ISO TS 10974:2018
(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 10974:2018 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 (circular or elliptical cross-section) bore, whole body MR scanners operating at approximately 64 MHz with whole body coil excitation.
NOTE 1 Requirements for non-implantable parts are outside the scope of this document.
The tests that are specified in this document are type tests that characterize interactions with the magnetic and electromagnetic fields associated with an MR scanner. The tests 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.
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 Safety requirements for MR scanners can be found in IEC 60601‑2‑33.
NOTE 5 The scope is limited to AIMDs that do not use sensing functions or to AIMDs that are programmed not to use sensing functions to affect therapy delivery during an MR scan.
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Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 10974
Second edition
2018-04
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 10974:2018(E)
©
ISO 2018
ISO/TS 10974:2018(E)
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved
ISO/TS 10974:2018(E)
Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 6
5 General requirements for non-implantable parts . 6
6 Requirements for particular AIMDs . 6
7 General considerations for application of the tests of this document .6
7.1 Compliance criteria . 6
7.2 Use of tiers . 7
7.3 Test reports . 7
7.3.1 General. 7
7.3.2 Description of the AIMD under test . 7
7.3.3 Test methods and results . 7
8 Protection from harm to the patient caused by RF-induced heating .8
8.1 Introduction . 8
8.2 Outline of the Stage 1 four-tier approach . 8
8.3 Measurement system prerequisites for all tiers .10
8.3.1 RF field source .10
8.3.2 Tissue simulating phantom .10
8.3.3 Definition of power deposition .12
8.3.4 Measurement system validation .12
8.4 Determination of RF-induced power deposition in a tissue simulating medium .12
8.4.1 General.12
8.4.2 Determine location of hot spots around the AIMD .13
8.4.3 Determination of spatial (3D) distribution of power deposition for each
hot spot .13
8.4.4 Determine the final power deposition .14
8.5 Proximity effect of electrodes from multiple leads .16
8.6 Modelling prerequisites for Tier 2, Tier 3, and Tier 4 .17
8.7 Tier selection for RF-induced power deposition .17
8.7.1 General.17
8.7.2 Tier 1 .17
8.7.3 Tier 2 .18
8.7.4 Tier 3 .19
8.7.5 Tier 4 .20
8.8 In vitro model validation .21
8.9 Overall uncertainty analysis .23
8.10 In vivo analysis of power deposition .24
8.11 RF-induced heating assessment flow chart.24
9 Protection from harm to the patient caused by gradient-induced device heating .27
9.1 Introduction .27
9.2 Testing considerations .28
9.2.1 General.28
9.2.2 Determination of |dB/dt| rms exposure limits .29
9.2.3 Determination of test duration .29
9.3 Test requirements .29
9.3.1 General.29
9.3.2 In vitro test phantom or other suitable container .30
9.3.3 Gelled solution .30
ISO/TS 10974:2018(E)
