JP2018102589A - Pulse wave propagation speed measuring device, blood pressure measuring device, and pulse wave propagation speed measuring method - Google Patents

Abstract

An object of the present invention is to shorten the time required for ultrasonic measurement when measuring pulse wave velocity. An ultrasonic unit that transmits a two-dimensional plane wave to a blood vessel of an artery and receives a reflected wave, and an arithmetic processing unit that performs signal processing on the received signal of the reflected wave, the arithmetic processing unit includes: Receiving beamforming based on the received signal of the reflected wave, selecting the first blood vessel position and the second blood vessel position having different positions in the major axis direction of the blood vessel, and the blood vessel in the first blood vessel position Detecting the first blood vessel diameter fluctuation timing and the second blood vessel diameter fluctuation timing of the blood vessel at the second blood vessel position, the first blood vessel diameter fluctuation timing, and the second blood vessel diameter A pulse wave velocity measuring apparatus that measures pulse wave velocity using fluctuation timing. [Selection] Figure 18

Description

  The present invention relates to a pulse wave velocity measuring device that measures a pulse wave velocity.

  2. Description of the Related Art Conventionally, a technique for acquiring biological information of a human body that is a subject using ultrasonic measurement performed by installing an ultrasonic unit (probe) including a plurality of ultrasonic elements on a biological surface is known. Yes. One of them is measurement of the pulse wave velocity (see, for example, Patent Document 1). For example, the pulse wave velocity is transmitted and received ultrasonic waves from the surface of the living body to the blood vessel at each position separated by a predetermined distance along the long axis direction of the blood vessel, and the fluctuation waveform of the blood vessel diameter at each position from the received signal of the reflected wave Can be measured (calculated).

JP-A-2005-52424

  By the way, in the conventional ultrasonic measurement, one scan is performed by transmitting and receiving an ultrasonic beam along the scanning line direction (depth direction) from the surface of the living body, and each time the received beam is based on the received signal of the reflected wave. In general, the reflected wave data related to the scanning line is generated by forming. On the other hand, in order to accurately measure the pulse wave propagation speed, it is necessary to calculate the blood vessel diameter continuously and correctly. The correct calculation of the blood vessel diameter requires capturing the correct position and diameter of the blood vessel, so the above scanning is performed while shifting the incident position of the ultrasonic beam along the short axis direction of the blood vessel. It is necessary to grasp the blood vessel position. Moreover, it is necessary to perform this in a cycle as short as possible than the beat cycle in order to continuously and correctly calculate the blood vessel diameter. However, the conventional method has a limit in speeding up the ultrasonic measurement related to the measurement of the pulse wave velocity.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique capable of shortening the time required for ultrasonic measurement necessary for measuring the pulse wave velocity.

  A first invention for solving the above problems includes an ultrasonic unit that transmits a two-dimensional plane wave to a blood vessel of an artery and receives a reflected wave, and an arithmetic processing unit that performs signal processing on the received signal of the reflected wave. The arithmetic processing unit performs reception beam forming based on a reception signal of the reflected wave, and selects a first blood vessel position and a second blood vessel position in which the positions of the blood vessels in the long axis direction are different; Detecting a first blood vessel diameter fluctuation timing of the blood vessel at the first blood vessel position and a second blood vessel diameter fluctuation timing of the blood vessel at the second blood vessel position; and the first blood vessel diameter fluctuation. It is a pulse wave velocity measuring device that measures the pulse wave velocity using the timing and the second blood vessel diameter fluctuation timing.

  According to another aspect of the present invention, there is provided a pulse wave velocity measuring method using an ultrasonic unit that transmits a two-dimensional plane wave to an arterial blood vessel and receives a reflected wave, wherein the received beam is received based on the received signal of the reflected wave. Performing forming, selecting a first blood vessel position and a second blood vessel position having different positions in the major axis direction of the blood vessel, a first blood vessel diameter fluctuation timing of the blood vessel at the first blood vessel position, and , Detecting a second blood vessel diameter fluctuation timing of the blood vessel at the second blood vessel position, and using the first blood vessel diameter fluctuation timing and the second blood vessel diameter fluctuation timing, the pulse wave velocity And measuring a pulse wave velocity measurement method.

  According to the first invention, ultrasonic measurement can be performed by transmitting a two-dimensional plane wave to a blood vessel of an artery and receiving the reflected wave. With one ultrasonic measurement, it is possible to obtain a reflected wave reception signal for the blood vessel portion along the long axis direction of the blood vessel traveling in the irradiation region of the two-dimensional plane wave. In addition, after performing ultrasonic measurement, reception beam forming is performed based on the received signal of the reflected wave, and blood vessel positions are selected at different positions in the blood vessel long axis direction (long axis direction position). The pulse wave velocity can be measured from the blood vessel diameter fluctuation timing. According to this, it is possible to shorten the time required for ultrasonic measurement necessary for measuring the pulse wave velocity.

  Also, as a second invention, the selecting includes performing reception focus processing on the reception signal relating to the short-axis cross section of the blood vessel including the first blood vessel position to select the first blood vessel position. And performing a reception focus process on the received signal related to the short-axis cross-section of the blood vessel including the second blood vessel position to select the second blood vessel position. A propagation velocity measuring device may be configured.

  According to the second aspect of the invention, it is possible to perform reception focus processing of the reception signal related to the blood vessel short-axis cross section at different long-axis direction positions of the blood vessels, and to select the blood vessel position at each long-axis direction position.

  According to a third aspect of the invention, the arithmetic processing unit specifies a major axis direction of the blood vessel from the first blood vessel position and the second blood vessel position, and is orthogonal to the identified major axis direction. The pulse wave propagation velocity measuring device according to the second aspect of the present invention may further be configured to further set the short-axis cross section.

  According to the third aspect of the present invention, it is possible to set a blood vessel short-axis cross-section so as to be orthogonal to the blood vessel long-axis direction at different long-axis direction positions of blood vessels, and to select a blood vessel position at each long-axis direction position.

  Further, as a fourth invention, the measuring includes the first blood vessel diameter fluctuation timing, the second blood vessel diameter fluctuation timing, and the first blood vessel position along the specified major axis direction. And measuring the pulse wave velocity using the distance between the second blood vessel position and the second blood vessel position, the pulse wave velocity measuring device of the third invention may be configured.

  According to the fourth aspect of the invention, the pulse wave propagation speed is calculated using the blood vessel diameter fluctuation timing of each blood vessel position selected at different long-axis direction positions of the blood vessel and the distance between each blood vessel position along the blood vessel long-axis direction. Can be measured.

