JP2002143153A - Method for arranging phase of transmission or reception wave and ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform adaptive measurement corresponding to a subject by automatically adjusting a set sonic speed to be used for a phase arrangement processing to a value being the same as or close to an actual medium sonic speed. SOLUTION: A transmission or reception wave phase arranging method is characterized in such a manner that an ultrasonic reflection wave from the inside of the subject is received by vibrators so as to delay received echo sounder reception signals based on the set sonic speed and to arrange the phase (21), a difference between the set sonic speed and the actual medium sonic speed is estimated based on the phase-arranged reception signals (22), a processing for estimating the medium sonic speed based on the difference is performed concerning the measurement areas of the subject (23) and certainty is evaluated concerning medium sonic speed estimation values obtained by the measurement so as to set the medium sonic speed estimation value with the highest evaluation as a common set sonic speed with respect to the measurement areas (24).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus used for medical diagnosis, and more particularly, to a phasing process for focusing an ultrasonic transmission / reception signal.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus applies an ultrasonic probe to the surface of a subject, transmits ultrasonic waves from the probe to the subject, and receives reflected waves from inside the subject. Based on the received signal, the state of each part of the subject is displayed as an image such as a tomographic image and used for diagnosis. In general,
The ultrasonic probe is formed by arranging a plurality of transducers at regular intervals in a linear, curved or planar manner. Then, a transducer group to be operated is selected from among the plurality of transducers, and transmission and reception of ultrasonic waves are performed. A beam is formed by sequentially moving, for example, the aperture formed by the group of transducers selected in this manner. In the sector scanning probe, the beam is deflected and scanned without moving the aperture.

In driving a group of transducers having a selected aperture, a transmission signal supplied to each transducer is delayed to shift the supply timing, and ultrasonic waves radiated from each transducer are transmitted to a desired portion (focal point). Is performed. Similarly, the reflected wave (reflected echo) from the subject is received by each transducer forming the aperture, and the received signal is amplified and then subjected to a process of delaying each received signal, and the same signal is received from a desired portion. A phasing process is sometimes performed to match the phases of the reflected waveform components. Then, after adding the received signals subjected to the phasing processing to a sufficiently large signal, performing signal processing such as compression processing, filtering processing, and γ correction, and performing scan conversion such as coordinate conversion and interpolation to obtain an image. It is displayed.

The delay time of each signal in the above-described transmission phasing processing and reception phasing processing is obtained by dividing the difference between the distance from each transducer to the focal point by the sound velocity of the propagation medium of the ultrasonic wave and converting the time into time. Becomes As the sound speed of the propagation medium, an assumed set sound speed is usually used. However, living tissue, which is a medium,
Since the sound speed may not be uniform and there are individual differences,
There may be an error between the set sound speed and the sound speed at the time of actual measurement. With such a difference in sound speed, focus adjustment is not properly performed, and the quality of an obtained image is deteriorated.

In order to cope with such a problem, Japanese Patent Application Laid-Open No. Hei 6-269449 has proposed a method for appropriately estimating the propagation speed of ultrasonic waves in living tissue. According to this, a medium through which an ultrasonic wave propagates is assumed by various coefficients including a sound velocity, and a deformation of a propagating waveform is calculated by a theoretical equation including a medium coefficient assuming deformation, and the medium is compared with an actually measured waveform to compare with a measured sound velocity. By estimating the coefficients including
The accuracy of estimating the sound velocity of the medium is improved.

Further, Japanese Patent Application Laid-Open No. 2-274235 proposes that an operator instructs and corrects the medium sound speed by input means such as a console to perform an optimal phasing process. Japanese Patent Application No. 4-252576 discloses that a human body is regarded as an inhomogeneous medium, and a delay time is adjusted in accordance with an object to automatically focus on an unfocused area on a tomographic image. It has been suggested that they be combined.

[0007]

However, the method described in Japanese Patent Application Laid-Open No. 6-269449 requires a medium to be assumed, requires a complicated operation, and must be compared with an actually measured waveform. , It takes time to process. Therefore, it is not necessarily suitable for adaptive measurement in which measurement is performed by adjusting the set sound speed in accordance with the medium sound speed of the subject.

