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है”ह”ह

IS 11701 (1986): Guide for testing and callibration ofultrasonic therapeutic equipment [MHD 15: ElectromedicalEquiment]

E :11701-1986

Indian StandardGUIDE FOR TESTING AND

CALIBRATION OF ULTRASONICTHERAPEUTIC EQUIPMENT

Acoustics Sectional Committee, LTDC 5

Chairman Representing

SHRt K. D. PAVATE Central Electronics Engineering Research Institute( CSIR ), Pilani

Members

SHRIM. R. KAPOOR ( Alternate toShri K. D. Pavatc )

SHRI SANDEEP AHUJA Ahuja Radios, New DelhiSHRI K. R. GURUMURTHY( Alternate)

SHRI R. K. BHATXA Department of Telecommunication, New Delh!SHRI T. R. YYADHWA(Alternate\

SHRI K. CHANDRACHUDA~ ‘SHRI P. GHOSH

SHRI SHANKAR ( Alternate)DR P. N. GUPTACOL KRISHAN LAL

SHRI B. S. RUPRAI ( Afkmsatc)DR V. MOHANANSHRIJ. S. MONGA

SHRI M. S. MONGA ( Alt,rrnate )Snm J. S. MONGA

Directorate General of Civil Aviation, New DelhiRailway Board ( Ministry of Railways )

Department of Electronics. New DelhiMinistry of Defencc ( DGI )

National Physical Laboratory ( CSIR ), New DelhiBolton Private Ltd, New Delhi

Electronic Component Industries’ Association( ELCINA ), New Delhi

SHRI GHANISHAMDASS ( Aftemote )SHRI B. S. hTARAYAN Indian Telephone Industries Ltd, Bangalore

SHRI K. NAQARAJ (Alfewzte )DR ( KUIWARI) SHAIL~JA NXKAM All India Institute of Speech & Hearing, Mysorc

SHRI S. S. MURTIiY ( Alternate)PROP B. S. RAMAKRISHNA Central University, HyderabadSHRI S. L. REDEY Peico Electroni~ & Electrical Ltd, Bombay; and

Radio Electronic & Television Manufacturers’Association, Bombay

SHRI M. M. JOSHI ( Alternate)SHRI M. SHANKAXALINQA~ Directorate General of Supplies & Disposals,

New DelNlSHRI S. K. .%N Directorate General ofAll India Radio, NewDelid

SHRI W. V. B. RAMALINGA~ ( Alternate)

( Contirmd oss$agu 2 )

@ Copyright 1986INDIAN STANDARDS INSTITUTION

This publication is protected under the Indian Copyright Act (XIV of 19S7) andreproduction in whole or in part by any meansexceptwith writtesspermission of thepublisher shall be deemed to bean infringement of copyright under the said Act.

IS :11701-1986

( Continuedfrom fiage 1 )

Members Representing

CDR P. K. SINHA Ministry of Defence ( R&D)LT R. S. DAT-YA( Alternate)

SUPERINTENDENTSURVEYOROF Central Public Works Department, New DelhiWORKS ( FOOD)

SURVEYOROFWORKS I/FOOD ( Alternate)SHRIN. SRINIVASAN, Director General, 1S1( Ex-oflcio Member )

Director ( Electronics )

Secretary

SHRI PAVAN KUMAR

Deputy Director ( Electronics ), 1S1 *

Panel for Ultrasonic Transducers and Equipment, LTDC 5: P8 .

Convener

DR P. N. GUPTA Department of Electronics, New Delhl

Members

DR V. N. BXNDAL National Physical Laboratory ( CSIR ), New DelhiSHRI D. P. GOEL Central Scientific Instruments Organization

( CSIR ), ChandigarhSHRI C. M. PANT Vibronix Pvt Ltd, BombaySHUXA. S. RAMAUURTHY Nav~oc~h~ical & OceanograpK1c Laboratory,

I

[ndianGUIDE FOR

CALIBRATIONTHERAPEUT

O. FO1

0.1 This Indian Standard was adq~on 26 May 1986, after the drajCommittee had been approved by 1Division Council.

0.2 This standard covers the testintic equipment. The technique of r

0.3 While preparing this standardPub 150-1963 ‘Testing and calib]ment’, issued by the International

0.4 In reporting the result of a testif the final value, observed or talcdone in accordance with IS :2-196

1. SCOPE

1.1 This standard applies to apparaapparatus consists of a generator o’transducer, usually a disk of piczotultrasound. The transducer is h~radiation of the ultrasound to tlassociated parts with their housing

