1、Designation: F 2052 06e1Standard Test Method forMeasurement of Magnetically Induced Displacement Forceon Medical Devices in the Magnetic ResonanceEnvironment1This standard is issued under the fixed designation F 2052; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEParagraph X1.3 was added editorially in May 2006.1. Scope1.1 This test metho
3、d covers the measurement of the mag-netically induced displacement force produced by static mag-netic field gradients on medical devices and the comparison ofthat force to the weight of the medical device.1.2 This test method does not address other possible safetyissues which include but are not lim
4、ited to issues of magneti-cally induced torque, RF heating, induced heating, acousticnoise, interaction among devices, and the functionality of thedevice and the MR system.1.3 This test method is intended for devices that can besuspended from a string. Devices which cannot be suspendedfrom a string
5、are not covered by this test method. The weightof the string from which the device is suspended during the testmust be less than 1 % of the weight of the tested device.1.4 This test method shall be carried out in a system inwhich the direction of the magnetically induced deflectionforce is horizonta
6、l.1.5 The values stated in SI units are to be regarded asstandard. Values in parentheses are for information only.1.6 This standard does 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 s
7、afety and health practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2F2119 Test Method for Evaluation of MR Image Artifactsfrom Passive ImplantsF 2182 Test Method for Measurement of Radio FrequencyInduced Heating Near Passive
8、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 Marking Medical Devices and OtherItems for Safety in the Magnetic Resonance Environment2.2 Other Standards:3IEC 606
9、01233 Ed. 2.0 Medical Electronic EquipmentPart 2: Particular Requirements for the Safety of MagneticResonance Equipment for Medical DiagnosisISO 13485:2003(E) Medical DevicesQuality Manage-ment SystemsRequirements for Regulatory Purposes,definition 3.73. Terminology3.1 Definitions:3.1.1 diamagnetic
10、materiala material whose relative per-meability is less than unity.3.1.2 ferromagnetic materiala material whose magneticmoments are ordered and parallel producing magnetization inone direction.3.1.3 magnetic field strength (H in A/m)strength of theapplied magnetic field.3.1.4 magnetic induction or m
11、agnetic flux density (B inT)that magnetic vector quantity which at any point in amagnetic field is measured either by the mechanical forceexperienced by an element of electric current at the point, or bythe electromotive force induced in an elementary loop duringany change in flux linkages with the
12、loop at the point. Themagnetic induction is frequently referred to as the magneticfield. Bois the static field in an MR system. Plain type indicatesa scalar (for example, B) and bold type indicates a vector (forexample, B).3.1.5 magnetic resonance diagnostic devicea device in-tended for general diag
13、nostic use to present images whichreflect the spatial distribution or magnetic resonance spectra, or1This test method is under the jurisdiction of ASTM Committee F04 on Medicalmetals (for surgical implants andmedical devices); MRI (magnetic resonance imaging); MRsafetyAPPENDIXES(Nonmandatory Informa
14、tion)X1. RATIONALE FOR DEVELOPMENT OF THE TEST METHODX1.1 The primary reason for this test method is to deter-mine the magnetically induced deflection force on medicaldevices that may be subjected to magnetic resonance imaging.Note that this test method only addresses the magneticallyinduced deflect
15、ion force and that the results of this test aloneare not sufficient to determine whether a particular device issafe in the MR environment. The deflection force is producedby the static magnetic field gradients. The static field alsoproduces a torque on a device that acts to align the object withthe
16、magnetic field (like a compass needle aligns itself with theEarths magnetic field). For a device to be safe in the MRenvironment, the magnetically induced deflection force andtorque should be less than forces and torques to which thedevice would be subjected if it were not in a large magneticfield,
17、for example, a force less than the weight of the deviceand a torque less than that produced by normal daily activities(which might include rapidly accelerating vehicles or amuse-ment park rides). Other possible safety issues include but arenot limited to RF heating, induced heating, acoustic noise,i
18、nteraction among devices, and the functionality of the deviceand the MR system. Although a commercial 1.5 T MR systemcurrently produces the conditions that would most commonlybe encountered by a medical device, 3 T MR systems havebeen cleared for market and are becoming more common inclinical situat
19、ions. It is important to note that a medical devicethat is safe in a 1.5 T scanner may not be so in a system withhigher or lower static field strength (for example, a 3 T systemor a 1 T system). Also, there can be major differences in thecharacteristics of open and cylindrical MR systems. Forinstanc
20、e, the static field spatial gradients may be significantlyhigher in open systems.X1.1.1 After the safety of a device has been determined, itshould be marked as MR Safe, MR Conditional, or MR Unsafeusing the definitions and icons given in Practice F 2503. Theterms are defined in Practice F 2503 as:X1
