title: Dose perturbation by air cavities in megavoltage photon beams: implications for cavity surface doses.
abstract: Gas-filled cavities in the body are known to perturb megavoltage photon beams in radiation therapy. The bowel represents one such cavity where cavity dimensions can vary throughout a treatment course. This has implications for doses to the surface of the bowel. Doses to the first 0.1 mm and 1.0 mm of cavity surfaces were calculated for 6 MV and 18 MV photon beams for a range of cavity sizes. It is found that relatively minor variations in cavity surface doses result over the typical range of rectal cavity size (2-3 cm). However, the variations in surface dose should be considered whenever bowel reactions must be considered, or when the target cells of interest line the bowel itself.
authors.affiliation: Department of Radiation Oncology, Sir Charles Gairdner Hospital, Nedlands, Australia. Martin.Ebert@health.wa.gov.au
authors.forename: M A
authors.initials: MA
authors.lastname: Ebert
authors.forename: N A
authors.initials: NA
authors.lastname: Spry
mesh_terms: D000388:Air; D003198:Computer Simulation; D006801:Humans; D007422:Intestines / Q000528:radiation effects; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods