JPH09224938A - Ultrasonic diagnostic device and method for optimizing delay time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the quality of an ultrasonic tomogram through the effect of dynamic focusing method. SOLUTION: This ultrasonic diagnostic device has an oscillator 60, a pulser 61, a transmission delay circuit 62, a transmission rate signal generator 63, and a delay time control circuit 64, which scan ultrasonic signals for each scanning line on a cross section within an examinee, and an oscillator 60, a preamplifier 65, a reception delay circuit 66, and an adder 70, which produce focused input signals by imparting a delay time to a plurality of ultrasonic echo signals obtained as scans are provided. The device also includes an A/D converter 82, a buffer memory 83, and a correlation processing circuit 84, which calculate an amount showing the correlation among the input signals for each parameter, based on the input signals on a plurality of scanning lines, the signals being obtained at each of in vivo speed sound values that dominate the degree of focusing of the input signals, and an optimum sound speed value detecting circuit 85 and a delay time control circuit 64 which optimize the delay time imparted to the echo signals according to the in-vivo sound speed value at which the amount of correlation for each of the in-vivo sound speed values is at a minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called ultrasonic diagnostic apparatus for displaying a tomographic image in a body using an ultrasonic signal and a delay time optimizing method for optimizing a delay time given to the ultrasonic signal. In particular, the present invention relates to an ultrasonic diagnostic apparatus and a delay time optimizing method that automatically correct the ultrasonic beam pattern deterioration caused by the uncertainty of the sound velocity value in the living body to improve the resolution.

[0002]

2. Description of the Related Art An ultrasonic diagnostic method in which an ultrasonic signal (also referred to as an ultrasonic beam or an ultrasonic pulse) is radiated into the body of a subject, and biological information is obtained by reflected waves from each tissue in the subject, Rapid progress has been made in recent years by the development of two technologies, ultrasonic tomography and ultrasonic Doppler. The most popular electronic scanning device today uses an array-type ultrasonic transducer (ultrasonic transducer), which is electronically controlled at a high speed to perform real-time display. Made possible

A conventional example of a sector electronic scanning type ultrasonic diagnostic apparatus is shown in FIG. 19 using a block diagram. Let M be the number of transducer elements arranged in the ultrasonic probe (transducers 4 (1) to 4 (M)). When transmitting an ultrasonic pulse into a living body (or a medium), the transmission rate signal generator 1 first outputs a rate pulse that determines the repetition frequency of the ultrasonic pulse. This rate pulse is transmitted by the delay circuit 2 for transmission composed of M channels.
(1) to 2 (M), a delay time τ _f that determines the convergence distance (F ₀ ) of the ultrasonic beam at the time of transmission, and a delay for deflecting the ultrasonic beam in a predetermined direction (θ ₀ ). Time τ _s
Are supplied to the M-channel oscillator drive circuits (pulsars) 3 (1) to 3 (M).

That is, the delay time τ (m) set in the m-th delay circuit 2 (m) is τ _f (m) + τ _s
(M), and τ _f and τ _s are set as follows (see FIG. 3 for τ _f (m)).

[0005]

[Equation 1] Here, d is the transducer array interval, V is the in-vivo sound velocity, and F ₀
Is the focal length, and θ ₀ is the deflection angle (sector angle). In addition,
See FIG. 20 for τ _f (m).

In the pulsers 3 (1) to 3 (M), drive pulses for driving the ultrasonic transducers 4 (1) to 4 (M) to generate ultrasonic waves are generated. The transmission timing is determined by the outputs of the transmission delay circuits 2 (1) to 2 (M). This pulsar (driving circuit) 3
The outputs of (1) to 3 (M) are ultrasonic transducers 4 (1) to 4 (4).
(M) is supplied to the ultrasonic transducers 4 (1) to 4 (4).
(M) is driven to generate ultrasonic waves.

A part of the ultrasonic waves generated from the ultrasonic transducers 4 (1) to 4 (M) and radiated into the living body is reflected by the boundary surface of the organ in the living body or the acoustic scatterer of the living tissue. Is
It is again received by the ultrasonic transducers 4 (1) to 4 (M) and converted into electric signals. This received signal is amplified through the preamplifiers 5 (1) to 5 (M), and then the delay time that determines the convergence distance of the ultrasonic beam at the time of reception and the deflection angle of the ultrasonic beam are determined as in the case of transmission. Delay time for receiving and delay circuit for receiving M channel 6 (1)
It is sent to the adder 7 through ~ 6 (M). The output signal of the M-channel reception delay circuit 6 is added and synthesized by the adder 7. The output signal of the adder 7 is logarithmically compressed and detected by the logarithmic amplifier 8 and the envelope detection circuit 9 to obtain A /
After being A / D converted by the D converter 10, it is temporarily stored in the image memory 11 by a write / read controller (not shown).

The signal stored in the image memory 11 is read out in the television format by the writing / reading controller and sent to the television monitor 13, and the monitor 13
Is displayed as an ultrasonic tomographic image.

On the other hand, the output of the adder 7 is sent to two quadrature phase detection circuits. That is, the output of the adder 7 is first sent to the mixer circuits 14-1 and 14-2. Further, the reference signal generator 20 outputs a continuous wave (reference signal) having a predetermined frequency (generally, a frequency substantially equal to the ultrasonic frequency f0 is used). The output of the reference signal generator 20 is branched, one of which is phase-shifted by 90 degrees in the phase shifter 15 and input to the mixer circuit 14-1, and the other is directly input to the mixer circuit 14-2. It The outputs of the mixer circuits 14-1 and 14-2 are sent to the low-pass filters 16-1 and 16-2, and the low-pass filters 16-1 and 16-2 remove the frequency components of the sum and only the frequency components of the difference. Is extracted. The signal having this difference frequency is converted into a digital signal by the A / D converters 17-1 and 17-2 and then temporarily stored in the memory circuit.

On the other hand, in order to calculate the Doppler signal,
It is necessary to continuously scan the same site and use a plurality of signals at that time. A plurality of signals obtained by the plurality of scans are temporarily stored in a memory (not shown), and when a predetermined number of data are gathered, the FFT circuit 18 analyzes the frequency of the Doppler signal to obtain the Doppler frequency ( Flow velocity) is required. The flow velocity obtained by the FFT circuit 18 is calculated by the calculator 1
9

The physical quantities displayed in the ultrasonic blood flow imaging method (ultrasonic Doppler method) are the center of the spectrum (that is, the average value of the flow velocity) and the dispersion value of the spectrum (that is, the state of disturbance of the flow velocity). These calculations are carried out by the calculator 19. The value calculated by the calculator 19 is
It is temporarily stored in the image memory 11 and displayed on the television monitor 13. Here, the output of the arithmetic unit 19 is generally displayed in color on the tomographic image.

As described above, the conventional ultrasonic diagnostic apparatus employs a method of focusing an ultrasonic beam in at least one of transmission and reception in order to improve lateral resolution. In particular, an electronic scanning array transducer generally uses an electron focusing method by controlling a delay time of a transmission / reception signal. The ultrasonic diagnostic apparatus has a delay control circuit 21 as a control circuit for controlling the delay time. The delay control circuit 21 controls the delay time given to the transmission / reception signal as in the above-mentioned formula (1).

However, a problem of the electron focusing method for focusing the ultrasonic beam is that the beam spreads at a place (depth) away from the focusing point and the resolution is lowered. As a method for solving this problem, a dynamic focusing method has been conventionally used. The dynamic focus method is a method of performing delay time control so that the focus point continuously moves in the depth direction with time during reception, and the reflected signal is always obtained from the area where the received ultrasonic beam is focused. .
The principle will be described with reference to FIG.

