Health informatics -- Medical waveform format

This document specifies a heterogeneous format of neurophysiological waveform signals to support recording in a single persistent record package as well as interoperable exchange. The document focuses on electroencephalography (EEG) waveforms created during EEG examinations. Specific provision is made for sleep polysomnography examinations (PSG), brain death determination, evoked potentials (EP), and electromyography (EMG) studies. This document is intended for neurophysiology.

Informatique de santé -- Format de la forme d'onde médicale

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Published
Publication Date
27-Apr-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
15-Mar-2021
Completion Date
15-Mar-2021
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TECHNICAL ISO/TS
SPECIFICATION 22077-5
First edition
2021-04
Health informatics — Medical
waveform format —
Part 5:
Neurophysiological signals
Reference number
ISO/TS 22077-5:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TS 22077-5:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 22077-5:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 1

5 General ............................................................................................................................................................................................................................ 2

5.1 Overview of the rules ........................................................................................................................................................................ 2

5.2 Configuration of waveform data .............................................................................................................................................. 2

5.3 Time synchronization ....................................................................................................................................................................... 3

6 Waveform encoding ........................................................................................................................................................................................... 5

6.1 General ........................................................................................................................................................................................................... 5

6.1.1 Application of EEG studies ...................................................................................................................................... 5

6.1.2 Full disclosure waveforms ....................................................................................................................................... 6

6.1.3 Intermittent record waveforms .......................................................................................................................... 6

6.2 Waveform class ....................................................................................................................................................................................... 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 Waveform Class for EEG, PSG, EP, EMG ......................................................................................................... 7

6.3 Waveform attributes (lead names) ........................................................................................................................................ 9

6.3.1 Waveform code .................................................................................................................................................................. 9

6.3.2 EEG ............................................................................................................................................................................................10

6.3.3 PSG, EOG, EMG, EP, RESP ........................................................................................................................................10

6.3.4 ECG ............................................................................................................................................................................................11

6.4 Sampling attributes ..........................................................................................................................................................................12

6.4.1 General...................................................................................................................................................................................12

6.4.2 MWF_IVL (0Bh): Sampling rate ........................................................................................................................12

6.4.3 MWF_SEN (0Ch): Sampling resolution ......................................................................................................13

6.5 Frame attributes .................................................................................................................................................................................13

6.6 Pointer .........................................................................................................................................................................................................13

6.7 Filter ..............................................................................................................................................................................................................14

7 Event information ............................................................................................................................................................................................14

7.1 General ........................................................................................................................................................................................................14

7.2 Measurement status – related events...............................................................................................................................15

Annex A (informative) MFER conformance statement ....................................................................................................................16

Annex B (informative) EEG electrode code .................................................................................................................................................17

Annex C (informative) Example of waveform encoding .................................................................................................................23

Bibliography .............................................................................................................................................................................................................................34

© ISO 2021 – All rights reserved iii
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ISO/TS 22077-5:2021(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 215, Health informatics.

A list of all parts in the ISO 22077 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 22077-5:2021(E)
Introduction

Neurophysiological signals are used to monitor and assess an individual’s brain activity for a wide array

of clinical examinations including sleep polysomnography (PSG), determination of brain death, evoked

potentials (EP), and electromyography (EMG).

Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical

activity of the brain. It is typically non-invasive, with multiple electrodes placed along the scalp (see

Figures B.1 and B.2). Diagnostic applications generally focus on the spectral content of EEG, that is, the

type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals. EEG

is most often used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to

diagnose sleep disorders, coma, encephalopathies, and brain death.

PSG examinations include monitoring the condition of the body during sleep at night. Confirmed diagnosis

of sleeping disorders and sleeping respiratory disorders is supported by recording neurophysiological

signals through electrodes. By measuring brain waves, eye movements, electromyogram movements,

etc., the depth of sleep (sleep stage), quality, presence or absence of midwake arousal, respiration by

breathing, snoring, oxygen saturation, etc., can be assessed.

To correctly interpret neurophysiological changes, medical device systems need to capture

these data, along with additional waveforms such as the respiration, SpO2, EOG (eye movement).

Healthcare providers and clinical specialists who perform these examinations greatly benefit from

interoperability – having all the examination data recorded in a single standardized package or file that

can be safely and securely managed and exchanged.

