CLINICAL RADIATION PHYSICS SERVICE

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The section continues to provide expert physical and technological support for radiation treatment, consisting of routine calibration, quality assurance and first-line maintenance of all radiation producing and ancillary equipment. It includes special dosimetry studies, computer- assisted treatment planning and the design and development of special equipment tailored to developing clinical needs. Current research has been directed towards accurately measuring the dose distribution to patients receiving TBI for bone marrow transplant and to improving dose uniformity. Doses are now calculated based on point diode measurements using a newly developed algorithm. Dose uniformity is maximized by employing missing tissue compensators in the head and neck region. New patient contour profiles are checked against a library of existing compensators for an accurate match. New compensators are thus only manufactured when necessary and are added to the existing library. Research will next be conducted to improve the accuracy of patient positioning with the arms elevated and supported on a rest designed to modulate the dose to the expected value. This support will then expose the lungs so that appropriate shielding blocks can be used. A project is also starting in collaboration with the Naval Research Laboratory to evaluate the clinical utility of semiconductor doped Vycor glass as a substitute for Lithium Fluoride (LiF) in thermoluminescence dosimetry of photon and electron beams. This project will then expand to develop a multi-fiber dosimeter reader using Vycor glass dosimeters bonded to optical fibers. This system has the advantage of providing intermittent dose and dose-rate readings and should have applications in clinical, radiation protection and environmental remote dosimetry.