Blood clot disruption in vitro using shockwaves delivered by an extracorporeal generator after pre-exposure to lytic agent.

The standard methods for recanalyzing thrombosed vessels are vascular stenting or administration of thrombolytic drugs. However, these methods suffer from uncertain success rate and side-effects. Therefore, minimally-invasive ultrasound methods have been investigated.

In vitro sonodynamic cytotoxicity in regulated cavitation conditions.

Sonodynamic toxicity has always been linked to the cavitation phenomenon. In this work, sonodynamic effect with Photofrin was evaluated with a new ultrasound device: a regulated cavitation generator. In this way, acoustic intensity was substituted with cavitation level as ultrasound parameter.

Feasibility of using ultrasound contrast agents to increase the size of thermal lesions induced by non-focused transducers: in vitro demonstration in tissue mimicking phantom.

Miniature flat ultrasound transducers have shown to be effective for a large variety of thermal therapies, but the associated superficial heating implicates developing original strategies in order to extend therapeutic depth. The goal of the present paper is to use ultrasound contrast agents (UCA) to increase remote attenuation and heating. Theoretical simulations demonstrated that increasing attenuation from 0.

Treatment of esophageal tumors using high intensity intraluminal ultrasound: first clinical results.

Background: Esophageal tumors generally bear a poor prognosis. Radical surgery is generally the only curative method available but is not feasible in the majority of patients; palliative therapy with stent placement is generally performed. It has been demonstrated that High Intensity Ultrasound can induce rapid, complete and well-defined coagulation necrosis.

Morphological analysis of the interstitial ultrasonic ablation in porcine liver in vivo.

Background: The shape of the induced thermal ablation area is as important as its dimension. The aim of this study was to analyze the size reproducibility and the aspect of the interstitial ultrasonic ablation obtained by a planar transducer in porcine liver in vivo.

Methods: Five pigs were used.

Delivery by shock waves of active principle embedded in gelatin-based capsules.

Purpose: Delivering a drug close to the targeted cells improves its benefit versus risk ratio. A possible method for local drug delivery is to encapsulate the drug into solid microscopic carriers and to release it by ultrasound. The objective of this work was to use shock waves for delivering a molecule loaded in polymeric microcapsules.

Dual-mode ultrasound transducer for image-guided interstitial thermal therapy.

Deep-seated tumors can be treated by minimally invasive interstitial ultrasound thermal therapy. A miniature transducer emitting high-intensity acoustic waves is placed in contact with the targeted area to induce local thermal necrosis. Accurate positioning of the probe and treatment monitoring must be achieved for the technique to be effective.

Developing an interstitial ultrasound applicator for thermal ablation in liver: results of animal experiments.

Background: In this project, an interstitial ultrasound applicator was developed for the treatment of primary and secondary cancers of the liver. Experiments on animals were used to check the destructive capabilities of this probe within the hepatic parenchyma of the pig in vivo, with a study of the physical parameters of the ultrasound treatment. In parallel, the possibility of visualizing the lesions induced by means of ultrasound imaging was also studied.

High intensity ultrasound clamp for bloodless partial nephrectomy: In vitro and in vivo experiments.

In some patients at risk of disease recurrence of renal cancers, maximum conservation of the kidney is possible through partial nephrectomy. However, bloodless surgery is difficult to achieve. The article describes an ultrasonic clamp, which optimises energy deposition and monitors lesion development with an echo-based technique.

Numerical field intensity factor calculations for 1-3 piezocomposite structures.

The 1-3 piezocomposite transducers used in specific medical applications--as lithotripsy--must be excited by intense electrical impulses. By inference, the composite material is subjected to high-stress levels. To explain possible failure, a numerical tool for analyzing singular two- and three-dimensional stress fields in piezocomposite structures is proposed.

64-element intraluminal ultrasound cylindrical phased array for transesophageal thermal ablation under fast MR temperature mapping: an ex vivo study.

This work was undertaken to investigate the feasibility of using a cylindrical phased array for transoesophaeal thermal ablation under magnetic resonance (MR) imaging guidance. Sixty-four transducers (0.45 mm wide by 15 mm tall), operating at 4.

Bloodless partial nephrectomy with a new high-intensity collimated ultrasonic coagulating applicator in the porcine model.

Objectives: To evaluate the long-term hemostatic efficacy of a new high-intensity collimated ultrasonic (HICU) applicator for open subhilar partial nephrectomy (PN) in the porcine model.

Methods: An applicator was designed with a planar 3.78-MHz HICU transducer and a reflector to optimize the delivery of acoustic energy to coagulate renal tissue.

[Haemostatic efficacy of a high intensity focused ultrasound applicator in lower pole partial nephrectomy in the pig].

Objective: To evaluate the haemostatic property of a high intensity focused ultrasound (HIFU) applicator in lower pole partial nephrectomy in a porcine model.

Materials And Methods: An applicator with a flat HIFU transducer operating at a frequency of 3.78 MHz was designed.

