In 1971 at the symposium of the German Physical Society, the first results were presented in which shockwaves, created using high velocity water drops and using a water filled, closed tube as waveguide, were able to destroy kidney stones [1].

The idea was further pursued using a light-gas gun and projectiles were fired with a velocity of up to 5 km/s on a metal target, which was connected to an open water recipient. The shockwaves produced in the target entered the water recipient, in which a stone had been placed. Depending on the form of the target, a straight or focused shockwave hit the stone. With a straight wave only small cracks were produced, however with the focused wave substantial fragmentation of the stone was achieved (Fig. 11.1c).

It had thus far been unknown to use shockwaves for therapeutic purposes. Substantial experimental and theoretical studies conducted by an interdisciplinary workgroup, consisting of members of the Department of Urology at the University Munich, the Institute of Surgical Research and Dornier, were therefore required prior clinical application. These studies started in January 1974 [2–8]. The substantial funding for this project, at the time considered as extremely high risk, came from the German Ministry of Research and Technology. Today a similar project would probably not receive public funding, thus such innovation would be impossible.

The costly physical trials could only be justified if there was a likelihood that the shockwave would not damage organs. For this reason the laboratory apparatus in the starting phase of the project was constructed for tests on vital structures (Figs. 11.2 and 11.3). The medical trials conducted were structured in two segments, in-vitro and in-vivo trials . The in-vitro experiments were aimed at determining if the delicate erythrocytes would be destroyed and if the process of erythrocyte proliferation were to be effected. The impact of the shockwave on abdominal and thoracal organs in a small animal were tested during the in-vivo experiments.

In a free standing water bath, probes with a standardized volume of 10 ml dog blood were adjusted into the focal point and the impact of the exposition to up to four shockwaves at 20 kV was studied. Increasing with the number of shockwaves was the concentration of serum haemoglobin to a level of 400 mg/100 ml. The increase seemed not to be relevant in comparison to the total blood volume of the animal. Later in a dog, despite a twentyfold shockwave exposure, no increase in the concentration of serum hemoglobin could be found.

The impact of the shockwave on the proliferative processes in a mixed lymphocyte model was compared to untreated cell cultures in the same way. The reactivity of the exposed lymphocytes did not differ to that of the untreated control group. A change in the stimulation capacity was not found.

For the in-vivo trials the test facility had to be modified. Instead of the water bath a bench was used, with which the shockwave could directly be coupled with the trial animal using a membrane. Using spacers the distance between the membrane and focal point was altered and allowed for the shockwave to act at a certain depth from the skin’s surface.

Narcotized rats were fixed to the bench and the thoracic and abdominal area randomly treated with ultrasound at 20 kV. Single shockwave exposure in the thoracic region caused massive lung trauma resulting in the deaths of the animals. This had not been entirely unexpected as the lung possesses other acoustic impedances as muscle or fat. These injuries were prevented by insulating the lung with air-filled materials which stopped the shockwave entering this part of the body. The animals survived ultrasound treatment of the abdominal area with ten shockwaves without any clinical side effects. Histological tests conducted 24 h and 14 days after the treatment showed neither macroscopic nor microscopic pathological changes [9].

Further trials focused specifically on the influence of shockwave exposure on the liver and intestine. The respective organs were eventerated, brought into focus and after successful exposure repositioned. After two exposures the intestine showed petechial bleeding. Massive haemorrhages or lesions of the intestinal wall never occurred. The liver also showed petechial bleeding. After 14 days no pathological alterations could be found on either organ (Table 11.1).