The purpose of this document is to describe the heterogeneous neurophysiological waveforms and

related data that can be normalized to a standard semantic representation and format and persisted

in a single package. The specification also supports the time synchronization of these waveforms and

related parametric data so that the clinician receiving the data package is able to better assess the

patient’s condition throughout the examination period.
About Medical waveform Format Encoding Rules (MFER)

The MFER standards address several challenges that are not limited to either EEG waveforms or the

neurophysiological assessments that are the main subject of this document:

— Simple and easy implementation: application of MFER is very simple and is designed to facilitate

understanding, easy installation, trouble-shooting, and low implementation cost.

— Using with other appropriate standards: it is recommended that MFER only describes

medical waveforms. Other information can be described using appropriate standards such as

1) 2) 3)

HL7® , DICOM® , IEEE® , etc. For example, clinical reports that include patient demographics,

order information, medication, etc. are supported in other standards such as HL7® Clinical

Document Architecture (CDA). By including references to MFER information in these documents,

implementation for message exchange, networking, database management that includes waveform

information becomes simple and easy.

— Separation between supplier and consumer of medical waveforms: the MFER specification

concentrates on data format instead of paper-based recording. For example, recorded ECG/EEG are

processed by filter, data alignment, and other parameters, so that the ECG waveform can be easily

displayed using an application viewer. However, it is not as useful for other purposes such as data

1) HL7 is the registered trademark of Health Level Seven International. This information is given for the convenience

of users of this document and does not constitute an endorsement by ISO of the product named.

2) DICOM is the registered trademark of the National Electrical Manufacturers Association for its standards

publications relating to digital communications of medical information. This information is given for the convenience

of users of this document and does not constitute an endorsement by ISO of the product named.

3) IEEE is a registered trademark of Institute of Electrical and Electronics Engineers, Inc. This information is given

for the convenience of users of this document and does not constitute an endorsement by ISO of the product named.

© ISO 2021 – All rights reserved v
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ISO/TS 22077-5:2021(E)

processing for research investigations. A design goal of MFER is that a waveform is described in

raw format with as complete as possible recording detail. When the waveform is used, appropriate

processing of the data are supported like filtering, view alignment and so on. In this way, the medical

waveform described in MFER can be used for multiple purposes.

— Product capabilities are not limited: standards often support only a minimum set of requirements,

so the expansion of product features can be greatly limited. MFER can describe medical waveform

information without constraining the potential features of a product. Also, medical waveform

display must be very flexible, and thus MFER has mechanisms supporting not only a machine-

readable coded system for abstract data, but also human-readable representation.

The MFER specification supports both present and future product implementations. MFER supports the

translation of stored waveform data that was encoded using other standards, enabling harmonization

and interoperability. This capability supports not only existing waveform format standards but can be

extended to support future formats as well.
vi © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL SPECIFICATION ISO/TS 22077-5:2021(E)
Health informatics — Medical waveform format —
Part 5:
Neurophysiological signals
1 Scope

This document specifies a heterogeneous format of neurophysiological waveform signals to support

recording in a single persistent record package as well as interoperable exchange. The document focuses

on electroencephalography (EEG) waveforms created during EEG examinations. Specific provision is

made for sleep polysomnography examinations (PSG), brain death determination, evoked potentials

(EP), and electromyography (EMG) studies.
This document is intended for neurophysiology.
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.

ISO 22077-1:2015, Health informatics — Medical waveform format — Part 1: Encoding rules

ISO/TS 22077-3:2015, Health informatics — Medical waveform format — Part 3: Long term

electrocardiography
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 22077-1:2015 apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Symbols and abbreviated terms
CO2 Carbon dioxide
DC Direct Current
DICOM Digital Imaging and Communication in Medicine
ECG Electrocardiography
EEG Electroencephalography
EMG Electromyography
EOG Electrooculography
© ISO 2021 – All rights reserved 1
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ISO/TS 22077-5:2021(E)
EP Evoked potentials
HPF High-frequency pass filter
IEEE Institute of Electrical and Electronic Engineers
LOINC® Logical Observation Identifiers Names and Codes
LPF Low-frequency pass filter
MFER Medical waveform Format Encoding Rules
PSG Polysomnography
SEP Somatosensory evoked potential
SNOMED-CT® Systematized Nomenclature of Medicine-Clinical Terms
SpO2 Saturation of peripheral oxygen

LOINC is the registered trademark of Regenstrief Institute, Inc. This information is given for the con-

venience of users of this document and does not constitute an endorsement by ISO of the product named.

