JP2008161546A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus which acquires tissue characteristics of cardiovascular tissues more accurately. <P>SOLUTION: The ultrasonic diagnostic apparatus includes a transmission section 14 for driving an ultrasonic probe 13, a reception section 15 for generating received signals by receiving an ultrasonic reflected wave obtained when the cardiovascular tissues of a living body reflect the ultrasound transmitting waves by using the ultrasonic probe 13, a phase detecting section 17 for generating a phase detection signal from the received signal, a shape characteristics operation section 31 which respectively operates the amount of positional displacement at a plurality of positions to be measured set at the cardiovascular tissues of the living body from the phase detection signals and operates a plurality of shape characteristic values between arbitrary two points set from the plurality of positions to be measured from the amount of positional displacement, a blood pressure correction operation section 33 which receives a blood pressure value on the cardiovascular tissues of the living body and corrects the blood pressure value, and a property characteristic operation section 32 for operating a plurality of nature characteristic values from the plurality of shape characteristic values and the corrected blood pressure value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus capable of measuring the elastic characteristics and viscosity characteristics of an arterial vascular wall tissue.

  In recent years, an increasing number of people suffer from cardiovascular diseases such as myocardial infarction and cerebral infarction, and it has become a major issue to prevent and treat such diseases.

  Arteriosclerosis is closely related to the onset of myocardial infarction and cerebral infarction. Specifically, when an atheroma is formed on the artery wall, or when new cells of the artery are not made due to various factors such as hypertension, the artery loses its elasticity and becomes hard and brittle. Then, the blood vessel is blocked in the part where the atheroma is formed, or the vascular tissue covering the atheroma is ruptured and the atheroma flows into the blood vessel, and the artery is blocked in another part or the artery is hardened. These diseases are caused by the rupture of parts. Therefore, early diagnosis of arteriosclerosis is important for the prevention and treatment of these diseases.

  Conventionally, arteriosclerotic lesions have been diagnosed by directly observing the inside of a blood vessel using a vascular catheter. However, this diagnosis has a problem that the load on the subject is large because it is necessary to insert a vascular catheter into the blood vessel. For this reason, observation with a vascular catheter is used to identify the location of a subject who is certain that an arteriosclerotic lesion is present. For example, this method can be used as a test for health care. It was never used.

  Measuring a cholesterol level that is a cause of arteriosclerosis or measuring a blood pressure level is a test that can be easily performed with less burden on the subject. However, these values do not directly indicate the degree of arteriosclerosis.

  Further, if arteriosclerosis is diagnosed at an early stage and a therapeutic drug for arteriosclerosis can be administered to a subject, it will be effective in treating arteriosclerosis. However, when arteriosclerosis progresses, it is said that it is difficult to completely recover the cured artery even though the therapeutic agent can suppress the progress of arteriosclerosis.

  For these reasons, there is a need for a diagnostic method or a diagnostic device that has less burden on the subject and diagnoses at an early stage before arteriosclerosis proceeds.

  On the other hand, an ultrasonic diagnostic apparatus and an X-ray diagnostic apparatus are conventionally used as a non-invasive medical diagnostic apparatus that places little burden on the subject. By irradiating ultrasonic waves or X-rays from outside the body, it is possible to obtain shape information in the body or time change information of the shape without causing pain to the subject. When time change information (motion information) of the shape of the measurement object in the body is obtained, the property information of the measurement object can be obtained. That is, the elasticity characteristic of the blood vessel in the living body can be obtained, and the degree of arteriosclerosis can be directly known.

  In particular, ultrasound diagnosis is superior to X-ray diagnosis in that it can be measured simply by applying an ultrasound probe to a subject, and therefore there is no need for administration of a contrast agent to the subject and there is no risk of X-ray exposure. Yes.

  In addition, recent advances in electronics technology have made it possible to dramatically improve the measurement accuracy of ultrasonic diagnostic equipment. Along with this, development of ultrasonic diagnostic apparatuses that measure minute movements of living tissues is progressing. For example, when the technique described in Patent Document 1 is used, it is possible to measure a high-speed vibration component up to several hundred Hz with an amplitude of several microns of vasomotion with high accuracy. It is reported that it will be possible to measure with high accuracy.

