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In extracorporeal lithotripsy, the electro-acoustic efficiency of electrohydraulic generators is limited by the inductance of the electrical discharge circuit. A new shock-wave generator is described that uses a coaxial discharge line enabling electro-acoustic efficiency to be greatly increased. The line is built using a para-electric ceramic with a relative dielectric constant of 1700, manufactured for use in high-voltage impulse mode. A coaxial spark gap, with minimal inductance, has been developed to obtain the triggered breakdown of the discharge line. Shock waves are created with a coaxial electrode plugged directly into the spark gap and immersed in an electrolyte of degassed saline. Electrode gap and electrolyte resistivity are adjusted to match the resistivity of the electrolyte volume between the underwater electrodes to the characteristic impedance of the line. The discharge line generates in the medium a rectangular current pulse with an amplitude of about 6000 A and a rise time of 50 ns. Compared with conventional generators, measurements of the expansive peak pressure pulse show an increase of 105% at 10 kV, 86.5% at 12 kV and 34.5% at 14 kV charging voltage. Electro-acoustic efficiency is found to be 11% instead of 5.5% for a conventional discharge circuit.

Encapsulating chemotherapeutic agents in liposomes improves targeting and efficacy of treatments against some tumors. The present work aims at evaluating if sonosensitive liposomes combined with cavitation for drug delivery enhance efficacy and reduce toxicity. Two focused beams were combined for stabilizing the cavitation cloud and an imaging probe used for guidance. Each 1MHz focused transducer had a 5cm diameter and focal length. Exposure conditions were 10.8kW/cm2 Isppa, 250Hz PRF and 1% duty cycle. Phosphatidylcholine-based nongaseous liposomes were loaded with Doxorubicin. To control for mechanical tissue damage, AT2 Dunning tumors on rats were first exposed to ultrasound only. Treatment induced temperature rose below 0.5° C. The tumor growth was not significantly slowed down by ultrasound, but histological examination of tumors evidenced large areas of necrosis which resorbed one week after ultrasound. The new liposomes were compared with conventional HSPC-based liposomes in terms of efficacy and t...

In extracorporeal shock wave lithotripsy (ESWL), spreading wave amplitude is limited by the inductance of the discharge circuit. The goal of this study is to demonstrate the possibility of increasing pressure wave amplitude by using a low inductance transmission line. A high voltage transmission line has been constructed using a ferroelectric ceramic with relative dielectric constant equal to 1700 to give a total capacitance of 100 nF. A coaxial spark gap, with minimal inductance, has been developed to obtain triggered breakdown of the charged line. This new discharge circuit generates a high voltage rectangular pulse between underwater electrodes and then creates a spreading wave. Pressure amplitude and electroacoustic efficiency compared to conventional generators results demonstrate qualities of this new generator

1350-4177/$ see front matter 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ultsonch.2010.12.007 DOI of original article: 10.1016/j.ultsonch.2010.07.009 ⇑ Corresponding author at: Universite de Lyon, Lyon F-69003, France. E-mail address: lucie.somaglino@yahoo.fr (L. Somaglino). 4th paragraph (line 35 of the Section), the line ‘‘off-time duration induced a decrease of hydroxyl radical production’’ should read as follows

A device devoted to the 3-D representation of the prostate has been developed. It operates with either sagittal or transverse images. On each selected image, an operator outlines the prostate (and/or an eventual pathological area), by means of a digitizing tablet. These contours are then described by a limited number of points. From these points, belonging to the object envelope, two 3-D representation techniques have been implemented: the B-spline parametric surface and the triangulation method. The main advantage of the triangulation algorithm is its rapidity, contrary to the one using the parametric surfaces. Moreover, it allows satisfying representations of simple anatomic shapes like the prostate. The understanding of the geometry of the object is improved by a fast rotation of the whole object.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Previous in vitro studies conducted in our group have shown the feasibility of monitoring drug release from liposomes by an inertial acoustic cavitation index. We currently report in vivo experiments utilizing the cavitation index in combined treatment of AT2 Dunning tumor grafted rats with focused ultrasound and liposomal doxorubicin. Sixty‐three rats were allocated into seven groups: control, low level ultrasound treatment, high level ultrasound treatment, free doxorubicin+high level ultrasound treatment, and liposomal doxorubicin, liposomal doxorubicin+low level ultrasound treatment, and liposomal doxorubicin+high level ultrasound treatment. Based on pharmacokinetic studies, it was decided to apply ultrasound to the tumor 48 h after drug injection. An experimental setup was built to perform repeatable and rapid sonications of tumors monitored by the cavitation index. Tumor growth was assessed for a period of 35 days after tumor inoculation. Results showed that liposomal doxorubicin significantly slowed...

