Ultrasonicbiophysicistsandphysicianshavecontinuouslyexhibitedgreatinterestinstudyingtheultrasonicpropertiesofblood.Itisshownthatcompressibilityofredcellappearstobeinverselypropor-tionalwithitshemoglobincontent.Amongultrasonicattenuationproducedbyredcellstructurelevelinblood,absorptionofredcellplayspredominantrole,viscousrelativemotionlossaccountsforlessthan15%,andcellscatteringcontributionisnegligible.Thecoagulationprocessofbloodisaccompaniedbysignificantchangeofsoundparameters.Themarkedadvantagehasbeenfoundintestofbloodcoagula-tionprocessbyusingultrasonictechniquethanthetraditionalviscousmethod.Bloodcoagulationcausessoundattenuation,soundbackscatteringandnonlinearityparameterB/Atoincrease,buttheattenuationfrequencydependencehardlychanges.Allofthesefindingsareofanimportantrealisticsignifi-cancefordevelopingultrasonicmedicine.