Further, the method described in Japanese Patent Application Laid-Open No. 2-274235 is not a method for automatically estimating the sound velocity of a medium, so that the operator feels a burden and lacks accuracy. In addition, the method disclosed in Japanese Patent Application No. 4-252576 is not a method that focuses on the sound velocity of a medium, and thus has a problem that it is difficult to obtain a good image as a whole.

The problem to be solved by the present invention is that the set sound velocity used for the phasing process can be automatically adjusted to the same or close to the actual medium sound velocity, and adaptive measurement according to the subject can be performed. Is to do.

[0010]

According to the phasing method of the present invention, a reflected wave of an ultrasonic wave transmitted into a subject from a plurality of arranged transducers is received by each of the transducers. The plurality of received signals are delayed based on a set sound speed determined in accordance with the medium of the subject to be phased, and the set sound speed and the actual medium are determined based on the plurality of phased received signals. Estimating the error from the sound velocity, the process of estimating the medium sound velocity based on the estimation error is performed for a plurality of measurement regions of the subject, the plurality of estimated values of the medium sound speed obtained for each measurement region It is characterized in that the likelihood is evaluated, and a medium sound velocity estimated value having the highest evaluation is set as a common set sound velocity for the plurality of regions.

According to such a phasing method, an ultrasonic measurement is performed on an actual subject, and an error between a set sound speed and an actual medium sound speed is estimated based on a plurality of phased received signals. Since the set sound speed is corrected based on the error, adaptive measurement can be realized by a simple operation.

Here, generally, in ultrasonic diagnosis,
Ultrasonic measurement is performed on a plurality of regions or a region of interest of the subject having a certain extent, and an image is formed based on the acoustic information obtained thereby. In this case, the estimated value of the medium sound velocity is often different for each measurement area, and it is possible to adjust or set the set sound velocity for each measurement area in accordance with this, but it is necessary to avoid complexity. I can't.

Therefore, a representative medium sound velocity is selected from among the estimated medium sound velocity values obtained for all or a plurality of areas, and a single medium sound velocity common to each area is set. If so, it is simple and sharp phasing can be performed over those regions, and an image with uniform image quality can be obtained.

Such a problem is solved by evaluating the likelihood of a plurality of estimated sound speeds of a medium obtained by ultrasonic measurement, and setting the estimated value of the estimated sound speed of the medium as a common set sound speed for the plurality of regions. Can be solved.

Here, as a specific example of a method of evaluating the likelihood, there is a method using an evaluation function described below. By the way, a plurality of received signals measured for one measurement region are phased by delaying according to delay times respectively set based on the set sound speed. That is, the timing at which the ultrasonic wave reflected at the set focal point enters each transducer forming the aperture is shifted because the propagation distance of the ultrasonic wave varies depending on the arrangement position of each transducer. Therefore, in order to match the time axis of the received signal received by each transducer, the received signal with the shortest propagation distance is appropriately delayed with respect to the received signal with the longest propagation distance, and the phase of the received signal is changed. A phasing process for matching is performed. The delay time at this time is
The setting is made based on the propagation distance and the sound speed of the propagation medium. If the medium is not uniform, the phase of the received signal will be shifted even if the phase is adjusted. Therefore, the delay time error is estimated by measuring the phase shift of the received signal, the delay time related to phasing is corrected based on the estimation error, and the delay time adapted to the medium (hereinafter, also referred to as the adaptive delay time). Adjustment). When this adaptive delay time is plotted with the vibrator arrangement direction (array direction) as the horizontal axis, an upwardly convex 2
It has the following curve distribution.

By the way, the adaptive delay time distribution corrected based on the delay error sometimes has an overall inclination θ with respect to the delay time distribution at the time of setting. Such a phenomenon occurs, for example, when a high echo (high reflectivity) site exists. If such an inclination θ is adjusted based on a certain adaptive delay time distribution, focusing (focusing) is performed on a high echo portion, and the beam is passed in a direction deviated from the original ultrasonic beam direction. Will be. Therefore, it can be said that the estimated value of the medium sound velocity in the region where the slope θ is the delay time distribution after the correction is large has low probability.

