JP2003126090A - In vivo signal measurement device and ultrasonic diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the in vivo signal measurement device synchronized with a heart beat which automatically targets the signal wave ensemble mean at every heart beat cycle. SOLUTION: The R wave detector 50 detects the R wave of electrocardiac signals. A heart beat divider 52 that divides varying signals indicating the blood vessel diameter and blood velocity as well as the electrocardiac signals at the timing of the R waves, and generates a sample wave in a heart beat cycle unit. A heart beat correlation calculator 56 calculates mutual correlation among plural sample waves involved in a specified period of the varying signals of the blood vessel diameter. Based on the calculated results, a representative selector 58 selects a fixed number of highly correlated sample waves as the typical sample waves whose parameter indicates the typical sample waves to be transmitted to an ensemble mean calculator 54. The ensemble mean calculator 54 functions to ensemble means of respective signals from the sample waves indicating the variation of the blood vessel diameter, blood velocity and the electrocardiac signals to be specified by the parameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a biological signal synchronized with a heartbeat, and more particularly to an ultrasonic diagnostic apparatus for measuring displacement of blood vessel wall and blood flow velocity.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus is used for diagnosing properties of blood vessels and functions of the heart and the like. When the displacement of the blood vessel wall is measured using the ultrasonic diagnostic apparatus, the displacement signal may include a fluctuation component due to respiration. As a method of reducing this respiratory fluctuation component, the blood vessel wall displacement waveform that represents the time change of the blood vessel wall displacement is divided into sample waveforms for each heartbeat cycle, and multiple sample waveforms are ensemble averaged to generate an average waveform. There is a way to do it. The heartbeat cycle is grasped based on a characteristic waveform that appears in the electrocardiographic signal for each heartbeat.

An R wave of an electrocardiographic signal is generally used as a characteristic waveform. Conventionally, a measurer has determined a heartbeat section in which a variation between heartbeats is small in a blood vessel wall displacement signal, and, for example, moves a cursor to an R wave and manually extracts a plurality of sample waveforms used for ensemble averaging.

[0004]

However, there is a problem that the operation of selecting a plurality of sample waveforms based on the judgment of the measurer and the manual operation is complicated and time-consuming. In addition, there is a problem that the choice of the sample waveform is left to the subjectivity of the measurer, which causes a large variation in the measurement result.

The present invention has been made to solve the above problems, and automatically selects a sample waveform in a short time,
It is an object of the present invention to provide a biological signal device and an ultrasonic diagnostic device that can obtain a highly accurate ensemble average waveform.

[0006]

A biological signal measuring apparatus according to the present invention is characterized in that a reference biological signal measuring means for measuring a reference biological signal synchronized with a heartbeat and a predetermined characteristic waveform appearing in the reference biological signal are detected. A waveform detecting means, a target biological signal measuring means for measuring a target biological signal from a living body, a waveform dividing means for dividing the target biological signal waveform into a sample waveform of a heartbeat cycle based on the characteristic waveform, and Based on a predetermined condition, a representative selecting means for selecting a plurality of representative sample waveforms from the plurality of sample waveforms, and an ensemble averaging means for ensemble averaging the plurality of representative sample waveforms to obtain an average waveform of the target biological signal. .

According to the present invention, the target biomedical signal, which is originally the target biomedical signal, is divided into sample waveforms on a heartbeat cycle basis based on the reference biomedical signal having a waveform synchronized with the heartbeat. In this section, the characteristic waveform detection means detects a characteristic waveform that appears in the reference biological signal in synchronization with the heartbeat,
The feature waveform is automatically used as a reference. By ensemble averaging the sample waveforms, it is possible to reduce / remove low-frequency respiratory fluctuation components and the like compared to the heartbeat frequency. On the other hand, if the target of the ensemble average includes a peculiar sample waveform that is significantly different from other sample waveforms, the peculiarity remains in the average waveform, which is not preferable. Therefore, the representative selecting means selects, from the sample waveforms, one suitable for obtaining the average waveform by the ensemble average, based on a predetermined condition for the waveform. The ensemble averaging means ensemble averages the plurality of representative sample waveforms selected by the representative selecting means. In the ensemble averaging process, the average value of the data of the representative sample waveforms in the corresponding time phases is calculated, and the average waveform is formed from the average values in each time phase.

