JP2006263128A - Method and device for measuring vascular elasticity modulus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measuring vascular elasticity modulus simply measuring the credible vascular elasticity modulus at an artery part of a wrist. <P>SOLUTION: This method for measuring the vascular elasticity modulus is provided with an ultrasonic wave entering means allowing ultrasonic waves to enter therein and an ultrasonic detecting means detecting the ultrasonic waves reflected from a vascular wall, applies external pressure equivalent to mean blood pressure to the blood vessel, calculates the inside diameter and the outside diameter of the blood vessel based on a time difference of the ultrasonic waves reflected from the inner/outer faces of the vascular wall in the front side and the ultrasonic waves reflected from the vascular wall inner/outer faces in the opposite side, and calculates the vascular elasticity modulus from the blood pressure and the blood vessel diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a blood vessel elastic modulus measuring method and a blood vessel elastic modulus measuring device, and more particularly to a blood vessel elastic modulus measuring method and a blood vessel elastic modulus measuring device that can easily measure the elastic modulus of a blood vessel at an artery portion of a wrist.

により血管弾性率Ｅが求められる。
特開２００２−２０９８５７号公報（第３頁） Obtaining the elastic modulus of blood vessels, especially arteries, is important for diagnosis and prevention of arteriosclerosis. The ultrasonic echo method is widely used because it is non-invasive and can obtain information about blood vessels inside the living body. Arterial blood delivered from the heart dilates and contracts arterial blood vessels depending on its temporally varying blood pressure. That is, the blood vessel diameter depends on blood pressure. There has been proposed a method of calculating the elastic modulus of a blood vessel from the diameter of a carotid artery obtained by an ultrasonic echo method and the blood pressure value obtained by a sphygmomanometer (for example, Patent Document 1). According to this, from the blood vessel inner radius a _d and the blood vessel outer radius b _d at the diastolic blood pressure Pid, the blood vessel inner radius a _s and the blood vessel outer radius b _{s at} the systolic blood pressure Pis,

Thus, the blood vessel elastic modulus E is obtained.
JP 2002-209857 A (page 3)

  However, the measurement method in the prior art is a case where an external pressure is not applied to the blood vessel, and the cross-sectional shape of the blood vessel at this time is circular. However, in reality, when the ultrasonic probe is pressed against the neck, it is difficult to reduce the external pressure to 0, and deformation of the blood vessel is inevitable. Therefore, when measuring the change in the radius of the blood vessel, the displacement of the blood vessel wall when the collapsed blood vessel is going to become a perfect circle due to the internal pressure is detected, which causes a large error. Further, in the normal blood pressure range of 50 mmHg to 140 mmHg, the amount of change in the carotid artery blood vessel diameter is as small as about 100 to 300 μm. Therefore, in order to detect this amount of change, an ultrasonic distance resolution of about 20 μm is required. However, in order to increase the resolution, it is necessary to increase the resonance frequency of the ultrasonic probe, but it is known that increasing the resonance frequency increases the attenuation of the ultrasonic wave in the living tissue. Therefore, the resonance frequency of the ultrasonic probe cannot be increased too much. Therefore, it is difficult to obtain a resolution of about 20 μm with an easily configured ultrasonic echo device, and an expensive ultrasonic echo device is required if the distance resolution is set to about 20 μm. By the way, the measurement site is preferably the radial artery of the wrist rather than the carotid artery. The radial artery is usually 2-4 mm in diameter. The relationship between blood pressure and blood vessel diameter is known, and the difference in blood vessel diameter corresponding to systolic blood pressure and diastolic blood pressure is 50 to 100 μm, which is smaller than the change in blood vessel diameter with respect to the carotid artery blood pressure. Therefore, it has been extremely difficult to measure the blood vessel elastic modulus for the radial artery with the conventional method.

(Object of invention)
An object of the present invention is to provide an apparatus that can accurately measure the vascular elasticity by a simple method for the radial artery of the wrist.

