1、Designation: F 2213 06Standard Test Method forMeasurement of Magnetically Induced Torque on MedicalDevices in the Magnetic Resonance Environment1This standard is issued under the fixed designation F 2213; the number immediately following the designation indicates the year oforiginal adoption or, in
2、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.1. Scope1.1 This test method covers the measurement of the mag-netically induced torque produce
3、d by the static magnetic fieldin the magnetic resonance environment on medical devices andthe comparison of that torque to the equivalent torque appliedby the gravitational force to the implant.1.2 This test method does not address other possible safetyissues which include but are not limited to iss
4、ues of magneti-cally induced force due to spatial gradients in the staticmagnetic field, RF heating, induced heating, acoustic noise,interaction among devices, and the functionality of the deviceand the MR system.1.3 The torque considered here is the magneto-static torquedue to the interaction of th
5、e MRI static magnetic field with themagnetization in the implant. The dynamic torque due tointeraction of the static field with eddy currents induced in arotating device is not addressed in this test method. Currents inlead wires may induce a torque as well.1.4 The sensitivity of the torque measurem
6、ent apparatusmust be greater than110 the “gravity torque,” the product of thedevices maximum linear dimension and its weight.1.5 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 app
7、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F 2052 Test Method for Measurement of Magnetically In-duced Displacement Force on Medical Devices in theMagnetic Resonance EnvironmentF2119 Test Me
8、thod for Evaluation of MR Image Artifactsfrom Passive ImplantsF 2182 Test Method for Measurement of Radio FrequencyInduced Heating Near Passive Implants During MagneticResonance ImagingF 2503 Practice for Marking Medical Devices and OtherItems for Safety in the Magnetic Resonance Environment2.2 Othe
9、r Standards:IEC 60601-2-33 Ed. 2.0 Medical Electrical EquipmentPart 2: Particular Requirements for the Safety of MagneticResonance Equipment for Medical Diagnosis, 20023ISO 13485:2003(E) Medical DevicesQuality Manage-ment SystemsRequirements for Regulatory Purposes,definition 3.733. Terminology3.1 D
10、efinitionsFor the purposes of this test method, thedefinitions in 3.1.1-3.1.18 shall apply:3.1.1 diamagnetic 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 directio
11、n.3.1.3 magnetic induction or magnetic 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 ch
12、ange in flux linkages with the loop at the point. Themagnetic induction is frequently referred to as the magneticfield. B0is the static field in an MR system. Plain type indicatesa scalar (for example, B) and bold type indicates a vector (forexample, B).3.1.4 magnetic field strength (H in A/m)streng
13、th of theapplied magnetic field.3.1.5 magnetic resonance (MR)resonant absorption ofelectromagnetic energy by an ensemble of atomic particlesituated in a magnetic field.3.1.6 magnetic resonance diagnostic devicea device in-tended for general diagnostic use to present images which1This test method is
14、under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved May 1, 2006. Published June 2006. Originallyapproved in 2002. Last previous edition approved in 2004 as F
15、 2213 04.2For 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 Summary page onthe ASTM website.3Available from American National Standards Institut
16、e (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.reflect the spatial distribution or magnetic resonance spectra, orboth, which reflect frequency and distribution of nuclei exhib-i
17、ting nuclear magnetic resonance. Other physical parametersderived from the images or spectra, or both, may also beproduced.3.1.7 magnetic resonance (MR) environmentvolumewithin the 0.50 mT (5 gauss (G) line of an MR system, whichincludes the entire three dimensional volume of space sur-rounding the
18、MR scanner. For cases where the 0.50 mT line iscontained within the Faraday shielded volume, the entire roomshall be considered the MR environment.3.1.8 magnetic resonance equipmentmedical electricalequipment which is intended for in-vivo magnetic resonanceexamination of a patient. The MR equipment
19、comprises allparts in hardware and software from the supply mains to thedisplay monitor. The MR equipment is a ProgrammableElectrical Medical System (PEMS).3.1.9 magnetic resonance examination (MRExamination)process of acquiring data by magnetic reso-nance from a patient.3.1.10 magnetic resonance im