On the other hand, it can be said that the greater the strength A of the received signal, the higher the certainty. The adaptive delay time obtained for each received signal is generally dispersed, but if the dispersion width d is large, it can be said that the likelihood is low. Note that the dispersion width d may be an absolute value of a difference between the adaptive delay time distribution and the delay time distribution at the time of setting. From the above, the evaluation function K of the following equation (1) is set for each area, and the sound velocity of the medium corresponding to the adaptive delay time distribution of the area where K is the largest is evaluated as being most likely. K = A / α + β / d + γ / θ (1) In Expression (1), α, β, and γ are arbitrary coefficients, and are coefficients for appropriately weighting each evaluation term.

Further, when the evaluation of the estimated medium sound velocity value with the highest evaluation does not reach a certain criterion, the set delay time of each area is determined based on the estimated medium sound velocity of each area, and the ultrasonic measurement is performed. It is preferable to repeat the process or to repeat the process at the high speed set in the apparatus. For example, a threshold value Kth is set, and the process is repeated until the evaluation function K exceeds the threshold value Kth. It should be noted that a certain limit number of times can be set for this repetition.

An ultrasonic diagnostic apparatus to which the above-described phasing method is applied can be realized by the following configuration. That is, a probe in which a plurality of transducers for transmitting and receiving ultrasonic waves to and from the subject are arranged, and a transmission signal to be supplied to each transducer of the probe corresponding to the medium of the subject. A transmission phasing unit that delays and outputs the received signals based on the determined set sound speed, and a reception phasing unit that delays and outputs the received signals output from the respective vibrators based on the set delay time. Means, and an ultrasonic diagnostic apparatus comprising: an image processing means for generating an image based on a reception signal output from the wave receiving phasing means and displaying the image on an image display means, wherein the wave phasing means is Signal delay means for respectively delaying and outputting the plurality of received signals based on the set delay time, and estimating the medium sound velocity of the subject based on the plurality of received signals output from the signal delay means Medium sound velocity estimating means for determining a value, A representative sound velocity that evaluates the likelihood of the plurality of estimated medium sound speed values obtained for a plurality of measurement areas of a sample, selects the highest estimated medium sound velocity estimate value, and sets the estimated sound velocity value as a common set sound velocity for the plurality of measurement areas. And selecting means.

In this case, the medium sound velocity estimating means includes error estimating means for estimating delay errors of the plurality of received signals output from the signal delay means, and a plurality of medium sound velocities corresponding to the plurality of medium sound velocities. Storage means for storing a plurality of reference delay times to be set, and comparing means for selecting, from the storage means, the reference delay times which coincide within a certain allowable range with an adaptive delay time obtained by adding an estimated delay error to the set delay time. And a medium sound speed selecting means for obtaining a medium sound speed corresponding to the selected reference delay time as a medium sound speed estimated value.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment of an ultrasonic diagnostic apparatus to which the phasing method of the present invention is applied. FIG. 1 shows a block diagram of a wave phasing unit which is a feature of the present embodiment, and FIG. 2 shows an entire configuration diagram of an ultrasonic diagnostic apparatus.

As shown in FIG. 2, the ultrasonic diagnostic apparatus includes an ultrasonic probe 1, an aperture selection switch 2, a transmission / reception separation circuit 3, a transmission circuit 4, a transmission phasing circuit 5, Receiving circuit 6
, An analog-to-digital converter (ADC) 7, a wave receiving and phasing unit 8, an adding unit 9, a signal processing unit 10, a display unit 11, and a sampling signal generating unit 12. Wave receiving phasing unit 8, adding unit 9, signal processing unit 10
Is formed by digital signal processing means.

The ultrasonic probe 1 is formed by arranging a plurality of transducers in a straight line. Then, the transducer selected by the aperture selection switch 2 is driven to transmit an ultrasonic wave to the subject, and the reflected wave from the subject is received by the selected transducer, whereby the inside of the subject is received. Ultrasonic measurement is performed on a desired site. The ultrasonic beam is formed by moving the aperture. In the case of the sector scanning probe, the ultrasonic beam is deflected to scan the beam without moving the aperture.

