JP2004041382A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately compute a blood pressure of a local area (local blood pressure) in a blood vessel by utilizing a transmitted/received wave of an ultrasonic wave. <P>SOLUTION: A maximum blood pressure P<SB>s</SB>and a minimum blood pressure P<SB>d</SB>are obtained by a cuff type hemodynamometer 30. Also, a maximum diameter D<SB>s</SB>and a minimum diameter D<SB>d</SB>regarding a local area are obtained corresponding to them, and those parameter values are provided to a non-linear function. By the non-linear function, a diameter D at each time to be input is reduced, and a pressure P at each time regarding the local area is computed. In the place of the diameter, the area of the blood vessel (the area on a minor axis cross section) may be utilized as well. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, to measurement of local blood pressure using ultrasonic waves.
[0002]
[Prior art]
A catheter-type sphygmomanometer is used to obtain a blood pressure waveform for a specific local site in a blood vessel. That is, a catheter is inserted into a blood vessel, and a local blood pressure at a specific site is measured by a pressure sensor provided at a distal end thereof. However, this technique is invasive and invasive, and places a heavy burden on patients. As a method of noninvasive blood pressure measurement, a tonometry method in which a pressure pulse wave of a radial artery is measured by a pressure sensor is known. However, since the absolute blood pressure cannot be obtained, it is necessary to calibrate the detection value of the pressure sensor using the blood pressure value measured by the cuff type sphygmomanometer wound around the upper arm.
[0003]
By the way, a non-invasive blood pressure measurement method using ultrasound is known (Reference 1: Motoaki Sugawara et al., Development of non-invasive measurement method of blood pressure waveform, Medical Electronics and Biotechnology, Vol. 21, pp. 429, 1983). Etc.). That is, since the blood pressure change and the blood vessel diameter change are approximately in a linear relationship, the blood vessel diameter change at the measurement site is measured using the ultrasonic echo tracking method, and the systolic blood pressure and the diastolic blood pressure are measured with the cuff type blood pressure monitor. The maximum blood vessel diameter is calibrated with the systolic blood pressure, and the minimum blood vessel diameter is calibrated with the diastolic blood pressure, whereby the change in blood vessel diameter is regarded as a blood pressure waveform.
[0004]
[Problems to be solved by the invention]
It is known that the relationship between the blood pressure change and the blood vessel diameter change is not strictly linear but has a non-linear characteristic (Hansen F, et al., Diameter and compliance in the human common artery-variations-reference). with age and sex, Ultrasound Med & Biro 21, pp 1-9, 1995. and Reference 3: Hayashi K, et al., Mechanical properties, human arteries, et al. That is, as the blood pressure increases, the artery becomes stiff, and the change in blood vessel diameter decreases. There is also arteriosclerosis due to aging and disease. Despite these factors, errors may increase if the relationship between the change in blood vessel diameter and the change in blood pressure is regarded as linear. Therefore, if a circulatory dynamic index, for example, a known wave intensity is calculated using the blood pressure waveform obtained by the linear approximation, a measurement error also occurs.
[0005]
It is an object of the present invention to more accurately measure local blood pressure using ultrasound.
[0006]
[Means for Solving the Problems]
The present invention is a wave transmitting and receiving means for transmitting and receiving ultrasonic waves to and from a subject, based on a received signal obtained by transmitting and receiving the ultrasonic waves, for a specific local site in a blood vessel in the subject, Blood vessel size waveform information calculating means for obtaining local size waveform information representing a time change of the size; a blood pressure monitor mounted on the body surface of the subject to measure systolic blood pressure and diastolic blood pressure; Estimating means for estimating local blood pressure waveform information representing a temporal change of the local blood pressure for the specific local site by converting the blood vessel size waveform information based on systolic blood pressure and diastolic blood pressure. Means for giving the systolic blood pressure and the diastolic blood pressure to a nonlinear function for estimating the local blood pressure waveform information from the local size waveform information, And executes the calculation for obtaining the information.
[0007]
According to the above configuration, the local blood pressure waveform information is obtained using the nonlinear function for estimating the local blood pressure waveform information from the blood vessel size waveform information. Therefore, the accuracy of estimating the local blood pressure can be further improved as compared with the case where the conventional linear function is used.
