ISO/TS 11073-92001:2007
(Main)Health informatics — Medical waveform format — Part 92001: Encoding rules
Health informatics — Medical waveform format — Part 92001: Encoding rules
ISO/TS 11073-92001:2007 specifies how medical waveforms, such as electrocardiogram, electroencephalogram, spirometry waveform etc., are described for interoperability among healthcare information systems. ISO/TS 11073-92001:2007 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. ISO/TS 11073-92001:2007 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 — Forme d'onde médicale — Partie 92001: Règles d'encodage
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Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 11073-92001
First edition
2007-09-01
Health informatics — Medical waveform
format —
Part 92001:
Encoding rules
Informatique de santé — Forme d'onde médicale —
Partie 92001: Règles d'encodage
Reference number
ISO/TS 11073-92001:2007(E)
©
ISO 2007
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ISO/TS 11073-92001:2007(E)
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ISO/TS 11073-92001:2007(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) .21
7 Extended description (Level 3).24
Annex A (informative) MFER conformance statement .27
Annex B (informative) Description example.28
Annex C (informative) Event information description.35
Annex D (informative) Example of standard encoding.36
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ISO/TS 11073-92001:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee
casting a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 11073-92001 was prepared by Technical Committee ISO/TC 215, Health informatics.
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ISO/TS 11073-92001:2007(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: MEFR 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. ART (arterial blood pressure) 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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TECHNICAL SPECIFICATION ISO/TS 11073-92001:2007(E)
Health informatics — Medical waveform format —
Part 92001:
Encoding rules
1 Scope
This Technical Specification specifies how medical waveforms, such as electrocardiogram,
electroencephalogram, spirometry waveform, etc., are described for interoperability among healthcare
information systems.
This Technical Specification 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 Technical Specification 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
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ISO/TS 11073-92001:2007(E)
CEN Comité Européen de Normalisation/European Committee for Standardization
ECG Electrocardiogram
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
SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (EN 1064)
SPO2 Saturation of Peripheral Oxygen
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/TS 11073-92001:2007(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 3.
c) Sequence
The sequence represents the repetition of the group with the data block and channel.
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ISO/TS 11073-92001:2007(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) is 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/TS 11073-92001:2007(E)
Table 1 — Tag
8 7 6 5 4 3 2 1
Class P/C Tag number
0 0
MFER
0 1
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.
8 7 6 5 4 3 2 1
0 1 1 0 0 1 1 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 is 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.
8 7 6 5 4 3 2 1
0 Data length
Figure 5 — Data length u 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.
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
Length number
1 Most significant octet The second octet The third octet
(e.g. 3 octets)
Figure 6 — Data length
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ISO/TS 11073-92001:2007(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 privacy, security, etc.; 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), may 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 examples, 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/TS 11073-92001:2007(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.
1) MWF_IVL (0Bh): Sampling rate
This tag indicates the frequency or interval the medical waveform is sampled (Table 2).
Table 2 — Sampling rate
MWF_IVL * Data length Default Encoding range/remarks Duplicated definitions
Unit 1 —
th −128 +127
11 0Bh 1 000 Hz Override
Exponent (10 power) 1 10 to 10
Mantissa u 4 e.g. signed 16-bit 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 —
2) 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
MWF_SEN * Data length Default Encoding range/remarks Duplicated definitions
Unit 1 —
th −128 +127
12 0Ch See Table 5 Override
Exponent (10power) 1 10 to 10
Mantissa u 4 e.g. signed 16-bit integer
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Table 5 — Sampling units
Unit Value Default Remarks
Voltage V 0 0,000 001 V —
mm Hg(Torr) 1 — —
Pa 2 — —
Pressure
cm HO 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.
1) 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 u 4 1 — Override
2) 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/TS 11073-92001:2007(E)
Table 7 — Number of channels
MWF_CHN* Data length Default Remarks Duplicated definitions
05 05h u 4 1 — Override
3) 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
06 06h u 4 Depends on waveform data length — Override
5.1.3 Waveform
The waveform type, waveform attributes and waveform data are encoded as follows.
1) 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 u 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 49151 (BFFFh) are already reserved. Numbers 49152 to
65535 may be used privately but it should be documented in the MFER specification as quickly as possible if
the waveform is commonly used.
2) 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 49151 (BFFFh) are already reserved. Numbers 49152 to 65535 may be
used privately but should be used for new types of waveforms by upgrading the MFER promptly.
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ISO/TS 11073-92001:2007(E)
Table 10 — Classification of waveforms
Classification Type Value Description Reference Remarks
— — 0 Unidentified — —
Different kinds of 12 lead
ECG_STD12 1 Standard 12 lead ECG Part 3-1 ECGs including general
ECGs can be encoded
ECG_LTERM 2 Long-term ECG Part 3-2 Holter ECG, monitoring ECG
ECG_VECTR 3 Vectorcardiogram Part 3-5 —
ECG_EXCER 4 Stress ECG Part 3-3 —
His bundle ECG,
intracardiac ECG,
ECG_INTR 5 Intracardiac ECG Part 3-4
Electrocardiogram
intravascular ECG, cardiac
surface ECG
Body surface potential map
ECG_SURF 6 Body surface ECG Part 3-5
Body surface
His bundle ECG
Ventricular late
ECG_ILATE 7 Part 3-5 —
potential
Body surface late
ECG_
...
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