20、aging (MRI)imaging tech-nique that uses static and time varying magnetic fields toprovide images of tissue by the magnetic resonance of nuclei.3.1.11 magnetic resonance system (MR System)ensembleof MR equipment, accessories including means for display,control, energy supplies, and the MR environment
21、.IEC 606012333.1.12 magnetically induced displacement forceforce pro-duced when a magnetic object is exposed to the spatial gradientof a magnetic field. This force will tend to cause the object totranslate in the gradient field.3.1.13 magnetically induced torquetorque produced whena magnetic object
22、is exposed to a magnetic field. This torquewill tend to cause the object to align itself along the magneticfield in an equilibrium direction that induces no torque.3.1.14 magnetization (M in T)magnetic moment per unitvolume.3.1.15 medical deviceany instrument, apparatus, imple-ment, machine, applian
23、ce, implant, in vitro reagent or calilbra-tor, software, material, or other similar or related article,intended by the manufacturer to be used, alone or in combi-nation, for human beings for one or more of the specificpurpose(s) of:(1) diagnosis, prevention, monitoring, treatment, or alleviation of
24、dis-ease,(2) diagnosis, monitoring, treatment, alleviation of, or compensation foran injury,(3) investigation, replacement, modification, or support of the anatomyor of a physiological process,(4) supporting or sustaining life,(5) control of conception,(6) disinfection of medical devices, and(7) pro
25、viding information for medical purposes by means of in vitro ex-amination of specimens derived from the human body, and whichdoes not achieve its primary intended action in or on the humanbody by pharmacological, immunological, or metabolic means, butwhich may be assisted in its function by such mea
26、ns.ISO 134853.1.16 paramagnetic materiala material having a relativepermeability which is slightly greater than unity, and which ispractically independent of the magnetizing force.3.1.17 passive implantan implant that serves its functionwithout the supply of electrical power.3.1.18 tesla, (T)the SI
27、unit of magnetic induction equal to104gauss (G).4. Summary of Test Method4.1 The static field in a magnetic resonance system producesa torque on a device that acts to align the long axis of the objectwith the magnetic field. The torque is evaluated using atorsional pendulum method. A device is place
28、d on a holdersuspended by a torsional spring. The apparatus is placed in thecenter of the magnetic resonance equipment magnet where themagnetic field is uniform. The torque is determined from themeasurement of the deflection angle of the holder from itsequilibrium position. The frame holding the spr
29、ing and holderassembly is rotated and the torque as a function of angle of theimplant is determined. The maximal magnetic torque is com-pared to the worst case gravity torque, defined as the product ofthe maximum linear dimension of the device and the deviceweight.5. Significance and Use5.1 This tes
30、t method is one of those required to determine ifthe presence of a medical device may cause injury during amagnetic resonance examination and in the magnetic reso-nance environment. Other safety issues which should beaddressed include but may not be limited to magneticallyinduced force (see Test Met
31、hod F 2052) and RF heating (seeTest Method F 2182). The terms and icons in Practice F 2503should be used to mark the device for safety in the magneticresonance environment.5.2 If the maximal torque is less than the product of thelongest dimension of the medical device and its weight, thenthe magneti
32、cally induced deflection torque is less than theworst case torque on the device due to gravity. For thiscondition, it is assumed that any risk imposed by the applica-tion of the magnetically induced torque is no greater than anyrisk imposed by normal daily activity in the Earths gravita-tional field
33、. This is conservative; it is possible that greatertorques would not pose a hazard to the patient.5.3 This test method alone is not sufficient for determiningif an implant is safe in the MR environment.5.4 The sensitivity of the torque measurement apparatusmust be greater than110 the “gravity torque
34、,” the product ofdevice weight and the largest linear dimension.5.5 The torque considered here is the magneto-static torquedue to the interaction of the MRI static magnetic field with themagnetization in the implant. The dynamic torque due tointeraction of the static field with eddy currents induced