The transmission phasing circuit 5 delays a plurality of transmission signals to be supplied to a plurality of transducers forming a selected aperture based on a set sound speed determined in accordance with the medium of the subject. Then, the ultrasonic waves radiated from each transducer are converged at a desired focal point. Transmission circuit 4
Generates a drive pulse based on the transmission signal output from the wave phasing circuit 5, supplies the drive pulse to each transducer via the transmission / reception separation circuit 3 and the aperture selection switch 2, An ultrasonic beam is radiated therein.

The reflected echo from the subject is received by a plurality of transducers having a diameter, and is input to a wave receiving circuit 6 through a diameter selection switch 2 and a transmission / reception wave separation circuit 3. The reception circuit 6 amplifies a plurality of input reception signals into reception signals having good dynamic ranges. The plurality of reception signals amplified by the reception circuit 6 are input to the ADC 9, converted into digital signals, and received by the reception phasing unit 8.
Is input to

The wave receiving phasing section 8 delays the phases of a plurality of received signals based on a set sound speed determined in accordance with the medium of the subject. That is, the timing at which the ultrasonic waves reflected at the focal point enter each transducer is shifted because the propagation distance of the ultrasonic waves varies depending on the arrangement position of each transducer. Therefore,
In order to match the time axis of the received signal received by each transducer, the received signal having the shortest propagation distance is appropriately delayed with respect to the received signal having the longest propagation distance. Thereby, the focus processing of the received signal is performed, and the acoustic information of the focus can be obtained. The wave receiving phasing unit 8 is a part related to a characteristic part of the present invention, and will be described later in detail.

The received signals phased by the wave phasing unit 8 are added to each other in an adding unit 9, grow large, and are input to a signal processing unit 10. The signal processing unit 10 performs well-known signal processing such as log compression, filtering, and γ correction on the output signal of the addition unit 9, and further performs scan conversion such as coordinate conversion and interpolation, and outputs the signal to the display unit 11. I do. In this way, by performing ultrasonic measurement on a region having a certain extent of the subject, a desired image is formed and displayed on the display unit 11 to provide for diagnosis. The sampling signal generator 12 generates a sampling signal for analog-to-digital conversion in the ADC 7.

Here, the method of phasing the transmitted and received waves according to the feature of the present invention will be described in detail by taking the wave phasing section 8 as an example. The delay time of the reception signal in the reception phasing is set based on the propagation distance of the ultrasonic wave from the focal point to the transducer and the sound speed of the propagation medium. However, when the medium is a living tissue, the medium is often non-uniform, and the sound velocity of the medium of the subject varies depending on individual differences. In such a case, even if the phase is adjusted by the set delay time based on the set medium sound speed, the actual sound speed is different from the set medium sound speed. Will deteriorate. The wave receiving phasing unit 8 is configured to solve such a problem.

FIG. 3 shows a detailed configuration diagram of the wave receiving and phasing section 8. As shown, a digital delay unit 21, a delay error estimating unit 22, a delay time comparing unit 23, a medium sound speed selecting unit 24, a digital delay control unit 25, a reference delay time recording unit 27, and a reference sound speed recording And a part 26. As shown in FIG. 3, the digital delay unit 21 has a number of digital delay processes (1 to n) 31 corresponding to the received signal.
And each digital delay processing (1 to n) 3
1 is based on delay data (medium sound speed, propagation distance, delay time, etc.) input from the digital delay control unit 25,
Each received signal is delayed and output to the adder 9.

As shown in FIG. 3, the delay error estimator 22 fetches the delayed received signals of two adjacent channels output from the digital delay processor 31 and detects a delay error of the received signals. Multiple delay error detection processing 3
2 and a delay time error estimating process 33 for estimating a delay time error based on the errors detected thereby. Delay error detection processing 32 in the present embodiment
Detects the phase difference between the received signals of two adjacent channels, for example, by taking a cross-correlation between the received signals of the two adjacent channels. The detected phase difference is input to the delay error estimation processing 33, where the delay error is estimated. In other words, if the actual sound velocity of the medium is the same as the set value and is homogeneous, there is no phase difference between the two received signals. However, if the sound velocity of the medium is not uniform, a phase difference occurs. The delay time error ΔD can be estimated. This delay time error ΔD is obtained for each channel.