In an electrohydraulic generator, two underwater metal electrodes are connected with a capacitor charged to a high voltage. When the circuit is switched on, a plasma is generated reaching temperatures of thousands of K, resulting in a compressive pressure pulse. The formation of the plasma is a nonreproducible phenomenon inducing great variations of the pressure pulse. When the electrodes are immersed in an electrolyte instead of degassed water, the conditions of electrical discharge are dramatically modified. The latency time and the amplitude of the oscillations of the discharge current decrease as the conductivity of the electrolyte increases. For a conductivity of 7 Ωcm, there is no latency, and the critically damped discharge is achieved. The expanding pressure wave is increased by 10%, and the mean peak pressure value over 120 shocks at the second focus after focalization is increased by 50%. The relative standard deviation of the pressure value at the second focus is only 5%, while it is about 30% in ordinary water. The fragmentation efficiency is considerably increased because total fragmentation is obtained in 220 shocks instead of 450 shocks in ordinary water when standard stones are used, and in 131 shocks instead of 304 shocks when gallstones are used. Last, we show that the wear of the electrodes is reduced by a factor 8 when electrolyte is used. The improvement is supposed to have two causes: First, the energy is delivered into the medium in a shorter time, and, second, the center of the shock wave is always located at the same place. The decreased wear should make it possible to treat a much greater number of patients without changing electrodes, and the enhancement of the pressure should increase the efficiency of the fragmentation of the gallstones without aggravating the patient's pain.

In electrohydraulic generators used in lithotripsy two underwater metal electrodes are connected in series with a capacitor charged to a high voltage. When the circuit is switched on, a plasma occurs reaching temperatures of thousands of degrees Celsius resulting in a compressive pressure wave. The formation of the plasma is a particular non reproducible phenomenon inducing great variations of the pressure values. We showed, when electrodes are immersed in an electrolyte instead of ordinary degassed water, that the mean pressure value is increased by 50 % and the standard deviation is 3 % instead of 30 %. The authors suggest that the improvement of the pressure value of the expanding wave is due to a better efficiency of the electro-acoustic conversion and that the small value of the standard deviation is related to the constant spark location. Measurements obtained by triangulation show that the birth place of the plasma in ordinary degassed water is changing shock after shock in contrary, the birth place in electrolyte is always located at the same place. Photographies confirm qualitatively this phenomenon. The authors show that the reproducibility and the higher value of the pressure allow a better fragmentation of standard stones.

Drug release from liposomes can be activated by ultrasound and inertial cavitation is assumed to be the main involved mechanism. Broadband noise is known as a good indicator for such cavitation. The feasibility of assessing the extent of drug release by acoustic noise measurements has been investigated. A 1.17‐MHz focused transducer (50‐mm diameter and 50‐mm focal length) was excited with tone‐bursts (duty cycle: 10%–100%, PRF: 100 Hz–10 kHz, and Ispta < 800 W/cm2). Emitted noise was registered with a broadband needle hydrophone and bandpass filtered between the fundamental and the first harmonic frequency for assessing the instantaneous inertial cavitation activity. A cavitation index (CI) was computed by integrating the filtered signal over time. This index was validated experimentally using terephthalate oxidized to fluorescent hydroxyterephthalate under the action of free hydroxyl radicals generated by inertial cavitation. The hydroxyterephthalate fluorescence and the CI were well correlated (R2≃0.92)...

Within the scope of an application to transcutaneous ultrasonic thrombolysis, this study compares inertial cavitation thresholds obtained at the focus of a transducer for two types of ultrasonic excitations: a classical one frequency signal and an excitation combining two slightly different frequencies. A cepstral filtering method is used to measure inertial cavitation activity for these signals. A 30% reduction of the threshold is observed when using bifrequency excitation.

The invention relates to a device generating ultrasonic waves focused in aocal point. Said generator device comprises a plurality of transducer elements arranged externally on a support means for focusing into a focal point, such as a circular dome, and is characterized in that the transducer elements are divided into at least two groups of transducer elements, of which the resonance frequency differs in such a way that the principal positive ultrasonic waves produced by each group add up together and the positive and negative secondary ultrasonic waves are at least partly cancelled, thus reducing significantly the negative waves. This device can be advantageously used for extracorporeal lithotripsy.

An extracorporeal shock wave lithotriptor using an ultrasound scan head pantograph location system has been designed. The shock wave ellipsoid reflector position is adjusted to the stone with a computer assisted positioning device. Seven dogs with stones implanted into the renal pelvis were treated and stone fragmentation occurred in all cases. Subsequently, 45 patients with stones were treated. The stones ranged in size from 5 to 29 mm (mean 16). Radio-opaque as well as poorly opaque or radiolucent stones were treated and fragmentation was achieved in 85% of cases. An additional endoscopic procedure was performed in four cases. No fragmentation occurred in four patients. Further shock wave treatment was necessary in two patients who presented with stones larger than 2 cm. Both radio-opaque and poorly opaque stones can be treated with this system. Ultrasound localisation and the ellipsoid positioning device avoid the need for expensive fluoroscopic equipment and a hydraulic patient positioning system.

Les auteurs decrivent en detail la realisation d'un velocimetre pulse a 20 MHz. Ce choix de la frequence d'emission des ultrasons permet une resolution longitudinale et transversale de plus ou moins 0·15 mm. Diverses applicationsin vitro, puis chez l'animal et chez l'homme justifient le developpement de ce type d'appareil, tant en microchirurgie que pour des etudes hemodynamiques precises.

