Procedure for the assessment of the exposure to electromagnetic fields of workers bearing active implantable medical devices - Part 2-3: Specific assessment for workers with implantable neurostimulators

This European Standard provides the procedure for the specific assessment required in Annex A of EN 50527 1:2015 for workers with implanted neurostimulators (e.g. spinal cord, deep-brain, retinal, bladder). It offers different approaches for doing the risk assessment. The most suitable one shall be used. If the worker has other Active Implantable Medical Devices (AIMDs) implanted additionally, they have to be assessed separately.

Verfahren zur Beurteilung der Exposition von Arbeitnehmern mit aktiven implantierbaren medizinischen Geräten gegenüber elektromagnetischen Feldern - Teil 2-3: Besondere Beurteilung für Arbeitnehmer mit implantierbaren Neurostimulatoren

Procédure pour l'évaluation de l'exposition des travailleurs porteurs de dispositifs médicaux implantables actifs aux champs électromagnétiques - Partie 2-3 : Evaluation spécifique aux travailleurs porteurs de neurostimulateurs implantés

Le présent document fournit la procédure d’évaluation spécifique exigée dans l’Annexe A de l’EN 50527 1:2016, pour les travailleurs porteurs de systèmes neurostimulateurs (SN) implantés, spécifiquement du type utilisé pour la stimulation médullaire (SM). Il est admis que des neurostimulateurs implantables ont été développés pour un grand nombre d’applications cliniques; toutefois, les dispositifs de SM qui relèvent du domaine d’application du présent document représentent jusqu’à présent le plus grand segment des applications de neurostimulateurs implantables. NOTE 1 Si le travailleur porte, en plus, d’autres dispositifs médicaux implantables actifs (DMIA) implantés, ceux-ci sont évalués de manière individuelle conformément à l’EN 50527 1 ou à d’autres normes particulières de la série EN 50527. Cette évaluation spécifique a pour objet de déterminer, pour des travailleurs porteurs de dispositifs de SM implantés, le risque qui provient de l’exposition aux champs électromagnétiques (EMF – electromagnetic fields) sur le lieu de travail. L’évaluation comprend la probabilité d’effets cliniquement significatifs. NOTE 2 Le présent document ne traite pas des risques vis-à-vis des courants de contact ni des effets sur tout dispositif non implantable associé (par exemple, un dispositif de programmation du patient). Les techniques décrites dans les différentes approches peuvent aussi être utilisées pour l’évaluation des zones accessibles au public. La plage de fréquences à observer comprend le spectre entre 0 Hz et 3 GHz. Au-dessus de 3 GHz, aucune interférence n’est réputée se produire avec les dispositifs qui relèvent du domaine d’application du présent document. NOTE 3 La justification de la limitation de la plage d’observation à 3 GHz peut être consultée dans l’ISO 14708 3 [1]. NOTE 4 Des informations complémentaires relatives aux fonctions des systèmes neurostimulateurs peuvent être consultées à l’adresse https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Spinal-Cord-Stimulation.

Postopek ocenjevanja izpostavljenosti delavcev z aktivnimi medicinskimi vsadki elektromagnetnim poljem - 2-3. del: Specifično ocenjevanje delavcev z vsadljivimi nevrostimulatorji

Ta evropski standard podaja postopek specifičnega ocenjevanja v skladu z dodatkom A standarda EN 50527 1:2015 za delavce z vsajenimi nevrostimulatorji (npr. v hrbtenjači, globoko v možganih, v mrežnici in mehurju). Ponuja različne pristope za izvedbo ocenjevanja tveganja, uporabiti pa je treba najprimernejšega. Če delavec dodatno uporablja druge aktivne medicinske vsadke (AIMD), mora biti ocenjen ločeno.

General Information

Status
Published
Public Enquiry End Date
27-Feb-2020
Publication Date
02-Dec-2021
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
16-Nov-2021
Due Date
21-Jan-2022
Completion Date
03-Dec-2021

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SLOVENSKI STANDARD
SIST EN 50527-2-3:2022
01-januar-2022
Postopek ocenjevanja izpostavljenosti delavcev z aktivnimi medicinskimi vsadki

elektromagnetnim poljem - 2-3. del: Specifično ocenjevanje delavcev z vsadljivimi

nevrostimulatorji

Procedure for the assessment of the exposure to electromagnetic fields of workers

bearing active implantable medical devices - Part 2-3: Specific assessment for workers

with implantable neurostimulators
Ta slovenski standard je istoveten z: EN 50527-2-3:2021
ICS:
11.040.40 Implantanti za kirurgijo, Implants for surgery,
protetiko in ortetiko prosthetics and orthotics
17.240 Merjenje sevanja Radiation measurements
SIST EN 50527-2-3:2022 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 50527-2-3:2022
---------------------- Page: 2 ----------------------
SIST EN 50527-2-3:2022
EUROPEAN STANDARD EN 50527-2-3
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2021
ICS 17.240; 11.040.40
English Version
Procedure for the assessment of the exposure to
electromagnetic fields of workers bearing active implantable
medical devices - Part 2-3: Specific assessment for workers with
implantable neurostimulators