1.2 This standard provides suitablethe ultrasonic beam produced bythe manufacturers and the supervisas set forth herein.

1.3 This standard relates only to U1ing plane circular transducers infuture developments should Ieacappropriate provisions will be adde

●RUICSfor rounding cM numerical valu(

2

IS: 11701-1986

[miian StandardGUIDE FOR TESTING AND

CALIBRATION OF ULTRASONICTHERAPEUTIC EQUIPMENT

O. FOREWORD

$ 0.1 This Indian Standard was adopted by the Indian Standards Institutionon 26 May 1986, after the draft finalized by the Acoustics SectionalCommittee had been approved by the Electronics and TelecommunicationDivision Council.

0.2 This standard covers the testing and calibration of ultrasonic therapeu-tic equipment. The technique of measurements is given in Appendix A.

0.3 While preparing this standard, assistance has been derived from IECPub 150-1963 ‘Testing and calibration of ultrasonic therapeutic equip-ment’, issued by the International Electrotechnical Commission ( IEC ).

0.4 In reporting the result of a test made in accordance with this standard,if the final value, observed or calculated, is to be rounded off, it shall bedone in accordance with IS : 2-1960*.

1. SCOPE

1.1 This standard applies to apparatus designed for therapeutic use. Suchapparatus consists of a generator of high-frequency electrical energy and atransducer, usually a disk of piezoelectric material, for converting thk toultrasound. The transducer is housed in a holder designed for localradiation of the ultrasound to the human body. The transducer and

IIassociated parts with their housing are known as the treatment head.

1.2 This standard provides suitable methods for calibrating the intensity ofthe ultrasonic beam produced by this apparatus and should enable boththe manufacturers and the supervising agencies to provide proper Iabellingas set forth herein.

1.3 This standard relates only to ultrasonic therapeutic equipment employ-ing plane circular transducers in accordance with present practice. Iffuture developments should lead to other acceptable transducers,appropriate provisions will be added to these recommendations.

*Ruks for rounding off numerical values ( rttid ).

3

IS :11701-1986

1.4 This standard relates only tophysical characteristics of the apparatus,Therapeutic value and methods of use are not considered.

2. TERMINOLOGY

2.1 For the purpose of this standard, the terms and definitions given inIS :1885 ( Part 3/See 4 )-1966* shall apply.

3. ACOUSTIC CHARACTERISTICS

3.1 The uhrasonic output waves produced may ‘be unmodulated ormodulated. Modulation may be sinusoidal, pulsed or that resulting fromfull or half wave rectification. When the modulation is less than 25 per.cent, the wave will be considered unmodulated.

NOTE — The degree of modulation is the quotient of the difference and the sum ofthe maximum and minimum pressure amplitudes of the wave.

3.2 The effective acoustic power output of a treatment head is the timeaverage of the acoustic power, radiated by the treatment head in theforward direction into an approximately free field in water, under standardconditions ( see 6). It is expressed in watts.

3.3 The effective radiating area of a treatment head is 1011 times the areameasured at the treatment head face and using a particular circular bafflechosen to transmit 90 percent of the effective acoustic power as describedin 6.3.

3.4 The effective intensity of ultrasound radiated from a treatment head isthe quotient of the effective acoustic power output and the effectiveradiating area. It is expressed in watts per square centimetre ( W/cm%).

3.5 The maximum intensity of a treatment head is, by convention 4/n timesthe time average of acoustic power (at maximum setting of outputcontrols ) measured near the centre of the treatment head face and using acircular baffle, of 1 cm diameter.

4. SAFETY AND CONTROL FEATURES

4.1 A meter indicating effective acoustic power output (as defined in 3.2 ),or effective intensity ( as defined in 3.4 ), or both, shall be provided on thegenerator in the form of a meter or calibrated output control device.