In the range where the reflection signal from the oscillator to the distance 0 to r1 can be obtained (that is, from time 0 to 2r1 /
The reception delay time is set so that the focal length is f1 (range up to V). Next, in the range where the reflection signal from the transducer is r1 to r2 is obtained (that is, from the time 2r1 / V to 2r2 / V), the focal length is f
The reception delay time is set to be 2. Further, when the reflected signal is obtained from the range where the distance from the oscillator is r2 or more (that is, the range where the time is 2r2 / V or more), the reception delay time is set so that the focal length becomes f3. However, 0≤f1≤r1, r1≤f2≤r2, r2≤f3
It is.

[0015]

In the above description of the dynamic focusing method, the case where the focusing point at the time of the dynamic focusing changes in three steps of f1 to f3 has been described.
In recent devices, continuous focusing points can be set for each pixel of the image memory due to the influence of digitalization of the reception delay circuit.

When the focal point is continuously set by using the dynamic focusing method, the reception delay time is set by using the equation (1), and the delay shown by the equation (1) is set. It has been conventionally known that the in-vivo sound velocity value V among the time-determining parameters differs depending on the organ. For example, “V = 1560 m / sec” for muscle and “V = 1480 m / sec for fat”.
sec ”is also reported, and there are considerable differences among subjects.

As described above, since the in-vivo sound velocity value is actually an amount that cannot be universally determined, the focusing point cannot be determined, which is an obstacle to the dynamic focusing method. .

That is, given delay time τ _f (m)
On the other hand, F ₀ V = constant at all times, so if there is a difference of about 5% in the speed of sound like the above fat / muscle, the focus point 10
The movement of the focusing point at 0 mm is 5 mm, which is a non-negligible amount. Therefore, in such a case, it cannot be said that the reception from the focusing point is always captured and displayed, and as a result, the image quality is deteriorated.

Further, when the set sound velocity value of the device is equal to the actual sound velocity value, as shown in FIG. 22 (B), the range (0) to r1 (distance from the transducer) where the reflection signal can be obtained. That is, in the range from time 0 to 2r1 / V), the actual focal length f1 'is determined to be approximately the midpoint of 0-r1. Similarly, in the range where the reflected signals with the distances r1 to r2 are obtained (that is, from the time 2r1 / V to 2r).
(Range up to 2 / V), the actual focal length f2 'is r1-r2
When the reflected signal is obtained at the approximate midpoint of the distance r2 or more in the range of distance r2 or more (that is, in the range of time 2r2 / V or more), the actual focal length f3 'is determined to be r3 or later.

On the other hand, for example, when the actual in-vivo sound velocity value is larger than the set sound velocity value in the apparatus, FIG.
As shown in (A), the actual focus points f1 'to f3' are set focus points f1 to f3 (generally f1 = r1 / 2, f2 = (r1
+ R2) / 2, f3> r3), f1 '<f1, f2'
<F2, f3 '<f3, and especially when the difference between the sound velocity values is large, a case of f2'<r1 occurs, and the effect of the dynamic focusing method cannot be utilized.

The present invention has been made to solve the above-mentioned problems, and its purpose is to make the maximum effect of the dynamic focusing method by constantly matching the set focusing point and the actual focusing point. Its purpose is to further improve the image quality of an ultrasonic tomographic image.

[0022]

In order to solve the above-mentioned problems, according to the present invention, for example, in a received signal on adjacent scanning lines, for example, in a region (arbitrary depth) designated on a tomographic image. The amount (correlation amount) indicating the correlation between the signals is calculated. Then, the degree of focusing of the received signal (the depth position of the receiving focus, etc.) is controlled based on the calculated correlation amount.

That is, while the parameter values, such as the in-vivo sound velocity value, which govern the degree of focusing of the received signal are sequentially changed, the correlation amounts calculated each time are compared. And
A parameter value (optimum value) that minimizes the amount of correlation is searched for, and a parameter that determines the focusing degree based on the parameter value (for example, delay time or the degree of change in the depth position of the receiving focus) is configured to be optimized. Has been done.

With this configuration, a parameter value (in-vivo sound velocity) that minimizes the amount of correlation between received signals on adjacent scanning lines, for example, at fixed intervals for each diagnostic region, for each subject, etc. Since the focusing parameters (delay time, degree of change of depth position of reception focus, etc.) can be set based on the value), the degree of reception focus of ultrasonic beam (depth position, etc.) It is always constant regardless of changes. Therefore, for example, even in high-definition reception dynamic focus performed on a pixel-by-pixel basis, only the reception signals from the focal points are always collected, and an ultrasonic tomographic image with higher resolution and higher image quality is obtained based on those reception signals. be able to.

In the present invention, the ultrasonic signal is repeatedly scanned on the same scanning line a plurality of times, and the repeated scanning is performed based on the received signals on the plurality of scanning lines obtained at each of the plurality of repeated scanning. The correlation amount for each is calculated. And
An accurate correlation amount with a small error can be obtained by averaging the calculated correlation amounts for each repeated scan.

Further, according to the present invention, the correlation amount for each different portion is calculated based on the received signal on the scanning line of the different portion on the cross section, and the calculated correlation amount for each repeated scanning is added and averaged. It is possible to obtain an accurate correlation amount with a small error.

On the other hand, in order to solve the above problems,
In the present invention, for example, in the case of scanning by deflecting an ultrasonic signal such as sector scanning, among received signals on adjacent scanning lines, for example, between signals in a region (arbitrary depth) designated on a tomographic image. An amount indicating the correlation (correlation amount) is calculated. Then, the deflection angle of the ultrasonic signal is controlled based on the calculated correlation amount.

That is, while the parameter values that control the deflection angle of the ultrasonic signal, such as the in-vivo sound velocity value, are sequentially changed, the correlation amounts calculated each time are compared. And
A parameter value (optimum value) that minimizes the correlation amount is searched, and a parameter that determines the deflection angle (for example, delay time) based on the parameter value or a parameter that determines the reception focus depth position (the degree of change of the depth position). Etc.).

With this configuration, for example, when performing a sector scan, the correlation amount between the received signals on the adjacent scanning lines is minimized at fixed intervals, for example, depending on the diagnosis region or the subject. Since the parameters (delay time, degree of change of depth position, etc.) can be set based on the parameter value (in-vivo sound velocity value), the deflection angle of the ultrasonic beam is related to changes in in-vivo sound velocity value. Instead, it is always constant, and the receiving focus depth position can be optimized.
Therefore, a high resolution and high quality ultrasonic tomographic image can be obtained.

Further, as the deflection angle control means, it is possible to control the writing of the ultrasonic scanning signal into the memory for scanning conversion. That is, the deflection angle data corresponding to the parameter value with which the correlation amount is minimized is obtained, and the writing address of the received signal to the memory is changed according to the deflection angle data, whereby the in-vivo sound velocity is changed. It is possible to correct an error in the deflection angle due to the change in the value.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the common concept of the present invention is shown in FIG.
This will be described with reference to FIGS. 1 and 2 are schematic diagrams (partial cross-sectional views) showing an ultrasonic wave transmission / reception portion of an ultrasonic diagnostic apparatus that performs sector electronic scanning, and includes a transmitter 50, a receiver 51, a display 52, and a delay circuit. 53 ... 53, vibrator 5
54, and a delay time control circuit 55 are shown.

Now, in an ultrasonic diagnostic apparatus for performing sector electronic scanning, its ultrasonic beam transmission / reception direction (scanning direction,
Of the received signals (e1 (t) and e2 (t), respectively) obtained in substantially adjacent scans of θ and θ + Δθ, the beam width near the “A” focusing point is wide ( Focusing is not done as planned; Figure 1 (A)
And (B)), and “B”, the relationship between the beam width and the correlation function is described for the case where the beam width is narrow (when focusing is performed more accurately; see FIGS. 2A and 2B). .

