IEC 61689:2007
(Main)Ultrasonics - Physiotherapy systems - Field specifications and methods of measurement in the frequency range 0,5 MHz to 5 MHz
Ultrasonics - Physiotherapy systems - Field specifications and methods of measurement in the frequency range 0,5 MHz to 5 MHz
Is applicable to ultrasonic equipment designed for physiotherapy consisting of an ultrasonic transducer generating continuous or quasi-continuous wave ultrasonic energy in the frequency range 0,5 MHz to 5 MHz. This standard only relates to ultrasonic physiotherapy equipment employing a single plane unfocused circular transducer per treatment head, producing static beams perpendicular to the face of the treatment head. This standard specifies: - methods of measurement and characterization of the output of ultrasonic physiotherapy equipment based on reference testing methods; - characteristics to be specified by manufacturers of ultrasonic physiotherapy equipment based on reference testing methods; - guidelines for safety of the ultrasonic field generated by ultrasonic physiotherapy equipment; - methods of measurement and characterization of the output of ultrasonic physiotherapy equipment based on routine testing methods; - acceptance criteria for aspects of the output of ultrasonic physiotherapy equipment based on routine testing methods. Therapeutic value and methods of use of ultrasonic physiotherapy equipment are not covered by the scope of this standard. This second edition cancels and replaces the first edition published in 1996 and constitutes a technical revision. This second edition is a result of maintenance on this standard and the referenced standards IEC 61161 (2006) and IEC 62127-1. A relatively large technical change is the determination of the effective radiating area. This is now no longer based on the measurement of four areas but only on one. This change was needed to improve the accuracy of the determination of this parameter for small transducers. Be aware that this change may alter the value obtained for this and related parameters.
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Standards Content (Sample)
IEC 61689
Edition 2.0 2007-08
INTERNATIONAL
STANDARD
Ultrasonics – Physiotherapy systems – Field specifications and methods of
measurement in the frequency range 0,5 MHz to 5 MHz
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IEC 61689
Edition 2.0 2007-08
INTERNATIONAL
STANDARD
Ultrasonics – Physiotherapy systems – Field specifications and methods of
measurement in the frequency range 0,5 MHz to 5 MHz
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 11.040.60 ISBN 2-8318-9256-2
– 2 – 61689 © IEC:2007(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 List of symbols .15
5 Ultrasonic field specifications .16
6 Conditions of measurement and test equipment used .17
6.1 General .17
6.2 Test vessel.18
6.3 Hydrophone.18
6.4 RMS or peak signal measurement .18
7 Type testing reference procedures and measurements.19
7.1 General .19
7.2 Rated output power .19
7.3 Hydrophone measurements.19
7.4 Effective radiating area .20
7.5 Reference type testing parameters .22
7.6 Acceptance criteria for reference type testing.22
8 Routine measurement procedure.23
8.1 General .23
8.2 Rated output power .23
8.3 Effective radiating area .23
8.4 Beam non-uniformity ratio .24
8.5 Effective intensity.24
8.6 Acceptance criteria for routine testing .24
9 Sampling and uncertainty determination .24
9.1 Reference type testing measurements.24
9.2 Routine measurements.24
9.3 Uncertainty determination.25
Annex A (informative) Guidance for performance and safety.26
Annex B (normative) Raster scan measurement and analysis procedures .31
Annex C (normative) Diametrical or line scan measurement and analysis procedures.33
Annex D (informative) Rationale concerning the beam cross-sectional area definition.36
Annex E (informative) Factor used to convert the beam cross-sectional area (A ) at
BCS
the face of the treatment head to the effective radiating area (A ) .42
ER
Annex F (informative) Determining acoustic power through radiation force
measurements.44
Annex G (informative) The validity of low-power measurements of the beam cross-
sectional area (A ).46
BCS
Annex H (informative) Influence of hydrophone effective diameter .47
Annex I (informative) Effective radiating area measurement using a radiation force
balance and absorbing apertures.49
Annex J (informative) Guidance on uncertainty determination .59
61689 © IEC:2007(E) – 3 –
Bibliography.61
Figure A.1 – The normalized, time-averaged values of the acoustic intensity (unbroken