SNOMED CT is the registered trademark of the International Health Terminology Standards Devel-

opment Organisation (IHTSDO). This information is given for the convenience of users of this document

and does not constitute an endorsement by ISO of the product named.
5 General
5.1 Overview of the rules

All MFER content (see ISO 22077-1:2015, 4.2.2), including the file header and waveform data, should be

encoded based on the encoding rules that are composed of the tag, length and value (TLV), 3-tuple as

shown in Figure 1.
Figure 1 — Data unit

— The tag (T) consists of one or more octets and indicates the attribute of the data value.

— The data length (L) is the length of data values indicated in one or more octets.

— The value (V) is contents which are indicated by tag (T); e.g. attribute definition, waveform data,

etc.

In order to make effective use of this document, a MFER conformance statement is provided in Annex A

and sample waveform description are provided in Annex C.
5.2 Configuration of waveform data

Medical waveform data described in accordance with the MFER is an aggregate of waveform frame data

that consists of a header section (encoding detailed information about the waveform) and a waveform

data section (main data of waveform). See Figure 2. The header and waveform data are encoded based

on the encoding rules that are composed of TLV (Tag - Data length - Value). One MFER waveform file can

include several waveforms. The content of an MFER waveform file is sequentially interpreted from the

beginning of the file, and a single file can contain multiple waveform definitions. Given the sequential

2 © ISO 2021 – All rights reserved
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ISO/TS 22077-5:2021(E)

precedence processing for an MFER file, a waveform definition applies until another definition with the

same tag is encountered. In this case, the subsequent definition replaces the preceding definition for

the same waveform.

Additionally, the definition for one waveform can be used, by reference, to define additional waveforms

in the MFER file. For example, a 60 channel EEG might only require four core waveform specifications,

with the other channels referring to the same definition, providing simplification of the overall file

complexity.

When there are several waveforms in a MFER waveform file, each waveform can be located anywhere in

the file; however, in the specification of data generated during EEG and other examinations, waveform

frames should be located as shown in Figure 2 to enhance usability and avoid erroneous interpretation:

— The information about EEG examination and others should be described before description of

waveform [i.e. in (a) and (d) content should be included before (e)]. For this document, the waveform

class definition(s) (MWF_WFM) are for neurophysiological signals and should be set to one of the

appropriate values defined in Table 2.

— The same type waveforms should be described in a sequential, contiguous manner, and located

chronologically in the file.
Key
a EEG examination h frame #1 of waveform #1
b waveform (type #1) i frame #2 of waveform #1
c waveform (type #2) j header
d Explanation about neurophysiological signals k waveform data
e explanation (waveform class) l explanation about frame
f waveform #1 of type #1
g waveform #2 of type #1
Figure 2 — Waveform data configuration
5.3 Time synchronization

In EEG examination data, several types of neurophysiological signals and biomedical data, such

as SpO2 or respiration may be described together in the same MFER file, requiring support for time

© ISO 2021 – All rights reserved 3
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ISO/TS 22077-5:2021(E)

synchronization between the waveform streams and these parametric observations. In addition, it is

necessary to capture the state of the photic stimulator at the time the data was acquired.

NOTE For EEG examinations, photic stimulators are used to investigate anomalous brain activity triggered

by specific visual stimuli, such as flashing lights or other patterns.

The reference time used for synchronization starts counting from the beginning of the examination

period. The data recording system shall establish the reference time for each data point using the

recorded examination time. The reading system can then establish synchronization between data

points by correlating the acquisition time for each data point.

The reference time of waveforms such as EEGs are described using the pointer tag (MWF_PNT). The

reference time of events such as photic stimulator information (stimulator period, frequency, mode,

duration, etc.) is described using "starting time" item of the event tag (MWF_EVT). The reference time

of measurements such as heart rate and respiration rate are described using the "time point" item of

the value tag (MWF_VAL). Reference time is indicated as a data pointer that depends on the sampling

rate of the waveform frame. The waveform reader system may also achieve data synchronization using

pointers of different sampling rate.

For example, in Figure 3, if the sampling interval of a photic stimulator event is 1 second and the

sampling interval of EEG waveform is 1 ms, then the point of photic stimulator event becomes 60 s and

the point of EEG waveform becomes 60 000 samples at the time of the start of the photic stimulator.