Generally, the interval between adjacent scanning lines (scan interval; here Δθ) is set small with respect to the ultrasonic beam width. Therefore, two adjacent ultrasonic beams Ba
, Bb have some regions in common as shown in FIG. 1, and this common region is larger as the focusing is insufficient and the beam width is wider. That is, the wider the beam width (the wider the beam divergence state, the greater the divergence of the beam side rope level), the more common the information from the same scatterer is contained in the received signal obtained by each scanning. Therefore, the correlation strength between each received signal (correlation coefficient)
Will be larger.

On the other hand, as the focusing is performed more completely, the common portion of the adjacent ultrasonic beams Ba 'and Bb' becomes narrower as shown in FIG. 2 and obtained by each scanning. The correlation coefficient between each signal becomes small. That is, the beam width and the correlation strength C (0) are qualitatively as shown in FIG.

The received signal e1 (t) in the θ direction and θ + Δθ
The correlation coefficient C (0) of the received signal e2 (t) from the direction (the waveforms of both are shown in FIGS. 4 (a) and 4 (b)) is expressed by the following equation (see FIG. 4 (c)).

[0036]

[Equation 2] Here, e2 (t) ^* is a complex conjugate function of e2 (t).

That is, it can be seen that the beam width near the focus point can be controlled by controlling the correlation coefficient C (0) of two or more adjacent ultrasonic beams.

According to the present invention, by utilizing the above-mentioned property, the delay time for obtaining each focus point in dynamic focus is controlled so that the beam width of the focus point is minimized, and the error of the focus point described above is controlled. Is configured to reduce

Next, FIG. 5 shows a first embodiment for briefly explaining the outline of the processing procedure of the autofocus method based on the correlation processing.

This ultrasonic diagnostic apparatus is, for example, a diagnostic apparatus that performs sector scanning, and is an array type ultrasonic transducer 60 (1) -60 (which is an electro-acoustic transducer in which M transducers are linearly arranged. M). The array type vibrator 60 has a transmission system for driving the vibrators 60 (1) to 60 (M) to radiate an ultrasonic signal into, for example, a living body, and each vibration reflected from the living body. Child 60 (1) ~
The receiving system for processing the echo signal received by 60 (M) is respectively connected.

The transmission system is composed of array type transducers 60 (1) to 6 (6).
M for outputting drive pulse for driving 0 (M) respectively
Channel pulser (vibrator drive circuit) 61 (1) -6
1 (M) and transmission pulse delay circuits 62 (1) to 61 (1) to 61 (M), which delay control the drive pulse output timing of the pulsers 61 (1) to 61 (M).
62 (M) and each transmission delay circuit 62 (1) to 62 (M)
A transmission rate signal generator 63 for sending a rate pulse for delay control and a delay time control circuit 64 for individually controlling the delay time given by each of the transmission delay circuits 62 (1) to 62 (M).

The transmission delay circuits 62 (1) to 62 (M) are
With respect to the rate pulse sent from the transmission rate signal generator 63, a delay time τ which determines the focusing distance (F0) of the ultrasonic beam at the time of transmission controlled by the delay time control circuit 64.
_f and a delay time τ _s for deflecting the ultrasonic beam in a predetermined direction (θ ₀ ) are given to each of the pulsers 61 (1) to 61 (61).
(M) and outputs the pulser 61 (1) to 61 (M).
Are individually driven according to the sent rate pulse to drive the respective transducers 60 (1) to 60 (M).

That is, the m-th (m <M) th delay circuit 6
The delay time τ (m) set in 2 (m) is τ _f
(M) + τ _s (m), and τ _f (m) and τ _s (m)
Is set as follows (for τ _f (m), see FIG.
reference).

[0044]

(Equation 3) Here, d is the transducer array interval, V is the in-vivo sound velocity, and F ₀
Is the focal length, and θ ₀ is the deflection angle (sector angle).

The receiving system is composed of array type transducers 60 (1) to 6 (6).
Preamplifiers 65 (1) to 65 (M) for amplifying received signals received by 0 (M) and converted into electric signals
And a reception delay circuit 66 for receiving M channels that performs reception processing while giving different delay times to the reception signals amplified by the preamplifiers 65 (1) to 65 (M).
(1) to 66 (M) and the reception delay circuits 66 (1) to 6
A delay time control circuit 64 for individually controlling the delay time given by 6 (M).

The reception delay circuits 66 (1) to 66 (M) are
According to the control of the delay time control circuit 64, the delay time τ _f that determines the focusing distance of the ultrasonic beam at the time of reception similarly to the time of transmission
And a delay time τ _s that determines the deflection angle of the ultrasonic beam are given to the received signal. At this time, the delay time control circuit 64 uses different depths (focal lengths F ₀ , F ₁ ,
It is also possible to change the delay time τ _f (reception dynamic focus) so that a reception signal that is substantially continuously focused according to F ₂ , F ₃ , ...

Further, the reception system includes a reception delay circuit 66 (1).
To 66 (M), the adder 70 adds and combines the received signals, and the logarithmic amplifier 71 that logarithmically amplifies (compresses) the received signals added and combined by the adder 70.
A detection circuit 72 for generating a detection signal (A mode signal) by envelope detection of the logarithmically compressed reception signal; an A / D converter 73 for converting the detection signal into a digital signal;
An image memory 74 for storing the digital image signal A / D converted by the A / D converter 73, a write / read controller 75 for controlling writing / reading of the digital image signal to / from the image memory 64, and an image memory A D / A converter 76 for converting the digital image signal read out from the analog image signal 74 into an analog image signal;
The television monitor 77 displays the analog image signal converted by the converter 76 as an ultrasonic tomographic image.

On the other hand, the ultrasonic diagnostic apparatus is provided with a unit for controlling at least one of the transmission delay time and the reception delay time according to the correlation strength between adjacent reception signals. That is, this delay time control unit includes the delay time control circuit 64 described above, a gate circuit 80 connected to the branch output side of the adder 70 and sampling a part of the received signal, and a sampling area of the gate circuit 80. A designator 81 having a trackball or a joystick that can be designated on the monitor 77 and installed on the panel of the diagnostic device or the like.
Of the A / D converter 82 connected to the output side of the gate circuit 80, the buffer memories 83 and 83 connected to the branch outputs from the A / D converter 82, and the buffer memories 83 and 83, respectively. It has a correlation processing circuit 84 connected to the reading side and an optimum sound velocity value detection circuit 85 connected to the output side of the correlation processing circuit 84. The correlation processing circuit 84 includes a calculation circuit that calculates the correlation coefficient by performing a correlation calculation on the signals output from the buffer memories 83 and 83, and a memory that stores the correlation coefficient calculated by this calculation circuit. The optimum sound velocity value detection circuit 85 is adapted to obtain the minimum correlation coefficient from a plurality of correlation coefficients stored in the memory of the correlation processing circuit 84 and the set sound velocity value corresponding to the correlation coefficient. The output side of the optimum sound velocity value detection circuit 85 is connected to the delay time control circuit 64.

Next, the overall operation of the ultrasonic diagnostic apparatus according to the present embodiment will be described, particularly focusing on the autofocus processing operation by delay time control according to the correlation strength between adjacent received signals.

When transmitting the ultrasonic pulse into the living body, the rate pulse output from the transmission rate signal generator 63 is sent to the transmission delay circuits 62 (1) to 62 (M). Then, the rate pulse is transmitted by the transmission delay circuit 62.
In (1) to 62 (M), the delay time τ _f calculated and determined by the delay time control circuit 64 based on the sound velocity value V _x1 (for example, 1530 m / sec) as a preset provisional value.
And a delay time τ _s are supplied to the M-channel oscillator drive circuits (pulsers) 61 (1) to 61 (M).