  Further, as a fifth invention, the selecting includes selecting three or more blood vessel positions having different positions in the major axis direction of the blood vessel, including the first blood vessel position and the second blood vessel position. And the detecting includes detecting a blood vessel diameter fluctuation timing for each of the three or more selected blood vessel positions, and the measuring is performed using the blood vessel diameter fluctuation timing for each of the three or more blood vessel positions. You may comprise the pulse wave velocity measuring apparatus of any one of the 1st-4th invention including measuring the said pulse wave velocity.

  According to the fifth aspect, it is possible to select a blood vessel position at each of three or more long axis direction positions with different blood vessels, and to measure the pulse wave propagation velocity from the blood vessel diameter fluctuation timing of each selected blood vessel position.

  According to a sixth aspect of the present invention, the selecting includes tracking the blood vessel position by selecting the blood vessel position at a predetermined cycle, and the measuring includes measuring the pulse wave propagation velocity for each beat. You may comprise the pulse-wave propagation velocity measuring apparatus of any one of the 1st-5th invention including performing this.

  According to the sixth invention, each blood vessel position selected at a different position in the long axis direction of the blood vessel can be tracked at a predetermined period. Based on the tracking result, the pulse wave velocity can be measured for each beat from the blood vessel diameter fluctuation timing at each blood vessel position.

  In addition, as a seventh invention, the pulse wave velocity measuring device according to any one of the first to sixth inventions is provided, and the arithmetic processing unit is configured such that the blood vessel diameter or the second blood vessel position at the first blood vessel position A blood pressure measurement device that calculates blood pressure using the blood vessel diameter, the pulse wave velocity, the given reference blood vessel diameter, and the given reference blood pressure may be configured.

  According to the seventh aspect, the blood pressure can be calculated using the blood vessel diameter, the pulse wave propagation velocity, the reference blood vessel diameter, and the reference blood pressure at any of the blood vessel positions selected at different long-axis direction positions. .

The figure which shows the example of whole structure of a blood-pressure measuring apparatus. The schematic perspective view which shows an ultrasonic measurement simply. The schematic diagram of an object part. The figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The other figure explaining receiving beam forming. The figure which shows the example of extraction of the feature point in an ultrasonic image. The figure which shows an example of the blood vessel diameter fluctuation | variation waveform. The figure explaining calculation of a pulse wave velocity. The figure which shows the example in which the blood vessel long axis direction inclined with respect to the biological body surface. The figure which shows the other example of a blood vessel diameter fluctuation waveform. The block diagram which shows the function structural example of a blood-pressure measurement apparatus. The figure which shows the data structural example of reference value data. The figure which shows the data structural example of the blood vessel log data. The flowchart which shows the flow of the process which a blood-pressure calculation apparatus performs. The flowchart which shows the flow of the blood vessel position selection process. The schematic perspective view which shows simply the ultrasonic measurement in a modification. The figure which shows the structural example of the ultrasonic unit in another modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments described below, and modes to which the present invention can be applied are not limited to the following embodiments. In the description of the drawings, the same parts are denoted by the same reference numerals.

[overall structure]
FIG. 1 is a diagram illustrating an example of the entire configuration of a blood pressure measurement device 1 that is a pulse wave velocity calculation device 100, and illustrates a state in which an ultrasound unit 10 is attached to a subject 7. As shown in FIG. 1, the blood pressure measurement device 1 has a configuration in which an ultrasonic unit 10 is electrically connected to a processing device 30 via a cable.

  The ultrasonic unit 10 is installed on the skin surface (biological surface) of the subject 7 and transmits and receives ultrasonic waves (ultrasonic measurement). This ultrasonic unit 10 has a plurality of ultrasonic elements (ultrasonic transducers) 11 arranged in a matrix on the sensor surface side that comes into contact with the surface of a living body when in use. Prior to the ultrasonic measurement, the ultrasonic unit 10 is affixed and fixed by the adhesive pedestal 101 to the part (target part) of the subject 7 corresponding to the purpose of the measurement.

  The adhesive pedestal 101 has an adhesive layer that can be attached to and detached from the surface of the living body, and does not easily come off or peel off even if the subject 7 moves the body. With this adhesive pedestal 101, the ultrasonic unit 10 allows one of the ultrasonic elements (hereinafter, also simply referred to as “elements”) 11 to be arranged in one of the array directions (for example, the row direction) of a measurement target artery. The blood vessel (for example, carotid artery) 9 is installed on the surface of the living body of the subject 7 in a direction along the long axis direction. The blood vessel 9 is not limited to the carotid artery, and for example, the subclavian artery, the aorta, the radial artery, the femoral artery, or the like may be used as a measurement target.

  The processing device 30 is a kind of computer control device, drives the ultrasonic element 11 to control ultrasonic measurement, and calculates the blood vessel diameter of the blood vessel 9 in real time based on the measurement result. And a pulse wave velocity (PWV; Pulse Wave Velocity) is measured from the obtained blood vessel diameter, and blood pressure is measured. The ultrasonic measurement is repeated at a predetermined cycle. The unit of measurement in this predetermined cycle is called “frame”, and the blood vessel diameter is calculated for each frame. In addition, the pulse wave propagation speed PWV is measured for each beat and the blood pressure is measured, and the continuous measurement for continuously measuring the pulse wave propagation speed PWV and the blood pressure P for each beat is realized.

[principle]
1. Ultrasonic Measurement FIG. 2 is a schematic perspective view schematically showing ultrasonic measurement by the ultrasonic unit 10. Here, the row direction of the elements 11 along the blood vessel 9 is the y direction, the column direction of the elements 11 is the x direction, and the direction orthogonal to these directions (the depth direction from the living body surface 71 of the target site) is the z direction. It is defined as

  In the present embodiment, the processing device 30 drives each element 11 in parallel, so that the ultrasonic wave from each element 11 is converted into a two-dimensional plane wave 110 whose wavefront is parallel to the biological surface 71 in the target region in the z direction ( Irradiate in the direction of the large arrow). Then, the reflected wave of the transmitted ultrasonic wave is received by each element 11, and the received signal is output to the processing device 30. Thus, by irradiating the ultrasonic wave from each element 11 as the two-dimensional plane wave 110, it is possible to transmit the ultrasonic wave at once to the entire region of interest and receive the reflected wave. By using the received signal related to the two-dimensional plane wave 110 once, ultrasonic measurement at each position in the minor axis direction of the blood vessel 9 can be performed at each position in the major axis direction of the blood vessel 9 at the same timing. That is, it is possible to obtain a measurement result as if the state of the blood vessel 9 at the target site at a certain moment in time is cut out instantaneously and entirely. It is extremely difficult to obtain the same timing state of the entire blood vessel 9 when transmitting and receiving ultrasonic waves by narrowing the beam in the z-axis direction and scanning the target site while shifting the incident position of the ultrasonic beam as in the past. In addition, the measurement time is prolonged when re-scanning or the like occurs. It can be said that this embodiment without such a defect can significantly reduce the time required for ultrasonic measurement as compared with the prior art.

