Ultrasonics - Pressure pulse lithotripters - Characteristics of fields

Applies to - lithotripsy equipment using extracorporeally induced pressure waves; - lithotripsy equipment producing focused mechanical energy. 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.

Ultraschall - Druckpuls-Lithotripter - Feldcharakterisierung

Ultrasons - Lithotripteurs à ondes de pression - Caractérisation des champs

Ultrasonics - Pressure pulse lithotripters -Characteristics of field (IEC 61846:1998)

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Status
Published
Publication Date
31-Aug-2002
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Sep-2002
Due Date
01-Sep-2002
Completion Date
01-Sep-2002

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Ultrasonics - Pressure pulse lithotripters -Characteristics of field (IEC 61846:1998)Ultraschall - Druckpuls-Lithotripter - FeldcharakterisierungUltrasons - Lithotripteurs à ondes de pression - Caractérisation des champsUltrasonics - Pressure pulse lithotripters - Characteristics of fields17.140.50ElektroakustikaElectroacoustics11.040.50Radiografska opremaRadiographic equipmentICS:Ta slovenski standard je istoveten z:EN 61846:1998SIST EN 61846:2002en01-september-2002SIST EN 61846:2002SLOVENSKI

STANDARD
SIST EN 61846:2002
SIST EN 61846:2002
SIST EN 61846:2002
SIST EN 61846:2002
SIST EN 61846:2002

INTERNATIONALSTANDARDIEC61846First edition1998-04Ultrasonics –Pressure pulse lithotripters –Characteristics of fieldsUltrasons –Lithotripteurs à ondes de pression –Caractérisation des champs Commission Electrotechnique Internationale International Electrotechnical

Commission IEC 1998
Copyright - all rights reserved

 Droits de reproduction réservésAucune partie de cette publication ne peut être reproduite niutilisée sous quelque forme que ce soit et par aucunprocédé, électronique ou mécanique, y compris la photo-copie et les microfilms, sans l'accord écrit de l'éditeur.No part of this publication may be reproduced or utilized inany form or by any means, electronic or mechanical,including photocopying and microfilm, without

permission inwriting
from the publisher.International Electrotechnical Commission3, rue de Varembé
Geneva, SwitzerlandTelefax: +41 22 919 0300e-mail: inmail@iec.ch IEC web site
http: //www.iec.chPRICE CODEUFor price, see current
catalogueSIST EN 61846:2002

– 2 –61846 © IEC:1998(E)CONTENTSPageFOREWORD...................................................................................................................3INTRODUCTION.............................................................................................................4Clause1 Scope.......................................................................................................................52 Normative references................................................................................................53 Definitions................................................................................................................64 List of symbols..........................................................................................................105 Conditions of measurement......................................................................................106 Test equipment.........................................................................................................116.1Test chamber.....................................................................................................116.2Hydrophone.......................................................................................................116.3Voltage measurement........................................................................................127 Measurement procedure...........................................................................................127.1Spatial measurements.......................................................................................127.2Temporal measurements...................................................................................147.3Acoustic energy measurements..........................................................................14AnnexesAAcoustic wave lithotripsy...........................................................................................16BTypes of pressure wave transducers.........................................................................18CField measurement...................................................................................................20DBibliography..............................................................................................................25SIST EN 61846:2002

61846 © IEC:1998(E)– 3 –INTERNATIONAL ELECTROTECHNICAL COMMISSION___________ULTRASONICS –PRESSURE PULSE LITHOTRIPTERS –CHARACTERISTICS OF FIELDSFOREWORD1)The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprisingall national electrotechnical committees (IEC National Committees). The object of the IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, the IEC publishes International Standards. Their preparation isentrusted to technical committees; any IEC National Committee interested in the subject dealt with mayparticipate in this preparatory work. International, governmental and non-governmental organizations liaisingwith the IEC also participate in this preparation. The IEC collaborates closely with the International Organizationfor Standardization (ISO) in accordance with conditions determined by agreement between the twoorganizations.2)The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, aninternational consensus of opinion on the relevant subjects since each technical committee has representationfrom all interested National Committees.3)The documents produced have the form of recommendations for international use and are published in the formof 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 InternationalStandards transparently to the maximum extent possible in their national and regional standards. Anydivergence between the IEC Standard and the corresponding national or regional standard shall be clearlyindicated in the latter.5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for anyequipment 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 subjectof 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:FDISReport on voting87/115/FDIS87/118/RVDFull information on the voting for the approval of this standard can be found in the report onvoting 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 caseroman bold type.A bilingual version of this standard may be issued at a later date.SIST EN 61846:2002

