title: Planning of radiotherapy for patients with hip prosthesis.
abstract: The effects of a hip prosthesis on the dose distribution when treating pelvic cancer have been evaluated. A prosthesis of titanium alloy in a water phantom was used as a model. Photon radiation beams with energies of 6, 20, and 50 MV and with a focus phantom distance of 100 cm were directed against the prosthesis. The dose profiles at different depths were measured with the RFA-7 system. The sphere of the prosthesis was inhomogeneous. The dose in a beam behind the prosthesis was reduced with the order of 10-40% and the largest distortion was behind the shaft. Using an opposed four-field technique with the same weight on all the fields, the dose reduction was as large as 7-12% in a string across the target behind the end of the shaft. With 50% weight on the lateral fields, the dose reduction was 4-8% of the average dose. Such an uneven dose distribution may decrease the curability, and a treatment technique not including the prosthesis should be preferred. Finally, a local increase of the dose close to the prosthesis seems to be of limited practical concern even at the highest energies.
authors.affiliation: Department of Oncology, University of Umeå, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Erlanson
authors.forename: L
authors.initials: L
authors.lastname: Franzén
authors.forename: R
authors.initials: R
authors.lastname: Henriksson
authors.forename: B
authors.initials: B
authors.lastname: Littbrand
authors.forename: P O
authors.initials: PO
authors.lastname: Löfroth
mesh_terms: D006622:Hip Prosthesis; D006801:Humans; D008961:Models, Structural; D010386:Pelvic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014025:Titanium; D014867:Water
chemical_list: D014867:Water; D014025:Titanium