2. Blood vessel position selection processing The processing device 30 performs reflected wave data generation processing and blood vessel diameter calculation processing when selecting a blood vessel position at a different position in the long axis direction of the blood vessel 9.

(1) Reflected wave data generation process The reflected wave data generation process is a process for processing a reception signal from each element 11 and generating reflected wave data such as position information of the in vivo structure of the subject 7 and a change with time. is there. The reflected wave data includes at least a so-called B mode image, but may include other so-called A mode, M mode, and color Doppler mode images. In the A mode, the first axis is a sampling point sequence of the received signal along the direction of the scanning line, which will be described later, and the second axis is the received signal intensity (reflected wave intensity) of the reflected wave at each sampling point. In this mode, the amplitude (A mode image) is displayed. The B mode is a mode for displaying a two-dimensional ultrasound image (B-mode image) of the in vivo structure visualized by converting reflected wave amplitudes (A-mode images) related to a plurality of scanning lines into luminance values. It is.

  In the present embodiment, an ultrasound image (slice image of a target part) I of a blood vessel short-axis cross section (for example, the xz plane in FIG. 2) orthogonal to the blood vessel long-axis direction at two or more long-axis direction positions (y positions). Is generated for each frame. In each ultrasonic image I, a short-axis image of the blood vessel 9 is drawn. Hereinafter, the long-axis direction position where the ultrasonic image I is generated is referred to as “slice position”, and the blood vessel short-axis cross section passing through the slice position is referred to as “slice plane”.

FIG. 3 is a schematic view of the target portion 73 where the ultrasonic unit 10 is installed as viewed from the x direction. 3 to 12 are simplified and schematic diagrams in which the element 11 is extremely enlarged for easy understanding, and the slice surface is shown thick.
As described above, the ultrasonic image is an image of the slice plane of the target portion 73 based on the received signal from each element 11, and is generated at two or more y positions that are slice positions. Although the slice position may be set as appropriate, the pulse wave velocity PWV can be measured with higher accuracy as the number increases. The blood vessel diameter is calculated for each slice position in the subsequent processing, and the pulse wave propagation velocity PWV is measured based on the blood vessel diameter fluctuation at each slice position. Therefore, if the slice position is increased, the influence of noise can be reduced accordingly. For example, FIG. 3 shows slice planes A-1, A-2, and A-3 at three slice positions, and an ultrasonic image may be generated by thinning the y position as shown in FIG. An ultrasonic image may be generated at the y position.

  When generating an ultrasonic image, reception beam forming is performed based on a reception signal of a reflected wave from each element 11. The reception beamforming is a process of sequentially performing sampling with each position of the target portion 73 as a focal position, and phasing and adding the reception signals from each element 11 at each sampling point, and a known method can be used. The depth of the sampling point can be set based on the assumed depth of the blood vessel wall or the blood vessel lumen.

  As a specific procedure, first, reception focus processing (phasing processing) for delaying the reception signal from each element 11 is performed. Then, the reception signal of each element 11 after the reception focus process is added with weight. Thereby, only a signal from a desired direction (the direction of the scanning line) having the same phase can be amplified, and a reflected wave from each sampling point along the direction of the scanning line can be selectively extracted. Thereafter, necessary processing is performed on the reflected wave intensity obtained for each sampling point, and an ultrasonic image is generated. When a plurality of elements 11 constitute one channel and transmit and receive ultrasonic waves, the received signals obtained are phased and added for each channel.

  More specifically, reception beam forming is performed by sampling from the biological surface 71 side with the vertical direction of the slice plane (z-axis direction in the example of FIG. 3) as the direction of the scanning line, and generating scanning lines one by one. Do. 4 to 9 are diagrams for explaining reception beam forming related to the leftmost slice position (slice plane A-1) in FIG. 3. 4, 6, and 8 show the two-dimensional array of the elements 11 constituting the ultrasonic unit 10 installed on the biological surface 71 in a simplified manner of 8 × 8, and FIG. 5, FIG. 7, and FIG. 9 schematically shows the slice plane A-1 of the target portion 73, respectively.

  First, the scanning line L-1 at the left end of the slice plane A-1 is generated. In order to generate the scanning line L-1, for example, received signals from the 16 × 4 × 4 elements 11 hatched in FIG. 4 are used. When viewed from the y direction, the received signals from the respective elements 11 correspond to four rows from the left with hatching in FIG. 5 and from the left to four columns with hatching in FIG. 3 when viewed from the x direction. Then, the reception beam forming is performed by phasing and adding the reception signals from these 16 elements 11, and the scanning line L-1 shown in FIG. 5 is generated. Note that the number of elements 11 used to generate one scanning line is not limited to 16 of 4 × 4, and may be set as appropriate according to necessary resolution and the like.

  Subsequently, the right scanning line L-2 is generated. In this case, the received signal from each element 11 hatched in FIG. 6 is selected and used, and reception beam forming is performed to generate the scanning line L-2 shown in FIG. Then, the scanning lines are generated while selecting the reception signals from the respective elements 11 in the same manner up to the scanning line L-n at the right end shown in FIG. The scanning line L-n at the right end is generated by using the reception signal from each element 11 that is hatched in FIG.

  Similarly, ultrasonic images of the slice planes (slice planes A-2 and A-3 in FIG. 3) are sequentially generated for the other slice positions. For example, in the reception beamforming related to the slice plane A-2, first, the scanning line at the left end of the slice plane A-2 is generated using the reception signal from each element 11 hatched in FIG. In order to generate the scanning line on the right side, a reception signal from each element 11 hatched in FIG. 11 is used. Similarly, the scanning line is generated to the right end while selecting the reception signal of each element 11. In order to generate the scanning line at the right end, each element 11 hatched in FIG. 12 is used.

(2) Blood vessel diameter calculation process In the blood vessel diameter calculation process, the blood vessel diameter is calculated for each slice position by detecting the blood vessel 9 from each ultrasonic image generated at two or more slice positions as described above. The selection of the blood vessel position is performed by extracting a feature point in the ultrasonic image corresponding to each ultrasonic image at each slice position and detecting the blood vessel 9 from each ultrasonic image using the extracted feature point.

  FIG. 13 is a diagram illustrating an example of extracting feature points from an ultrasound image. In order to facilitate understanding, the number of feature points B is reduced in FIG. 13, but in practice, more feature points than shown are extracted. Further, the outline of the blood vessel 9 is indicated by a one-dot chain line.

