Robertson D D, Yuan J, Wang G, Vannier M W
Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Comput Assist Tomogr. 1997 Mar-Apr;21(2):293-8. doi: 10.1097/00004728-199703000-00024.
CT of total joint prostheses is limited by metal artifact produced mainly by missing projection data. Iterative deblurring reconstruction is less sensitive to missing projection data than filtered backprojection. A software CT simulator was used to compare total hip prosthesis images reconstructed using standard filtered backprojection, filtered backprojection after linear interpolation of missing data, and iterative deblurring.
Unilateral and bilateral total hip replacements with metal-backed or all-polyethylene acetabular prostheses were simulated using bone, metal, and polyethylene annuli and circles of metal and water (soft tissue). Material attenuation properties were taken from the literature. The simulation assumed that no X-rays penetrated the metal. Simulated projection data were reconstructed using filtered backprojection, filtered backprojection after linear interpolation of missing data, and iterative deblurring. Visual observations and objective region-of-interest analyses were made.
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 deblurring images. All reconstruction techniques underestimated bone and water CT attenuation values. Metal artifact was worse for the bilateral or metal-backed prostheses.
Iterative deblurring generated nearly metal-artifact-free images in this simulation. Filtered backprojection, even after linear interpolation, produced typical clinical metal-artifact images.
全关节假体的CT检查受主要由缺失投影数据产生的金属伪影限制。迭代去模糊重建对缺失投影数据的敏感度低于滤波反投影。使用软件CT模拟器比较采用标准滤波反投影、缺失数据线性插值后的滤波反投影以及迭代去模糊重建的全髋关节假体图像。
使用骨、金属和聚乙烯环以及金属和水（软组织）的圆圈模拟单侧和双侧全髋关节置换，其中髋臼假体有金属背衬或全聚乙烯材质。材料衰减特性取自文献。模拟假设没有X射线穿透金属。使用滤波反投影、缺失数据线性插值后的滤波反投影以及迭代去模糊重建模拟投影数据。进行视觉观察和感兴趣区域的客观分析。
即使没有X射线穿透金属，迭代去模糊在骨或软组织内几乎不产生可见伪影。从迭代去模糊图像中更容易且准确地进行骨边缘检测和尺寸测量。所有重建技术均低估了骨和水的CT衰减值。双侧或金属背衬假体的金属伪影更严重。
在本模拟中，迭代去模糊生成了几乎无金属伪影的图像。滤波反投影，即使是在缺失数据线性插值之后，仍产生典型的临床金属伪影图像。