Each of the pulsers 61 (1) to 61 (M) sends a drive pulse to each ultrasonic transducer 60 (1) at a transmission timing determined according to the output of the transmission delay circuits 62 (1) to 62 (M). ) To 60 (M), and as a result, each of the ultrasonic transducers 60 (1) to 60 (M) is driven to emit an ultrasonic beam into the living body.

A part of the ultrasonic beam radiated in the living body is reflected by the boundary surface of the organ in the living body or the acoustic scatterer of the living tissue, and the ultrasonic transducers 60 (1) -60 are again provided.
It is received by (M) and converted into an electrical signal. This received signal, after being amplified through the preamplifiers 65 (1) to 65 (M), has the delay time τ _f and the delay time τ _s at the time of reception, which are determined based on the set sound velocity value VX1, as at the time of transmission. It is given by the reception delay circuits 66 (1) to 66 (M) and sent to the adder 70 (FIG. 6, step S1).

The output of the adder 70 is logarithmically compressed and detected by a logarithmic amplifier 71 and a detection circuit 72, and is output as a digital image signal by an A / D converter 73 as an image memory under the control of a write / read controller 75. Stored at 74. Then, it is read out in the television format by the writing / reading controller 75, sent to the monitor 77 via the D / A converter 76, and displayed as an ultrasonic tomographic image.

Then, on the ultrasonic tomographic image (see FIG. 7) obtained based on the provisional delay time Vx1, the depth to be measured and the region of interest (hereinafter referred to as the measurement region) are set. In this case, the measurement area can be set by the designator 81 such as a trackball or a joystick (step S2).

Of the output of the adder 70, a part of the echo signal from the above measurement area is extracted by the gate circuit 80.
In the present embodiment, as shown in FIG. 7, of the echo signals obtained in two adjacent scans (scanning direction (scanning angle) θ and θ + Δθ (Δθ is a scanning interval)) in the measurement region, for example, near the center. Of the depth and the region of interest) are extracted (sampled) by the gate circuit 80 and sent to the A / D converter 82. The scanning direction (scanning angle) means the deflection angle of the scanning line from the direction orthogonal to the array direction of the transducers 60 (see FIG. 7).

The received signal e1 (t) in the scanning direction θ and the received signal e2 (t) in the scanning direction θ + Δθ which are A / D converted by the A / D converter 82 are stored in the buffer memories 83 and 83, respectively ( Step S3).

Then, the received signals e1 (t) and e2 (t) stored in the buffer memories 83, 83 are respectively input to the arithmetic circuit of the correlation processing circuit 84, and the arithmetic circuit produces the above equation (2). Based on the calculation, the correlation coefficient C (0) is calculated (step S4). Set sound velocity value (provisional value) V _x1 related to this received signal and calculated correlation coefficient C1 (0)
Are temporarily stored in the memory of the correlation processing circuit 84 (step S5).

Next, the delay time control circuit 64 delays the new set sound velocity value V _x2 , which is increased (or decreased) by a predetermined amount with respect to the set sound velocity value V _x1 , based on the above equation (3). The time is calculated. Then, the delay time calculated similarly to the case of the first set sound velocity value V _x1 described above is given to the reception signal by each of the reception delay circuits 66 (1) to 66 (M) (step S6). The same processing (step S3 to step S5) as in the case of the set sound velocity value V _x1 is performed.

That is, the received signal e1 obtained by two adjacent scans (scanning direction (θ), (θ + Δθ)) of the echo signals from the substantially same area as the designated area.
(t) 'and e2 (t)' are stored in the buffer memories 83, 83 and then input to the arithmetic circuit of the correlation processing circuit 84 to calculate the correlation coefficient C2 (0). The set sound velocity value V _x2 related to the received signal and the calculated correlation coefficient C2 (0) are stored in the memory similarly to the first set sound velocity value V _x1 and the correlation coefficient C1 (0).

In this way, the set sound velocity values V _x1 , V _x2 , ..., V
_By sequentially changing _xn within a predetermined range and performing the above-described processing (steps S3 to S5), the correlation coefficient C1 (0 corresponding to the sound velocity values V _x1 , V _x2 , ..., V _xn is obtained. , C2 (0), ..., Cn (0) are calculated by the arithmetic circuit of the correlation processing circuit 84 and stored in the memory.

Then, by the optimum set sound velocity detection circuit 85, the correlation coefficients C1 (0), C2 (0), ...
The optimum set sound velocity value V _xs corresponding to the smallest correlation coefficient Cmin (0) among Cn (0) and its minimum correlation coefficient Cmin (0) is obtained (step S7; see FIG. 8).

The optimum focusing delay time τ _{fr is} set by the delay time control circuit 64 based on the obtained optimum set sound velocity value V _xs.
And the final optimum delay time τ (= τ _fr + τ _s )
Is set, and the optimum delay time is set by the reception delay circuit 66.
At (1) to 66M, a new received signal is given (step S8). As a result, it is possible to optimize the focusing delay time in the entire depth direction based on the optimum delay time, and to display the optimally received and focused ultrasound image without depending on the sound velocity value. You can

As described above, according to this embodiment,
Even if the speed of sound in the living body changes, it is possible to set the optimum sound speed value that minimizes the correlation coefficient of the received signal, and the focusing delay time of the received signal can be determined based on this optimum sound speed value. Therefore, the ultrasonic beam can always be focused on a predetermined focus regardless of the change in the sound velocity in the living body. As a result, the image quality and resolution of the ultrasonic tomographic image are improved.

In particular, when a high-definition dynamic focusing method is used in which the delay time is controlled continuously (especially in pixel units) according to different depths, each focusing point is data regardless of the in-vivo sound velocity value. Since it coincides with the acquisition site, it is possible to obtain an ultrasonic tomographic image with very high resolution and high image quality.

In the above embodiment, the case where the delay time corresponding to the optimum set sound velocity value is given to the received signal has been described, but the present invention is not limited to this.
A similar delay time can be given to the transmission signal.

Further, if the value is unstable in the calculation of the correlation coefficient only once at each set sound velocity value, step S5
After the processing of step S3, the processing of steps S3 to S5 is repeated a predetermined number of times in the same measurement area to calculate a predetermined number of correlation coefficients (FIG. 9; step S10). It is also possible to obtain the arithmetic mean of the predetermined number of correlation coefficients calculated in the processing of step S11 and perform the processing of step S6 and thereafter.

Further, instead of calculating a plurality of correlation coefficients in the same measurement area, if the correlation coefficient is obtained in a certain measurement area, the measurement areas are sequentially moved to a plurality of parts and the measurement areas of the parts are measured. Step S3 to Step S5
Is performed to calculate the correlation coefficients of the plurality of parts (step S15), and when the correlation coefficients of the plurality of parts are all calculated, the phase of the plurality of parts calculated in the process of step S16 is calculated. Find the arithmetic mean of the relations,
It is also possible to perform the processing from step S6 onward.

As described above, a more accurate correlation coefficient can be obtained by averaging the correlation coefficients respectively obtained from the same measurement region or a plurality of regions.

Although the depth to be measured and the region of interest (measurement region) to be measured are set in step S2, this measurement region may be set in advance to a predetermined region (FIG. 11, step S2A).

Further, in this embodiment, the method of changing the delay time according to the change of the set sound velocity and calculating the correlation coefficient from the signal by the adjacent scanning is described. At this time, the delay time newly set is used. Ultrasound images may be displayed simultaneously. This makes it possible to monitor how the image quality (resolution) of the ultrasonic image is improving.

In the first embodiment described above, only the received signal in the predetermined measurement area is extracted using the gate circuit 80 and the designator 81, but the present invention is not limited to this, and for example, FIG. 12 shows a modification of the first embodiment.

