1.1 本指南介绍了对植入金属对金属（MOM）设备的患者进行磁共振成像（MRI）研究的推荐方案，以确定假体周围组织是否可能与不良局部组织反应（ALTR）相关。在使用特定植入物扫描患者之前，MR医生应确认设备具有MR条件，并且所使用的扫描协议满足特定植入物的安全扫描条件。本指南假设MRI协议将应用于植入体内的MOM设备。 此外，预计在执行该扫描协议期间，将遵循标准化的MRI安全措施。 1.2 本指南涵盖了使用MRI对患者MOM髋关节置换装置周围组织的临床评估。本指南适用于全髋关节系统和表面置换MOM髋关节系统。 1.3 本指南中包含的协议适用于IEC 60601-2-33第3.2版第201.3.239节中定义的具有第201节中定义的全身射频（RF）发射线圈的全身磁共振设备。 3.240. 射频线圈应具有IEC 60601-2-33第3.2版第201.3.249节中定义的圆极化射频激励（通常也称为正交激励）。 1.4 以国际单位制表示的数值应视为标准值。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 在确定这些方案的适用性之前，用户可以考虑MR系统和髋关节植入物标签中提供的所有预防措施和警告。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 由于其优越的软组织对比度、多平面能力和缺乏电离辐射，磁共振成像非常适合对MOM髋关节置换术进行成像。 MR成像是评估假体周围骨溶解和磨损性滑膜炎最准确的成像方式( 19 , 20 ). 5.2 在使用特定植入物扫描患者之前，MR医生应确认设备具有MR条件，并且所使用的扫描协议满足特定植入物的安全扫描条件。 5.3 本指南可用于识别以下不良事件。 5.3.1 骨溶解- 在评估周围神经病变方面，磁共振成像优于常规X线照片和计算机断层扫描（CT）- 人工骨溶解和已被证明是定位和量化假体周围骨溶解程度的最准确方法( 19 , 21 ). 在磁共振成像上，骨溶解表现为边缘良好的骨内中间到轻微增加的信号强度病变，与髓内脂肪的高信号强度形成对比。局部骨髓置换区域周围有一条低信号强度的特征线，区分骨溶解与骨肿瘤置换或感染( 22 ). 图4 左妈妈髋关节置换术的冠状位（左）和轴向（右）FSE图像 注1: 大转子内有局灶性骨溶解（白色箭头），表现为与骨骼肌相似的边界清晰的中等信号强度，取代了正常的高信号强度脂肪骨髓。图片由霍利斯·波特博士提供。 5.3.2 部件松动- 虽然数据是初步的，但磁共振成像可以识别可能指示组件松动的周向骨吸收。松动可能是由于骨溶解、周围纤维膜形成或非骨组织的骨整合不良所致- 胶结部件。在磁共振成像中，在脂肪抑制技术中，组件松动通常表现为金属骨或水泥骨界面的周向信号强度增加( 20 ). 周围纤维膜形成或骨溶解的发现也表明有潜在的松动；这与固定良好的部件形成对比，高信号强度的脂肪骨髓直接与植入物界面相对。 5.3.3 磨损性滑膜炎- 磁共振成像是评估囊内磨损负担最有用的成像方式- MOM关节成形术周围诱发滑膜炎( 23 ). 初步数据表明，MR成像上滑膜反应的信号特征与翻修手术组织学上显示的磨损性滑膜炎类型相关( 24 ). 低信号强度碎屑提示组织学上有金属碎屑。混合的中等和低信号碎片与组织学上存在的混合聚合物（聚乙烯和/或聚甲基丙烯酸甲酯）和金属碎片有关。磁共振成像可显示滑膜炎或滑液减压至邻近的囊，如髂腰肌或转子囊，可表现为软组织肿块或继发神经压迫。 有时，即使在没有局部溶骨性病变的情况下，磨损引起的滑膜炎也会导致周围骨骼的慢性惰性侵蚀( 6. ). 图5 左髋关节置换术的轴位（左）和冠状位（右）FSE图像 注1: 磨损引起的滑膜炎减压到外展肌组织，那里有低信号强度的碎片（箭头），与金属碎片一致。图片由霍利斯·波特博士提供。 5.3.4 感染- 在感染的情况下，滑膜通常表现为高强度片状外观，并伴有邻近的囊外软组织水肿。 这些表现有助于区分感染的滑膜模式和磨损引起的滑膜炎，尽管最终诊断仍需要抽吸( 22 ). 软组织集合、引流窦或骨髓炎的存在进一步支持了磁共振成像对感染的诊断。 图6 右妈妈髋关节成形术的轴向FSE（左）和反转恢复（右）图像 注1: 片状滑膜炎（黑色箭头）伴邻近囊外软组织水肿（白色箭头）。在随后的抽吸中确认感染。 图片由霍利斯·波特博士提供。 5.3.5 局部组织不良反应- 不良的局部组织反应可表现为滑膜炎、滑囊炎、骨溶解和关节置换术附近的囊性或实体性肿块，这些肿块可被称为假瘤( 19 , 20 ). ALTR还可以包括无菌性淋巴细胞性血管炎相关病变（ALVAL）的组织病理学特征，这可以在组织学上得到证实。阿尔瓦尔关节相对常见的表现是囊扩张，均匀的高信号液体夹杂着中等信号强度的病灶。 最近的研究表明，最大滑膜厚度和更多固体滑膜沉积物的存在与翻修手术时的组织损伤和组织学检查时的坏死高度相关( 15 ). 图7 右髋关节置换术中的轴向FSE图像 注1: 图7 显示大转子囊中大量积液（箭头所示），该囊通过后假性包膜中的裂开与髋关节相连（这些图像中未显示）。流体为高信号，具有精细的中等信号强度碎屑。 在翻修手术中，组织学证实ALVAL评分较高。图片由霍利斯·波特博士提供。 图8 右髋关节表面置换术中的轴向FSE图像 注1: 图8 显示假包膜扩张，流体信号强度减压至转子囊。假包膜增厚，信号强度中等（黑色箭头）。前方还有其他实质性囊外病变（白色箭头）。在翻修手术中，可以看到肺泡和金属病变的混合图像。 5.3.6 模块化锥形相关ALTR- MRI可以准确描述模块化股骨颈全髋关节置换术中归因于摩擦腐蚀的ALTR。MRI特征，尤其是最大滑膜厚度和滑膜炎体积，可以预测组织学严重程度( 22 , 23 ). 此外，如果由于敏感性伪影而未使用3D-MSI技术，则表面置换MOM关节成形术或MOM THA中耳轴周围的囊内ALTR可能会被遮挡。高带宽FSE或具有视角倾斜的FSE是不够的。 注1: 模块化锥形ALTR可能发生在非金属对金属植入物以及金属对金属关节成形术中。

1.1 This guide describes the recommended protocol for magnetic resonance imaging (MRI) studies of patients implanted with metal-on-metal (MOM) devices to determine if the periprosthetic tissues are likely to be associated with an adverse local tissue reaction (ALTR). Before scanning a patient with a specific implant, the MR practitioner shall confirm that the device is MR Conditional and that the scan protocol to be used satisfies the conditions for safe scanning for the specific implant. This guide assumes that the MRI protocol will be applied to MOM devices while they are implanted inside the body. It is also expected that standardized MRI safety measures will be followed during the performance of this scan protocol. 1.2 This guide covers the clinical evaluation of the tissues surrounding MOM hip replacement devices in patients using MRI. This guide is applicable to both total and resurfacing MOM hip systems. 