1、Designation: F 2119 07Standard Test Method forEvaluation of MR Image Artifacts from Passive Implants1This standard is issued under the fixed designation F 2119; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method characterizes the distortion and signalloss artifacts produced in a magnetic resonance (MR) image bya passive
3、implant (implant that functions without the supply ofelectrical or external power). Anything not established to beMR-Safe or MR-Conditional is excluded.2. Referenced Documents2.1 ASTM Standards:2F 2052 Test Method for Measurement of Magnetically In-duced Displacement Force on Medical Devices in theM
4、agnetic Resonance EnvironmentF 2182 Test Method for Measurement of Radio FrequencyInduced Heating Near Passive Implants During MagneticResonance ImagingF 2213 Test Method for Measurement of Magnetically In-duced Torque on Medical Devices in the Magnetic Reso-nance EnvironmentF 2503 Practice for Mark
5、ing Medical Devices and OtherItems for Safety in the Magnetic Resonance Environment3. Terminology3.1 Definitions3.1.1 artifact width, nthe maximum distance (mm) fromthe edge of the implant to the fringe of the resulting imageartifact found in the entire set of images acquired using this testmethod.3
6、.1.2 image artifact, na pixel in an image is considered tobe part of an image artifact if the intensity is changed by atleast 30 % when the device is present compared to a referenceimage in which the device is absent.3.1.3 magnetic resonance (MR) environment, nvolumewithin the 0.50 mT (5 gauss (G) l
7、ine of an MR system, whichincludes the entire three dimensional volume of space sur-rounding the MR scanner. For cases where the 0.50 mT line iscontained within the Faraday shielded volume, the entire roomshall be considered the MR environment.3.1.4 magnetic resonance imaging (MRI), nimaging tech-ni
8、que that uses static and time varying magnetic fields toprovide images of tissue by the magnetic resonance of nuclei.3.1.5 MR-Conditional, adjan item that has been demon-strated to pose no known hazards in a specified MR environ-ment with specified conditions of use. Field conditions thatdefine the
9、specified MR environment include field strength,spatial gradient, dB/dt (time rate of change of the magneticfield), radio frequency (RF) fields, and specific absorption rate(SAR).Additional conditions, including specific configurationsof the item, may be required.3.1.6 MR-Safe, adjan item that poses
10、 no known hazardsin all MR environments.NOTE 1MR-Safe items include nonconducting, nonmagnetic itemssuch as a plastic petri dish. An item may be determined to be MR-Safe byproviding a scientifically based rationale rather than test data.3.1.7 MR-Unsafe, adjan item that is known to posehazards in all
11、 MR environments.NOTE 2MR-Unsafe items include magnetic items such as a pair offerromagnetic scissors.3.1.8 tesla (T), nthe SI unit of magnetic induction equal to104G.4. Summary of Test Method4.1 Pairs of spin echo images are generated both with andwithout the implant in the field of view. Image art
12、ifacts areassessed by computing differences outside the region corre-sponding to the implant between reference and implant images.Once the worst case conditions using the spin echo pulsesequence are ascertained, a pair of gradient echo images areacquired under the same conditions.5. Significance and
13、 Use5.1 This test method provides a quantified measure of theimage artifact produced under a standard set of scanningconditions.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of subcommitteeF04.15 on Mat
14、erial Test Methods.Current edition approved Sept. 1, 2007. Published September 2007. Originallyapproved in 2001. Last previous edition approved in 2001 as F 2119 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo
15、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 This test method applies only to passive implants thathave been established t
16、o be MR-Safe or MR-Conditional.6. Apparatus6.1 An MR imaging system with a static field strength of 1.5T or 3.0 T is recommended. The MRI system must have theability to swap readout and phase-encode directions.6.2 A reference object made from a nondistorting medium,such as 0.5-in. diameter nylon rod
17、.7. Test Specimen7.1 The implant for which image artifact is to be measuredshall serve as the test specimen.7.2 For the purposes of device qualification, the deviceevaluated according to this test method should be a finishedsterilized device.NOTE 3The device does not have to be sterile at the time o
18、f testing;however, it should have been subjected to all processing, packaging, andsterilization steps before testing because any of these steps may affect themagnetic properties of the device.7.3 This test method may be used on prototype devices atany stage of production during product development.
