Measurementofcyclicmicrodefbrmation

Ofarterialwallwithpulsatileflow

ShigehiroHa5himoto＊8，ShirouManabea，KazuhiroIkegamia，YbshinoriMurashigea，Chiaki

Miyamotoa，MasayoshiOmoria，Rei3iHattorib，H毎imeOtanib，HirqjiImamurab
aBiomedicalSystems，Dept．ofElectronics，InformationandCommunicationEngineering，

OsakaInstituteofTeclm0logy，
bDept，OfThoracicandCardiovascularSurgpery，KanSaiMedicalUmiversity
ABSTRACTThe cyclic micro−deformation ofthearterialwal1with pulsatile now was measured to get鮎ndamentaldata fbr
estimationofthemechanicalstressinendothelialcells．Thedescendingaorta（1−2mmdiameter）ofananesthetizedrat

WaSeXPOSedunderthoracotomy．Thedisplacementmeasur1ngSyStemWaSaSSembledwiththechargecoup】edde（CCD）oflasersensor・Themovementoflaserbeam（670rLmWaVelength）reflectedattheveモSelwallwascalibratedto

themovementofthearterialwall・ThenuctuatingmovementwasalsomeasuredatfourpolntSmarkedonthevess
WallwithCCDcameratodistinguishthecircumftrentialmovement丘omthelongitudinalone．Theresultsshowedthat
thepresentdesignedsystemhasenoughresolutiontomeasurethearterialvesselwallcyclic−micro−fluctuation，Whichis

lOpercentofdiameterinthecircumftrentialdirectionwithoutdeformationinthelongitudinaldirectionwiththecardiac
beatlngJ〃Ⅴル仇

Keywords：Biomeasurement，Pulsatingdeformation，Pulsatileno叫arterialwal1，CCDlasersensor，mOCkcirculation，
diaphragmpump
l．mTROI）VCTION

Thebloodtlowcausesmechanicalshearandtensilestressesinavesselwall・Theinnersurfac？Ofthevesselwallis
coveredwithendothelialcells・Theendothelialcellsaresecretingchemicalagentsandcontrollingthrombusformationl・Previousstudiesshowthattheendothelialcel15areSenSitivetomechanicalstress2・4・Thequantitativerelationbetween
mechanicalandbiological血ctorsremains，however，underdiscussion．Thepulsatileflowmaycausedi蝕renteffbctson
theendothelialcells＆omthesteadynow5・Thepresentstudyshowsthemethodologytomeasurethecyclicmicro−
deformationofthearterialwal1withapulsatilenowtogivefundamentaldataforestimationofstressinvesselwalls・
2．METHOI）S

2．1MeasurementsystemwithCCDlaser
Tomeasurethecyclicmicro−deformationofthearterialwallwithpulsatilenow，thedisplacementmeasurlngSyStem
Wa5aSSembledwiththechargecoupleddevice（CCD）oflasersensor（Figs．1＆2）．Themovementoflaserbeamof670
nmwavelengthrenectedatthevesselwalliscomputedandcalibratedtothemovementofthewal1・Themovementi
Calculatedintothe nuctuation ofdiameterOfthe vessel，Whichis負xed atthe opposite5idewith the L bar・The

measurementsystemdistinguishesO．02mmfluctuationinthediameterOfthevessel．Intheexperimentalsystem，thesimultaneousmeasurementofinstantaneOusnOWrateenablestocorrelatethedeformationofthewall料iththephiseofPulsatilenow．
一 contact．hasimoto＠elc．oit．acJp；Phone ＋81−6・69544608；払x ＋81・6−69572136；h叩：／／www．oit．acJp；BiomedicalSy5temS，

DepaTtmentOfElectronics，hfbrmationandCommunicationEngineerlng，OsakaInstituteofl七chnology，5−16−1，Ohmiya，Asahi−ku，Os止a535−8585，Japm

456

LasersinSurgery：AdvancedCharacterLzation，Therapeutics，andSystemsXll，KennethE・Bartels，etaI．．Ed托drs，ProceedingsofSPIEVol．4609（2002）⑥2002SPIE・1605−7422／02／＄15・00

aortaFig．1：ChaTgeCOupLeddevise（CCD）oflasersensor・

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Fig，2：Measurementonmovementofthewa11withCCDlaser．

Longitudinal
毒＞
Bloodnow→

Descending aorta

Fig．3：FourpolntSmarkedonthevesselwall・Fig．4：Measurementsy5temwith1aser；electromagneticnowmeteちright；animalandla5erdevice，Center；reSpLratOr・1e允▼458