9.3.4 Temperature survey to determine orientation and hot spots .30
9.3.5 Minimum temperature instrumentation .31
9.3.6 Definition of dB/dt test waveform .31
9.3.7 Characterization of applied dB/dt .32
9.4 Lab testing using simulated MR gradient field .32
9.5 MR scanner testing .32
9.6 Analysis of gradient heating test .33
10 Protection from harm to the patient caused by gradient-induced vibration .33
10.1 Introduction .33
10.2 Overview of tiers .34
10.3 MR environmental conditions .35
10.3.1 General.35
10.3.2 Determination of maximum clinical dB/dt .35
10.3.3 Determination of clinical B .
0 35
10.3.4 Determination of clinical dB/dt × B .
0 35
10.3.5 Test frequencies .35
10.3.6 Test duration .36
10.3.7 Test temperature .37
10.4 General test procedure .37
10.4.1 Measurement of gradient field and determination of AIMD location .37
10.4.2 AIMD/test unit setup .37
10.5 Method 1 — MR scanner .38
10.6 Method 2 — Shaker table .39
10.6.1 General.39
10.6.2 Determine scanner input .39
10.6.3 AIMD vibration response .39
10.6.4 Determine shaker table amplitude (dB/dt scaling) .40
10.6.5 Perform vibration exposure using a shaker table .40
11 Protection from harm to the patient caused by B -induced force .41
12 Protection from harm to the patient caused by B -induced torque .41
13 Protection from harm to the patient caused by gradient-induced extrinsic electric
potential .41
13.1 Introduction .41
13.2 General requirements .42
13.3 Gradient pulse leakage test .46
13.3.1 General.46
13.3.2 Test equipment .46
13.3.3 Test signal .46
13.3.4 Tier 1 — Combined gradient-induced charge measurement test procedure .48
13.3.5 Tier 2 — Separate transient gradient-induced charge and steady-state
current measurement test procedure .51
13.4 Gradient rectification test .53
13.4.1 General.53
13.4.2 Test equipment .53
13.4.3 Test signal .53
13.4.4 Gradient-induced rectification measurement test procedure .54
13.5 Gradient pulse distortion of AIMD output test .56
13.5.1 General.56
13.5.2 Test equipment .56
13.5.3 Test signal .56
13.5.4 Gradient-induced AIMD output distortion test procedure .56
14 Protection from harm to the patient caused by B -induced malfunction .58
14.1 Introduction .58
14.2 Static field testing .59
14.2.1 B general requirements for static field testing .59
14.2.2 B field generation .60
iv © ISO 2018 – All rights reserved
ISO/TS 10974:2018(E)
14.2.3 Test conditions.60
14.3 Test procedures .60
14.3.1 General.60
14.3.2 Class 0 test procedure .60
14.3.3 Class 1 test procedure .60
14.3.4 Class 2 test procedure .61
15 Protection from harm to the patient caused by RF-induced malfunction and RF
rectification .61
15.1 Introduction .61
15.2 General requirements .61
15.3 Mechanisms for RF interaction with an AIMD .61
15.4 Selecting radiated vs injected test methods .63
15.4.1 General.63
15.4.2 AIMD type designation for test method selection .63
15.4.3 RF antenna type designation for test method selection .65
15.4.4 RF EMC tier selection .65
15.4.5 RF test conditions .65
15.4.6 B considerations .68
15.5 Injected immunity test .68
15.5.1 General.68
15.5.2 Determination of peak and rms injected levels for Tier 1 and Tier
2 — AIMD with short electrical length .69
15.5.3 Determination of peak and rms injected levels for Tier 3 and Tier 4 .69
15.5.4 Injected immunity test procedure .71
15.5.5 RF phase test conditions .71
15.5.6 AIMD monitoring during the test .72
15.6 Radiated immunity test .72
15.6.1 General.72
15.6.2 Determining the RF radiated field level .72
15.6.3 Radiated test procedure .72
15.6.4 AIMD monitoring during the test .73
15.7 Test equipment .73
15.7.1 Generating the RF electric field for radiated testing (AIMD with short
electrical length) .73
15.7.2 Phantom and tissue simulating medium for radiated testing .73
15.7.3 AIMD monitoring apparatus .73
15.7.4 RF level measuring device .74
15.7.5 RF injection network .74
15.8 Determining the peak RF injected level using a radiated test .75
16 Protection from harm to the patient caused by gradient-induced malfunction .76
16.1 Introduction .76
16.2 General requirements .76
16.3 Selecting radiated and injected test methods .77
16.4 Radiated immunity test .78
16.4.1 General.78
16.4.2 Test equipment .78
16.4.3 Radiated test signal .79
16.4.4 Test procedure .81
16.5 Injected immunity test .82
16.5.1 General.82
16.5.2 Test equipment .82
16.5.3 Injected test signal.82
16.5.4 Test procedure .84
16.5.5 AIMD test configuration .86
17 Combined fields test .93
17.1 Introduction .93
17.2 Test setup .94
ISO/TS 10974:2018(E)
17.3 AIMD fixation .96
17.4 Test procedure .97
17.4.1 General.97
17.4.2 Before MR exposure .97
17.4.3 During MR exposure .97
17.4.4 After MR exposure .97
17.5 Test equipment .97
17.5.1 Field generation .97
17.5.2 Phantom and tissue simulating medium .97
17.5.3 AIMD monitoring apparatus .98
18 Markings and accompanying documentation .98
18.1 Definitions .98
18.2 Applicability of labelling requirements .98
18.3 Labelling requirements .98
Annex A (normative) Pulsed gradient exposure for Clause 10, Clause 13, and Clause 16 .100
Annex B (informative) Derivation of lead length factor for injected voltage test levels for
Clause 13 and Clause 16 .112
Annex C (informative) Tier 1 high tangential E-field trough line resonator .121
Annex D (informative) Supporting information and rationale for gradient-induced device
heating .128
Annex E (informative) Example RF injection network .133
Annex F (informative) Supporting information and rationale for MR-induced vibration .135
Annex G (informative) Gradient vibration patent declaration form .139
Annex H (informative) Assessment of dielectric and thermal parameters .141
Annex I (informative) RF exposure system validation method.146
Annex J (informative) MR scanner RF transmit coil .156
Annex K (informative) Current distribution on the AIMD as a function of the phase
distribution of the incident field.158
Annex L (informative) Tissue simulating medium formulations .161
Annex M (informative) Generation of incident fields.165
Annex N (informative) Dielectric and thermal tissue properties .180
Annex O (informative) Gradient field injected testing — AIMD electrode tissue impedance
determination method .184
Annex P (informative) Estimation of conservative B and 10 g averaged E-field values for
Tier 1 for RF-induced heating and RF malfunction .189
Annex Q (informative) AIMD configuration .197
Annex R (informative) Electrically excitable tissue stimulation, terms and definitions .198
Annex S (informative) Combined fields test .200
Annex T (informative) General methods for modelling dB/dt levels in MR gradient coils .206
Bibliography .212
vi © ISO 2018 – All rights reserved
ISO/TS 10974:2018(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared jointly by Technical Committee ISO/TC 150, Implants for surgery,
Subcommittee SC 6, Active implants, and Technical Committee IEC TC 62, Electrical equipment in medical
practice, Subcommittee SC 62B, Diagnostic imaging equipment. The draft was circulated for voting to the
national bodies of both ISO and IEC.
