Background: 

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.

Methods: 

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.

Results: 

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).

Conclusions: 

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.

Level of Evidence: 

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

中文翻译：

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结合金属伪影抑制算法的单能和双能 CT 方案扫描参数对 THA 的影响：体外研究

背景： 

髋关节置换柄造成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。这项离体研究的目的是评估不同扫描参数和金属伪影算法在存在髋关节柄的情况下对图像质量的影响。

方法： 

9 根股骨柄，6 根非骨水泥型和 3 根骨水泥型，在受试者生前植入，在死后和解剖遗体捐献后取出并进行研究。比较了 12 种 CT 协议，包括单能量 (SE) 和单源连续双能量 (DE) 扫描，使用和不使用迭代金属伪影减少算法（iMAR；西门子 Healthineers）和/或单能重建。对每个协议评估了条纹和泛光伪影以及主观图像质量。

结果： 

使用 iMAR 减少金属伪影显着减少了所有研究方案中的条纹伪影（p = 0.001 至 0.01）。使用锡过滤器和 iMAR 的 SE 协议观察到最佳主观图像质量。使用 iMAR（Hounsfield 单位的标准偏差：151.1、143.7、144.4）以及使用锡过滤器和 iMAR (163.5) 的 SE 协议在 110、160 和 190 keV 的单能重建中观察到最少的条纹伪影。对于带有锡过滤器但没有 iMAR（4.40 毫米）的 SE 和没有 iMAR 的 190 keV 单能重建（4.67 毫米），可以看到最小的虚拟增长。

结论： 

该研究强烈建议在临床实践中应使用金属伪影减少算法（例如，iMAR）对具有非骨水泥或骨水泥股骨柄的假体的骨-植入物界面进行成像。在 iMAR 协议中，具有 140 kV 和锡过滤器的 SE 协议产生了最佳的主观图像质量。此外，该协议和 160 和 190 keV 的 DE 单能重建与 iMAR 实现了最低水平的条纹和开花伪影。

证据等级： 

诊断三级。有关证据等级的完整描述，请参阅作者须知。