1.3 The protocol contained in this guide applies to whole body magnetic resonance equipment, as defined in section 201.3.239 of IEC 60601-2-33, Ed. 3.2, with a whole body radiofrequency (RF) transmit coil as defined in section 201.3.240. The RF coil should have circulary polarized RF excitation (also commonly referred to as quadrature excitation) as defined in section 201.3.249 of IEC 60601-2-33, Ed. 3.2. 1.4 The values stated in SI units are to be regarded as standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. The user may consider all precautions and warnings provided in the MR system and hip implant labeling prior to determining the applicability of these protocols. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Magnetic resonance imaging is ideally suited to image MOM hip arthroplasty due to its superior soft tissue contrast, multiplanar capabilities and lack of ionizing radiation. MR imaging is the most accurate imaging modality for the assessment of peri-prosthetic osteolysis and wear-induced synovitis ( 19 , 20 ). 5.2 Before scanning a patient with a specific implant, the MR practitioner shall confirm that the device is MR Conditional and that the scan protocol to be used satisfies the conditions for safe scanning for the specific implant. 5.3 This guide can be used to identify the following adverse events. 5.3.1 Osteolysis— Magnetic resonance imaging is superior to conventional radiographs and computer tomography (CT) in the assessment of peri-prosthetic osteolysis and has been shown to be the most accurate method to locate and quantify the extent of peri-prosthetic osteolysis ( 19 , 21 ). On MR imaging, osteolysis appears as well marginated intraosseous intermediate to slightly increased signal intensity lesions that contrast with the high signal intensity of the intramedullary fat. A characteristic line of low signal intensity surrounds the area of focal marrow replacement, distinguishing the appearance of osteolysis from tumoral replacement of bone or infection ( 22 ). FIG. 4 Coronal (left) and Axial (right) FSE Images of a Left MOM Hip Arthroplasty Note 1: There is focal osteolysis (white arrows) in the greater trochanter, which manifests as well-demarcated intermediate signal intensity, similar to that of skeletal muscle, replacing the normal high signal intensity fatty marrow. Images courtesy of Dr. Hollis Potter. 5.3.2 Component Loosening— While the data are preliminary, MR imaging can identify circumferential bone resorption that may indicate component loosening. Loosening may result from osteolysis, circumferential fibrous membrane formation or poor osseous integration of a non-cemented component. On MR imaging, component loosening typically manifests as circumferential increased signal intensity at the metallic-bone or cement-bone interface on fat-suppressed techniques ( 20 ). The finding of circumferential fibrous membrane formation or osteolysis also indicates potential loosening; this is in contrast to a well-fixed component, with high signal intensity fatty marrow directly opposed to the implant interface. 5.3.3 Wear-Induced Synovitis— Magnetic resonance imaging is the most useful imaging modality to assess the intracapsular burden of wear-induced synovitis surrounding MOM arthroplasty ( 23 ). Preliminary data indicate that the signal characteristics of the synovial response on MR imaging correlate with the type of wear-induced synovitis demonstrated on histology at revision surgery ( 24 ). Low signal intensity debris is suggestive of metallic debris on histology. Mixed intermediate and low signal debris correlate with the presence of mixed polymeric (polyethylene and/or polymethyl methacrylate) and metallic debris at histology. Magnetic resonance imaging can demonstrate decompression of