ITBM-RBM最新文献

This work is devoted to the segmentation of thrombosis in vivo venous ultrasound image. The evaluation of thrombosis size is of a big interest for the diagnosis of cardiovascular diseases. In this paper a new segmentation method for ultrasound images is developed, employing a geodesic active region model. This approach takes account both of boundary and region information using their statistical properties. The region information is approached with grey level distribution model and the estimation of the boundaries is based on the evolution of an initial curve using a level set method. The developed algorithm is tested on real B-mode ultrasound images, in vivo thrombus vein echotomographic images, to isolate the thrombus. The obtained experimental results have confirmed the ability of this approach to bound effectively the thrombus, and they pointed out also that the proposed method is adapted for ultrasound image segmentation.

Membrane processes are increasingly reported for various applications in both upstream and downstream technology, such as the established ultrafiltration and microfiltration, and emerging processes such as membrane bioreactors, membrane chromatography, and membrane contactors for the preparation of emulsions and particles. Membrane systems are taking advantages of their selectivity, high surface area per unit volume, and their potential for controlling the level of contact and/or mixing between two phases. This review presents these various membrane processes by focusing more precisely on membrane materials, module design, operating parameters and the large range of possible applications. Ultrafiltration and microfiltration are well-known membrane separation processes, used i.e. for solvent removal, virus filtration, and antibiotics production. Membrane bioreactors are alternative approaches to classical methods of immobilizing biocatalysts, i.e. for the production of aminoacids, antibiotics, and anti-inflammatories. Chromatographic membranes may replace advantageously conventional resin-based chromatography columns, having the benefit of the absence of the long diffusion times that often occur in resin-based chromatography. Finally, membrane contactors involve using a pressure to force a dispersed phase to permeate through a membrane into a continuous phase, for the preparation of emulsions and various types of particles.

Fibroscan^® is a new medical device that measures liver stiffness noninvasively. The method is based on one-dimensional transient elastography. Ultrasound signals (3,5 MHz) are used to follow the propagation of a low-frequency shear elastic wave (50 Hz) that propagates at a velocity that depends on liver stiffness. Measurement is performed on the right lobe of the liver using a probe that is placed on the skin surface. Result is obtained at the end of examination that takes about 5 minutes. Pilot and multicentre studies have shown that liver stiffness is strongly correlated to fibrosis stage obtained from liver biopsy on patients with chronic hepatitis C. Fibroscan^® could be used to improve the evaluation of patients with liver chronic diseases by reducing the number of liver biopsies and by allowing the following of treatments.

A controlled pulsed electrical field applied to a living tissue is believed to cause a structural reorganisation in the lipid bilayer of the cell membranes. This electropermeabilisation or electroporation process is used for opening up the cell membrane in order to get access to the cell. An electrical impedance tissue model that incorporates electroporation is presented. From this model a bio-impedance indicator is proposed that assesses the pore generation in the cell membranes. The indicator was determined during and after the electroporation. An impedance measurement device was designed and calibrated. This device was used for bio-impedance measurements on living rat tie muscles in relation with electroporation. The result from these measurements showed that it was possible to observe both openings and closings of the cell membranes during and after electroporation. Besides impedance measurements could be used for determining whether the electroporation is reversible or irreversible.

The use of medical devices within hyperbaric chambers has always been slowed down by the specific difficulties of this environment. Indeed, installing a medical device within a pressure level much higher than atmospheric pressure and in an oxygen enriched atmosphere is an interesting challenge. In fact, few manufacturers dare engage in this way. Besides, for many years numerous working groups have emerged in hyperbaric medecine. Currently a european standard is being finalized and based on a risk analysis identifying, among other things, a certain number of potential hazards. They can potentially generate dangers during the use of a hyperbaric chamber. Installing a medical device in a hyperbaric chamber is not an easy thing to do. Indeed, the risks induced by a use in a hyperbaric chamber cannot be minimized. Furthermore the medical device must not cause additional risks within the chamber or, anyway, the risks must be evaluated, reduced and accepted. Consequently, prior to installing a medical device, this study proposes a methodology which enables to evaluate the risk management concerning the use of a medical device. Once the methodology completed, the manager of hyperbaric oxygen therapy unit is able to decide whether to install the device or not.

A model of the cardiovascular system (CSV) that consists of the ventricle, the circulatory system and the regulation of the cardiac action is presented. The model of the ventricle includes a description of the electromechanical phenomena occurring during cardiac contraction. It explains the global behaviour of the heart and is coupled with a model of the circulation. The whole cardiovascular system is under the influence of a regulation model. In fact, the cardiovascular system is regulated by the Autonomic Nervous System (ANS). In this work, only the influence of the short-term regulation of blood pressure (the baroreflex) is considered. The model allows the simulation of various physiological tests of the ANS, like the tilt test or the Valsalva manœuvre. These tests are usually used with patients to detect some pathology (syncope for example). But the interpretation of the signals obtained (blood pressure, heart rate) is often difficult because of the complexity of the SCV. It is then possible to improve the comprehension of the interaction between the SCV and the ANS thanks to the model; and to give a physiological interpretation of the signals obtained with the tilt test and the Valsalva manœuvre.