A Non-Contact Optical Patient and Beam Dosimetry System for Continuous in vivo Radiotherapy Verification

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Abstract Optical Cherenkov video imaging of body anatomy and dose delivery can be used now to map out radiotherapy beam incidence upon the patient tissue, directly visualizing the radiation dose deposition on the patient in real time. This could serve as a non-contact workflow tool for verification for daily fractionated radiation therapy, allowing capture of all treatments, all the time. DoseOptics has developed the C-Dose™ camera system, capable of real-time imaging, used in on-going clinical studies in radiation oncology at the Dartmouth-Hitchcock Medical Center. The live 2-D images of the radiation beam on the surface of the patient's tissue, will be integrated with real-time optical surface mapping of patient anatomy from surface mapping. To achieve our goals, the mapping system needs specialized gating off during each radiotherapy pulse-on time, allowing Cherenkov image capture at 360 Hz, the pulse rate of the linac. Additionally, to make the C-Dose images quantitatively accurate, a correction for tissue emissivity needs to be added in, and active imaging from the mapping projector and C-Dose camera will provide this. The combined system should have better than 3% accuracy in calibrated Dose linearity, and the combined overlay on the patient anatomy will make the system the most functional yet for beam and patient position dosimetry. This will be all verified in the Phase 1, and then the combined system will be developed for a multicenter trial, testing for the rate of observed incidents in whole breast radiotherapy. The RO- ILS data based indicates that 27% of incidents are discovered during therapy delivery, and so we will test the systems in two centers where the patient alignment practice is different (laser & tattoo alignment, vs optical alignment) and track incidents related to accuracy of beam and body position. In the completion of this work, we will have a completed system ready for regulatory clearance, and have the data required to demonstrate value to the customers, being the radiotherapy team and the patients getting their daily treatment. This project is backed by a considerable amount of prior camera development and a critical commercial/marketing partner, and will produce the worlds first all optical, non-contact imaging dosimetry system. The team members involved have expertise in all aspects of the development and clinical radiotherapy physics needed to make the project succeed. Beyond this specific application of whole breast radiotherapy, there are other key applications in which the system could be useful as well, where the field sizes are large and dynamics and patient positioning are critical.