19、A justi-fication for using a prototype instead of the finished devicemust be provided.8. Procedure8.1 MR Imaging Parameters for Testing Artifacts:8.1.1 The recommended MR imaging test environment forevaluation of artifacts are given as follows. An alternative maybe used if an adequate case can be ma
20、de for relevance to thespecific device. Field of view, slice thickness, and matrix sizeshall be adjusted to achieve pixel dimensions to accuratelymeasure the artifact. Two example situations are described, onefor small implants, such as a coronary stent, and one for largerimplants such as an artific
21、ial hip joint.Static field strength: 1.5T (see 6.1)Bandwidth: 32 kHz (required)Field of view: sufficient to encompass the entire implantand the artifactSmall implant (for example, coronary stent):Matrix size: 256 3 256Slice thickness: 3 mmLarge implant (for example, hip implant):Matrix size: 256 3 1
22、28Slice thickness: 5 mmTwo different pulse sequences will be used:Pulse sequence: spin echoTR: 500 msTE: 20 msPulse sequence: gradient echoTR: 100 500 msTE: 15 msFlip angle: 308.1.2 The device should be immersed in a solution. Forexample, a copper sulfate (CuSO4) solution (12 g/L) may beused to redu
23、ce T1and keep TR at a reasonable level. Thedevice may be suspended in nylon netting. If a copper sulfatesolution is inappropriate for a particular device, a substitutemay be used but a justification must be provided. Nickelchloride (NiCl2) and manganese chloride (MnCl2) are possiblesubstitutes. To a
24、chieve adequate field homogeneity, thereshould be at least 4 cm of clearance between the device andeach side of the container holding the solution and the implant.8.1.3 Each image must contain a reference object, (made ofnylon or some other material, which does not cause distortion),so that the posi
25、tion of the device may be accurately assessed.For example, a section of 0.5-in. diameter nylon rod positionedso that it appears as a circle in the image could serve as thereference object. Each image must also contain a physical sizescale, generally displayed on MR images, so that distances maybe me
26、asured.8.2 Set of Images To Be Acquired:8.2.1 A complete set of spin echo image pairs, as describedin 8.2.2-8.2.4, shall be acquired.8.2.2 An individual test image pair shall consist of an imageof the reference object only, and an image containing both thereference object and the device being tested
27、. The device mustbe tested in three mutually orthogonal orientations relative tothe static field. Orientations for which the implant will not fit inthe bore may be omitted. Cylindrically symmetric devices maybe tested parallel to the static field and in just one directionperpendicular to the static
28、field. Sagittal, relative to static fielddirection, images should be acquired in all cases.8.2.3 For images containing both the device being testedand the reference object, for each orientation two sets ofimages must be acquired using both possibilities for designa-tion of readout and phase-encode d
29、irections. For imagescontaining the reference object only, one image is acquiredusing either possibility for designation of readout and phase-encode direction. The reference object is oriented along theright-left axis so that it extends beyond the length of the devicebeing tested so that the referen
30、ce object will appear in eachimage containing the tested device.8.2.4 For each image pair and each orientation and eachreadout/phase-encode direction designation, a sufficient num-ber of contiguous slices to span the entire device must beacquired. So, for example, a device that is completely con-tai
31、ned within one slice will require three orientations times tworeadout/phase-encode designations = six images containing thedevice being tested + three images containing the referenceobject only.8.2.5 For the worst case (largest artifact size) set of condi-tions (orientation, readout/phase-encode des
32、ignation, and slicenumber) from the set of spin echo images, an image pair (see8.2.2) using the gradient echo pulse sequence must be ac-quired. It is probably most time efficient to acquire theseimages while the object is in position for acquiring the spinecho images.8.3 Measurement of Artifact Size
33、:8.3.1 The distance (in mm) from the device boundary to thefringe of the artifact (630 % zone, see 3.1.2) should bemeasured. To compute the distance in mm, take the distance inpixels and multiply by the ratio of the field of view (FOV)expressed in mm to the matrix dimension (m) also measured inmm. D