In this modification, two or more adjacent received signals output from the adder 70 are directly sent to the A / D converter 82 'of the delay time control unit so that the correlation strength C (0) is obtained. Has become.

That is, in the delay time control unit of this modification, the A / D converter 82 'is connected to the branch output side of the adder 70. The output side of the A / D converter 82 'has substantially the same configuration as that of the first embodiment, and the other components are also substantially the same as those of the first embodiment, and therefore the description thereof will be omitted.

In the present embodiment, after the end of step S1 in FIG. 6 of the first embodiment, that is, the reflected signal (received signal) e1 (t) 'and the reflected signal (received signal) e output from the adder 70 by two adjacent scans. e2 (t) 'is the direct A / D converter 8
2 ', is A / D converted by the A / D converter 82', and then stored in the buffer memories 83 and 83, respectively (FIG. 13; step S3A). Hereinafter, step S
The process of 4 to step S8 is performed similarly to the first embodiment, and the minimum correlation coefficient Cmin (0) and the minimum correlation coefficient Cmi are obtained.
The optimum set sound velocity value V _xs corresponding to n (0) is obtained. Then, the optimum focusing delay time τ _fr and the final optimum delay time τ are given to the new reception signal by the reception delay circuits 66 (1) to 66 (M) based on the optimum set sound velocity value V _xs .

Also in this modification, as in the first embodiment described above, the ultrasonic beam can be focused on a predetermined focus regardless of the change of the sound velocity in the living body, so that the image quality of the ultrasonic tomographic image is improved. , The resolution is improved.

(Second Embodiment) Another configuration (more specific configuration) of the delay time control unit according to the present invention, which performs correlation processing on received signals from two adjacent directions to obtain an optimum delay time, is described below. FIG. 14 shows a second embodiment.

In the delay time control unit of this embodiment, the output side of the adder 70 is branched, and mixers 90a and 90b connected to the branched outputs, and the mixers 90a and 90a, respectively.
The low-pass filters 91a and 91b respectively connected to the output side of 90b, and the low-pass filters 91a and 91b.
A / D converters 92a respectively connected to the output side of b
92b, two buffer memories 93 ... 93 connected to each of the A / D converters 92a and 92b, and a correlation processing circuit 94 connected to the read side of each buffer memory 93.
An optimum sound velocity value detection circuit 95 connected to the output side of the correlation processing circuit 94, and a delay time control circuit 64 connected to the output side of the optimum sound velocity value detection circuit 95. The delay time control unit includes a reference signal generator 96,
And a π / 2 phase shifter 97 connected to one of the branched outputs of the reference signal generator 96, the output of the π / 2 phase shifter 97 is connected to one mixer 90a, and the reference signal The other output of the generator 96 is directly connected to the mixer 90b. Note that the other configurations are the same as the configurations of the first embodiment (FIG. 5), and thus description thereof will be omitted.

Next, the overall operation of the ultrasonic diagnostic apparatus according to this embodiment will be described, particularly focusing on the autofocus processing operation by delay time control according to the correlation strength between adjacent received signals. It should be noted that the description of the operation substantially equivalent to that of the first embodiment is partially omitted or simplified.

First, the received signal e1 from the scanning direction θ
(t) and the received signal e2 (t) from the scanning direction θ + Δθ are
Each can be approximately mathematically expressed by the following equations.

[0080]

(Equation 4) Where Y _n is the ultrasonic reflection coefficient of the _nth scatterer, t _n
Is the time until the sound wave returns from the nth reflector, ω
₀ (= 2πf ₀ ) is the ultrasonic angular frequency. Also, e1
(t) is the received signal from the N1th to N2th scatterers. On the other hand, e2 (t) is the received signal from the N1'th to N2'th scatterers, and both received signals include those from the common scatterer, as described above. Is.

In FIG. 14, as in the first embodiment,
After the end of step S1 in FIG. 6, that is, the output from the adder 70 (received signal by two adjacent scans)
Is represented by e1 (t) and e2 (t) shown in the above equation (4), and these received signals e1 (t) and e2 (t) are respectively generated by the mixer 9
0a and mixer 90b. On the other hand, one of the reference signals sin (ω ₀ t) having a frequency substantially equal to the ultrasonic (angular) frequency output from the reference signal generator 96 is directly input via one input terminal of the mixer 90b, It is multiplied with the adder outputs e1 (t) and e2 (t).

Although the DC component and the 2ω ₀ component are output from the mixer 90b, the 2ω ₀ component is removed by the low pass filter 91b, and the signal represented by the following equation is obtained.

[0083]

(Equation 5) However, [e1 (t)] i and [e2 (t)] i are e1 (t) and e2
“Cos component” of (t) (imaginary component; imaginary part)
Represents

On the other hand, of the reference signal sin (ω ₀ t) output from the reference signal generator 96, the other is shifted by 90 ° (π / 2) in phase by the π / 2 phase shifter 97 and cos ( ω ₀ t) is input through one input terminal of the mixer 90a and is multiplied by the adder outputs e1 (t) and e2 (t). Further, in the output from the mixer 90a, the high-frequency component is removed by the low-pass filter 91a in the same manner as the output from the mixer 90b described above, and the signal represented by the following equation is obtained.

[0085]

(Equation 6) However, [e1 (t)] r and [e2 (t)] r are e1 (t) and e2
Indicates the "sin component" (real component; real part) of (t).
That is, the signals e1 (t) and e output from the adder 70
2 (t) is the mixers 90a and 90b, the low-pass filter 9
By the action of 1a and 91b, the cos component of the signal,
Quadrature detection is performed on the sin component (FIG. 15, step S2).
0).

The signals subjected to the quadrature phase detection are converted into digital signals by the A / D converters 92a and 92b and then temporarily stored in the buffer memories 93 ... 93. The signals stored in the buffer memories 93 ... 93 are combined as a complex number by the arithmetic circuit of the correlation processing circuit 94 as shown in the following equation (step S21).

[0087]

(Equation 7)

The combined complex signals E1 (t) and E2 (t) are
Correlation processing is performed by the arithmetic circuit according to the following equation.

[0089]

(Equation 8) Where E2 (t) ^* is the complex conjugate function of E2 (t), that is,

[Equation 9] E2 (t) ^* = [e2 (t)] r-j [e2 (t)] i (step S22). The set sound velocity value V _x1 related to the received signal and the calculated correlation coefficient C1 (0) are temporarily stored in the memory of the correlation processing circuit 94 (step S23).

Thereafter, as in the first embodiment, step S
Processing of 6 or less is performed. That is, the correlation coefficient is sequentially obtained while changing the set sound velocity value, and the optimum set sound velocity value detection circuit 95 finds the minimum correlation coefficient Cmin (0) and the optimum set sound velocity value V _xs . Then, the optimum focusing delay time τ _fr and the final optimum delay time τ are set by the delay time control circuit 64 based on the obtained optimum setting sound velocity value V _xs , and the optimum delay time τ is set to the reception delay circuit 66. (1) ~
By giving a new received signal at 66 (M), it is possible to display an ultrasonic image which is optimally received and focused without depending on the sound velocity value.

As described above, according to this embodiment,
Similar to the first embodiment, since the ultrasonic beam can be focused on a predetermined focus regardless of the change of the sound velocity in the living body, especially when the high-definition dynamic focusing method close to the pixel unit is used. It is possible to obtain an ultrasonic tomographic image with very high resolution.

In particular, according to this embodiment, the received signal output from the adder is converted into a complex signal through the mixer and the low-pass filter, A / D converted, and stored in the memory. Sampling and storage in a memory are easier than in the configuration of the first embodiment.