By using such a highly accurate measurement method, it is possible to measure in detail the two-dimensional distribution of the elastic characteristics of the artery wall. For example, Non-Patent Document 1 shows an example in which the state of the two-dimensional distribution of the elastic modulus of the carotid artery wall is displayed superimposed on the B-mode tomographic image. The degree of stiffness of the arterial wall is not uniform and has a certain distribution, and in the diagnosis of arteriosclerosis, the local distribution of the elastic modulus, which is a characteristic amount indicating the degree of hardening of the artery, is accurately determined. This is because it is important to understand.
Japanese Patent Laid-Open No. 10-5226 Hiroshi Kanai et al, "Elasticity Imaging of Atheroma With Transcutaneous Ultrasound Preliminary Study," Circulation, Vol.107, p.3018-3021, 2003.

  When arteriosclerosis progresses, a tumor called a atheroma that contains a large amount of lipid in the interior is generated, or the inner-media thickness is increased, resulting in a stenosis in the blood vessel. When blood flows from a portion having a large blood vessel cross-sectional area without stenosis into a stenosis portion having a small blood vessel cross-sectional area, the flow velocity increases. According to Bernoulli's theorem, the following equation holds for a continuous fluid.

  Here, p is blood pressure, ρ is blood density, and v is blood flow velocity. From formula (1), when a stenosis part is generated and generated in an arterial blood vessel, it is considered that the blood pressure in that part is lowered.

  However, conventional ultrasonic diagnostic apparatuses have been demanding elastic characteristics without considering such a decrease in blood pressure. For this reason, according to the conventional ultrasonic diagnostic apparatus, there is a possibility that the measurement of the elastic characteristics of the tumor portion of the arterial blood vessel wall and the portion where the inner-media thickness is thickened may be inaccurate.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of solving such problems and obtaining more accurate elastic characteristics of a blood vessel wall.

  The ultrasonic diagnostic apparatus according to the present invention includes a transmitter that drives an ultrasonic probe for transmitting an ultrasonic transmission wave to a circulatory tissue of a living body, and the ultrasonic transmission wave is reflected by the circulatory tissue of the living body. Receiving the ultrasonic reflected wave obtained by using the ultrasonic probe, generating a received signal, phase detecting the received signal, generating a phase detection signal, and the phase detection The position displacement amount at each of a plurality of measurement target positions set in the circulating tissue of the living body is calculated from the signal, and the shape between any two points set based on the plurality of measurement target positions from the position displacement amount A shape characteristic calculation unit that calculates a plurality of characteristic values; a blood pressure correction calculation unit that receives a blood pressure value related to the circulatory tissue of the living body and corrects the blood pressure value; and the plurality of shape characteristic values and the corrected blood pressure value. And Zui, and a property characteristic calculator for calculating a plurality of attribute property values.

  In a preferred embodiment, the circulatory tissue is a blood vessel, and the blood pressure correction calculation unit corrects the blood pressure value according to a change in blood vessel shape in the axial direction of the blood vessel.

  In a preferred embodiment, the blood pressure correction calculation unit corrects the blood pressure value in accordance with a change in cross-sectional area in the axial direction of the blood vessel.

  In a preferred embodiment, the blood pressure correction calculation unit corrects the blood pressure value according to a change in an inner diameter in the axial direction of the blood vessel.

  In a preferred embodiment, the circulatory tissue is a blood vessel, and the ultrasonic diagnostic apparatus further includes a blood flow velocity calculating unit that calculates a blood flow velocity of blood moving through the blood vessel using a Doppler method, The blood pressure correction calculation unit corrects the blood pressure value according to a change in blood flow velocity in the axial direction of the blood vessel.

  In a preferred embodiment, the ultrasonic diagnostic apparatus displays at least one of the plurality of property characteristic values, an average value of the plurality of property characteristic values, or a distribution image of the plurality of property characteristic values. And a display unit.

  In a preferred embodiment, the property characteristic value is at least one of an elastic characteristic and a viscous characteristic.

  In a preferred embodiment, the blood pressure correction calculation unit corrects the blood pressure value in synchronization with a heartbeat.

  According to the ultrasonic diagnostic apparatus of the present invention, the blood pressure correction calculation unit corrects the blood pressure value for each position for obtaining the property characteristic. Therefore, the elastic characteristic of the vascular wall tissue in the stenosis of the blood vessel can be obtained more accurately.

