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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 (17-19).
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 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 (17, 18). 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 (20).
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 2.2.103 of IEC 60601-2-33, Ed. 3.0, with a whole body radiofrequency (RF) transmit coil as defined in section 2.2.100. The RF coil should have quadrature excitation.
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 and health 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A340 Terminology of Symbols and Definitions Relating to Magnetic Testing
F2503 Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment
IEC StandardIEC 60601-2-33, Ed. Medical Electrical Equipment--Part 2: Particular Requirements for the Safety of Magnetic Resonance Equipment for Medical Diagnosis, 2010