For each oscillator determined in this way,
The delay time error ΔD is input to the delay time comparison unit 23.
It is. The delay time comparing section 23 has a digital delay system.
Setting delay for each received signal corresponding to each transducer from the control unit 25
Delay time D is input, where delay time error ΔD
Compensated adaptive delay time D_A= D + ΔD is obtained. This
Adaptive delay time D_AIs the received signal corresponding to each transducer
Required. Incidentally, the delay time D is determined by the arrangement of the vibrators.
When plotting with the direction (array direction) as the horizontal axis,
Of the delay time distribution having a quadratic curve. Based on this value
Delay error D to be compensated_AAdaptive delay by superimposing
Time D_ABecomes The delay time comparison unit 23 determines the calculated adaptive delay
Delay time D_AReference delay time that matches or is close to
Search from the recording unit 26. In the reference delay time recording unit 26
Is the delay time data obtained for a plurality of different medium sound velocities.
Data is stored, and the delay time comparing section 23
Delay time D_ASelect a reference delay time close to. This and
The reference delay recorded in the reference delay time recording unit 26
Time is recorded as a delay time corresponding to discrete sound speed values.
Data of multiple media sound velocities
The adaptive delay time D _AReference delay time that matches
Search may not be possible. In this case, the interpolation or extrapolation method
Estimate by supplementing as appropriate. The adaptive delay time
D_AIs approximated by the delay time distribution of a quadratic surface or curve, and
The reference delay time is approximated by a quadratic surface or curve corresponding to
Expressed as a delay time distribution,
The amount of information can be reduced. In addition, the delay time distribution
The difference is obtained to generate a difference delay time sequence.
By fitting the following straight line, the amount of information
Can be reduced.

The reference delay time selected by the delay time comparison unit 23 is input to the medium sound speed selection unit 24, where the reference medium sound speed recording unit 27 is searched, and the medium sound speed corresponding to the selected reference delay time is selected. . This makes it possible to estimate a sound speed adapted to the actual sound speed of the medium. That is, the reference medium sound speed recording unit 27 records what medium sound speed the reference delay time recorded in the reference delay time recording unit 26 depends on. In this way, the estimated value of the medium sound speed obtained by the medium sound speed selection unit 24 is sent to the digital delay control unit 25 as the set sound speed.

The digital delay control unit 25 changes the set sound speed in accordance with the estimated value of the medium sound speed obtained by the medium sound speed selection unit 24, and sets the received signal corresponding to each transducer based on the changed set sound speed. Control the delay time.

As described above, according to the above-described embodiment,
The set sound speed used for the phasing process can be automatically adjusted to a value equal to or close to the actual medium sound speed, and adaptive measurement according to the subject can be performed. As a result, even if the subject changes, or even if a non-uniform part fits in the living tissue, the ultrasonic measurement can be executed adaptively, and the deterioration of the image quality can be improved.

In the above description, the adjustment of the sound velocity of the medium in one measurement area, that is, one ultrasonic beam and one depth of ultrasonic measurement has been described. However, generally, in order to form a two-dimensional or three-dimensional image, an ultrasonic beam is scanned in both the depth direction and the azimuth direction to measure acoustic information in a plurality of regions. In this case, a plurality of estimated values of the delay time error and the medium sound velocity corresponding to each area are obtained. In this case, the estimated value of the medium sound velocity is often different for each measurement area, and it is possible to adjust or set the set sound velocity for each measurement area accordingly, but it is possible to avoid complication. Absent.

That is, it is better to select a representative medium sound velocity from among the estimated medium sound velocity values obtained for all or a plurality of areas and to set a single medium sound velocity common to each area. Often it is useful. For example, the delay time of each received signal set in the digital delay unit 21 can be analytically determined assuming that the medium is homogeneous. If the speed is set as the sound speed, adjustment relating to measurement can be simplified. Moreover, sharp phasing can be performed over the plurality of regions or the region of interest, and an image with uniform image quality can be obtained.