Another biological signal measuring apparatus according to the present invention has a correlation value calculating means for calculating a correlation value between the sample waveforms, and the representative selecting means, based on the correlation value,
A group of the sample waveforms similar to each other is selected as the representative sample waveform.

The transient noise component lowers the correlation between the sample waveform containing it and the sample waveform not containing it. Conversely, a group of sample waveforms that are correlated with each other can be expected to have less such noise components.
Therefore, in the present invention, a correlation value between sample waveforms is calculated, and a group of sample waveforms similar to each other is selected as a representative sample waveform based on the correlation value.

In a preferred aspect of the present invention, the reference signal is
It is a biological signal measuring device which is an electrocardiographic signal. In particular, the R wave of the electrocardiographic signal can be used as the characteristic waveform.

The ultrasonic diagnostic apparatus according to the present invention is a transmitting / receiving means for transmitting an ultrasonic pulse and receiving an echo signal, and a blood vessel wall displacement measuring means for measuring a displacement of a blood vessel wall based on the echo signal. A blood flow velocity measuring means for measuring a blood flow velocity based on the echo signal; a reference biological signal measuring means for measuring a reference biological signal synchronized with a heartbeat; and a predetermined characteristic waveform appearing in the reference biological signal. Characteristic waveform detecting means, waveform dividing means for dividing the signal waveforms of the displacement of the blood vessel wall and the blood flow velocity based on the characteristic waveform into sample waveforms of heartbeat period, and a predetermined condition for the sample waveforms. Based on each of the displacement of the blood vessel wall and the blood flow velocity, a representative selecting unit that selects a plurality of representative sample waveforms from the plurality of sample waveforms,
For each of the displacement of the blood vessel wall and the blood flow velocity,
An ensemble averaging means for obtaining an average blood vessel wall displacement waveform and an average blood flow velocity waveform by ensemble averaging the plurality of representative sample waveforms, and an evaluation value calculation for calculating an evaluation value from the average blood vessel wall displacement waveform and the average blood flow velocity waveform And means.

According to the present invention, the displacement signal of the blood vessel wall and the blood flow velocity signal obtained based on the echo signal are used as the target biological signal, and their average waveforms are generated. Then, a predetermined evaluation value is calculated based on those average waveforms. Various evaluation values are conceivable, and one of them is wave intensity, which is a circulatory dynamic index.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an ultrasonic diagnostic apparatus according to an embodiment of the present invention will be described with reference to the drawings. The ultrasonic diagnostic apparatus has a function of calculating wave intensity as an evaluation value for evaluating the properties of blood vessels and the function of the heart.

Wave intensity was originally
It is proposed as an index for determining which of the action of the forward pulse wave traveling from the heart to the periphery and the action of the reflected pulse wave reflected from the periphery toward the heart is dominant. Specifically, the wave intensity I is I = ΔP · ΔU from the time change ΔP and ΔU between Δt, where P is the pressure of the local site in the artery and U is the blood flow velocity of the local site. ......... (1) is defined.

That is, the wave intensity is defined as the product of the change in the pressure P and the change in the blood flow velocity U in the constant time interval Δt. The wave intensity normalized by time, which does not depend on how to take Δt, is expressed by the following equation (2).

WI = (dP / dt) · (dU / dt) (2) As can be seen from the above equation (2), the wave intensity WI is the time derivative of the pressure P and the time of the blood flow velocity U. It is defined as the product of the derivatives.

The ultrasonic diagnostic apparatus automatically tracks, for example, the displacement of the carotid vessel wall by the ultrasonic echo tracking method, and the time change of the blood vessel diameter is measured by this. On the other hand, the time change of blood flow velocity is measured by the ultrasonic Doppler method.

