title: Dosimetry characteristics of metallic cones for intraoperative radiotherapy.
abstract: Dosimetry data were obtained on the first dedicated linear accelerator of its type designed for electron intraoperative radiotherapy (IORT) within an operating room. The linear accelerator uses a high dose rate, 9 Gy.min-1, to reduce the treatment time. Its chrome-plated brass treatment cones, designed with straight ends and 22.5 degrees beveled ends, are not mechanically attached to the collimator head, but are aligned using a laser projection system. Dosimetry measurements were made for each combination of energy (6, 9, 12, 15, and 16 MeV), cone size (diameters range from 5 to 12 cm), and cone type (22.5 degrees beveled or straight). From these data, depth-dose curves, cone output, and air-gap correction factors were generated that allow the calculation of the monitor setting for delivering a prescribed dose at any depth for any irradiation condition (energy, cone, air gap). Isodose data were measured for every cone using film in a solid water phantom. Scatter off the inside wall of the cone resulted in peripheral dose horns near the surface that were energy and cone dependent, being as large as 120%.
authors.affiliation: Department of Radiation Physics, University of Texas, M. D. Anderson Cancer Center, Houston 77030.
authors.forename: C E
authors.initials: CE
authors.lastname: Nyerick
authors.forename: T G
authors.initials: TG
authors.lastname: Ochran
authors.forename: A L
authors.initials: AL
authors.lastname: Boyer
authors.forename: K R
authors.initials: KR
authors.lastname: Hogstrom
mesh_terms: D004583:Electrons; D006801:Humans; D007432:Intraoperative Period; D009873:Operating Rooms; D010315:Particle Accelerators / Q000295:instrumentation*; D011879:Radiotherapy Dosage