– 4 –61846 © IEC:1998(E)INTRODUCTIONExtracorporeal lithotripsy is used for the clinical treatment of renal, ureteric and biliary stones.Lithotripsy employs high-intensity acoustic waves to produce disintegration of the stonesthrough a process of sequential application of pressure waves. Several different forms oflithotripsy equipment are now commercially available from a number of manufacturers.This International Standard specifies methods of measuring and characterizing the acousticpressure field generated by lithotripsy equipment.SIST EN 61846:2002

61846 © IEC:1998(E)– 5 –ULTRASONICS –PRESSURE PULSE LITHOTRIPTERS –CHARACTERISTICS OF FIELDS1 ScopeThis 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 ofextracorporeal lithotripsy equipment,–methods of measurement and characterization of the pressure field generated bylithotripsy equipment.NOTE – The parameters defined in this International Standard do not – at the present time – allow quantitativestatements to be made about effectiveness and possible hazard. In particular, it is not possible to make astatement about the limits for these effects.While this particular standard has been developed for equipment intended for use inlithotripsy, it has been developed such that, as long as no other specific standards areavailable to be used for other medical applications of therapeutic extracorporeal pressurepulse equipment, this standard may be used as a guideline.2 Normative referencesThe following normative documents contain provisions which, through reference in this text,constitute provisions of this International Standard. At the time of publication, the editionsindicated were valid. All normative documents are subject to revision, and parties toagreements based on this International Standard are encouraged to investigate the possibilityof applying the most recent editions of the normative documents indicated below. Members ofIEC and ISO maintain registers of currently valid International Standards.IEC 60050(801):1994, International Electrotechnical Vocabulary (IEV) – Chapter 801: Acousticsand electroacousticsIEC 60866:1987, Characteristics and calibration of hydrophones for operation in the frequencyrange 0,5 MHz to 15 MHzIEC 61102:1991, Measurement and characterisation of ultrasonic fields using hydrophones inthe frequency range 0,5 MHz to 15 MHzSIST EN 61846:2002

– 6 –61846 © IEC:1998(E)3 DefinitionsFor the purpose of this International Standard, the following definitions apply.3.1 acoustic pulse energy3.1.1derived acoustic pulse energyspatial integral of the derived pulse-intensity integral over a circular cross-sectional area ofradius R in the x-y plane which contains the focusSymbol: ERUnit: joule, J3.1.2derived focal acoustic pulse energyspatial integral of the derived pulse-intensity integral over the focal cross-sectional areaSymbol: EfUnit: joule, JNOTE – This definition may overestimate E if the aperture of the pressure pulse generator is large.3.2beam axisline passing through the geometric centre of the aperture of the pressure pulse generator andthe focusNOTE – This line is taken as the z axis. See 6.1 and clause 7.3.3compressional pulse durationtime interval beginning at the first time the instantaneous acoustic pressure exceeds 50 % ofthe peak-positive acoustic pressure and ending at the next time the instantaneousacoustic pressure has that value (see figure C.1)Symbol: tFWHMp+ Unit: second, sNOTE – The subscript "FWHM" stands for "full width, half maximum".3.4derived pulse-intensity integraltime integral of the instantaneous intensity at a particular point in a pressure pulse field overthe pressure pulse waveform (see 3.31 of IEC 61102)Symbol: PIIUnit: joule per metre squared, J/m23.5end-of-cable loaded sensitivity of a hydrophoneratio of the voltage at the end of any integral cable or connector of a hydrophone, whenconnected to a specified electrical input impedance, to the instantaneous acoustic pressurein the undisturbed free field of a plane wave in the position of the acoustic centre of thehydrophone if the hydrophone were removed (see 3.14 of IEC 61102)Symbol: MLUnit: volt per pascal, V Pa–1SIST EN 61846:2002

61846 © IEC:1998(E)– 7 –3.6focal cross-sectional areaarea of the peak-compressional acoustic pressure contour which is –6 dB relative to thevalue at the focus and is in the plane, perpendicular to the beam axis, which contains thefocusSymbol: AfUnit: metre squared, m23.7focal extentshortest distance along the z axis that connects points on the –6 dB contour of peak-positiveacoustic pressure in the x-z plane on either side of the focusSymbol: fzUnit: metre, m3.8focal volumevolume in space contained within the surface defined by the –6 dB (relative to the value at thefocus) peak-compressional acoustic pressure contours measured around the focusSymbol: Vf Unit: metre cubed, m3NOTE – It is difficult to measure –6 dB points throughout the volume around the focus. It is reasonable in practiceto 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).3.9focal width, maximummaximum width of the –6 dB contour of p+ around the focus in the x-y plane which containsthe focusSymbol: fxUnit: metre, m3.10focal width, orthogonalwidth of the –6 dB contour of p+ around the focus, in the x-y plane which contains the focus,in the direction perpendicular to fxSymbol: fyUnit: metre, m3.11focuslocation in the pressure pulse field of the maximum peak-positive acoustic pressure3.12hydrophonetransducer that produces electrical signals in response to waterborne acoustic signals[IEV 801-32-26] (see also IEC 60866)SIST EN 61846:2002

