ASTM F2213-06(2011)
(Test Method)Standard Test Method for Measurement of Magnetically Induced Torque on Medical Devices in the Magnetic Resonance Environment
Standard Test Method for Measurement of Magnetically Induced Torque on Medical Devices in the Magnetic Resonance Environment
SIGNIFICANCE AND USE
This test method is one of those required to determine if the presence of a medical device may cause injury during a magnetic resonance examination and in the magnetic resonance environment. Other safety issues which should be addressed include but may not be limited to magnetically induced force (see Test Method F2052) and RF heating (see Test Method F2182). The terms and icons in Practice F2503 should be used to mark the device for safety in the magnetic resonance environment.
If the maximal torque is less than the product of the longest dimension of the medical device and its weight, then the magnetically induced deflection torque is less than the worst case torque on the device due to gravity. For this condition, it is assumed that any risk imposed by the application of the magnetically induced torque is no greater than any risk imposed by normal daily activity in the Earth's gravitational field. This is conservative; it is possible that greater torques would not pose a hazard to the patient.
This test method alone is not sufficient for determining if an implant is safe in the MR environment.
The sensitivity of the torque measurement apparatus must be greater than 1/10 the “gravity torque,” the product of device weight and the largest linear dimension.
The torque considered here is the magneto-static torque due to the interaction of the MRI static magnetic field with the magnetization in the implant. The dynamic torque due to interaction of the static field with eddy currents induced in a rotating device is not addressed in this test method. Currents in lead wires may induce a torque as well.
SCOPE
1.1 This test method covers the measurement of the magnetically induced torque produced by the static magnetic field in the magnetic resonance environment on medical devices and the comparison of that torque to the equivalent torque applied by the gravitational force to the implant.
1.2 This test method does not address other possible safety issues which include but are not limited to issues of magnetically induced force due to spatial gradients in the static magnetic field, RF heating, induced heating, acoustic noise, interaction among devices, and the functionality of the device and the MR system.
1.3 The torque considered here is the magneto-static torque due to the interaction of the MRI static magnetic field with the magnetization in the implant. The dynamic torque due to interaction of the static field with eddy currents induced in a rotating device is not addressed in this test method. Currents in lead wires may induce a torque as well.
1.4 The sensitivity of the torque measurement apparatus must be greater than 1/10 the “gravity torque,” the product of the device's maximum linear dimension and its weight.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
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Designation: F2213 − 06 (Reapproved 2011)
Standard Test Method for
Measurement of Magnetically Induced Torque on Medical
Devices in the Magnetic Resonance Environment
This standard is issued under the fixed designation F2213; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers the measurement of the mag- 2.1 ASTM Standards:
netically induced torque produced by the static magnetic field F2052Test Method for Measurement of Magnetically In-
inthemagneticresonanceenvironmentonmedicaldevicesand duced Displacement Force on Medical Devices in the
the comparison of that torque to the equivalent torque applied Magnetic Resonance Environment
by the gravitational force to the implant. F2119Test Method for Evaluation of MR Image Artifacts
from Passive Implants
1.2 This test method does not address other possible safety
F2182Test Method for Measurement of Radio Frequency
issues which include but are not limited to issues of magneti-
Induced Heating On or Near Passive Implants During
cally induced force due to spatial gradients in the static
Magnetic Resonance Imaging
magnetic field, RF heating, induced heating, acoustic noise,
F2503Practice for Marking Medical Devices and Other
interaction among devices, and the functionality of the device
Items for Safety in the Magnetic Resonance Environment
and the MR system.
2.2 Other Standards:
1.3 The torque considered here is the magneto-static torque
IEC 60601-2-33Ed. 2.0 Medical Electrical Equipment—
due to the interaction of the MRI static magnetic field with the
Part2:ParticularRequirementsfortheSafetyofMagnetic
magnetization in the implant. The dynamic torque due to
Resonance Equipment for Medical Diagnosis, 2002
interaction of the static field with eddy currents induced in a
ISO 13485:2003(E) Medical Devices—Quality Manage-
rotatingdeviceisnotaddressedinthistestmethod.Currentsin
ment Systems—Requirements for Regulatory Purposes,
lead wires may induce a torque as well.
definition 3.7
1.4 The sensitivity of the torque measurement apparatus
3. Terminology
mustbegreaterthan ⁄10the“gravitytorque,”theproductofthe
3.1 Definitions—For the purposes of this test method, the
device’s maximum linear dimension and its weight.
definitions in 3.1.1 – 3.1.18 shall apply:
1.5 The values stated in SI units are to be regarded as
3.1.1 diamagnetic material—a material whose relative per-
standard. No other units of measurement are included in this
meability is less than unity.
standard.