line) and of one of its plane-wave approximations (broken line), existing on the axis of
a circular piston source of ka = 30, versus the normalized distance s, where s = λz/a .29
Figure A.2 – Histogram of R values for 37 treatment heads of various diameter and
BN
frequency.30
Figure D.1 – Iso-pressure lines of a typical physiotherapy treatment head of small
geometrical area (ka = 17) .38
Figure D.2 – Plot of beam cross-sectional area against different limit values for a
small variation in distance along the beam alignment axis, z .39
Figure D.3 – Normalized values of beam cross-sectional area for IEC and FDA limit
values for five transducers of different ka values, z = 0,5 cm .40
Figure D.4 – Variation of the beam cross-sectional area (A ) with distance from the
BCS
face of the treatment head .41
Figure D.5 – Variation of the normalized beam cross-sectional area (A ) with
BCS
transducer ka .41
Figure E.1 – Conversion factor F as a function of the ka product for ka product
ac
between 40 and 160 .43
Figure I.1 – Schematic representation of aperture measurement set-up .49
Figure I.2 – Measured power as a function of aperture diameter for commercially-
available 1 MHz physiotherapy treatment heads .54
Figure I.3 – Cumulative sum of annular power contributions, previously sorted in
descending order of intensity contribution, plotted against the cumulative sum of their
respective annular areas.57
Table C.1 – Constitution of the transformed array [B] used for the analysis of half-line
scans.34
Table F.1 – Necessary target size, expressed as the minimum target radius b, as a
function of the ultrasonic frequency, f, the effective radius of the treatment head, a ,
and the target distance, z, calculated according to 5.3 of IEC 61161 (see [5]). .
Table G.1 – Variation of the beam cross-sectional area (A (z)) with the indicated
BCS
output power from two transducers .46
Table H.1 – Comparison of measurements of the beam cross-sectional area (A (z))
BCS
made using hydrophones of geometrical active element radii 0,3 mm, 0,5 mm and
2,0 mm .48
Table I.1 – Aperture measurement check sheet .53
Table I.2 – Annular power contributions .55
Table I.3 – Annular intensity contributions .55
Table I.4 – Annular intensity contributions, sorted in descending order .56
Table I.5 – Annular power contributions, sorted in descending order of intensity
contribution.56
Table I.6 – Cumulative sum of annular power contributions, previously sorted in
descending order of intensity contribution, and the cumulative sum of their respective
annular areas.57
– 4 – 61689 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ULTRASONICS –
PHYSIOTHERAPY SYSTEMS –
FIELD SPECIFICATIONS AND METHODS OF
MEASUREMENT IN THE FREQUENCY RANGE 0,5 MHz TO 5 MHz
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61689 has been prepared by IEC technical committee 87:
Ultrasonics.
This second edition cancels and replaces the first edition published in 1996 and constitutes a
technical revision.
This second edition is a result of maintenance on this standard and the referenced standards
IEC 61161 (2006) and IEC 62127-1. A relatively large technical change is the determination of
the effective radiating area. This is now no longer based on the measurement of four areas
but only on one. This change was needed to improve the accuracy of the determination of this
parameter for small transducers. Be aware that this change may alter the value obtained for
this and related parameters.
61689 © IEC:2007(E) – 5 –
The text of this standard is based on the following documents:
CDV Report on voting
87/351/CDV 87/370/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This standard should be read in conjunction with IEC 60601-2-5, which, as indicated in its
preface, will be revised in order to be compatible with this standard.
NOTE The following print types are used:
– Requirements: in roman type
– Test specifications: in italic type
– Notes: in small roman type
– Words in bold in the text are defined in Clause 3.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
– 6 – 61689 © IEC:2007(E)
INTRODUCTION
Ultrasound at low megahertz frequencies is widely used in medicine for the purposes of
physiotherapy. Such equipment consists of a generator of high-frequency electrical energy
and usually a hand-held treatment head, often referred to as an applicator. The treatment
head consists of a transducer, usually a disk of piezoelectric material, for converting the
electrical energy to ultrasound and is often designed for contact with the human body.
