Biological effects of tandem shock waves on soft animal tissues – preliminary “in vivo” experiments

We have investigated biological effects of two successive (tandem) shock waves focused to a common focal region on soft animal tissues, including cancer tissues "in vivo" and cancer cells "ex vivo". The tandem shock waves have been produced by our formerly developed shock wave generator where two cylindrical pressure waves are focused by a metallic parabolic reflector to a common focal region and the second shock can be switched on with a different time delay after the first one. The idea on application of the tandem shock waves is to localize the action of the shocks at a predictable region in an initially acoustically homogenous medium such as cancer tissues are. The first shock creates in the tissue some acoustical non homogeneity and cavitations, and the second shock dissipate on it, similarly as it is in the case of the lithotripsy of kidney stones. We have found that at some time interval between the shocks (10-15 Icircfrac14s) the second, originally pressure wave, reaches the focus as a rarefaction wave that produces a large number of cavitations. Collapsing cavitations create secondary, very short wavelength shocks which can interact with cell scale structures. We have demonstrated that the tumors from cancer cells exposed to the tandem shocks grow much slowly. We know that the tandem shocks locally injure a healthy tissue of a rabbit liver . In this work we will present results on synergistic effect of the tandem shocks and hematoporphyrin on the growth rate of tumors on laboratory rats. Preliminary experiments show that the combined therapy of shock waves with hematoporphyrin (i.e., sonotherapy) should be applied in the initial stage of the tumor development.