It is conventionally known that there is a similar relationship between a blood vessel diameter change waveform and a blood pressure change waveform.
When the maximum and minimum blood vessel diameters measured by the tracking method are calibrated with the maximum and minimum blood pressures measured by a cuff-type sphygmomanometer attached to the subject's upper arm, changes in blood vessel diameters are regarded as changes in blood pressure at the local site. be able to.

Then, the wave intensity is calculated from the above change in blood flow velocity and change in blood pressure according to the above equation (2).

FIG. 1 is a schematic block diagram of the ultrasonic diagnostic apparatus. In FIG. 1, a probe 10 is an ultrasonic probe that transmits ultrasonic pulses and receives echoes. This probe 10 has an array transducer, and the ultrasonic beam is electronically scanned by electronic scanning of the array transducer. Examples of the electronic scanning method include electronic linear scanning and electronic sector scanning. The ultrasonic diagnostic apparatus according to the present embodiment has the function of measuring the wave intensity, as described above, in measuring the wave intensity,
The living body surface 1 of the probe 10 so that the scanning plane formed by the scanning of the ultrasonic beam coincides with the central axis of the blood vessel 14.
The contact position and contact position with respect to 2 are adjusted by manual operation.

The transmission circuit 16 is a circuit for supplying a transmission signal to the probe 10, and the operation of the transmission circuit 16 is controlled by the transmission / reception control section 18. Receiver circuit 20
Is a circuit that performs processing such as amplification and phasing addition on the received signal from the probe 10. The reception circuit 20 is also controlled by the transmission / reception control unit 18.

The transmission / reception control unit 18 executes transmission / reception control for forming a transmission beam and a reception beam.

The tomographic image forming section 22 is a circuit for forming a tomographic image, that is, a B-mode image. The image information of the formed tomographic image is output to the display processing unit 24. The displacement calculator 26 determines the position of the blood vessel wall, specifically, the probe 10.
The position of the front wall on the front side as viewed from the position and the position of the rear wall on the back side as viewed from the probe 10 are calculated, and the blood vessel diameter is calculated from the positions of the front wall and the rear wall. Have

Specifically, the displacement calculator 26 has a function of tracking the position of the blood vessel wall in the tracking gate set by the user on the measurement line described later.

The blood flow velocity calculation unit 28 obtains the blood flow velocity from the echo signal on the measurement line by the color Doppler method,
It is a circuit that calculates the average value of the blood flow velocity in the sample gate set on the measurement line. Blood vessel diameter change signal 102 calculated by the displacement calculator 26 and blood flow velocity calculator 28
The blood flow velocity signal 104 representing the blood flow velocity calculated in (4) is output to the display processing unit 24 and the ensemble average calculation unit 34.

Incidentally, the measurement line setting device 30 is a device for setting a measurement line shown later, and the tracking gate setting device 32 is a device for manually setting the tracking gate, which are, for example, a keyboard or a track. It is composed of a pointing device such as a ball.

The electrocardiographic measurement unit 42 is provided for measuring the electrocardiographic signal 10 of the subject.
7 is measured and output to the ensemble average calculation unit 34.

The ensemble averaging unit 34 includes a blood vessel diameter change signal 102, a blood flow velocity signal 104, and an electrocardiographic signal 10.
7 is divided into sample waveforms of each heartbeat period, and the sample waveforms are ensemble averaged to generate a change average waveform of blood vessel diameter, a blood flow velocity average waveform, and an electrocardiographic average waveform.
This will be described in more detail later with reference to FIG.

The evaluation value calculator 36 is a circuit for calculating the wave intensity as an evaluation value from the blood vessel diameter and the blood flow velocity. FIG. 3 described later shows a specific configuration example thereof. The value of the wave intensity calculated by the evaluation value calculation unit 36 is output to the display processing unit 24.

In the present embodiment, the evaluation value calculation unit 36
Sphygmomanometer 4 to calculate wave intensity
The blood pressure signal 106 output from 0, specifically, the maximum blood pressure and the minimum blood pressure are referred to. For example, the sphygmomanometer 40 measures the blood pressure of the subject with a cuff wrapped around the upper arm surface of the subject.

The display processing section 24 is a circuit that forms a display image displayed on the display 38. The display processing unit 24 has an image synthesizing function and the like.

