. Utilizing the batch average LC individual chip sensitivity was found to vary between 0.85 and 1.20. Energy dependence was found to be within ±0.8%.
Conclusion: Due to the large variance in response of each chip but excellent linearity it was determined that utilizing a chip specific light count per gray factor was preferable vs. an average correction factor with chip specific sensitivity correction factors. Each reader examined had statistically significant differences in the measured light count, thus, calibration and readout of individual chips must be performed on the same reader. Little energy dependence was found, hence, a single LC correction factor is sufficient, independent of the photon or electron energy utilized (MV range).