Purpose: This study aimed to evaluate IViST, a novel multi-sensor-based dosimetry platform for real-time plan monitoring in HDR brachytherapy.
Methods: The novel platform comprises 3 parts: 1) a fully optimized and characterized multi-point plastic scintillator dosimeter (mPSD; using BCF-60, BCF-12, and BCF-10 scintillators), 2) a compact assembly of photomultiplier tubes (PMTs) coupled to dichroic mirrors and filters for high-sensitivity scintillation light collection, and 3) a Python-based graphical user interface used for system management and signal processing. Individual scintillator signals were measured using a hyperspectral approach, taking into account the Cerenkov stem effect. The PMTs were independently controlled and read simultaneously using a NI-DAQ board at 100 kHz. The dosimetric performance was assessed in water under several conditions, including a prostate plan. The agreement with TG-43U1 expected dose, the receiver operating characteristic (ROC) curve, the temporal resolution, and the systemâ€™s performance in detecting errors (e.g., interchanging pairs of guide tubes, wrong source dwell positions and dwell time) were all tested. The triangulation principle was used to report measured source positions relative to planned ones.
Results: Differences between the mPSD measurements and TG-43U1 were within 5% up to 10 cm from the source. The system was able to track the source with a mean difference of 0.43Â±0.7 mm relative to the expected value for sensor-to-source distances of 0.5 to 6.5 cm. The observed weighted (over the 3 sensors) mean deviation between the planned and measured source dwell time was 0.38Â±0.67 s. All introduced errors were successfully detected. In the ROC analysis, the BCF-10 sensor showed the highest sensitivity and specificity. For all the scintillators, the areas under the curve were greater than 0.8.
Conclusion: The platform allows accurate real-time dose, source position, and dwell-time measurements, a combination of features not found in any available commercial systems for application in brachytherapy.
Funding Support, Disclosures, and Conflict of Interest: The present work was supported by the National Sciences and Engineering Research Council of Canada , by the Canadian Foundation for Innovation JR Evans Leader Funds, the Fonds de Recherche du Quebec - Nature et Technologies and by the CREATE Medical Physics Research Training Network.