  Hereinafter, embodiments of an ultrasonic diagnostic apparatus according to the present invention will be described.

  FIG. 1 is a block diagram showing a configuration for diagnosing a vascular wall tissue property using the ultrasonic diagnostic apparatus 11 of the present embodiment. The ultrasonic probe 13 connected to the ultrasonic diagnostic apparatus 11 is installed in close contact with the body surface 2 of the subject, and transmits ultrasonic waves to the inside of the extravascular tissue 1. The transmitted ultrasonic wave is reflected and scattered by the blood vessel 3 and the blood 5, and a part thereof returns to the ultrasonic probe 13 and is received as an echo (ultrasonic reflected wave). The ultrasonic diagnostic apparatus 11 analyzes and calculates the received signal and obtains shape information and motion information of the blood vessel front wall 4. In addition, a blood pressure monitor 12 is connected to the ultrasonic diagnostic apparatus 11, and blood pressure data of the subject measured by the blood pressure monitor 12 is input to the ultrasonic diagnostic apparatus 11. The ultrasonic diagnostic apparatus 11 determines the instantaneous position of the object by the constrained least square method using both the amplitude and the phase of the detection signal, for example, according to the method disclosed in Patent Document 1. By performing phase tracking with high accuracy (positional change measurement accuracy is ± 0.2 micron), the thickness of the minute part on the blood vessel front wall 4 and the state of the time change of the thickness change amount are measured with sufficient accuracy. be able to. Furthermore, by using the blood pressure data obtained from the sphygmomanometer 12, the elastic characteristics of the local minute part in the blood vessel front wall 4 can be obtained. An electrocardiograph 22 is connected to the ultrasonic diagnostic apparatus 11, and an electrocardiographic waveform measured by the electrocardiograph 22 is input to the ultrasonic diagnostic apparatus 11 to determine the timing of data acquisition and data reset. Used as a trigger signal. The electrocardiograph 22 can be replaced with other sound signal detectors such as a heart sound meter and a pulse wave meter, and an electrocardiographic waveform and a pulse wave waveform can be used as a trigger signal instead of the electrocardiographic waveform.

  Hereinafter, the configuration and operation of the ultrasonic diagnostic apparatus 11 will be described in detail. In conventional ultrasonic diagnostic apparatuses, it has been assumed that blood pressure, which is a stress that causes elastic deformation in a blood vessel wall, is constant regardless of the position of the blood vessel. On the other hand, in the ultrasonic diagnostic apparatus 11 of the present embodiment, the blood pressure is corrected in the axial direction of the blood vessel in consideration of the change in the shape of the blood vessel wall due to the occurrence of a stenosis, and the corrected blood pressure value is used. To obtain elastic properties.

  FIG. 2 is a block diagram showing a configuration of the ultrasonic diagnostic apparatus 11. The ultrasonic diagnostic apparatus 11 includes a transmission unit 14, a reception unit 15, a delay time control unit 16, a phase detection unit 17, a filter unit 18, a calculation unit 19, a storage unit 20, and a display unit 21. In addition, a user interface 25 for an operator to give a command to the ultrasonic diagnostic apparatus 11 and a control unit 23 composed of a microcomputer or the like for controlling each of these components based on the command from the user interface 25 are provided. . Note that each component shown in FIG. 2 is not necessarily configured by independent hardware. For example, each part of the calculating part 19 demonstrated in detail below is comprised by the microcomputer and software, and the function of each part may be implement | achieved.

  The transmission unit 14 generates a predetermined drive pulse signal and outputs it to the ultrasonic probe 13. The ultrasonic transmission wave transmitted from the ultrasonic probe 13 by the drive pulse signal is reflected and scattered by a living tissue such as the blood vessel 3, and the generated ultrasonic reflected wave is received by the ultrasonic probe 13. The frequency of the drive pulse for generating the ultrasonic wave is determined in consideration of the depth of the measurement target and the ultrasonic velocity so that the adjacent ultrasonic pulses adjacent on the time axis do not overlap.