Procédure pour l'évaluation de l'exposition des travailleurs Verfahren zur Beurteilung der Exposition von

porteurs de dispositifs médicaux implantables actifs aux Arbeitnehmern mit aktiven implantierbaren medizinischen

champs électromagnétiques - Partie 2-3 : Evaluation Geräten gegenüber elektromagnetischen Feldern - Teil 2-3:

spécifique aux travailleurs porteurs de neurostimulateurs Besondere Beurteilung für Arbeitnehmer mit

implantés implantierbaren Neurostimulatoren

This European Standard was approved by CENELEC on 2021-08-09. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 50527-2-3:2021 E
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SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)
Contents Page

European foreword ........................................................................................................................................... 6

1 Scope ........................................................................................................................................................... 7

2 Normative references ................................................................................................................................. 7

3 Terms and definitions ................................................................................................................................ 7

4 Specific assessment .................................................................................................................................. 9

4.1 Overview of specific assessments .................................................................................................... 9

4.1.1 Relation to OH&S Management Systems............................................................................ 9

4.1.2 Description of the assessment process ............................................................................... 9

4.2 Specific assessment phase 0: Exclusion based on history and physician warnings ..................... 12

4.3 Specific assessment phase 1: Consideration of equipment and SCS therapy type ...................... 13

4.4 Specific assessment phase 2a – workplace EMF compared to Action Levels .............................. 15

4.5 Overview of specific assessment phases 2b and 2c ...................................................................... 17

4.6 Methodology for assessment of unintended nerve stimulation and tissue damage risk ................ 18

4.6.1 General .............................................................................................................................. 18

4.6.2 Overview of the assessment method given in Annexes D and E ...................................... 18

4.6.3 Selection of device parameters for assessment ................................................................ 19

4.6.4 Assessment levels for electric and magnetic fields ........................................................... 19

4.6.5 NSR and TDR calculation results for unipolar and bipolar configurations ......................... 23

4.6.6 Phase 2a risk assessment summary ................................................................................. 26

4.7 Specific Assessment phase 2b – workplace EMF compared to NSR / TDR EMF threshold

levels 27

4.7.1 Phase 2b general approach ............................................................................................... 27

4.7.2 EMF threshold zones ......................................................................................................... 27

4.7.3 Conversion of EMF values ................................................................................................. 29

4.7.4 Phase 2b assessment procedure ...................................................................................... 29

4.8 Specific assessment phase 2c – adjustments for known lead characteristics ............................... 39

4.8.1 Phase 2c general approach ............................................................................................... 39

4.8.2 Phase 2c assessment procedure ...................................................................................... 41

5 Documentation ......................................................................................................................................... 42

Annex A (normative) Device specific replacement of EN 50527-1:2016, Table 1 ................................... 43

Annex B (informative) Rationale .................................................................................................................. 47

B.1 Introduction ..................................................................................................................................... 47

B.2 Rationale for specific clauses of this document ............................................................................. 47

Annex C (informative) Nerve Stimulation for SCS ..................................................................................... 48

C.1 Neurostimulation techniques .......................................................................................................... 48

C.2 Spinal Cord Stimulation .................................................................................................................. 48

Annex D (informative) Selection of Conductivity Values for SCS Modelling .......................................... 54

D.1 The use of conductivity in the standard .......................................................................................... 54

D.2 Conductivity literature ..................................................................................................................... 54

D.3 Selection of values for tissue Types ............................................................................................... 59

D.4 Summary ........................................................................................................................................ 65

Annex E (informative) Modelling Nerve Stimulation for SCS.................................................................... 66

E.1 Introduction ..................................................................................................................................... 66

E.2 Internal electric field threshold for nerve stimulation ...................................................................... 80

E.3 Avoiding damage to tissue ............................................................................................................. 82

E.4 Assessment of voltages and currents induced in leads ................................................................. 86

E.5 Assessment of nerve stimulation from external fields .................................................................... 93

E.6 Assessment of tissue damage from external fields ........................................................................ 97

E.7 Overall assessment ...................................................................................................................... 100

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SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)

Annex F (informative) Electrode factor for non-isotropic tissue ............................................................ 101

F.1 Application to isotropic tissue ....................................................................................................... 101

F.2 Application to non-isotropic tissue ................................................................................................ 103

Bibliography .................................................................................................................................................. 105

Figures

Figure 1 — Overview of the assessment process ........................................................................................... 11

Figure 2 — Summary of assessment exclusion criteria .................................................................................. 12

Figure 3 — Specific assessment phase 1 ....................................................................................................... 14

Figure 4 — Specific assessment phase 2a — Initial assessment of risk of unintended nerve stimulation or

tissue damage ......................................................................................................................................... 17

Figure 5 — Magnetic field assessment levels as selected (also Figure E.14) ................................................ 21

Figure 6 — Electric field assessment levels as selected (also Figure E.16) ................................................... 22

Figure 7 — Values of NSR for assessed electric field exposures ................................................................... 23

Figure 8 — Values of TDR for assessed electric field exposures ................................................................... 24

Figure 9 — Values of NSR for assessed magnetic field exposures ................................................................ 25

Figure 10 — Values of TDR for assessed magnetic field exposures .............................................................. 26

Figure 11 — Maximum E-field for cylindrical-type bipolar lead stimulation ..................................................... 31

Figure 12 — Maximum E-field for paddle-type bipolar lead stimulation .......................................................... 32

Figure 13 — Maximum B-field for bipolar single lead stimulation ................................................................... 33