Therefore, the medium sound speed selection section 24 has a function of selecting a representative medium sound speed for a plurality of regions or regions of interest, and setting a single common medium sound speed for each region. The embodiment of this function basically evaluates the likelihood of a plurality of medium sound velocity estimated values obtained by ultrasonic measurement, and sets the highest evaluated medium sound velocity estimated value to a common setting for the plurality of regions. Set as sound speed.
Here, as a specific example of the method of evaluating the certainty,
There is a method using an evaluation function described below.

[0038] As previously mentioned, when plotted on the horizontal axis the array direction of the transducer adaptive delay time D _A, can be approximated to a quadratic curve distribution of convex upward. This adaptive delay time D _A
May have a gradient θ as a whole with respect to the distribution of the set delay time as shown in FIG. Such a phenomenon occurs, for example, when a high echo (high reflectivity) site exists. If such an inclination θ is adjusted based on a certain adaptive delay time distribution, focusing (focusing) is performed on a high echo portion, and the beam is passed in a direction deviated from the original ultrasonic beam direction. Will be. Therefore, it can be said that the estimated value of the medium sound velocity in the region where the slope θ is the delay time distribution after the correction is large has low probability.

On the other hand, it can be said that the greater the strength A of the received signal, the higher the certainty. Also, it can be said that the likelihood of the large dispersion width d of the adaptive delay time obtained for each received signal is low. Note that the dispersion width d may be an absolute value of a difference between the adaptive delay time distribution and the delay time distribution at the time of setting. From the above, the evaluation function K of the above equation (1) for each region
Is determined, and the sound velocity of the medium corresponding to the adaptive delay time distribution in the region where K is the largest is evaluated as being most likely.

Here, if the evaluation of the estimated medium sound velocity value of the highest evaluation does not reach a certain criterion, the set delay time of each area is determined based on the estimated medium sound velocity of each area, and the ultrasonic measurement is performed. Is preferably repeated. For example, a threshold value Kth is set, and the process is repeated until the evaluation function K exceeds the threshold value Kth. It should be noted that a certain limit number of times can be set for this repetition.

An embodiment for selecting the most probable estimated value of the sound velocity of the medium based on the above concept and the procedure shown in FIG. 5 will be described. First, in step S1, ultrasonic measurement is started for a plurality of regions (beam direction, depth), and adaptive delay time distribution data is collected. Based on the collected data, in step S2, an evaluation function K for a plurality of areas is calculated in accordance with equation (1). Then, in step S3, the largest evaluation function Kmax is selected,
Based on this, the sound velocity of the medium is estimated by the above-described method. Next, in step S4, the selected evaluation function Kmax is selected.
Is greater than a threshold value Kth, that is, Kth <Km
ax is determined. If this determination is affirmative, the process proceeds to step S5, where the estimated medium sound velocity value corresponding to the evaluation function Kmax is sent to the digital delay control unit 25. This allows
The digital delay control unit 25 recalculates the delay time data based on the estimated sound velocity of the medium and feeds it back to the digital delay unit 21 to form an image.

On the other hand, if the determination in step S4 is negative, the process proceeds to step S6, where the imaging process is performed in the same manner as in step S5. Then, the process returns to the measurement and repeats until Kth <Kmax is satisfied. The number of repetitions is preferably set to a predetermined upper limit number. If the number of repetitions exceeds the predetermined number, it is preferable to return to the initial set sound velocity, for example, and output the fact to the display unit 11.

The evaluation procedure shown in FIG. 6 can be replaced with the evaluation procedure shown in FIG. In this procedure, the estimated medium sound velocity may vary greatly depending on the measurement. Therefore, when an estimated value of the impossible medium sound velocity is obtained, the sound velocity (v) and the evaluation items (A, d, θ) of the evaluation function are obtained. Is set to an upper limit or a lower limit, and if the value deviates from the evaluation, the accuracy of estimation of the medium sound velocity is improved. For example, the lower limit AL of the signal strength, the upper limit dH of the dispersion width d, the upper limit θH of the slope θ of the delay time distribution are set, and the lower limit vL and the upper limit vH of the medium sound velocity are set. Then, for example, in step S11, an evaluation function K that satisfies the conditions of AL <A, d <dH, and θ <θH is extracted. Then, an estimated value of the sound velocity of the medium is calculated based on this (S3). Next, in step S12, an evaluation function K that satisfies the condition vL <v <vH is extracted, and is connected to step S4 in FIG. By doing so, the estimation accuracy can be further improved.

