The application of strong electric fields in water and organic liquids has been studied for several years, because of its importance in electrical transmission processes and its practical applications in biology, chemistry, and electrochemistry. More recently, liquid-phase electrical discharge reactors have been investigated, and are being developed, for many environmental applications, including drinking water and wastewater treatment, as well as, potentially, for environmentally benign chemical processes. This paper reviews the current status of research on the application of high-voltage electrical discharges for promoting chemical reactions in the aqueous phase, with particular emphasis on applications to water cleaning.

/pdf/electrohydraulic-discharge-and-nonthermal-plasma-for-water-bcogyk507r.pdf

Electrohydraulic Discharge and Nonthermal Plasma for Water Treatment

Ultrasound is an inexpensive and widely used imaging modality for the diagnosis and staging of a number of diseases. In the past two decades, it has benefited from major advances in technology and has become an indispensable imaging modality, due to its flexibility and non-invasive character. In the last decade, research investigators and commercial companies have further advanced ultrasound imaging with the development of 3D ultrasound. This new imaging approach is rapidly achieving widespread use with numerous applications. The major reason for the increase in the use of 3D ultrasound is related to the limitations of 2D viewing of 3D anatomy, using conventional ultrasound. This occurs because: (a) Conventional ultrasound images are 2D, yet the anatomy is 3D, hence the diagnostician must integrate multiple images in his mind. This practice is inefficient, and may lead to variability and incorrect diagnoses. (b) The 2D ultrasound image represents a thin plane at some arbitrary angle in the body. It is difficult to localize the image plane and reproduce it at a later time for follow-up studies. In this review article we describe how 3D ultrasound imaging overcomes these limitations. Specifically, we describe the developments of a number of 3D ultrasound imaging systems using mechanical, free-hand and 2D array scanning techniques. Reconstruction and viewing methods of the 3D images are described with specific examples. Since 3D ultrasound is used to quantify the volume of organs and pathology, the sources of errors in the reconstruction techniques as well as formulae relating design specification to geometric errors are provided. Finally, methods to measure organ volume from the 3D ultrasound images and sources of errors are described.

https://iopscience.iop.org/article/10.1088/0031-9155/46/5/201/pdf

Three-Dimensional Ultrasound Imaging

Although no deleterious effects form diagnostic ultrasound have been reported in epidemiologic studies and surveys of widespread clinical usage (Ziskin and Petitti 1988), the conditions for the onset of transient cavitation must be investigated in the total evaluation of potential risks associated with diagnostic ultrasound applications. An extension of the results from the approximate theory developed by Holland and Apfel (1989) is applied in this paper to a population of nuclei to predict the onset of cavitation in host fluids with physical properties similar to those of biological fluids. From this analysis and from results of recent in vitro cavitation experiments, an index is developed which can gauge the likelihood of substantial microbubble growth in the presence of short-pulse, low-duty cycle diagnostic ultrasound.

Gauging the likelihood of cavitation from short-pulse, low-duty cycle diagnostic ultrasound.

http://dlweb01.tzuchi.com.tw/DL/AcdActive/content/research/document/tjc/chen/shockwave%20induced%20neovascularization%20at%20tendon%20bone%20junction---2003%20JOR.pdf

Shock wave therapy induces neovascularization at the tendon-bone junction. A study in rabbits.

The dynamics of laser-produced cavitation bubbles near a solid boundary and its dependence on the distance between bubble and wall are investigated experimentally. It is shown by means of high-speed photography with up to 1 million frames/s that jet and counterjet formation and the development of a ring vortex resulting from the jet flow are general features of the bubble dynamics near solid boundaries. The fluid velocity field in the vicinity of the cavitation bubble is determined with time-resolved particle image velocimetry. A comparison of path lines deduced from successive measurements shows good agreement with the results of numerical calculations by Kucera & Blake (1988). The pressure amplitude, the profile and the energy of the acoustic transients emitted during spherical bubble collapse and the collapse near a rigid boundary are measured with a hydrophone and an optical detection technique. Sound emission is the main damping mechanism in spherical bubble collapse, whereas it plays a minor part in the damping of aspherical collapse. The duration of the acoustic transients is 20-30 ns. The highest pressure amplitudes at the solid boundary have been found for bubbles attached to the boundary. The pressure inside the bubble and at the boundary reaches about 2.5 kbar when the maximum bubble radius is 3.5 mm. The results are discussed with respect to the mechanism of cavitation erosion.

Optical and acoustic investigations of the dynamics of laser-produced cavitation bubbles near a solid boundary

Evidence is presented of acoustic cavitation generated by a Dornier extracorporeal shockwave lithotripter. Using x-ray film, thin aluminium sheets, and relatively thick metal plates as targets, evidence of liquid jet impacts associated with cavitation bubble collapse was observed. The jet impact was violent enough to puncture thin foils and deform metal plates. Furthermore, numerous jet impacts were generated over a volume of greater than 200 cm 3 . It is likely that such violent cavitation will also occur in tissue, and observed biological effects (e.g. renal calculus disintegration and tissue trauma) may be related to cavitation damage.

