ISO TS 10974:2012
(Main)Assessment of the safety of magnetic resonance imaging for patients with an active implantable medical device
Assessment of the safety of magnetic resonance imaging for patients with an active implantable medical device
ISO/TS 10974:2012 is applicable to implantable parts of active implantable medical devices (AIMDs) intended to be used in patients who might undergo a magnetic resonance scan in 1,5T, cylindrical bore, whole body MR scanners for imaging the hydrogen nucleus. The tests that are specified in ISO/TS 10974:2012 are type tests intended to be carried out on samples of a device to characterize interactions with the magnetic and electromagnetic fields associated with an MR scanner. ISO/TS 10974:2012 contains test methods that are applicable to a broad class of AIMDs for the purpose of evaluating device operation against several hazards.
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TECHNICAL ISO/TS
SPECIFICATION 10974
First edition
2012-05-01
Assessment of the safety of magnetic
resonance imaging for patients with an
active implantable medical device
Évaluation de la sécurité de l'imagerie par résonance magnétique pour
les patients avec un dispositif médical implantable actif
Reference number
ISO/TS 10974:2012(E)
©
ISO 2012
ISO/TS 10974:2012(E)
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
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Published in Switzerland
ii © ISO 2012 – All rights reserved
ISO/TS 10974:2012(E)
Contents Page
Foreword . vii
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 7
5 General requirements for non-implantable parts . 7
6 Requirements for particular AIMDs . 7
7 Protection of patients from potential hazards caused by interactions of the AIMD and MR
scanners . 8
8 Test signals . 9
8.1 Gradient sequence of sequences . 9
8.2 RF sequence of sequences . 11
9 General considerations for application of the requirements of this Technical Specification . 14
9.1 Compliance criteria . 14
9.2 Monitoring equipment . 14
9.3 Validation of models and test equipment . 14
9.4 Uncertainty assessment . 14
9.5 Test reports . 14
10 Protection from harm to the patient caused by RF-induced heating . 15
10.1 General . 15
10.2 Outline of the four-tier approach . 16
10.2.1 Tier 1 . 16
10.2.2 Tier 2 . 18
10.2.3 Tier 3 . 18
10.2.4 Tier 4 . 19
10.3 Determination of the induced electric and magnetic fields . 20
10.3.1 Electromagnetic simulation . 20
10.3.2 Relevant parameters . 20
10.3.3 Assessment procedure . 20
10.3.4 Uncertainty budget of incident field assessment . 20
10.4 Validation of electromagnetic AIMD models . 21
10.4.1 Validation procedure . 21
10.4.2 Validation criteria . 21
10.5 Generation of incident fields for Tier 1 to Tier 3 and minimal medium requirements . 21
10.6 Measurement system requirements . 22
10.6.1 Probe specification . 22
10.6.2 Validation and characterization of the measurement system . 22
10.7 Procedures and protocols for determination of the distribution and magnitude of the
absorbed energy in the tissue equivalent material by SAR and T measurements . 23
10.7.1 Determination of 3D relative distribution of local energy deposition . 23
10.7.2 Measurement protocol for determination of maximum amplitude . 24
10.8 Uncertainty assessment of energy deposition using SAR or temperature probes . 27
10.9 Compliance criteria . 28
10.10 Test report . 28
ISO/TS 10974:2012(E)
11 Protection from harm to the patient caused by gradient-induced device heating . 28
11.1 General . 28
11.2 Testing considerations. 29
11.2.1 General . 29
11.2.2 Determination of clinical dB/dt exposure limits . 29
11.2.3 Test duration . 30
11.2.4 Data collection . 30
11.3 Test requirements . 31
11.3.1 General . 31
11.3.2 In vitro, phantom or other suitable container . 31
11.3.3 Gelled solution . 31
11.3.4 Optical temperature probes . 31
11.3.5 Temperature survey to determine worst-case orientation and hot spots . 32
11.3.6 Minimum temperature instrumentation . 32
11.3.7 Temperature data collection . 32
11.3.8 Monitor applied dB/dt . 32
11.3.9 Gradient field vector orientation relative to device . 32
11.3.10 Monitoring AIMD for heating and malfunction . 32
11.4 Lab testing using simulated MRI gradient field . 33
11.4.1 Simulated field requirements . 33
11.4.2 Pulse waveform RMS value . 33
