E. Carr Everbach
Nimish Vakil
S. M. Gracewski
Rochester Ctr. for Biomed. Ultrasound, Univ. of Rochester, Rochester, NY 14627
Acoustic cavitation has been shown to play an important role in gallstone lithotripsy [Vakil et al., J. Acoust. Soc. Am. 90, 2340 (A) (1991)]. The bile surrounding a gallstone has been assumed to behave as a Newtonian fluid, with a viscosity independent of shear rate. Calculations show, however, that collapsing cavitation bubbles can produce shear rates nine orders of magnitude larger than those at which reported bile viscosities have been measured. Measurements of bile viscosity over a range of shear rates will be presented that show the non-Newtonian behavior of human bile, whose effective viscosity increases with shear rate. These results have implications for models of the behavior of collapsing cavitation bubbles during gallstone lithotripsy, and suggest the usefulness of clinical medical procedures that modify patients' bile viscosity prior to lithotripsy.