Proc．S円EVol．4609

Flow meter

CCD Laser

Fig・5：Measurementprocedureinvivo，Figure6：Reciprocatlng・micro・di8Phr8gmpumPSyStern．

2・2MeasurementsystemwithCCDc＆血er且Thefluctuatingmovementwasalsomeasured衰fourpolntSmarkedonthevesselwallwiththechargecoupleddevise（CCD）cameratodistinguishthecircumftrentialmoYementfromthelongitudinalone．Thefburpoint5are］ocatedto

makeasquareoflrnm．Eachdiagonallineofthesquarecoincideswiththecircumferentialorlongitudinaldirectionof
thevessel（Fig．3）．

2・3Measurementprocedure

Ratswerechosenfortheanimaltobehandledinalargenumber（thirty−tWOratS）oftests．Thedescendingaortaofan
aneSthetizedratw85CXPO5edandexfoliatedfrom5urrOundingtissueunderthoracotomywithresplratOrOf60beatperminute（Fig・4）・Themcasurementsofcyclicdeformationofar（eri81wallwereperformedatthedescendingaorta・The

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ChamberResistance

CCD laser

Figure7：Mockcirculationcircuit．

nowratewasmeasuredataortawiththeelectromagneticnowmeter・ThebloodpressureWaSmeaSuredatthebranchof
aorta with the catheterand diaphragm method（Fig．5）．Temperature ofthe rectumis maintainedヾat th叫′−SeVen

CentigradewithalagglngpaCk・TbcontrolthemeandiameterOfthedescendingaortaandthecomplianceofthevessel
Wall，fb1lowingliquidswereintroducedthroughthevenous；thesalinesolution，thevasodilatationagent（nitroglycerin），
Orthevasoconstrictionagent（dopamine）．
ヱ・4Me且SurementprOCedure・血γか〃Thedescendingaorta，OfwhichbranCheswereligated，aSlongaslOmmwasexcised丘・Omaratandcormectedtothemockcirculationcircuit．Theexcisedaortasegmentwassunkinasalinesolutioncontainedinachamber．Pulsatile
Saline−SOlution−nOW pOWered by the reciprocating−micro・diaphragm pumP（Fig．6）was applied to the excised

descendingaorta，andmeasuredthenuctuatingmovementofthevesselwall（Fig．7）．Thepumpsystemconsistsofa
battery，aDCmotor，aCrank，adiaphragmchamber，andleafletone−WayValves．ThenowconditionwascontroILedto
Simulatethatwiththenaturalhear（Ofrats；beatingrateof300perminute，StrOkevolumeofO．06mlwiththediaphrag
PumP．V訂iationsweremadeinthedistalresistanCewithconstrictLngthesiliconetube，Whichwasconnectedatthe

downstreamofthemockcirculation．Thenowrateandthepress岬eWeremeaSuredwiththeelectromagneticflowmeter
andwiththecatheter・diaphragmmethod，reSpeCtively・A鮎rthetest，thediameterandthewallthicknessofthevess
WeremeaSuredwithascale．

3．RESmS

Fig．8exempli丘esthetracmgsofthedeformationofthearterialwallandthebloodflowratewiththepulsatilenowin
Vivo・ThetraclngShowsO・2mmcyclicsinusoidalfluctuationofthevesseldiameterwiththecardiac beatlng・The

PulsatlngValueisestimatedtotenpercentofthemeandiameterOfthedescendingaorta．Themovementobservedwith
theCCDcameraindicatesthatthevesselwalldeformsatcircumfbrentialdirection，andthatthewalldefbrmsbelowone
perCentOfthemeandiameteratlongitudinaldirection．neresultsofthirty・tWOanimaltestsshowthatthe・rateOf
deformationatcircumfbrentialdirectionwithcardiacbeatingis丘・Om5to10percentofthemeandiameter・Wtlenthevasodilationagent（nitroglycerin）isintroducedintothecirculationinthetestsinvivo，the bloodvolume
movestotheperipheralcirculationbytelangiectasia．ThisdecreasedthemeandiameterOfaorta，andincreasedthera
Offluctuationofitsdiameterwithcardiacbeating（Thblel）．Whenthesalinesolutionisintroducedintothecirculation，

thecirculatingbloodvolumeexpanSionincreasesthemeandiameterOfaorta．Infusionofdopaminealsoexpandsthe
meandiameterofaorta，becauseofthemovementofblood丘omperipheralcirculationbytheefftctofvasoconstriction・

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Diameter，mm

Oq．2

0．1

0▲00」

1】．2

l．4

川用

2Ti皿e，S

Figure8：Tracingsofthedeformationofthearterialwallandbloodflowratewiththepulsatilenow・Thblel：Themeanvesseld血nctcrandtherateofitsfluctuation．

