TOTAL HIP-PROSTHESIS METAL-ARTIFACT SUPPRESSION USING ITERATIVE DEBLURRING RECONSTRUCTION

Purpose: CT of total joint prostheses is limited by metal artifact pro duced mainly by missing projection data. Iterative deblurring reconstr uction is less sensitive to missing projection data than filtered back projection. A software CT simulator was used to compare total hip pros thesis images reconstructed using standard filtered backprojection, fi ltered backprojection after linear interpolation of missing data, and iterative deblurring. Method: Unilateral and bilateral total hip repla cements with metal-backed or all-polyethylene acetabular prostheses we re simulated using bone, metal, and polyethylene annuli and circles of metal and water (soft tissue). Material attenuation properties were t aken from the literature. The simulation assumed that no X-rays penetr ated the metal. Simulated projection data were reconstructed using fil tered backprojection, filtered backprojection after linear interpolati on of missing data, and iterative deblurring. Visual observations and objective region-of-interest analyses were made. Results: Even with no X-rays penetrating the metal, iterative deblurring produced almost no visible artifact within the bone or soft tissues. Bone edge detection and sizing were more easily and accurately done from the iterative de blurring images. All reconstruction techniques underestimated bone and water CT attenuation values. Metal artifact was worse for the bilater al or metal-backed prostheses. Conclusion: Iterative deblurring genera ted nearly metal-artifact-free images in this simulation. Filtered bac kprojection, even after linear interpolation, produced typical clinica l metal-artifact images.