  The receiving unit 15 receives an ultrasonic reflected wave using the ultrasonic probe 13. The reception unit 15 includes an A / D conversion unit, amplifies the ultrasonic reflected wave, generates a reception signal, and further converts it into a digital signal. The transmission unit 14 and the reception unit 15 are configured using electronic components.

  The delay time control unit 16 is connected to the transmission unit 14 and the reception unit 15 and controls the delay time of the drive pulse signal given from the transmission unit 14 to the ultrasonic transducer group of the ultrasonic probe 13. Thereby, the direction of the acoustic line of the ultrasonic beam of the ultrasonic transmission wave transmitted from the ultrasonic probe 13 and the depth of focus are changed. Further, by controlling the delay time of the received signal received by the ultrasonic probe 13 and amplified by the receiving unit 15, the aperture diameter can be changed or the focal position can be changed. The output of the delay time control unit 16 is input to the phase detection unit 17.

  The tomographic image generation unit 24 includes a filter, a logarithmic amplifier, a detector, and the like, and converts the received signal received from the delay time control unit 16 into a signal having luminance information corresponding to the signal intensity. Thereby, a signal indicating a tomographic image in the measurement region of the subject is obtained.

  The phase detection unit 17 performs phase detection on the reception signal subjected to delay control by the delay time control unit 16 and separates it into a real part signal and an imaginary part signal. The separated real part signal and imaginary part signal are input to the filter unit 18. The filter unit 18 removes a high frequency component, a reflection component other than a measurement target, a noise component, and the like. The phase detection unit 17 and the filter unit 18 can be configured by software or hardware. The real part signal and the imaginary part signal of the reception signal subjected to phase detection are input to the calculation unit 19.

  FIG. 3 is a block diagram showing the configuration of the calculation unit 19 in detail. The calculation unit 19 includes a shape characteristic calculation unit 31, a property characteristic calculation unit 32, and a blood pressure correction calculation unit 33. The calculation unit 19 can be configured by software or hardware.

  Based on the real part signal and the imaginary part signal of the received signal, the shape characteristic calculation unit 31 obtains the movement speed of the living tissue at a plurality of measurement target positions, and integrates the movement speed to thereby calculate the position displacement amount (position time). (Displacement). From the obtained position displacement amount, the thickness change amount (stretching amount) and the change amount of the blood vessel diameter between the measurement target positions are obtained. In addition, information on one cardiac cycle is received from the electrocardiograph 22, and the maximum thickness variation and the maximum thickness, which are the difference between the maximum value and the minimum thickness variation in one cardiac cycle, are obtained.

  The blood pressure correction calculation unit 33 receives blood pressure data from the sphygmomanometer 12, and corrects the received blood pressure data in accordance with a difference in shape of the blood vessel in the axial direction, that is, a change in cross-sectional area or a change in inner diameter in the axial direction. Alternatively, the received blood pressure data is corrected according to a change in blood flow velocity in the axial direction of the blood vessel. The blood pressure data correction method will be described in detail below.

  The property characteristic calculation unit 32 receives the maximum thickness change amount and the maximum value (or initial value) of the thickness, and obtains the distortion of the living tissue. Furthermore, using the blood pressure data corrected by the blood pressure correction calculation unit 33, the elastic characteristic of the tissue between the measurement target positions is obtained.

  The maximum change in thickness, strain, or elastic characteristic of the biological tissue thus obtained is mapped corresponding to the measurement region, and a spatial distribution frame for each cardiac cycle showing the spatial distribution of these multiple values. The data is output to the display unit 21. Further, what is displayed on the display unit 21 may be the plurality of values themselves or an average value thereof. A tomographic image signal generated by the tomographic image generation unit 24 is also input to the display unit 21, and a tomographic image of the measurement region is displayed on the display unit 21.

  Next, the calculation in the calculation unit 19 will be described in more detail with reference to FIGS. 4 and 5. FIG. 4 schematically shows an ultrasonic beam 67 propagating through the living body 60. In the figure, a blood vessel wall 64 and a living tissue 62 other than the blood vessel are shown. The ultrasonic wave transmitted from the ultrasonic probe 13 disposed on the surface of the living body 60 travels through the living body 60. The ultrasonic transmission wave propagates through the living body 60 as an ultrasonic beam 67 having a certain finite width, and a part of the ultrasonic wave reflected or scattered by the living tissue 62 and the blood vessel wall 64 in the process is sent to the ultrasonic probe 13. Returned and received as an ultrasonic reflected wave. The reflected ultrasonic wave is detected as a time series signal r (t), and the reflected time series signal obtained from the tissue closer to the ultrasonic probe 13 is located closer to the origin on the time axis. The width (beam diameter) of the ultrasonic beam 67 can be controlled by changing the delay time.

