Schwarz Gilbert M, Huber Stephanie, Wassipaul Christian, Kasparek Maximilian, Hirtler Lena, Hofstaetter Jochen G, Bader Till, Ringl Helmut
Department of Orthopedics and Trauma-Surgery, Medical University of Vienna, Vienna, Austria.
Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria.
J Bone Joint Surg Am. 2023 Apr 19;105(8):620-629. doi: 10.2106/JBJS.22.01003. Epub 2023 Feb 27.
Metal artifacts caused by hip arthroplasty stems limit the diagnostic value of computed tomography (CT) in the evaluation of periprosthetic fractures or implant loosening. The aim of this ex vivo study was to evaluate the influence of different scan parameters and metal artifact algorithms on image quality in the presence of hip stems.
Nine femoral stems, 6 uncemented and 3 cemented, that had been implanted in subjects during their lifetimes were exarticulated and investigated after death and anatomical body donation. Twelve CT protocols consisting of single-energy (SE) and single-source consecutive dual-energy (DE) scans with and without an iterative metal artifact reduction algorithm (iMAR; Siemens Healthineers) and/or monoenergetic reconstructions were compared. Streak and blooming artifacts as well as subjective image quality were evaluated for each protocol.
Metal artifact reduction with iMAR significantly reduced the streak artifacts in all investigated protocols (p = 0.001 to 0.01). The best subjective image quality was observed for the SE protocol with a tin filter and iMAR. The least streak artifacts were observed for monoenergetic reconstructions of 110, 160, and 190 keV with iMAR (standard deviation of the Hounsfield units: 151.1, 143.7, 144.4) as well as the SE protocol with a tin filter and iMAR (163.5). The smallest virtual growth was seen for the SE with a tin filter and without iMAR (4.40 mm) and the monoenergetic reconstruction of 190 keV without iMAR (4.67 mm).
This study strongly suggests that metal artifact reduction algorithms (e.g., iMAR) should be used in clinical practice for imaging of the bone-implant interface of prostheses with either an uncemented or cemented femoral stem. Among the iMAR protocols, the SE protocol with 140 kV and a tin filter produced the best subjective image quality. Furthermore, this protocol and DE monoenergetic reconstructions of 160 and 190 keV with iMAR achieved the lowest levels of streak and blooming artifacts.
Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.
髋关节置换柄引起的金属伪影限制了计算机断层扫描（CT）在评估假体周围骨折或植入物松动方面的诊断价值。这项体外研究的目的是评估不同扫描参数和金属伪影算法对存在髋关节柄时图像质量的影响。
九个股骨柄，6个非骨水泥型和3个骨水泥型，在受试者生前植入，在其死后经解剖尸体捐赠后取出并进行研究。比较了12种CT方案，包括有和没有迭代金属伪影减少算法（iMAR；西门子医疗）和/或单能重建的单能量（SE）和单源连续双能量（DE）扫描。对每个方案评估条纹和光晕伪影以及主观图像质量。
使用iMAR减少金属伪影在所有研究方案中均显著减少了条纹伪影（p = 0.001至0.01）。对于带有锡滤过器和iMAR的SE方案，观察到最佳主观图像质量。对于采用iMAR的110、160和190 keV单能重建（亨氏单位标准差：151.1、143.7、144.4）以及带有锡滤过器和iMAR的SE方案（163.5），观察到的条纹伪影最少。对于带有锡滤过器且无iMAR的SE方案（4.40 mm）和无iMAR的190 keV单能重建（4.67 mm），观察到最小的虚拟生长。
本研究强烈建议在临床实践中，对于非骨水泥型或骨水泥型股骨柄假体的骨-植入物界面成像应使用金属伪影减少算法（例如iMAR）。在iMAR方案中，采用140 kV和锡滤过器的SE方案产生了最佳主观图像质量。此外，该方案以及采用iMAR的160和190 keV的DE单能重建实现了最低水平的条纹和光晕伪影。
诊断性III级。有关证据水平的完整描述，请参阅作者指南。