In order to achieve the above object, the following means are employed in the vascular elastic modulus measuring method and vascular elastic modulus measuring apparatus of the present invention.
A blood vessel wall on the near side, comprising: an ultrasonic wave incident means for entering ultrasonic waves; a detection means for detecting ultrasonic waves reflected from the blood vessel wall; a pressurizing means for pressurizing the blood vessel; and a measuring means for measuring blood pressure. Corresponds to the average blood pressure in the vascular elasticity measurement method that calculates the vascular elastic modulus by calculating the vascular inner diameter and outer diameter from the time difference between the ultrasonic waves reflected from the inner and outer surfaces of the blood vessel opposite to the ultrasonic waves reflected from the inner and outer surfaces. The blood vessel elastic modulus is calculated from the amount of blood vessel deformation when the blood vessel is pressurized with external pressure.

により血管弾性率Ｅを求めることを特徴とする。 In addition, an ultrasonic wave incident means for incident ultrasonic waves, a detection means for detecting ultrasonic waves reflected from the blood vessel wall, and a pressurizing means for pressurizing the blood vessel, the ultrasonic wave reflected from the inner surface of the blood vessel wall on the near side. In the blood vessel elastic modulus measurement method for calculating the blood vessel diameter from the time difference between the ultrasonic waves reflected from the inner surface of the blood vessel wall opposite to the sound wave and calculating the blood vessel elastic modulus, a pressure corresponding to the average blood pressure Pav is applied from the outside and measured independently. From the blood vessel inner radius a _d and blood vessel outer radius b _{d at} the time of diastolic blood pressure Pid, and the blood vessel inner radius a _s and blood vessel outer radius b _{s at} the time of systolic blood pressure Pis,

The blood vessel elastic modulus E is obtained by the following.

  In addition, the apparatus includes an ultrasonic wave incident unit that inputs ultrasonic waves, a detection unit that detects ultrasonic waves reflected from the blood vessel wall, a pressurizing unit that pressurizes the blood vessel, and a measurement unit that measures blood pressure. In the blood vessel elasticity measuring apparatus for calculating the blood vessel elastic modulus by calculating the blood vessel inner diameter and outer diameter from the time difference between the ultrasonic wave reflected from the inner and outer surfaces of the blood vessel wall opposite to the ultrasonic wave reflected from the inner and outer surfaces of the blood vessel wall, A blood vessel elastic modulus calculation unit is provided that calculates a blood vessel elastic modulus from a blood vessel deformation amount when a blood vessel is pressurized with an external pressure corresponding to.

により血管弾性率Ｅを求める血管弾性率演算部を設けたことを特徴とする。 In addition, an ultrasonic wave incident means for incident ultrasonic waves, a detection means for detecting ultrasonic waves reflected from the blood vessel wall, and a pressurizing means for pressurizing the blood vessel, the ultrasonic wave reflected from the inner surface of the blood vessel wall on the near side. In a blood vessel elastic modulus measuring device that calculates the blood vessel diameter from the time difference between the ultrasonic waves reflected from the inner surface of the blood vessel wall opposite to the sound wave and calculates the blood vessel elastic modulus, a pressure corresponding to the average blood pressure Pav is applied from the outside and measured independently. From the blood vessel inner radius a _d and blood vessel outer radius b _{d at} the time of diastolic blood pressure Pid, and the blood vessel inner radius a _s and blood vessel outer radius b _{s at} the time of systolic blood pressure Pis,

A blood vessel elastic modulus calculation unit for obtaining the blood vessel elastic modulus E is provided.

  In addition, an ultrasonic wave incident means for incident ultrasonic waves and a detection means for detecting ultrasonic waves reflected from the blood vessel wall are provided, and from the inner surface of the blood vessel wall opposite to the ultrasonic wave reflected from the inner surface of the blood vessel wall. In a blood vessel elastic modulus measuring device for calculating a blood vessel diameter from a time difference of reflected ultrasonic waves and calculating a blood vessel elastic modulus, a polyolefin system having an acoustic impedance of 8 to 10 mm close to the skin between the piezoelectric vibrator and the skin It is characterized by having the gel-like member.