  A plurality of measurement target positions Pn (P1, P2,... Pk... Pn, n is a natural number of 3 or more) in the blood vessel wall 62 located on the acoustic line 66 that is the central axis of the ultrasonic beam is P 1, P 2,... Pk... Pn are arranged in order from the ultrasonic probe 13 at a constant interval L. If the coordinates in the depth direction with the surface of the living body 60 as the origin are Z1, Z2,... Zk... Zn, the reflection from the measurement target position Pk is located at tk = 2Zk / c on the time axis. It will be. Here, c indicates the sound speed of the ultrasonic wave in the living body. The reflected wave signal r (t) is phase-detected by the phase detection unit 17, and the detected signal is separated into a real part signal and an imaginary part signal and passed through the filter unit 18. In the shape measurement value calculation unit 31 of the calculation unit 19, the amplitude does not change in the reflected wave signal r (t) and the reflected wave signal r (t + Δt) after a minute time Δt, and only the phase and the reflection position change. Originally, the phase difference is obtained by the least square method so that the waveform matching error between the reflected wave signals r (t) and r (t + Δt) is minimized. From this phase difference, the motion speed Vn (t) of the measurement target position Pn is obtained, and the position displacement amount dn (t) can be obtained by further integrating this.

  FIG. 5 shows the relationship between the measurement target position Pn and the target tissue Tn for elastic characteristic calculation. The target tissue Tk is located with a thickness L in a range between adjacent measurement target positions Pk and Pk + 1. (n−1) target tissues T1,... Tn−1 can be provided from the n measurement target positions P1,.

  The thickness change amount Hk (t), which is the amount of expansion / contraction of the target tissue Tk, is calculated from Hk (t) = hk + 1 (t) − from the position displacement amounts hk (t) and hk + 1 (t) of the measurement target positions Pk and Pk + 1. It is obtained as hk (t).

  The change in the thickness of the tissue Tk of the blood vessel wall 64 occurs according to the change in blood pressure due to the heartbeat, and is repeated approximately in synchronization with the cardiac cycle. Therefore, it is preferable to obtain a numerical value for each heartbeat in synchronization with the cardiac cycle. The maximum value and the minimum value are extracted from the thickness change amount Hk (t) in one cardiac cycle, and the difference between the maximum value and the minimum value is set as the maximum thickness change amount Δhk. Further, the difference between the maximum value and the minimum value of the blood pressure is set as the pulse pressure Δp. When the maximum value (or initial value) of the thickness of the target tissue is Hm, the strain Sk and the elastic characteristic xk can be obtained by the following equations, respectively.

Sk = Δhk / Hm
xk = Δp / Sk = Δp · Hm / Δhk

  The number of measurement target positions Pn and their intervals can be arbitrarily set in accordance with the purpose of measurement and the characteristics of the biological tissue that is the measurement target. In the above description, an example in which the thickness change amount and the elastic characteristic between adjacent measurement target positions is obtained is shown. However, the thickness change amount and the elastic characteristic are two points sandwiching one or more measurement target positions. A value between may be obtained. In this case, as the positional displacement amount between the two points, it is preferable to use an average value of the positional displacement amounts of the two points and the measurement target position therebetween.

  The range for obtaining the amount of change in thickness and the elastic characteristics may be one place between any two points, but the ultrasonic probe 13 used in the present embodiment has a plurality of superstructures arranged in an array. It has a sound wave vibrator, and it is possible to obtain the elastic characteristics of all locations in an arbitrary region within the tomographic plane.

  By the above procedure, the calculation unit 19 calculates image information by calculating the maximum thickness change amount, strain, elastic property, etc. of the living tissue, and the image is displayed on the display unit 21. Further, data such as the maximum thickness variation, strain, and elastic characteristics calculated by the measurement unit 32, images, and tomographic images are stored in the storage unit 20 within the range allowed by the storage capacity, and can be read at any time. . If an element such as a ring memory is used for the storage unit 20, for example, the latest data can always be updated and stored. Therefore, various data stored in the storage unit 20 can be displayed on the display unit 21 as needed. Further, a plurality of frames stored in the storage unit 20 may be averaged in the time direction to generate a single distribution image.

