Water-Equivalent Plastic Scintillation Detectors for Small-Field Radiotherapy

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DESCRIPTION (provided by applicant): Standard Imaging, Inc. is developing a new generation of radiation dosimeters for small field dosimetry. These small detectors are needed in clinical applications such as stereotactic radiosurgery/stereotactic radiotherapy (SRS/SRT), intensity modulated radiation therapy (IMRT), dynamic arc therapy, and tomotherapy treatments. The enabling technology is the point scintillation detector that employs a miniature plastic scintillator coupled to a color PIN diode detector via an optical fiber. Small field radiotherapy techniques such as stereotactic radiosurgery (SRS) or stereotactic body radiation therapy (SBRT) enable delivery of high radiation doses to tumors while sparing healthy tissue and organs at risk. These special and complex treatment modalities significantly benefit patients and offer substantial advantages over traditional radiotherapy techniques. Because SRS and SBRT treatments often deliver the entire therapeutic dose in a single or hypofractionated treatment regimen, the treatments must be delivered accurately. Phase I generated a robust, single-point water-equivalent scintillation dosimeter to accurately characterize and measure the dosimetry of small fields and to verify these special treatments before delivery. The compact, fully operational Plastic Scintillation Detector (PSD) is further enhanced when paired with Standard Imaging's dual-channel SuperMAX electrometer. However, the PSD/SuperMAX electrometer system cannot yet be used with water scanning systems because it lacks a compatible analog signal output. Coordinated use of a water scanning system with SRS-appropriate detectors is crucial to characterize these precise radiation fields accurately and efficiently before patient treatment. The overall goal of this Phase II project is to transition th Phase I small-field detector from a bench-top system requiring a specialized 2-channel electrometer to a versatile fully commercialized medical radiation detector. Achieving this goal will advance the successful Phase I project by (1) greatly expanding the effectiveness and market potential of PSD devices by developing a universally compatible detector system that could be fully used in place of an ionization chamber or diode with existing medical radiation measurement equipment, especially water scanning systems, (2) thoroughly optimizing the detector, and (3) fully characterizing the detector for easy application in typical clinical settins. At the successful completion of this Phase II study, Standard Imaging will be poised to deliver to the market a well-characterized PSD suitable for precise dosimetry and QA of small fields used in SRS and SBRT, and that is fully compatible with existing measurement systems. Further development of this single-point system subsequently could include generating multi-point systems such as 2D arrays for patient dosimetry or fixed linear arrays for water scanning.