ISO 22077-1:2015
(Main)Health informatics — Medical waveform format — Part 1: Encoding rules
Health informatics — Medical waveform format — Part 1: Encoding rules
ISO 22077-1:2015 specifies how medical waveforms, such as electrocardiogram, electroencephalogram, spirometry waveform, etc., are described for interoperability among healthcare information systems. This International Standard may be used with other relevant protocols, such as HL7, DICOM, ISO/IEEE 11073, and database management systems for each purpose. This is a general specification, so specifications for particular waveform types and for harmonization with DICOM, SCP-ECG, X73, etc. are not given. This International Standard does not include lower layer protocols for message exchange. For example, a critical real-time application like a patient monitoring system is out of scope and this is an implementation issue.
Informatique de santé — Format de la forme d'onde médicale — Partie 1: Règles d'encodage
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 22077-1
First edition
2015-04-01
Health informatics — Medical
waveform format —
Part 1:
Encoding rules
Informatique de santé — Format de la forme d’onde médicale —
Partie 1: Règles d’encodage
Reference number
ISO 22077-1:2015(E)
©
ISO 2015
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ISO 22077-1:2015(E)
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ISO 22077-1:2015(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Abbreviated terms . 1
4 Basic specifications . 2
4.1 Basic attributes . 2
4.1.1 General. 2
4.1.2 Sampling attributes . 2
4.1.3 Frame attributes . 3
4.2 Encoding rule . 4
4.2.1 General. 4
4.2.2 Tag (T) . 4
4.2.3 Data length (L) . 5
4.2.4 Value (V) . 6
4.3 Encoding principle . 6
4.3.1 General. 6
4.3.2 Definition levels . 6
4.3.3 General principles in interpretation, scope and priority of definitions . 6
5 Basic rules (Level 1) . 8
5.1 Primary description. 8
5.1.1 Sampling attributes . 8
5.1.2 Frame attributes . 9
5.1.3 Waveform .10
5.1.4 Channel .13
5.2 Auxiliary rule .14
5.2.1 Data description .14
5.2.2 Other definition .16
5.2.3 Information description .17
6 Supplemental description (Level 2) .22
7 Extended description (Level 3) .24
Annex A (informative) MFER conformance statement .27
Annex B (informative) Description example .29
Annex C (informative) Event information description .36
Annex D (informative) Example of standard encoding.38
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ISO 22077-1:2015(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
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For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 215, Health Informatics.
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ISO 22077-1:2015(E)
Introduction
Medical waveform data such as an electrocardiogram (ECG) or an electroencephalogram (EEG) are
widely utilized in physiological examinations, physiological research, electronic medical records,
healthcare information, and other areas in the clinical field. Medical waveform data can be used for
many medical and research purposes if digital signal processing technology is applied to standardize
the data in a digital format. For medical waveforms, it is essential to standardize the data format to
expedite the mutual application of the standard so that the data can be processed electronically and
used in a variety of ways.
Simple and easy implementation: application of medical waveform format encoding rules (MFER)
is very simple and is designed to facilitate understanding, easy installation, trouble-shooting, and low
implementation cost.
Harmonization with other standards: MFER is specially utilized to describe the medical waveform
data. Other information than waveform data, such as patient demographic data and finding information,
etc. should be written using other healthcare standards, such as HL7, DICOM, ISO/IEEE 11073.
In addition, experts in each field should independently develop relevant standards for medical
specifications; for example MFER for ECG is developed by cardiologists and EEG is developed by
neurologists.
Combination with coded information and text information: MFER policy is that both machine and
human readable manner are used. Namely coded information is for computer processable and text data
are for human readable information. Arterial blood pressure (ART) is coded as 129 and information
description fields indicate “Right radial artery pressure”, for example. As the description of MFER is quite
flexible, MFER neither hinders the features of each system nor impedes the development of technologies.