61689 © IEC:2007(E) – 7 –
ULTRASONICS –
PHYSIOTHERAPY SYSTEMS –
FIELD SPECIFICATIONS AND METHODS OF
MEASUREMENT IN THE FREQUENCY RANGE 0,5 MHz TO 5 MHz
1 Scope
This International Standard is applicable to ultrasonic equipment designed for physiotherapy
consisting of an ultrasonic transducer generating continuous or quasi-continuous wave
ultrasonic energy in the frequency range 0,5 MHz to 5 MHz.
This standard only relates to ultrasonic physiotherapy equipment employing a single plane
unfocused circular transducer per treatment head, producing static beams perpendicular to
the face of the treatment head.
This standard specifies:
– methods of measurement and characterization of the output of ultrasonic physiotherapy
equipment based on reference testing methods;
– characteristics to be specified by manufacturers of ultrasonic physiotherapy equipment
based on reference testing methods;
– guidelines for safety of the ultrasonic field generated by ultrasonic physiotherapy
equipment;
– methods of measurement and characterization of the output of ultrasonic physiotherapy
equipment based on routine testing methods;
– acceptance criteria for aspects of the output of ultrasonic physiotherapy equipment
based on routine testing methods.
Therapeutic value and methods of use of ultrasonic physiotherapy equipment are not
covered by the scope of this standard.
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60050-801:1994, International Electrotechnical Vocabulary (IEV) – Chapter 801:
Acoustics and electroacoustics
IEC 60469-1:1987, Pulse techniques and apparatus – Part 1: Pulse terms and definitions
IEC 60601-1, Medical electrical equipment – Part 1: General requirements for basic safety
and essential performance
IEC 60601-2-5:2000, Medical electrical equipment – Part 2-5: Particular requirements for the
safety of ultrasonic physiotherapy equipment
IEC 61161:2006, Ultrasonics – Power measurement – Radiation force balances and
performance requirements
– 8 – 61689 © IEC:2007(E)
IEC 62127-1:2007, Ultrasonics – Hydrophones – Part 1: Measurement and characterization of
medical ultrasonic fields up to 40 MHz using hydrophones
IEC 62127-3:2007, Ultrasonics – Hydrophones – Part 3: Properties of hydrophones for
ultrasonic fields up to 40 MHz
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acoustic pulse waveform
temporal waveform of the instantaneous acoustic pressure at a specified position in an
acoustic field and displayed over a period sufficiently long to include all significant acoustic
information in a single pulse or tone-burst, or one or more cycles in a continuous wave
NOTE 1 Temporal waveform is a representation (e.g. oscilloscope presentation or equation) of the instantaneous
acoustic pressure.
NOTE 2 Definition adopted from IEC 60469-1.
3.2
acoustic repetition period
arp
pulse repetition period for non-automatic scanning systems and the scan repetition period
for automatic scanning systems, equal to the time interval between corresponding points of
consecutive cycles for continuous wave systems
NOTE 1 Acoustic repetition period is expressed in seconds (s).
NOTE 2 Definition adopted from IEC 62127-1.
3.3
acoustic frequency
acoustic-working frequency
frequency of an acoustic signal based on the observation of the output of a hydrophone
placed in an acoustic field at the position corresponding to the spatial-peak temporal-peak
acoustic pressure
NOTE 1 The signal is analysed using either the zero-crossing acoustic-working frequency technique or a
spectrum analysis method. Acoustic-working frequencies are defined in 3.3.1 and 3.3.2.
NOTE 2 In a number of cases the present definition is not very helpful or convenient, especially for broadband
transducers. In that case a full description of the frequency spectrum should be given in order to enable any
frequency-dependent correction to the signal.
NOTE 3 Acoustic frequency is expressed in hertz (Hz).
NOTE 4 Definition adopted from IEC 62127-1.