  Next, the operation of the blood pressure correction calculation unit 33 will be described in detail. FIG. 6 schematically shows an example in which a B-mode tomographic image having a cross section parallel to the axial direction of the carotid artery blood vessel wall is displayed on the display unit 21 using the ultrasonic diagnostic apparatus 11. In the tomographic image 101, the blood vessel front wall 102, the lumen 103, the blood vessel rear wall 104, the extravascular tissue 106, and the like are displayed with different luminances. In the lumen 103, blood 105 flows from the left to the right in the figure. In the stenosis 107, a part of the blood vessel rear wall 104 is thickened, and the inner diameter of the blood vessel is smaller than that of a portion where no stenosis exists (hereinafter, a normal part).

  Here, the blood vessel inner diameter of the normal portion is d, the blood pressure is p, the blood flow velocity is v, the blood density is ρ, the minimum inner diameter in the stenosis 107 is d ′, the blood pressure is p ′, and the blood flow velocity is v ′. Then, the following relation is established from Bernoulli's theorem (Equation (1)).

  In addition, since the product of the blood vessel cross-sectional area and the blood flow velocity is constant, the following relationship holds when the blood vessel cross-sectional shape is a circle.

  From equations (2) and (3), blood pressure p 'is obtained from equation (4).

  Therefore, when the inner diameter of the blood vessel varies depending on the position in the axial direction, the blood pressure correction calculation unit 33 obtains the inner diameter of the blood vessel for each position where the elastic characteristic is obtained, and corrects the blood pressure value using Equation (4) based on the obtained inner diameter. To do. The corrected blood pressure value is output to the property characteristic calculator 32. Thereby, the property characteristic calculating part 32 can obtain | require a more exact elastic characteristic. In order to obtain the inner diameter change depending on the position of the blood vessel in the axial direction, the blood pressure correction calculation unit 33 receives, for example, a tomographic image signal, and calculates the difference in signal intensity between the lumen 103 and the blood vessel front wall 102 and blood vessel rear wall 104. Use this to determine the inner diameter of the blood vessel. The lumen 103 is filled with blood, and the acoustic impedance is greatly different from that of the blood vessel front wall 102 and the blood vessel rear wall 104, which are blood vessel wall tissues. Therefore, the inner diameter of the blood vessel can be obtained relatively accurately and automatically.

  When obtaining the elastic characteristics of the vascular wall tissue, it is only necessary to know the pulse pressure Δp, which is the difference between the systolic blood pressure and the diastolic blood pressure that give the maximum amount of change in the vascular wall tissue thickness. Therefore, it is not necessary for the blood pressure correction calculation unit 33 to always perform correction calculation of the blood pressure value, and it is only necessary to correct the systolic blood pressure and the diastolic blood pressure once in each cardiac cycle. Therefore, the correction calculation is preferably performed in synchronization with the cardiac cycle. A signal synchronized with the cardiac cycle may be obtained from the electrocardiograph 22, or the time variation of the inner diameter calculated by the shape characteristic calculator 31 or the time displacement of an arbitrary position of the blood vessel 3 may be used.

  Equation (3) shows the relationship when the cross-sectional shape of the blood vessel is a circle, but there are actually cases where the cross-sectional shape of the blood vessel is not a circle. In this case, it is preferable that the blood pressure correction calculation unit 33 corrects the received blood pressure data in accordance with the change in the cross-sectional area in the axial direction.

  For this purpose, the ultrasonic diagnostic apparatus 11 transmits and receives ultrasonic waves so that a B-mode tomographic image having a cross section perpendicular to the axial direction of the blood vessel can be obtained at each position where the elastic characteristics are obtained. The tomographic image generation unit 24 generates a cross-sectional tomographic image signal perpendicular to the axial direction of the blood vessel and outputs it to the blood pressure correction calculation unit 33.