4.2 Ultrasonic therapeutic equipment shall conform to the appropriatestandards for safety of operation.

*Electrotechnicalvocabulary : Part 3 Acoustics, Section 4 Sonics, ultrasonics andunder water acoustics,

4

5. TOLERANCES

5.1 The output meter or control d~effective acoustic power, or the effaaccuracy of + 15~o when the outp~and t 20% when the output is bet

5.2 During five hours of continuourated supply line voltage, in waterremain constant within + 15~@ofprovided with a power indicating m

IIA 15 to + 20~o after the first 30 m

5.3 The acoustic power shall not v:

1! of supply line voltage of + 5%. Nfor compliance with this requiremer

5.4 The actual frequency shall nonominal frequency.

5.5 Tests for compliance with 5.1; !treatment head has been immersed ]period of 48 hours.

5.6 The temperature of the treatduring 10 minutes radiation (at ma~transformer oil having an initial tenshall be at least two Iitres andexternal means. The temperature Kcouple attached in the centre of the

5.7 The effective radiating area shalvalue.

5.8 The maximum intensity shallvalue. The centre of the 1 cm diameintensity is found, shall lie within 1 (

[15.9 The quotient of the maximum

\!

exceed two.

6. CALIBRATION PROCEDURES

6.1 All measurements shall be maiinto an approximately free field ithat is degassed at 30 + 3°C acavitation occurs.

6.2 The -effective acoustic power ~preferably determined by the radiatif

IS :11701-1986

5. TOLERANCES

5.1 The output meter or control device specified in 4.1 shall indicate theeffective acoustic power, or the effective acoustic intensity, or both, with anaccuracy of & 15°/0when the output is greater than 50°/0 of the maximum,and * 20% when the output is between 10°/0and 50~0 of the maximum.

5.2 During five hours of continuous operation at maximum output and atrated supply line voltage, in water at 30 + 3°C, the acoustic output shallremain constant within + 15% of its initial value. If the apparatus isprovided with a power indicating meter, this variation may increase from

II+ 15 to -& 20’7(0after the first 30 minutes of operation.

5.3 The acoustic power shall not vary by more than + 10~o for variations

11 of supply line voltage of & 5%. No manual readjustment of the apparatusfor compliance with this requirement is permitted.

5,4 The actual frequency shall not differ by more than + 5~0 from thenominal frequency.

5.5 Tests for compliance with 5.1, 5.2 and 5.3 shall be conducted after thetreatment head has been immersed in tap water to a depth of 50 cm for aperiod of 48 hours.

5.6 The temperature of the treatment head face shall not exceed 450Cduring 10 minutes radiation ( at maximum setting of the output controls ) intransformer oil having an initial temperature of 30”C. The volume of oilshall be at least two Iitres ~d it shall not be agitated or stirred byexternal means. The temperature may be measured with a small thermo-couple attached in the centre of the treatment head face.

5.7 The effective radiating area shall be kept within ZE 10% of the ratedvalue.

5.8 The maximum intensity shall be kept within + 10% of the ratedvalue. The centre of the 1 cm diameter baffle at which the actual maximumintensity is found, shall lie within 1 cm of the centre of the treatment head.

115.9 The quotient of the maximum and the effective intensity shall not

1I

exceed two.

6. CALIBRATION PROCEDURES

6.1 All measurements shall be made with the treatment head operatinginto an approximately free field m water under standard conditions,that is degassed at 30 & 3°C and under conditions such that nocavitation occurs.

6.2 The effective acoustic Power .OUtPUt of a plane treatment head ispreferably determined by the radiation pressure method.

5

IS :11701-1986

6.3 The effective radiating area of a plane treatment head, as defied in 3.3,shall be determined by the use of circular baffles and by measurements ofthe effective acoustic power output. That baffle is found ( by interpolation,if necessary ) which transmits 900/. of the power measured without anybaffle. This baffle area is then multiplied by 1011 to obtain the effectiveradiating area.

6.3.1 The baffles shall consist of rings whose inner and outer surfaces areconical as shown in Fig. 1. The constituent material and design shall besuch as to provide a degree of acoustic insulation ensuring that the soundintensity transmitted through the baffle wall does not exceed 3°~ of theincident intensity. The baffle is bounded at the end which faces thetreatment head by the circular intersection of the inner and outer cone andthe diameter of this circle determines the baffle area. The other end of thebafle ( the base) shall have an outer diameter larger than the diameter ofthe radiating area of the treatment head to be tested. The baffles shall becentred on the face of the treatment head in such a way that the distancebetween the circular edge of each baffle and the face of the treatment headface < L A set of baffles shall be provided of diminishing diameters insteps of 5~o, starting from the diameter of the face of the treatment head.The number of baffles required depends on the type of treatment head andshould be sufficient to reduce the transmitted power to about 70°~ of thatproduced without baffle. In addition, a baffle of 1 cm diameter is neededto determine the maximum intensity.