4 © ISO 2021 – All rights reserved
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ISO/TS 22077-5:2021(E)
Key
1 Event information
tag: MWF_EVT
code:
starting time: 60 s
2 60 s
3 start of examination
4 stimulator begin
Figure 3 — Time synchronization
6 Waveform encoding
6.1 General
6.1.1 Application of EEG studies

This set of medical waveform format encoding rules (MFER) is aimed at ensuring that the waveforms

collected during EEG studies, including PSG examinations, are encoded together with the needed

contextual and descriptive information of the EEG examination. The waveforms recorded during EEG

studies include “full disclosure waveform” (i.e. comprehensive continuous waveform data covering

the entire period of the exam), and “intermittent record waveform” (i.e. waveform records in short

segments of particular interest during the exam). Intermittent waveforms are also commonly described

as, e.g. “one shot”, “window”, “snapshot”, “snippet”.
© ISO 2021 – All rights reserved 5
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ISO/TS 22077-5:2021(E)
6.1.2 Full disclosure waveforms

This form is used when encoding all EEG waveforms during examinations, including the resting period,

and the loading period such as photic stimulation. This not only includes encoding of waveform signals

from all leads used in the examination but also encoding of a subset of waveforms selected from multiple

leads. Note that for full disclosure waveform recording, encoding waveforms for the entire period of

the examination within one frame (see Figure 2) significantly reduces the MFER file complexity and

simplifies reading of the EEG content.

Encoding of full disclosure waveform shall be done in accordance with ISO 22077-1. The waveform class

of these waveforms include EEG_REST (40), EEG_EP (41), EEG_LTRM (43) and others.
6.1.3 Intermittent record waveforms

Intermittent recording of waveforms is used when encoding the waveforms of EEG, etc., using

interval records to capture shorter periods of interest during the examination such as resting, photic

stimulation, hyperventilation periods or one-shot records taken at random during the examination.

The point of time when the record concerned was taken during the test shall be encoded with using the

pointer tag (MWF_PNT).

For example, in Figure 4, if the sampling interval is 1 ms, then the point of information event (point #1)

becomes 600 s and the point of EEG waveform becomes 600 000 samples at the time of the start of the

examination.

Using the same sampling interval, the point of information event (point #2) becomes 900 s and the

point of EEG waveform becomes 9 000 000 samples at the time of the start of the examination.

6 © ISO 2021 – All rights reserved
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ISO/TS 22077-5:2021(E)
Key
1 600 s after examination starting
2 900 s after examination starting
3 sampling interval 1 ms
4 start of examination
Figure 4 — Intermittent record waveform
6.2 Waveform class
6.2.1 General

The waveform class indicates that this waveform data represents a neurophysiological signal.

Furthermore, the waveform class indicates the kind of waveform that is included in the MFER data. The

format is given in Table 1.
Table 1 — Waveform class
MWF_WFM Data length Default Remarks Duplicated definitions
2 Non-specific waveform — Override
08 08h
Str ≤ 32 Waveform description — Override
NOTE 1 See ISO 22077-1:2015, 5.1.3.
NOTE 2 See ISO 22077-1:2015, 4.3.3.2 and 4.3.3.3.
6.2.2 Waveform Class for EEG, PSG, EP, EMG
6.2.2.1 General
Each waveform class shall identify its Type based on Table 2 below.
© ISO 2021 – All rights reserved 7
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ISO/TS 22077-5:2021(E)
Table 2 — Classification of waveforms
Classification Type Value Description Remarks
Electrocardiography ECG_LTERM 2 Long-term ECG Holter ECG, monitoring ECG
Includes surgical monitoring
EEG_REST 40 Resting EEG
EEG
ABR
EEG_EP 41 Evoked EEG
SEP
Electroencephalography
EEG_CSA 42 Frequency analysis Reserved for future use.
(Neurophysiological signal)
EEG_LTRM 43 Long-term EEG Sleeping EEG
EMG 44 Electromyography —
EOG 45 Electrooculography —
Impedance resitatory, air-
Respiratory RESP 46 Respiratory
flow, Snore asnd others

NOTE 1 See ISO 22077-1:2015, section 5.1.3 [Waveform for general waveform type definitions (40) through (43)].

NOTE 2 EMG, EOG and RESP are uniquely defined in this document.

The following subsections provide additional detail for each of the waveforms identified in Table 2,

except those reserved for future use, such as EEG_CSA.
6.2.2.2 EEG_REST, EEG_LTRM

Electroencephalography (EEG) is a diagnostic technique recording the electrical activity of the

brain. Usually the electrodes are placed on the surface of the skull; special techniques use implanted

electrodes as well (see Annex B).

