SPECT/CT bone imaging after hip resurfacing arthroplasty: is it feasible to use CT attenuation correction in the presence of metal implants?

Background In hip resurfacing arthroplasty a metal implant (prosthesis) is used to resurface the patient's native femoral head. The assessment of bone function around the implant is important in evaluating any subsequent complications. The use of bone single photon emission computed tomography/computed tomography (SPECT/CT) imaging may enhance this evaluation. Objectives The primary objective of this study was to ascertain whether SPECT/CT imaging is feasible in the presence of the metal implant. A secondary objective was to deduce the impact attenuation correction has on the detected counts originating from bone covered by the metal implant. Methods A phantom was constructed to allow assessment of counts obtained from a point source (PS) imaged in the vicinity of a hip resurfacing implant. Three implant cup sizes (4, 8 and 10) were assessed and images acquired with a PS positioned adjacent to the implant pin and under the cup. Multiple acquisitions were undertaken both with and without surrounding soft tissue equivalent material. The images were analysed with and without attenuation correction and the recovered counts compared with that of a PS imaged in free space (control). Results Attenuation-corrected counts did not vary significantly with cup size (P=0.427), PS position (P=0.999), presence of soft tissue equivalent material (P=0.193) or a combination of PS position and soft tissue (P=0.193). The attenuation-corrected counts recovered from a PS (soft tissue equivalent material present) showed an overestimation, compared with the control, both when positioned adjacent to the pin and under the cup; mean 8% (4-16%) and 4% (1-6%), respectively. Conclusion The results of the study suggest that the application of the attenuation correction technique is applicable to bone SPECT/CT images of the femoral head-neck junction acquired in the presence of a hip resurfacing implant Nucl Med Commun 32:289-297 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.