It is desirable that the blood flow velocity calculation unit 28 be composed of a quadrature detector, an autocorrelator, etc. mounted on the conventional ultrasonic Doppler diagnostic apparatus.

FIG. 2 shows a concrete configuration example of the ensemble average calculation unit 34 shown in FIG. The electrocardiographic signal 107 is input to the R wave detector 50, and the R wave detector 50
Detects the R wave appearing in the electrocardiographic signal at the start timing of the ventricular systole, and outputs the trigger signal at that timing. R
The waves form exceptionally high and sharp peaks in the electrocardiographic signal and can be detected by peak detection techniques.

The heartbeat divider 52 outputs the change signal 1 of the blood vessel diameter.
02, the blood flow velocity signal 104, the electrocardiographic signal 107, and the trigger signal from the R wave detector 50 are input. Heartbeat divider 5
2 is a change signal 10 of the blood vessel diameter at the timing of the trigger signal.
2. Separate the blood flow velocity signal 104 and the electrocardiographic signal 107. As a result, the blood vessel diameter change signal 102, the blood flow velocity signal 104, and the electrocardiographic signal 107 are each divided into sample waveforms for each heartbeat period from the R wave to the next R wave. The heartbeat divider 52 gives an index to each heartbeat period, and this index is used to identify the data of the sample waveform of each signal. Blood vessel diameter change signal 102, blood flow velocity signal 10
4 and the sample waveforms 112, 114, and 116 generated from the electrocardiographic signal 107, respectively, are output to the ensemble average calculator 54. The sample waveform 112 generated from the blood vessel diameter change signal 102 is the heartbeat waveform correlation calculator 56.
Is also output to.

The heartbeat waveform correlation calculator 56 is sequentially input with the sample waveforms 112 of the blood vessel diameter change signal 102. For example, a plurality of sample waveforms input within a certain period are included in the set. A correlation value is calculated for each combination of two sample waveforms. This correlation calculation is performed using a well-known method for examining the degree of similarity between waveforms.

The representative selector 58 is a heartbeat waveform correlation calculator 5.
Based on the correlation value for each combination of the sample waveforms obtained in 6, a predetermined number of sample waveforms having strong correlation with each other are selected.

The ensemble average calculator 54 selects a representative of the sampled waveforms 112, 114 and 116 of the blood vessel diameter change signal 102, the blood flow velocity signal 104 and the electrocardiographic signal 107, which are sequentially input from the heartbeat divider 52. Bowl 58
A sample waveform having the same heartbeat period as the sample waveform selected in is selected as the representative sample waveform. This selection is made based on the index mentioned above. The ensemble average calculator 54 is
The representative sample waveforms of the blood vessel diameter change signal 102, the blood flow velocity signal 104, and the electrocardiographic signal 107 are individually ensemble averaged. From the ensemble average calculator 54, a change average signal of blood vessel diameter, a blood flow velocity average signal, and an electrocardiographic average signal having an average waveform obtained by the ensemble average are output. It should be noted that each of these average signals is used by the evaluation value calculator 36 and can be displayed on the display 38.

FIG. 3 shows the evaluation value calculator 36 shown in FIG.
Is shown. The blood flow velocity average signal 124 output from the ensemble average calculation unit 34 is input to the differentiator 70, and the differentiator 70 calculates the time derivative of the blood flow velocity. The differentiation result is output to the multiplier 72.

On the other hand, in the scaling unit 74, the blood vessel diameter change average signal 122 output from the ensemble average calculating unit 34 and the blood pressure signal 106 output from the sphygmomanometer 40.
Is entered. The scaling unit 74 determines the maximum value and the minimum value of the blood vessel diameter change average signal 122, respectively.
By correlating the maximum blood pressure and the minimum blood pressure obtained from No. 6, the waveform of the change average signal 122 of the blood vessel diameter is calibrated as the blood pressure waveform. That is, unit conversion is executed. Therefore,
The converted blood pressure signal is output from the scaling unit 74. The differentiator 76 performs time differentiation on the blood pressure signal, and the differentiation result is output to the multiplier 72.