Figure 14 — Maximum B-field for bipolar two lead stimulation ....................................................................... 34

Figure 15 — Maximum E-field for unipolar lead stimulation ............................................................................ 35

Figure 16 — Maximum E-field for unipolar lead stimulation (1 MHz to 100 MHz) .......................................... 36

Figure 17 — Maximum B-field for unipolar lead stimulation ............................................................................ 37

Figure 18 — Maximum B-field for unipolar lead stimulation (100 MHz to 5 GHz)........................................... 38

Figure 19 — Specific assessment phase 2c —Re-assessment of tissue damage risk using known lead

characteristics ......................................................................................................................................... 40

Figure C.1 — Typical implantations of spinal cord stimulation devices .......................................................... 49

Figure C.2 — Leads and electrodes for spinal cord stimulation — Paddle leads have flat electrodes and

percutaneous leads have cylindrical electrodes ..................................................................................... 50

Figure C.3 — Cross section of spine showing the different regions ............................................................... 52

Figure D.1 — Conductivity values from 1996 modelled data .......................................................................... 55

Figure D.2 — Conductivities for cerebrospinal tissues (2007 data) ................................................................ 57

Figure D.3 — Conductivities for cerebrospinal tissues (1996 and 2009 data) ................................................ 58

Figure D.4 — Conductivity for fat (not infiltrated, average infiltrated, fully infiltrated) ..................................... 60

Figure D.5 — Cross section of spine showing the different regions ............................................................... 62

Figure D.6 — Layers of tissue adjacent to spinal cord .................................................................................... 63

Figure D.7 — Variation of directional conductivities and their ratio with frequency and the anisotropy factor 64

Figure D.8 — Values of frequency dependent parameters related to conductivity as used in Annex E ......... 65

Figure E.1 — Simplified linear circuit model for isolated patch of excitable membrane. From Reilly 1998. ... 67

Figure E.2 — Calculated strength-duration relationship for square-wave mono-phasic current pulse. From

Reilly 1998. ............................................................................................................................................. 68

Figure E.3 — Representation of myelinated nerve ......................................................................................... 69

Figure E.4 — Electric model for linear cable. From Reilly 1998. ..................................................................... 69

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SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)

Figure E.5 — Equivalent circuit models for excitable membranes. From Reilly 1998. ................................... 70

Figure E.6 — Strength-duration curves for myelinated nerve model with mono-phasic stimuli. Point

electrodes within an infinite homogeneous medium ............................................................................... 72

Figure E.7 — Illustration of the effect of altering separation between electrode and nerve ............................ 73

Figure E.8 — Electrode Factor Multiplier......................................................................................................... 77

Figure E.9 — Strength-duration curve for electric field square wave pulse, exponentially decaying pulse,

sinewave ................................................................................................................................................. 78

Figure E.10 — Variation of internal electric field (peak) sensitivity threshold with frequency ......................... 79

Figure E.11 — ICNIRP 1998 and 2010 Basic Restrictions ............................................................................. 80

Figure E.12 — ICNIRP 2010 Occupational Basic Restriction ......................................................................... 81

Figure E.13 — Variation of maximum current with frequency, expressed as a ratio to the low frequency value

for fully infiltrated fat ................................................................................................................................ 85

Figure E.14 — Magnetic field assessment levels ............................................................................................ 88

Figure E.15 — Voltages (rms) induced by magnetic field for the two assessment levels lines and three loop

areas ....................................................................................................................................................... 89

Figure E.16 — Electric field assessment levels .............................................................................................. 92

Figure E.17 — Voltages (rms) induced by external electric field for the three reference levels and three

electrode spacings .................................................................................................................................. 93

Figure E.18 — NSR for magnetic field exposure ............................................................................................ 95

Figure E.19 — NSR for Electric Field exposure .............................................................................................. 96

Figure E.20 — TDR for magnetic field exposure ............................................................................................. 98

Figure E.21 — TDR for electric field exposure ................................................................................................ 99

Tables

Table 1 — Device parameters used for phase 2a and 2b assessments ......................................................... 19

Table 2 — Assessment levels ......................................................................................................................... 20

Table 3 — Phase 2a assessment summary .................................................................................................... 26

Table 4 — Description of exposure zones for phase 2b assessment procedure ............................................ 28

Table 5 — Applicable zone charts for bipolar stimulation ............................................................................... 29

Table 6 — Applicable zone charts for unipolar stimulation ............................................................................. 30

Table 7 — Information necessary to proceed with phase 2c .......................................................................... 39

Table 8 — NSR modifiers for field levels in Zones 2b, 2c, or 2d ..................................................................... 41

Table 9 — Example calculations for phase 2c assessment ............................................................................ 41

Table A.1 — Compliant workplaces and equipment with exceptions .............................................................. 43

Table C.1 — Summary of maximum values of key dimensions ...................................................................... 51

Table C.2 — Types of connection ................................................................................................................... 53

Table D.1 — Conductivity of fat and CSF from 50 kg pigs at selected frequencies........................................ 56

Table D.2 — Measurements illustrating the variation of conductivity with age for pigs .................................. 56

Table D.3 — Conductivity information required ............................................................................................... 59

Table D.4 — Conductivities of fat in S/m ......................................................................................................... 61

Table D.5 — Conductivities in CSF in S/m ...................................................................................................... 61