– 8 –61846 © IEC:1998(E)3.13instantaneous acoustic pressurepressure minus the ambient pressure at a particular instant in time and at a particular point inan acoustic field (see also 801-21-19 of IEC 60050(801))Symbol: pUnit: pascal, Pa3.14instantaneous intensityacoustic energy transmitted per unit time in the direction of acoustic wave propagation per unitarea normal to this direction at a particular instant in time and at a particular point in anacoustic fieldFor measurement purposes referred to in this standard, where far-field conditions may beassumed, the instantaneous intensity, I, is expressed as:IpZ=2wherepis the instantaneous acoustic pressure;Zis the characteristic acoustic impedance of the medium.(See also 3.21 of IEC 61102.)Symbol: IUnit: watt per metre squared, W/m23.15lithotripsy equipmentdevice for disintegrating calculi and other concretions within the bodyNOTE – Known applications include renal stones, gallstones, pancreatic duct stones, salivary stones, orthopaedicpain and calcification in tendons.3.16peak-negative acoustic pressure, peak-rarefactional acoustic pressuremaximum of the modulus of the rarefactional acoustic pressure at any spatial location in thepressure pulse field (see 3.26 of IEC 61102)Symbol: p– Unit: pascal, Pa3.17peak-positive acoustic pressure, peak-compressional acoustic pressuremaximum compressional acoustic pressure at any spatial location in the pressure pulse field(see 3.27 of IEC 61102)Symbol: p+Unit: pascal, Pa3.18pressure pulseacoustic wave emitted by the lithotripsy equipmentSIST EN 61846:2002

61846 © IEC:1998(E)– 9 –3.19pressure pulse waveformtemporal waveform of the instantaneous acoustic pressure at a specified position in apressure pulse field and displayed over a period sufficiently long to include all significantacoustic information in the pressure pulse3.20pulse-pressure-squared integraltime integral of the square of the instantaneous acoustic pressure over the pressure pulsewaveformSymbol: piUnit: pascal squared seconds3.21rise timeat the focus, time taken for the instantaneous acoustic pressure to increase from 10 % to90 % of the peak-positive acoustic pressure (see figure C.1)Symbol: tr Unit: second, s3.22target locationlocation in space where the manufacturer intends the user to locate the calculi3.23temporal integration limits3.23.1positive temporal integration limitstimes between which the positive acoustic pressure first exceeds 10 % of its maximum valueand the first time it reduces below 10 % of its maximum valueSymbol: TPUnit: seconds3.23.2total temporal integration limitstimes between which the absolute value (modulus) of pressure pulse waveform first exceeds10 % of its maximum value and the last time it reduces below 10 % of its maximum valueSymbol: TTUnit: secondsSIST EN 61846:2002

– 10 –61846 © IEC:1998(E)4 List of symbolsAf:focal cross-sectional areaEf:derived focal acoustic pulse energyER:derived acoustic pulse energyfx:focal width, maximumfy:focal width, orthogonalfz:focal extentI:instantaneous intensityML:end-of-cable loaded sensitivity of the hydrophonep:instantaneous acoustic pressurep–:peak-negative acoustic pressurep+:peak-positive acoustic pressurepi:pulse-pressure-squared integralPII:derived pulse-intensity integraltr:rise timetFWHMp+:compressional pulse durationTP:positive temporal integration limitsTT:total temporal integration limitsVf:focal volumeZ:characteristic acoustic impedance of the medium5 Conditions of measurementMeasurements 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 (testchamber) which shall be large enough to allow the measurement environment to approximatefree-field conditions. If degassed water is not used, great care shall be taken to ensure thatbubbles do not collect on the hydrophone nor anywhere in the beam path.SIST EN 61846:2002