[0008]
Preferably, the local size is a blood vessel diameter. Preferably, the systolic blood pressure and P _s, the vessel diameter at this time is D _s, whereas, the minimum blood pressure and P _d, the vessel diameter at this time is D _d, the vessel diameter at a certain time is represented by D In this case, the local blood pressure P at the time is
P = _Pd * exp [β (D / _Dd- 1)]
_{However, β = ln (P s /} P d) / (D s / D d -1)
Required by
[0009]
Preferably, the local size is a blood vessel area. Preferably, the systolic blood pressure and P _s, the vessel area at this time is S _s, whereas, the minimum blood pressure and P _d, the vessel area at this time is S _d, the vessel area at a certain time was S In this case, the local blood pressure P at the time is
P = P _d * exp [β _s (S / S _d −1)]
Where β _s = ln (P _s / P _d ) / (S _s / S _d −1)
Required by
[0010]
For example, the blood vessel diameter for a local site can be obtained as the distance between two tracking points (gates) by performing echo tracking on the front wall and the back wall of the blood vessel on the ultrasonic beam. As the area of the blood vessel cross section (short axis cross section), a known KI method, A-SMA method, or the like, which traces a heart wall from a B-mode image to obtain a left ventricular area, can be used. Further, the blood vessel cross-sectional area may be obtained from the blood flow display by the color Doppler method.
[0011]
The local blood pressure waveform information obtained as described above is used, for example, in the calculation of the wave intensity. Of course, the information may be displayed as a numerical value or as a graph.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the principle of the embodiment according to the present invention will be described.
[0013]
Systolic blood pressure obtained by the cuff-type sphygmomanometer is wound around the upper arm portion (systolic pressure) and P _s, the vessel diameter at this time is D _s. Similarly, the lowest blood pressure (diastolic pressure) and P _d, the vessel diameter at this time is D _d.
[0014]
First, the relationship between (A): local blood pressure and blood vessel diameter (local diameter) will be examined. Now, it is assumed that the nonlinear relationship between the local blood pressure and the local diameter at a local site in a blood vessel is represented by the following exponential function having two parameters a and b.
[0015]
P = P (D, a, b)
= A * exp (b * D) (1)
From the above equation (1), the systolic blood pressure and the diastolic blood pressure are expressed by the following equations.
[0016]
_{P s = a * exp (b} * D s) (2)
_Pd = a * exp (b * _Dd ) (3)
From the relationship between the above expressions (2) and (3), a and b are expressed by the following expressions.
[0017]
_{b = ln (P s / P} d) / (D s -D d) (4)
a = _Pd / exp (b * _Dd ) (5)
Therefore, the relationship between the local blood pressure P and the blood vessel diameter D is represented by the following equation.
[0018]
P = _Pd * exp [b * (D- _Dd )]
= _Pd * exp [β (D / _Dd- 1)] (6)
Where β is
_{β = ln (P s / P} d) / (D s / D d -1) (7)
Is a blood vessel elasticity index called a stiffness parameter defined by (see Document 3). That is, the blood vessels become harder as β becomes larger.
[0019]
The above results indicate that when the characteristic of local blood pressure-diameter of blood vessel is approximated by an exponential function, the exponent is a stiffness parameter.
[0020]
Next, similarly to the above, the relationship of (B): local blood pressure-vascular area (short-axis cross-sectional area) will be examined. The systolic blood pressure obtained by the cuff-type sphygmomanometer and P _s, the vessel area at this time is S _s. Also, the minimum blood pressure and P _d, the vessel area at this time is S _d.
[0021]
Now, it is assumed that the nonlinear relationship between the local blood pressure P and the blood vessel short-axis cross-sectional area S is represented by the following exponential function having two parameters A and B.
[0022]
P = P (S, A, B)
= A * exp (B * S) (8)
From the above equation (8), the systolic blood pressure and the diastolic blood pressure are expressed by the following equations.
[0023]
_{P s = A * exp (B} * S s) (9)
_Pd = A * exp (B * _Sd ) (10)
From the relationship between the above equations (9) and (10), A and B are expressed by the following equations.
[0024]
_{B = ln (P s / P} d) / (S s -S d) (11)
A = P _d / exp (B * S _d ) (12)
Therefore, the relationship between the local blood pressure P and the blood vessel area S is represented by the following equation.
[0025]
P = _Pd * exp [B * (S- _Sd )]
_{= P d * exp [β s} (S / S d -1)] (13)
Here, the stiffness parameters are as follows.
