Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1998-08-27
2001-01-23
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S490000, C600S500000, C600S503000
Reexamination Certificate
active
06176832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cardiovascular information measurement system capable of noninvasively and continuously measuring vital cardiovascular information.
2. Description of the Related Art
Various indices such as a volume flow of blood, viscoelasticity caused by vasodilation and vasoconstriction are conventionally used as cardiovascular indices for grasping the states of circulatory organs of a patient.
A volume flow of blood is measured by the following method. The blood vessel of a patient is irradiated with an ultrasonic wave, the blood flow velocity is obtained using a Doppler signal generated by the blood flow. The volume flow of blood is then obtained in accordance with the relationship between the blood flow velocity and the cross-sectional area of the blood vessel.
An optical flow method for measuring a velocity vector using the liminance gradient of continuous image data is used as a method of obtaining vasodilation and vasoconstriction rates.
When the volume flow of blood is to be obtained from the blood flow velocity calculated using the Doppler signal, demand has arisen for a technique for easily and continuously calculating the cross-sectional area of the blood vessel of interest in order to obtain the volume flow of blood.
The above optical flow method undesirably requires complicated sequential calculations.
A method of winding a manchette on an arm portion of a patient and measuring the blood pressure from the resultant vibration or sound has been practiced as a conventional method of measuring the blood pressure. However, when the blood pressure must be measured for several days upon surgical operation, the arm portion of the patient must be pressurized to result in considerable mental and physical loads.
To solve this problem, a method of measuring, with an ultrasonic wave, the propagation velocity of a pulse wave propagating through the blood vessel and measuring the blood pressure is disclosed in Japanese Patent Laid-Open No. 7-241288. According to this method, the blood pressure is calculated using the following theoretical expression:
&Dgr;P=&rgr;C&Dgr;v
where
&Dgr;P: the pressure change
&rgr;: the blood density
&Dgr;v: the flow velocity change
C: the pulse wave velocity
This theoretical expression is disclosed in the following reference (edited by The Japan Hydraulics & Pnuematics Society, New Hydropneumatic Handbook, Section 1, Chapter 3, 24-25, OHM-sha, Ltd., 1988). However, this theoretical expression is an expression based on a condition that no change occurs in the blood vessel wall. That is, this expression is made in no consideration of the influence of the blood vessel wall.
SUMMARY OF THE INVENTION
The present invention, therefore, has been made in consideration of the conventional problems described above, and has as its object to provide a cardiovascular information measurement system capable of noninvasively measuring the cross sectional shape of a blood vessel and calculating a cardiovascular index based on the measured sectional shape.
It is another object of the present invention to provide a cardiovascular information measurement system capable of noninvasively measuring the sectional shape of a blood vessel and accurately measuring the blood pressure in consideration of the pulse wave of the blood vessel wall.
In order to solve the above problems and achieve the above objects, a cardiovascular information measurement system according to the first aspect of the present invention has the following arrangement.
That is, a cardiovascular information measurement system comprises sectional shape detection means for simultaneously detecting sectional shapes of at least two arterial portions, cross-sectional area calculation means for calculating cross-sectional areas of the two arterial portions on the basis of the sectional shapes detected by the sectional shape detection means, flow velocity calculation means for calculating an average blood flow velocity in an artery on the basis of the cross-sectional areas calculated by the cross-sectional area calculation means, pulse wave velocity calculation means for calculating a pulse wave propagation velocity between the two arterial portions in accordance with time changes in the sectional shapes of the two arterial portions which are detected by the sectional shape detection means, relative blood pressure calculation means for calculating a relative blood pressure value to a reference blood pressure value obtained in a specific time phase, on the basis of the blood flow velocity calculated by the flow velocity calculation means and the pulse wave velocity calculated by the pulse wave velocity calculation means, and absolute blood pressure calculation means for calculating an absolute blood pressure value on the basis of the relative blood pressure value and the reference blood pressure value obtained in the specific time phase and measured in advance.
A cardiovascular information measurement system according to the second aspect of the present invention has the following arrangement.
That is, a cardiovascular information measurement system comprises ultrasonic emission means for emitting an ultrasonic wave toward a blood vessel, ultrasonic wave detection means for detecting an ultrasonic wave reflected in a living body, binarization means for setting an appropriate threshold value in accordance with an angle between an incident direction of the ultrasonic wave and a blood vessel wall and binarizing an output signal from the ultrasonic detection means, and index calculation means for calculating a cardiovascular index on the basis of blood vessel sectional shape information obtained from information binarized by the binarization means.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.
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Habu Yoshiyuki
Yaegashi Mitsutoshi
Burns Doane , Swecker, Mathis LLP
Nasser Robert L.
Terumo Kabushiki Kaisha
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