IEC 61846:1998

INTERNATIONAL IEC
STANDARD 61846
First edition
1998-04
Ultrasonics –
Pressure pulse lithotripters –
Characteristics of fields
Ultrasons –
Lithotripteurs à ondes de pression –
Caractérisation des champs
Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are
available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base
publication incorporating amendments 1 and 2.
Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken by
the technical committee which has prepared this publication, as well as the list of
publications issued, is to be found at the following IEC sources:
• IEC web site*
• Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.

INTERNATIONAL IEC
STANDARD 61846
First edition
1998-04
Ultrasonics –
Pressure pulse lithotripters –
Characteristics of fields
Ultrasons –
Lithotripteurs à ondes de pression –
Caractérisation des champs
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For price, see current catalogue

– 2 – 61846 © IEC:1998(E)
CONTENTS
Page
FOREWORD . 3
INTRODUCTION . 4
Clause
1 Scope. 5
2 Normative references. 5
3 Definitions. 6
4 List of symbols. 10
5 Conditions of measurement . 10
6 Test equipment. 11
6.1 Test chamber. 11
6.2 Hydrophone . 11
6.3 Voltage measurement . 12
7 Measurement procedure. 12
7.1 Spatial measurements . 12
7.2 Temporal measurements . 14
7.3 Acoustic energy measurements. 14
Annexes
A Acoustic wave lithotripsy. 16
B Types of pressure wave transducers . 18
C Field measurement . 20
D Bibliography. 25

61846 © IEC:1998(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ULTRASONICS –
PRESSURE PULSE LITHOTRIPTERS –
CHARACTERISTICS OF FIELDS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61846 has been prepared by IEC technical committee 87:
Ultrasonics.
The text of this standard is based on the following documents:
FDIS Report on voting
87/115/FDIS 87/118/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annexes A, B, C and D are for information only.
In this standard, the following print types are used:
– requirements and definitions: in roman type;
– NOTES: in smaller roman type;
– compliance: in italic type;
– terms used throughout this standard which have been defined in clause 3: small case
roman bold type.
A bilingual version of this standard may be issued at a later date.

– 4 – 61846 © IEC:1998(E)
INTRODUCTION
Extracorporeal lithotripsy is used for the clinical treatment of renal, ureteric and biliary stones.
Lithotripsy employs high-intensity acoustic waves to produce disintegration of the stones
through a process of sequential application of pressure waves. Several different forms of
lithotripsy equipment are now commercially available from a number of manufacturers.
This International Standard specifies methods of measuring and characterizing the acoustic
pressure field generated by lithotripsy equipment.

61846 © IEC:1998(E) – 5 –
ULTRASONICS –
PRESSURE PULSE LITHOTRIPTERS –
CHARACTERISTICS OF FIELDS
1 Scope
This International Standard is applicable to
– lithotripsy equipment using extracorporeally induced pressure waves;
– lithotripsy equipment producing focused mechanical energy.
This International Standard does not apply to percutaneous and laser lithotripsy equipment.
This International Standard specifies
– measurable parameters which could be used in the declaration of the acoustic output of
extracorporeal lithotripsy equipment,
– methods of measurement and characterization of the pressure field generated by
lithotripsy equipment.
NOTE – The parameters defined in this International Standard do not – at the present time – allow quantitative
statements to be made about effectiveness and possible hazard. In particular, it is not possible to make a
statement about the limits for these effects.
While this particular standard has been developed for equipment intended for use in
lithotripsy, it has been developed such that, as long as no other specific standards are
available to be used for other medical applications of therapeutic extracorporeal pressure
pulse equipment, this standard may be used as a guideline.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. At the time of publication, the editions
indicated were valid. All normative documents are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) – Chapter 801: Acoustics
and electroacoustics
IEC 60866:1987, Characteristics and calibration of hydrophones for operation in the frequency
range 0,5 MHz to 15 MHz
IEC 61102:1991, Measurement and characterisation of ultrasonic fields using hydrophones in
the frequency range 0,5 MHz to 15 MHz