synovitis or fluid into adjacent bursae, such as the iliopsoas or trochanteric bursa, which can present as soft tissue masses or with secondary nerve compression. On occasion, wear-induced synovitis can result in a chronic indolent pattern of erosion of the surrounding bone, even in the absence of focal osteolytic lesions ( 6 ). FIG. 5 Axial (left) and Coronal (right) FSE Images of a Left MOM Hip Arthroplasty Note 1: Wear-induced synovitis decompresses into the abductor musculature where there is low signal intensity debris (arrow), consistent with metallic debris. Images courtesy of Dr. Hollis Potter. 5.3.4 Infection— In the setting of infection, the synovium often demonstrates a hyperintense, lamellated appearance with adjacent extracapsular soft tissue edema. These appearances help to distinguish the synovial pattern of infection from wear-induced synovitis, although aspiration is still required for definitive diagnosis ( 22 ). The presence of a soft tissue collection, draining sinus or osteomyelitis further supports the diagnosis of infection on MR imaging. FIG. 6 Axial FSE (left) and Inversion Recovery (right) Images of a Right MOM Hip Athroplasty Note 1: There is a lamellated synovitis (black arrow) with adjacent extracapsular soft tissue edema (white arrow). Infection was confirmed at subsequent aspiration. Images courtesy of Dr. Hollis Potter. 5.3.5 Adverse Local Tissue Response— Adverse local tissue reactions can manifest as synovitis, bursitis, osteolysis and cystic or solid masses adjacent to the arthroplasty, which may be termed pseudotumors ( 19 , 20 ). ALTR can also include the histopathologic feature of aseptic lymphocytic vasculitis-associated lesions (ALVAL), which can be confirmed at histology. A relatively common appearance of joints with ALVAL is expansion of the capsule with homogenous high signal fluid interspersed with intermediate signal intensity foci. More recent studies suggest that maximum synovial thickness and the presence of more solid synovial deposits highly correlate with tissue damage at revision surgery and necrosis at histologic inspection ( 15 ). FIG. 7 Axial FSE Image in a Right MOM Hip Arthroplasty Note 1: Fig. 7 demonstrates a large collection of fluid in the trochanteric bursa (arrow), which communicates with the hip joint via a dehiscence in the posterior pseudocapsule (not shown in these images). The fluid is high signal with fine intermediate signal intensity debris. A high ALVAL score was confirmed on histology at revision surgery. Images courtesy of Dr. Hollis Potter. FIG. 8 Axial FSE Image in a Right MOM Hip Resurfacing Arthroplasty Note 1: Fig. 8 demonstrates expansion of the pseudocapsule with fluid signal intensity decompressing into the trochanteric bursa. The pseudocapsule is thickened and of intermediate signal intensity (black arrows). There is additional solid extracapsular disease anteriorly (white arrow). At revision surgery, a mixed picture of ALVAL and metallosis was seen. 5.3.6 Modular Taper Associated ALTR— MRI can accurately describe ALTR attributed to tribocorrosion in modular femoral neck total hip arthroplasty. MRI characteristics, particularly maximal synovial thickness and synovitis volume, can predict histologic severity ( 22 , 23 ). In addition, intra-capsular ALTR around either resurfacing MOM arthroplasty or around the trunnion in MOM THA may be obscured if 3D-MSI techniques are not utilized due to the susceptibility artifact. High-bandwidth FSE or FSE with view-angle tilt are not sufficient. Note 1: Modular taper ALTR may occur in non-metal-on-metal implants as well as in metal-on-metal arthroplasty.