The multiplier 72 has a differentiator 70 and a differentiator 76.
This is a circuit for obtaining the wave intensity as an evaluation value by multiplying the differential result of the blood flow velocity and the differential result of the blood pressure output from. That is, the configuration shown in FIG. 3 is a circuit that executes the above equation (2).

Next, the processing procedure in the ensemble average calculation unit 34 will be described with reference to the processing flow chart of the ensemble average shown in FIG. First, the length of the sampling period for sampling the sample waveform and the heart rate to be ensemble averaged, that is, the number m of sample waveforms selected as the representative sample waveform by the representative selector 58 are set (S20).
0). The ensemble average calculation unit 34 is configured such that the displacement calculation unit 26 and the blood flow velocity calculation unit 28 within the set sampling period.
And a blood vessel diameter change signal 102, a blood flow velocity signal 104, and an electrocardiographic signal 107, which are respectively input from the electrocardiographic measurement unit 42.
Is stored (S205). These signals can be stored in memory as digital data.

The R wave detector 50 stores the stored electrocardiographic signal 10
The data of No. 7 is read and the timing of the R wave is detected (S210). The heartbeat divider 52 uses the blood vessel diameter change signal 1
02, the blood flow velocity signal 104 and the electrocardiographic signal 107 are read out. The signal data sequence is divided at the timing of the R wave detected by the R wave detector 50 to generate a signal data sequence in heartbeat cycle units. The signal data string for one heartbeat defines each sample waveform. The heartbeat divider 52 associates the sample waveform of each signal with a number according to the time series order as an index. Here, it is assumed that the indices 0 to n are given in order from the sample waveform located at the beginning of the sampling period to the last sample waveform (S215).

Of the sampled waveforms of each signal generated by the heartbeat divider 52, the sampled waveform of the blood vessel diameter change signal 102 is passed to the heartbeat waveform correlation calculator 56 together with the index. In the heartbeat waveform correlation calculator 56, the correlation value S _{i, k} between the two sample waveforms (i-th and k-th sample waveforms) of the blood vessel diameter change signal 102 is calculated for all combinations of i and k. . This process is started with initial values of i and k set to 0 (S220). And i
By fixing the, some i, the correlation values S _i for _{k, k} is calculated and stored in storage means such as a memory (S225).
Note that here, when i and k are equal, the calculation and recording of the correlation value are not performed.

Every time the processing S225 for a certain i, k is completed, k is incremented by 1 (S23).
0). When the heartbeat waveform correlation calculator 56 completes the calculation and recording of the correlation value for k = n for a certain i (S235), the representative selector 58 determines the n correlation values S _{i, k} (k = 0 to n), the upper m with the largest value
The average value mean (S _i ) is calculated, and the average value and the index of the averaged sample waveform are stored (S240). On the other hand, when the processing is completed up to k = n, the heartbeat waveform correlation calculator 56 increments i by 1 (S245) and repeats processing S225 to S235. When the processing is completed up to i = n (S250), the representative selector 58 searches for the maximum value of stored mean (S _i ) and defines a group of sample waveforms that gives the maximum value as the representative sample waveform, The index of the group of sample waveforms is read from the memory and output to the ensemble average calculator 54 (S255).

The ensemble average calculator 54 has a blood vessel diameter change signal 102, a blood flow velocity signal 104, and an electrocardiographic signal 10.
The sample waveform corresponding to the index selected by the representative selector 58 is selected from the series of sample waveform data strings generated by the heartbeat divider 52 for No. 7, and the ensemble average is output (S260). .

The ensemble averaging unit 34 can obtain a signal waveform from which respiratory fluctuation components and random noise are removed from various signals synchronized with the heartbeat. Although the signal waveform was used for calculating the wave intensity in the present apparatus, it can be used for measuring other evaluation values, etc., and the accuracy of the measured value can be improved.

Further, here, the heartbeat waveform correlation calculator 56
Has shown an example of calculating the correlation with respect to the sample waveform of the blood vessel diameter change signal, but the correlation may be calculated using, for example, the sample waveform of the blood flow velocity signal.