This second edition cancels and replaces the first edition (ISO/TS 10974:2012) which has been
technically revised.
ISO/TS 10974:2018(E)
Introduction
The first edition (2012) of this document 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 second edition represents experience gained from the first edition of its use in practice and 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 document (ISO/TC 150/SC 6/JWG 2 and IEC/
SC 62B/JWG 1) releases this edition to promote further developments in this area. The JWG anticipates
the possibility that an International Standard might result from this work.
IEC 60601-2-33 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.
No requirements contained within this document, including the use of clinical scanners, construe or
imply any obligation for compliance on the part of MR scanner manufacturers. Any statement to the
contrary is strictly unintentional.
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.
The JWG is concerned with effects on the AIMD caused by the scanner. ISO/TC 150/SC 6 is concerned
with resulting potential hazards to the patient caused by the AIMD. IEC 62B/MT40 is concerned with
potential hazards to the patient caused by the MR scanner.
Figure 1 — Responsibilities of product committees illustrating the extent of the scope of this
document in terms of the effects between AIMDs and MR scanners
The test methods contained in this document for evaluating device operation against several hazards
are applicable to a broad class of AIMDs. Tests for particular device types are not included. Specific
viii © ISO 2018 – All rights reserved
ISO/TS 10974:2018(E)
compliance criteria and the determination of risk resulting from device behavioural responses during
these tests are outside the scope of this document.
NOTE The device manufacturer, regulatory agencies and particular product committees, are responsible for
setting specific compliance criteria and the determination of risk. For example, ISO/TC 150/SC 6 might turn the
general provisions of this document into product-specific requirements.
The test methods in this document were derived from six known or foreseeable potential hazards to
patients with an AIMD undergoing an MR scan. These general hazards give rise to specific test methods
as shown in Table 1.
Table 1 — Potential patient hazards and corresponding test methods
General hazard Test method Clause
Heat RF field-induced heating of the AIMD 8
Gradient field-induced device heating 9
Vibration Gradient field-induced vibration 10
Force B -induced force 11
Torque B -induced torque 12
Gradient field-induced lead voltage
(extrinsic electric potential)
Unintended stimulation
RF field-induced rectified lead voltage 15
Malfunction B field-induced device malfunction 14
RF field-induced device malfunction 15
Gradient field-induced device malfunction 16
Combined fields test 17
Figure 2 depicts the relationship between the three output fields of an MR scanner (RF, gradient,
and B ) and the hazards considered by this document. In the figure, extrinsic electric potential and
RF rectification are represented as Unintended Stimulation and heat is shown as occurring from two
sources, Electrode Heating and Device Heating. Numbers in parentheses indicate clause numbers. For
example, RF field-induced heating of electrodes is evaluated according to the test method in Clause 8.
ISO/TS 10974:2018(E)
Figure 2 — Relationship between MR scanner output fields (RF, gradient, B) and hazards (test
method clause numbers in parentheses)
Evaluation of the AIMD for these hazards involves some combination of testing and modelling. Tests
in Clauses 8 through 16 may use bench-top testing, modelling, MR scanners, or a combination of these
approaches. The test in Clause 17 uses an MR scanner. Devices are subjected to radiated fields or
injected voltages in order to witness behavioural responses. Modelling may be employed to determine
appropriate test signal voltage levels or to estimate tissue heating, for example. Within this document
device immunity to the B , RF, and gradient fields is evaluated separately, except for Clause 17.
In addition to the tests listed in Table 1, this document contains requirements for markings and
accompanying documentation (Clause 18).
RF-induced heating of tissues surrounding an AIMD is caused by elevated local SAR and associated
component heating that arises from induced currents.
Gradient-induced device heating is caused by eddy currents.
Device vibration is due to the combined effect of the B (static) and gradient fields.
Force and torque is caused by B (static) interaction with magnetic materials.
Extrinsic electric potential is meant to imply that the induced voltage comes from outside the device as
in the case of gradient-induced stimulation or modification of output pulses due to superposition. The
result involves voltages not caused by a device malfunction.
Rectification of induced voltages can occur if the induced voltage is high enough to cause nonlinear
circuit elements to conduct, for example, an input protection diode. Rectification might result in voltage
pulses occurring at a distal electrode. The resulting rectified voltage is an unintended consequence of
the reaction of the AIMD and is not considered a device failure or malfunction, per se.
x © ISO 2018 – All rights reserved
ISO/TS
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