  The feature point B is a point where the luminance value changes compared to the surroundings and can be observed conspicuously from the image. As a feature point extraction method, for example, a corner detection method (Harris and Stephens) can be used. Alternatively, other corner detection methods such as the minimum eigenvalue method (Shi and Tomasi) and FAST feature detection may be used, or local features such as SIFT (Scale invariant feature transform) and SURF (Speeded Up Robust Features). You may extract a feature point using a feature-value. Alternatively, a method may be used in which a peak of reflected wave amplitude (which may be a luminance value) is detected for each scanning line, and the peak position is extracted as a feature point.

  The reflected wave intensity of the ultrasonic wave becomes high at the position where the medium changes, and the position where the reflected wave intensity is high in the ultrasonic image (B mode image) is expressed as high luminance. Therefore, many feature points B appear in a portion where a luminance change occurs such as a blood vessel wall. On the other hand, since the ultrasonic wave hardly reflects inside the blood vessel 9 and passes through the blood, the feature point B hardly appears. That is, the feature points B distributed in a substantially circular shape along the blood vessel wall appear at the position of the blood vessel 9.

  Therefore, the blood vessel 9 can be detected by selecting the feature points B distributed in a substantially circular shape. Specifically, the center of the substantially circular shape is the center position of the blood vessel 9 (blood vessel center), each position of the selected feature point B is the position of the blood vessel wall, and on the scanning line (center scanning line) passing through the vicinity of the blood vessel center. Are determined as the front wall position and the rear wall position. Then, the distance (front-rear wall distance) D11 between the front wall position and the rear wall position on the central scanning line is calculated and set as the blood vessel diameter.

  After obtaining the positions of the front and rear walls once, for example, “tracking” is used to obtain the blood vessel center, the front wall position, and the rear wall position at each slice position after the next frame. In tracking, a region of interest (tracking point) is set in the reflected wave data of interest (for example, an A-mode image or an ultrasound image that is a B-mode image), and the region of interest is tracked and displaced between different frames. This is a known process for calculating. In the present embodiment, for example, the central scanning line and a predetermined number of scanning lines on the left and right are set as target scanning lines, and regions of interest (tracking points) are set at the front wall position and the rear wall position on each target scanning line. Then, each region of interest is tracked with the next frame, and the front wall position and the rear wall position in the next frame are obtained from the displacement. Thereafter, the distance between the front and rear walls is calculated for each target scanning line, and the maximum value among them is used as the blood vessel diameter. Further, the midpoint between the front and rear walls on the target scanning line where the distance between the front and rear walls is maximized is obtained as the blood vessel center.

3. Pulse wave velocity measurement process In the pulse wave velocity measurement process, first, a pulse wave is calculated using a time-series change (blood vessel diameter fluctuation) of one blood vessel diameter calculated for each frame at each slice position as described above. A characteristic period as a measurement period of the propagation speed PWV is determined. For example, any one of the characteristic periods of the diastolic period T _d , the systolic period T _s , and the overlapping notch period T _n can be set as the measurement period. Alternatively, all three characteristic periods may be set as measurement periods. In the present embodiment, for example, time measuring systolic T _s.

  Here, the pulse wave propagation velocity PWV can be measured if the blood vessel diameter variation at at least two blood vessel positions (more specifically, different long axis direction positions along the long axis direction of the blood vessel) is known. Therefore, first, the blood vessel position selected at any one of the slice positions is set as the first blood vessel position, and the blood vessel position selected at another slice position is set as the second blood vessel position, and the blood vessel diameter of the first blood vessel position is set as the second blood vessel position. The calculation principle of the pulse wave velocity PWV will be described using the first blood vessel diameter and the blood vessel diameter at the second blood vessel position as the second blood vessel diameter.

FIG. 14 is a diagram illustrating an example of a blood vessel diameter fluctuation waveform of the first blood vessel diameter and the second blood vessel diameter. FIG. 14 shows a blood vessel diameter fluctuation waveform for three beats, and each section divided by an arrow corresponds to a blood vessel diameter fluctuation waveform for one beat. The waveform is simplified for easy understanding. As shown in FIG. 14, the vascular diameter fluctuation waveform for one beat of the first vascular diameter and the second vascular diameter includes diastolic period T _d , systolic period T _s , and overlapping notch period T _n , respectively. The peak of the characteristic period appears.

Therefore, by detecting the peak from the blood vessel diameter fluctuation waveform of the first blood vessel diameter as the blood vessel diameter fluctuation timing, those peak times are detected as the first blood vessel diameter diastole T _d , systole T _s , and overlap cut. It can be determined as traces period _{T n.} Similarly, if a peak (blood vessel diameter fluctuation timing) is detected from the blood vessel diameter fluctuation waveform of the second blood vessel diameter, those peak times are converted into the diastole T _d , the systolic period T _s , and the overlap cut of the second blood vessel diameter. It can be determined as traces period _{T n.}

  Specifically, a predetermined differential operation is performed on each of the vasculature fluctuation waveforms obtained at each slice position, and when a peak condition indicating that the differential value is a peak equal to or higher than the reference is satisfied (time period, time phase). Is also detected as the peak time. For example, the peak time may be detected from a first-order differentiated velocity waveform, or the peak time may be detected from a second-order differentiated acceleration waveform.

Here, the pressure wave accompanying the heart contraction quickly reaches the blood vessel position closer to the heart among the first blood vessel position and the second blood vessel position. Assuming that the first blood vessel position is a slice position closer to the heart, the first blood vessel diameter is earlier in expansion / contraction timing than the second blood vessel diameter. Therefore, knowing the systolic T _s in each blood vessel position, their time difference (time difference between the peak time of systolic T _s of the peak time and the second vessel diameter during systole T _s of the first blood vessel diameter) The pulse wave velocity PWV can be measured (calculated) from the distance between the first blood vessel position and the second blood vessel position. As the distance between the first blood vessel position and the second blood vessel position, for example, the distance between the blood vessel centers of the respective blood vessel positions can be used.

When the measurement time is the diastole T _d , the same processing is performed for each peak time difference between the first blood vessel diameter and the second blood vessel diameter diastole T _d to obtain the pulse wave velocity PWV. That's fine. If measurement time is from the dicrotic notch period T _n, it performs the same processing for the difference between the first vessel diameter and the peak time of the dicrotic notch period T _n of the second vessel diameter, pulse wave velocity What is necessary is just to obtain | require PWV.