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INTERNATIONAL STANDARD ISO 22077-1:2015(E)
Health informatics — Medical waveform format —
Part 1:
Encoding rules
1 Scope
This International Standard specifies how medical waveforms, such as electrocardiogram,
electroencephalogram, spirometry waveform, etc., are described for interoperability among healthcare
information systems.
This International Standard may be used with other relevant protocols, such as HL7, DICOM,
ISO/IEEE 11073, and database management systems for each purpose.
This is a general specification, so specifications for particular waveform types and for harmonization
with DICOM, SCP-ECG, X73, etc. are not given.
This International Standard does not include lower layer protocols for message exchange. For
example, a critical real-time application like a patient monitoring system is out of scope and this is an
implementation issue.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
frame
waveform encoding unit consisting of data blocks, channels, and sequences
2.2
medical waveform
time sequential data that are sampled by A/D converter or transmitted from medical equipment
2.3
sampling
data that are converted at a fixed time interval
2.4
channel
individual waveform data group
3 Abbreviated terms
AAMI Association for the Advancement of Medical Instrumentation
A/D Analog to Digital
CSE Common Standards for Quantitative Electrocardiography
CEN Comité Européen de Normalization/European Committee for Standardization
ECG Electrocardiogram
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ISO 22077-1:2015(E)
EEG Electroencephalogram
GPS Global Positioning System
HL7 Health Level Seven
DICOM Digital Imaging and Communications in Medicine
IEEE Institute of Electrical and Electronic Engineers
IEC International Electrotechnical Commission
JIS Japanese Industrial Standard
LSB Least significant bit
MFER Medical waveform Format Encoding Rules
MSB Most significant bit
OID Reference to the ISO standard.
SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (EN 1064)
SPO Saturation of Peripheral Oxygen
2
UID Reference to the ISO standard
UUID Reference to the ISO standard
VCG Vectorcardiogram
4 Basic specifications
4.1 Basic attributes
4.1.1 General
Medical waveform data described in accordance with the MFER consists of Sampling attributes
(Figure 1), Frame attributes (Figure 2) and other supplemental information.
4.1.2 Sampling attributes
Sampling information has two attributes, sampling rate and sampling resolution.
a) sampling rate
The sampling rate is described with sampling interval or sampling frequency. The sampling interval
stands for the time or distance interval of each sampled data as distributed sampled waveform data.
b) sampling resolution
Sampling resolution represents a minimum sampling value per least significant bit (LSB).
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ISO 22077-1:2015(E)
Key
T sampling interval (or frequency)
R resolution
Figure 1 — Sampling attributes
4.1.3 Frame attributes
The frame is a waveform encoding unit consisting of data blocks, channels, and sequences. A configuration
example of a frame is shown as Figure 2.
a) data block
The data block is the waveform data array for each channel.
b) channels
The channels indicate different waveform groups, e.g. if three waveform groups exist, the number of
channels is three.
c) sequence
The sequence represents the repetition of the group with the data block and channel.
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ISO 22077-1:2015(E)
Key
1 frame
2 data block
3 channel
4 sequence
Figure 2 — Frame attributes
4.2 Encoding rule
4.2.1 General
The header and waveform data should be encoded based on the encoding rules which are composed of
the tag, length and value (TLV), as shown in Figure 3.
Tag (T)Data length (L)Value (V)
Figure 3 — 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) are the contents which are indicated by tag (T); e.g. attribute definition, waveform
data, etc.
4.2.2 Tag (T)
The tag is composed of a class, primitive/context (P/C) and tag number. The tag is classified into four
classes (Table 1). Classes 0 to 2 are MFER standard coding and class 3 is for private use. The private
definition is intended for special purposes but should be included within any updated future version.
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ISO 22077-1:2015(E)
Table 1 — Tag
8 7 6 5 4 3 2 1
Class P/C Tag number
0 0
0 1 MFER
0/1
1 0
1 1 Private
a) primitive type (P/C = 0).