Table D.6 — Cerebrospinal tissues: thickness and materials types ............................................................... 62

Table E.1 — Basic case parameters used in SENN model ............................................................................ 71

Table E.2 — ICNIRP 2010 Occupational Basic Restriction for in situ electric field ........................................ 81

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SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)

Table E.3 — Multiplying factors for higher levels of stimulation ...................................................................... 82

Table E.4 — Maximum allowable electrode current for different electrode areas and averaging volumes

0.5

where σ = 0.085 S/m. (Values vary as σ ) ............................................................................................ 84

Table E.5 — Exposure Levels used for the assessments ............................................................................... 87

Table E.6 — Maximum NSR from magnetic field exposures .......................................................................... 95

Table E.7 — Maximum NSR from electric field exposures ............................................................................. 97

Table E.8 Maximum TDR from magnetic field exposures ............................................................................... 98

Table E.9 — Maximum TDR from electric field exposures .............................................................................. 99

Table E.10 — Overall assessment summary ................................................................................................ 100

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SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)
European foreword

This document (EN 50527-2-3:2021) has been prepared by CLC/TC 106X “Electromagnetic fields in the

human environment”.
The following dates are fixed:
• latest date by which this document has to be (dop) 2022-08-09
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2024-08-09
conflicting with this document have to be
withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a Standardization Request given to CENELEC by the European

Commission and the European Free Trade Association.

Any feedback and questions on this document should be directed to the users’ national committee. A complete

listing of these bodies can be found on the CENELEC website.
---------------------- Page: 8 ----------------------
SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)
1 Scope

This document provides the procedure for the specific assessment required in EN 50527-1:2016, Annex A, for

workers with implanted neurostimulator systems (NS), specifically of the type used for spinal cord stimulation

(SCS).

It is recognized that implantable neurostimulators have been developed for a wide variety of clinical

applications, however the SCS devices within the scope of this document represent the largest segment of the

implantable neurostimulator applications thus far.

NOTE 1 If the worker has other Active Implantable Medical Devices (AIMDs) implanted additionally, they are assessed

separately according to EN 50527-1 or other particular standards within the EN 50527 series.

The purpose of the specific assessment is to determine the risk for workers with implanted SCS devices arising

from exposure to electromagnetic fields (EMF) at the workplace. The assessment includes the likelihood of

clinically significant effects.

NOTE 2 This document does not address risks from contact currents, or the effects upon any associated non-

implantable devices (e.g. Patient Programmers).

The techniques described in the different approaches can also be used for the assessment of publicly

accessible areas.

The frequency range to be observed is from 0 Hz to 3 GHz. Above 3 GHz no interference with the devices

within the scope of this document is expected to occur.

NOTE 3 The rationale for limiting the observation range to 3 GHz can be found in ISO 14708-3 [1].

NOTE 4 Further information concerning the functions of neurostimulator systems can be found at

https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Spinal-Cord-Stimulation.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes

requirements 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.

EN 50527-1:2016, Procedure for the assessment of the exposure to electromagnetic fields of workers bearing

active implantable medical devices - Part 1: General
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 50527-1:2016 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
implantable pulse generator
IPG

part of the active implantable medical device, including the power supply and electronic circuit that produces

an electrical output
3.2
neurostimulator system

active implantable medical device comprising an implantable pulse generator and therapy delivering electrodes

usually part of implanted electrical leads that are intended to deliver therapy to a patient by electrically

stimulating certain nerve structures, along with an associated external patient programming device

---------------------- Page: 9 ----------------------
SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)
3.3
electrode

electrically conducting part (usually the termination of a lead) which is designed to form an interface with body

tissue or body fluid
3.4
bipolar lead
lead with at least two electrodes that are electrically isolated from each other
3.5
AIMD-Employee
worker with an active implantable medical device

Note 1 to entry: For the purposes of this document, the term AIMD-Employee refers to the patient whose implant consists

of a neurostimulator system of the type intended for spinal cord stimulation.
3.6
assessment team
team consisting of:

— employer and if applicable, his occupational health and safety experts and/or occupational physician;

— AIMD-Employee and his responsible physician;

— (technical and medical) experts as necessary, e.g. manufacturer of the device

3.7
unipolar stimulation

stimulation using a single electrode with reference to the outer shell of the implantable pulse generator

3.8
single lead bipolar stimulation
stimulation using two or more adjacent electrodes of a single lead structure

Note 1 to entry: Leads for use with SCS devices typically have a minimum of 8 electrodes.

3.9
two lead bipolar stimulation

stimulation using two or more electrodes located on two separate leads that are implanted in close proximity

to one another
3.10
device
implanted spinal cord stimulator
3.11
electromagnetic field
EMF

alternating electric field, alternating magnetic field, or radio wave between

1 Hz and 3 GHz whether continuous, pulsed, or modulated in space or time
3.12
spinal cord stimulator
SCS

neurostimulator system designed specifically for stimulation of the human spinal cord to treat chronic pain by

electrically stimulating the spinal cord but not the Dorsal Root Ganglion (DRG)
---------------------- Page: 10 ----------------------
SIST EN 50527-2-3:2022
EN 50527-2-3:2021 (E)
3.13
General Public Reference Level
GPRL

measurable level of electric or magnetic field strength given in Council Recommendation 1999/519/EC for the

general public environment, exposure to which is not considered harmful for persons not bearing an active

implant
3.14
nerve stimulation ratio
NSR

ratio of the electric field at the spinal cord induced by external electromagnetic fields, to the electric field level

below which the AIMD-Employee is not expected to perceive nervous system stimulation

3.15
tissue damage ratio
TDR

ratio of the electrode current induced by external electromagnetic fields, to the current for a given electrode

area below which the AIMD-Employee is not expected to undergo any damage to the tissues surrounding the

implanted electrode
4 Specific assessment
4.1 Overview of specific assessments
4.1.1 Relation to OH&S Management Systems

Nonionizing radiation is a hazard to the health of workers. Whether this hazard constitutes a risk i

...

