Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Patent
1998-09-02
2000-09-05
Jaworski, Francis J.
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
600454, A61B 800, A61B 806
Patent
active
061135437
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for determining, by means of an ultrasonic echograph, the compliance and the blood pressure of an artery containing flowing blood, according to an artery model.
The invention also relates to an ultrasonic echograph having a system for carrying out said method.
2. Description of Related Art
Such a method is already known from the publication entitled "The Static Elastic Properties of 45 Human Thoracic and 20 Abdominal Aortas in Vitro and the Parameters of the Model" by G. J. LANGEWOUTERS et alii, published in "J. Biotech.,17, 1984, pp. 425-435". Said document discloses an artery model based on the hypothesis of pure elastic behaviour of arterial walls. First, direct measurements are obtained from IN VITRO experimentations, in static pressure conditions, and a pressure/arterial diameter diagramm is constructed from the experimental measurements. Then, a relationship (3) between the arterial cross-section and the pressure is established. Said relationship (3) called model is calculated based on Young's modulus (3a) which increases with pressure according to a second order function. Algebraic manipulation then integration of said modulus, taking into account boundary conditions, yields said general formulation (3) of the arterial cross-section (A(p)) value as a parametrical function of pressure (p), which only takes into account pure elastic behaviour of the artery. The derivative of said general formulation (3) with respect to pressure provides a formulation (4) of the static compliance (C(p)) as a parametrical function of pressure (p.428, col.1,2). The direct measurements and the results obtained by calculations using the model of a purely elastic artery are compared.
According to the author of this publication (p.429, col.1), these formulations (3,4) are valid for homogeneous, isotropic, piece-wise linear, purely elastic material with cylindrical cross-section. Thus, application to aortas is a gross approximation.
Nowdays, diagnosis of vascular diseases and therapeutic choices have to be based on the analysis of the arterial lesion morphology and on the analysis of blood flows. These informations must be obtained with accuracy, and without using invasive means.
SUMMARY OF THE INVENTION
The present invention aims at providing a method for determining the pressure and the compliance values of arterial walls, according to models now taking into account a more complex structure of said wails than that considered in the cited publication.
The aim of the invention is reached by a method according to claim 1.
Said method is much more efficient than a method based on this previous model.
Such an improvement of the new viscoelastic model is based on a better characterization of the mechanical behaviour of arterial walls, which results in that compliance and pressure are further more accurately defined and formulated.
An other object of the invention is to propose an ultrasonic echograph having a system to carry out said method.
This aim is achieved by an ultrasonic echograph according to claim 9.
This tool permits determining accurately and without using invasive means whether the examined artery fulfil efficiently its function of pressure wave guide, conveying the kinetic power generated by the cardiac pump while adapting the wave form to the downstream arterial system.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in further details with reference to the accompanying drawings, in which:
FIG. 1 shows diagrammatically a set-up for carrying out direct measurements of pressure and compliance of an arterial sample;
FIG. 2A shows a measured pressure curve E and a calculated pressure curve F obtained from the viscoelastic model now proposed; and
FIG. 2B shows a measured pressure curve E and a calculated pressure curve F' obtained from a purely elastic model;
FIG. 2C shows a dilation curve D as a function of time;
FIG. 3 shows pressure curves as functions of dilation with hysteresis A,B and withou
REFERENCES:
patent: 5054493 (1991-10-01), Cohn et al.
patent: 5107840 (1992-04-01), Bonnefous
patent: 5316004 (1994-05-01), Chesney et al.
patent: 5411028 (1995-05-01), Bonnefous
patent: 5830131 (1998-11-01), Caro et al.
Jaworski Francis J.
Renfrew Dwight H.
U.S. Philips Corporation
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