61846 © IEC:1998(E)– 11 –The conductivity of the water shall be suitable for the hydrophone being used. The calibrationof the hydrophone shall be known at the temperature of the water in the measuring tank.6 Test equipment6.1 Test chamberThe test chamber shall be a water tank constructed in a form that can be securely fixed to thepressure pulse generator so that the acoustic output from the pressure pulse generator iscoupled into a volume of water. The chamber shall be sufficiently large to allow the expectedposition of the focus to be several centimetres away from any reflective boundary, in particularthe water surface. The distance between the focus and reflective boundaries shall be chosensuch that no spurious or multiple reflections of the pressure pulse interfere with themeasurements.There shall be a suitable mechanical holder for the hydrophone which shall be mounted on acoordinate positioning system to allow adjustment and measurement of the position of thehydrophone in three orthogonal directions relative to the focus. One axis (z axis) of theco-ordinate positioning system shall be collinear with the beam axis. The relative position ofthe 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 themeasurements. The coupling media shall be as specified by the manufacturer.6.2 HydrophoneThe 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 hydrophoneThe focus hydrophone shall be equivalent to a single-film piezopolymer spot-poled membranetype 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 withthe 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 assmall as possible and its value shall be stated.NOTE – The lower frequency limit of current hydrophone calibration according to IEC 60866 and IEC 61102 is0,5 MHz. It would be desirable, however, for the purpose of the measurements described here to extend thehydrophone calibration to lower frequencies, at least to 0,2 MHz.6.2.2 Field hydrophoneThe field hydrophone shall have a robust construction and shall have a response which doesnot 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 assmall as possible and its value shall be stated.SIST EN 61846:2002

– 12 –61846 © IEC:1998(E)The sensitivity of the hydrophone shall not vary by more than ±10 % over the course of themeasurements.NOTE – Two different hydrophones are permitted because many of those suitable for measurements at the focusare 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 andnegative acoustic pressure readings of the high pressures encountered.6.3 Voltage measurement6.3.1 Oscilloscope or transient recorderThe device used to observe and measure the hydrophone output signal shall be appropriatefor the purpose, its frequency response and input capacitance and resistive impedance shall bereported. A digital oscilloscope with a sampling frequency greater than 100 MHz is thepreferred option, although a transient recorder and digital storage for subsequent computerdisplay may be satisfactory.The end-of-cable loaded sensitivity of the hydrophone shall be determined as specified in5.1.2 of IEC 61102, this value shall then be used to calculate the incident acoustic pressuresfrom the observed hydrophone output voltages.6.3.2 Pressure-pulse-waveform recordingThe output voltage waveform from the hydrophone shall be recorded in such a way as to allowthe measurement or calculation of:–instantaneous acoustic pressure, p;–peak-negative acoustic pressure, p–;–peak-positive acoustic pressure, p+;–rise time, tr;–compressional pulse duration, tFWHMp+;–instantaneous intensity, I.7 Measurement procedureThe measurements shall be made at least at one clinical setting as specified by themanufacturer. If only one setting is used, this setting shall be the maximum available forclinical application. The settings used shall be documented.Using the x-y-z coordinate positioning system, with the z direction being the beam axis, thefollowing 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 whichcontains the focus. The distance between the focus and the target location shall bedocumented. If the peak-positive acoustic pressure p+ in the target location does not differby more than 10 % of p+ in the focus, it is feasible to do the measurements in the x-y plane atthe z position indicated by the target location.7.1 Spatial measurementsThe 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 ofthe –6 dB isobar in the x-y plane. It shall be the lesser of 2 mm or 1/5 th of the maximumdimension of the –6 dB isobar in the x-z plane. If the values of p+ from sampling pointto 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 fieldhydrophone may be used.SIST EN 61846:2002

61846 © IEC:1998(E)– 13 –NOTE 1 – It may be worthwhile to perform measurements in the vicinity of the target location to locate the focusand 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 sothat the 6 dB measurements can be made without distortion.7.1.1 Beam plots of peak-positive acoustic pressureThe values of peak-positive acoustic pressure in the x-y plane which contains the focusshall 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 shouldalso be determined since the two curves are not identical and there can be significant differences between theareas 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 themaximum beam width.The variation of peak-positive acoustic pressure in x-z and y-z planes shall be measured andplotted at least as a –6 dB contour in each plane.7.1.2 Beam plots of peak-negative acoustic pressureThe values of peak-negative acoustic pressure in x-z and y-z planes shall be measured.These measurements shall be used to estimate the site and magnitude of the maximum peak-negative acoustic pressure.These measurements are very difficult to make in practice and the limits for spatial samplingintervals may be relaxed. If the difference in p– does not exceed 10 % from point to point, thesampling intervals may be chosen accordingly. The intervals used shall be declared.7.1.3 FocusThe separation of the focus and the target location shall be determined to a precision of±2 mm in the x and y directions and ±3 mm in the z direction.7.1.4 Focal widthThe width of the –6 dB contour in the x direction, focal width, maximum, fx, and in they direction, focal width, orthogonal, fy, shall be measured from the results derived from 7.1.1.7.1.5 Focal extentThe length of the –6 dB contour along the z direction, fz, shall be measured from the –6 dBcontour in the x-z plane derived from 7.1.1.7.1.6 Focal areaThe focal cross-sectional area along the x and y axes shall be established from the spatialdistributions.NOTE – It is reasonable to approximate the focal cross-sectional area to an ellipse with axes of lengths fx and fy.7.1.7 Focal volumeThe focal volume along the x, y and z axes shall be established from the spatial distributions.NOTE – It is reasonable to approximate the focal volume to an ellipsoid with axes of lengths fx, fy and fz.SIST EN 61846:2002