P/C = 0 indicates a primitive description.
b) context type (P/C = 1).
This has only two tags which are group and channel definition on current MFER. Figure 4 gives an
example of a group definition.
876 5432 1
1
01 0011 1
Figure 4 — Group definition
4.2.3 Data length (L)
The data length indicates the number of octets used for data values in the value (V) section (i.e. the
length excluding octets used for tag and data length sections). The data length encoding method differs
depending on whether the number of octets used for data are less than 127 or more than 128 octets.
a) In case the data value section uses 127 octets or less.
The length is encoded in one octet, as shown in Figure 5.
876 5432 1
0Data length
Figure 5 — Data length ≤ 127 octets
b) In case the data value section uses 128 octets or more.
The long data length can be encoded using multiple octets. The first octet indicates the number of octets
used to represent the total data length. For example, two subsequent octets are used to indicate the
waveform data length from 128 to 65 535 and thus three octets are used to encode the data length as in
Figure 6. However, MFER allows representation of a data length using multiple octets even if the length is
less than 127 octets. For example, four octets can describe up to 4 294 967 295 bytes length as a data part.
87 654 32 187 65 43 218 76 543 21 87 654 32 1
Length number
1 Most signi icant octetThe second octetThe third octet
(e.g. 3octets)
Figure 6 — Data length
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ISO 22077-1:2015(E)
c) Designation of indefinite data length.
MFER allows designation of an indefinite data length by encoding 80 h on the top of the data length field
(Figure 7). This indefinite length designation is terminated by encoding the end-of-contents (tag = 00,
data length = 00).
Tag Length End-of-Contents
----- ----- -----
P/C=1 (80h) (00,00)
Figure 7 — Indefinite length designation and end-of-contents designation
d) In case the data length is 0.
MFER indicates that the definition indicated by tag resets to the default value. Namely, on the root
definition the concerned items re-initialize to default values and in case of the channel definition, the
channel definition is re-initialized to the root definition.
4.2.4 Value (V)
The header or waveform data values are encoded in the value section according to descriptors
specified by the tag.
4.3 Encoding principle
4.3.1 General
All definitions in MFER have default values, so any additional or amended definitions are optional. Thus
the definition corresponding to each tag has a default value, so re-definition is not necessary if the
default value is retained. It is expected that default definitions will suffice for most purposes.
4.3.2 Definition levels
4.3.2.1 Level 1 — basic definitions
Definitions at level 1 are basic definitions, which are ordinary rules (marked with an asterisk) and
ensure precise encoding.
4.3.2.2 Level 2 — supplementary definitions
Definitions at level 2 are supplementary definitions. They may be used as required but it is desirable
to associate the supplementary definitions with a host protocol where they can be defined with the
host protocol.
4.3.2.3 Level 3 — extended definitions
Definitions at level 3 are extended definitions, which should be used as little as possible. Items of these
extended definitions may considerably affect the system with regard to security. Thus, great care should
be taken in using them.
4.3.3 General principles in interpretation, scope and priority of definitions
4.3.3.1 Initial values (default value)
All definitions in MFER have initial values that are applied until redefined by any subsequent definition.
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4.3.3.2 Multiple definitions
Multiple definitions may be made for any item. Depending on items, a new definition, an old definition,
or all definitions (such as for events), can be used multiple times.
For example, setting the sampling frequency to 250 Hz overrides the initial value of 1 kHz.
If multiple events occur, they are interpreted in definition order.
4.3.3.3 Later definition priority
Each definition is interpreted in definition order. If an item has related definitions, definition should be
made in due order. The default endianity is big-endian, so to use little-endian endianity the definition for
little-endian must be designated.
For example, before defining each channel, the number of channels should be defined.
4.3.3.4 Channel attributes definition order
Before defining the attributes of a channel, the number of channels should be defined. If the number of
channels is defined later, previous channel definitions are reset to the root definition including default values.