In the first and second embodiments, the case where the delay time given to the transmission or reception signal of the m-th transducer is calculated by using the above-mentioned formula (3) for each set sound velocity value has been described. However, the present invention is not limited to this. For example, the delay time setting circuit has a storage unit such as a ROM (Read Only Memory), and the delay time data is stored in advance in this storage unit. Then, the CPU of the delay time control circuit can read and control the delay time data stored in the storage unit and give it to the transmission or reception signal.

In general, the storage unit stores delay times given to M (M) transducers with respect to the focal length F ₀ (or reception time). That is, assuming that the provisional in-vivo sound velocity is Vx1, the focusing delay time τ _f (m) given to the transmission or reception signal of the m-th transducer when focusing the ultrasonic wave at the focal length F ₀ is ,

(Equation 10) Becomes Here, K is a proportional constant. Storage unit (hereinafter,
In the ROM (described as a table), τ _f (m) is stored for F ₀ . Here, in order to set the focus point to F ₀ and increase the set sound velocity value V _x1 by (ΔV _x1 ), the CPU of the delay time control circuit 64 uses the focus point stored in the ROM for the focus point F ₀ . Delay time data τ
_f (m) is F ₀ + ΔF (ΔF is the degree of change in focal length)
The read control may be performed so that it is used for the received signal from (of course, the delay time finally given is τ (= τ _f + τ _s )). However, ΔF = (ΔV _x1 /
V _x1 ).

That is, it is necessary to control the delay time (focusing delay time) in advance according to the sequential change of the set sound velocity value.
This can be implemented very easily by changing the focal length based on the change of the read address of the delay time data stored in the OM.

Further, the focusing delay time τ _f and the deflection delay time τ _s are rarely stored in independent ROMs (storage units), and the combined delay time (ie,
It is often stored in ROM as τ _f + τ _s ), but even in this case, the total delay time can be controlled by controlling the read address of the total delay time τ according to the change of τ _f. Become.

Further, also in the present embodiment, as in the first embodiment, it is possible to extract only the signal in a certain measurement region using the gate circuit and perform the above-mentioned correlation processing.
Various modifications (FIGS. 9 to 11) described in the first embodiment can be performed.

(Third Embodiment) In the above-described first and second embodiments, the movement of the focal point that occurs when the set sound velocity is different from the actual in-vivo sound velocity, and a measure for improving image quality deterioration due to this movement will be described. However, in the case of the sector scanning method,
At the set sound velocity and the actual in-vivo sound velocity, it appears as an error in the sector deflection angle. That is, when the difference is ΔV _x1 ,
The actual deflection angle increases or decreases.

The ultrasonic diagnostic apparatus according to this embodiment has means for correcting the increase or decrease of the deflection angle described above.

As the correction means, in the ultrasonic diagnostic apparatus according to the present embodiment, in the configuration shown in FIG. 14, the delay time control circuit 64 has a storage section such as a ROM table, and this storage section corresponds to θ ₀ . Delay time data for scanning angle τ
_s (m) is stored. Sector deflection angle θ ₀ and set sound velocity are

[Equation 11] It is represented as However, K'is a proportional constant.

For example, the storage unit such as the ROM table of the delay time control circuit 64 stores the delay time data τ _s for θ ₀ .
(M) is stored. Here, the deflection angle is θ ₀ ,
In order to increase the set sound velocity value V _x1 by (ΔV _x1 ),
The CPU of the delay time control circuit 64 may use the scanning angle delay time data τ _s (m) stored in the ROM for the deflection angle for the deflection of “θ ₀ + Δθ _x1 ”. However, “Δθ _x1 = − (ΔV _x1 / V _x1 ) tan θ ₀ ”.

That is, controlling the delay time in accordance with the sequential change of the set sound velocity value can be performed very easily by changing the read address of the delay time data stored in the ROM in advance. However, regarding the deflection angle,
Other methods are possible. In general, the focusing delay time τ _f and the deflection delay time τ _s are rarely stored using independent ROMs (storage units), and the combined delay time τ (that is, τ _f + τ _s ) is stored in the ROM. Often stored in. In such a case, the correction of the change angle can be performed by the display system as shown below.
The delay time can be controlled more easily than the read control processing from M.

That is, when the delay time τ _s is used and the set sound velocity value is V _x1 + ΔV _x1 , as described above,

(Equation 12) The display range (display sector angle) of the display monitor may be adjusted accordingly.

FIG. 16 shows the configuration of an ultrasonic diagnostic apparatus provided with the delay time control means based on such a display system. This ultrasonic diagnostic apparatus includes an image memory control circuit 100 equipped with a computer circuit that controls the writing / reading controller 75a. This image memory control circuit 100
Is connected to the optimum set sound velocity value detection circuit 95 '.
The optimum set sound velocity value detection circuit 95 ′ of the present embodiment obtains the optimum set sound velocity value corresponding to the minimum correlation coefficient and its minimum correlation function based on the correlation coefficient data sent from the correlation processing circuit 94, and further The optimum deflection angle data (sector scanning angle data) is obtained based on the optimum set sound velocity value, and the optimum deflection angle data is sent to the image memory control circuit 100. The image memory control circuit 100 controls the write / read controller 75a based on the sent optimum deflection angle data to control the write address of the image signal written in the image memory 74. It should be noted that other configurations are the same as those of the second embodiment shown in FIG.
Since the configuration is substantially the same as that shown in, the description thereof will be omitted.

In this embodiment, when transmitting the ultrasonic pulse into the living body, first, the transmission rate signal generator 63
The rate pulse output from the transmission delay circuit 62
(1) to 62 (M), the delay time τ _f and the delay time τ _s calculated and determined by the delay time control circuit 64 based on the sound velocity value V _x1 as a preset provisional value are given. M channel oscillator drive circuit (pulsar) 61
(1) to 61 (M). That is, the delay time τ set in the m-th transmission delay circuit 62 (m)
(M) is “τ _f (m) + τ _s (m)”, and τ
_f (m) and τ _s (m) are set as in the following equation.

[0106]

(Equation 13) Here, d is the transducer arrangement interval, V _x1 is the in-vivo sound velocity, F
₀ is the focal length, and θ ₀ is the deflection angle (sector angle).

The pulsars 61 (1) to 61 (M) send the drive pulse to the ultrasonic transducer 60 (1) at the transmission timing determined according to the outputs of the transmission delay circuits 62 (1) to 62 (M). To 60 (M), and as a result, the ultrasonic transducers 60 (1) to 60 (M) are driven and ultrasonic waves are radiated into the living body.

A part of the ultrasonic waves radiated into the living body is reflected by the boundary surface of the organ in the living body or the acoustic scatterer of the living tissue, and again by the ultrasonic transducers 60 (1) to 60 (M). It is received and converted into an electrical signal. This reception signal is amplified through the preamplifiers 65 (1) to 65 (M), and then, similarly to the transmission, the delay time τ _f and the delay time τ _s at the time of reception determined based on the set sound velocity value V _x1. Is given by the reception delay circuits 66 (1) to 66 (M) to adder 7
Sent to 0.

The output from the adder 70 (two scans (reflection signals obtained in the scanning directions θ and θ + Δθ)) is represented by e1 (t) and e2 (t) shown in the above equation (4), The received signals e1 (t) and e2 (t) are obtained by the mixer 90a and the mixer 90b and the low-pass filters 91a and 91b, respectively, and the signals shown in the above formulas (5) and (6) are obtained (second embodiment). Morphology, see FIG. 15, step S20). These signals are stored in the buffer memories 93 ... 93 as digital signals through the A / D converters 92a and 92b, and then are combined by the arithmetic circuit of the correlation processing circuit 94 into the complex numbers shown in the above equation (7). (See step S21 in FIG. 15) Further, the correlation processing is performed by the arithmetic circuit according to the above-mentioned expression (8) (step S22-FIG. 15).
(See S23).