– 14 –61846 © IEC:1998(E)7.2 Temporal measurementsA focus hydrophone shall be positioned at the focus in such a way as to register the peak-positive acoustic pressure to a precision of ±20 %.The pressure pulse waveform shall be measured at the focus. The following parametersshall be derived:–peak-positive acoustic pressure and the peak-negative acoustic pressure;–compressional pulse duration;–rise time.7.3 Acoustic energy measurements7.3.1 Pulse-pressure-squared integralThe pulse-pressure-squared integral at any point (r, q) shall be given by:p(r,)p(r,,t) dti 2qq=òT(1)NOTE – The temporal limits over which integration is performed, T, should be stated and can be either Tp or TT.7.3.2 Derived pulse-intensity integralThe derived pulse-intensity integral at any point (r, q) shall be given by:PIIrZprtdtT(,)(,,)qq=ò12(2)NOTE – The temporal limits over which integration is performed, T, should be stated and can be either Tp or TT.This measurement shall be made with a focus type hydrophone.7.3.3 Derived focal acoustic pulse energyThe derived focal acoustic pulse energy shall be calculated from measurements of thederived pulse-intensity integral taken within the region of the focal cross-sectional area.The derived focal acoustic pulse energy may be calculated from:EZprtdSdtPIIrdSfTSS==òòò12(,,)(,)qq(3)NOTE – The temporal limits over which integration is performed, T, should be stated and can be either Tp or TT.wherep (r, q, t) is the instantaneous acoustic pressure at position (r, q) and time t;S is the surface lying in the plane passing through the focus and perpendicular to thebeam axis, with spatial polar coordinates r and q; bounded by the –6 dB contour.Z is the characteristic acoustic impedance of water (see annex C).SIST EN 61846:2002

61846 © IEC:1998(E)– 15 –7.3.4 Derived acoustic pulse energyThe acoustic pulse energy shall be calculated from measurements of the derived pulse-intensity integral taken within an area S defined as a circular cross-sectional area of radius R.EZprtdSdtPIIrdSRTSS==òòò12(,,)(,)qq(4)The value of R shall be specified and should be chosen to mimic a stone.SIST EN 61846:2002

– 16 –61846 © IEC:1998(E)Annex A(informative)Acoustic wave lithotripsyA.1

BackgroundRenal and ureteric stones are very common in many countries and in Western Europe theincidence is estimated at 3 % to 4 % of the population. To this figure must also be added thefrequent problem of gallstones.Conventional removal of renal, most ureteric and gall bladder stones involves a traumaticsurgical incision, which is associated with a hospital stay of one to three weeks and aprolonged convalescent period.Since about 1978 two new methods, percutaneous ultrasonic lithotripsy and extracorporeallithotripsy, have grown in importance and a large number of operations now involve one or theother of these methods. Both reduce or eliminate invasive surgery and greatly reducehospitalization and post-operational convalescence. Both procedures employ high intensityacoustic waves to produce disintegration of the stones.Early ultrasonic equipment for this application was based on continuous wave sources anddirect contact applicators. Extracorporeally induced stone destruction is usually carried outusing the application of sequential pressure waves. The use of laser techniques forpercutaneous lithotripsy has become important as another example of minimally invasivesurgery.In the 1990s increasing interest has been shown in the literature in evaluating the potential ofhigh intensity acoustic waves for the treatment of orthopaedic pain, delayed bone fracturehealing and calcifications of tendons.A.2

Percutaneous continuous wave systemsThe concept of the use of ultrasonic energy for stone disintegration was reported as early as1953 and practical work was carried out in the early 1970s. The slowness of the action hasprevented wide adoption of the method, although equipment is still produced.A.3

ExclusionsIt is not proposed to discuss percutaneous or semi-invasive systems, including laser lithotripsy,although the latter may be a combination of localized plasma and shock

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