– 6 – 61846 © IEC:1998(E)
3 Definitions
For the purpose of this International Standard, the following definitions apply.
3.1 acoustic pulse energy
3.1.1
derived acoustic pulse energy
spatial integral of the derived pulse-intensity integral over a circular cross-sectional area of
radius R in the x-y plane which contains the focus
Symbol: E
R
Unit: joule, J
3.1.2
derived focal acoustic pulse energy
spatial integral of the derived pulse-intensity integral over the focal cross-sectional area
Symbol: E
f
Unit: joule, J
NOTE – This definition may overestimate E if the aperture of the pressure pulse generator is large.
3.2
beam axis
line passing through the geometric centre of the aperture of the pressure pulse generator and
the focus
NOTE – This line is taken as the z axis. See 6.1 and clause 7.
3.3
compressional pulse duration
time interval beginning at the first time the instantaneous acoustic pressure exceeds 50 % of
the peak-positive acoustic pressure and ending at the next time the instantaneous
acoustic pressure has that value (see figure C.1)
Symbol: t
FWHMp+
Unit: second, s
NOTE – The subscript "FWHM" stands for "full width, half maximum".
3.4
derived pulse-intensity integral
time integral of the instantaneous intensity at a particular point in a pressure pulse field over
the (see 3.31 of IEC 61102)
pressure pulse waveform
Symbol: PII
Unit: joule per metre squared, J/m
3.5
end-of-cable loaded sensitivity of a hydrophone
ratio of the voltage at the end of any integral cable or connector of a hydrophone, when
connected to a specified electrical input impedance, to the instantaneous acoustic pressure
in the undisturbed free field of a plane wave in the position of the acoustic centre of the
hydrophone if the hydrophone were removed (see 3.14 of IEC 61102)
Symbol: M
L
–1
Unit: volt per pascal, V Pa
61846 © IEC:1998(E) – 7 –
3.6
focal cross-sectional area
area of the peak-compressional acoustic pressure contour which is –6 dB relative to the
value at the focus and is in the plane, perpendicular to the beam axis, which contains the
focus
Symbol: A
f
Unit: metre squared, m
3.7
focal extent
shortest distance along the z axis that connects points on the –6 dB contour of peak-positive
acoustic pressure in the x-z plane on either side of the focus
Symbol: f
z
Unit: metre, m
3.8
focal volume
volume in space contained within the surface defined by the –6 dB (relative to the value at the
focus) peak-compressional acoustic pressure contours measured around the focus
Symbol: V
f
Unit: metre cubed, m
NOTE – It is difficult to measure –6 dB points throughout the volume around the focus. It is reasonable in practice
to approximate the focal volume from measurements taken in three orthogonal directions: the beam axis (z axis);
the direction of maximum beam diameter (x axis); the axis perpendicular to the x axis (y axis).
3.9
focal width, maximum
maximum width of the –6 dB contour of p around the focus in the x-y plane which contains
+
the focus
Symbol: f
x
Unit: metre, m
3.10
focal width, orthogonal
width of the –6 dB contour of p around the focus, in the x-y plane which contains the focus,
+
in the direction perpendicular to f
x
Symbol: f
y
Unit: metre, m
3.11
focus
location in the pressure pulse field of the maximum peak-positive acoustic pressure
3.12
hydrophone
transducer that produces electrical signals in response to waterborne acoustic signals
[IEV 801-32-26] (see also IEC 60866)

– 8 – 61846 © IEC:1998(E)
3.13
instantaneous acoustic pressure
pressure minus the ambient pressure at a particular instant in time and at a particular point in
an acoustic field (see also 801-21-19 of IEC 60050(801))
Symbol: p
Unit: pascal, Pa
3.14
instantaneous intensity
acoustic energy transmitted per unit time in the direction of acoustic wave propagation per unit
area normal to this direction at a particular instant in time and at a particular point in an
acoustic field
For measurement purposes referred to in this standard, where far-field conditions may be
assumed, the instantaneous intensity, I, is expressed as:
p
I =
Z
where
p is the instantaneous acoustic pressure;
Z is the characteristic acoustic impedance of the medium.
(See also 3.21 of IEC 61102.)
Symbol: I
Unit: watt per metre squared, W/m
3.15
lithotripsy equipment
device for disintegrating calculi and other concretions within the body
NOTE – Known applications include renal stones, gallstones, pancreatic duct stones, salivary stones, orthopaedic
pain and calcification in tendons.
3.16
peak-negative acoustic pressure, peak-rarefactional acoustic pressure
maximum of the modulus of the rarefactional acoustic pressure at any spatial location in the
pressure pulse field (see 3.26 of IEC 61102)
Symbol: p
–
Unit: pascal, Pa
3.17
peak-positive acoustic pressure, peak-compressional acoustic pressure
maximum compressional acoustic pressure at any spatial location in the pressure pulse field
(see 3.27 of IEC 61102)
Symbol: p
+
Unit: pascal, Pa
3.18
pressure pulse
acoustic wave emitted by the lithotripsy equipment