If an evaluation function that satisfies the conditions of the evaluation procedure in FIG. 6 cannot be extracted, that is, if convergence is not achieved even after repeated execution, step S13 or step S14 is performed.
, The coefficients α, β, γ of the evaluation function and the upper and lower limit values AL,
The measurement can be repeated by changing dH, θH, and sound speed ranges vL, vH.

It is desirable to adjust the coefficient of the evaluation function and the upper and lower limits according to other factors, for example, the probe, the observation site, and the disease. For example, superficial sites such as the thyroid gland,
This is because the expected sound speed range, signal strength, and delay time accuracy differ between cirrhosis, fatty liver, and the like. Further, since the probe is generally determined depending on the observation site, the coefficient of the evaluation function and the upper and lower limits described above may be determined for each probe.

The change and adjustment of these judgment conditions can be further optimized by fuzzy inference or artificial intelligence. In particular, a measurement condition such as a probe, an observation site, and a disease is input, and when an image satisfying the user is obtained, the apparatus is made to recognize the determination condition. This automatically learns the evaluation coefficients, evaluation item thresholds, etc., corresponding to the probe, the observation site, and the disease, and assigns these judgment conditions to the next patient under the same conditions. It is possible to quickly shift to the optimum setting.

For example, if a patient has cirrhosis, cirrhosis generally has a higher sound speed than the sound speed set by a normal device. Also, if the cirrhosis is hardened as a whole, the attenuation of the intensity of the received signal is expected to be reduced. Therefore,
Set the range of sound velocity v to 1550m / s <v <1560m / s, and
Set L higher than usual. As a result, if the judgment condition is not satisfied, relax the condition of the item that does not satisfy,
Change in the direction expected for the disease. For example, 1550m / s <
Change to v <1600 m / s and reduce the coefficient α. When the evaluation converges due to this change and the operator determines that the condition is good, the apparatus is made to recognize those conditions. As a result, when a similar patient becomes the subject again, the knowledge of reducing α or increasing the sound speed condition can be acquired by learning as knowledge for converging the evaluation. As a result, it is possible to quickly adjust to optimal conditions.

As described above, according to the above embodiment, the ultrasonic measurement is performed on the actual subject, and the error between the set sound speed and the actual medium sound speed is determined based on the plurality of phased received signals. Since the estimated sound velocity is estimated and corrected based on the error, adaptive measurement can be realized by a simple operation.

Also, a representative medium sound velocity is selected from among the estimated medium sound velocity values obtained for all or a plurality of areas, and a single medium sound velocity common to each area is set. Therefore, adaptive adjustment of the sound velocity of the medium is simple, and sharp phasing can be performed over those regions, so that an image with uniform image quality can be obtained.

In the above embodiment, the delay error estimator 22
The method of estimating the delay time error by detecting the phase difference between the received signals by taking the cross-correlation of the received signals between adjacent channels has been described. However, the present invention is not limited to this. May be applied. For example, a method can be applied in which the reception signal after phasing between adjacent channels is complex multiplied by the reception center frequency to extract only the difference frequency component, and the real and imaginary parts are divided to obtain a phase difference from tan θ. Further, a method of setting a region of interest in a display image, and converging while varying the delay time of each channel so as to maximize the signal strength or the histogram of the region can be applied.

Further, the sound velocity of the medium is estimated and the delay data is recreated to form an image. Thereafter, the delay error estimating unit 22 has information on the delay time error remeasured based on the corrected delay time. When the delay error is corrected by adding the delay error of each element in the attention area to the delay time at the estimated high speed to form an image by phasing, the average sound velocity is corrected as a whole to improve the image. Then, the quality of the image of the attention area can be further improved.

The estimated value of the medium sound speed estimated by the medium sound speed selection unit 24 may be displayed on the display unit 11. Further, in the above embodiment, the example of the transducer in the one-dimensional array is used for the ultrasonic probe 1; however, the present invention is not limited to this, and a two-dimensional image using a ring array or a two-dimensional array transducer may be used. The present invention can also be applied to an apparatus for forming a three-dimensional image. Further, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist of the present invention.