3.1.2 ferromagnetic material—a material whose magnetic
1.6 This standard does not purport to address all of the
moments are ordered and parallel producing magnetization in
safety concerns, if any, associated with its use. It is the
one direction.
responsibility of the user of this standard to establish appro-
3.1.3 magnetic induction or magnetic flux density (B in
priate safety and health practices and determine the applica-
T)—that magnetic vector quantity which at any point in a
bility of regulatory limitations prior to use.
magnetic field is measured either by the mechanical force
1 2
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical For referenced ASTM standards, visit the ASTM website, www.astm.org, or
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
F04.15 on Material Test Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2011. Published October 2011. Originally the ASTM website.
approved in 2002. Last previous edition approved in 2006 as F2213–06. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/F2213-06R11. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2213 − 06 (2011)
experiencedbyanelementofelectriccurrentatthepoint,orby article, intended by the manufacturer to be used, alone or in
the electromotive force induced in an elementary loop during combination, for human beings for one or more of the specific
any change in flux linkages with the loop at the point. The purpose(s) of:
magnetic induction is frequently referred to as the magnetic
(1) diagnosis, prevention, monitoring, treatment, or allevia-
tion of disease,
field. B isthestaticfieldinanMRsystem.Plaintypeindicates
(2) diagnosis, monitoring, treatment, alleviation of, or com-
a scalar (for example, B) and bold type indicates a vector (for
pensation for an injury,
example,B).
(3) investigation, replacement, modification, or support of the
anatomy or of a physiological process,
3.1.4 magnetic field strength (H in A/m)—strength of the
(4) supporting or sustaining life,
(5) control of conception,
applied magnetic field.
(6) disinfection of medical devices, and
3.1.5 magnetic resonance (MR)—resonant absorption of (7) providing information for medical purposes by means of
in vitro examination of specimens derived from the hu-
electromagnetic energy by an ensemble of atomic particle
man body, and which does not achieve its primary in-
situated in a magnetic field.
tended action in or on the human body by
pharmacological, immunological, or metabolic means,
3.1.6 magnetic resonance diagnostic device—a device in-
but which may be assisted in its function by such means.
tended for general diagnostic use to present images which
ISO 13485
reflectthespatialdistributionormagneticresonancespectra,or
3.1.16 paramagnetic material—a material having a relative
both, which reflect frequency and distribution of nuclei exhib-
permeability which is slightly greater than unity, and which is
iting nuclear magnetic resonance. Other physical parameters
practically independent of the magnetizing force.
derived from the images or spectra, or both, may also be
3.1.17 passive implant—an implant that serves its function
produced.
without the supply of electrical power.
3.1.7 magnetic resonance (MR) environment—volume
3.1.18 tesla, (T)—the SI unit of magnetic induction equal to
within the 0.50 mT(5 gauss (G)) line of an MR system, which 4
10 gauss (G).
includes the entire three dimensional volume of space sur-
4. Summary of Test Method
rounding the MR scanner. For cases where the 0.50 mT line is
contained within the Faraday shielded volume, the entire room
4.1 Thestaticfieldinamagneticresonancesystemproduces
shall be considered the MR environment.
atorqueonadevicethatactstoalignthelongaxisoftheobject
with the magnetic field. The torque is evaluated using a
3.1.8 magnetic resonance equipment—medical electrical
torsional pendulum method. A device is placed on a holder
equipment which is intended for in-vivo magnetic resonance
suspended by a torsional spring.The apparatus is placed in the
examination of a patient. The MR equipment comprises all
center of the magnetic resonance equipment magnet where the
parts in hardware and software from the supply mains to the
magnetic field is uniform. The torque is determined from the
display monitor. The MR equipment is a Programmable
measurement of the deflection angle of the holder from its
Electrical Medical System (PEMS).
equilibrium position. The frame holding the spring and holder
3.1.9 magnetic resonance examination (MR Examination)—
assembly is rotated and the torque as a function of angle of the
process of acquiring data by magnetic resonance from a
implant is determined. The maximal magnetic torque is com-
patient.
paredtotheworstcasegravitytorque,definedastheproductof
the maximum linear dimension of the device and the device
3.1.10 magnetic resonance imaging (MRI)—imaging tech-
nique that uses static and time varying magnetic fields to weight.
provide images of tissue by the magnetic resonance of nuclei.
5. Significance and Use
3.1.11 magnetic resonance system (MR System)—ensemble
5.1 Thistestmethodisoneofthoserequiredtodetermineif
of MR equipment, accessories including means for display,
the presence of a medical device may cause injury during a
control, energy supplies, and the MR environment.
magnetic resonance examination and in the magnetic reso-
IEC 60601–2–33
nance environment. Other safety issues which should be
3.1.12 magnetically induced displacement force—forcepro- addressed include but may not be limited to magnetically
induced force (see Test Method F2052) and RF heating (see
ducedwhenamagneticobjectisexposedtothespatialgradient
of a magnetic field. This force will tend to cause the object to Test Method F2182). The terms and icons in Practice F2503
should be used to mark the device for safety in the magnetic
translate in the gradient field.
resonance environment.
