(Monday, 7/30/2018) 7:30 AM - 9:30 AM
Room: Karl Dean Ballroom A1
Purpose: To create a device capable of addressing the unmet clinical need for remote, real-time, surface dosimetry. By achieving rapid dose readout, and using a wireless system, we aim to reduce the amount of time and effort necessary to conduct full-body dosimetry. Dose data for a patient undergoing Total Skin Electron Therapy (TSET) was acquired by imaging scintillator targets on the skin surface with an intensified camera.
Methods: Dosimeter packets containing scintillator (disc-shaped, 1cm Ø x 1mm thick, EJ-212 Elijen Technology) and Optically Stimulated Luminescence (OSL) dosimeters were placed on five body locations of a patient receiving TSET using the Stanford Technique from a Varian Trilogy linac. To convert light output to dose: 1) a scintillator target ROI was selected 2) background and flatfield corrections were applied 3) an ellipse-convoluted-Gaussian was fit to the ROI 4) amplitudes of the fit, per frame, were summed 5) Fit output was converted to dose using scintillator calibration factors. Surface dose measured by scintillator was compared to that of OSLD.
Results: Absolute dose measurements for 25 different dosimetry sites, collected over the course of 5 days, were analyzed. Relating scintillator to OSLD dose via linear regression yielded an R² of 94%. Percent difference in dose reported by scintillator versus OSLD, per site, was <5% and <3% in 24/25 and 18/25 cases, respectively. The distribution of dose differences between OSL and scintillator dosimeters can be potentially attributed to variations in scintillator-to-camera angles across the body.
Conclusion: Compared to OSLDs, scintillators were able to measure surface dose within <5% accuracy. Linac-synchronized imaging of calibrated scintillator targets has the potential to provide live absolute surface dosimetry information for patients being treated with TSET. Furthermore, this technique can also be adopted for use in any surface dosimetry scenario where the surface of interest is visible during treatment.
Funding Support, Disclosures, and Conflict of Interest: This work has been sponsored by NIH research grants R44 CA199836, R01 EB023909, and Shared Resources from the Norris Cotton Cancer Center core facilities, sponsored by P30 CA023106. P. Bruza is principal investigator in SBIR subaward B02463 (prime award NCI R44 CA199681). B. Pogue is a president of DoseOptics LLC.
Keywords
Dosimetry, Scintillators, Optical Modeling
Taxonomy
TH- External beam- electrons: dose measurement
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