[0053]

As described above, according to the present invention, the set sound speed used in the phasing process can be automatically adjusted to a value equal to or close to the actual medium sound speed. Measurement becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a wave receiving and phasing unit according to the present invention.

FIG. 2 is a block diagram of an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 3 is a diagram illustrating detailed functions of a digital delay unit and a delay error estimating unit in FIG. 1;

FIG. 4 is a diagram illustrating an example of an adaptive delay time distribution.

FIG. 5 is a flowchart illustrating an embodiment of a processing procedure for selecting a medium sound velocity representing a plurality of regions.

FIG. 6 is a flowchart showing another embodiment of a processing procedure for selecting a medium sound velocity representing a plurality of regions.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ultrasonic probe 2 aperture selection switch 5 transmission phasing circuit 7 analog-to-digital converter 8 reception phasing section 21 digital delay section 22 delay time estimation section 23 delay time comparison section 24 medium sound velocity selection section 25 digital delay control section 26 Reference delay time recording unit 27 Reference medium sound velocity recording unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C301 DD12 EE07 EE11 EE13 EE14 HH24 HH33 JB03 JB19 JB28 KK30 LL05 5J083 AA02 AB17 AC08 AC28 AD04 AE10 AF01 BC13 BE08 BE53 BE60 EA08 EA14 EA18

Claims (4)

[Claims] An ultrasonic wave transmitted into a subject from a plurality of arranged transducers is received by each of the transducers, and the received plurality of received signals are transmitted to a medium of the subject. A phase delay is performed based on a set sound speed determined corresponding to the phase difference, an error between the set sound speed and the actual medium sound speed is estimated based on the plurality of phased received signals, and based on the estimated error. Performing a process of estimating the medium sound velocity by using a plurality of measurement regions of the subject, evaluating the likelihood of the plurality of estimated values of the medium sound speed obtained for each measurement region, and estimating the highest evaluated medium sound speed. A phasing method for transmitting and receiving waves, wherein a value is set as a common set sound speed for the plurality of regions. 2. When the evaluation of the highest estimated medium sound velocity value does not reach a certain criterion, the set delay time of each measurement area is determined based on the medium sound velocity estimation value of each measurement area. The method of claim 1, wherein the sound wave measurement is repeated. 3. A probe in which a plurality of transducers for transmitting and receiving ultrasonic waves to and from a subject are arranged, and a transmission signal supplied to each transducer of the probe is transmitted to a medium of the subject. A transmission phasing means for delaying and outputting the received signals based on the set sound speed determined correspondingly, and a reception and phasing means for delaying and outputting the received signals output from the respective vibrators based on the set delay time. An ultrasonic diagnostic apparatus comprising: a wave phasing unit; and an image processing unit that generates an image based on a reception signal output from the wave phasing unit and causes the image display unit to display the image. A phase delay unit configured to delay the plurality of received signals based on the set delay time and output the delayed signals; and a method of detecting the subject based on the plurality of received signals output from the signal delay unit. Medium sound velocity estimating means for obtaining a medium sound velocity estimated value; The likelihood is evaluated for the plurality of estimated medium sound speeds obtained for the plurality of measurement regions of the subject, and the highest estimated medium sound speed estimated value is selected and set as a common set sound speed for the plurality of measurement regions. An ultrasonic diagnostic apparatus comprising: a representative sound velocity selecting unit. 4. The medium sound velocity estimating means includes: an error estimating means for estimating delay errors of the plurality of received signals output from the signal delay means; and a plurality of medium sound velocities and a plurality of medium sound velocities corresponding to the respective medium sound velocities. Storage means for storing the reference delay time, and comparing means for selecting, from the storage means, the reference delay time that matches within a certain allowable range the adaptive delay time obtained by adding the estimated delay error to the set delay time, 4. The ultrasonic diagnostic apparatus according to claim 3, further comprising: a medium sound speed selecting unit that obtains a medium sound speed corresponding to the selected reference delay time as a medium sound speed estimated value.