Purpose: Cherenkov imaging has been shown to be capable of displaying certain treatment irregularities that might otherwise go unnoticed with standard QA processes. In this study we report on a clinical QA/QI study investigating the use of always-on treatment delivery monitoring with Cherenkov imaging in a radiotherapy clinic.
Methods: Cherenkov imaging systems (BeamSite, DoseOptics LLC, Lebanon NH) were installed in two linac bunkers in our clinic, which provided continuous imaging of Cherenkov and background images of all treatments. For this project, a custom data transfer and central storage infrastructure was employed to efficiently handle the collection and review of the current 3500-fraction dataset. Images were reviewed post-treatment by a team clinical staff consisting of therapists, physicists, and physicians, and any irregularities were interpreted and analyzed using standard clinical tools and procedures.
Results: Offline review of 200 patient treatments uncovered 3 independent delivery events, all related to patient positioning. One case consisted of unfavorable chin positioning during an AP-PA thoracic spine treatment which was corrected mid-fraction. The remaining two cases involved arm/hand placement which resulted in unintended exposure; one was found to have persisted for 7/10 fractions resulting in an estimated 3 Gy of exit dose to the arm and no negative impact on the treatment area. Independently, during this same period, 12 events were reported in the hospital-based incident reporting system, all deemed to have no detectable harm to the patient.
Conclusion: Clinical review of Cherenkov images identified non-ideal patient positioning events during treatment which were not identified in the existing QA program. This system has the potential to improve radiation oncology incident learning through the increased visibility of clinical events during patient treatment. Future work will focus on data-driven automatic incident detection with improved sensitivity and development of appropriate action procedures to improve efficacy and efficiency.
Funding Support, Disclosures, and Conflict of Interest: This work has been supported by NIH grant R01 EB023909 with hardware support through R44 CA232879 and with the support of the Norris Cotton Cancer Center shared resources in 5P30 CA023108-41. BP is the President of, DA is a consultant for, and MJ and PB are employees of DoseOptics LLC.
Optical Imaging, Patient Positioning, Surface Dose
TH- External Beam- Photons: out of field dosimetry/risk analysis