A compact underwater shock wave generator using magnetic pulse compression circuit for medical applications

Paper reports on production and focusing of micro-underwater shock waves for medical applications. Shock wave focusing has various scientific, industrial and medical applications. For precise shock wave therapies near sensitive organs, such as cranioplasty in the close vicinity of the brain, a micro-shock wave source is required. A half-ellipsoidal cavity with 20.0 mm minor diameter and the ratio of major to minor diameters of 1.41 was designed and constructed as an extracorporeal shock wave (ESW) source. Underwater shock waves were generated by electric discharge produced by a magnetic pulse compression circuit (MPC) and an electrode. Input voltage and input current were measured by using an oscilloscope and a current monitor. Pressure histories were measured at different stand-off distances by using a PVDF needle and a fiber optic probe hydrophones. A wide range of peak overpressures from 10 to 150 MPa at the focus was obtained, and small focal zone and focal energy flux density were measured. It is concluded that the present compact extracorporeal shock wave generator has appropriate characteristics for application in precise and sensitive medical procedures.