  According to the blood vessel elastic modulus measuring method apparatus and the blood vessel elastic modulus measuring apparatus of the present invention, it is possible to easily and accurately and noninvasively measure a blood vessel elastic modulus that is more reliable than the conventional blood vessel elastic modulus. Therefore, since the blood vessel elastic modulus can be easily measured even at home, the effects of cholesterol management and lifestyle improvement can be known without going to the hospital. Therefore, it can contribute to reduction of medical expenses.

In the present invention, the blood vessel diameter and blood pressure are measured based on the relationship between blood pressure, blood vessel diameter, and blood vessel elasticity, and the blood vessel elasticity is obtained. Hereinafter, the principle of the present invention will be described.
The deformation of a blood vessel when an external pressure is applied is generally known as a pipe law, and the relationship between the external pressure and the volume of the blood vessel per unit length is a curve as shown in FIG. When the blood pressure fluctuation is given as the internal pressure of the pressure pulse wave, the blood vessel deforms and is detected as a blood vessel volume pulse wave. When the average blood pressure and the external pressure match, the amplitude of the volume pulse wave becomes maximum. At this time, the blood vessel wall is displaced significantly larger than when the external pressure is zero. The blood vessel displacement, that is, the blood vessel diameter in the minor axis direction, which has a large change amount with respect to blood pressure, is measured. The average blood pressure is determined from the systolic blood pressure and the diastolic blood pressure according to the following formula.

First, as shown in FIG. 1, a point of a radius r inside the hollow cylindrical elastic body where the inner radius of the hollow cylindrical elastic body is a, the outer radius is b, the inner pressure is _{Pi, and the} outer pressure is _Po. When the radial stress σ _rr and the circumferential stress σ _φφ in FIG. 1 are obtained by elastic mechanics, they are represented by the equations (1) and (2) in FIG. The Young's modulus E, the radial stress sigma _rr when the Poisson's ratio _lambda, direction deformation epsilon _Faifai by the hoop stress σ _φφ, the formula of Figure 1 according to the elastodynamic (3). Here, as shown in FIG. 2, if the blood vessel inner radius at the time of diastolic blood pressure Pid is a _d , the blood vessel outer radius is b _d , r = b _d , and the blood pressure P = Pav Equations (4) and (5) in FIG. 2 are derived from Equations (1) and (2). Further, _assuming that the inner radius of the blood vessel at systolic blood pressure Pis is as, the outer radius of the blood vessel is b _s , r = b _s, and the pressure P = Pav outside the blood vessel, the above-described equations (1), ( Equations (6) and (7) in FIG. 2 are derived from 2).

Therefore, the circumferential deformation ε _φφ d (b _d ) at r = b _d at the time of diastolic blood pressure Pid is expressed by the equation (8) in FIG. 2 from the above equations (3), (4), and (5). Become. Further, the circumferential deformation ε _φφ s (b _s ) at r = b _s when the systolic blood pressure Pis is given by the above-described equations (3), (6), (7) and the equation (9) in FIG. Become.

The difference in circumferential deformation ε _φφ s (b _s ) _{−ε φφ} d (b _d ) between the diastolic blood pressure Pid and the systolic blood pressure Pis is the difference between the circumferential length 2πb _s and the circumferential length 2πb _d . Since it is standardized by the average circumference (b _s + b _d ) / 2, the equation (10) in FIG. 3 is obtained.

  From the equations (8), (9), and (10) in FIG. 2, the equation (12) shown in FIG.

  Therefore, in the vascular elasticity measurement method, the vascular elasticity can be easily measured by measuring the blood pressure with a sphygmomanometer and measuring the blood vessel diameter with an ultrasonic echo device.