61846 © IEC:1998(E) – 9 –
3.19
pressure pulse waveform
temporal waveform of the instantaneous acoustic pressure at a specified position in a
pressure pulse field and displayed over a period sufficiently long to include all significant
acoustic information in the pressure pulse
3.20
pulse-pressure-squared integral
time integral of the square of the instantaneous acoustic pressure over the pressure pulse
waveform
Symbol: p
i
Unit: pascal squared seconds
3.21
rise time
at the focus, time taken for the instantaneous acoustic pressure to increase from 10 % to
90 % of the peak-positive acoustic pressure (see figure C.1)
Symbol: t
r
Unit: second, s
3.22
target location
location in space where the manufacturer intends the user to locate the calculi
3.23
temporal integration limits
3.23.1
positive temporal integration limits
times between which the positive acoustic pressure first exceeds 10 % of its maximum value
and the first time it reduces below 10 % of its maximum value
Symbol: T
P
Unit: seconds
3.23.2
total temporal integration limits
times between which the absolute value (modulus) of pressure pulse waveform first exceeds
10 % of its maximum value and the last time it reduces below 10 % of its maximum value
Symbol: T
T
Unit: seconds
– 10 – 61846 © IEC:1998(E)
4 List of symbols
A : focal cross-sectional area
f
E : derived focal acoustic pulse energy
f
E : derived acoustic pulse energy
R
f : focal width, maximum
x
f : focal width, orthogonal
y
f : focal extent
z
I: instantaneous intensity
M : end-of-cable loaded sensitivity of the hydrophone
L
p: instantaneous acoustic pressure
p : peak-negative acoustic pressure
–
p : peak-positive acoustic pressure
+
p : pulse-pressure-squared integral
i
PII: derived pulse-intensity integral
t : rise time
r
t : compressional pulse duration
FWHMp+
T : positive temporal integration limits
P
T : total temporal integration limits
T
V : focal volume
f
Z: characteristic acoustic impedance of the medium
5 Conditions of measurement
Measurements shall be performed in a situation approximating conditions of actual operation.
Parameters to be considered include:
– pressure pulse generator drive level;
– rate of pressure pulse release;
– ambient temperature;
– electrical conductivity of water in the measuring tank;
– temperature and oxygen content of water in the measuring tank.
The values of these parameters at which the measurements are made shall be noted.
Degassed water (see annex C) at 20 °C to 40 °C should be used in the measuring tank (test
chamber) which shall be large enough to allow the measurement environment to approximate
free-field conditions. If degassed water is not used, great care shall be taken to ensure that
bubbles do not collect on the hydrophone nor anywhere in the beam path.

61846 © IEC:1998(E) – 11 –
The conductivity of the water shall be suitable for the hydrophone being used. The calibration
of the hydrophone shall be known at the temperature of the water in the measuring tank.
6 Test equipment
6.1 Test chamber
The test chamber shall be a water tank constructed in a form that can be securely fixed to the
pressure pulse generator so that the acoustic output from the pressure pulse generator is
coupled into a volume of water. The chamber shall be sufficiently large to allow the expected
position of the focus to be several centimetres away from any reflective boundary, in particular
the water surface. The distance between the focus and reflective boundaries shall be chosen
such that no spurious or multiple reflections of the pressure pulse interfere with the
measurements.
There shall be a suitable mechanical holder for the hydrophone which shall be mounted on a
coordinate positioning system to allow adjustment and measurement of the position of the
hydrophone in three orthogonal directions relative to the focus. One axis (z axis) of the
co-ordinate positioning system shall be collinear with the beam axis. The relative position of
the hydrophone shall be measurable with a precision of 0,5 mm or better.
Care shall be taken to ensure that the coupling membranes do not influence the
measurements. The coupling media shall be as specified by the manufacturer.
6.2 Hydrophone
The hydrophone shall have characteristics complying with IEC 60866.
For the purposes of this standard, two classes of hydrophones are specified:
–a focus hydrophone;
– a field hydrophone.
6.2.1 Focus hydrophone
The focus hydrophone shall be equivalent to a single-film piezopolymer spot-poled membrane
type not thicker than 25 μm (see annex C and IEC 61102).
Calibration shall be performed in the frequency range 0,5 MHz to 15 MHz in accordance with
the requirements of IEC 60866.
The frequency response shall not vary by more than ±3 dB over the calibrated frequency range.
The effective diameter of the hydrophone shall be not greater than 1,0 mm, it should be as
small as possible and its value shall be stated.
NOTE – The lower frequency limit of current hydrophone calibration according to IEC 60866 and IEC 61102 is
0,5 MHz. It would be desirable, however, for the purpose of the measurements described here to extend the
hydrophone calibration to lower frequencies, at least to 0,2 MHz.
6.2.2 Field hydrophone
The field shall have a robust construction and shall have a response which does
hydrophone
not vary by more than ±3 dB per octave over the frequency range from 0,5 MHz to 15 MHz.
The effective diameter of the hydrophone shall be not greater than 1,0 mm, it should be as
small as possible and its value shall be stated.