Intraluminal high intensity ultrasound treatment in the esophagus under fast MR temperature mapping: in vivo studies.

New curative and palliative treatments are needed to respond to the poor prognosis of esophageal cancer. The purpose of this study was to determine whether magnetic resonance imaging (MRI) and MR thermometry can be used to monitor the thermal ablation induced by an intraluminal high-intensity ultrasound applicator positioned in the esophagus. Experiments were performed in vivo in 2 pig esophagi (25 thermal lesions per pig).

Monitoring the formation of thermal lesions with heat-induced echo-strain imaging: a feasibility study.

We investigated the feasibility of using echo-strain images to visualize the extent of high-intensity ultrasound (US)-induced thermal lesions during their formation. Echo-strain, defined as the relative deformation of the backscattered ultrasonic signal, is due to tissue expansion and to changes in the speed of sound during heating. First, a theoretical framework was developed to predict the influence of these effects on the echo signal.

Generation of higher pressure pulses at the surface of piezo-composite materials using electrical pre-strain.

New clinical concepts in lithotripsy demand smaller shock heads. Reducing the size of piezoelectric shock heads requires increasing the surface pressure of each transducer so that the total pressure at the focus remains the same. A new method allowing generation of large surface pressures is described.

Development of a compact self-focusing piezoelectric generator using electrical pre-strain piezocomposite material.

New clinical concepts in lithotripsy demand small shock heads. Reducing the size of piezoelectric shock heads will only be possible if the pressure generated at the surface of each transducer can be increased so that, the total pressure at the focus remains very high. So, we propose a new method allowing the generation of large surface pressures.

Comparison of two methods of treatment for intraluminal thermal ablation using an ultrasound cylindrical phased array.

Intraluminal (within the alimentary tract) thermal surgery has been shown to be a useful therapeutic option when extracorporeal focused ultrasound applicators cannot be used since their beam may not reach the target site. If plane transducers are used for the treatment of alimentary tract tumours, the applicator must be rotated in order to generate a cylindrical volume of necrosis. However, rotating these applicators and controlling their shooting direction presents technical difficulties.

Intraluminal ultrasound applicator compatible with magnetic resonance imaging "real-time" temperature mapping for the treatment of oesophageal tumours: an ex vivo study.

High intensity ultrasound has shown considerable ability to produce precise and deep thermal coagulation necrosis. Focused, cylindrical, spherical or plane transducers have been used to induce high temperatures in tissues to coagulate proteins and kill cells. Recently magnetic resonance imaging (MRI) has been used, with extracorporeal or intracavitary focused transducers and cylindrical interstitial applicators, to monitor temperature distribution and provide feedback during heating procedures.

Determination of the acoustic pressure at and the reflection coefficient of a target through measurements of the absorbed power and the emitter voltage.

A harmonic acoustic wave, fed back by a reflecting target, modifies the electric impedance of the emitter. This effect is studied using a tightly focused beam and various flat targets with known reflection coefficients, which are placed at pressure maxima or minima of the standing wave in the focal zone. It is possible to establish relationships that allow one to determine, for flat targets with unknown acoustic properties, the acoustic impedance and reflection coefficient of the target as well as the acoustic pressure present at the target, only from measurements of the absorbed power and the emitter voltage.

Feasibility of a transurethral ultrasound applicator for coagulation in prostate.

Transurethral resection of the prostate (TURP) is the surgical method routinely used in clinics to treat benign prostate hyperplasia (BPH). The purpose of this work is to demonstrate the feasibility of a transurethral ultrasound (US) applicator based on a miniature US flat transducer to coagulate prostatic tissues. Rabbit liver was found to comply well with human prostate.

Combination of thermal and cavitation effects to generate deep lesions with an endocavitary applicator using a plane transducer: ex vivo studies.

In the high-intensity focused ultrasound (US), or HIFU, field, it is well-known that the cavitation effect can be used to induce lesions of larger volume. The principle is based on the increase in the equivalent attenuation coefficient of the tissue in the presence of the bubbles created by cavitation. The elementary lesions produced by combination of cavitation and thermal effects, using focused transducers, were spherical and developed upstream of the focal point.

Transoesophageal ultrasound applicator for sector-based thermal ablation: first in vivo experiments.

New curative and palliative treatments must be proposed to respond to the bad long-term prognosis of oesophageal cancers. It has been demonstrated that high intensity ultrasound (US) can induce rapid, complete and well-defined coagulation necrosis. For the treatment of this cancer, we designed an applicator that uses an intraductal approach.

Long-lasting stable cavitation.

Stable cavitation is produced on the surface of a special target, i.e., an abrasive foil with a grain size of about 15 microm, insonified by a 473 kHz focused beam.

Ultrasound cylindrical phased array for transoesophageal thermal therapy: initial studies.

This work was undertaken to investigate the feasibility of constructing a cylindrical phased array composed of 64 elements spread around the periphery (OD 10.6 mm) for transoesophageal ultrasound thermotherapy. The underlying operating principle of this applicator is to rotate a plane ultrasound beam electronically.