In vitro evaluation of gallstone dissolution with methyl-tert-butyl ether and ultrasound energy

Given the large number of cholecystectomies performed annually, a nonsurgical approach to gallstone therapy is of great interest. A laboratory ultrasound system has been developed to study enhancement of methyl-tert-butyl ether (MTBE) dissolution of human gallstones in vitro. A mathematical model that quantitatively characterizes the dissolution process via a rate constant has been developed. Using this model, the kinetics of 15 gallstones from a single patient were evaluated for three dissolution methods: 1) unstirred MTBE, 2) aspirated MTBE, and 3) ultrasonically enhanced MTBE. The results showed excellent fits between the model and measured dissolution rates. 195 kHz continuous-wave (CW) ultrasonically enhanced dissolution rates exhibited a 6.2 fold gain over the manually aspirated MTBE and a 49.5 fold gain over static MTBE dissolution. Investigation of 50% duty cycle pulsed mode ultrasound revealed that total power appears to be the determinant of the observed dissolution rates. Gallstone calcification showed a strong correlation with dissolution rates measured by the model.