11.4.3 Gradient sequence of sequences . 33
11.5 MR scanner testing . 33
11.6 Analysis of gradient heating test . 34
11.7 Uncertainty assessment . 34
11.8 Test report . 34
12 Protection from harm to the patient caused by gradient-induced vibration . 35
12.1 General . 35
12.2 General test considerations . 36
12.2.1 Equipment . 36
12.2.2 Determination of clinical dB/dt and B exposure limits . 39
12.2.3 Test signals . 39
12.3 Test method for the evaluation of AIMD functionality during exposure to gradient-induced
vibration . 39
12.3.1 General requirements . 39
12.3.2 Conducting functional testing using a research scanner . 40
12.3.3 Conducting functional testing using simulated fields . 40
12.3.4 Conducting functional testing using a clinical scanner . 40
12.3.5 Conducting functional testing using a shaker table or other vibration test equipment . 40
12.4 Test method for the evaluation of patient discomfort during exposure to gradient-induced
vibration . 41
12.4.1 General requirements . 41
12.4.2 Conducting patient discomfort testing using a research scanner . 42
12.4.3 Conducting patient discomfort testing using simulated fields. 42
12.4.4 Conducting patient discomfort testing using a clinical scanner . 42
12.4.5 Conducting patient discomfort testing using a shaker table or other vibration test
equipment . 43
12.5 Test method for the evaluation of risk of tissue injury during exposure to gradient-
induced vibration . 43
12.5.1 General requirements . 43
12.5.2 Conducting testing for the evaluation of risk of tissue injury using a research scanner . 46
12.5.3 Conducting testing for the evaluation of risk of tissue injury using simulated fields . 46
12.5.4 Conducting testing for the evaluation of risk of tissue injury using a clinical scanner . 46
12.5.5 Conducting testing for the evaluation of risk of tissue injury using a shaker table or other
vibration test equipment . 46
12.6 Uncertainty assessment . 47
12.7 Test report . 47
13 Protection from harm to the patient caused by B -induced force . 47
iv © ISO 2012 – All rights reserved
ISO/TS 10974:2012(E)
14 Protection from harm to the patient caused by B -induced torque . 47
15 Protection from harm to the patient caused by image artefact . 48
16 Protection from harm to the patient caused by gradient-induced extrinsic electric
potential . 48
16.1 General . 48
16.2 Test procedure . 48
16.3 Uncertainty assessment . 49
16.4 Test report . 49
17 Protection from harm to the patient caused by RF rectification . 49
17.1 General . 49
17.2 Test procedure . 49
17.3 Uncertainty assessment . 50
17.4 Test report . 50
18 Protection from harm to the patient caused by B -induced malfunction . 50
18.1 General . 50
18.2 Test procedure . 50
18.3 Test equipment . 50
18.3.1 Generating the B field . 50
18.3.2 Phantom and tissue simulation medium . 51
18.4 Uncertainty assessment . 51
18.5 Test report . 51
19 Protection from harm to the patient caused by RF-induced malfunction . 51
19.1 Introduction of tiered approach . 51
19.2 Injected immunity test . 53
19.2.1 Using the tiers . 53
19.2.2 Test procedure . 55
19.2.3 Test equipment . 55
19.2.4 Uncertainty assessment . 55
19.2.5 Test report . 55
19.3 Radiated immunity test . 56
19.3.1 Using the tiers . 56
19.3.2 Test procedure . 56
19.3.3 Test equipment . 56
19.3.4 Uncertainty assessment . 57
19.4 Test report . 57
20 Protection from harm to the patient caused by gradient-induced malfunction . 57
20.1 Introduction of tiered approach . 57
20.2 Injected immunity test . 58
20.2.1 Tier 1 . 58
20.2.2 Tier 2 . 62
20.2.3 Tier 3 . 65
20.2.4 Test procedure . 67
20.2.5 Test equipment . 67
20.2.6 Uncertainty assessment . 67
20.2.7 Test report . 67
20.3 Radiated immunity test . 67
20.3.1 Applicability . 67
20.3.2 Tier 1 . 67
20.3.3 Tier 2 . 68
20.3.4 Test procedure . 69
20.3.5 Test equipment . 69
20.3.6 Uncertainty assessment . 69
20.3.7 Test report . 69
21 Combined fields test . 69
22 Markings and accompanying documentation . 70
ISO/TS 10974:2012(E)
Annex A (informative) Gradient vibration patent declaration form . 72
Annex B (informative) Derivation of lead length factor for injected voltage test levels for gradient-
induced malfunction . 74
Annex C (informative) Basic MR physics . 78
Annex D (informative) Gradient injection network . 80
Annex E (informative) RF injection network . 82