SLOVENSKI STANDARD
oSIST prEN 50527-2-3:2020
01-februar-2020
Postopek ocenjevanja izpostavljenosti delavcev z aktivnimi medicinskimi vsadki

elektromagnetnim poljem - 2-3. del: Specifično ocenjevanje delavcev z vsadljivimi

nevrostimulatorji

Procedure for the assessment of the exposure to electromagnetic fields of workers

bearing active implantable medical devices - Part 2-3: Specific assessment for workers

with implantable neurostimulators
Ta slovenski standard je istoveten z: prEN 50527-2-3
ICS:
11.040.40 Implantanti za kirurgijo, Implants for surgery,
protetiko in ortetiko prosthetics and orthotics
17.240 Merjenje sevanja Radiation measurements
oSIST prEN 50527-2-3:2020 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 50527-2-3:2020
---------------------- Page: 2 ----------------------
oSIST prEN 50527-2-3:2020
EUROPEAN STANDARD DRAFT
prEN 50527-2-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2019
ICS
English Version
Procedure for the assessment of the exposure to
electromagnetic fields of workers bearing active implantable
medical devices - Part 2-3: Specific assessment for workers with
implantable neurostimulators
To be completed To be completed
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2020-02-28.
It has been drawn up by CLC/TC 106X.

If this draft becomes a European Standard, CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which

stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CENELEC in three official versions (English, French, German).

A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to

the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to

provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and

shall not be referred to as a European Standard.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Project: 66708 Ref. No. prEN 50527-2-3 E
---------------------- Page: 3 ----------------------
oSIST prEN 50527-2-3:2020
prEN 50527-2-3:2019 (E)
Contents Page

European foreword ........................................................................................................................................... 3

1 Scope ........................................................................................................................................................... 4

2 Normative references ................................................................................................................................. 4

3 Terms and definitions ................................................................................................................................ 4

4 Specific assessment .................................................................................................................................. 6

4.1 Description of the assessment process ............................................................................................ 6

4.1.1 General ................................................................................................................................ 6

4.1.2 Exclusion based on history and physician warnings ........................................................... 8

4.1.3 Specific assessment phase 1: Consideration of equipment and SCS therapy type ........... 9

4.1.4 Equipment consideration ................................................................................................... 10

4.1.5 Specific assessment phase 2: Ruling out extrinsic stimulation and tissue damage .......... 11

4.1.6 Specific assessment phase 3: Assessment of clinical effects using in vivo testing .......... 11

4.2 Assessment of extrinsic stimulation and tissue damage risk ......................................................... 12

4.2.1 General .............................................................................................................................. 12

4.2.2 Overview of the Assessments Method given in Annexes D and E .................................... 13

4.2.3 Selection of Parameters Affecting the Assessment ........................................................... 13

4.2.4 Examples of assessment for unipolar configuration .......................................................... 15

4.2.5 Overall Assessment ........................................................................................................... 17

4.2.6 Further Assessment ........................................................................................................... 19

4.2.7 Concluding phase 2 assessment ....................................................................................... 20

4.3 Specific Assessment Phase 3: Clinical Evaluation ......................................................................... 20

4.3.1 Considerations in choosing a clinical method .................................................................... 20

4.3.2 Conducting in vivo tests ..................................................................................................... 21

5 Documentation ......................................................................................................................................... 22

Annex A (normative) Device specific replacement of EN 50527-1:2016, Table 1 ................................... 23

Annex B (informative) Clinical investigation methods .............................................................................. 30

Annex C (informative) Rationale .................................................................................................................. 31

Annex D (informative) Nerve Stimulation for SCS ..................................................................................... 32

Annex E (informative) Modelling Nerve Stimulation for SCS.................................................................... 38

Bibliography .................................................................................................................................................... 70

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European foreword

This document (prEN 50527-2-3:2019) has been prepared by CLC/TC 106X “Electromagnetic fields in the

human environment”.
This document is currently submitted to the Enquiry.
The following dates are proposed:
• latest date by which the existence of this (doa) dor + 6 months
document has to be announced at national
level
• latest date by which this document has to be (dop) dor + 12 months
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) dor + 36 months
conflicting with this document have to be (to be confirmed or
withdrawn modified when voting)

This document has been prepared under a mandate given to CENELEC by the European Commission and

the European Free Trade Association.
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1 Scope

This document provides the procedure for the specific assessment required in EN 50527-1:2016, Annex A, for

workers with implanted neurostimulator systems (NS), specifically of the type used for spinal cord stimulation

(SCS).

It is recognized that implantable neurostimulators have been developed for a wide variety of clinical

applications, however the SCS devices within the scope of this document represent the largest segment of the

implantable neurostimulator applications thus far.

