Medical Physics Seminar – Monday, September 9, 2019
Small Field Challenges and the Development of a Scintillation Detector
Shannon Holmes, PhD (Hosted by Dr. Larry DeWerd)
Medical Physicist, Standard Imaging, Inc.
The drive toward smaller and smaller fields in stereotactic radiosurgery and highly modulated radiotherapy revealed significant challenges for accurate dose measurements. Clinical physicists are finding their familiar ionization chambers and diodes becoming increasingly burdened with unwieldy and complex small field correction factors, whose dependencies are often unclear or poorly defined. Partial volume effects also complicated the equation. The need for a better small field detector prompted renewed investigation into organic scintillation dosimetry that had shown promise in research applications, if only one could only get around the difficulty of dealing with ÄŒerenkov light. Collaboration between Standard Imaging (Middleton, WI) and researchers at M.D. Anderson Cancer Center (Houston, TX) and Laval University (Quebec City, QC) resulted in the first commercially available scintillation detectors for small field radiation therapy. These detectors offer a tantalizing alternative that simplifies the problem of small field dosimetry.