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Experimental study of micro shock wave focusing for precise medical applications

For applying shock waves to sensitive medical procedures like cranioplasty in a close vicinity of the brain or treatment of myocardial dysfunction, generation of micro underwater shock waves plays an important role. Such delicate applications make limits on usage of conventional shock wave (SW) sources. In the present research a half‐ellipsoidal cavity with 20.0‐mm minor diameter and the ratio of major to minor diameters of 1.41 was designed as a compact extracorporeal SW source. Silver azide AgN3 pellets ranging from 1.0 to 20 μg with their energy ranging from 1.9 to 38 mJ were used to generate shock waves at the first focal point F1 inside the reflector. Irradiation of a Q‐switched Nd:YAG laser beam through a 400‐μm optical fiber was used to ignite the pellet. The whole sequences of the shock wave generation, propagation, and focusing were visualized by quantitative double pulse holographic interferometry and time‐resolved high speed shadowgraph methods. Pressure histories were measured at the shock wav...