When there are three or more slice positions, the pulse wave propagation velocity PWV is calculated using the peak time of the systolic period T _s in the blood vessel diameter variation waveform obtained at each of the three or more slice positions. FIG. 15 is a diagram in which the peak time of the systolic period T _s determined for each slice position is plotted, with the horizontal axis representing time and the vertical axis representing the position of the blood vessel 9 in the long axis direction (y position). The y position of the blood vessel center obtained at the corresponding slice position is used as the y position of each plot. The pulse wave propagation speed PWV is calculated as the slope of the obtained approximate straight line L11 by performing an approximate calculation such as the least square method using the relationship between the time represented by each plot and the position in the long axis direction, for example. Therefore, if the number of slice positions is increased, the pulse wave velocity PWV can be accurately calculated while suppressing the influence of errors caused by noise included in individual plots.

4). Blood Pressure Measurement Process The continuous change ΔP in blood pressure P can be expressed by the following equation (1) using the change ΔD in the blood vessel diameter D based on the Bramwell-Hill equation. In equation (1), ρ is the blood density. ΔD represents the difference between the blood vessel diameter D and the reference blood vessel diameter D0, and ΔP represents the difference between the blood pressure P and the reference blood pressure P0.

  The reference blood vessel diameter D0 and the reference blood pressure P0 can be determined by calibration. The calibration here is a process of setting a numerical relationship between the blood vessel diameter and the blood pressure by measuring the blood pressure using a pressurized sphygmomanometer and simultaneously obtaining the blood vessel diameter using the blood pressure measurement device 1 (calibration process). It is. In a usage mode such as monitoring blood pressure for a relatively long period (for example, several hours or several days), the above calibration process may be performed in the middle of blood pressure constant measurement. desirable.

In the blood pressure measurement process, blood pressure P is measured (calculated) using equation (1). In the present embodiment, any selected vessel position in one slice position (hereinafter, referred to as "representative vessel position") using the vessel diameter during systole T _s as vessel diameter D, a the vessel diameter D, the pulse wave propagation From the speed PWV, the reference blood vessel diameter D0 _s and the reference blood pressure P0 _s calibrated in advance for the systolic period T _s , the blood pressure P is calculated according to the equation (1). The blood pressure P obtained in this case is systolic blood pressure.

In the case of a timing measure diastolic T _d is representative and vascular diameter D of the diastolic T _d of vessel position, and the pulse wave propagation velocity PWV, diastolic T reference vessel diameter which is calibrated for _d D0 _d The blood pressure P (in this case, diastolic blood pressure) is calculated using the reference blood pressure P0 _d . Similarly, in the case where the time measured dicrotic notch period T _n, and the blood vessel diameter D of the dicrotic notch period T _n representative vessel position, and the pulse wave propagation velocity PWV, for dicrotic notch period T _n Using the calibrated reference blood vessel diameter D0 _n and reference blood pressure P0 _n , blood pressure P (in this case, double notch blood pressure) is calculated.

5. By the way, in the above description of the principle, the slice plane for generating the ultrasonic image is exemplified as the xz plane (see FIG. 2 and the like). However, in reality, the blood vessel 9 may not travel in parallel with the living body surface 71 in the target region 73, and the xz plane is not always orthogonal to the major axis direction of the blood vessel. For this reason, if the scanning line is generated along the z-axis direction simply using the xz plane as a slice plane, there is a problem that the calculation accuracy of the blood vessel diameter decreases. This is because, if the blood vessel 9 does not travel in parallel with the living body surface 71 (y direction), for example, as shown in FIG. In this example, a plane A21 orthogonal to the blood vessel long axis direction L21 may be set as the slice plane.

  On the other hand, in the present embodiment, ultrasonic measurement is performed by irradiating the entire region of the target region 73 with a two-dimensional plane wave, and the living body surface 71 is obtained from a reception signal already obtained as a measurement result of the ultrasonic measurement. Scan lines can be generated along any direction starting from the side.

  Therefore, in the present embodiment, prior to the blood vessel position selection process, first, a blood vessel long axis direction specifying process is performed in order to set a slice plane orthogonal to the blood vessel long axis direction. In this blood vessel major axis direction specifying process, first, the xz plane is provisionally set as a slice plane, and reflected wave data generation processing and blood vessel diameter calculation processing are sequentially performed for two slice positions (for example, slice positions at both left and right ends). Then, a straight line connecting the obtained blood vessel centers O21 and O23 is obtained to specify the blood vessel major axis direction L21. When the blood vessel major axis direction L21 is specified, a plane A21 orthogonal to the blood vessel long axis direction is set as a slice plane, and the process proceeds to blood vessel position selection processing. If the specified blood vessel long axis direction is parallel to the living body surface 71, the blood vessel position selection process may be performed for the remaining slice positions other than the two processed in the blood vessel long axis direction specifying process.

6). In the above explanation of the principle, the feature point is extracted by the blood vessel diameter calculation process of the first frame and the blood vessel 9 is detected. Then, a scanning line passing through the vicinity of the blood vessel center is set as the central scanning line, and in the subsequent frames, tracking is performed on the target scanning line including the central scanning line as a target, and each position of the front and rear walls is obtained.

Here, the blood vessel 9 repeats expansion and contraction approximately isotropically by pulsation. If tracking is used, the displacement of the blood vessel wall accompanying pulsation can be tracked between frames. However, there is a problem that if the subject 7 moves and body movements occur and the blood vessel center deviates from the vicinity of the central scanning line, the blood vessel diameter cannot be calculated correctly even if tracking is continued. This occurs because the relative positional relationship between the blood vessel 9 and the ultrasonic unit 10 is changed due to body movement, so that the distance between the front and rear walls on the scanning line passing through the vicinity of the blood vessel center cannot be obtained. For example, when the blood vessel 9 is shifted to the right as shown by the broken line in FIG. 5, the blood vessel diameter cannot be calculated correctly on the central scanning line set based on the position of the blood vessel 9 shown by the original solid line. Further, due to such a decrease in the calculation accuracy of the blood vessel diameter, a situation may occur in which the characteristic periods of the diastolic period T _d , the systolic period T _s , and the overlapping notch period T _n cannot be correctly determined in the subsequent processing. For example, in the example of FIG. 17, the shape of the blood vessel diameter fluctuation waveform is broken after the second beat, and it is difficult to correctly determine the peak time of each feature period from the blood vessel diameter fluctuation waveform thus broken.

  Therefore, in the present embodiment, the positional deviation determination process is performed based on the result of calculating the distance between the front and rear walls for each target scanning line that has been tracked, and the value is calculated on the left end or right end scanning line of the target scanning lines. It is determined that the displacement of the blood vessel 9 has occurred when the value becomes the maximum, or when the value becomes the maximum in the scanning lines other than the central scanning line among the target scanning lines. This is because if the central scanning line of the target scanning lines is the central scanning line, the diameter of the blood vessel 9 is correctly captured, but if the position of the blood vessel 9 is displaced, the scanning line for capturing the diameter is displaced from the center. . The state in which the left end or right end scan line of the target scan lines captures the diameter can be said to be a state where tracking is possible. Then, in the frame in which it is determined that the position deviation of the blood vessel 9 has occurred, the feature point is extracted again to detect the blood vessel 9, and the scanning line passing through the vicinity of the obtained blood vessel center is updated as the central scanning line. When the center scan line is updated, tracking is resumed.