4.3.3.5 Root definition (general definition) and channel definition (definition per channel)
The root definition is effective for all channels. The channel definition is effective only for the relevant
channel and overrides the root definition. However, care should be taken because if a subsequent change
to the root definition is made, it will override the default content of the relevant channel for subsequent
channel definitions.
For example, if EEG is designated in the root definition, ECG designated for a channel in the channel
definition overrides EEG.
4.3.3.6 Definition reset
If the data length is defined as zero (no data) in the definition of an item, the content in the definition
is reset to default value. If the data length is designated as zero in a channel definition, the definition
follows the root definition including the default value. If the number of channels is defined, contents
defined for the channel attribute are all reset to the root definition including the default value.
4.3.3.7 Incomplete definition ignored
If a definition is made without an adequate preceding definition, the definition is ignored.
In the absence of any complete definition, the default root definition will be applied.
For example, if the number of channels is undefined, any dependent channel definition is ignored.
4.3.3.8 Succession of definitions
Unless redefined, each definition applies to all succeeding frames, in the effective range, except for the
data pointer which is succeeding renewed. Thus, contents defined in the root definition apply to all frames
unless overridden by channel definition(s), so it suffices to define common items in the root definition.
For example, to use little-endian for all encodings with MFER, define little-endian once, then it is effective
over the whole region irrespective of frames.
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ISO 22077-1:2015(E)
4.3.3.9 Definition and efficacy of data
It depends on the functional capability of the user application whether or not the user can use data
defined by the provider. If some content cannot be processed, users may discard all the data or use only
the processable range of data.
5 Basic rules (Level 1)
5.1 Primary description
5.1.1 Sampling attributes
Sampling attributes are sampling frequency or sampling interval and resolution are given in Tables 2 to 5.
a) MWF_IVL (0Bh): Sampling rate
This tag indicates the frequency or interval the medical waveform is sampled (Table 2).
Table 2 — Sampling rate
Data Encoding range/ Duplicated defini-
MWF_IVL* Default
length remarks tions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
11 0Bh 1 000 Hz Override
e.g. unsigned 16-bit
Mantissa ≤4
integer
The unit may be frequency in Hertz, time in seconds or distance metres (Table 3).
Table 3 — Sampling rate unit
Unit Value Remarks
Frequency Hz 0 Including power
Time interval s 1 —
Distance m 2 —
b) MWF_SEN (0Ch): Sampling resolution
This tag indicates the resolution, minimum bits, the medical waveform is sampled (generally,
digitized) (Table 4).
Table 4 — Sampling resolution
Data Encoding range/ Duplicated defini-
MWF_SEN* Default
length remarks tions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
12 0Ch see Table 5 Override
e.g. unsigned 16-bit
Mantissa ≤4
integer
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ISO 22077-1:2015(E)
Table 5 — Sampling resolution units
Unit Value Default Remarks
Voltage V 0 0,000 001 V —
mm Hg(Torr) 1 — —
Pa 2 — —
Pressure
cm H O 3 — —
2
mm Hg/s 4 — —
dyne 5 — —
Force
N 6 — —
Ratio % 7 — Include volume fraction (%)
Temperature °C 8 — —
−1
min 9 — —
Heart rate
−1
s 10 — —
Resistance Ω 11 — —
Current A 12 — —
Rotation r/min 13 — —
W 14 — —
Power
dB 15 — —
Mass kg 16 — —
Work J 17 — —
−2 −5
Vascular resistance dyne ⋅ s ⋅ m cm 18 — —
l 19 — —
Flow rate, flow, volume l/s 20 — —
l/min 21 — —
Luminous intensity cd 22 — —
5.1.2 Frame attributes
As described in Figure 2 a frame is composed of data blocks, channels and sequences.
a) MWF_BLK (04h): Data block length
This tag indicates the number of data sampled in a block (Table 6).