[0026]
_{β s = ln (P s /} P d) / (S s / S d -1) (14)
When the blood vessel cross-section is circular, the area S by using the diameter D of the vessel S = [pi] D ^2/4
Is represented by The maximum vessel diameter D _s and vessel diameter D is the minimum blood vessel diameter D _d and the change amount [Delta] D s _therefrom, as the sum of [Delta] D, are respectively expressed by the following equation.
[0027]
D _s = D _d + ΔD _s (15)
D = D _d + ΔD (16)
Since the blood vessel diameter changes ΔD _s and ΔD are sufficiently smaller than the minimum blood vessel diameter D _d , that is, ΔD _s / D _d << 1, ΔD / D _d << 1,
_{S / S d -1 = (D} / D d) 2 -1 ≒ 2 (D / D d -1) (17)
S _s / S _d −1 = (D _s / D _d ) ² −1 ≒ 2 (D _s / D _d −1) (18)
Holds. Therefore,
β _s ≒ β / 2 (19)
_{P = P d * exp [β} s (S / S d -1)] (20)
≒ P _d * exp [β (D / D _d -1)] (21)
Can be approximated. From the above equations (20) and (21), almost the same results are obtained when the relationship between local blood pressure and blood vessel area is approximated by an exponential function and when the relationship between blood pressure and blood vessel diameter is approximated by an exponential function. Is understood.
[0028]
Next, an embodiment of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the entire configuration.
[0030]
In FIG. 1, a probe 10 is used in contact with the body surface 12 in the embodiment shown in FIG. 1, and the probe 10 transmits and receives ultrasonic waves. Specifically, an array transducer composed of a plurality of transducers is provided in the probe 10, and the array transducer generates an ultrasonic beam B. A scanning surface S is formed by electronically scanning the ultrasonic beam B. In the example shown in FIG. 1, the ultrasonic beam B is electronically linearly scanned, but the electronic scanning method may be electronic sector scanning.
[0031]
A blood vessel 14 exists in the living body, and the blood vessel 14 has a front wall 14A and a rear wall 14B when viewed from the probe 10. When measuring a specific local part in the blood vessel 14, for example, the position and posture of the probe 10 are adjusted while observing a B-mode image (two-dimensional tomographic image) so that the specific local part is included. The scanning surface S is positioned. Then, a specific beam direction is further designated on the scanning plane S, and the diameter of the blood vessel 14 is measured on the beam direction using the echo tracking technique. As will be described in detail later, in this case, a tracking gate for tracking the front wall 14A and the rear wall 14B on the specific beam direction is set.
[0032]
The transmission unit 16 functions as a transmission beamformer, and supplies a plurality of transmission signals with a predetermined delay relationship to a plurality of vibration elements. On the other hand, the receiving unit 18 performs phasing addition on a plurality of reception signals output from the plurality of vibration elements. That is, the receiving unit 18 functions as a receiving beamformer.
[0033]
The control unit 20 controls the operation of each component in the apparatus in addition to the operation control of the transmission unit 16 and the reception unit 18 described above. An operation panel 22 is connected to the control unit 20. The operation panel 22 includes a trackball, a keyboard, and the like. The reception signal after the phasing addition output from the receiving unit 18 is output to the ultrasonic image forming unit 24, the blood vessel displacement calculating unit 26, and the blood flow velocity calculating unit 28 in the present embodiment.
[0034]
The ultrasonic image forming unit 24 performs signal processing necessary for forming a known B-mode image. The signal processing includes known signal processing such as detection and logarithmic compression.
[0035]
The blood vessel displacement calculator 26 calculates the diameter of a local part in a blood vessel using the above-described echo tracking technique. Specifically, the pulsation of the front wall 14A and the rear wall 14B is detected in the two tracking gates, that is, the diameter is calculated from the displacement of each wall. This is a known technique itself. In the present embodiment has a function of this blood vessel displacement calculation unit 26 obtains a diameter D _d corresponding to the diameter D _s and the lowest blood pressure corresponding to the systolic blood pressure within one heartbeat. Of course, the diameter D at each time is also calculated. The diameters corresponding to the systolic blood pressure and the diastolic blood pressure may be specified in a pressure conversion unit 32 described later.
[0036]
The blood flow velocity calculator 28 calculates the blood flow velocity at each point in the scanning plane based on the Doppler method.