  Specific examples of the blood vessel elastic modulus measuring apparatus and the measuring method using the blood vessel elastic modulus measuring method described above will be described in detail with reference to the drawings. FIG. 5 is a diagram for explaining an optimal embodiment of the present invention. FIG. 6 is a diagram showing the structure of the ultrasonic echo sensing unit 100. FIG. 7 is a block diagram showing an electronic circuit configuration according to the embodiment of the present invention.

  As shown in FIG. 5, the blood vessel elasticity measurement apparatus according to the present embodiment includes an ultrasonic incident unit that inputs ultrasonic waves, a detection unit that detects ultrasonic waves reflected from a blood vessel wall, and the ultrasonic incident unit It comprises a pressurizing unit 50 as pressurizing means for pressing an ultrasonic echo sensing unit 100 comprising sound wave detecting means against a living tissue.

  The ultrasonic echo sensing unit 100 of FIG. 6 is provided with an ultrasonic transducer 110, a pressure sensor 101, a pressure transmission bag 103, and a coupled gel member 120. Further, as shown in FIG. 5, although not shown in the pressurizing unit 50, air is sent into the bellows 106 through the pipe 107 using an air pump incorporated in the main body, and the ultrasonic echo sensing unit 100 is attached to the wrist portion. It can be pressurized against the skin.

  In the ultrasonic echo method used in the present invention, in order to increase the distance resolution of ultrasonic waves, first, an electric pulse having a pulse width of about 100 ns is generated at a transmission frequency of 50 Hz, that is, at an interval of 20 ms. An ultrasonic pulse having an extremely short width is generated by being sent to the acoustic transducer 110. The ultrasonic transducer 110 is made of a PVDF (polyvinylidene fluoride) thin film piezoelectric vibrator and a copper plate having a thickness of 200 μm bonded to the back surface as a backing material. In order to achieve a resonance frequency of 10 MHz with respect to an electric pulse width of 100 ns, the thickness of the PVDF thin film is preferably 20 μm to 30 μm. In addition, ultrasonic waves from the back surface are reflected to the front side by the backing material, and ultrasonic pulses having a short pulse width are efficiently generated. For ultrasonic echo measurement of the radial artery 21, the diameter of the ultrasonic transducer 110 is preferably 4 to 5 mm.

  Since the acoustic impedance of the living body is about the same as that of the PVDF thin film of the ultrasonic transducer 110, the ultrasonic energy is efficiently incident into the living body even if it is brought into direct contact with the living body. Unnecessary multiple reflections are caused and S / N is lowered. In the present invention, in order to perform acoustic impedance matching for the coupling between the piezoelectric vibrator and the skin, a polyolefin-based coupling gel member 120 having a thickness of 8 mm, which is close to the skin tissue, is inserted and transparent in a section of substantially 8 mm. The non-reflective area is obtained. In addition, since the gel member has moderate adhesiveness, it eliminates the scattering of ultrasonic waves due to the unevenness of the skin surface and improves the S / N, and at the same time does not require a normally used liquid gel member. Convenience improved significantly.

  Considering the thickness 8 mm of the coupled gel member 120 and the depth of a general blood vessel from the skin, the curvature of the incident surface of the ultrasonic transducer 110 is preferably 1/13 (1 / mm).

In this manner, the ultrasonic pulse transmitted from the ultrasonic transducer 110 is transmitted through the object to be examined, and is reflected by the outer surface and the inner surface of the blood vessel having different acoustic impedances. It is also reflected on the opposite side of the blood vessel. The reflected ultrasonic pulse is incident on the ultrasonic transducer 110 and converted into an electric signal, and a total of four reflected waves are detected as electric pulses. Ultrasound is an elastic wave and is about 1520 m / s at 35 ° C. in living tissue. Therefore, when the distance of 1 mm is converted into time, it is approximately 700 ns. Convert the time lag of the reflected wave into distance. The thickness of the blood vessel wall is 100 to 200 μm, and the time difference between the reflected waves on the outer surface and the inner surface of the blood vessel wall is 120 to 240 ns.

