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Biomedical subjects

G Fontenier

Publications and source records attributed to G Fontenier.

15 recordsLinked to original sources
PubMed1985

Application of image processing techniques to gamma-angiography.

Different image processing techniques have been tested and compared on data derived from gamma-angiography images to detect the boundary of the left ventricle. The method involves a preprocessing step, followed by the edge detection itself. The best preprocessing is a nonlinear "variant" filtering, where each pixel is replaced by the average of the 3 X 3 neighborhood having the smallest variance. The edge detector giving the best contour is a Sobel operator. A second-order high-pass Butterworth filter also provides a good segmentation.

Computers↗
PubMed1985

An efficient medical database system implementation with its tool and data structure consideration.

The development of a new system for medical database application running on minicomputer under MUMPS system is described. Two kinds of data representation in global structure are briefly reviewed. The use of a subject oriented multi-dimensional data structure greatly simplifies database design and facilitates data manipulation, organization, selective retrieval and software development. It is concluded that the program generator approach can provide the flexibility necessary for various applications and future growth of computerized medical record system. The final system has been proven effective in practical operation. The future extension concerns the introduction of multi-microprocessor structure and logic representation is presented.

Computers↗
PubMed1984

Aortic input impedance in heart failure: comparison with normal subjects and its changes during vasodilator therapy.

This study was aimed at the evaluation of aortic impedance in patients with congestive heart failure. Aortic impedance (simultaneous measurements of aortic pressure and blood flow), mean (Wm) and pulsatile (Wp) powers were compared in 11 normal subjects and in 12 patients with heart failure. Pulse wave velocity (C: modified Moëns-Korteweg equation, simultaneous measurements of aortic pressure and radius) was determined under control conditions in all normal subjects and in 7 patients with heart failure. Impedance curves in patients with heart failure were characterized by increased values of the impedance modulus at 0 Hz (peripheral resistance) and at low frequencies. The characteristic impedance, C, and phase were not different from normal subjects. In six patients with heart failure, impedance curves were studied during nitroprusside infusion. During the infusion of the vasodilator, the impedance modulus at 0 Hz and at low frequencies decreased. The characteristic impedance was unchanged. The zero intercept of the phase was shifted towards lower frequencies. These results show that the changes in impedance curves in patients with heart failure are due to greater peripheral resistance and wave reflection. During nitroprusside infusion the stroke volume increased and the aortic blood flow became more pulsatile (greater values of low frequency components). This modification accounts for the increased values of Wm and Wp, and is related to decreased peripheral resistance and wave reflection.

Adult↗
PubMed1983

Forward and backward waves in the arterial system, their relationship to pressure waves form.

The purpose of this work was to analyze, in human subjects, the shape of the aortic pressure wave from its forward and backward components calculated by use of Westerhof's model. Twenty-nine patients were studied: 11 normal subjects, 11 hypertensive patients and 7 patients with congestive heart failure. The following measurements and calculations were performed both under control conditions and during either angiotensin infusion in 5 normal subjects or nitroprusside infusion in 6 hypertensive patients: cardiac output, aortic blood pressure (catheter tip micromanometer), blood flow velocity (electromagnetic catheter-tip velocity transducer) in the ascending aorta, aortic impedance and reflection coefficients allowing the calculation of the aortic forward and backward pressure waves. The results show that the shape of aortic pressure wave in hypertensive patients is related to increased arterial wall stiffness which determines greater values and overlap of the forward and backward waves. This result is corroborated by the changes observed during angiotensin infusion in normal subjects. The shape of pressure wave in heart failure patients is dicrotic. This shape is related to smaller values and overlap of forward and backward waves. This appears related to a reduced stroke volume. During peripheral vasodilation the shape of pressure wave in hypertensive patients becomes dicrotic. However, this was mainly related to later backward waves. These results confirm that the shape of pressure waves depends both on the arterial wall stiffness and on the left ventricular performance: mainly on the stroke volume. The calculation of forward and backward waves allows a quantitative analysis of pressure waves.

Adult↗
PubMed1976

Coating evolution with an implantable biological battery.

A cathode of smooth platinum in a right endoatrial position and an anode of Domal magnesium were used to construct a hybrid bioelectric battery designed to power a pacemaker. In use the cathode is gradually covered by a coating consisting of a crystalline layer and a layer of connective tissue. This coating is responsible for the system change in the reduction process at the cathode level: the transfer from an oxygen to a hydrogen system. This system change causes a voltage drop in the bioelectric battery. This paper deals with oxygen diffusion across the tissue layer, as well as with various spectral and chemical analyses. A high level of calcium and phosphorus in the different analyses carried out seems to show that the presence of these elements is related to the coating of the cathode. The effect on the formation of the coating of the position of the cathode is also discussed.

Animals↗
PubMed1975

Design of experimentation with a platinum-magnesium bioelectric battery.

The utilization of metal electrodes in the fabrication of a bioelectric battery has been the subject of intensive study for several years. Up to this date, subcutaneous cathodes of black platinum or of silver-silver chloride have been used in conjunction with anodes of aluminum or zinc. The subcutaneous black platinum is not reliable as a function of time due to the growth of overlying heterogeneous tissues. The utilization of a smooth platinum cathode in the right endoauricular position allows good reliability with time, but does not allow using a large surface area. Furthermore we have a reduction of the H-+ ions and not of the oxygen. A pure Domal magnesium anode was utilized with this cathode, which seemed to be a good compromise between to battery's voltage, its lifetime, and its lack of toxicity to body tissues.

Animals↗
PubMedDate not supplied

Semi-automatic medical image processing.

During the last few years a number of systems for graphics generation and image processing have been developed by the authors. Depending on the application, one can consider many kinds of systems; for example for simple analysis of cellular images, a system that realizes the video mixing between a camera and graphics data from a microcomputer would be adequate. For a more elaborate analysis, such as angiographic and echographic images requiring a high level of interactivity, a semi-automatic acquisition system linked to a host computer would be necessary. Limits in precision and execution time of these semi-automatic systems leads to independent work-stations that realize digital acquisition, processing, and display of images.

Computers↗
PubMedDate not supplied

Long-term in vivo behavior of a platinum endoauricular-magnesium hybrid battery.

A hybrid bioelectric battery designed for pacemaker feeding was developed and implanted in 15 dogs for a period of 18 or more months. The smooth platinum cathode, set on an intra-cavitary pacing lead, is located in the bloodstream of the right auricle. The anode of pure (99.9 percent) Domal magnesium is placed in the subcutaneous tissue, which is then consumed by a uniform corrosion process. The theoretical consumption for a current output of 200 muA was evaluated according to Faraday's law at 7 g in 9 years; however, the real consumption, taking into account the corrosion phenomenon, is estimated at 14 g in 9 years. This histological tolerance to the magnesium is excellent. The fundamental characteristic of this platinum-magnesium battery is the great reproducibility of the output parameters (voltage, power) and the excellent stability with time, for any chosen platinum surface or load resistance. For an output current of 200 muA, the battery provides an available output power of 100 muW at a reproducible and stable voltage of 0.5 v. This stability is demonstrated in a long-term study on 15 beagles.

Animals↗