[0037]
Cuff-type sphygmomanometer 30 is a known blood pressure monitor wound around the upper arm, for example, subject, systolic P _s and the minimum blood pressure P _d is measured by the sphygmomanometer. Those pieces of information are output to the pressure conversion unit 32.
[0038]
The image display processing unit 34 is configured as a display processing unit including, for example, a DSC (Digital Scan Converter), and performs coordinate conversion, interpolation processing, and the like on image data output from the ultrasonic image forming unit 24. . The display processing unit 34 creates a blood pressure waveform at a local site in a blood vessel, and creates a two-dimensional blood flow image (color Doppler image) based on the speed information output from the blood flow speed calculation unit 28. Further, it has a function of creating a local pressure waveform based on information of the converted pressure P output from the pressure conversion unit 32 described later. Of course, the image display processing unit 34 may have a function of calculating an index such as a wave intensity.
[0039]
The pressure conversion section 32, the maximum blood pressure P _s and the diastolic blood pressure P _d, based on the maximum diameter D _s and the minimum diameter D _d that correspond to them, the above-described with respect to the diameter D input at each time (6 ) Is performed to estimate and calculate the pressure P at the local site. The information is output to the image display processing unit 34, and the image display processing unit 34 forms a local pressure waveform based on the local pressure P at each time as described above.
[0040]
The display unit 36 displays a two-dimensional tomographic image, a color flow mapping image, and the like. In the present embodiment, the local pressure waveform is displayed as a graph or a numerical value. Various types of information calculated based on such information of the local pressure waveform are also displayed on the display unit 36 as numerical values or graphs.
[0041]
FIG. 2 conceptually shows an operation example of the apparatus shown in FIG. 1 as a flowchart.
[0042]
First, in S101, transmission and reception of ultrasonic waves are started by the probe 10, and at the same time, blood pressure measurement is started by the cuff type sphygmomanometer 30. In S102, systolic _{P s} and the minimum blood pressure _{P d} is obtained by the cuff-type sphygmomanometer 30. On the other hand, in S103, the maximum diameter _{D s} which corresponds to the systolic blood pressure _{P s,} the minimum diameter _{D d} corresponding to the minimum blood pressure _{P d} is obtained. In this case, preferably the information D _s in one _heartbeat, may be identify D _d, by taking the ensemble average of a plurality heartbeats, be acquired their information Good. However, it is desirable that the measurement of blood pressure and the calculation of the diameter be as close as possible in time.
[0043]
For example, in S102 of the process to obtain the systolic blood pressure P _s and the minimum blood pressure P _d in the one heartbeat, may acquire a maximum diameter D _s and the minimum diameter D _d at the relevant heart.
[0044]
In S104, by executing the above-mentioned (6), that is, each parameter value _P s described above to a nonlinear _function, by P _d, D s, giving _{D d,} converts the diameter D to be input, As a result, the local blood pressure P is determined. Incidentally, this calculation is executed in real time, and the local blood pressure P converted at each time is obtained.
[0045]
In S105, the local blood pressure waveform indicating the time change of the local blood pressure P thus obtained is displayed on the display unit 36, or such information is numerically displayed. In S106, other information calculated based on such a local blood pressure waveform, desirably, a wave intensity waveform is displayed on the display unit 36.
[0046]
When the above calculation is continued in S107, each of the above-described steps is repeatedly executed. In that case, the steps of S102 and S103 may be executed again, or the calculation of the above-mentioned nonlinear function may be executed continuously while maintaining the parameter values obtained in those steps. Good.
[0047]
FIG. 3 is a graph showing the characteristic 202 of the present embodiment and the characteristic 200 of the conventional example.
[0048]
The horizontal axis of this graph is the blood vessel diameter at a local site at a certain time, and the vertical axis is the local pressure at the local site. In the conventional example 200, a linear function is used. However, in the present embodiment, since a non-linear function as described above is used, a pressure P different from the conventional pressure is obtained for the diameter D.
[0049]
FIG. 4 is a graph showing a pressure difference when the characteristics of the conventional example and the present embodiment are compared. For example, the pressure difference between the two is about 7% at the maximum, and according to the present embodiment, it is possible to approach the true pressure value more than before.
[0050]
FIG. 5 shows a pressure waveform obtained by the calculation according to the present embodiment. The horizontal axis represents time, and the vertical axis represents pressure. Here, reference numeral 204 is a conventional example, and reference numeral 206 is this embodiment. As described above, since the two are different from each other, it is possible to obtain the value more accurately than in the conventional case, for example, when calculating the wave intensity. According to the experiment of the inventor, in the present embodiment, the first peak is lower and the second peak is higher in the waveform of the wave intensity than in the related art.