[Function configuration]
FIG. 18 is a block diagram illustrating a functional configuration example of the blood pressure measurement device 1. The blood pressure measurement device 1 includes a two-dimensional array of ultrasonic units 10 and a processing device 30. The processing device 30 includes an operation input unit 31, a display unit 33, a communication unit 35, an arithmetic processing unit 37, And a storage unit 39.

  The ultrasonic unit 10 includes an ultrasonic transmission / reception circuit, and constitutes the ultrasonic measurement unit 20 together with the transmission / reception control unit 371 of the processing device 30. The ultrasonic measurement unit 20 realizes ultrasonic measurement.

  The transmission / reception circuit transmits / receives ultrasonic waves from / from the plurality of ultrasonic elements (ultrasonic transducers) 11 while switching between the transmission mode and the reception mode according to the transmission / reception control signal input from the transmission / reception control unit 371. Specifically, the transmission / reception circuit includes, as a transmission configuration, an ultrasonic oscillation circuit that generates a pulse signal having a predetermined frequency, a transmission delay circuit that delays the generated pulse signal, and the like. In addition, the receiving configuration is configured to include an amplifier that amplifies the received signal, an A / D conversion circuit, and the like, and the received signal (measurement result) of each element 11 after processing is selected as a blood vessel position of the arithmetic processing unit 37. Output to the unit 372. In this embodiment, an ultrasonic pulse is transmitted simultaneously from each element 11 to irradiate a target site with a two-dimensional plane wave having a propagation direction in the z direction.

  The operation input unit 31 receives various operation inputs from the user and outputs an operation input signal corresponding to the operation input to the arithmetic processing unit 37. It is realized with a button switch, lever switch, dial switch, trackpad, mouse, and the like.

  The display unit 33 is realized by a display device such as an LCD (Liquid Crystal Display), and performs various displays based on a display signal from the arithmetic processing unit 37.

  The communication unit 35 is a communication device for transmitting and receiving data to and from the outside under the control of the arithmetic processing unit 37. As a communication method of the communication unit 35, a wired connection via a cable compliant with a predetermined communication standard, a connection connected via an intermediate device called a cradle or the like, and a wireless communication are used. Various systems such as a wireless connection type can be applied.

  The arithmetic processing unit 37 includes, for example, a microprocessor such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and an IC (Integrated Circuit) memory. It is realized by electronic parts such as. The arithmetic processing unit 37 performs data input / output control with each function unit, and receives predetermined programs and data, operation input signals from the operation input unit 31, and reception of each element 11 from the ultrasound unit 10. Various arithmetic processes are executed based on signals and the like, and biological information of the subject 7 is acquired.

  The calculation processing unit 37 includes a transmission / reception control unit 371, a blood vessel position selection unit 372, a feature period determination unit 377, a heart rate determination unit 378, a pulse wave propagation velocity calculation unit 379, a blood pressure calculation unit 380, and a time measuring unit. 381. Each of these units will be described as being realized by software by the arithmetic processing unit 37 reading out the blood pressure measurement program 391 from the storage unit 39 and executing it. It can also be realized.

  The transmission / reception control unit 371 controls transmission / reception of ultrasonic waves by the ultrasonic unit 10. The transmission / reception control unit 371 outputs a transmission / reception control signal to the ultrasonic unit 10 and performs control for switching between the transmission mode and the reception mode.

  The blood vessel position selection unit 372 selects a blood vessel position at a different position in the long axis direction of the blood vessel 9. The blood vessel position selection unit 372 includes a reflected wave data generation unit 373, a tracking unit 374, a blood vessel diameter calculation unit 375, and a slice plane setting unit 376.

  The reflected wave data generation unit 373 performs reception beam forming based on the reception signal of each element 11 input from the transmission / reception control unit 371 and generates reflected wave data 394. In the present embodiment, scanning lines in the slice plane are generated at two or more slice positions, and an ultrasonic image (B-mode image) is generated.

  The tracking unit 374 refers to the reflected wave data 394, tracks tracking points between frames of ultrasonic measurement, and performs tracking for calculating the displacement. Functions such as so-called “echo tracking” and “phase difference tracking” are realized.

  The blood vessel diameter calculation unit 375 extracts feature points from the ultrasonic image at each slice position, and obtains the positions of the blood vessel center and the front and rear walls of the blood vessel 9. Further, based on the tracking result by the tracking unit 374, the positions of the blood vessel center and the front and rear walls are tracked for each slice position. Then, the blood vessel diameter is continuously calculated by obtaining the distance between the front and rear walls for each frame. By this continuous blood vessel diameter calculation, a blood vessel diameter fluctuation waveform is obtained for each slice position.

  The slice plane setting unit 376 sets a slice plane at each slice position so as to be orthogonal to the blood vessel long axis direction.

The feature period determination unit 377 determines each feature period of the diastole period T _d , the systole period T _s , and the overlapping notch period T _n for each slice position based on the blood vessel diameter variation waveform obtained at each slice position. .

  The heartbeat determination unit 378 determines a break of one heartbeat based on the blood vessel fluctuation waveform obtained at any one slice position, for example, according to the determination result of the feature period determination unit 377. The heart rate determination unit 378 may include a function for calculating a heart rate.

The pulse wave velocity calculation unit 379 calculates the pulse wave velocity PWV for each beat based on the peak time of the measurement time (for example, systole T _s ) determined at each slice position.

The blood pressure calculation unit 380, for example, from the blood vessel diameter D of the systolic period T _{s at} the representative blood vessel position, the pulse wave propagation speed PWV, the reference blood vessel diameter D0 _s for the systolic period, and the reference blood pressure P0 _s according to the equation (1) P is calculated.

  The timer unit 381 measures the measurement time. The timing method can be selected as appropriate, but for example, a system clock can be used.

  The storage unit 39 is realized by a storage medium such as an IC memory, a hard disk, or an optical disk, and stores various programs and various types of data such as calculation process data of the calculation processing unit 37. Note that the arithmetic processing unit 37 and the storage unit 39 may be separated from each other, and may be realized by a communication connection via a communication line such as a LAN (Local Area Network) or the Internet. For example, in that case, the storage unit 39 can be realized as a storage device of a server connected to the Internet.