Extracorporeal shock-wave cholelithotripsy was carried out in 135 symptomatic patients with radiolucent gallstones, followed by oral bile acid dissolution to assess the resultant stone disappearance rates. Fragmentation was satisfactory (all fragments less than 5 mm in diameter) in 34 patients (25%) after a single session of lithotripsy, and in 65 (48%) after multiple sessions. The overall satisfactory fragmentation rate was significantly higher in patients with single stones less than or equal to 20 mm in diameter when compared with those with larger solitary stones (71% vs. 38%, p less than 0.05), as it also was in all subjects with solitary stones when compared with those with multiple stones (60% vs. 34%, p less than 0.05). After 6, 9, and 12 mo of oral bile acid treatment, the stone-free rates were significantly higher in patients with satisfactory than in those with partial fragmentation (55% vs. 0%, 80% vs. 29%, and 90% vs. 33%, respectively; p less than 0.05). Only 1 of the 7 patients who had previously undergone endoscopic sphincterotomy for concomitant choledocholithiasis was free of stones after 1 yr of dissolution. During dissolution therapy, of the 102 patients in whom fragmentation had occurred, 1 (1%) developed mild acute pancreatitis, 23 (23%) suffered attacks of biliary colic, and 6 (6%) required cholecystectomy. We conclude that the result of fragmentation appears to be a major determinant of the success and rapidity of subsequent oral bile acid dissolution, and that when satisfactory, it allows for complete stone disappearance in most patients within the following year. A comparison of the present results with those of previous original studies suggests that to achieve such satisfactory fragmentation, patients should be selected on the basis of their stone characteristics, which optimally should present as solitary gallbladder calculi less than 20 mm in diameter. Furthermore, real-time ultrasonographic monitoring should be used during lithotripsy with a transducer centered along the shock-wave axis. Despite the innocuousness of the shock waves, the incidence of fragment migration and its possible complications, in our experience, emphasizes the need to restrict at present this nonoperative approach to the treatment of symptomatic gallstone disease.

Extracorporeal shock wave lithotripsy is now accepted as a method of choice for treatment of most renal stones. Shock waves can be generated by an underwater spark gap discharge at the first focal point of a hemi-ellipsoid. Resulting acoustic waves are reflected from the walls of the ellipsoid and converge at the second focal point, outside the ellipsoid. Any concretion placed at this point, provided that it is surrounded by a medium with transmission characteristics similar to those of water (e.g. human soft tissues) will be disintegrated. This physical principle has been used to disintegrate renal concretions (1). Prerequisites for extracorporeal shock wave lithotripsy are: (a) shock wave generation: (b) stone localization: and (c) a positioning device enabling the kidney stone position to coincide with the second focus of the ellipsoid (site of maximum energy density). Stone localization by two independent fluoroscopy tubes and patient positioning by a hydraulic overhead gantry were used by Chaussy. This system allows treatment of most opaque stones with a success rate of approximately 90%. However, the price of the system in addition to its size make it prohibitive for most health care institutions.

Biomedical focused ultrasound (US) could represent a new modality of neurostimulation overcoming the limitations of current techniques in terms of invasiveness and spatial resolution. While it has already been proven that low energy US can stimulate nervous activity at the systemic level, little is known regarding the biophysical mechanisms underlying this phenomenon. In this in vivo study, we intended firstly to prove the feasibility of generating US-induced nervous responses in a model of earthworm giant axons. Secondly, this nervous model was used to investigate the biological mechanisms responsible for US neurostimulation. Following a hypothesis of a cavitation-induced phenomenon proposed in previous studies, we used a confocal US device driven with US sequences specifically designed to induce cavitation (f = 1.1 MHz, Ncycles/pulse = 44 − 88, PRF = 32 − 250 Hz, Npulses/train = 76, TRF = 0.25 Hz). In vivo neural responses, constitued of trains of action potentials (APs) could be triggered by US along the lateral giant fibers (LGF) using acoustic pressures ranging from 5.8 to 14.3 MPa. These levels of pressure and the associated radiation forces are repeatable effects, while the observed phenomenon of US neurostimulation was not. Cavitation is a complex and random phenomenon, and the acoustic signatures recorded by hydrophone confirmed that identical ultrasound burst could induce very different bubbles cloud in the vicinity of the targeted nerve. These first results suggest that, in these experimental conditions, cavitation rather than radiation force is the main biophysical mechanism underlying ultrasound neurostimulation. Moreover, according to our observations, there is no direct causal link between a single US pulse and a single AP. APs should not be studied individually, but as a group, or a serial of subgroups, triggered by a train of US pulses.

An apparatus for generating high frequency shock waves having a truncated ellipsoidal reflector is provided. The apparatus has a cavity which constitutes a chamber for reflecting shock waves, the chamber being filled with a dielectric liquid such as water or oil. The apparatus also has a shock wave generator device which generally has two electrodes and a source for selectively and substantially instantaneously providing an electric voltage to the electrodes. The equipotential screen is fast with the ellipsoidal reflector and is grounded by the support formed by the ellipsoidal reflector. This equipotential screen limits electric leakage and thus renders the apparatus safer in operation for destroying targets such as tissues, biliary concretions, kidney stones, etc.