Simultaneous bubble sizing using multiple acoustic ...

from hugenumbersof infant microbubbles. Indeed,the "noises"havenow become"signals."The underwatersoundof breaking waveshasbeeninvertedto yield the spectrumof oceanwave heightand recentlythe underwatersoundof rainfall hasbeeninverted to revealthe real-timerainfall dropsizedistribution.The distinctivespectrumof underwatersoundduringrainfall evenallowsone to describethecloudsfrom whichtherain hasfallen.[Worksupported by ONR.] 8:40

3aPAa2.Acousticdetectionof inertialmicrocavitation from ultrasound. RonaldA. Roy (Appl.Phys.Lab.,Univ.of Washington, Seattle,WA 98195)

Recentyearshavewitnesseda growinginterestin processes governingthe nucleation,perpetuation, andphysicalconsequences of inertial microcavitationgeneratedby ultrasound.Fields as diverseas medicine,ultrasoniccleaning,and sonochemistry all rely, in varyingdegrees,on our ability to either inhibit, promote,or controlinertial cavitationactivity.Quantitative,spatiallyresolved assessment of suchactivity often requiresan ability to detectbubblesas small as a micronlastinglessthan a microsecond. This constitutes a technicalchallengethat hassoughtthe servicesof optical,electrical,and acousticaltechnologies. A review is presented of the stateof the art of spatiallyresolved,acousticmicrocavitation detectionschemes. This will includedescriptions of bothpassive

[Atchleyet al., Ultrasonics 26 (1988)]andactive[Royet al., J.Acoust.Soc.Am. 87, 2451(1990)]systems. Althoughthesesystems weredesigned to detectinertialmicrocavitation generated by microsecond pulsesof Megahertz-frequency ultrasound (similarto that utilizedin diagnostic ultrasound), thetechniques arequitestraightforward andgeneralizable to anysituation whereoneseeksto detect spatiallydiscretecavitationactivityin a reasonably homogeneous boundedliquid.Issuessuchasabsolutesensitivityandobservational

invasiveness arediscussed. [Worksupported by NIH throughGrantNo. RO1 CA39374.] 9:10

3aPAa3. Detection of cavitation during clinical extracorporeal lithotripsy. Andrew J. Coleman,Min J. Choi, and John E.

Saunders(MedicalPhys.Directorate, Guy'sandSt. Thomas'HospitalTrust,LondonSE17EH, England) A clinicalcavitationdetectionsystemhasbeendevelopedthat monitorsthe amplitude-timevariationof the 1-MHz componentof

thebroadband acoustic emission expected to accompany bubblecollapse duringclinicalextracorporeal shockwave lithotripsy [C. C. Church,J. Acoust.Soc.Am. 86, 215-227 (1989)].The detector is basedon a hand-held piezoceramic focalbowlhydrophone thatis acoustically coupled to thepatients' skin.A commercial electromagnetic positioning device(Fastrak, Polhemus Inc.,Vermont)is used to enablethe receptionzoneof the hydrophone to be directedunderultrasoundimageguidance.The systemhasbeentestedin the clinic by monitoringacousticemissionfrom positionsaroundthe beam focus of a clinical shockwavelithotripterduring routine lithotripsy.The detectedacousticemissionshowsfeaturescharacteristic of thoseobtainedfrom cavitationobservedin vitro and arises from withina regionof similardimensions to thatof thehyper-echoic regionthatcanbe simultaneously observedin theB-scanimage. The studyprovidesevidencethatacousticemissionfrom cavitationin tissuecanbe detectednoninvasively duringclinicallithotripsy. 9:40

3aPAa4.Simultaneous bubblesizingusingmultipleacoustictechniques.T.G. Leighton (Inst.of Sound& Vib. Res.,Univ. of Southampton, Highfield,Southampton SO17 1BJ,England) There existsa rangeof acoustictechniques for characterizing bubblepopulationswithin liquids.Eachtechniquehaslimitations, and completecharacterization of a populationrequiresthe simultaneous useof several,so that the limitationsof eachfind compensationin the others.An experimentis describedin whicha simplecontrolledbubblepopulationis subjectedto a drivingsignalat pump

frequency, top,anda second signalat theimagingfrequency, toi . Thepopulation is thensimultaneous examined usinggeometrical scattering, andresonance scattering of thefundamental frequency (top),second andthirdharmonics (2top, 3•%), andcombination frequencies (toi_ topandtoi_ •%/2).Comparison is madeof theease,accuracy, andspeed withwhichindividual techniques measure the population,and what advantages accruefrom their simultaneous deployment. 10:10-10:25

Break

ContributedPapers 10:25

3aPAa5.

Temperature-related

effects

in

single-bubble

sonoluminescence. SeanM. Cordry (YorkCollege,York,NE 68467), LawrenceA. Crum,andRonaldA. Roy (Appl. Phys.Lab., Seattle,WA 98105)

Bubblesacousticallylevitatedin the appropriateunderwatersound field can undergoradial motion which causesthe bubblesto be lumines-

cent,a phenomenon knownassingle-bubble sonoluminescence (SBSL).It hasbeenreported[Hiller et al., Phys.Rev. Lett. 69, 1182 (1992)] that coolingthe temperature of the waterby 20 øCcanincreaselight emission by a factorof 12.5. In this presentstudy,the acousticenergyradiatedby $BSL was measuredusinga needlehydrophoneand the numberof photons emitted by the bubble was measuredwith a photomultipliertube. Comparisons were madebetweenthe acousticand electromagnetic radiation emittedby the bubblefor a rangeof differenttemperatures andacous-

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J. Acoust.Soc. Am., Vol. 98, No. 5, Pt. 2, November 1995

tic pressures. Althoughthenumberof photonsemittedvariedstronglywith the temperature, the radiatedacousticenergydid not.Theseresultssuggest that it is the internalgasdynamicsand not the bubbledynamicswhich is

responsible for theobserved temperature-related effects.[Worksupported by theOfficeof NavalResearch.] 10:40

3aPAa6. Correlation of cavitation-induceddamage to blood elements with passiveacousticdetector output. E. Cart Everbach,Inder Raj S.

Makin (Eng.Dept.,Swarthmore College,500 CollegeAve.,Swarthmore, PA 19081),andCharlesW. Francis (StrongMemorialHospital,Univ.of Rochester,Rochester,NY 14642) A 20-MHz probetransducer placedconfocallywith a 1-MHz cavitation transducerwas usedto detectinertial cavitationin humanbloodprepara-

tions[Huertaset al., J. Acoust.Soc.Am. 95, 2856(A) (1994)].The prepa130th Meeting:AcousticalSociety of America

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