21、.1.2 MR Safean item that poses no known hazards inall MR environments.NOTE X1.1MR Safe items include nonconducting, nonmagneticitems such as a plastic Petri dish. An item may be determined to be MRSafe by providing a scientifically based rationale rather than test data.X1.1.3 MR Conditionalan item t
22、hat has been demon-strated to pose no known hazards in a specified MR environ-ment with specified conditions of use. Field conditions thatdefine the specified MR environment include field strength,spatial gradient, dB/dt (time rate of change of the magneticfield), radio frequency (RF) fields, and sp
23、ecific absorption rate(SAR).Additional conditions, including specific configurationsof the item, may be required.X1.1.4 MR Unsafean item that is known to pose hazardsin all MR environments.NOTE X1.2MR Unsafe items include magnetic items such as a pair offerromagnetic scissors.X1.2 Test Method F2119p
24、rovides a method for evaluatingimage artifact for passive medical implants. Other methodsmay be needed to assess the image artifact from other devices.X1.3 This test method was revised in 2005 to reference theMR safety terminology in Practice F 2503. The historicaldefinitions for MR safe and MR comp
25、atible were removed andthe definitions of MR safe, MR conditional, and MR unsafewere inserted. Definitions for MR environment, medical de-vice, and MR system were revised to be in agreement with thedefinitions in Practice F 2503.F205206e14X2. DERIVATION OF FORCE RELATION GIVEN IN 8.4X2.1Definitions
26、of symbols:Ts= tension in stringTm= torque due to magnetic fieldFm= magnetically induced deflection force due to mag-netic field spatial gradientL = distance from string attachment to center of mass ofdevicem = mass of devicea = angular deflection of string measured with protractoru = angular rotati
27、on of deviceg = acceleration due to gravityAssumptions:1. Magnetism is a body force like gravity.2. The center of magnetic force is not required to coincidewith the center of mass, though the two locations are shown tobe coincident in Fig. X2.1. The force equations written beloware independent of th
28、e point of application of the magneticallyinduced force and torque.3. The device is oriented in the magnetic field so that FmandTmare the only components of magnetically induced force andtorque.Summing forces in the free body diagram in Fig. X2.1:SFz5 0 5 Fm Tssina (X2.1)SFy5 0 5 Tscosa mg (X2.2)Sol
29、ving the two equations gives Fm= mg tana.Note that the solution is independent of the point ofattachment of the string. Also note that because the derivationof the relation for Fmuses only the force equilibrium equations,the relation for Fmalso holds if the center of magnetic forcedoes not coincide
30、with the center of mass, as might be the casefor a device composed of more than one material.REFERENCES(1) Gegauff, A. G., Laurell, K. A., Thavendrarajah, A., and Rosenstiel, S.F., “A Potential MRI Hazard: Forces on Dental Magnet Keepers,”Journal of Oral Rehabilitation, vol. 17, 1990, pp. 403410.(2)
31、 Kagetsu, N. J., and Litt, A. W., “Important Considerations in Mea-surement of Attractive Force on Metallic Implants in MR Imagers,”Radiology, vol. 179, 1991, pp. 505508.(3) Kanal, E., and Shellock, F. G., “Aneurysm Clips: Effects of Long-termand Multiple Exposures to a 1.5-T MR System,” Radiology,
32、vol. 210,1999, pp. 563565.(4) New, P. F., Rosen, B. R., Brady, T., J., Buonarmo, F. S., Kistler, J. P.,Burt, C. T., Hinshaw, W. S., Newhouse, J. H., Pohost, G. M., andTaveras, J. M., “Potential Hazards and Artifacts of Ferromagnetic andNonferromagnetic Surgical and Dental Materials and Devices inNuc
33、lear Magnetic Resonance Imaging,” Radiology, vol. 147, 1983, pp.139148.(5) Planert, J., Modler, H., and Vosshenrich, R., “Measurements ofMagnetism-Related Forces and Torque Moments Affecting MedicalInstruments, Implants, and Foreign Objects During Magnetic Reso-nance Imaging at all Degrees of Freedo
34、m,” Medical Physics, vol. 23,1996, pp. 851856.(6) Planert, J., Modler, H., Ljdecke, and Eger, M., “A MiniaturisedForce-Torque Sensor with Six Degrees of Freedom for Dental Mea-surements,” Clin. Phys. Physiol. Meas., vol. 13, 1992, pp. 241248.(7) Schenck, J. F., “The Role of Magnetic Susceptibility i
35、n MagneticResonance Imaging: MRI Magnetic Compatibility of the First andSecond Kinds,” Medical Physics, vol. 23, 1996, pp. 815850.(8) Shellock, F. G., and Kanal, E., “Yasargil Aneurysm Clips: Evaluationof Interactions with a 1.5-T MR System,” Radiology, vol. 207, 1998,pp. 587591.(9) Shellock, F. G.,
36、 and Shellock, V. J., “Cardiovascular Catheters andAccessories: Ex Vivo Testing of Ferromagnetism, Heating, and Arti-facts Associated with MRI,” JMRI, vol. 8, 1998, pp. 13381342.(10) Shellock, F. G., and Shellock, V. J., “Cranial Bone Flap FixationClamps: Compatibility at MR Imaging,” Radiology, vol
37、. 207, 1998,pp. 822825.(11) Teitelbaum, G.P., Lin, M.C.W., Watanabe, A.T., Nogray, J.F., Young,T.I., and Bradley, W. G., Jr., “Ferromagnetism and MR Imaging:Safety of Carotid Vascular Clamps,” American Journal of Neurora-diology, vol. 11, 1990, pp. 267272.(12) Teitelbaum, G. P., Yee, C. A., Van Horn
38、, D. D., Kim, H. S., andColletti, P. M., “Metallic Ballistic Fragments: MR Imaging Safetyand Artifacts,” Radiology, vol. 175, 1990, pp. 885859.FIG. X2.1 Free Body Diagram of Device in Magnetic FieldF205206e15ASTM International takes no position respecting the validity of any patent rights asserted i
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