Underwater shock wave focusing is successfully applied to disintegrate and remove kidney stones or
gallbladder stones without using surgical operations. This treatment is one of the most peaceful applications
ofshock waves and is named as the Extracorporeal Shock Wave Lithotripsy. Ajoint research project is going
on between the Institute ofFluid Science, Tohoku University and the School ofMedicine, Tohoku University.
The paper describes a result of the fundamental research on the underwater shock wave focusing applied to
the ESWL. Quantitatively to visualize the underwater shock waves, various optical flow visualization
techniques were successfully used such as holographic interferometry, and shadowgraphs combined with
Ima-Con high speed camera. Double exposure holographic interferometric observation revealed the
mechanism of generation, propagation and focusing of underwater shock waves. The result of the present
research was already used to manufacture a prototype machine and it has already been applied successfully
to ESWL crinical treatments. However, despite of success in the clinical treatments, important fundamental
questions still remain unsolved, i.e., effects of underwater shock wave focusing on tissue damage during the
Model experiments were conducted to clarify mechanism of the tissue damage associated with the ESWL.
Shock-bubble interactions were found responsible to the tissue damage during the ESWL treatment. In order
to interprete experimental findings and to predict shock wave behavior and high pressures, a numerical
simulation was carried. The numerical results agreed with the experiments.