title: Activation of hip prostheses in high energy radiotherapy and resultant dose to nearby tissue.
abstract: High energy radiotherapy can produce contaminant neutrons through the photonuclear effect. Patients receiving external beam radiation therapy to the pelvis may have high-density hip prostheses. Metallic materials such as those in hip prostheses, often have high cross-sections for neutron interaction. In this study, Thackray (UK) prosthetic hips have been irradiated by 18 MV radiotherapy beams to evaluate the additional dose to patients from the activation products. Hips were irradiated in- and out-of field at various distances from the beam isocenter to assess activation caused in-field by photo-activation, and neutron activation which occurs both in and out-of-field. NaI(Tl) scintillator detectors were used to measure the subsequent gamma-ray emissions and their half-lives. High sensitivity Mg, Cu, P doped LiF thermoluminescence dosimeter chips (TLD-100H) were used to measure the subsequent dose at the surface of a prosthesis over the 12 h following an in-field irradiation of 10,000 MU to a hip prosthesis located at the beam isocenter in a water phantom.53Fe,56Mn, and52V were identified within the hip following irradiation by radiotherapy beams. The dose measured at the surface of a prosthesis following irradiation in a water phantom was 0.20 mGy over 12 h. The dose at the surface of prostheses irradiated to 200 MU was below the limit of detection (0.05 mGy) of the TLD100H. Prosthetic hips are activated by incident photons and neutrons in high energy radiotherapy, however, the dose resulting from activation is very small.
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Keehan
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.|William Buckland Radiotherapy Centre, The Alfred Hosptial, Melbourne, Victoria, Australia.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Smith
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.|William Buckland Radiotherapy Centre, The Alfred Hosptial, Melbourne, Victoria, Australia.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Millar
authors.affiliation: Department of Orthopaedic Surgery, The Alfred Hosptial, Melbourne, Victoria, Australia.
authors.forename: Max
authors.initials: M
authors.lastname: Esser
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Taylor
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.|Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
authors.forename: Peta
authors.initials: P
authors.lastname: Lonski
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.|Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kron
authors.affiliation: School of Science, RMIT University, Melbourne, Victoria, Australia.
authors.forename: Rick D
authors.initials: RD
authors.lastname: Franich
mesh_terms: D006622:Hip Prosthesis; D006801:Humans; D009010:Monte Carlo Method; D009502:Neutrons; D058958:Organs at Risk / Q000528:radiation effects; D010315:Particle Accelerators / Q000295:instrumentation*; D010386:Pelvic Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D013819:Thermoluminescent Dosimetry
keywords: high energy radiotherapy; photonuclear effect; prostheses activation