EEG data are used to diagnose epilepsy, to monitor encephalopathy, for anaesthesia and coma state

determination, and within sleep studies.

In clinical procedures, an EEG is typically is recorded for 20 minutes to 60 minutes using electrodes

placed on the patient’s scalp. Long term monitoring (e.g. to monitor epilepsy) may last from 6 hours to

several days. In both cases, video and audio recordings are often made as well.
Electrical potentials are in the range of 1 µV to 500 µV.

In sleep medicine, polysomnography (PSG), also called a “sleep study”, is an examination for diagnosing

sleep disorders. EEG data captured during PSG examin
...

TECHNICAL ISO/TS
SPECIFICATION 22077-5
First edition
Health informatics — Medical
waveform format —
Part 5:
Neurophysiological signals
PROOF/ÉPREUVE
Reference number
ISO/TS 22077-5:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TS 22077-5:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 22077-5:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 1

5 General ............................................................................................................................................................................................................................ 2

5.1 Overview of the rules ........................................................................................................................................................................ 2

5.2 Configuration of waveform data .............................................................................................................................................. 2

5.3 Time synchronization ....................................................................................................................................................................... 3

6 Waveform encoding ........................................................................................................................................................................................... 5

6.1 General ........................................................................................................................................................................................................... 5

6.1.1 Application of EEG studies ...................................................................................................................................... 5

6.1.2 Full disclosure waveforms ....................................................................................................................................... 5

6.1.3 Intermittent record waveforms .......................................................................................................................... 5

6.2 Waveform class ....................................................................................................................................................................................... 6

6.2.1 General...................................................................................................................................................................................... 6

6.2.2 Waveform Class for EEG, PSG, EP, EMG ......................................................................................................... 6

6.3 Waveform attributes (lead names) ........................................................................................................................................ 8

6.3.1 Waveform code .................................................................................................................................................................. 8

6.3.2 EEG ............................................................................................................................................................................................... 9

6.3.3 PSG, EOG, EMG, EP, RESP ........................................................................................................................................... 9

6.3.4 ECG ............................................................................................................................................................................................10

6.4 Sampling attributes ..........................................................................................................................................................................11

6.4.1 General...................................................................................................................................................................................11

6.4.2 MWF_IVL (0Bh): Sampling rate ........................................................................................................................11

6.4.3 MWF_SEN (0Ch): Sampling resolution ......................................................................................................12

6.5 Frame attributes .................................................................................................................................................................................12

6.6 Pointer .........................................................................................................................................................................................................12

6.7 Filter ..............................................................................................................................................................................................................13

7 Event information ............................................................................................................................................................................................13

7.1 General ........................................................................................................................................................................................................13

7.2 Measurement status – related events...............................................................................................................................14

Annex A (informative) MFER conformance statement ....................................................................................................................15

Annex B (informative) EEG electrode code .................................................................................................................................................17

Annex C (informative) Example of waveform encoding .................................................................................................................22

Bibliography .............................................................................................................................................................................................................................32

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO/TS 22077-5:2021(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 215, Health informatics.

A list of all parts in the ISO 22077 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 22077-5:2021(E)
Introduction

Neurophysiological signals are used to monitor and assess an individual’s brain activity for a wide array

of clinical examinations including sleep polysomnography (PSG), determination of brain death, evoked

potentials (EP), and electromyography (EMG).

Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical

activity of the brain. It is typically non-invasive, with multiple electrodes placed along the scalp (see

Figures B.1 and B.2). Diagnostic applications generally focus on the spectral content of EEG, that is, the

type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals. EEG

is most often used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to

diagnose sleep disorders, coma, encephalopathies, and brain death.

PSG examinations include monitoring the condition of the body during sleep at night. Confirmed diagnosis

of sleeping disorders and sleeping respiratory disorders is supported by recording neurophysiological

signals through electrodes. By measuring brain waves, eye movements, electromyogram movements,

etc., the depth of sleep (sleep stage), quality, presence or absence of midwake arousal, respiration by

breathing, snoring, oxygen saturation, etc., can be assessed.

To correctly interpret neurophysiological changes, medical device systems need to capture

these data, along with additional waveforms such as the respiration, SpO2, EOG (eye movement).

Healthcare providers and clinical specialists who perform these examinations greatly benefit from

interoperability – having all the examination data recorded in a single standardized package or file that

can be safely and securely managed and exchanged.