  The storage unit 39 includes a blood pressure measurement program 391, reference value data 392, received signal data 393, reflected wave data 394, tracking data 395, blood vessel position data 396, blood vessel diameter log data 397, and PWV log. Data 398 and blood pressure log data 399 are stored. Of course, in addition to these, flags for various determinations, counter values for timing, etc. can be stored as appropriate.

  The blood pressure measurement program 391 is executed by the arithmetic processing unit 37, whereby a transmission / reception control unit 371, a blood vessel position selection unit 372, a feature period determination unit 377, a heart rate determination unit 378, a pulse wave propagation velocity calculation unit 379, a blood pressure calculation unit 380. The functions of the time measuring unit 381 and the like are realized. When these functional units are realized by hardware such as an electronic circuit, a part of a program for realizing the functions can be omitted.

The reference value data 392 stores a reference blood vessel diameter D0 and a reference blood pressure P0 for the characteristic period of the diastole T _d , the systolic period T _s , and the overlapping notch period T _n . Specifically, as shown in FIG. 19, reference blood vessel diameters D0 _d , D0 _s , D0 _n for each feature period and reference blood pressures P0 _d , P0 _s , P0 _n for each feature period are stored.

  The reception signal data 393 stores a reception signal from each element 11 obtained as a result of ultrasonic measurement for each frame.

  The reflected wave data 394 stores reflected wave data generated for each frame based on the received signal from each element 11. The reflected wave data 394 includes ultrasonic image (B-mode image) data at each slice position.

  The tracking data 395 is data of a tracking result by the tracking unit 374 and is used as a tracking point at each slice position, and stores the displacement of the front wall position and the rear wall position between the tracked frames for each slice position.

  The blood vessel position data 396 is data on the selection result of the blood vessel position by the blood vessel position selection unit 372. The blood vessel position, the positions of the front and rear walls obtained by selecting the blood vessel position at each slice position, the setting of the center scanning line, etc. Remember every frame.

  The blood vessel diameter log data 397 stores various data relating to the blood vessel diameter that is continuously calculated for each frame from the start to the end of measurement. Specifically, as shown in FIG. 20, in association with the measurement time for each frame, a pulsation number for identifying the pulsation at the time (for example, the number of pulsations from the start of measurement. And the blood vessel diameter calculated for each slice position at that time. The pulsation number is set based on the determination of the heart rate by the heart rate determination unit 378. Of course, other data can be stored as appropriate. In FIG. 20, the measurement time has gradually elapsed as “t001”, “t002”, “t003”, and “t004”, but since the pulsation number is “1”, the measurement time is related to the same pulsation. Indicates data. By looking at the blood vessel diameter at each slice position in time series in the blood vessel diameter log data 397, a blood vessel diameter fluctuation waveform is obtained.

The PWV log data 398 stores a pulse wave velocity PWV calculated for each beat in association with a pulsation number. Further, the blood pressure log data 399 stores the blood pressure at the measurement time (systolic period T _s ) calculated for each beat (in this case, the systolic blood pressure for each beat) in association with the pulsation number.

[Process flow]
FIG. 21 is a flowchart showing a flow of processing performed by the blood pressure measurement device 1. The processing described here is realized by causing the arithmetic processing unit 37 to read out and execute the blood pressure measurement program 391 from the storage unit 39 and operate each unit of the blood pressure measurement device 1. Prior to the measurement, the ultrasonic unit 10 is installed on the living body surface of the subject 7.

  First, the ultrasonic measurement unit 20 starts ultrasonic measurement using the ultrasonic unit 10 (step S1). The ultrasonic measurement started here is performed for each frame, and the measurement result (the reception signal of the reflected wave) is stored in the reception signal data 393.

  Subsequently, a blood vessel long axis direction specifying process is performed (step S3). In the blood vessel long axis direction specifying process, first, the reflected wave data generation unit 373 performs the reflected wave data generation process using the xz plane as a slice plane for two of the slice positions. Subsequently, the blood vessel diameter calculation unit 375 performs a blood vessel diameter calculation process for the two slice positions. Then, the inclination of the straight line connecting the blood vessel centers obtained at each slice position is specified as the blood vessel long axis direction.

  If the blood vessel long axis direction is specified, the slice plane setting unit 376 subsequently sets a slice plane at each slice position so as to be orthogonal to the blood vessel long axis direction (step S5).

  Thereafter, the blood vessel position selection unit 372 starts the blood vessel position selection process (step S7). By the processing started here, the blood vessel position at each slice position is selected for each frame, and the blood vessel diameter of the blood vessel position is stored in the blood vessel diameter log data 397.

  Further, the heart rate determining unit 378 starts to determine a heart rate (step S9). The determined identification information of one heartbeat is set as a pulsation number from the start of measurement.

Subsequently, the feature period determination unit 377 refers to the blood vessel diameter log data 397, detects the peak time from the blood vessel diameter fluctuation waveform obtained at each slice position, and detects the diastolic period T _d , systolic period T _s , and overlapping notches. determining each feature life periods _{T n} (step S11).

Subsequently, the pulse wave propagation velocity calculation unit 379 calculates the pulse wave propagation velocity PWV based on the peak time of the systole T _s determined for each slice position (step S13).

Then, the blood pressure calculation unit 380 calculates the blood pressure P from the blood vessel diameter D in the systolic period T _s , the pulse wave propagation velocity PWV, the reference blood vessel diameter D0 _s for the systolic period, and the reference blood pressure P0 _s according to the equation (1). Calculate (step S15).

  Thereafter, while the blood pressure measurement is not finished (step S17: NO), the processes of steps S11 to S15 are repeatedly executed for each beat.

  Next, the blood vessel position selection process started in step S7 will be described. FIG. 22 is a flowchart showing the flow of the blood vessel position selection process, and the blood vessel position selection unit 372 performs the process shown in FIG. 22 for each slice position. That is, first, the reflected wave data generation unit 373 starts the reflected wave data generation process (step S711). By the processing started here, an ultrasonic image of the slice plane is generated for each frame at the corresponding slice position, and the image data is stored in the reflected wave data 394.

  Subsequently, the blood vessel diameter calculation unit 375 extracts feature points from the ultrasound image of the current frame and detects the blood vessel 9 (step S713). By this processing, the positions of the blood vessel center and the front and rear walls are obtained. Thereafter, the blood vessel diameter calculation unit 375 calculates the blood vessel diameter from the obtained positions of the blood vessel center and the front and rear walls (step S715).

  Subsequently, the blood vessel diameter calculation unit 375 sets a scanning line passing through the vicinity of the blood vessel center as a central scanning line (step S717). Thereafter, after waiting for the generation of the ultrasonic image of the next frame, the blood vessel diameter is calculated by tracking the positions of the blood vessel center and the front and rear walls in the next frame (step S719). Prior to the processing here, the tracking unit 374 starts tracking using the front wall position and the rear wall position calculated in step S713 as tracking points.