Annex F (informative) Estimation of the temperature rise in vivo from determined energy
deposition . 85
Annex G (informative) Methods of assessment of the temperature rise in vivo . 88
Annex H (informative) Assessment of dielectric and thermal parameters . 91
Annex I (normative) Measurement system validation . 94
Annex J (informative) Example of coil systems . 107
Annex K (informative) Current distribution on the AIMD as a function of the phase distribution of
the incident field . 108
Annex L (informative) Recipe and rationale for tissue simulating materials . 111
Annex M (informative) Generation of incident fields . 113
Annex N (informative) Dielectric parameters. 117
Annex O (informative) Thermal and electrical properties of scar tissues . 119
Annex P (informative) Estimation of conservative B and 10g averaged E-field values for Tier 1 for
RF-induced heating and malfunction . 120
Annex Q (informative) AIMD configurations . 126
Annex R (normative) Uncertainty evaluation . 127
Annex S (informative) Guidance on gradient field interactions and test methods for pacemakers. 145
Annex T (informative) Characterization of lead port interface impedance for evaluating gradient-
induced extrinsic electric potential effects . 169
Annex U (informative) Method for in vitro measurement of gradient-induced E-field . 173
Annex V (informative) Basic physics and interactions of gradient magnetic fields with AIMDs . 184
Bibliography . 197
vi © ISO 2012 – All rights reserved
ISO/TS 10974:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
ISO/TS 10974 was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee SC 6,
Active implants.
TS
ISO/TS 10974:2012(E)
Introduction
This Technical Specification came about following a joint meeting between ISO/TC 150, Implants for surgery,
and IEC/SC 62B/MT 40, Magnetic resonance equipment for medical diagnosis, in Vienna, Austria, in
September 2006. An agreement was reached to coordinate efforts on the development of a new Technical
Specification for the safety of patients with active implantable medical devices (AIMD) undergoing an MRI
exam and related further development of IEC 60601-2-33.
This Technical Specification represents a broad-based effort to capture the current understanding of relevant
issues and concerns at 1,5 T, the most common MR field strength. The Joint Working Group (JWG)
responsible for this Technical Specification (ISO TC150/SC6/JWG2 and IEC SC62B/JWG1) recognizes its
incomplete understanding and coverage of relevant details. The JWG releases this edition to promote
developments in this area.
The JWG plans to refine this first edition with the intention of publishing a second edition in the time frame
allowed by the ISO/IEC Directives and seeks input from interested parties. At this time, the JWG anticipates
the possibility that eventually an International Standard might result from this work.
IEC 60601-2-33:2010 provides supporting information. By mutual agreement between the JWG and MT 40,
any and all MR scanner-related requirements will be considered by IEC/SC 62B/MT 40 and will be released
through future amendments and editions of IEC 60601-2-33.
The relationship between product committees is shown in Figure 1. Straight lines represent the relationship
and not necessarily a physical connection. Ellipses represent scope, i.e. the effects between patient and
scanner, patient and AIMD, and AIMD and scanner.
SC6
AIMD Patient
Scanner
Figure 1 — Diagram showing the responsibilities of product committees and illustrating the extent of
the scope of this Technical Specification in terms of the effects between AIMDs and MR scanners
viii © ISO 2012 – All rights reserved
MT40
ISO/TS 10974:2012(E)
This Technical Specification is concerned with interactions on the AIMD caused by the scanner.
ISO/TC 150/SC 6 product committees are concerned with how those interactions affect patient safety.
This Technical Specification is general for all AIMD types, while ISO/TC 150/SC 6 product committees deal
with specific types. ISO/TC 150/SC 6 will turn the general provisions of this Technical Specification into
product-specific requirements, if necessary.
TS
SC6
1 2 3
1. Hazardous situation/mechanism/phenomenon: Interactions between the AIMD and scanner and
resulting phenomenon, e.g. induced voltage.