Before infusion

After infusion

Infusedliquid Vesseldiameter Rateofnuctuation Vbsseldiameter Rateofnuctuation
Salinesolution l．40mm
Dopamine
l．70mmNitroglycerinl．78mm

1．60mm
1．75mm
1．56mm

5．5％
4．2％
4．2％

7．8％
5．5％
lO．6％

TheresuLtinvttroshowsthattherateoffluctuationdependsonthemeandiameter，Whichrenectstensilestressinthe
Wallattheneutralinthecardiaccycle．Whenthevesselwallisstronglystretchedatneutral，itbecomeshard・This

decreasestherateoffluctuationofthevesselwal1withthephaseofpulsatileflow．Whenthevesselwa11issoftly

stretchedatthenatural，Ontheotherhand，itbecomesflexible．Thisincreasestherateoffluctuationofthevesselwal
withthebeatingofthepulsatilepump・ThemeanValuesofouterdiameterandofthewallthicknessofthevesselwere2
mmandO．15mm，reSpeCtively．

4．DISCUSSION

Themicrodeformationofthevesselwal1shouldbemeasuredwiththesensoroutofcontact，becausethevesselwallis
COmPliant．Boththeultrasoundandlightbeamsaregeneral1yusedfbTthemediatomeasurethedistancebetweenthe

sensorandthesurfacewithoutcontacteachother．Theresolutionofmeasu代mentdependsonthewavelengthofth
renectedbeam．

UltrasonographiswidelyusedinthemedicalmeasuTement・Itenablesmeasurementofmovementoftheinterfaceinthe
bodynon−invasiYely・ThenormalleveldevicedistinguishesthedistanCeOfO・1mm6・

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TheCCDcameraisusefu1togetthemovingimageofthesurface．TheadvantageOflaser（1ightamplification
Stimulatedemissioヮofradiation）beamsisitsuniformityaboutbothphaseand＆equency・TheCCDlasersensor

COnSistsofthesemlCOnductorlaserandtheCCDelement．Thelaserbeamreflectedatthes11rfacefbcusesontheCCD
element・Asthemovementofthesurface，theangleofthereflectedbeamvaries．ThevariationoftheanglecorrespondtothatofthefocusedpositionontheCCDelement．
BeingcompaTedwiththeultrasonographorthechargecoupleddevise（CCD）camerチSyStemS，thepresentmeasur享ng

亭yStemWiththeCCDoflasersensorhastheadvantagedboutthedynamicresolutlOntOdistinguishthenuctuat
micro−deformationofarterialwallswiththecardiacbeating・Forexample，themeasurlngSyStemispreftrabletoapply
toanarteryofsmalldiameter．

TheresultsshouldbeappliedtosimulatecomplianCeOfarterialvesselwal17・ThecyclicvariationofdiameterisuseftoestimatefluctuatlngStreSSinvesselwallwithpulsatilenow・Theefftctsofpulsatileflowonmechanicalstressin

endotheLialcellsofarterieshavenotbeenquantined8−TOt

Inthepresenttestsinvivo，SurrOundingtissuearoundthedescendingaortaisexfbliated．ThesurroundingtlSSuema
havesomeminore飴ctstothecomplianCeOfthevesselwall．

Thesurroundingpressureinthethoraxalsoafftct5thedeformationofthevesselwallofthedescendingaortabefbre

thoracotomy・Thepressureperiodicallyfluctuateswithresplration，Thenegativesurroundingpressureincreases
meandiameterofthevessel，WhichdecreasesthecomplianCeOfthevesselwall．

Thepulsatileflowmodinesthestressinthevesselwall．Boththeshearstressonthewallandtensilestressinthewall

nucttlateperiodically・Thepresentstudyshowsthattensilestressgeneratesmainlyinthecircumfヒrentialdirectionofthe
VeSSelwall．Thestressmaycausevariouse飴ctsinendothelialcells10．ThepulsatileflowalsomayplayanimportantroletocontroIclotfbrmation5．
5．CONCLVSION
Thepresentstudyshowedthatthedesignedsystemhasenoughresolutiontorneasurethearteria】vesselwallmicro−

fluctuation，WhichislOpercentofdiameterinthecircumftrentialdirectionwithoutdefbrmationinthelongitudinal
directionwithpulsatilenows．
ACKNOWLEDGMENTS
ThisworkwassupportedinpartbyaGrant−in−AidforScientif王cResearch丘omtheJapaneSeMinistryofEducation，Culture，Sports，ScienceandTtchnology．
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