3.1.13 magnetically induced torque—torqueproducedwhen
5.2 If the maximal torque is less than the product of the
a magnetic object is exposed to a magnetic field. This torque
longest dimension of the medical device and its weight, then
will tend to cause the object to align itself along the magnetic
the magnetically induced deflection torque is less than the
field in an equilibrium direction that induces no torque.
worst case torque on the device due to gravity. For this
3.1.14 magnetization (M in T)—magnetic moment per unit
condition, it is assumed that any risk imposed by the applica-
volume.
tion of the magnetically induced torque is no greater than any
3.1.15 medical device—any instrument, apparatus, risk imposed by normal daily activity in the Earth’s gravita-
implement, machine, appliance, implant, in vitro reagent or tional field. This is conservative; it is possible that greater
calilbrator, software, material, or other similar or related torques would not pose a hazard to the patient.
F2213 − 06 (2011)
5.3 This test method alone is not sufficient for determining manufactured devices that have been processed to a finished
if an implant is safe in the MR environment. condition (for example, sterilized).
5.4 The sensitivity of the torque measurement apparatus
7.2 Forpurposesofdevicequalification,anyalterationfrom
must be greater than ⁄10 the “gravity torque,” the product of
the finished condition should be reported. For instance, if
device weight and the largest linear dimension.
sections are cut from the device for testing, this should be
reported.
5.5 The torque considered here is the magneto-static torque
due to the interaction of the MRI static magnetic field with the
8. Procedure
magnetization in the implant. The dynamic torque due to
interaction of the static field with eddy currents induced in a
8.1 Fig. 1 depicts the test fixture, which is placed in the
rotatingdeviceisnotaddressedinthistestmethod.Currentsin
middle of the magnet where the magnetic field is uniform.The
lead wires may induce a torque as well.
test device is placed on the holding platform with one of its
principal axes in the vertical direction. The entire apparatus is
6. Apparatus
placed in the center of the magnet in the region of uniform
6.1 The test fixture is depicted in Fig. 1. It consists of a
magnetic field. Rotate the fixed base and measure the deflec-
sturdy structure supporting a holding platform supported by a
tionofthedevicewithrespecttothebaseat10°incrementsfor
torsional spring. Materials should be non-ferromagnetic. The
angles between 0° and 360°. Note that at angular values where
device may be taped or otherwise attached to the holding
the angular derivative of the torque changes sign, there will be
platform. The supporting structure will have fixed to it a
anabruptchangeindeflectionangleasthedeviceswingstothe
protractor with 1° graduated markings and the holding plat-
next equilibrium position. Try to measure the deflection angle
form will have a marker so that the angle between the basket
as close as possible to this swing so that the maximal torque
and the support structure can be measured. The supporting
will be determined.
structure is rotated with the turning knob. The equilibrium
angle between the supporting structure and the holding plat- 8.2 Repeat the process in 8.1 twice, once for each of the
other two principal axes of the device in the vertical direction.
form outside the magnetic field represents the zero torque
angle. The torque inside the magnet is equal to the product of
8.3 Lead wires should be arranged in a manner that is
the deflection angle and spring constant. The torsional spring
representativeofthe in vivoconfiguration.Iffeasible,thewires
diametershouldbechosensothatthemaximaldeflectionangle
should carry the currents that are applied in vivo.
is less than 25°. A photograph of a torque apparatus is shown
in Fig. 2.
9. Calculation
7. Test Specimens
9.1 The torque is τ=k∆θ where ∆θ is the deflection angle
7.1 For purposes of device qualification, the device evalu- of the basket from its equilibrium position relative to the fixed
ated according to this test method should be representative of base outside the magnet and k is the spring constant.
NOTE 1—The 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 Apparatus
F2213 − 06 (2011)
NOTE 1—The turning knob is used to rotate the mounts supporting the torsional pendulum.
FIG. 2 Photograph of an Apparatus for Measurement of Magnetic Torque
10. Report coordinate system with origin at isocenter of the magnet.
Include a diagram showing the MR system and the coordinate
10.1 The report shall include the following for each speci-
axes.
men tested:
10.1.10 Diagram or photograph of the test apparatus, in-
10.1.1 Device product description including dimensioned
cluding the value of the spring constant.
drawing(s) or a photograph with dimensional scale.
10.1.11 Plots of torque in units of N-m versus angular
10.1.2 Adiagram or photograph showing the three configu-
position of a device axis with respect to the direction of the
rations of the device during the test.
staticfield.Therewillthreeplotsintotal,oneforeachprincipal
10.1.3 Deviceproductidentification(forexample,batch,lot
axis of the device oriented in the vertical direction.
number, type number, revision, serial number, date of manu-
10.1.12 Calculations of torque that would be exerted on
facture).
current loops in the device (see Appendix X4).
10.1.4 Materials of construction (ASTM designation or
10.1.13 Include a description and photograph of alterations
other).
that were done to the device.
10.1.5 Numberofspecime
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