1、Designation: F2978 13Guide toOptimize Scan Sequences for Clinical Diagnostic Evaluationof Metal-on-Metal Hip Arthroplasty Devices using MagneticResonance Imaging1This standard is issued under the fixed designation F2978; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the recommended protocol formagnetic resonance
3、imaging (MRI) studies of patients im-planted with metal-on-metal (MOM) devices to determine ifthe periprosthetic tissues are likely to be associated with anadverse local tissue reaction (ALTR). Before scanning a patientwith a specific implant, the MR practitioner shall confirm thatthe device is MR C
4、onditional and that the scan protocol to beused satisfies the conditions for safe scanning for the specificimplant. This guide assumes that the MRI protocol will beapplied to MOM devices while they are implanted inside thebody. It is also expected that standardized MRI safety measureswill be followe
5、d during the performance of this scan protocol.1.2 This guide covers the clinical evaluation of the tissuessurrounding MOM hip replacement devices in patients usingMRI. This guide is applicable to both total and resurfacingMOM hip systems.1.3 The protocol contained in this guide applies to wholebody
6、 magnetic resonance equipment, as defined in section2.2.103 of IEC 60601-2-33, Ed. 3.0, with a whole bodyradiofrequency (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 asstandard.1.5 This standard doe
7、s not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. The user mayconsider all precaution
8、s and warnings provided in the MRsystem and hip implant labeling prior to determining theapplicability of these protocols.2. Referenced Documents2.1 ASTM Standards:2A340 Terminology of Symbols and Definitions Relating toMagnetic TestingF2503 Practice for Marking Medical Devices and OtherItems for Sa
9、fety in the Magnetic Resonance Environment2.2 IEC Standard:3IEC 60601-2-33, Ed. 3.0 Medical Electrical EquipmentPart 2: Particular Requirements for the Safety of MagneticResonance Equipment for Medical Diagnosis, 20103. Terminology3.1 DefinitionsFor the purposes of this standard thefollowing definit
10、ions shall apply:3.1.1 Magnetic Resonance Imaging (MRI)diagnostic im-aging technique that uses static and time varying magneticfields to provide tomographic images of tissue by the magneticresonance of nuclei.3.1.2 MR - Conditionalan item that has been demon-strated to pose no known hazards in a spe
11、cific MR environmentwith specified conditions of use. Field conditions that definethe specified MR environment include field strength, spatialgradient, dB/dt (time rate of change of the magnetic field),radiofrequency (RF) fields, and specific absorption rate (SAR).Additional conditions, including sp
12、ecific configurations of theitem, may be required (Practice F2503).3.1.3 Metal-on-Metal (MOM) hip replacementa hip ar-throplasty device in which the articulating surfaces of thefemoral head and the acetabular cup are fabricated from metal.4. Summary of Protocol4.1 Surface coil fast spin echo (FSE) s
13、equences of theaffected hip in three planes and a larger field-of-view (FOV)short tau inversion recovery (STIR) sequence to include both1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on A
14、rthroplasty.Current edition approved Dec. 1, 2013. Published May 2014. DOI: 10.1520/F2978-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document
15、Summary page onthe ASTM website.3Available from International Electrotechnical Commission (IEC), 3, rue deVaremb, P.O. Box 131, CH-1211 Geneva 20, Switzerland, http:/www.iec.ch.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1hips and
16、the surrounding pelvis are recommended. A largeFOV sequence of the entire pelvis should be included to assessfor remote causes of pain, such as pelvic or sacral fractures,which may be referred to the hip.4.2 With regards to the FSE surface coil imaging, anintermediate echo time, water-sensitive fast
17、 spin echo tech-nique is effective in highlighting osteolysis and detectingwear-induced synovitis. The fluid-sensitive inversion recoverysequence helps outline fluid collections and will demonstratethe presence of marrow edema in the setting of implantloosening or peri-prosthetic fracture (1).4.3 Mo
18、difications of standard pulse sequence parametersshould be applied when imaging in the presence of metallicimplants. Options available to reduce susceptibility artifacts onroutine clinical scanners include increasing the amplitude ofthe readout gradient by the use of a wider receiver bandwidthand th
19、inner slices (2, 3). Decreasing voxel size by the use of ahigh-resolution matrix will increase spatial resolution andtrabecular detail in the face of the susceptibility artifact.However, these techniques will also decrease the signal-to-noise ratio. Orienting the frequency encoding direction alongth