Hereinafter, similar to the first and second embodiments, the correlation coefficient is sequentially obtained while changing the set sound velocity value, and the optimum set sound velocity value detection circuit 95 'produces the minimum correlation coefficient Cmin.
(0) ′ and the optimum set sound velocity value V _xs ′ are _calculated (see FIG. 1).
7, step S30).

Then, the optimum set sound velocity value detection circuit 95 '
Is the calculated optimum sound velocity value V as shown in FIG.
'based on, the optimum set sound velocity value V _{xs' xs} optimum deflection angle (sector scan angle) where the data corresponding to the (12)
(Step S31), the optimum deflection angle data is sent to the image memory control circuit 100 (step S3).
2). Similarly, the optimum focusing point (data acquisition depth) is also obtained by the above equation (12) and sent to the image memory control circuit 100.

The image memory control circuit 100 obtains (sampling) optimum deflection angle data and optimum data sent.
Write / read controller 75a based on depth data
To control the write address of the digital image signal sent via the A / D converter 73 to the image memory 74 (step S33). That is, the image memory 7
Since the ultrasonic scanning signal (digital image signal) written (stored) in No. 4 becomes the writing position corresponding to the optimum scanning angle and the data sampling depth at the optimum sound velocity value, the D / A converter 76 is used. Through this, the image quality of the ultrasonic tomographic image displayed on the monitor 77 is improved.

It goes without saying that the correction associated with the increase or decrease of the deflection angle can be used simultaneously with the correction associated with the movement of the focal point described in the first and second embodiments. Further, the correction associated with the movement of the focal point and the correction associated with the increase / decrease of the deflection angle do not necessarily have to be performed at the same time. In particular, for the purpose of improving the resolution of the ultrasonic tomographic image, only the correction of the focusing point may be performed. .

Also in the present embodiment, as in the first embodiment, it is possible to extract only the signal in a certain measurement region by using a gate circuit and perform the above-mentioned correlation processing. It is also possible to make the various modifications described (FIGS. 9-11).

Furthermore, in the above-mentioned embodiments, the delay time control of the present invention has been described using the electronic sector scanning type ultrasonic diagnostic apparatus, but the present invention is not limited to this, and electronic linear scanning, It is applicable not only to the electronic convex scanning type ultrasonic diagnostic apparatus but also to a mechanical scanning type ultrasonic diagnostic apparatus using an annular array probe.

Furthermore, in the above-described embodiment, the example in which the delay time control is performed on the reception signal is shown, but it may be performed on either the transmission signal or the reception signal.

On the other hand, the present invention evaluates the shape of the ultrasonic beam by the correlation processing between the received signals based on two or more adjacent scans. The term "adjacent" as used in the present specification means strictly. 18 does not need to be the adjacent scan in FIG.
As shown in FIG.
In the sector scan in which the scan number 10) is performed, not only the selection of the scan line 1 and the scan line 2, but also the scan line 1 and the scan line 3 is performed.
Alternatively, like scanning line 1 and scanning line 4, selection may be made by jumping over several scanning lines. This jumping range is
It is at least up to the scanning line where the received signal which can be expected to have a correlation with the received signal on the scanning line 1 is obtained.

The optimum scanning line selecting method is determined by the beam width and the scanning density. further,
When calculating the correlation coefficient at each of a plurality of points and obtaining a more accurate value by arithmetic mean, for example, scan 1 and scan 4, scan 2 and scan 5, scan 3 and scan 6, ... Various selection methods are possible.

Further, in the above-described embodiment, the correlation processing is performed on two received signals by two adjacent scans, but the present invention is not limited to this. For example, a plurality of adjacent scans by a plurality of adjacent scans may be performed. Correlation processing can also be performed between received signals.

Although the description of the configuration of the blood flow unit portion of the Doppler signal is omitted in the embodiment of the present invention, it is shown in FIG. 19 of the conventional example in each diagnostic device of the first to third embodiments. The blood flow unit portion may be added as a constituent element, and the operation of this blood flow unit portion is the same as that of the conventional example.

[0121]

As described above, according to the present invention, even if the in-vivo sound velocity value changes, for example, the ultrasonic beam can be always focused at a predetermined depth position. The resolution degradation caused by the error between the set focus point and the actual focus point that was generated on the conventional ultrasonic tomographic image due to the change in the value is significantly reduced, regardless of the physique of the subject or the examination site. Diagnosis is always possible under optimal conditions. Further, in particular, the present invention makes it possible to focus an ultrasonic beam at a predetermined depth without error, and therefore, it is particularly effective when a high-definition dynamic focusing method close to a pixel unit is performed, and high resolution is achieved. A high-quality ultrasonic tomographic image can be obtained, and diagnostic accuracy can be further improved.

[Brief description of drawings]

FIG. 1A is a diagram schematically showing an ultrasonic transmission / reception part of an ultrasonic diagnostic apparatus and an ultrasonic beam having a wide beam width for explaining the common concept of the present invention, and FIG. The figure which shows the cross-sectional beam shape at the time of cutting the ultrasonic beam with a wide beam in A) at line L1.

FIG. 2A is a diagram schematically showing an ultrasonic transmission / reception part of an ultrasonic diagnostic apparatus and an ultrasonic beam having a narrow beam width for explaining the common concept of the present invention, and FIG. The figure which shows the cross-sectional beam shape at the time of cutting the ultrasonic beam with a narrow beam width in A) at line L2.

FIG. 3 is a graph showing the relationship between beam width and correlation intensity.

4A is a diagram showing a signal waveform of a reception signal e1 (t) from a scanning direction θ, and FIG. 4B is a signal waveform of a reception signal e2 (t) from a scanning direction (θ + Δθ). The figure (c) is a figure showing the formula which shows a correlation coefficient.

FIG. 5 is a block diagram schematically showing the overall configuration of the ultrasonic diagnostic apparatus according to the first embodiment.

FIG. 6 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the first embodiment.

FIG. 7 is a diagram showing an example of a measurement region designated on an ultrasonic tomographic image.

FIG. 8 is a graph showing an example of the relationship between the set sound velocity and the correlation strength.

FIG. 9 is a schematic flowchart showing an example of delay time control processing according to the correlation strength of the ultrasonic diagnostic apparatus according to the first embodiment.

FIG. 10 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the first embodiment.

FIG. 11 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the first embodiment.

FIG. 12 is a block diagram schematically showing an overall configuration of an ultrasonic diagnostic apparatus according to a modified example of the first embodiment.

FIG. 13 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the modified example of the first embodiment.

FIG. 14 is a block diagram schematically showing the overall configuration of an ultrasonic diagnostic apparatus according to a modified example of the second embodiment.

FIG. 15 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the second embodiment.

FIG. 16 is a block diagram schematically showing the overall configuration of an ultrasonic diagnostic apparatus according to a modified example of the third embodiment.

FIG. 17 is a schematic flowchart showing an example of delay time control processing of the ultrasonic diagnostic apparatus according to the third embodiment.

FIG. 18 is a diagram for explaining an example of scanning line selection in adjacent scanning.

FIG. 19 is a block diagram showing the overall configuration of a conventional ultrasonic diagnostic apparatus.

FIG. 20 is a diagram for explaining the principle of the electron focusing method.

FIG. 21 is a diagram for explaining the principle of the dynamic focusing method.

FIG. 22 is a diagram for explaining a problem of the conventional dynamic focusing method.