35、 in arotating device is not addressed in this test method. Currents inlead wires may induce a torque as well.6. Apparatus6.1 The test fixture is depicted in Fig. 1. It consists of asturdy structure supporting a holding platform supported by atorsional spring. Materials should be non-ferromagnetic. T
36、hedevice may be taped or otherwise attached to the holdingplatform. The supporting structure will have fixed to it aF2213062protractor with 1 graduated markings and the holding plat-form will have a marker so that the angle between the basketand the support structure can be measured. The supportings
37、tructure is rotated with the turning knob. The equilibriumangle between the supporting structure and the holding plat-form outside the magnetic field represents the zero torqueangle. The torque inside the magnet is equal to the product ofthe deflection angle and spring constant. The torsional spring
38、NOTEThe angular reference marker is used to locate the angular marks on protractors connected to the bottom mount and the holding platform.FIG. 1 Diagram of the Torque ApparatusNOTEThe turning knob is used to rotate the mounts supporting the torsional pendulum.FIG. 2 Photograph of an Apparatus for M
39、easurement of Magnetic TorqueF2213063diameter should be chosen so that the maximal deflection angleis less than 25. A photograph of a torque apparatus is shownin Fig. 2.7. Test Specimens7.1 For purposes of device qualification, the device evalu-ated according to this test method should be representa
40、tive ofmanufactured devices that have been processed to a finishedcondition (for example, sterilized).7.2 For purposes of device qualification, any alteration fromthe finished condition should be reported. For instance, ifsections are cut from the device for testing, this should bereported.8. Proced
41、ure8.1 Fig. 1 depicts the test fixture, which is placed in themiddle of the magnet where the magnetic field is uniform. Thetest device is placed on the holding platform with one of itsprincipal axes in the vertical direction. The entire apparatus isplaced in the center of the magnet in the region of
42、 uniformmagnetic field. Rotate the fixed base and measure the deflec-tion of the device with respect to the base at 10 increments forangles between 0 and 360. Note that at angular values wherethe angular derivative of the torque changes sign, there will bean abrupt change in deflection angle as the
43、device swings to thenext equilibrium position. Try to measure the deflection angleas close as possible to this swing so that the maximal torquewill be determined.8.2 Repeat the process in 8.1 twice, once for each of theother two principal axes of the device in the vertical direction.8.3 Lead wires s
44、hould be arranged in a manner that isrepresentative of the in vivo configuration. If feasible, the wiresshould carry the currents that are applied in vivo.9. Calculation9.1 The torque is t =kDu where Du is the deflection angleof the basket from its equilibrium position relative to the fixedbase outs
45、ide the magnet and k is the spring constant.10. Report10.1 The report shall include the following for each speci-men tested:10.1.1 Device product description including dimensioneddrawing(s) or a photograph with dimensional scale.10.1.2 A diagram or photograph showing the three configu-rations of the
46、 device during the test.10.1.3 Device product identification (for example, batch, lotnumber, type number, revision, serial number, date of manu-facture).10.1.4 Materials of construction (ASTM designation orother).10.1.5 Number of specimens tested with explanation for thesample size used.10.1.6 Weigh
47、t of the device.10.1.7 Dimensioned diagram or photograph describing thedevice.10.1.8 Description of the type of magnet and the value ofthe static field B0.10.1.9 Cartesian coordinate (x,y,z) location of the center ofmass of the device during the test using a right handedcoordinate system with origin
48、 at isocenter of the magnet.Include a diagram showing the MR system and the coordinateaxes.10.1.10 Diagram or photograph of the test apparatus, in-cluding the value of the spring constant.10.1.11 Plots of torque in units of N-m versus angularposition of a device axis with respect to the direction of
49、 thestatic field. There will three plots in total, one for each principalaxis of the device oriented in the vertical direction.10.1.12 Calculations of torque that would be exerted oncurrent loops in the device (see Appendix X4).10.1.13 Include a description and photograph of alterationsthat were done to the device.11. Precision and Bias11.1 The precision and bias of this test method has not beenestablished.12. Keywords12.1 force, magnetic; implant; metals (for surgical im-plants); MRI (magnetic resonance imaging); MR safety;torque, magneticAPPENDIX