The purpose of this document is to describe the heterogeneous neurophysiological waveforms and

related data that can be normalized to a standard semantic representation and format and persisted

in a single package. The specification also supports the time synchronization of these waveforms and

related parametric data so that the clinician receiving the data package is able to better assess the

patient’s condition throughout the examination period.
About Medical waveform Format Encoding Rules (MFER)

The MFER standards address several challenges that are not limited to either EEG waveforms or the

neurophysiological assessments that are the main subject of this document:

— Simple and easy implementation: application of MFER is very simple and is designed to facilitate

understanding, easy installation, trouble-shooting, and low implementation cost.

— Using with other appropriate standards: it is recommended that MFER only describes

medical waveforms. Other information can be described using appropriate standards such as

1) 2) 3)

HL7® , DICOM® , IEEE® , etc. For example, clinical reports that include patient demographics,

order information, medication, etc. are supported in other standards such as HL7® Clinical

Document Architecture (CDA). By including references to MFER information in these documents,

implementation for message exchange, networking, database management that includes waveform

information becomes simple and easy.

— Separation between supplier and consumer of medical waveforms: the MFER specification

concentrates on data format instead of paper-based recording. For example, recorded ECG/EEG are

processed by filter, data alignment, and other parameters, so that the ECG waveform can be easily

displayed using an application viewer. However, it is not as useful for other purposes such as data

1) HL7 is the registered trademark of Health Level Seven International. This information is given for the convenience

of users of this document and does not constitute an endorsement by ISO of the product named.

2) DICOM is the registered trademark of the National Electrical Manufacturers Association for its standards

publications relating to digital communications of medical information. This information is given for the convenience

of users of this document and does not constitute an endorsement by ISO of the product named.

3) IEEE is a registered trademark of Institute of Electrical and Electronics Engineers, Inc. This information is given

for the convenience of users of this document and does not constitute an endorsement by ISO of the product named.

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processing for research investigations. A design goal of MFER is that a waveform is described in

raw format with as complete as possible recording detail. When the waveform is used, appropriate

processing of the data are supported like filtering, view alignment and so on. In this way, the medical

waveform described in MFER can be used for multiple purposes.

— Product capabilities are not limited: standards often support only a minimum set of requirements,

so the expansion of product features can be greatly limited. MFER can describe medical waveform

information without constraining the potential features of a product. Also, medical waveform

display must be very flexible, and thus MFER has mechanisms supporting not only a machine-

readable coded system for abstract data, but also human-readable representation.

The MFER specification supports both present and future product implementations. MFER supports the

translation of stored waveform data that was encoded using other standards, enabling harmonization

and interoperability. This capability supports not only existing waveform format standards but can be

extended to support future formats as well.
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TECHNICAL SPECIFICATION ISO/TS 22077-5:2021(E)
Health informatics — Medical waveform format —
Part 5:
Neurophysiological signals
1 Scope

This document specifies a heterogeneous format of neurophysiological waveform signals to support

recording in a single persistent record package as well as interoperable exchange. The document focuses

on electroencephalography (EEG) waveforms created during EEG examinations. Specific provision is

made for sleep polysomnography examinations (PSG), brain death determination, evoked potentials

(EP), and electromyography (EMG) studies.
This document is intended for neurophysiology.
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.

ISO 22077-1:2015, Health informatics — Medical waveform format — Part 1: Encoding rules

ISO/TS 22077-3:2015, Health informatics — Medical waveform format — Part 3: Long term

electrocardiography
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 22077-1:2015 apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Symbols and abbreviated terms
CO2 Carbon dioxide
DC Direct Current
DICOM Digital Imaging and Communication in Medicine
ECG Electrocardiography
EEG Electroencephalography
EMG Electromyography
EOG Electrooculography
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EP Evoked potentials
HPF High-frequency pass filter
IEEE Institute of Electrical and Electronic Engineers
LOINC® Logical Observation Identifiers Names and Codes
LPF Low-frequency pass filter
MFER Medical waveform Format Encoding Rules
PSG Polysomnography
SEP Somatosensory evoked potential
SNOMED-CT® Systematized Nomenclature of Medicine-Clinical Terms
SpO2 Saturation of peripheral oxygen

LOINC is the registered trademark of Regenstrief Institute, Inc. This information is given for the con-

venience of users of this document and does not constitute an endorsement by ISO of the product named.