– 12 – 61846 © IEC:1998(E)
The sensitivity of the hydrophone shall not vary by more than ±10 % over the course of the
measurements.
NOTE – Two different hydrophones are permitted because many of those suitable for measurements at the focus
are very fragile. A more robust, less highly specified device is therefore permitted for general field measurements.
Care is to be taken, when selecting a field hydrophone to select a type which will provide the needed linearity and
negative acoustic pressure readings of the high pressures encountered.
6.3 Voltage measurement
6.3.1 Oscilloscope or transient recorder
The device used to observe and measure the hydrophone output signal shall be appropriate
for the purpose, its frequency response and input capacitance and resistive impedance shall be
reported. A digital oscilloscope with a sampling frequency greater than 100 MHz is the
preferred option, although a transient recorder and digital storage for subsequent computer
display may be satisfactory.
The end-of-cable loaded sensitivity of the hydrophone shall be determined as specified in
5.1.2 of IEC 61102, this value shall then be used to calculate the incident acoustic pressures
from the observed hydrophone output voltages.
6.3.2 Pressure-pulse-waveform recording
The output voltage waveform from the hydrophone shall be recorded in such a way as to allow
the measurement or calculation of:
– instantaneous acoustic pressure, p;
– peak-negative acoustic pressure, p ;
–
– peak-positive acoustic pressure, p ;
+
– rise time, t ;
r
– compressional pulse duration, t ;
FWHMp+
– instantaneous intensity, I.
7 Measurement procedure
The measurements shall be made at least at one clinical setting as specified by the
manufacturer. If only one setting is used, this setting shall be the maximum available for
clinical application. The settings used shall be documented.
Using the x-y-z coordinate positioning system, with the z direction being the beam axis, the
following measurements shall be made to define the spatial characteristics of the beam.
The x axis shall be taken as the direction of the maximum beam width in the x-y plane which
contains the focus. The distance between the focus and the target location shall be
documented. If the peak-positive acoustic pressure p in the target location does not differ
+
by more than 10 % of p in the focus, it is feasible to do the measurements in the x-y plane at
+
the z position indicated by the target location.
7.1 Spatial measurements
The spatial distribution of acoustic pressure shall be measured in the test chamber.
The maximum sampling interval shall be the lesser of 1 mm or 1/5 th of the minimum width of
the –6 dB isobar in the x-y plane. It shall be the lesser of 2 mm or 1/5 th of the maximum
dimension of the –6 dB isobar in the x-z plane. If the values of p from sampling point
+
to sampling point do not differ by more than 10 %, the sampling intervals can be extended,
e.g. to 5 or 10 mm. The sampling intervals actually used shall be documented. The field
hydrophone may be used.
61846 © IEC:1998(E) – 13 –
NOTE 1 – It may be worthwhile to perform measurements in the vicinity of the target location to locate the focus
and hence define the direction of the z axis, before making other measurements. (See annex C.)
NOTE 2 – The direction of the x axis will be provisional until the plot detailed in 7.1.1 has been completed.
NOTE 3 – Care is to be used in selecting hydrophones of sufficient linearity in negative and positive regions so
that the 6 dB measurements can be made without distortion.
7.1.1 Beam plots of peak-positive acoustic pressure
The values of peak-positive acoustic pressure in the - plane which contains the focus
x y
shall be measured. The –6 dB beam widths shall be determined from the –6 dB contour plot.
NOTE – At each value of y that peak-positive acoustic pressure is measured, pulse intensity integral should
also be determined since the two curves are not identical and there can be significant differences between the
areas under the curve as calculated from peak-positive acoustic pressure versus pulse intensity integral.
(See 7.3.1.)
The orientation of the x axis shall be chosen such that it corresponds to the direction of the
maximum beam width.
The variation of peak-positive acoustic pressure in - and - planes shall be measured and
x z y z
plotted at least as a –6 dB contour in each plane.
7.1.2 Beam plots of peak-negative acoustic pressure
The values of peak-negative acoustic pr
...