Formation of a Liquid Jet by Interaction between a Laser-induced Bubble and a Shock Wave.

There are some problems such as a narrow therapeutic time window and severe side effects of fibrinolytics in the therapy of cerebral embolisms. Therefore, it is necessary to develop a new method to remove a cerebral thrombus more rapidly with fewer fibrinolytics. A Q-switch pulsed holmium (Ho): YAG laser with 86 mJ/pulse, pulse duration of 200ns and wavelength of 2.1 mm was used. The laser beam was transmitted through a 0.6 mm diameter quartz optical fiber. Experiments were conducted in a stainless steel container equipped with observation windows . The test chamber was filled with distilled water at 283K. At first, the formation of laser-induced bubbles in a 4 mm diameter glass tube was observed. The bubble gradually expanded and reached a maximum size at about 1 ms after irradiation. A shock wave induced by ignition of silver azide pellet was interacted with it at 500mus before Ho:YAG laser irradiation, which resulted in forming a liquid jet. This liquid jet penetrated into an artificial thrombus made of gelatin, and its maximum penetration depth was 4.2 mm, which was nearly twice deeper than the laser irradiation only (2.2 mm). Combination of this liquid jet and fibrinolytics will realize more rapid recanalization with fewer drugs.