NOMED CT is the registered trademark of the International Health Terminology Standards Develop-

ment Organisation (IHTSDO). This information is given for the convenience of users of this document

and does not constitute an endorsement by ISO of the product named.
5 General
5.1 Overview of the rules

All MFER content (see ISO 22077-1:2015, 4.2.2), including the file header and waveform data, should be

encoded based on the encoding rules that are composed of the tag, length and value (TLV), 3-tuple as

shown in Figure 1.
Figure 1 — Data unit

— The tag (T) consists of one or more octets and indicates the attribute of the data value.

— The data length (L) is the length of data values indicated in one or more octets.

— The value (V) is contents which are indicated by tag (T); e.g. attribute definition, waveform data, etc.

5.2 Configuration of waveform data

Medical waveform data described in accordance with the MFER is an aggregate of waveform frame data

that consists of a header section (encoding detailed information about the waveform) and a waveform

data section (main data of waveform). See Figure 2. The header and waveform data are encoded based

on the encoding rules that are composed of TLV (Tag - Data length - Value). One MFER waveform file can

include several waveforms. The content of an MFER waveform file is sequentially interpreted from the

beginning of the file, and a single file can contain multiple waveform definitions. Given the sequential

precedence processing for an MFER file, a waveform definition applies until another definition with the

same tag is encountered. In this case, the subsequent definition replaces the preceding definition for

the same waveform.
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Additionally, the definition for one waveform can be used, by reference, to define additional waveforms

in the MFER file. For example, a 60 channel EEG might only require four core waveform specifications,

with the other channels referring to the same definition, providing simplification of the overall file

complexity.

When there are several waveforms in a MFER waveform file, each waveform can be located anywhere in

the file; however, in the specification of data generated during EEG and other examinations, waveform

frames should be located as shown in Figure 2 to enhance usability and avoid erroneous interpretation:

— The information about EEG examination and others should be described before description of

waveform [i.e. in (a) and (d) content should be included before (e)]. For this document, the waveform

class definition(s) (MWF_WFM) are for neurophysiological signals and should be set to one of the

appropriate values defined in Table 2.

— The same type waveforms should be described in a sequential, contiguous manner, and located

chronologically in the file.
Key
a EEG examination h frame #1 of waveform #1
b waveform (type #1) i frame #2 of waveform #1
c waveform (type #2) j header
d Explanation about neurophysiological signals k waveform data
e explanation (waveform class) l explanation about frame
f waveform #1 of type #1
g waveform #2 of type #1
Figure 2 — Waveform data configuration
5.3 Time synchronization

In EEG examination data, several types of neurophysiological signals and biomedical data, such

as SpO2 or respiration may be described together in the same MFER file, requiring support for time

synchronization between the waveform streams and these parametric observations. In addition, it is

necessary to capture the state of the photic stimulator at the time the data was acquired.

NOTE For EEG examinations, photic stimulators are used to investigate anomalous brain activity triggered

by specific visual stimuli, such as flashing lights or other patterns.
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The reference time used for synchronization starts counting from the beginning of the examination

period. The data recording system shall establish the reference time for each data point using the

recorded examination time. The reading system can then establish synchronization between data

points by correlating the acquisition time for each data point.

The reference time of waveforms such as EEGs are described using the pointer tag (MWF_PNT). The

reference time of events such as photic stimulator information (stimulator period, frequency, mode,

duration, etc.) is described using "starting time" item of the event tag (MWF_EVT). The reference time

of measurements such as heart rate and respiration rate are described using the "time point" item of

the value tag (MWF_VAL). Reference time is indicated as a data pointer that depends on the sampling

rate of the waveform frame. The waveform reader system may also achieve data synchronization using

pointers of different sampling rate.

For example, in Figure 3, if the sampling interval of a photic stimulator event is 1 second and the

sampling interval of EEG waveform is 1 ms, then the point of photic stimulator event becomes 60 s and

the point of EEG waveform becomes 60 000 samples at the time of the start of the photic stimulator.

