title: Numerical simulation of SAR induced around Co-Cr-Mo hip prostheses in situ exposed to RF fields associated with 1.5 and 3 T MRI body coils.
abstract: When patients with metallic prosthetic implants undergo an MR procedure, the interaction between the RF field and the prosthetic device may lead to an increase in specific absorption rate (SAR) in tissues surrounding the prosthesis. In this work, the distribution of SAR(10g) around bilateral CoCrMo alloy hip prostheses in situ in anatomically realistic voxel models of an adult male and female due to RF fields from a generic birdcage coil driven at 64 or 128 MHz are predicted using a time-domain finite integration technique. Results indicate that the spatial distribution and maximum values of SAR(10g) are dependent on body model, frequency, and the position of the coil relative to the body. Enhancement of SAR(10g) close to the extremities of a prosthesis is predicted. Values of SAR(10g) close to the prostheses are compliant with recommended limits if the prostheses are located outside the coil. However, caution is required when the prostheses are within the coil since the predicted SAR(10g) close to an extremity of a prosthesis exceeds recommended limits when the whole body averaged SAR is 2 W kg(-1) . Compliance with recommended limits is likely to require a reduction in the time averaged input power.
authors.affiliation: Radiological Sciences Unit, Charing Cross Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Powell
authors.forename: Annie
authors.initials: A
authors.lastname: Papadaki
authors.forename: Jeff
authors.initials: J
authors.lastname: Hand
authors.forename: Alister
authors.initials: A
authors.lastname: Hart
authors.forename: Donald
authors.initials: D
authors.lastname: McRobbie
mesh_terms: D000328:Adult; D003198:Computer Simulation; D006621:Hip Joint / Q000503:physiopathology* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014800:Vitallium
chemical_list: D014800:Vitallium