[Explanation of symbols]

 50 Transmitter 51 Receiver 52 Display 53 Delay Circuit 54 Transducer 55 Delay Time Control Circuit 60 (1) -60 (M) Ultrasonic Transducer 61 (1) -61 (M) Transducer Drive Circuit (Pulsar) 62 (1) to 62 (M) transmission delay circuit 63 transmission rate signal generator 64 delay time control circuit 65 (1) to 65 (M) preamplifier 66 (1) to 66 (M) reception delay circuit 70 adder 71 logarithmic amplifier 72 Detection Circuit 73 A / D Converter 74 Image Memory 75, 75a Writing / Reading Control Circuit 76 D / A Converter 77 TV Monitor 82 A / D Converter 83,83 Buffer Memory 84,94 Correlation Processing Circuit 85,95 Optimal Set sound velocity value detection circuit 90a, 90b Mixer 91a, 91b Low pass filter 92a, 92b A / D converter 93 Buffer memory 96 units Signal generator 97 [pi / 2 phase shifter 100 image memory control circuit

Claims (21)

[Claims] 1. A scanning means for scanning an ultrasonic signal for each scanning line on a cross section in a subject, and a plurality of ultrasonic echo signals obtained in response to the scanning are delayed and focused. In the ultrasonic diagnostic apparatus including a generating unit that generates a received signal, a calculating unit that calculates an amount indicating a correlation between the received signals based on the received signals on a plurality of scanning lines, and the calculated correlation. An ultrasonic diagnostic apparatus, comprising: a focusing degree control means for controlling the focusing degree of the received signal based on the amount. 2. The calculating means calculates a correlation amount for each of the plurality of parameter values based on the received signals on the plurality of scanning lines obtained for each of the plurality of parameter values that govern the degree of convergence of the received signal. The ultrasonic diagnostic apparatus according to claim 1, which is means for performing. 3. The delay time for optimizing the delay time given to the plurality of echo signals based on the parameter value that minimizes the correlation amount among the correlation amounts for each of the plurality of parameter values. Claim 2 which has the optimization means
An ultrasonic diagnostic apparatus as described in the above. 4. The focusing degree control means optimizes a focusing position at which the received signal is acquired, based on a parameter value that minimizes the correlation value among correlation values for each of the plurality of parameter values. The ultrasonic diagnostic apparatus according to claim 2, further comprising position optimization means. 5. The ultrasonic diagnostic apparatus according to claim 3, wherein the parameter value is an in-vivo sound velocity value. 6. The ultrasonic diagnostic apparatus according to claim 1, wherein the received signals on the plurality of scanning lines are signals in a range where correlation can be expected. 7. The ultrasonic diagnostic apparatus according to claim 6, wherein the reception signals on the plurality of scanning lines are reception signals on adjacent scanning lines. 8. A tomographic image generation unit that generates an ultrasonic tomographic image of the cross section based on the received signal, a display unit that displays the ultrasonic tomographic image on a monitor, and an ultrasonic tomographic image displayed on the monitor. A designation unit for designating a desired region on the image, wherein the calculation unit is a unit for calculating a correlation amount between the reception signals based on reception signals on a plurality of scanning lines in the designation region. 1. The ultrasonic diagnostic apparatus according to 1. 9. The scanning means includes means for repeatedly scanning the ultrasonic signal on the same scanning line a plurality of times.
The calculating means calculates a correlation amount for each of the plurality of repeated scans based on the reception signals on the plurality of scanning lines obtained for each of the plurality of repeated scans, and calculates the correlation for each of the calculated plurality of repeated scans. The means for averaging the amounts, and the focusing degree control means is means for controlling the focusing degree of the received signal based on the averaging amount of correlation.
An ultrasonic diagnostic apparatus as described in the above. 10. The calculating means calculates a correlation amount for each different portion based on a received signal on a scanning line of a different portion on the cross section, and adds and averages the calculated correlation amounts for each of a plurality of repeated scans. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the focusing degree control means is means for controlling the focusing degree of the received signal based on the correlation amount obtained by averaging. 11. The ultrasonic diagnostic apparatus according to claim 1, further comprising a scanning angle control means for controlling a scanning angle of the ultrasonic signal based on the correlation amount obtained by the calculation means. 12. A scanning means for scanning an ultrasonic signal by applying a deflection angle to a cross section in a subject, and a plurality of ultrasonic echo signals obtained in response to the scanning with a delay time for focusing. In the ultrasonic diagnostic apparatus including a generating unit that generates the received signal, the calculating unit calculates the amount indicating the correlation between the received signals based on the received signals on a plurality of scanning lines, and the calculated unit. An ultrasonic diagnostic apparatus, comprising: a deflection angle control means for controlling a deflection angle of the ultrasonic signal based on a correlation amount. 13. The ultrasonic diagnostic apparatus according to claim 12, further comprising a focus position control unit that controls a focus position at which the received signal is acquired. 14. The calculation means calculates the correlation amount for each of the plurality of parameter values based on the received signals on the plurality of scanning lines obtained for each of the plurality of parameter values that control the deflection angle of the ultrasonic signal. 14. The calculation means is a means for calculating the deflection angle, and the deflection angle control means is a means for controlling the deflection angle based on a parameter value that minimizes the correlation amount among the correlation amounts for each of the plurality of parameter values. The ultrasonic diagnostic apparatus described. 15. The ultrasonic wave according to claim 14, wherein the deflection angle control means is a means for controlling the deflection angle by giving a delay time for the deflection angle to the ultrasonic signal based on the correlation amount. Diagnostic device. 16. A tomographic image generation unit that generates an ultrasonic tomographic image of the cross section based on the received signal, and a display unit that displays the ultrasonic tomographic image on a monitor, wherein the display unit includes: The memory includes a memory in which a received signal based on ultrasonic signal scanning is written, and a writing / reading control unit that scan-converts the received signal written in the memory and reads out as an image signal. Means for obtaining deflection angle data corresponding to the parameter value having the smallest amount, and write address of the received signal to the memory by the write / read control means according to the obtained deflection angle data. 15. The ultrasonic diagnostic apparatus according to claim 14, further comprising address correction means for correcting the error. 17. A designating unit for designating a desired region on the ultrasonic tomographic image displayed on the monitor, wherein the computing unit calculates a correlation amount between the received signals in a plurality of scans within the designated region. The ultrasonic diagnostic apparatus according to claim 16, which is a means for performing calculation based on a received signal on the line. 18. The scanning means has means for repeatedly scanning the ultrasonic signal on the same scanning line a plurality of times, and the arithmetic means has a plurality of the plurality of scan signals obtained for each of the plurality of repeated scans. Is a means for calculating the correlation amount for each of the plurality of repetitive scans based on the received signal on the scanning line, and adding and averaging the calculated correlation amount for each of the repetitive scans.
17. The ultrasonic diagnostic apparatus according to claim 16, wherein the deflection angle control means is means for controlling the deflection angle of the ultrasonic signal based on the added and averaged correlation amount. 19. The calculating means calculates a correlation amount for each different portion from the received signals on the scanning lines of different portions on the cross section, and adds and averages the calculated correlation amounts for each of a plurality of repeated scans. 17. The ultrasonic diagnostic apparatus according to claim 16, wherein the deflection angle control means is a means for controlling the deflection angle of the ultrasonic signal based on the averaged correlation amount. 20. A step of giving a delay time to a plurality of ultrasonic echo signals obtained by scanning an ultrasonic signal for each scanning line on a cross section in a subject to generate a focused reception signal, Calculating a quantity indicating the correlation between the generated reception signals based on the reception signals on a plurality of scanning lines, and the plurality of echo signals based on the calculated correlation quantity for controlling the degree of focusing And a step of optimizing a delay time given to the delay time optimization method. 21. The calculation step calculates a correlation amount for each of the plurality of parameter values based on the reception signals on the plurality of scanning lines obtained for each of the plurality of parameter values that govern the degree of focusing of the reception signal. The delay time optimizing step is a step of optimizing a delay time given to the plurality of echo signals based on a parameter value that minimizes the correlation amount among the correlation amounts of the plurality of parameter values. The delay time optimization method according to claim 20, wherein