2. Hazard: Potential source of harm, e.g. heating or malfunction. A knowledge of known or foreseeable
hazards resulting from physical interactions will guide comprehension, selection and development of TS
test methods.
3. Risk: Probability of occurrence of harm x severity of harm.
Figure 2 — Responsibilities of product committees illustrating the extent of the scope of this
Technical Specification in terms of the delineation between hazards and harms
Test methods described in this Technical Specification are primarily designed and intended as bench-top tests
using equipment and techniques to simulate the fields (B static, gradient, and RF) found in MR 1,5 T
scanners. Although, in a few cases, clinical scanner tests are implied, in all others, the AIMD manufacturer
assumes the burden for development and validation of clinical scanner-based test methods. Furthermore, the
test signals and parameters specifically described within this Technical Specification for bench-top testing (e.g.
Clause 8) are not being encouraged or recommended for use on clinical scanners and to do so might result in
scanner damage.
No requirements contained within this Technical Specification, including the use of clinical scanners, construe
or imply any burden or obligation on the part of MR equipment manufacturers. Any statement to the contrary is
strictly unintentional.
The requirements contained within this Technical Specification are based on specific potential hazards that
have been identified as applicable to a general class of AIMDs (see Clause 7). Risks associated with these
specific hazards, and any additional hazards and risks that might occur for any specific AIMD type
(e.g. implantable neurostimulators), are outside the scope of this Technical Specification.
NOTE 1 Other interested parties, such as device manufacturers, regulatory agencies and particular product
committees, are responsible for setting specific compliance criteria and determining risk.
NOTE 2 The discussion of risk and, in some cases, test methods in some of the informative annexes (e.g. Annex S,
Annex T and Annex V) serves to provide additional information and a rationale that might assist readers in their
comprehension of this material. The information provided in these annexes is supplementary and subordinate to the
normative requirements in this Technical Specification.
ISO/TS 10974:2012(E)
The International Organization for Standardization (ISO) and the International Electrotechnical Commission
(IEC) draw attention to the fact that it is claimed that compliance with this Technical Specification may involve
the use of a patent concerning gradient vibration given in Clause 12.
ISO and IEC take no position concerning the evidence, validity and scope of this patent right.
The hol der of this patent right has assured ISO and IEC that he or she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statement of the holder of this patent right is registered with ISO and IEC (a copy of the patent declaration
is shown in Annex A). Further information may be obtained from:
Medtronic, Inc.
Open Innovation and Intellectual Property
8200 Coral Sea St. NE, MVN43
Mounds View, MN 55112
USA
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified above. ISO and IEC shall not be held responsible for identifying any or all
such patent rights.
x © ISO 2012 – All rights reserved
TECHNICAL SPECIFICATION ISO/TS 10974:2012(E)
Assessment of the safety of magnetic resonance imaging for
patients with an active implantable medical device
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
This Technical Specification is applicable to implantable parts of active implantable medical devices (AIMDs)
intended to be used in patients who undergo a magnetic resonance scan in 1,5 T, cylindrical bore, whole body
MR scanners for imaging the hydrogen nucleus.
NOTE 1 Requirements for non-implantable parts are outside the scope of this Technical Specification.
The tests that are specified in this Technical Specification are type tests intended to be carried out on samples
of a device to characterize interactions with the magnetic and electromagnetic fields associated with an MR
scanner. They can be used to demonstrate device operation according to its MR Conditional labelling. The
tests are not intended to be used for the routine testing of manufactured products.
This Technical Specification contains test methods that are applicable to a broad class of AIMDs for the
purpose of evaluating device operation against several hazards (see Clause 7). Tests for particular device
types are not included. Specific compliance criteria and the determination of risk resulting from device
behavioural response during these tests are outside the scope of this Technical Specification.
NOTE 2 Modification of these tests for particular device types is left to particular product committees.
NOTE 3 Other interested parties, such as device manufacturers, regulatory agencies, and particular product
committees, are responsible for setting specific compliance criteria and determining risk.