NOTE 1 If the worker has other Active Implantable Medical Devices (AIMDs) implanted additionally, they are assessed

separately according to EN 50527-1 or other particular standards within the EN 50527 series.

The purpose of the specific assessment is to determine the risk for workers with implanted SCS devices arising

from exposure to electromagnetic fields (EMF) at the workplace. The assessment includes the likelihood of

clinically significant effects and takes both transient and long-term exposure within specific areas of the

workplace into account.

NOTE 2 This document does not address risks from contact currents or the effects upon any associated external

devices.

The techniques described in the different approaches can also be used for the assessment of publicly

accessible areas.

The frequency range to be observed is from 0 Hz to 3 GHz. Above 3 GHz no interference with the devices

within the scope of this document is expected to occur.

NOTE 3 The rationale for limiting the observation range to 3 GHz can be found in ISO 14708-3.

NOTE 4 Further information concerning the functions of neurostimulator systems can be found at

https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Spinal-Cord-Stimulation.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes

requirements 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.

EN 50527-1:2016, Procedure for the assessment of the exposure to electromagnetic fields of workers bearing

active implantable medical devices - Part 1: General

EN ISO 14155, Clinical investigation of medical devices for human subjects — Good clinical practice

(ISO 14155)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 50527-1:2016 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
implantable pulse generator
IPG

part of the active implantable medical device, including the power supply and electronic circuit that produces

an electrical output
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3.2
neurostimulator system

active implantable medical device comprising an implantable pulse generator and includes therapy delivering

electrodes usually part of implanted electrical leads that are intended to deliver therapy to a patient by

electrically stimulating certain nerve structures, along with an associated external patient programming device

3.3
electrode

electrically conducting part (usually the termination of a lead) which is designed to form an interface with body

tissue or body fluid
3.4
bipolar lead
lead with at least two electrodes that are electrically isolated from each other
3.5
AIMD-Employee
worker with an active implantable medical device

Note 1 to entry: For the purposes of this document, the term AIMD-Employee refers to the patient whose implant consists

of a neurostimulator system of the type intended for spinal cord stimulation.
3.6
assessment team
team consisting of:

— employer and if applicable, his occupational health and safety experts and/or occupational physician;

— AIMD-Employee and his responsible physician;
— (technical and medical) experts as necessary, e.g. manufacturer of the device
3.7
unipolar stimulation

stimulation using a single electrode with reference to the outer shell of the implantable pulse generator

3.8
single lead bipolar stimulation
stimulation using two or more adjacent electrodes of a single lead structure

Note 1 to entry: Leads for use with SCS devices typically have a minimum of 8 electrodes.

3.9
two lead bipolar stimulation

stimulation using two electrodes located on two separate leads that are implanted in close proximity to one

another
3.10
EM phantom

physical model containing tissue-equivalent material used to simulate the body in an experimental dose

measurement

Note 1 to entry: EM phantoms are sometimes also referred to as torso simulator or phantom.

[SOURCE: World Health Organization]
3.11
uninfluenced behaviour
conditions for uninfluenced behaviour are provided in EN 50527-1:2016, 4.1.3
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3.12
device
implanted spinal cord stimulator
3.13
electromagnetic field
EMF

alternating electric field, alternating magnetic field, or radio wave between

1 Hz and 3 GHz whether continuous, pulsed, or modulated in space or time
3.14
static field
static magnetic field
SMF
static electric field
SEF

static (stationary) or quasi-static (below 1 Hz) electric field or magnetic field whether continuous, pulsed, or

modulated in space or time
3.15
spinal cord stimulator
SCS

neurostimulator system designed specifically for stimulation of the human spinal cord to treat chronic pain by

electrically stimulating the spinal cord but not the Dorsal Root Ganglion (DRG)
4 Specific assessment
4.1 Description of the assessment process
4.1.1 General

Spinal Cord Stimulation (SCS) is generally used for chronic pain reduction. The stimulation does not provide

therapy in direct relation to AIMD-Employee safety, so changes to therapy, or turning therapy off, does not

pose a specific risk to the AIMD-Employee. It is noted that an AIMD-Employee can also receive therapy

changes which may appear as a “shock” or “jolt” due to abrupt movements such as coughing and laughing as

well as from postural changes such as standing up from seating, or vice versa. These are not significant direct

risk situations to the AIMD-Employee, but there may be indirect implications due to the nature of the occupation

or positioning. A workplace risk assessment does not need to be based on an absence of risk or effect. It can

be made using a balance of the benefits and the identified possible effects, both direct and indirect, due to the

nature of the employment.

The risks to an AIMD-Employee resulting from to EMF or SF exposure in the workplace includes the following

categories:

— that the implanted SCS may itself be influenced in a way that leads to temporary or permanent loss of

therapy, or delivery of a corrupted form of therapy that might not meet the needs of the patient such that

they might be unable to carry out their employee functions. ISO 14708-3 is the product standard that

addresses the risks of malfunction and damage to the SCS NS when exposed to EMF or SF. The working

group has deemed the risks to the AIMD-Employee related to malfunction and device damage to be

acceptable, and they are therefore not addressed by this document. See C.2 for additional rationale.

