Purpose: A novel system composed of a monocrystalline scintillator and optical camera has been developed for Quality Assurance (QA) on high dose-rate (HDR) brachytherapy afterloaders. HDR QA requires adherence to US-NRC regulations, and includes high definition archival image documentation of the source positioning. HDR QA is required for (1) daily use of the system, (2) periodic source exchanges, (3) validation of applicators, and new developments call for (4) patient specific QA. The new proto-type commercial system uses radioluminescence imaging to determine position and dwell-time accuracy of the source and can provide patient specific QA for complex deliveries.
Methods: The scintillator and optical camera system (OriQA, Luca Medical Systems, Palo Alto, CA) with high spatial and temporal resolution was tested on a Varian GammaMediX HDR afterloader (Palo Alto, CA). The evaluations included position and timer accuracy as well as cumulative activity measurement over a range of doses typically prescribed for gyn brachytherapy. The accuracy and standard deviation were then evaluated for dwell time and position, and cumulative activity for various configurations.
Results: The system readily acquires and analyzes images of the source position in accordance with standard practice for HDR daily QA. Several dwell positions over a 10 cm range with varying dwell times between 0.3 - 20 seconds were employed. The position error of the QA device was identified as -0.01 (±0.04) centimeters, the time error was -0.08 (±0.11) seconds, and the error in cumulative activity was <1%.
Conclusion: A new, novel, and practical HDR QA system has been devised that includes a monocrystalline scintillator and optical camera system. The radioluminescence technology of the device is highly accurate and precise, and with its low-cost camera based optical imaging system provides QA documentation in accordance with NRC regulations. The potential for applying this technology to patient specific QA is also investigated.
Funding Support, Disclosures, and Conflict of Interest: UC Davis has a research agreement with OriQA, Luca Medical Systems