NOTE 4 All safety requirements for MRI scanners can be found in IEC 60601-2-33.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
IEC 60601-2-33:2010, Medical electrical equipment — Part 2-33: Particular requirements for the basic safety
and essential performance of magnetic resonance equipment for medical diagnosis
IEC 61000-4-3, Electromagnetic compatibility (EMC) — Part 4-3: Testing and measurement techniques —
Radiated, radio-frequency, electromagnetic field immunity test
ANSI/AAMI PC69:2007, Active implantable medical devices — Electromagnetic compatibility — EMC test
protocols for implantable cardiac pacemakers and implantable cardioverter defibrillators
ASTM F2052, Standard Test Method for Measurement of Magnetically Induced Displacement Force on
Medical Devices in the Magnetic Resonance Environment
ISO/TS 10974:2012(E)
ASTM F2213, Standard Test Method for Measurement of Magnetically Induced Torque on Medical Devices in
the Magnetic Resonance Environment
ASTM F2503-08, Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic
Resonance Environment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
AIMD
active implantable medical device
active medical device which is intended to be totally or partially introduced, surgically or medically, into the
human body or by medical intervention into a natural orifice, and which is intended to remain after the
procedure
[ISO 13485:2003, definition 3.1]
NOTE For the purposes of this Technical Specification, an AIMD is a system consisting of a set of components
(e.g. device and leads) and accessories which interact to achieve the performance intended by the manufacturer.
3.2
AIMD configuration
any unique combination or arrangement of AIMD system settings or components, particularly relative
geometrical orientations or electrical connections between components (see Annex Q)
3.3
active medical device
medical device relying for its functioning on a source of electrical energy or any source of power other than
that directly generated by the human body or gravity
[ISO 13485:2003, definition 3.2]
3.4
B
static magnetic field of the MR scanner, taken as 1,5 T in this Technical Specification, unless otherwise stated
3.5
B
1RMS
root mean square (RMS) of B , the radio frequency magnetic induction
t
x
[(Bt)] dt
B
1RMS
t
x
where t is time, and t is the evaluation time, estimated at the RF transmit coil centre
x
[IEC 60601-2-33:2010, definition 201.3.201]
3.6
birdcage coil
radiator which generates the RF portion of the magnetic field
NOTE This usually refers to a bench-top coil used to simulate the operation of a scanner's volume RF transmit coil.
2 © ISO 2012 – All rights reserved
ISO/TS 10974:2012(E)
3.7
compliance volume
patient-accessible space in which compliance of gradient output is inspected
NOTE 1 In MR equipment with a cylindrical whole body magnet, the compliance volume is a cylinder whose axis
coincides with the magnet axis, with a radius of 0,20 m and with a length equal to the gradient coil.
NOTE 2 Adapted from IEC 60601-2-33, definition 201.3.202.
3.8
cylindrical bore scanner reference coordinate system
three dimensional Cartesian coordinate system in which the X axis lies in a horizontal plane, the Y axis in a
vertical plane, the Z axis is coaxial with the magnet bore, and the origin of the reference coordinate system is
located at isocentre
3.9
device
that part of an AIMD that houses a power source and electronic circuit and which produces a stimulation
voltage or current pulse
NOTE The complete AIMD includes the device and a means for conveying the output pulse to the stimulation site.
3.10
effective stimulus duration
t
s,eff
duration of any period of the monotonic increasing or decreasing gradient, used to describe its limits for
cardiac or peripheral nerve stimulation, defined as the ratio of the peak-to-peak field variation and the
maximum value of the time derivative of the gradient in that period
[IEC 60601-2-33:2010, definition 201.3.205]
3.11
extrinsic electric potential
unrectified voltage induced by fields external to the AIMD (i.e. not caused by the device)
3.12
first level controlled operating mode
mode of operation of the MR equipment in which one or more outputs reach a value that can cause
physiological stress to patients which needs to be controlled by medical supervision
NOTE Definition and validation of physiological stress is defined in the absence of additional sources that may cause
or enhance stress factors (like AIMDs).
[IEC 60601-2-33:2010, definition 201.3.208]
3.13
G
magnetic field gradient in units of T/m
NOTE 1 G introduces a spatial gradient along the X axis of the reference coordinate system, G introduces a gradient
x y
along the Y axis, and G introduces a gradient along the Z axis.
z
NOTE 2 Adapted from IEC 60601-2-33:2010, Table 201.101.
3.14
gradient output
parameter characterizing the gradient performance, such as rate of change of the magnitude of the magnetic
field, or E-field induced by one or more gradient units, under specified conditions and at a specified position
[IEC 60601-2-33:201
...
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