3.3.1
zero-crossing acoustic-working frequency
f
awf
this is determined according to the procedure specified in IEC/TR 60854.
NOTE This frequency is intended for continuous wave systems only.
61689 © IEC:2007(E) – 9 –
3.3.2
arithmetic-mean acoustic-working frequency
f
awf
arithmetic mean of the most widely separated frequencies f and f , within the range of three
1 2
times f , at which the magnitude of the acoustic pressure spectrum is 3 dB below the peak
magnitude
NOTE 1 This frequency is intended for pulse-wave systems only.
NOTE 2 It is assumed that f < f .
1 2
3.4
amplitude modulated wave
wave in which the ratio p / √2p at any point in the far field on the beam alignment axis is
p rms
greater than 1,05, where p is the temporal-peak acoustic pressure and p is the r.m.s.
p rms
acoustic pressure
3.5
attachment head
accessory intended to be attached to the treatment head for the purpose of modifying the
ultrasonic beam characteristics
NOTE Definition adopted from IEC 60601-2-5.
3.6
beam alignment axis
straight line joining two points of spatial-peak temporal-peak acoustic pressure on two plane
surfaces parallel to the faces of the treatment head. One plane is at a distance of
approximately A /(πλ) where A is the nominal value of the effective radiating area of
ERN ERN
the treatment head and λ is the wavelength of the ultrasound corresponding to the nominal
value of the acoustic working frequency. The second plane surface is at a distance of either
2A /(πλ) or A /(3πλ), whichever is the more appropriate. For the purposes of alignment,
ERN ERN
this line may be projected to the face of the treatment head
NOTE 1 If the nominal value of the effective radiating area is unknown, then another suitable area may be used
to define the beam alignment axis such as the area of the active element of the ultrasonic transducer.
NOTE 2 As the beam alignment axis is used purely for the purposes of alignment, the definitions of specific
distances may be relaxed slightly to reflect the constraints of the measurement system employed. For example,
some treatment heads will have A /(πλ) considerably greater than 12 cm, in which case a maximum distance of
ERN
12 cm may be used to define the first plane. General guidelines for determining the beam alignment axis are
given in 8.3.
3.7
beam cross-sectional area
A
BCS
minimum area in a specified plane perpendicular to the beam alignment axis for which the
sum of the mean square acoustic pressure is 75 % of the total mean square acoustic
pressure
NOTE Beam cross-sectional area is expressed in centimetre squared (cm ).
3.8
beam maximum intensity
product of the beam non-uniformity ratio and effective intensity
NOTE Beam maximum intensity is expressed in watt per centimetre squared (W/cm ).
– 10 – 61689 © IEC:2007(E)
3.9
beam non-uniformity ratio
R
BN
ratio of the square of the maximum r.m.s. acoustic pressure to the spatial average of the
square of the r.m.s. acoustic pressure, where the spatial average is taken over the effective
radiating area. Beam non-uniformity ratio is given by:
p A
max ER
R = (1)
BN
pms A
t o
where
p is the maximum r.m.s. acoustic pressure;
max
A is the effective radiating area;
ER
pms is the total mean square acoustic pressure;
t
A is the unit area for the raster scan.
o
3.10
absolute maximum beam non-uniformity ratio
beam non-uniformity ratio plus the 95 % confidence overall uncertainty in the beam non-
uniformity ratio
3.11
beam type
descriptive classification for the ultrasonic beam in one of three types: collimated,
convergent or divergent
3.12
collimated
beam for which the active area coefficient, Q, obeys the following inequality:
–1 –1
–0,05 cm ≤ Q ≤ 0,1 cm
3.13
convergent
beam for which the active area coefficient, Q, obeys the following inequality:
–1
Q < –0,05 cm
3.14
divergent
beam for which the active area coefficient, Q, obeys the following inequality:
–1
Q > 0,1 cm
3.15
continuous wave
wave in which the ratio p / √2p , at any point in the far field on the beam alignment axis,
p rms
is the temporal-peak acoustic pressure and p is
is less than or equal to 1,05, where p
p rms
the r.m.s. acoustic pressure
3.16
duty factor
ratio of the pulse duration to the pulse repetition period
NOTE Definition adopted from IEC 60469-1, 5.3.2.4.
