Focused Shock Waves in Liquids

Principles and Research Objectives

Shock waves generated by discharge plasma in water are investigated, their physical and biological effects and the possible use of focused shock waves in biomedicine. This research continues the tradition of very succesful application of underwater shock waves for non-invasive disintegration of kidney and urinary track stones and galstones used in extracorporeal shockwave lithotripsy (ESWL). At the end of 1980s we have developed one of modified versions of the electrohydraulic type of ESWL device (lithotripter), which is based on generation of shock wave using a high current spark discharge in water. The treatment involves generation of shock waves by the lithotripter outside of the patient’s body and focusing them on the stone at a depth in tissue. Hundreds to thousands of shock wave pulses are delivered to comminute the targeted stone. After the urinary stone treatment, the stone debris passes through the urinary tract (see figure below). These generators are used in the lithotripters Medilit (MEDIPO, Czech Republic) at approximately 20 hospitals in the Czech and Slovak Republics with more than 120 000 patients treated.

Today our main attention is paid to applications of focused shock waves in oncology. There is, however, a fundamental difference in treatment of kidney stones and in a possible treatment of cancer tissues. Shock wave propagates through soft tissues with very a small attenuation almost without interaction with them and there is no difference in acoustical properties of cancer and healthy tissues. Great attention is paid to the role of cavitation and special generators of shock waves are being designed to modify the cavitation field and to control cavitation, e.g. by timing between pulses or using so-called tandem shock waves, which intensify the collapse of cavitation bubbles by sending a second shock wave at the moment before the bubbles produced by the first shock wave begin to collapse.

For this purpose we have developed a novel generator of focused shock waves in water (FSW), which is based on the production of cylindrical pressure waves generated by underwater multichannel electrical discharges using one or two porous ceramic-coated (composite) cylindrical metallic electrodes. The primary pressure waves generated by the underwater plasma channels at the surface of the composite electrode(s) in highly conducting water (15-20 mS/cm) are focused by a metallic parabolic reflector to a common focal point and only close to the focus are transformed into a strong shock wave. Dividing the composite cylindrical electrode into two coaxial parts of different diameter and surface area it is possible to generate two successive shock waves (i.e., focused tandem shock waves, FTSW). Under these conditions the second pressure wave is highly attenuated at the focal region due to acoustic perturbations created by the first wave resulting in the formation of strong rarefaction shock wave at the focus. The amplitude of the pressure wave is up to 100 MPa, while the amplitude of the rarefaction wave falls down up to -80 MPa, which creates a very complex pressure field and a large number of cavitation at the focus.

In cooperation with leading medical institutions in the Czech Republic we are exploring biomedical effects of focused tandem shock waves in vitro and in vivo and at international level we cooperate within the International Bioelectrics Consortium. These focused tandem shock waves were demonstrated to strongly interact with cell scale structures and to cause localized lesions at a predictable location deep within soft tissue at the focus without damaging tissue located in front of the focal point. Research on possible application of FTWS for cancer treatment and controlled drug delivery is under way. It has been proven in vivo that FTSW can delay tumor growth and enhance antitumor effect of chemotherapeutic drugs such as cis-platinum. The use of photo- and sono-sensitive substances in combination with shock waves is also being investigated in order to enhance efficiency of chemotherapy treatment of cancers.

Publications

1. Lukeš P., Zeman J., Horák V., Hoffer P., Poučková P., Holubová M., Hosseini S.H.R., Akiyama H., Šunka P., Beneš J. (2015) "In vivo Effects of Focused Shock Waves on Tumor Tissue Visualized by Fluorescence Staining Techniques" Bioelectrochemistry 103: 103-110 [Abstract] [LINK]
2. Lukeš P., Šunka P., Hoffer P., Stelmashuk V., Poučková P., Zadinová M., Zeman J., Dibdiak L., Kolářová H., Tománková K., Binder S., Beneš J. (2014) "Focused Tandem Shock Waves in Water and their Potential Application in Cancer Treatment" Shock Waves 24 (1): 51-57 [Abstract] [LINK]
3. Lukeš P., Šunka P., Hoffer P., Stelmashuk V., Beneš J., Poučková P., Zadinová M., Zeman J. (2012) Generation of Focused Shock Waves in Water for Biomedical Applications, In: Plasma for Bio-Decontamination, Medicine and Food Security, Series NATO Science for Peace and Security Series – A: Chemistry and Biology, Chapter 31, (Eds. Z. Machala, K. Hensel, Y. Akishev), Springer, ISBN 978-94-007-2851-6, p. 403-416
4. Stelmashuk, V., Hoffer, P. (2012) "Shock Waves Generated by an Electrical Discharge on Composite Electrode Immersed in Water with Different Conductivities" IEEE Trans. Plasma Sci. 40: 1907-1912 [LINK]
5. Beneš J., Zeman J., Poučková P., Zadinová M., Šunka P., Lukeš P. (2012) "Biological Effects of Tandem Shock Waves Demonstrated on Magnetic Resonance" Bratislava Med. J. 113 (6): 335-338 [Abstract] [LINK]
6. Beneš J., Poučková P., Zeman J., Zadinová M., Šunka P., Lukeš P., Kolářová H. (2011) "Effects of Tandem Shock Waves Combined with Photosan and Cytostatics on the Growth of Tumours" Folia Biol. 57 (6): 255-260 [Abstract] [LINK]
7. Šunka, P., Stelmashuk, V., Babický, V., Člupek, M., Beneš, J., Poučková, P., Kašpar, J., Bodnár, M. (2006) "Generation of Two Successive Shock Waves Focused to a Common Focal Point" IEEE Trans. Plasma Sci. 34: 1382-1385 [LINK]
8. Stelmashuk, V., Šunka, P. (2006) "Mutual Interaction of Two Shock Waves with a Different Time Delay" Czech. J. Phys. 56: B396-B400 [LINK]
9. Šunka, P., Babický, V., Člupek, M., Beneš, J., Poučková, P. (2004) "Localized Damage of Tissues Induced by Focused Shock Waves" IEEE Trans. Plasma. Sci. 32: 1609-1613 [LINK]
10. Šunka P., Babický V., Člupek M., Fuciman M., Lukeš P., Šimek M., Beneš J., Locke B. R., Majcherová Z. (2004) "Potential Applications of Pulse Electrical Discharges in Water" Acta Phys. Slovaca 54 (2): 135-145 [Abstract] [PDF]