Steven Dion

Shock Wave Generation through Constructive Wave Amplification

As new biomedical and industrial applications of shock waves emerge, the need to accurately and economically generate shocks is becoming more critical. Since a very large potential resides in biology and medicine areas for diagnostic and therapeutic uses, shock waves need to be efficiently produced in cells, tissues and organs. In the past, there have been a number of methods used to produce shock waves in liquids, all characterized by a large and rapid energy deposition, either through the detonation of an explosive, the irradiation of a target with a pulse of laser energy, the dumping of electricity through a spark gap, or the sudden acceleration of a piston, either by electromagnetic or piezoelectric means. There are well known shortcomings associated with each of these methods, such as the requirement for high-voltage electronics, the manipulation of explosives and/or the lack of control over the shock properties [1]. This paper presents a new method to generate highamplitude pressure pulses in liquids exploiting the advantages of low amplitude piezoelectric generators.

Comparison of methods for generating shock waves in liquids

We present two methods for producing high-amplitude pressure pulses in liquids. The electromagnetic generator, commonly used in lithotripters, is difficult to reduce in size, lacks complete control over the pressure pulse and requires high-voltage electronics. On the other hand, a time-reversal method is used to generate high-power acoustic pulses with a low-power electronic piezoeletric transducer.

TCT-839 Acute safety and technical performance evaluation of a novel CTO-crossing device based on a shock wave-energized guidewire

TCT-838 Effects of Oversizing on Neointimal Formation after Self-Expanding Bare Metal Stents in Porcine Femoral Arteries Atsushi Sakaoka, Hitomi Hagiwara, Norihiko Kamioka, Serge Rousselle, Armando Tellez Terumo Corporation, Kanagawa, Japan; Division of Cardiology, Department of Medicine and Clinical Science, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan; Emory University; Alizee Pathology, Thurmont, Maryland, United States; Alizee Pathology, Thurmont, Maryland, United States

Characterization of Calcified Plaques Retrieved From Occluded Arteries and Comparison With Potential Artificial Analogues

Cardiovascular disease is the leading cause of death worldwide. This disease includes chronic total occlusion (CTO), which is a complete blockage of an artery. Unlike partial occlusions, CTOs are difficult to cross percutaneously using conventional guidewires (thin and flexible wires) because of the fibrotic and calcified nature of the blockage. The lack of data regarding the mechanical properties of CTO limits the development of new technologies in the field of percutaneous coronary intervention (PCI) and percutaneous peripheral intervention (PPI). In this study, calcified plaques retrieved from occluded arteries are analyzed in order to better understand their mechanical properties and to help propose an artificial analogue. Calcified plaques samples were collected from the superficial femoral artery wall within one hour following a lower limb amputation surgery. These samples were studied to determine their composition and mechanical properties. The same characterization procedures were performed on various potential artificial analogues. These analogues include three plaster materials and dense hydroxyapatite blocks. The results were then compared with those of the calcified plaques in order to determine the more favorable analogue. This mechanical analysis and the proposal of a potential analogue for the calcified plaques found in occluded arteries could benefit the development of new technologies and devices in the field PCI and PPI.Copyright

High-Intensity Targeted Cavitation as a More Efficient and Safer Approach to Treat Kidney Stones

An apparatus to provide a safer and more efficient non-invasive treatment of kidney stones is under development. The proposed non-invasive alternative is to produce a tightly focused high-intensity cavitation cloud right at the stone; the cloud being electronically steerable in real time to compensate for the respiratory movements which would significantly reduce the exposition of healthy tissues to damaging shock waves. The piloted cloud is produced by 19 independent novel shock wave generators that are geometrically oriented towards a single focal point. The real-time steering is accomplished by applying different emission delays between the shock wave generators. The steering capability of the 19-channel prototype was monitored in vitro using a pressure sensor and kidney stone analogs. Promising tests were also conducted on ex-vivo pigs to measure the erosion rate of implanted artificial kidney stones.Copyright

A passive dispersive wave amplifier for high-intensity broadband acoustic pulses

The acoustical power output of piezoelectric ultrasonic transducer is limited by the material breakdown voltage or the available driving electrical power. While there are well known ways to passively amplify monofrequency acoustic waves generated by a single transducer, e.g., with an exponential horn, there is no obvious way to similarly pump energy into a structure to produce high-intensity broadband acoustic pulses. It was found that the frequency dependant phase velocity inherent to dispersive waveguides can be advantageously exploited to generate high intensity planar pulse waves using a single transducer. With this amplification concept, gain factors as high as 15 have been measured, which can be exploited to produce shock waves in water with a conventional ultrasonic transducer and low power electronics. The paper will present the theoretical underpinnings of this method, as well as its experimental validation. Some potential biomedical applications of this technology will also be discussed.