  The blood pressure correction calculation unit 33 obtains the blood vessel cross-sectional area from the intensity of the tomographic image signal in the same manner as the calculation of the inner diameter of the blood vessel. Alternatively, the blood pressure correction calculation unit 33 may obtain a cross-sectional area by approximating a cross section to an ellipse from the tomographic image.

  Assuming that the blood vessel cross-sectional area of the normal part is S and the cross-sectional area of the stenotic part 107 where the inner diameter is minimum is S ', the blood pressure p' is obtained by

  Therefore, the blood pressure correction calculation unit 33 can correct the blood pressure by substituting the obtained cross-sectional area into the equation (5). As described above, when the cross-sectional area of the blood vessel is different in the direction of the blood vessel axis, it is possible to obtain a more accurate elastic characteristic by correcting the blood pressure value at each position where the elastic characteristic is obtained.

  In addition, the blood pressure correction calculation unit 33 may correct the blood pressure value based on the blood flow velocity. In general, an ultrasonic diagnostic apparatus has a blood flow velocity calculation function using a Doppler method. Therefore, if this function is used, the blood pressure value can be corrected without adding a new configuration to the ultrasonic diagnostic apparatus.

  When the blood flow velocity v in the normal portion and the blood flow velocity v ′ in the stenosis 107 are expressed, the blood pressure p ′ in the stenosis 107 is expressed by the following formula (6).

  When correcting the blood pressure value based on the blood flow velocity, the ultrasonic diagnostic apparatus 11 further includes a blood flow velocity calculator 34 as shown in FIG. Such a function is provided in a general ultrasonic diagnostic apparatus as described above. The blood flow velocity calculation unit 34 obtains a blood flow velocity for each position where the elastic characteristic in the axial direction is obtained by analyzing the received signal obtained based on the Doppler method. The blood pressure correction calculation unit 33 receives the blood flow velocity, and corrects the blood pressure value using Equation (6).

  It should be noted that the average blood flow velocity in the blood vessel is used as the blood flow velocity v and v ′ used in the equations (1) to (6). It should be noted that the relationship between the flow velocity at the center and the average flow velocity is different between the case where the blood flow flowing in the blood vessel is laminar and the case of turbulent flow. When the cross section of the blood vessel is a circle, the average flow velocity in the blood vessel is ½ of the central velocity of the blood vessel in the case of laminar flow, but 0.81 to 0.83 times the central velocity in the case of turbulent flow. Become.

  As described above, according to the ultrasonic diagnostic apparatus of this embodiment, the blood pressure correction calculation unit 33 calculates the blood pressure value for each position where the elastic characteristic is obtained based on the inner diameter of the blood vessel, the cross-sectional area of the blood vessel, or the blood flow velocity. to correct. Therefore, the elastic characteristic of the vascular wall tissue in the stenosis of the blood vessel can be obtained more accurately. In particular, because the stenosis of the blood vessel is formed by a tumor that has occurred in the arterial blood vessel wall or by thickening of the medial thickness, it is possible to obtain a more accurate determination of the elastic characteristics of the diseased tissue, thereby causing a lesion in the arterial blood vessel. Can be accurately diagnosed.

  In the present embodiment, the blood pressure p in the carotid artery may be directly measured by a catheter or the like, or may be obtained by adding an arbitrary coefficient to the upper arm blood pressure measurement value. Furthermore, the upper arm blood pressure measurement value may be used as it is as the carotid blood pressure value. The main factor for stenosis of blood vessels is the presence of atheroma (plaque), and the most important factor in diagnosing atheroma is said to be easily ruptured. When an atheroma ruptures, its contents occlude blood vessels in the periphery and cause cerebral infarction or myocardial infarction. Therefore, the diagnosis point is whether the elasticity of the vascular tissue covering the atheroma is high (hard) or low (soft) Become. Therefore, even if the brachial blood pressure measurement value is used as the carotid artery blood pressure value, it is possible to know the relative hardness and softness of the surrounding normal tissue, and it is possible to provide very useful information to the doctor. It becomes.

  Furthermore, although the elastic characteristic is calculated | required in this embodiment, you may obtain | require other property characteristic values. For example, since stress is also used for calculating the viscosity coefficient of the vascular wall tissue, a more accurate viscosity coefficient can be obtained by correcting the blood pressure value for each measurement position in the axial direction by the blood pressure correction calculation unit.