34、istance (mm) = Distance (pixels) 3 FOV/m. Thisdistance may be evaluated quantitatively at the system consoleF2119072using software, commonly included with MRI scanners, to plotintensity profiles. Alternatively, if necessary, the distance maybe evaluated visually at the console or on film but in this
35、 casea conservative definition of the artifact fringe location shouldbe adopted to ensure that artifact size is not underestimated.For each image, the artifact must be characterized by the worstcase (maximum) distance as the boundary of the device iscompletely circumscribed. The worst case (maximum)
36、 distancefound in the entire set of images acquired (as prescribed above)must be used to characterize the artifact.8.3.2 Difficulty may arise if the MRI image consists of avoid corresponding to the implant surrounded by a voidcorresponding to the artifact. The boundary of the implant maynot be visib
37、le. In this case, the border of the implant, measuredwithout MRI, for example, using a ruler or calipers, may besuperimposed in the center of the void so that distances fromimplant boundary to the artifact fringe can be measured. Thesuperimposed implant border should be scaled to match theMRI image
38、distance scale.9. Report9.1 The report shall include the following for each specimentested:9.1.1 Device product description.9.1.2 Device product number and lot number.9.1.3 Device size (physical dimensions).9.1.4 The gradient echo image pair and a representative setof spin echo images, including tho
39、se that exhibit the worstartifacts.9.1.5 MRI system make, model, and static field strength.9.1.6 MRI parameters including TR, TE, bandwidth, re-ceiver, field of view, matrix size, and coil used.9.1.7 The method used for measuring artifact.9.1.8 Spin echo artifact width and gradient echo artifactwidt
40、h, (see 3.1.1).9.1.9 Solution (and solution concentration) used to immersethe device. If a CuSO4solution is not used, include ajustification for the solution used.10. Precision and Bias10.1 The precision and bias of this test method have notbeen established.11. Keywords11.1 image artifact; implant;
41、metals for surgical implants;MRI (magnetic resonance imaging); MR compatibility; MRsafetyAPPENDIX(Nonmandatory Information)X1. RATIONALE FOR DEVELOPMENT OF THE TEST METHODX1.1 This test method characterizes the artifact producedby a passive implant, which has been determined to beMR-Safe or MR-Condi
42、tional. Test Methods F 2052 and F 2213can be used to determine magnetically induced displacementforce and torque, respectively, on a medical device in the MRenvironment, and Test Method F 2182 can be used to measureradio frequency induced heating during MRI. Although acommercial 1.5 T MR system curr
43、ently produces the condi-tions that are most commonly encountered, 3 T MR systemshave been cleared for market and are becoming more commonin clinical situations.X1.2 The size of an artifact induced by a passive implant ina given MR environment has a complex relationship to implantsize, shape, and co
44、mposition. Acceptability of an artifact willdepend on implant type and location in addition to which partof the body is being imaged. The protocol described in this testmethod provides an objective basis for quantifying the extentof an artifact associated with an implant. This information maybe used
45、 to compare potential artifact sizes for many implantsand may be useful for health care professionals in selectingimplants for various applications.X1.3 For most applications, image artifacts are smaller forfast spin echo pulse sequences than conventional spin echo andgradient echo pulse sequences;
46、however, the combined use ofspin echo and gradient echo pulse sequences in the test methodprovides a valid method for ranking implants with regard totendency to produce artifacts under controlled conditions.X1.4 This test method was revised in 2007 to reference theMR safety terminology in Practice F
47、 2503 and the MR TestMethods F 2182, F 2213, and F 2052. The historical definitionsfor MR safe and MR compatible were removed and thedefinitions of MR-Safe, MR-Conditional, and MR-Unsafewere inserted. The definition for MR environment was revisedto be in agreement with the definitions in Practice F
48、2503.F2119073BIBLIOGRAPHY(1) Schenck, J. F., “The Role of Magnetic Susceptibility in MagneticResonance Imaging: MRI Magnetic Compatibility of the First andSecond Kinds,” Med. Phys., 23 (6), June 1996, pp. 815850.(2) Shellock, F. G., and Kanal E., Magnetic Resonance: Bioeffects,Safety, and Patient Ma
49、nagement, Second edition, Lippincott -Raven, Philadelphia, PA, 1996.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or with
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