Table 6 — Data block length
MWF_BLK* Data length Default Remarks Duplicated definitions
04 04h ≤ 4 1 — Override
b) MWF_CHN (05h): Number of channels
This tag indicates the number of channels (Table 7). As the previously specified channel attribute is
reset to the root definition including default, the number of channels should be specified before each
definition of the channel attribute. The number of channels cannot be specified with a channel definition
of channel attribute.
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ISO 22077-1:2015(E)
Table 7 — Number of channels
MWF_CHN* Data length Default Remarks Duplicated definitions
05 05h ≤4 1 — Override
c) MWF_SEQ (06h): Number of sequences
This tag indicates the number of sequences (Table 8). If the number of sequences is not designated, it
depends on the data block length, the number of channels and the number of waveform data values
which are defined for the concerned frame.
Table 8 — Number of sequences
MWF_SEQ* Data length Default Remarks Duplicated definitions
Depends on waveform data
06 06h ≤ 4 — Override
length
5.1.3 Waveform
The waveform type, waveform attributes, and waveform data are encoded as follows.
a) MWF_WFM (08h): Waveform class
Waveforms such as standard 12-lead ECG and monitoring ECG are grouped based on instruments and
purposes, as shown in Table 9.
Table 9 — Waveform class
MWF_WFM* Data length Default Remarks Duplicated definitions
2 Non-specific waveform —
08 08h Override
Str ≤ 32 Waveform description —
As a general rule, standardization will be made by type of waveforms, each is described in a separate
specification (e.g. for standard 12-lead ECG 11073-92301). However, because monitoring systems
use multiple waveforms such as ECG, SpO2, EEG, etc., refer to the specification for each individual
waveform standard.
For types of waveform (Table 10), numbers 1 to 49 151 (BFFFh) are already reserved. Numbers 49 152
to 65 535 can be used privately but it should be documented in the MFER specification as quickly as
possible if the waveform is commonly used.
b) MWF_LDN (09h): Waveform attributes (lead name, etc.)
Code and information can be added to the type of waveform. If a waveform is required to be reconfigured,
as in the case of deriving leads III and aVF from leads I and II, the codes should always be specified. The
codes should be taken into special consideration as they have a function to specify some processing,
as in the case of deriving other limb leads from leads I and II or deriving a waveform based on the lead
name. See Table 11 for the definition of waveform attributes.
As the lead names are defined depending on the class of waveform, they are not consolidated throughout
each class of waveform in MFER. Thus, caution should be taken in encoding lead names.
For waveform codes, numbers 1 to 49 151 (BFFFh) are already reserved. Numbers 49 152 to 65 535 can
be used privately but should be used for new types of waveforms by upgrading the MFER promptly.
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ISO 22077-1:2015(E)
Table 10 — Classification of waveforms
Classification Type Value Description Remarks
— — 0 Unidentified —
Different kinds of 12 lead
ECG_STD12 1 Standard 12 lead ECG ECGs including general ECGs
can be encoded
ECG_LTERM 2 Long-term ECG Holter ECG, monitoring ECG
ECG_VECTR 3 Vectorcardiogram —
ECG_EXCER 4 Stress ECG —
His bundle ECG, intracardiac
ECG_INTR 5 Intracardiac ECG ECG, intravascular ECG, car-
Electrocardiogram
diac surface ECG
Body surface potential map
ECG_SURF 6 Body surface ECG
Body surface
His bundle ECG
Ventricular late poten-
ECG_ILATE 7 —
tial
Body surface late poten-
ECG_LATE 8 —
tial
Sound SOUND 30 PCG, etc. 8 kHz, 11 kHz, 22 kHz, etc.
Fingertip pulse, carotid
Pulse PULSE 31 —
pulse
MON_LTRM 20 Long-term waveform —
MON_SPL 21 Sampled waveform —
Monitoring
MON_PWR 25 Power spectrum Some part is EEG_CSA
MON_TRD 26 Trendgram —
Magnetocardiogram 100 MCG —
Includes surgical mon
...
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