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Imaging Sensor Comparison for Real-Time Cherenkov Signal Detection From Tissue for Treatment Verification

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J Andreozzi

J Andreozzi1*, R Zhang1 , A Glaser1 , L Jarvis2 , D Gladstone2 , B Pogue1 , (1) Dartmouth College, Hanover, NH, (2) Dartmouth-Hitchcock Medical Center, City Of Lebanon, New Hampshire


TH-C-17A-1 Thursday 10:15AM - 12:15PM Room: 17A

Purpose: To identify the optimum imaging sensor for a clinical system that would provide real-time imaging of the surface beam profile on patients as novel visual information to radiation therapy technologists, and more rapidly collect clinical data for large-scale studies of Cherenkov applications in radiotherapy.

Methods: Four camera types, CMOS, CCD, ICCD and EM-ICCD, were tested to determine proficiency in the detection of Cherenkov signal in the clinical radiotherapy setting, and subsequent maximum supportable frame rate. Where possible, time-gating between the trigger signal from the LINAC and the intensifiers was implemented to detect signal with room lighting conditions comparable to patient treatment scenarios. A solid water phantom was imaged by the EM-ICCD and ICCD to evaluate the minimum number of accumulations-on-chip required for adequate Cherenkov detection, defined as >200% electron counts per pixel over background signal. Additionally, an ICCD and EM-ICCD were used clinically to image patients undergoing whole-breast radiation therapy, to understand the impact of the resolution limitation of the EM-ICCD.

Results: The intensifier-coupled cameras performed best at imaging Cherenkov signal, even with room lights on, which is essential for patient comfort. The tested EM-ICCD was able to support single-shot imaging and frame rates of 30 fps, however, the current maximum resolution of 512 x 512 pixels was restricting. The ICCD used in current clinical trials was limited to 4.7 fps at a 1024 x 1024 resolution. An intensifier with higher quantum efficiency at the entrance photocathode in the red wavelengths (30% QE vs current 7%) promises 16 fps at the same resolution at lower cost than the EM-ICCD.

Conclusion: The ICCD with the better red wavelength QE intensifier was determined to be the best suited commercial-off-the-shelf camera to detect real-time Cherenkov signal and provide the best potential for real-time display of radiation dose on the skin during treatment.

Funding Support, Disclosures, and Conflict of Interest: We have no conflicts. Funding is from grants from the NIH numbers R01CA109558 and R21EB017559.

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