— that the AIMD-Employee may experience additional effects upon their nervous system due to extrinsic

stimulation arising from induced currents in their implanted lead system. These effects can include

unpleasant sensations, up to and including “shocking” and “jolting”,

— that the induced currents are of sufficient magnitude to cause nerve tissue damage. This risk would occur

at higher exposure levels and where the EMF frequencies are high enough that they would not be

perceived by the AIMD-Employee.
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To address these risks, this document describes a multi-phase risk assessment as summarized in Figure 1.

— Exclusion from further assessment based upon a consideration of prior history

— Exclusion from further assessment based upon a survey of the equipment in the workplace

— Exclusion from further assessment if the AIMD-Employee has a stimulator where outputs can be shut off

in high-impedance mode and is able to work with the stimulator in this mode receiving no therapy while at

the workplace.

— Assessment of the likelihood that the extrinsically induced current arising from the EMF environment of

the workplace will exceed the stimulation threshold (i.e. limit of perceived stimulation) for the spinal cord

portion of the human nervous system. Further assessment is prescribed where extrinsic stimulation cannot

be ruled out.

— Assessment of the likelihood that the extrinsically induced current arising from the EMF environment of

the workplace could cause damage to the tissues of the spinal cord. This risk is present when the

characteristics of the extrinsically induced currents are such that they are not perceived by the AIMD-

Employee, yet are of sufficient magnitude to result in a level of deposited power as to cause tissue damage

as a result of tissue heating. . The underlying approach is first to allow work without restriction if it can be

determined that no extrinsic stimulation and no tissue damage would occur,

— Where the risk of tissue damage has been ruled out, but extrinsic stimulation has not been ruled out,

assessment of actual stimulation effects. Since the consequences of unintended stimulation vary widely

from one individual to another the assessment necessarily involves in vivo testing.

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Figure 1 — Overview of the assessment process
4.1.2 Exclusion based on history and physician warnings

Further risk assessment is not necessary if a history of uninfluenced behaviour at the workplace exists and a

responsible physician has confirmed that this history is sufficient to exclude clinically significant interaction.

When a SCS NS is tested according to ISO 14708-3, the manufacturer is required to provide a warning to the

implanting physician in the accompanying technical information as to any settings available in the device that

if used, afford the device with a reduced immunity to certain types of EMI. A specific warning would only be

given to the patient receiving the implant if they were discharged with one of these settings in effect, or if at

follow-up, a change to one of these settings was made for clinical reasons.

Figure 2 summarizes the situations where further risk assessment is unnecessary, and where a specific

assessment (beginning with 4.1.3) is required.
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Figure 2 — Summary of assessment exclusion criteria

4.1.3 Specific assessment phase 1: Consideration of equipment and SCS therapy type

To minimize the burden on the employer and AIMD-employee, the specific assessment begins with a first

phase in which it is determined if work can be allowed based upon considerations of equipment in the

workplace.

A specific risk assessment for the AIMD-Employee is required when there is history of influenced behaviour or

one of the following five conditions exists:

a) there is equipment present in the workplace that is neither included in, nor used in accordance with

Table A.1;

b) all equipment at the workplace is listed in Table A.1 (see Annex A) and is used accordingly, but the AIMD-

Employee has received warning(s) from the responsible physician that their device might be susceptible

to static fields (SF) or electromagnetic fields (EMF) associated with particular types of equipment, thereby

increasing the risk at the workplace.

c) there is equipment present in the workplace that is neither included in, nor used in accordance with

Table A.1 and for which the AIMD-Employee does not have a history of device behaviour (uninfluenced

or otherwise) while in its presence, but the AIMD-Employee has received a specific warning as described

in 4.1.1 b).

Figure 3 depicts phase 1 of the specific assessment. The steps to be taken are based upon a consideration of

equipment in the workplace and consultation with the responsible physician.

When any of the conditions a) through c) exist, 4.1.4 applies. Otherwise, no further assessment is required,

and documentation of the assessment can proceed as required in Clause 5.
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Figure 3 — Specific assessment phase 1
4.1.4 Equipment consideration

Information relevant to the equipment or other field generating sources under consideration shall be collected

to answer sufficiently the following two questions:

— can it be determined that clinically significant interference with the device will not occur as a result of

expected exposure to the equipment under consideration? If so, no further assessment is required, and

documentation of the result can proceed, as required in Clause 5;
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— can it be determined that the AIMD-Employee can return to the workplace only with restrictions placed on

the work tasks or areas of access? If so, no further assessment is required, and documentation of the

work restrictions can proceed as required in Clause 5.

When neither of these questions can be answered positively, the assessment continues to phase 2, as

described in 4.1.5.

The intent of this subclause is to find and utilize information that might already exist and that allows the

assessment to be completed without further, costlier and time-consuming effort. It is recommended that

experts who are likely to have such information be contacted. Examples of such experts are the device

manufacturer, equipment manufacturer, employer’s technical department, consultants, or others skilled in EMF

and SF effects with implanted devices.

4.1.5 Specific assessment phase 2: Ruling out extrinsic stimulation and tissue damage

When steps of the specific assessment phase 1 shown in Figure 3 have been followed but fail to mitigate or

to dismiss risk to the AIMD-Employee from the effects of workplace EMF or SF, then additional investigation

shall be performed as shown in Figure 4. The goal of Phase 2 investigation is to rule out the risk of extrinsic

stimulation, and tissue damage.