61689 © IEC:2007(E) – 11 –
3.17
effective intensity
I
e
intensity given by I = P/A where P is the output power and A is the effective radiating
e ER ER
area
NOTE Effective intensity is expressed in watt per centimetre squared (W/cm ).
3.18
absolute maximum effective intensity
value of the effective intensity corresponding to the absolute maximum rated output power
and the absolute minimum effective radiating area from the equipment
3.19
effective radiating area
A
ER
beam cross-sectional area determined at a distance of 0,3 cm from the front of the
treatment head, A (0,3), multiplied by a dimensionless factor, F , given by:
BCS ac
F = 1,354 (2)
ac
NOTE 1 The conversion factor F is used here in order to derive the area close to the treatment head which
ac
contains 100 % of the total mean square acoustic pressure. The origin of the value of F is described in
ac
Annex E and bibliographic references [3] and [4].
NOTE 2 Beam cross-sectional area is expressed in centimetre squared (cm ).
3.20
absolute minimum effective radiating area
effective radiating area minus the 95 % confidence overall uncertainty in the effective
radiating area
3.21
end-of-cable loaded sensitivity
end-of-cable loaded sensitivity of a hydrophone (or hydrophone-assembly)
M (f)
L
ratio of the instantaneous voltage at the end of any integral cable or output connector of a
hydrophone or hydrophone-assembly, when connected to a specified electric load
impedance, to the instantaneous acoustic pressure in the undisturbed free field of a plane
wave in the position of the reference centre of the hydrophone if the hydrophone were
removed
NOTE 1 End-of-cable loaded sensitivity is expressed in volts per pascal (V/Pa).
NOTE 2 Definition adopted from IEC 62127-3.
3.22
far field
acoustic (sound) field at distances from an ultrasonic transducer where the values of the
instantaneous acoustic pressure and particle velocity are substantially in phase [see also
IEC 60050-801, 801-03-30]
NOTE 1 Definition adopted from IEC 62127-1.
NOTE 2 For the purposes of this standard, the far field is at a distance greater than A /(πλ) where A is the
ERN ERN
nominal value of the effective radiating area of the treatment head and λ is the wavelength of the ultrasound
corresponding to the acoustic working frequency. This differs from IEC 62127-1.
3.23
hydrophone
transducer that produces electrical signals in response to waterborne acoustic signals
NOTE Definition adopted from IEC 60050-801, 801-32-26 (1994).
– 12 – 61689 © IEC:2007(E)
3.24
instantaneous acoustic pressure
p(t)
pressure minus the ambient pressure at a particular instant in time and at a particular point in
an acoustic field (see also IEC 60050-801, 801-01-19)
NOTE 1 Instantaneous acoustic pressure is expressed in pascal (Pa).
NOTE 2 Definition adopted from IEC 60050-801, 801-21-19 (1994).
3.25
active area coefficient
Q
quotient of the active area gradient, m, and the beam cross-sectional area at 0,3 cm from
the face of the treatment head, A (0,3)
BCS
−1
NOTE Active area coefficient is expressed in per centimetre (cm ).
3.26
active area gradient
m
gradient of the line connecting the beam cross-sectional area at 0,3 cm from the face of the
treatment head, A (0,3), and the beam cross-sectional area at the position of the last
BCS
axial maximum acoustic pressure, A (Z ), versus distance
BCS N
NOTE Active area gradient is expressed in centimetre (cm).
3.27
mean square acoustic pressure
mean square of the instantaneous acoustic pressure at a particular point in the acoustic
field. The mean is taken over an integral number of acoustic repetition periods
NOTE 1 In practice, the mean value is often derived from rms measurements.
NOTE 2 Mean square acoustic pressure is expressed in pascal squared (Pa ).