20、e long axis of the prosthesis can also be effective indecreasing artifacts but may not be feasible (4). In addition,view-angle tilting (VAT) gradients can be applied, whichapplies a section-selection gradient during the signal readout(5).4.4 Techniques to avoid when imaging in the presence ofmetal i
21、nclude imaging at high field strengths, use of frequency-selective fat suppression and use of gradient echo sequences.Susceptibility artifact is directly proportional to the mainmagnetic field (B0); therefore, imaging at field strengthsgreater than 1.5 T should be avoided when possible. When fatsupp
22、ression is required, inversion recovery sequences arepreferred over frequency-selective fat suppression techniques,as they are less susceptible to magnetic field inhomogeneities.Standardized gradient echo imaging should be avoided, asthese sequences lack the 180 refocusing pulse of spin echosequence
23、s, resulting in rapid dephasing of spins and large areasof signal void in the presence of metal.4.5 Table 1 outlines a suggested protocol for imaging MOMhip arthroplasty using a 1.5 Tesla (T) clinical scanner (6).4.6 Multi-acquisition variable-resonance image combina-tion (MAVRIC SL) is a new techni
24、que that results in an imagewith markedly reducd susceptibility artifact (7-9). Early studieshave demonstrated decreased image distortion at the bone-implant interface and improved detection of peri-prostheticosteolysis and synovitis when compared to conventional fastspin echo techniques (10).Arecen
25、tly reported study of patientswith either MOM resurfacing or MOM total hip arthroplastydemonstrated synovitis using the MAVRIC sequence in 77.4%of resurfacing arthroplasty and 86.2% of total hip arthroplasty(THA) hips (11). For imaging MOM arthroplasty, the use of aMAVRIC sequence is recommended in
26、at least one plane(coronal or axial) when this sequence is available. Specificparameters are listed in Appendix X2. With regards to timing,this protocol has been successful in assessing patients for bothimmediate and delayed complications, including fracture,nerve impingement and tendon tears in the
27、 immediate postop-erative period, and adverse tissue reactions, infection andpotential loosening in the later postoperative period (6, 12-14).TABLE 1 Suggested Protocol for Metal-on-Metal Hip Arthroplasty Imaging at a 1.5 T MRI ScannerA,BTimingParametersAxialFSE/TSECoronal FIRCoronalFSE/TSEAxial FSE
28、SagittalFSE/TSECoilBodyCoilBodyCoilSurfaceCoilSurfaceCoilSurfaceCoilTR, msec 4,500 - 5 500 4,500 4,500 - 5,800 4,500-5,500 5,500-6,500TE, msec 21.4 - 32.0 18 24 - 30 24 - 30 23 - 30TI, msec . . . 150 . . . . . . . . .Number of echoes 16 - 20 7 - 9 10 - 20 10 - 20 14 - 20BW, kHz 83 - 100 83 - 100 83
29、- 100 83 - 100 83 - 100FOV, cm 32 - 36 34 - 36 18 17 - 19 18 - 20Matrix 512 256 256 192 512 352 512 256 - 288 512 352Slice thickness, mm 5 5 4 4 2.5 - 3Interslice gap, mm 0 0 0 0 0Number of averages 4 2 4 - 5 4 - 5 4 - 5No phase wrap yes yes yes yes yesSwap phaseand frequencyyes yes yes yes yesVaria
30、ble BW yes yes yes yes yesFrequency direction anterior toposteriorright toleftright toleftanterior toposterioranterior toposteriorAAbbreviations:BW bandwidth.FIR fast inversion recovery.FOV field of view.FSE fast spin echo.TSE turbo spin echo.KHz kiloHertz.TE echo time.TI inversion time.TR repetitio
31、n time.BDepending on the MRI system, the BW may be reported as half-bandwidth (maximum frequency), so a reported BW of 62.5 is actually acquired at 125 Hz over the entirefrequency range. For Table 1, to convert to Hz/pixel when implementing 512 frequency encoding steps, use the following formula: (k
32、Hz x 2000)/512.F2978 132Additional prototype sequences are in development and willbecome available for such imaging including slice encoding formetal artifact correction (SEMAC), which is a variant of theVAT principle that adds additional phase-encoding steps in theslice dimension (9, 15). Currently
33、, a commercially availablesequence applies the SEMAC principle and is termed theWARP sequence, which is a high bandwidth protocol thatincludes the VAT technique (16).5. Significance and Use5.1 Magnetic resonance imaging is ideally suited to imageMOM hip arthroplasty due to its superior soft tissue c
34、ontrast,multiplanar capabilities and lack of ionizing radiation. MRimaging is the most accurate imaging modality for the assess-ment of peri-prosthetic osteolysis and wear-induced synovitis(17-19).5.2 Before scanning a patient with a specific implant, theMR practitioner shall confirm that the device