The first step of phase 2 is to determine the levels of SF or EMF associated with the equipment in question.

This is ordinarily done by performing an EMF site survey wherein the fields are measured directly in the

workplace at the separation distances expected in daily exposure for the AIMD-Employee. Such

measurements should account for seasonal variations (if any), as well as measurement at lesser distances to

better understand the boundaries where higher exposures might occur. The results are then assessed using

the methodology described in 4.2.

Coincident with the workplace site survey, it is necessary to collect information concerning the specific implant

situation. As a minimum, it is necessary to know the type of stimulation in use (unipolar, bipolar or multipolar

single lead, or bipolar two-lead). Additional information that is useful includes an approximation of the

implanted loop area, proximity of lead electrodes to the spinal cord, the electrode area(s) for the specific leads

implanted, and whether the implantable pulse generator carries an MRI conditional approval. These items of

information might be available from the implanting physician. Otherwise, in the absence of such information, it

should be assumed that the nominal conditions of implant as described in 4.2 apply.

Device “off” exclusion

If it is learned that the AIMD-employee is receiving unipolar stimulation and SCS device re-programming to

bipolar stimulation is not possible, and the AIMD-Employee has a stimulator whose outputs can be shut off in

high-impedance mode, and the AIMD-Employee is able to work with the stimulator in this mode receiving no

therapy, the AIMD-employee is allowed to work with this restriction.

4.1.6 Specific assessment phase 3: Assessment of clinical effects using in vivo testing

There can exist situations where the results from 4.2 indicate that the risk of tissue damage is negligible, yet

the EMF exposure levels are such that perception of them by the AIMD-Employee cannot be ruled out. In these

situations, the specific assessment continues with the consideration of applying in vivo testing. The

requirements for this phase of the assessment are described in 4.3.
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Figure 4 — Specific assessment phase 2 — Ruling out malfunction and extrinsic stimulation

4.2 Assessment of extrinsic stimulation and tissue damage risk
4.2.1 General

Assessment of the risk of extrinsic induced stimulation that might exceed the threshold of perception is a

complex topic. Annex E together with Annex D, has been developed to provide an analysis methodology for

determination of whether or not an external EMF will be of sufficient magnitude to result in stimulation of the

spinal cord by way of induced currents and internal fields.
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The risk of extrinsic induced voltages that might result in damage to tissue adjacent to the electrodes is also a

developed in Annex E.
4.2.2 Overview of the Assessments Method given in Annexes D and E

Annex D introduces the SCS devices and important parameters associated with their use.

The SENN model (Spatially Extended Nonlinear Node model), which is used for modelling stimulation of

nerves by internal electric fields in the body, is introduced in E.1 and E.2 and based on the work of J.P Reilly.

The values of the ICNIRP internal electric field Basic Restriction for nerve stimulation is used for assessing

nerve stimulation that may arise from external magnetic and electric fields. In E.3 the values of the ICNIRP

internal electric field Basic Restriction for local heating in the body, are used in the assessment of whether or

not tissue damage may occur.

The method for assessing whether nerve stimulation will be caused by external fields is based on evaluating

the quantity which is referred to as the Nerve Stimulation Ratio (NSR). If the NSR is greater than 1 then nerve

stimulation may occur, and if it is less than 1 nerve stimulation is not expected.

The stages of the method for assessing nerve stimulation are set out in E.5.1, and the results of the

assessment are contained in the remainder of E.5.

The method for assessing whether tissue damage will be caused by external fields is based on evaluating the

quantity which is referred to as the Tissue Damage Ratio (TDR). If the TDR is greater than one then nerve

stimulation may occur, and if it is less than 1 tissue damage is not expected.

The stages of the method for assessing tissue damage are set out in E.6.1, and the results of the assessment

are contained in the remainder of E.6.

The methods for assessing whether nerve stimulation and tissue damage occurs both depend on calculating

the voltage induced by the external fields between the electrodes by the external fields (electric and magnetic),

and the current flowing in the tissue between the electrodes. These are presented in E.4.

The assessments of E.5 and E.6 are brought together in 4.2.5 below and E.7.

In some situations, further assessment is required. The approach for this is given in E.8 and reproduced here.

4.2.3 Selection of Parameters Affecting the Assessment

The outcome of the assessment depends on many different parameters. To simplify this, assessments have

been carried out for a few particular sets of parameters representative of worst cases.

Lead configuration

The leads between the IPG and electrode site form a loop in which voltages may be induced by magnetic

fields. The lead configuration affects loop area which in turn affects the induced voltage. The areas used are

2 2 2

as follows: 612 cm for unipolar, 140 cm for bipolar (using two leads) and 10 cm for bipolar (using one lead).

Electrode spacing

The spacing of implanted electrodes affects the voltage induced between them. The spacings used are 50 cm

for unipolar, 5,4 cm for percutaneous leads and 3,7 cm for paddle electrodes.
Electric and magnetic fields

Values of electric and magnetic fields for this assessment are shown in Figure 5 and Figure 6, respectively.

Two sets of values are used for frequencies between 1 Hz and 10 GHz. The two lines used are:

— the Low Action Level from the EU EMF Directive for exposure of worker;

— the Reference Level from the EU EMF Recommendation for exposures to the General Public.

These are representative of the higher fields that may be found
...

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