3.28
total mean square acoustic pressure
pms
t
sum of the mean square acoustic pressure values, each with a specified incremental area,
in a specified plane over specified limits of summation
NOTE Total mean square acoustic pressure is expressed in pascal squared (Pa ).
3.29
modulation waveform
temporal envelope waveform of the amplitude modulated wave at the point of peak r.m.s.
acoustic pressure on the beam alignment axis and displayed over a period sufficiently long
to include all significant acoustic information in the amplitude modulated wave
3.30
output power
P
time-average ultrasonic power emitted by a treatment head of ultrasonic physiotherapy
equipment into an approximately free field under specified conditions in a specified medium,
preferably in water
NOTE 1 Definition adopted from IEC 61161:2006.
NOTE 2 Output power is expressed in watt (W).
61689 © IEC:2007(E) – 13 –
3.31
rated output power
maximum output power of the ultrasonic physiotherapy equipment at the rated value of
the mains voltage, with control settings configured to deliver maximum output power
NOTE Rated output power is expressed in watt (W).
3.32
absolute maximum rated output power
sum of the rated output power, the 95 % confidence overall uncertainty in the rated output
power, and the maximum increase in the rated output power for a ±10 % variation in the
rated value of the mains voltage
NOTE 1 The possibility of variation in the rated output power resulting from ± 10 % variation in the rated value
of the mains voltage should be checked by using a variable output transformer between the mains voltage supply
and the ultrasonic physiotherapy equipment. See A.2 for further guidance.
NOTE 2 Absolute maximum rated output power is expressed in watt (W).
3.33
temporal-maximum output power
P
tm
in the case of an amplitude modulated wave, the temporal-maximum output power is
given by:
⎛ p ⎞
p
⎜ ⎟
P = 1/2 P (3)
tm
⎜ ⎟
p
⎝ rms⎠
where
P is the actual output power under amplitude modulated wave conditions;
p is the temporal-peak acoustic pressure;
p
p is the true r.m.s. acoustic pressure.
rms
Both p and p are measured under amplitude modulated wave conditions and at a
p rms
specified point on the beam alignment axis
NOTE Temporal-maximum output power is expressed in watt (W).
3.34
pulse duration
time interval beginning at the first time the pressure amplitude exceeds a reference value and
ending at the last time the pressure amplitude returns to that value. The reference value is
equal to the sum of the minimum pressure amplitude and 10 % of the difference between the
maximum and minimum pressure amplitude
NOTE 1 This definition differs from that of 3.48 of IEC 62127-1, from which it is derived, to account for incomplete
modulation.
NOTE 2 Pulse duration is expressed in seconds (s).
3.35
pulse repetition period
prp
time interval between two equal moments in time of successive pulses or tone-bursts
NOTE 1 This applies to single element non-automatic scanning systems and automatic scanning systems. See
also IEC 60469-1:1987, 5.3.2.1.
NOTE 2 Pulse repetition period is expressed in seconds (s).
– 14 – 61689 © IEC:2007(E)
3.36
pulse repetition rate
prr
reciprocal of the pulse repetition period
NOTE 1 See also IEC 60469-1:1987, 5.3.2.2.
NOTE 2 The pulse repetition rate is expressed in hertz (Hz).
NOTE 3 The pulse repetition rate is equal to the repetition frequency of the modulated waveform.
3.37
rms acoustic pressure
p
rms
root-mean-square (rms) of the instantaneous acoustic pressure at a particular point in an
acoustic field
NOTE 1 The mean should be taken over an integral number of acoustic repetition periods unless otherwise
specified.
NOTE 2 Definition adopted from IEC 62127-1.
NOTE 3 rms acoustic pressure is expressed in pascal (Pa).
3.38
maximum rms acoustic pressure
p
max
maximum value of the rms acoustic pressure detected by a hydrophone over the entire
acoustic field
NOTE Maximum rms acoustic pressure is expressed in pascal (Pa).
3.39
peak rms acoustic pressure
maximum value of the rms acoustic pressure over a specified region, line or plane in an
acoustic field
NOTE Peak rms acoustic pressure is expressed in pascal (Pa).