  Next, an actual operation procedure will be described. First, the maximum blood pressure Pis, the minimum blood pressure Pid, and the average blood pressure Pav in the brachial artery are determined with a general blood pressure monitor.

  Next, as shown in FIG. 5 and FIG. 7, the ultrasonic echo sensing unit 100 is applied to the radial artery 110 of the wrist by the pressurizing unit 50 using air pressure until the value of the pressure sensor 101 indicates the average blood pressure Pav. Press. When the value of the pressure sensor 101 indicates the average blood pressure Pav, pressurization is stopped, and in this state, the ultrasonic transducer 110 receives ultrasonic echo signals as a total of four electric pulses.

After this electric signal (ultrasonic echo signal) is amplified by the preamplifier 201, only the high frequency of the resonance frequency 10 MHz is passed through the filter 202, the noise component is removed, and only the detected signal component is output. AD conversion of the signal component by the AD converter 203 is started and stored in the memory from the time when the coupling gel member 120 is delayed by the time required for the reciprocation of the ultrasonic wave with respect to the trigger signal synchronized with the transmission timing of the ultrasonic pulse. . The sampling frequency of the AD converter 203 is 200 MHz, and the sampling time for one ultrasonic pulse is 20 μs. Since the transmission frequency is 50 Hz, this sampling is performed approximately 30 to 50 times during one heartbeat. The measurement time is 5 seconds in order to record 5 to 7 beats. After the measurement is completed, the CPU 210 sequentially reads out the numerical values recorded in the memory, and reflects the reflected waves from the inner and outer walls of the first and second walls of the blood vessel wall with respect to the ultrasonic traveling direction, that is, a total of four reflected waves. Numerical processing for calculating the time lag and detecting the maximum and minimum of the time interval is performed, and average processing is performed for the obtained number of beats, and the blood vessel inner radius a _{d, the} blood vessel outer radius b _d , and the blood vessel inner radius a _{s Then, the} blood vessel outer radius b _s is calculated.

The vascular elastic modulus calculation unit 213 calculates the vascular elastic modulus E from the average blood pressure Pav _{, the} diastolic blood pressure Pid, and the systolic blood pressure Pis according to the following formula, and passes it to the display unit 212.

The display unit 212 displays the vascular elasticity E obtained as a result of the calculation on the liquid crystal display.

  According to the blood vessel elastic modulus measuring apparatus described above, the blood vessel elastic modulus E can be easily obtained while using a simpler apparatus than the conventional blood vessel elastic modulus E.

It is explanatory drawing which shows the stress and deformation | transformation of a hollow cylindrical elastic body. It is explanatory drawing which shows the deformation | transformation and stress of the blood vessel by a blood pressure. 3 is a formula representing a blood vessel elastic modulus according to the present invention. It is explanatory drawing which shows the blood-vessel deformation with respect to an external pressure. It is a figure explaining embodiment of this invention. It is a figure which shows the structure of the ultrasonic transducer of this invention. It is a block diagram which shows the structure which concerns on embodiment of this invention.

Explanation of symbols

21 radial artery
26 ribs
50 Pressure unit 100 Ultrasonic echo sensing unit 101 Pressure sensor
103 Pressure transmission bag 106 Bellows 110 Ultrasonic transducer
120 Bonded gel member
201 Preamplifier 202 Filter 203 AD Converter 204 Pulse Generator 210 CPU
212 Display Unit 213 Vascular Elasticity Display Unit

Claims (5)