7. LABELLING

7.1 Ultrasonic therapeutic equipment shall carry a nameplate, permanentlyattached, on which the following information shall be given:

a) Frequency of ultrasound in megahertz (megacycles per second);

b) Effective acoustic power output in watts at maximum settingof output controls;

c) Effective intensity in watts per square ccntimetre, at maximumsetting of output controIs; and

d) Wave form ( continuous, modulated or pulsed ).

7.1.1 The maximum intensity shall be indicated in the accompanyingpapers.

7.1.2 If modulated or pulsed, the output waveform, duty factor andrepetition rate shall be indicated in descriptive literature accompanying theequipment.

7.2 The effective radiating area of the treatment head (in square centi-metre ) shall be marked on its housing.

6

Ii

1/

/ //

/’,/[/////

LFIG. 1 CIRCULARBAFFLE(CR

APPE

( ClaTECHNIQUE O

A-1. Approximate free fieId condilbaffles, lining materials ( for exa]batting ), size and shape of tank, e

A-2. Degassing of water shall be afatmospheric pressure or by subject.than 30 mm of mercury for 3 houleast once within the 12 hours’ periunless special storage methods are

Ithroughout all procedures to minim

A-3. Cavitation may be avoided b:ultrasound intensity below that 1

IS: 11701-1986

FIG. 1 CIRCULARBAFFLE( CROSS-SECTIONTHROUGHA DIA~ )

APPENDIX A

( Clause 0.2)

TECHNIQUE OF MEASUREMENTS

A-L Approximate free field conditions may be obtained by use of suitablebaffles, lining materials ( for example, rubberized horsehair upholsterybatting ), size and shape of tank, etc.

A-2. Degassing of water shall be accomplished by boiling for 15 minutes atatmospheric pressure or by subjecting to a reduced pressure of not morethan 30 mm of mercury for 3 hours. Degassing shall be carried out atleast once within the 12 hours’ period preceding each set of measurementsunless special storage methods are used. In any case, care shall be takenthroughout all procedures to minimize re-solution of air in water.

A-3. Cavitation may be avoided by degassing the water and by keeping theultrasound intensity below that which produces cavitation. This latter

7

IS :11701-1986

procedure may occasionally require an extrapolation in calculatingmaximum output characteristics, It is then necessary to assume thatextrapolation is justifiable.

A-4. Radiation pressure measurements shall be made using a sensitiveelement which has a light-weight reflecting interface ( namely, thin metalfoil backed by air ) so arranged as to avoid standing waves. A cone orprism of 45” half-angle is convenient. The reflector shall be large enough tointercept the entire beam and its nearest point shall be placed between oneand three transducer diameters from the treatment head face.

A-5. It is preferable either to use compensating radiation meters, that is,radiation meters with which the measurements are made not on the basis ofdisplacement of a sensitive part but of the force required to return it to theinitial state, or to use devices in which the sensitive part is displaced in adirection parallel to itself and remains at a constant angle with respect tothe direction of ultrasonic emission. For example, a torsional spring or afloat may be used. Damping of the measuring system must be sufiient tointegrate the modulations of the radiation. The calibration shall be bymeans of standard weights. The effective acoustic power output, inwatts, is

w= ‘“c2 cos~ A

where

F = force exerted by the sound beam on the reflector alongthe beam axis,

c = velocity of sound in water, and

A = angle between the normal to the reflecting surface and thebeam axis.

The units for power, force and velocity are : watts, newtons andmetres per second in the MKSA system and ergs per second, dynes andcentimetres per second in the CGS system.

The numerical value of c at 30”C may be taken as 1510 m/s or151000 cm/s.

When the reflection coefficient of the reflecting interface differssignificantly from unity, the factor 2 in the denominator in the formula mustbe replaced by ( 1 + r ) where r is the intensity reflection coefficient. Ifthe force F is measured normal to the reflector, the denominator contains

cos A instead of COSZA.