3.40
temporal-maximum intensity
I
m
in the case of an amplitude modulated wave, the temporal-maximum intensity is given by:
P
tm
I = (4)
m
A
ER
where
P is the temporal-maximum output power;
tm
A is the effective radiating area.
ER
NOTE Temporal-maximum intensity is expressed in watt per centimetre squared (W/cm ).
3.41
temporal-peak acoustic pressure
p
tp
maximum value of the modulus of the instantaneous acoustic pressure at a particular point
in an acoustic field
61689 © IEC:2007(E) – 15 –
NOTE 1 Definition adopted from IEC 62127-1.
NOTE 2 Temporal-peak acoustic pressure is expressed in pascal (Pa).
3.42
treatment head
assembly comprising one ultrasonic transducer and associated parts for local application of
ultrasound to the patient
NOTE Definition adopted from IEC 60601-2-5.
3.43
ultrasonic transducer
device capable of converting electrical energy to mechanical energy within the ultrasonic
frequency range and/or reciprocally of converting mechanical energy to electrical energy
NOTE Definition adopted from IEC 62127-1.
3.44
ultrasound
acoustic oscillation whose frequency is above the high-frequency limit of audible sound (about
16 kHz)
NOTE Definition adopted from IEC 60050-801 (1994).
3.45
ultrasonic physiotherapy equipment; equipment
equipment for the generation and application of ultrasound to a patient for therapeutic
purposes
NOTE Definition adopted from IEC 60601-2-5.
4 List of symbols
a Geometrical radius of the active element of a treatment head
A Beam cross-sectional area
BCS
A (0,3) Beam cross-sectional area evaluated at 0,3 cm from the front face of the
BCS
treatment head
A (z ) Beam cross-sectional area evaluated at the position of the last axial maximum, z
BCS N
N
A Effective radiating area of a treatment head
ER
A Nominal value of the effective radiating area of a treatment head
ERN
a Geometrical radius of the active element of a hydrophone
g
A Geometrical area of the face of a treatment head
g
a Maximum hydrophone effective radius defined by IEC 62127-3
max
A
Unit area for a raster scan
o
b Minimum radius of a target for a radiation force balance
c Speed of sound in water
f Acoustic working frequency
F Conversion factor to convert A (0,3) to A
ac BCS ER
– 16 – 61689 © IEC:2007(E)
I Effective intensity
e
I Temporal maximum intensity
m
k
(= 2π/λ) Circular wave number
m Active area gradient
M End-of-cable loaded sensitivity of a hydrophone
L
P Output power of a treatment head
P Temporal-maximum output power
tm
p Temporal-peak acoustic pressure
p
p Maximum r.m.s. acoustic pressure
max
p RMS acoustic pressure
rms
pms Total mean square acoustic pressure
t
pms (z) Total mean square acoustic pressure determined in the specific plane z
t
Q
Active area coefficient
R Ratio of the peak r.m.s. acoustic pressure to the r.m.s. acoustic pressure
averaged over the beam cross-sectional area in a specified plane
R Beam non-uniformity ratio
BN
S Step size for a raster scan
S(z) Step size for raster scan in the specific plane z
U End-of-cable voltage for a hydrophone
U Hydrophone signal for the i-th scan point
i
U Maximum value of the hydrophone voltage
p
z Distance from the face of the treatment head to a specified point on the beam
alignment axis
z Distance from the face of the treatment head to the measurement plane
j
(perpendicular to the beam alignment axis) of interest
z Distance of the last axial maximum from the face of the treatment head
N
z Distance of the peak r.m.s. acoustic pressure from the front face of the
p
treatment head
λ Ultrasonic wavelength
ρ Density of water
Uncertainties are specified throughout this standard at the 95 % confidence level.