[0051]
FIG. 6 shows a configuration of another embodiment. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0052]
In the embodiment shown in FIG. 6, a short-axis cross section of the blood vessel 14 is used. In FIG. 1, the probe 10 is positioned so that the scanning plane S takes the long-axis cross section of the blood vessel 14. In the embodiment shown in FIG. 6, the blood vessel axis is set so that the probe 10 can acquire the short-axis cross section of the blood vessel 14. The scanning plane S is set in a direction orthogonal to the scanning plane S. When, for example, a B-mode tomographic image is formed by the image display processing unit 34, the image information is output to the area calculating unit 50, and the area calculating unit 50 calculates the number of pixels existing in the blood vessel 14 on the tomographic image. The cross-sectional area of the blood vessel 14 is calculated by counting or by using various known methods. In this case, a two-dimensional blood flow image may be used.
[0053]
Thus, the maximum area S _s corresponding to the maximum blood pressure P _s, is identified with minimum area S _d corresponding to the minimum blood pressure P _d, the information is output to the pressure converting unit 52.
[0054]
The pressure conversion unit 52 executes the above equation (20) to convert the input area S in accordance with the specified parameter value to thereby calculate the pressure P of the local part, similarly to the above equation (6). I'm asking. Also in this case, in calculating the area, the maximum area and the minimum area in one heartbeat may be obtained, or the maximum area and the minimum area may be obtained by obtaining an ensemble average over a plurality of heartbeats. .
[0055]
【The invention's effect】
As described above, according to the present invention, the local blood pressure can be obtained more accurately than before.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention.
FIG. 2 is a flowchart for explaining an operation example of the device shown in FIG. 1;
FIG. 3 is a graph showing the relationship between diameter and pressure.
FIG. 4 is a graph for explaining a difference between a characteristic of a conventional example and a characteristic of the present embodiment.
FIG. 5 is a graph showing a local pressure waveform.
FIG. 6 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 probe, 14 blood vessel, 16 transmitting part, 18 receiving part, 20 control part, 24 ultrasonic image forming part, 26 blood vessel displacement calculating part, 28 blood flow velocity calculating part, 30
Cuff type sphygmomanometer, 32 pressure conversion unit, 34 image display processing unit.

Claims (5)

Transmitting and receiving means for transmitting and receiving ultrasonic waves to and from the subject,
Based on a received signal obtained by the transmission and reception of the ultrasonic waves, for a specific local site in a blood vessel in the subject, a blood vessel size waveform information calculating means for obtaining local size waveform information representing a temporal change in the size,
A sphygmomanometer which is attached to the body surface of the subject and measures systolic and diastolic blood pressures, and converts the local size waveform information based on the systolic and diastolic blood pressures measured by the sphygmomanometer, whereby the identification is performed. Estimating means for estimating local blood pressure waveform information representing a time change of the local blood pressure,
Including
The estimating means performs an operation for obtaining the local blood pressure waveform information by giving the systolic blood pressure and the diastolic blood pressure to a nonlinear function for estimating the local blood pressure waveform information from the local size waveform information. Ultrasound diagnostic device. The device of claim 1,
An ultrasonic diagnostic apparatus, wherein the local size is a blood vessel diameter. The device according to claim 2,
The systolic blood pressure and P _s, the vessel diameter at this time as D _s, whereas, the minimum blood pressure and P _d, the vessel diameter at this time is a D _d, the vessel diameter at a certain time when as D, The local blood pressure P at the time is
P = _Pd * exp [β (D / _Dd- 1)]
_{However, β = ln (P s /} P d) / (D s / D d -1)
An ultrasonic diagnostic apparatus characterized by the following. The device of claim 1,
An ultrasonic diagnostic apparatus, wherein the local size is a blood vessel area. The device according to claim 4,
When the systolic blood pressure is P _s and the vascular area at this time is S _s , while the diastolic blood pressure is P _d , the vascular area at this time is S _d, and the vascular area at a certain time is S, The local blood pressure P at the time is
P = P _d * exp [β _s (S / S _d −1)]
Where β _s = ln (P _s / P _d ) / (S _s / S _d −1)
An ultrasonic diagnostic apparatus characterized by the following.

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