  The ultrasonic diagnostic apparatus of the present invention is suitably used for measuring property characteristics such as elastic properties in a minute part in a circulatory tissue, and in particular, accurately characterizes property characteristics such as elastic properties and viscosity properties of arterial vessel wall tissue. It is suitably used for measurement.

It is a block diagram which shows the structure for diagnosing the vascular wall tissue property using the ultrasonic diagnosing device by this invention. It is a block diagram which shows the structure of embodiment of the ultrasonic diagnosing device by this invention. It is a block diagram which shows in detail the structure of the calculating part of the ultrasonic diagnosing device shown in FIG. It is a figure which shows typically the ultrasonic beam which propagates the blood vessel wall, and a measurement object position. It is a figure which shows the relationship between a measurement object position and the object structure | tissue which calculates | requires an elastic characteristic. It is a figure which shows typically the example of a display of the B mode tomogram of a cross section parallel to the axial direction of the carotid artery measured using the ultrasonic diagnostic apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extravascular tissue 2 Body surface 3 Blood vessel 4 Blood vessel front wall 5 Blood 11 Ultrasound diagnostic apparatus 12 Sphygmomanometer 13 Ultrasonic probe 14 Transmission part 15 Reception part 16 Delay time control part 17 Phase detection part 18 Filter part 19 Calculation part 20 Memory | storage Unit 21 display unit 22 electrocardiograph 23 control unit 24 tomographic image generation unit 25 user interface 31 shape characteristic calculation unit 32 property characteristic calculation unit 33 blood pressure correction calculation unit 34 blood flow velocity calculation unit 101 tomographic image 102 blood vessel front wall 103 lumen 104 Blood vessel rear wall 105 Blood 106 Extravascular tissue 107 Stenosis

Claims (8)

A transmitter for driving an ultrasonic probe for transmitting an ultrasonic transmission wave to a living body circulatory tissue;
A reception unit that receives an ultrasonic reflected wave obtained by reflecting the ultrasonic transmission wave in the circulatory tissue of the living body using the ultrasonic probe, and generates a reception signal;
A phase detection unit that phase-detects the received signal and generates a phase detection signal;
From the phase detection signal, position displacement amounts at a plurality of measurement target positions set in the circulating tissue of the living body are respectively calculated, and two arbitrary points set based on the plurality of measurement target positions from the position displacement amounts A shape characteristic calculation unit for calculating a plurality of shape characteristic values between,
A blood pressure correction calculation unit that receives a blood pressure value related to the circulatory tissue of the living body and corrects the blood pressure value;
Based on the plurality of shape characteristic values and the corrected blood pressure value, a characteristic characteristic calculation unit that calculates a plurality of characteristic characteristic values;
An ultrasonic diagnostic apparatus comprising: The circulatory tissue is a blood vessel;
The ultrasonic diagnostic apparatus according to claim 1, wherein the blood pressure correction calculation unit corrects the blood pressure value according to a change in blood vessel shape in the axial direction of the blood vessel.   The ultrasonic diagnostic apparatus according to claim 2, wherein the blood pressure correction calculation unit corrects the blood pressure value according to a change in a cross-sectional area in the axial direction of the blood vessel.   The ultrasonic diagnostic apparatus according to claim 2, wherein the blood pressure correction calculation unit corrects the blood pressure value according to a change in an inner diameter in the axial direction of the blood vessel. The circulatory tissue is a blood vessel;
Further comprising a blood flow velocity calculation unit for calculating a blood flow velocity of blood moving through the blood vessel using the Doppler method,
The ultrasonic diagnostic apparatus according to claim 1, wherein the blood pressure correction calculation unit corrects the blood pressure value according to a change in blood flow velocity in the axial direction of the blood vessel.   The display unit that displays at least one of the plurality of property characteristic values, an average value of the plurality of property characteristic values, or a distribution image of the plurality of property characteristic values. An ultrasonic diagnostic apparatus according to claim 1.   The ultrasonic diagnostic apparatus according to claim 1, wherein the property characteristic value is at least one of an elastic characteristic and a viscous characteristic.   The ultrasound diagnostic apparatus according to claim 1, wherein the blood pressure correction calculation unit corrects the blood pressure value in synchronization with a heartbeat.

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