35、 is MR Condi-tional and that the scan protocol to be used satisfies theconditions for safe scanning for the specific implant.5.3 This guide can be used to identify the following adverseevents.5.3.1 OsteolysisMagnetic resonance imaging is superiorto conventional radiographs and CT in the assessment o
36、fperi-prosthetic osteolysis and has been shown to be the mostaccurate method to locate and quantify the extent of peri-prosthetic osteolysis (17, 18). On MR imaging, osteolysisappears as well marginated intraosseous intermediate toslightly increased signal intensity lesions that contrast with thehig
37、h signal intensity of the intramedullary fat. A characteristicline of low signal intensity surrounds the area of focal marrowreplacement, distinguishing the appearance of osteolysis fromtumoral replacement of bone or infection (20).5.3.2 Component LooseningWhile the data arepreliminary, MR imaging c
38、an identify circumferential boneresorption that may indicate component loosening. Looseningmay result from osteolysis, circumferential fibrous membraneformation or poor osseous integration of a non-cementedcomponent. On MR imaging, component loosening typicallymanifests as circumferential increased
39、signal intensity at themetallic-bone or cement-bone interface on fat-suppressed tech-niques (19). The finding of circumferential fibrous membraneformation or osteolysis also indicates potential loosening; thisis in contrast to a well-fixed component, with high signalintensity fatty marrow directly o
40、pposed to the implant inter-face.5.3.3 Wear-Induced SynovitisMagnetic resonance imag-ing is the most useful imaging modality to assess the intraca-psular burden of wear-induced synovitis surrounding MOMarthroplasty (21). Preliminary data indicate that the signalcharacteristics of the synovial respon
41、se on MR imaging corre-late with the type of wear-induced synovitis demonstrated onhistology at revision surgery (22). Low signal intensity debrisis suggestive of metallic debris on histology. Mixed interme-diate and low signal debris correlates with the presence ofmixed polymeric (polyethylene and/
42、or polymethyl methacry-late) and metallic debris at histology. Magnetic resonanceimaging can demonstrate decompression of synovitis or fluidinto adjacent bursae, such as the iliopsoas or trochanteric bursa,which can present as soft tissue masses or with secondarynerve compression. On occasion, wear-
43、induced synovitis canresult in a chronic indolent pattern of erosion of the surround-ing bone, even in the absence of focal osteolytic lesions (6).5.3.4 InfectionIn the setting of infection, the synoviumoften demonstrates a hyperintense, lamellated appearance withadjacent extracapsular soft tissue e
44、dema. These appearanceshelp to distinguish the synovial pattern of infection fromwear-induced synovitis, although aspiration is still required fordefinitive diagnosis (14). The presence of a soft tissuecollection, draining sinus or osteomyelitis further supports thediagnosis of infection on MR imagi
45、ng.NOTE 1Note the improved visualization of synovitis (white arrows)and the bone-prosthesis interface (black arrow) on the MAVRIC image.Images courtesy of Dr. Hollis Potter.FIG. 1 Coronal FSE (Left) and MAVRIC (Right) Images of a LeftMOM Hip ArthroplastyF2978 1335.3.5 Adverse Local Tissue ResponseAd
46、verse local tissuereactions can manifest as synovitis, bursitis, osteolysis andcystic or solid masses adjacent to the arthroplasty, which maybe termed pseudotumors (17-19). ALTR can also include thehistopathologic feature of aseptic lymphocytic vasculitis-associated lesions (ALVAL), which can be con
47、firmed usinghistology. A relatively common appearance of joints withALVAL is expansion of the pseudocapsule with homogenoushigh signal fluid interspersed with intermediate signal intensityfoci. More recent studies suggest that maximum synovialthickness and the presence of more solid synovial deposit
48、shighly correlate with tissue damage at revision surgery andnecrosis at histologic inspection (12).6. Apparatus6.1 MRI SpecificationThe MRI apparatus consists of amagnet using whole body RF quadrature excitation (refer to1.3). Imaging is recommended to be conducted at a magneticfield strength of 1.5
49、 T and should have the capabilities toperform the sequences suggested in 4.5. Higher field opensystems, such as 1.0 T and 1.2 T open systems, may alsoprovide acceptable performance provided the protocols areNOTE 1There is focal osteolysis (white arrows) in the greatertrochanter, which manifests as well-demarcated intermediate signalintensity, similar to that of skeletal muscle, replacing the normal highsignal intensity fatty marrow. Images courtesy of Dr. Hollis Potter.FIG. 2 Coronal (Left) and Axial (Right) FSE Images of a Left MOMHip Art
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