  Subsequently, the blood vessel diameter calculation unit 375 performs a positional deviation determination process (step S721). And when it determines with the position shift of the blood vessel 9 having generate | occur | produced (step S723: YES), a center scanning line is updated by performing the process of step S713-step S717 about the present flame | frame. On the other hand, while the blood vessel 9 is not misaligned (step S723: NO) and the blood pressure measurement is not completed (step S725: NO), the processing of step S719 and step S721 is repeatedly executed to determine the position of the blood vessel 9. The blood vessel diameter is calculated for each frame while monitoring the deviation.

  As described above, according to the present embodiment, the blood vessel diameter can be calculated at a high frame rate at a plurality of slice positions, and the pulse wave velocity PWV can be accurately measured from the blood vessel diameter fluctuation waveform. Moreover, the blood pressure of every beat can be measured using the measured pulse wave propagation velocity PWV.

  In the above-described embodiment, an example in which a two-dimensional plane wave covering the entire region of the target portion 73 is irradiated at a time by one ultrasonic measurement has been given (see FIG. 2). On the other hand, the ultrasonic element 11 is selectively used to transmit and receive ultrasonic waves to partially irradiate the target site with a two-dimensional plane wave, and perform multiple ultrasonic measurements in each frame while changing the irradiation range. It may be configured to be repeated. For example, as illustrated in FIG. 23, two-dimensional plane waves 110a and 110b may be sequentially irradiated onto the target portion 73 in two steps. In this case, the frame rate is halved, but the circuit scale of the transmission / reception circuit used in one ultrasonic measurement can be reduced.

  Alternatively, as illustrated in FIG. 24, a plurality (for example, two) of two-dimensional array ultrasonic units 10a and 10b each including a plurality of ultrasonic elements 11 arranged therein are installed along the blood vessel long axis direction. The ultrasonic units 10a and 10b may transmit and receive ultrasonic waves to different longitudinal positions of the blood vessel 9. In the case of this modification, each of the ultrasonic units 10a and 10b can simultaneously irradiate the target part with a two-dimensional plane wave and perform ultrasonic measurement in parallel.

  DESCRIPTION OF SYMBOLS 100 ... Pulse wave propagation velocity calculation apparatus, 1 ... Blood pressure measurement apparatus, 10 ... Ultrasonic unit, 11 ... Ultrasonic element, 20 ... Ultrasonic measurement part, 30 ... Processing apparatus, 31 ... Operation input part, 33 ... Display part, 35 ... Communication unit, 37 ... Arithmetic processing unit, 371 ... Transmission / reception control unit, 372 ... Blood vessel position selection unit, 373 ... Reflected wave data generation unit, 374 ... Tracking unit, 375 ... Blood vessel diameter calculation unit, 376 ... Slice plane setting unit 377: Feature period determination unit, 378 ... Heart rate determination unit, 379 ... Pulse wave propagation velocity calculation unit, 380 ... Blood pressure calculation unit, 381 ... Time measurement unit, 39 ... Storage unit, 391 ... Blood pressure measurement program, 392 ... Reference value data 393: Received signal data, 394: Reflected wave data, 395 ... Tracking data, 396 ... Blood vessel position data, 397 ... Blood vessel diameter log data, 398 ... PWV log data, 399 ... Blood pressure Gudeta, 7 ... the subject, 9 ... blood vessels

Claims (8)

An ultrasonic unit for transmitting a two-dimensional plane wave to a blood vessel of an artery and receiving a reflected wave;
An arithmetic processing unit that performs signal processing on the received signal of the reflected wave;
With
The arithmetic processing unit includes:
Performing reception beam forming based on the reception signal of the reflected wave, and selecting a first blood vessel position and a second blood vessel position having different positions in the major axis direction of the blood vessel;
Detecting a first blood vessel diameter fluctuation timing of the blood vessel at the first blood vessel position and a second blood vessel diameter fluctuation timing of the blood vessel at the second blood vessel position;
Measuring the pulse wave velocity using the first blood vessel diameter fluctuation timing and the second blood vessel diameter fluctuation timing;
Pulse wave velocity measuring device that performs. The selection is
Performing reception focus processing on the received signal related to the short-axis cross section of the blood vessel including the first blood vessel position to select the first blood vessel position;
Performing a reception focus process on the received signal related to the short-axis cross section of the blood vessel including the second blood vessel position to select the second blood vessel position;
The pulse wave velocity measuring device according to claim 1, comprising: The arithmetic processing unit includes:
Identifying the major axis direction of the blood vessel from the first blood vessel position and the second blood vessel position;
Setting the short-axis cross section to be orthogonal to the identified long-axis direction;
The pulse wave velocity measuring device according to claim 2, further comprising: The measuring is
The first blood vessel diameter variation timing, the second blood vessel diameter variation timing, and the distance between the first blood vessel position and the second blood vessel position along the specified major axis direction; Measuring the pulse wave velocity using
The pulse wave velocity measuring device according to claim 3, comprising: The selecting includes selecting three or more blood vessel positions having different positions in the longitudinal direction of the blood vessel, including the first blood vessel position and the second blood vessel position;
The detecting includes detecting a vascular diameter variation timing for each of the selected three or more vascular positions;
The measuring includes measuring the pulse wave velocity using a blood vessel diameter variation timing for each of the three or more blood vessel positions;
The pulse wave velocity measuring device according to any one of claims 1 to 4. The selecting includes tracking the blood vessel position by selecting the blood vessel position in a predetermined cycle;
The measuring includes measuring the pulse wave velocity every beat;
The pulse wave velocity measuring device according to any one of claims 1 to 5. Comprising the pulse wave velocity measuring device according to any one of claims 1 to 6,
The arithmetic processing unit uses a blood vessel diameter at the first blood vessel position or a blood vessel diameter at the second blood vessel position, the pulse wave velocity, a given reference blood vessel diameter, and a given reference blood pressure. Calculating blood pressure
Blood pressure measurement device. A pulse wave velocity measurement method using an ultrasonic unit that transmits a two-dimensional plane wave to a blood vessel of an artery and receives a reflected wave,
Performing reception beam forming based on the reception signal of the reflected wave, and selecting a first blood vessel position and a second blood vessel position having different positions in the major axis direction of the blood vessel;
Detecting a first blood vessel diameter fluctuation timing of the blood vessel at the first blood vessel position and a second blood vessel diameter fluctuation timing of the blood vessel at the second blood vessel position;
Measuring the pulse wave velocity using the first blood vessel diameter fluctuation timing and the second blood vessel diameter fluctuation timing;
A pulse wave velocity measurement method including