Room: Stars at Night Ballroom 4
Purpose: To demonstrate the utility of Cherenkov and scintillation imaging of the treatment surface during head and neck radiotherapy, through transparent bolus and immobilization mask material, in order to measure surface dosimetry and inform clinical replanning decisions.
Methods: Both Cherenkov emission from tissue and phantom material and scintillation from small plastic targets placed on the treatment surface were imaged using a time-gated intensified CMOS camera during head and neck radiotherapy. Scintillating targets were imaged through transparent bolus and immobilization mask material on body phantoms to demonstrate clinical utility. Interfraction anatomy changes were simulated on a head and neck phantom and the corresponding Cherenkov emission distributions were imaged during administration of VMAT treatment. Lastly, human patients undergoing head and neck radiotherapy were imaged throughout fractionated treatment, and cumulative Cherenkov emission and scintillation were tracked day-to-day.
Results: Scintillation and Cherenkov emission can be quantified through transparent bolus and immobilization masks and related to deposited surface dose. The relationship between simulated tumor reduction and change in Cherenkov intensity from a phantom is found to be highly linear, with a coefficient of determination of 0.99. Finally, Cherenkov images from patient treatment show potential for beam verification underneath mask material in head and neck cancer patients and may provide information clinically relevant to adaptive replanning decisions.
Conclusion: It is demonstrated for the first time that field verification and interfraction tracking of anatomy changes in head and neck radiotherapy is possible with real-time Cherenkov emission imaging. Imaging of scintillating targets and Cherenkov emission through transparent bolus is shown to be a potentially robust solution to surface dosimetry in patients with prescribed bolus use. Lastly, Cherenkov emission and scintillation imaging of patient treatment shown to be a useful tool for field verification and tracking of treatment delivery.
Funding Support, Disclosures, and Conflict of Interest: This work has been sponsored by NIH research grants R01EB023909 and R44CA199681. B Pogue is the president and co-founder of DoseOptics LLC. P Bruza is the principal investigator in an SBIR subaward B02463 (prime award NCI R44CA199681, DoseOptics LLC).