Dynamic behavior of bubbles during extracorporeal shock-wave lithotripsy

Ultrasound-induced cavitation damage to external epithelia of fish skin

Transmission electron microscopy was used to show the effects of therapeutic ultrasound (< or = 1.0 W/cm2, 1 MHz) on the external epithelia of fish skin. Exposures of up to 90 s produced damage to 5 to 6 of the outermost layers. Negligible temperature elevations and lack of damage observed when using degassed water indicated that the effects were due to cavitation. The minimal intensity was determined for inducing cellular damage, where the extent and depth of damage to the tissues was correlated to the exposure duration. The results may be interpreted as a damage front, advancing slowly from the outer cells inward, presumably in association with the slow replacement of the perforated cell contents with the surrounding water. This study illustrates that a controlled level of microdamage may be induced to the outer layers of the tissues.

Liquid jets, accelerated thrombolysis: a study for revascularization of cerebral embolism

A prior study has reported that a rapid recanalization therapy of cerebral embolism, using liquid jet impacts generated by the interaction of gas bubbles with shock waves, can potentially penetrate through thrombi in as little as a few microseconds with very efficient ablation (Kodama et al. 1997). The present study was undertaken to examine the liquid jet impact effect on fibrinolysis in a tube model of an internal carotid artery. First, the conditions for generating the maximum penetration depth of liquid jets in the tube were investigated. Gelatin was used to mimic thrombi. The shock wave was generated by detonating a silver azide pellet weighing about a few micrograms located in a balloon catheter. The collapse of the inserted gas bubbles and the subsequent liquid jet formation were recorded with high-speed photography. Second, thrombi were formed using fresh human blood from healthy volunteers. The fibrinolysis induced by the liquid jet impact with urokinase was explored. This was conducted under selected conditions based on the experiment using the gelatin. Fibrinolysis was calculated as the percentage of the weight loss of the thrombus. Fibrinolysis with urokinase alone and with a single liquid jet impact with urokinase was 1.9 +/- 3.7% (n = 16) and 20.0 +/- 9.0% (n = 35), respectively, for an incubation time of 60 min. Statistical differences were obtained between all groups (ANOVA). These results suggest that liquid jet impact thrombolysis has the potential to be a rapid and effective therapeutic modality in recanalization therapy for patients with cerebral embolism and other clinical conditions of intra-arterial thrombosis.

Innovative technology for tissue disruption by explosive-induced shock waves

We have developed a novel, less invasive, shock wave source that can be introduced into an arbitrary position in a human body percutaneously. Using this technique we can disrupt cells locally. The shock wave source consists of an explosive, an optical fiber, a balloon catheter, and a Nd:YAG laser, which generates a spherical explosive shock wave. The destructive potential of the present source for injuring tissue was confirmed and the subsequent cell elongation and split in the direction of the shock wave has been observed.