Key
1 Event information
tag: MWF_EVT
code:
starting time: 60 s
2 60 s
3 start of examination
4 stimulator begin
Figure 3 — Time synchronization
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6 Waveform encoding
6.1 General
6.1.1 Application of EEG studies

This set of medical waveform encoding rules (MFER) is aimed at ensuring that the waveforms collected

during EEG studies, including PSG examinations, are encoded together with the needed contextual and

descriptive information of the EEG examination. The waveforms recorded during EEG studies include

“full disclosure waveform” (i.e. comprehensive continuous waveform data covering the entire period of

the exam), and “intermittent record waveform” (i.e. waveform records in short segments of particular

interest during the exam). Intermittent waveforms are also commonly described as, e.g. “one shot”,

“window”, “snapshot”, “snippet”.
6.1.2 Full disclosure waveforms

This form is used when encoding all EEG waveforms during examinations, including the resting period,

and the loading period such as photic stimulation. This not only includes encoding of waveform signals

from all leads used in the examination but also encoding of a subset of waveforms selected from multiple

leads. Note that for full disclosure waveform recording, encoding waveforms for the entire period of

the examination within one frame (see Figure 2) significantly reduces the MFER file complexity and

simplifies reading of the EEG content.

Encoding of full disclosure waveform shall be done in accordance with ISO 22077-1. The waveform class

of these waveforms include EEG_REST (40), EEG_EP (41), EEG_LTRM (43) and others.
6.1.3 Intermittent record waveforms

Intermittent recording of waveforms is used when encoding the waveforms of EEG, etc., using

interval records to capture shorter periods of interest during the examination such as resting, photic

stimulation, hyperventilation periods or one-shot records taken at random during the examination.

The point of time when the record concerned was taken during the test shall be encoded with using the

pointer tag (MWF PNT).

For example, in Figure 4, if the sampling interval is 1 ms, then the point of information event (point #1)

becomes 600 s and the point of EEG waveform becomes 600 000 samples at the time of the start of the

examination.

Using the same sampling interval, the point of information event (point #2) becomes 900 s and the

point of EEG waveform becomes 9 000 000 samples at the time of the start of the examination.

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Key
1 600 s after examination starting
2 900 s after examination starting
3 sampling interval 1 ms
4 start of examination
Figure 4 — Intermittent record waveform
6.2 Waveform class
6.2.1 General

The waveform class indicates that this waveform data represents a neurophysiological signal.

Furthermore, the waveform class indicates the kind of waveform that is included in the MFER data. The

format is given in Table 1.
Table 1 — Waveform class
MWF_WFM Data length Default Remarks Duplicated definitions
2 Non-specific waveform — Override
08 08h
Str ≤ 32 Waveform description — Override
NOTE 1 See ISO 22077-1:2015, 5.1.3.
NOTE 2 See ISO 22077-1:2015, 4.3.3.2 and 4.3.3.3.
6.2.2 Waveform Class for EEG, PSG, EP, EMG
6.2.2.1 General
Each waveform class shall identify its Type based on Table 2 below.
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Table 2 — Classification of waveforms
Classification Type Value Description Remarks
Electrocardiography ECG_LTERM 2 Long-term ECG Holter ECG, monitoring ECG
Includes surgical monitoring
EEG_REST 40 Resting EEG
EEG
ABR
EEG_EP 41 Evoked EEG
SEP
Electroencephalography
EEG_CSA 42 Frequency analysis Reserved for future use.
(Neurophysiological signal)
EEG_LTRM 43 Long-term EEG Sleeping EEG
EMG 44 Electromyography —
EOG 45 Electrooculography —
Impedance resitatory, air-
Respiratory RESP 46 Respiratory
flow, Snore asnd others

NOTE 1 See ISO 22077-1:2015, section 5.1.3 [Waveform for general waveform type definitions (40) through (43)].

NOTE 2 EMG, EOG and RESP are uniquely defined in this document.

The following subsections provide additional detail for each of the waveforms identified in Table 2,

except those reserved for future use, such as EEG_CSA.
6.2.2.2 EEG_REST, EEG_LTRM

Electroencephalography (EEG) is a diagnostic technique recording the electrical activity of the

brain. Usually the electrodes are placed on the surface of the skull; special techniques use implanted

electrodes as well (see Annex B).

EEG data are used to diagnose epilepsy, to monitor encephalopathy, for anaesthesia and coma state

determination, and within sleep studies.

In clinical procedures, an EEG is typically is recorded for 20 minutes to 60 minutes using electrodes

placed on the patient’s scalp. Long term monitoring (e.g. to monitor epilepsy) may last from 6 hours to

several days. In both cases, video and audio recordings are often made as well.
Electrical potentials are in the range of 1 µV to 500 µV.

In sleep medicine, polysomnography (PSG), also called a “sleep study”, is an examination for diagnosing

sleep disorders. EEG data captured during PSG examinations are used as the primary indicator for

sleep stages, arousal, and wakefulness, but it is also used to aid in the diagnosis of

...

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