5 Ultrasonic field specifications
In addition to the general requirements specified in IEC 60601-1 and specific requirements
specified in IEC 60601-2-5, manufacturers shall specify nominal values for the following
parameters in the accompanying literature for each type of treatment head:
61689 © IEC:2007(E) – 17 –
– rated output power (±20 %);
– effective radiating area (A ) of the treatment head (±20 %);
ERN
– effective intensity at the same equipment settings as the nominal value of the rated output
power (±30 %);
– acoustic working frequency (±10 %);
– beam non-uniformity ratio (R ) (±30 %);
BN
– beam maximum intensity (±30 %);
– beam type;
– pulse duration, pulse repetition period, duty factor and the ratio of the temporal maximum
output power to the output power for each modulation setting (±5 %);
– modulation waveform for each modulation setting.
The numbers given in brackets are the tolerances defining the range of acceptable values for
the results of either the type testing reference measurements specified in Clause 7 or the
routine measurements specified in Clause 8. If the published tolerance requirement cannot be
met, then the 95 % confidence level that is achievable should be reported. It shall then be
demonstrated that the reported value, when incorporated with the tolerance so as to produce
the ‘worst case’ value, remains with the range of acceptable values, as specified in
IEC 60601-2-5, and on which guidance is provided in Annex A.
The temperature range shall be specified for the parameters specified above. The range of
line voltages shall also be specified.
For ultrasonic physiotherapy equipment using a treatment head capable of operating at
more than one nominal value of acoustic working frequency, the parameters listed above
shall be specified for each nominal value of acoustic working frequency.
In addition, for ultrasonic physiotherapy equipment which can use an attachment head,
the parameters listed above shall be specified for each combination of attachment head and
treatment head.
NOTE This document does not contain requirements relating to safety: these are covered in IEC 60601-2-5.
Guidance on performance and safety can be found in Annex A of this document.
6 Conditions of measurement and test equipment used
6.1 General
All measurements shall be undertaken under approximately free-field conditions at a
° °
temperature of 22 C ± 3 C.
If measurements are carried out at any other temperature, a test shall be undertaken to show
that the results, determined in accordance with 7.6 and 8.3, are not dependent on the
temperature at which the tests were undertaken.
Degassed water shall be used for the measurement of ultrasonic power, see 7.2. Degassed
water is not essential for the hydrophone measurements, see 7.3.
NOTE Degassed water is essential to avoid cavitation when the physiotherapy units are operated at or near full
output power. Information on preparation of water suitable for physiotherapy measurements may be found in
IEC 61161, and in bibliographic reference [10].
All measurements shall be made after the warm-up period specified by the manufacturer. If no
such period is specified, a period of 30 min shall be used.
– 18 – 61689 © IEC:2007(E)
6.2 Test vessel
The test vessel used for all hydrophone measurements shall be large enough to allow the
immersion of both the treatment head and the hydrophone. The tank size should conform
to IEC 62127-1.
The relative position and angular orientation of the treatment head and hydrophone should
be adjustable for the purposes of alignment in accordance with IEC 62127-1. Full degrees of
freedom of movement of both may be provided, although the minimum requirement is that
either the treatment head or the hydrophone should possess three independent degrees of
translational movement. The measurements should be performed under free-field conditions.
To achieve these conditions it may be necessary to line the walls of the test vessel as well as
the mounts used to hold the treatment head and the hydrophone with absorbers or angled
reflector(s) and absorber(s) of higher absorption and lower scatter. The free-field conditions
will be met sufficiently when the overall echo is reduced by more than 25 dB. Various
methods can be used to check the compliance for echo reduction of the tank lining materials
used. One example to check the absorbing or scattering materials used is given below.
Compliance for overall echo reduction of an acoustic absorber may be checked using the
following procedure. Echo reduction should be measured at the acoustic working frequency
of the treatment head under test using tone-burst ultrasound, with the acoustic absorber
located in the far-field of the separately driven ultrasonic transducer. The resulting
hydrophone signal (peak-to-peak or rms), produced by the reflection from the front surface of
the acoustic absorber, U , is compared to that from a perfect planar reflector, U .
absorber reflector
The acoustic absorber and the perfect reflector should be aligned near normal to the beam
alignment axis but angled so that the reflected signal can be intercepted by the hydrophone.
The echo r
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