Acoustic cavitation generated by an extracorporeal shockwave lithotripter

A survey of the pressures and intensities generated by different commercial extracorporeal shock wave (ESWL) lithotripters is reported. The lithotripters included in the survey are the Dornier HM3, Wolf Piezolith 2200 and 2300, Siemens Lithostar, Technomed Sonolith 2000 and 3000, and EDAP LT-01. Measurements were made using a polyvinylidene difluoride (PVdF) membrane hydrophone in water. The zero crossing frequency of one complete cycle of the focused pulse from ESWL equipment is in the range 0.1 to 1 MHz. Spatial-peak temporal-peak positive and negative pressures up to 114 MPa and 10 MPa, respectively, have been measured and the rise times of the positive pressure half cycle at maximum output settings are 30 ns or less. The mean spatial-peak temporal-average intensity of the lithotripters is 5.0 × 10 2 W m −2 when operated at a pulse repetition frequency of 1 Hz. The spatial-peak pulse-average intensity ranges from 6.6 × 10 7 to 1.24 × 10 9 W m −2 . The estimated acoustic energy in a single pulse (at the focus) at the maximum output setting of the lithotripters varies from 2.0 × 10 −3 J to about 9.0 × 10 −2 J. The beam area in the focal plane varies by a factor of 100 on different lithotripters and the temporal-peak pressure at the position of the skin at the entry point of the beam by a factor of 30. Measurement problems associated with hydrophone damage and the uncertainties in the hydrophone calibration at high pressures are discussed and an estimate of the total uncertainty in the absolute measurements of the spatial-peak temporal-peak positive pressure is given as ±36%.

A survey of the acoustic output of commercial extracorporeal shock wave lithotripters

A review of the physical properties and biological effects of the high amplitude acoustic fields used in extracorporeal lithotripsy

The acoustic emission from cavitation in the field of an extracorporeal shock wave lithotripter has been studied using a lead zirconate titanate piezoceramic (PC4) hydrophone in the form of a 100-mm diameter focused bowl of 120-mm focal length. With this hydrophone directed at the beam focus of an electrohydraulic lithotripter radiating into water, it is possible to identify signals well above the noise level, at the 1-MHz resonance of the hydrophone, which originate at the beam focus. Light emission, attributed to sonoluminescence, is also shown to originate at the focal region of the lithotripter, and the signal obtained from a fast photomultiplier tube directed at the focus has similarities in structure and timing to the detected acoustic signals. The multiple shock emission resulting from a single discharge of an electrohydraulic source is shown to result in two separate bursts of cavitational activity separated by a period of 3–4 ms. The signal burst corresponding to the primary shock has a duration of about 600 μs with little noticeable structure. The signal burst associated with the secondary shock has a reproducible structure with two distinct peaks separated by about 200 μs depending on the shock amplitude. The timing and structure of each burst is shown to be in reasonable agreement with the theoretical predictions made by Church (1989) based on the Gilmore model of bubble dynamics. In particular, it is shown that it is possible to obtain precise measurements of the time delay between the separate peaks within the signal burst detected following the secondary shock and this may, as predicted, provide a method of determining the size of bubbles remaining after the primary shock.

Acoustic emission and sonoluminescence due to cavitation at the beam focus of an electrohydraulic shock wave lithotripter.

A system is described for calculating volume from a sequence of multiplanar 2D ultrasound images Ultrasound images are captured using a video digitising card (Hauppauge Win/TV card) installed in a personal computer, and regions of interest transformed into 3D space using position and orientation data obtained from an electromagnetic device (Polhemus, Fastrak) The accuracy of the system was assessed by scanning 10 water filled balloons (13–141 mL), 10 kidneys (147–200 mL) and 16 fetal livers (8–37 mL) in water using an Acuson 128XP10 (5 MHz curvilinear probe) Volume was calculated using the ellipsoid, planimetry, tetrahedral and ray tracing methods and compared with the actual volume measured by weighing (balloons) and water displacement (kidneys and livers) The mean percentage error for the ray tracing method was 09 ± 24%, 27 ± 23%, 66 ± 54% for balloons, kidneys and livers, respectively So far the system has been used clinically to scan fetal livers and lungs, neonate brain ventricles and adult prostate glands

J.E. Saunders

Papers

Acoustic cavitation generated by an extracorporeal shockwave lithotripter

A survey of the acoustic output of commercial extracorporeal shock wave lithotripters

A review of the physical properties and biological effects of the high amplitude acoustic fields used in extracorporeal lithotripsy

Acoustic emission and sonoluminescence due to cavitation at the beam focus of an electrohydraulic shock wave lithotripter.

Volume estimation from multiplanar 2D ultrasound images using a remote electromagnetic position and orientation sensor