Room: AAPM ePoster Library
Perhaps the most unique feature of Cherenkov emission during radiotherapy is that it is linear to dose, though the detected signal linearity from patient tissues weakens in the presence of in vivo absorbers. In this study, emitted Cherenkov light from whole breast radiation therapy treatments in n=13 patients was corrected for varying tissue optical properties using a calibration between Cherenkov light intensity and correlated CT number (HU). This work presents the first major step to the most limiting aspect of in vivo imaging dosimetry.
Readily available patient CT scans from the treatment planning system (TPS) were used to sample the average radiodensity (HU) in the first 10 mm of tissue, and a time-gated intensified CMOS camera (C-Dose Research, DoseOptics LLC, Lebanon, NH) was used to image the Cherenkov light emitted during radiotherapy treatments over the course of this IRB-approved study.
A negative linear correlation between the average CT radiodensity (HU) with the average amount of Cherenkov light (?) emitted per unit deposited dose (Gy) was discerned for 6 MV beams (n=13,p=0.00034,R²=0.70) and 10 MV beams (n=5,p=0.041,R²=0.80). This calibration was then used to correct the Cherenkov light for breast radiodensity-dependent tissue optical properties, better elucidating the linearity between Cherenkov light and dose in vivo. The regression describing 6 MV beam energies was strengthened substantially from, R(uncorr,6)² = 0.67, to R(corr,6)² of 0.85. The 10 MV beams were improved from 0.91 to 0.95.
Despite nearly unlimited ability to measure transmission of the beam through tissue, there has never been a way to quantify radiation dose deposited directly. This work (recently accepted for publication in Nature Communications), presents the first possibility in breast irradiation imaging. Upon further development, extracting in vivo dose directly from these images can reveal dose deposition consistency for each treatment fraction and between patients.
Funding Support, Disclosures, and Conflict of Interest: Authors Prof. Brian Pogue, Prof. Michael Jermyn and Dr. Lesley Jarvis M.D. have competing interests with DoseOptics LLC, a company that manufactures Cherenkov cameras used to monitor radiation therapy.