  A blood vessel wall on the near side, comprising: an ultrasonic wave incident means for entering ultrasonic waves; a detection means for detecting ultrasonic waves reflected from the blood vessel wall; a pressurizing means for pressurizing the blood vessel; and a measuring means for measuring blood pressure. In the blood vessel elastic modulus measurement method for calculating the blood vessel elastic modulus by calculating the blood vessel inner diameter and the blood vessel outer diameter from the time difference between the ultrasonic pulse reflected from the inner and outer surfaces of the blood vessel wall opposite to the ultrasonic wave reflected from the inner and outer surfaces, the mean blood pressure is calculated. A blood vessel elastic modulus measurement method, comprising calculating a blood vessel elastic modulus from a blood vessel deformation amount when a blood vessel is pressurized with an external pressure corresponding to. An ultrasonic wave incident means for incident ultrasonic waves, a detection means for detecting an ultrasonic wave reflected from the blood vessel wall, and a pressurizing means for pressurizing the blood vessel, the ultrasonic wave reflected from the inner surface of the blood vessel wall on the near side, In the blood vessel elastic modulus measurement method for calculating the blood vessel diameter from the time difference of the ultrasonic waves reflected from the inner surface of the opposite blood vessel wall and calculating the blood vessel elastic modulus, a pressure corresponding to the average blood pressure Pav is applied from the outside and measured independently. From the obtained blood vessel inner radius a _d and blood vessel outer radius b _{d at} the time of diastolic blood pressure Pid, and blood vessel inner radius a _s and blood vessel outer radius b _{s at} the time of systolic blood pressure Pis,

2. The blood vessel elastic modulus measurement method according to claim 1, wherein the blood vessel elastic modulus E is obtained by the following.   A blood vessel wall on the near side, comprising: an ultrasonic wave incident means for entering ultrasonic waves; a detection means for detecting ultrasonic waves reflected from the blood vessel wall; a pressurizing means for pressurizing the blood vessel; and a measuring means for measuring blood pressure. Mean blood pressure in a blood vessel elastic modulus measuring device that calculates a blood vessel elastic modulus by calculating a blood vessel inner diameter and a blood vessel outer diameter from a time difference between ultrasonic waves reflected from the inner and outer surfaces of the blood vessel wall opposite to the ultrasonic waves reflected from the inner and outer surfaces. A blood vessel elastic modulus measuring device for calculating a blood vessel elastic modulus from a blood vessel deformation amount when a blood vessel is pressurized with an external pressure corresponding to the above. An ultrasonic wave incident means for incident ultrasonic waves, a detection means for detecting an ultrasonic wave reflected from the blood vessel wall, and a pressurizing means for pressurizing the blood vessel, the ultrasonic wave reflected from the inner surface of the blood vessel wall on the near side, In a blood vessel elastic modulus measuring device that calculates a blood vessel diameter from a time difference between ultrasonic waves reflected from the inner surface of the opposite blood vessel wall and calculates a blood vessel elastic modulus, a pressure corresponding to the average blood pressure Pav is applied from the outside and measured independently. From the obtained blood vessel inner radius a _d and blood vessel outer radius b _{d at} the time of diastolic blood pressure Pid, and blood vessel inner radius a _s and blood vessel outer radius b _{s at} the time of systolic blood pressure Pis,

The blood vessel elastic modulus measuring device according to claim 3, further comprising a blood vessel elastic modulus calculating unit that obtains the blood vessel elastic modulus E. An ultrasonic wave incident means for making an ultrasonic wave incident and a detection means for detecting an ultrasonic wave reflected from the blood vessel wall are reflected from the inner surface of the blood vessel wall opposite to the ultrasonic wave reflected from the inner surface of the blood vessel wall. In a blood vessel elastic modulus measuring apparatus for calculating a blood vessel diameter from a time difference of ultrasonic waves to calculate a blood vessel elastic modulus, a polyolefin-based gel having an acoustic impedance of 8 to 10 mm close to the skin between the piezoelectric vibrator and the skin The blood vessel elastic modulus measuring device according to claim 3 or 4, wherein the blood vessel elastic modulus measuring device has a cylindrical member.

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