In situ detection of melanomas by fluorescence measurements

adhered was destroyed into small fragments. This was an addi t ional hint that stone destruction requires cavitation. Cavitat ion is dependent on the surrounding pressure of the medium. A static-pressure increase in the surrounding medium should decrease stone destruction by shock waves. This was tested in an experiment with a pressure chamber pressurized up to 100 atmospheres. Stones of similar weight from another gallstone family were exposed to 100 shock waves generated with 30 kV and 90 nF. Destruction was greatly reduced under 100 atmospheres in comparison to stones o f the same family destroyed in the chamber under atmospheric pressure (Fig. 2). The fact that the mechanism responsible for gallstone destruction must be located in the surrounding fluid, reinforces the theory that cavitation is responsible for stone destruction in these experiments. The results suggest that cavitation is necessary in the stone-filled gal lbladder and renal pelvis for stone destruction to occur in vivo. Cavitat ion in the gallbladder was easily detected by ultrasound during gallstone destruction in patients [10]. The results also explain why stones in the common bile duct are more difficult to destroy. They are largely surrounded by tissue which prevents cavitation f rom destroying them. Al though the results suggest that cavitation is the principal mechanism of gallstone destruction by extracorporeal shock waves they do not exclude that in other stone types and with different types o f shock waves other mechanisms are responsible for stone destruction.