[0048]

According to the biological signal measuring apparatus and the ultrasonic diagnostic apparatus of the present invention, the heartbeat period suitable for the ensemble average is selected from the biological signal, and the ensemble average waveform is generated. As a result, the ensemble averaging process for the biomedical signal synchronized with the heartbeat is automated to save labor, and the ensemble averaging is performed on the sample waveform selected based on the objective criteria such as the correlation value in heartbeat period units. Therefore, a highly accurate average waveform can be obtained. In particular, when the wave intensity is obtained, the blood pressure signal and the blood flow velocity signal obtained from the change signal of the blood vessel diameter as the biomedical signal are differentiated, but by using the ensemble average waveform, the peak position can be determined. Improved accuracy,
The measurement accuracy of wave intensity is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of an ensemble average calculation unit.

FIG. 3 is a block diagram showing a specific configuration example of an evaluation value calculation unit.

FIG. 4 is a processing flow chart of ensemble averaging.

[Explanation of symbols]

10 probe, 16 transmission circuit, 18 transmission / reception control unit, 20 reception circuit, 22 tomographic image forming unit, 24 display processing unit, 26 displacement calculation unit, 28 blood flow velocity calculation unit,
30 measurement line setting device, 32 tracking gate setting device, 34 ensemble average calculating unit, 36 evaluation value calculating unit, 38 indicator, 40 sphygmomanometer, 42 electrocardiographic measuring unit,
50 R wave detector, 52 Heartbeat divider, 54 Ensemble average calculator, 56 Heartbeat waveform correlation calculator, 58 Representative selector, 70, 76 Differentiator, 72 Multiplier, 74
Scaling section.

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Claims (5)

[Claims] 1. A reference biological signal measuring means for measuring a reference biological signal synchronized with a heartbeat, a characteristic waveform detecting means for detecting a predetermined characteristic waveform appearing in the reference biological signal, and a purpose for measuring a target biological signal from a living body. Biological signal measuring means, a waveform dividing means for dividing the target biological signal waveform into a sample waveform of a heartbeat period based on the characteristic waveform, based on a predetermined condition for the sample waveform, a plurality of the plurality of sample waveforms A biological signal measuring device comprising: a representative selecting unit that selects a representative sample waveform; and an ensemble averaging unit that averages the plurality of representative sample waveforms by an ensemble to obtain an average waveform of a target biological signal. 2. The biological signal measuring apparatus according to claim 1, further comprising a correlation value calculating unit that calculates a correlation value between the sample waveforms, and the representative selecting unit is similar to each other based on the correlation value. A group of the sample waveforms are selected as the representative sample waveforms. 3. The biological signal measuring device according to claim 1 or 2, wherein the reference signal is an electrocardiographic signal. 4. The biological signal measuring device according to claim 3, wherein the characteristic waveform is an R wave of the electrocardiographic signal. 5. A transmitting / receiving means for transmitting an ultrasonic pulse and receiving an echo signal, a blood vessel wall displacement measuring means for measuring a displacement of a blood vessel wall based on the echo signal, and based on the echo signal. A blood flow velocity measuring means for measuring a blood flow velocity, a reference biological signal measuring means for measuring a reference biological signal synchronized with a heartbeat, a characteristic waveform detecting means for detecting a predetermined characteristic waveform appearing in the reference biological signal, Waveform dividing means for dividing the signal waveforms of the blood vessel wall displacement and the blood flow velocity based on a characteristic waveform into a sample waveform of a heartbeat cycle unit, and a displacement of the blood vessel wall based on a predetermined condition for the sample waveform, Representative selection means for selecting a plurality of representative sample waveforms from the plurality of sample waveforms for each of the blood flow velocities; displacement of the blood vessel wall and the blood flow velocity, respectively. For,
An ensemble averaging means for obtaining an average blood vessel wall displacement waveform and an average blood flow velocity waveform by ensemble averaging the plurality of representative sample waveforms, and an evaluation value calculation for calculating an evaluation value from the average blood vessel wall displacement waveform and the average blood flow velocity waveform. An ultrasonic diagnostic apparatus comprising: