JP2008149153A - Doppler ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide doppler ultrasonic diagnostic apparatus which removes a clutter component sufficiently and certainly, and detects a blood flow at a great slow rate simultaneously regardless of the movement amount of a parenchyma organ even in the situation that influence of the signal value of a blood flow component cannot be ignored as compared with the clutter component. <P>SOLUTION: Doppler ultrasonic diagnostic apparatus has a decision means to decide information about the elimination of a clutter component using a doppler signal which removes large fluctuations in a signal component time-serially by a pretreatment means 45j in advance. Cross-sectional blood flow information of a subject is extracted using the doppler signal which removes the clutter component from the doppler signal based on the information and is obtained. The decision means is equipped with a phase estimation means to estimate momentary phase variation amount of the clutter component included in the doppler signal processed by the pretreatment means. Clutter component removal means 45c-d, 45g, 45i are equipped with a phase correction means 45c which corrects the phase of each doppler data of the doppler signal from the phase variation amount estimated by the phase estimation means 45a-b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to ultrasonic Doppler imaging that uses the ultrasonic Doppler method to obtain dynamic information of blood flow in a living body, and in particular, removes echo components (clutter components) reflected by an organ such as a moving myocardium. The present invention relates to an ultrasonic Doppler diagnostic apparatus that improves blood flow information detection accuracy and rendering ability.

  The ultrasonic Doppler method is a technique for obtaining blood flow dynamics information in a subject mainly non-invasively from outside the body using the Doppler effect of an ultrasonic signal. Has made remarkable progress.

  As one type of this ultrasonic diagnostic apparatus, in addition to the B-mode imaging method, a CFM (color flow mapping) mode for performing color Doppler tomography and a PW mode for performing pulse Doppler method for obtaining blood flow information 2. Description of the Related Art An ultrasonic Doppler diagnostic apparatus having an imaging function is known. CFM mode imaging uses the technology of MTI (moving target indicating device) used in the radar field, and can obtain a two-dimensional blood flow velocity distribution image of a tomographic plane. Further, according to the imaging in the PW mode, blood flow information at one point on the tomographic plane can be obtained.

  A reflected echo from the living body obtained by transmitting an ultrasonic signal into the living body via the ultrasonic probe is received by the ultrasonic probe. The reception signal output from this probe is sent to the reception circuit. In the reception circuit, the reception signal is amplified for each reception channel, and a delay time for focusing is given and added.

  In the B-mode processing system, the output signal phased and added by the receiving circuit is logarithmically amplified by a logarithmic amplifier, envelope-detected, and further converted into a digital signal. This digital echo signal is held in the image memory of the display system.

  In the CFM mode processing system, the echo signal from the receiving circuit is quadrature detected by the quadrature detector. That is, the echo signal is multiplied between two reference signals having substantially the same frequency as the ultrasonic frequency and having a phase difference of 90 degrees from each other, and these multiplication outputs are LPFs from which high frequency components are respectively removed. , And extracted as a 2-channel baseband Doppler signal corresponding to the real part and the imaginary part. The baseband Doppler signal is converted into a digital signal by an A / D converter for each channel, and then temporarily stored in the buffer memory.

  In this CFM mode, transmission / reception of ultrasonic pulses is repeated N times (for example, 16 times) in the same scanning line direction. Therefore, the digital amount of Doppler data necessary for reconstructing one image has the first dimension, the second dimension, and the second dimension for each of the real part and imaginary part signals, as shown in FIG. It becomes three-dimensional data consisting of three dimensions, and this is stored in the buffer memory of the MTI filter. The first dimension represents the number (number) of each scan line, the second dimension represents the number of pixels (number) in the depth direction along each scan line, and the third dimension represents the repetition of transmission and reception for each pixel. Represents the number (number) of Doppler data obtained by.

  For this reason, when focusing on the same pixel position in the scanning section, received echoes are obtained in time series by transmitting and receiving N ultrasonic pulses, and the digital data obtained by quadrature detection based on the received echoes is the third dimension. Are arranged in order. The change speed of the amplitude of the Doppler data when viewed in the direction of the third dimension corresponds to the magnitude of the Doppler shift frequency, that is, the magnitude of the moving speed of the object.

  The clutter component of the three-dimensional digital data (Doppler signal) formed in the buffer memory of the MTI filter in this way is removed for each data string in the third dimension direction at each pixel position. This filtering principle is as follows.

  In the received echo, an echo signal from a moving body that moves at a certain speed or more, such as a blood cell, and an echo signal (referred to as a clutter component) from a tissue that does not move so much such as a real organ are mixed. Generally, regarding the signal intensity, the clutter component is larger than the echo signal from the blood flow (usually about 40 dB to 80 dB). However, regarding the moving speed, the echo signal from the bloodstream is larger than the clutter component. That is, the reflected signal from an object that does not move so much, such as a real organ, does not change much in phase with respect to the reference signal of the received echo even after repeated transmission and reception, so that the amplitude of the N digital data strings does not change much, It has only a frequency near DC. On the other hand, the reflected signal from an object moving at a certain speed, such as a blood cell, changes greatly in phase with the reference signal every time transmission / reception is repeated, so that the amplitude change of the N digital data strings is fast. The frequency is high. Therefore, the filter circuit of the MTI filter is configured as a high-pass filter, and the cutoff frequency is set to a value that can remove the clutter component. Thereby, the clutter component is removed from the detected Doppler signal, and an echo signal from the blood flow is extracted.

  This echo signal is then subjected to a blood flow motion state (blood flow velocity, power, variance, etc.) estimation process, and the estimated information is stored in the image memory of the display system. As a result, the two-dimensional velocity distribution color image is superimposed on the black and white background image obtained by the B-mode processing system and displayed in color on the monitor.

On the other hand, the PW mode processing system generally uses two-channel baseband signals corresponding to the real part and the imaginary part obtained by the quadrature detection circuit in the CFM mode processing system. Specifically, only a signal in a time interval corresponding to a desired depth is extracted from each baseband signal by a range gate circuit, and this extracted signal is integrated to improve the S / N ratio. This integrated signal is further passed through a high-pass filter to remove clutter components and detect blood flow components. This blood flow component signal is converted into a digital quantity, and then subjected to estimation of blood flow information in an arithmetic circuit that performs, for example, FFT processing. As a result, a blood flow power spectrum at a desired position on the cross section is calculated. This power spectrum data is sent to the image memory of the display system, and is displayed on the monitor as a spectrum image of the blood flow velocity in real time through display preparation here.
JP-A-9-193966

  As described above, the MTI filter is used for removing the clutter component. However, since the actual organ actually moves or may move slightly due to various causes, such a clutter component and particularly a low-speed blood sample are used. There is a problem that the echo signal from the stream cannot be clearly distinguished, and the conventional MTI filter has a problem that the clutter component cannot be accurately and sufficiently removed satisfactorily.

  The parenchymal organs are (1) heartbeat (particularly problematic when examining blood flow in the heart), (2) movements of surrounding organs caused by shaking of the heart, (3 It may or may not move due to movements (body movements) caused by the subject's breathing, and (4) movements caused by hand movements of the operator.

  For this reason, when the cutoff frequency of the MTI filter is set low as shown in FIG. 2A, the clutter component cannot be sufficiently removed, and the clutter component remains in the detection signal (see the hatched portion A in FIG. 2). In this case, since the clutter component is integrated into the image of the eyelid being examined as blood flow motion information, the blood flow motion information is inaccurate and may cause misdiagnosis.

  On the other hand, as shown in FIG. 2B, when the cutoff frequency of the MTI filter is set high, the clutter component can be accurately removed, but at the same time, part or most of the echo signal from the bloodstream is also removed ( (See shaded area B in the figure). In particular, blood flow with a low motion speed may disappear from the screen, and the purpose of diagnosis cannot be achieved.

  In this way, there are conflicting requirements for the blocking characteristics for the removal of clutter components and the extraction of echo signals from the bloodstream. In addition, the blood flow velocity varies depending on the diagnosis site and individual differences. For this reason, the cutoff frequency of the MTI filter inevitably has to be set to a compromise value, so that it is difficult to obtain a sufficient effect of reducing the clutter component in the past, and at the same time blood that moves at a low speed. There was a problem that we had to accept a low flow detection state.

  With the intention of solving this problem and improving blood flow rendering ability, the present inventors have proposed an ultrasonic diagnostic apparatus (hereinafter referred to as JP-A-9-193966) (Japanese Patent Application No. 8-26085). Have already been proposed). The purpose of this apparatus is to be able to sufficiently remove clutter components regardless of the amount of movement of the real organ, and to simultaneously detect a blood flow with a very low velocity. In order to achieve this object, the apparatus proposed in the prior application is generally characterized by performing the following three processes for each pixel of an image.

[1] First, an instantaneous phase change between the data constituting the clutter component is estimated, and the phase change of the Doppler signal is corrected according to the instantaneous phase change amount.
[2] After the correction process described in [1], a constant value corresponding to the clutter component is subtracted.
[3] Further, a high-pass filter is provided in the subsequent stage of the circuit that performs the processing of [1] or [2], and the filtering characteristic is determined according to the characteristics of the output signal after subtraction of the constant value of [2]. Control.

  In order to make the explanation easy to understand, paying attention to N digital data strings (referred to as “Doppler signals” as necessary) at a certain point (pixel) in space, the processing in the items [1] to [3] An outline will be described.

This Doppler signal is composed of N discrete Doppler data. The Doppler signal can be described as follows by dividing it into a Doppler component (clutter component) from the real organ and a Doppler component (blood flow component) from the bloodstream. it can.
[Equation 1]
Zi = A · exp {j · (φi + φ0)} + a · exp {j · (ψi + ψ0)}
...... (1)
In this equation, the first term represents the clutter component, and the second term represents the blood flow component. The subscript i means the data number (0 to N-1) in the data string. φ0 and ψ0 each represent an initial phase based on the first data, and φi and ψi each represent a phase difference of the i-th data with respect to the 0th (first) data. A and a each represent an amplitude component.

In the above items [1] and [2], in order to remove the clutter component included in the Doppler signal, the following is applied to the Doppler signal Zi (i = 0, 1, 2,..., N−1). In this way, processing that combines phase correction operation and constant value subtraction is performed.
[Equation 2]
Zi · exp {−j · (φi)} − A · exp {j · (φ0)}
= A · exp [j · {(ψi−φi) + φ0}] (2)

  By executing this process, in an ideal case, the clutter component is removed and only the blood flow component can be obtained.

In order to perform the ideal processing shown in Expression (2), it is necessary to estimate the phase term φi of the clutter component more accurately. Therefore, in this "prior application proposed apparatus", in order to capture the instantaneous phase change amount of the clutter component, instead of the average phase change amount over the entire observation period of N data, for example, the following equation As shown in (3), the average phase change amount in a minute time interval (time width is 2k + 1) is calculated. In this example, the average minute section width is gradually narrowed at the ends of the N data strings, and the phase change amount can also be estimated at these ends.

Using the instantaneous phase correction amount θi between the data in the data string estimated in this way, an operation for removing the clutter component is performed according to the following equation (4).
[Equation 4]
Zi · exp {−j (θ ₁ + θ ₂ +... + Θ _i−1 )} − A ^* exp {j ^* (φ0)}
...... (4)

  FIGS. 3B and 3C show an example of the result of the clutter component removal operation as an imaginary I component (or real Q component). FIG. 5B shows a case where only phase correction for correcting an instantaneous phase change is performed, and the waveform of the I component data string has a substantially constant value. FIG. 10C is a waveform obtained by subtracting a constant value (amplitude value of the first data) corresponding to the clutter component from the waveform of FIG. 10B, and as a result, the clutter component is substantially removed. .

  In equation (4), the constant value subtraction represented by the second term is performed for the purpose of removing the clutter component. However, as in the feature [3], the high-pass filter processing is performed in the subsequent stage. In this case, constant value subtraction is not always necessary. However, as will be described later, when the cutoff characteristic of the high-pass filter is changed according to the property of the Doppler signal, the processing result including the constant value subtraction of Expression (4) is used as information for grasping the property of the Doppler signal. ing.

  FIG. 3C illustrates an ideal state where the clutter component is completely removed and only the Doppler signal from the blood flow having a higher frequency than the clutter component remains. However, even if the instantaneous phase change amount of the clutter component is estimated using only a few nearby data, there is a limit to the estimation accuracy, and the clutter component can be completely removed only by the processing shown in Equation (4). Is impossible.

  In view of this, the apparatus proposed in the prior application is configured to further reduce clutter components that could not be removed by the processing of Expression (4) using a high-pass filter. That is, the characteristics of the high-pass filter are changed according to the characteristics of the Doppler signal after subtraction of a certain value. Specifically, as illustrated in FIG. 4, as the power value of the signal is larger, it is determined that the removal of the clutter component based on Expression (4) is not sufficient, and the cutoff frequency of the high-pass filter is increased, As shown in FIG. 5, not only the cutoff frequency but also the order of the filter is increased in accordance with the increase in the signal power value, and the attenuation characteristic is controlled to be steeper.

  Further, the Doppler signal (blood flow component) formed by the blood flow undergoes a phase shift by the phase change amount φi of the clutter component as shown in the equation (2). If the phase value after this phase shift is used as it is, the blood flow velocity relative to the clutter component can be obtained. However, the blood flow velocity provided by normal CFM processing is relative to the ultrasound probe, not the true blood flow velocity. It is natural that the true blood flow velocity is a relative velocity of the blood flow to the real organ. From this point of view, it can be said that the blood flow velocity obtained as described above in the device proposed in the prior application is the true blood flow velocity.

However, in the device proposed in the prior application, when it is desired to obtain the blood flow velocity for the ultrasonic probe in accordance with the conventional practice, the phase correction amount used in Equation (4) is inverted and processed as in the following equation. It also makes it possible.
Si · exp {+ j (θ ₁ + θ ₂ + …… + θ _i-1 )} (5)
Here, Si represents the Doppler signal after passing through the Haspass filter.

  By performing this operation, the relative velocity of the blood flow with respect to the ultrasonic probe can be obtained.

  As described above, the device proposed in the prior application is effective to a certain extent in removing the clutter component and improving the ability to depict blood flow, but it is particularly sufficient for recent diversified diagnostic methods and diagnostic sites. However, there was an unsolved problem. The unresolved problem is as follows.

[Unresolved issue (A)
The above-mentioned device proposed by the prior application is based on the premise that the clutter component signal value is very large compared to the blood flow component, and A (clutter component signal value) >> a (blood flow component signal value). As shown in Equation (3), the clutter component of the first term is to be estimated using the Doppler signal Zi itself of Equation (1). This premise is considered to be valid in most parts of the living body except for the heart chamber. However, in the case of a vascular system that is sufficiently larger than the transmission / reception beam width of the ultrasound, such as in the heart chamber, Furthermore, it cannot be said that A >> a.

  Furthermore, in the case of contrast echography in which an ultrasound contrast agent that has been actively studied in recent years is injected into a living body, the scattered component from the bloodstream is enhanced, and the signal value a of the Doppler signal (bloodstream component) from the bloodstream is increased. It becomes relatively large. In this case, the influence of the blood flow component cannot be ignored. That is, originally, it is desired to obtain the phase change amount θi reflecting only the clutter component, but in the case of this contrast agent injection, the influence of the blood flow component on the phase change amount θi becomes large, and the estimated phase difference The error of θi increases. As a result, the phase correction operation is not in an ideal state, and the effect of removing the clutter component is halved. As an extreme example, if a case where A << a occurs, the phase correction operation is effective to remove the blood flow component instead of the clutter component, and the intended purpose is achieved. You will not get.

In order to overcome such a situation, the apparatus proposed in the prior application applies a correction shown in the following equation (6) to the phase correction amount θi obtained in equation (3) according to the power value of the Doppler signal. Has been proposed.
[Equation 6]
θi · k (p) i (6)
Here, p is the power value of the input Doppler signal.

  The coefficient k (p) i in this equation is the content of the correction process, and an example is shown in FIG. Although the phase correction amount is not changed at a site where the clutter component is very large such as outside the blood vessel, the coefficient applied to the phase correction amount is reduced as the input Doppler signal becomes smaller as it enters the blood vessel. . Thus, as in the case of the blood vessel center shown in FIG. 7, when the clutter component is small and the phase correction amount is greatly influenced by the blood flow velocity, the coefficient k (p) i is decreased to make the phase correction not so large. It is to suppress.

  However, the multiplication of the coefficient k (p) i is effective on the premise that the absolute value of the power of the blood flow component is not so large. That is, it is not assumed that the contrast medium is administered and the blood flow component is enhanced. In such an enhanced state, the value of the coefficient k (p) i increases, and θi that is greatly affected by the blood flow component is output, so that the clutter component removal effect is reduced. When the enhancement effect by the contrast agent is very large, there is a possibility that the processing is performed to remove the blood flow component opposite to the clutter component instead of the clutter component.

  Further, in the case of the device proposed in the prior application, it is determined that the larger the signal power value after subtraction of a certain value is, the larger the clutter component remaining after the processing of Equation (4) is, and the cutoff characteristic of the high-pass filter is sharply controlled Like to do. The signal power value of the determination criterion is based on the premise that the clutter component included in the signal is dominant. Therefore, as described above, assuming that the blood flow component is enhanced by administration of the contrast agent, the signal power value increases as the blood flow component is enhanced, and the high-pass filter contains more components. Works to remove. Therefore, a contradiction arises that blood flow components are also removed.

[Unresolved issue (B)
There is also an unresolved problem related to the cutoff frequency of the high-pass filter. In the apparatus proposed in the prior application, a high-pass filter is used as the clutter removal means when the clutter component remaining after the processing of Expression (4) is large, and the cutoff frequency is controlled to be high.

  However, when observing relatively slow blood flow such as abdominal blood flow, using a small speed range may cause a situation in which the residual clutter component has a relatively large speed due to the influence of the heart and respiration. is there. In that case, in order to reduce the clutter component, it is necessary to set the cutoff frequency of the high-pass filter to a very large value. On the other hand, depending on the diagnosis site, the clutter component hardly fluctuates and a small cutoff frequency may be sufficient. That is, even in the same image, a situation can occur in which the cutoff frequency value required for the high-pass filter differs greatly.

  The average velocity value obtained by autocorrelation processing of the Doppler signal after passing through the high-pass filter tends to increase as the cutoff frequency of the high-pass filter increases. For this reason, when observing the average speed, there is a possibility that speed unevenness depending on the magnitude of the clutter component occurs in the same image. In order to reduce this influence, it is desirable to narrow the variable range of the cut-off frequency of the high-pass filter, and in particular to lower the upper limit value of the cut-off frequency. However, when such a setting is made, there is a situation in which the removal effect on the remaining clutter with a high speed is limited.

[Unresolved issue (C)
Furthermore, there is an unsolved problem regarding the determination of the size of the clutter component. In the case of the above-mentioned device proposed by the prior application, the power value of the signal after subtraction of a constant value is used as an index for judging the degree of the clutter component remaining after performing the processing of equation (4).

  However, this signal power value changes according to the attenuation characteristics of the living body and the distribution of structures in the living body, and does not always take a uniform value. For example, even when a uniform organ is observed in a relatively large region such as the liver, the average power value tends to be smaller in the deeper part due to the influence of biological attenuation. Therefore, if the magnitude of the clutter component is simply determined based on the absolute value of the power, it is erroneously determined that the shallow portion and the deep portion always have a relatively larger amount of the clutter component in the shallow portion than in the deep portion. There was a fear.

[Unresolved issue (D)
Furthermore, there is an unresolved problem regarding the difference in blood flow velocity between the CFM mode and the PW mode. In the case of CFM mode imaging performed by the apparatus proposed in the earlier application, the Doppler signal from the blood flow undergoes a phase shift by the phase change amount φi of the clutter component as shown in Equation (2). If the phase value after this phase shift is used as it is, the blood flow velocity relative to the clutter component is given as the CFM mode instead of the blood flow velocity for the ultrasonic probe according to the conventional practice.

  On the other hand, the mainstream of conventional ultrasonic diagnostic apparatuses that provide blood flow information is a type having both CFM mode and PW mode mechanisms as described above.

  Accordingly, when the influence of the clutter component speed cannot be ignored due to the slow blood flow speed such as the abdominal blood flow, the blood flow speed provided to the CFM mode in the device proposed in the prior application is There is an inconvenience that an error corresponding to the speed of the clutter component occurs with respect to the blood flow speed provided for the conventional PW mode (as long as the PW mode according to the conventional practice is used).

  As described above, since there are various unsolved problems even with the above-mentioned device proposed by the prior application, the present invention solves the above-mentioned problems of the conventional MTI filter as well as the above-mentioned prior application proposal. The purpose is to solve both unresolved and unsolved problems.

  Specifically, the present invention reliably and precisely separates the clutter component and the echo component from the low-speed blood flow to reliably remove the clutter component from the moving real organ, Furthermore, on the premise of providing an ultrasonic Doppler diagnostic apparatus capable of detecting a very low-speed blood flow without overlooking it and generating a blood flow image having a high detection ability and a two-dimensional distribution, the following objects are achieved. Is.

  A first object of the present invention is to image a vascular system such as a heart chamber sufficiently larger than the transmission / reception beam width of an ultrasonic wave, or to image a vascular system in which a contrast medium is injected into a living body. Even in imaging situations where the influence of the signal value of the blood flow component cannot be ignored compared to the component, the clutter component can be removed sufficiently and reliably regardless of the amount of movement of the real organ, It is to be able to detect blood flow with very low velocity at the same time.

  The second object of the present invention is to increase the speed of the high-pass filter without unnecessarily increasing the cutoff frequency even when the clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal processing is large. It is to ensure that large residual clutter components can be reduced.

  The third object of the present invention is that the feature quantity of the signal for judging the magnitude of the clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal processing is not affected by the influence of biological attenuation or the like. Even when the power values are not uniformly distributed, it is possible to determine the size of the same component that reliably reflects the size of the clutter component, and to obtain a reliable and highly accurate clutter removal effect.

  A fourth object of the present invention is an ultrasonic Doppler diagnostic apparatus that provides a blood flow velocity relative to a clutter component, and eliminates a difference in blood flow velocity provided by both CFM mode and PW mode mechanisms. It is to be.

A (1): Means for Achieving First Objective The problem (A) is that the Doppler component (blood flow component) from the blood flow included in the entire Doppler signal is compared to the Doppler component (clutter component) from the clutter. This happens when it can no longer be ignored. Therefore, a means for surely removing the influence of the blood flow component contained in the entire Doppler signal is constructed, and the instantaneous phase change amount θi according to the expression (3) is estimated using this means, and further, the expression (4) Thus, phase correction and clutter removal processing based on the instantaneous phase change amount θi is performed, and thereafter, the magnitude of the remaining clutter component is determined.

Focusing on the average velocity of blood flow and clutter components, the difference is generally
Clutter component <blood flow component. In the CFM method and the PW method, a clutter component is removed from the entire Doppler signal by a high-pass filter using this speed difference, and a blood flow component is extracted.

[Improved phase estimation]
As can be seen from this speed difference, it is reasonable to assume that the amount of phase change of the Doppler signal due to the clutter component is not so large. Therefore, as illustrated in FIG. 8, an upper limit value θmax is set in advance for the estimated value (ie, phase correction amount) θi of the phase change amount, and the estimated value θi estimated by Expression (3) is greater than or equal to the upper limit value θmax. If it is, it is determined that the influence of the blood flow component is large, and the output is clipped at the upper limit value θmax.

  For example, as illustrated in FIGS. 9B and 9C, this clip processing is a case where the influence of the blood flow component on the estimated value θi of the phase change amount is large, and the estimated value θi is deduced from the ideal value θcl. Even when there is a large deviation, the actual estimated value θact = + φmax is suppressed, so that the amount of deviation from the ideal value θcl can be reduced to an appropriate amount within the allowable range.

  Alternatively, by performing preprocessing using a low-pass filter on the Doppler signal, it is possible to reliably remove the blood flow component contained in the Doppler signal and reliably estimate the movement change amount of only the clutter component. . As schematically shown in FIGS. 10A to 10C, the low-pass filter functions effectively by matching the pass band of the low-pass filter with the clutter component.

  If the cutoff characteristic of the low-pass filter is made to be matched only with the clutter component and its cutoff characteristic is made steep, generally, the flatness of the phase characteristic of the pass band tends to be broken. This is not preferable for the present invention, which is based on performing phase correction using an instantaneous phase change amount, to ensure the accuracy of estimation of the phase change amount. That is, even when a low-pass filter is used, there is a certain limit to the steepness of the cutoff characteristic of the filter.

  Therefore, it is preferable to use this low-pass filter in combination with the above-described clip processing depending on the situation. For example, as shown in FIG. 10D, such a combination is used at the time of phase estimation, particularly in a specific situation where the blood flow component is very large compared to the clutter component, such as a large blood vessel under contrast medium administration. It is desirable to function as a safety valve.

  Further, the filtering process of the low-pass filter also functions to cause the correction process of the phase correction θi according to the signal power value based on the above formula (6) to function as originally intended. That is, if the blood flow component is somewhat removed by the low-pass filter, the power value used for such correction processing reflects the clutter component more strongly.

  Moreover, if the correction process of the phase correction amount based on the signal power value is used in combination with the filtering process by the low-pass filter, it is effective in complementing the performance limit of the low-pass filter as described below.

  The cut-off frequency of the low-pass filter is desirably a minimum setting that can cover the clutter component. However, as shown in FIG. 11 (b), when observing the heart, the myocardium or valve serving as the clutter exhibits a relatively fast velocity component, and therefore the cutoff frequency cannot be set to a very small value. Similarly, the upper limit value of the phase correction amount cannot be made as small as the set value for the abdominal blood flow. For this reason, there is no problem when the blood flow component is fast as shown in FIG. On the other hand, as shown in FIG. 6A, when the blood flow component passes through the low-pass filter when it is slow, the upper limit of the low-pass filter and the phase correction amount (estimated phase change amount) is reached. Even if a measure against the value is taken, such a blood flow component is regarded as a clutter component and passes through the filter. Focusing on the signal power value, the power value of the blood flow component is not so large in a very general situation that is not a specific situation such as under contrast medium administration, and the correction of the phase correction amount based on the power value can function. . Therefore, by using the correction of the phase correction amount based on the power value together, even when the velocity of the blood flow component is slow as shown in FIG. As described above, when the low-pass filter and the correction processing of the phase correction amount based on the power value are used in combination, the low-speed blood flow component can be reliably detected while complementing each other's disadvantages and taking advantage of the advantages.

  As described above, the problem (A) is greatly improved by adopting “limiting the amount of phase correction” or “using a low-pass filter”, and by using them together, The target range of blood flow measurement is significantly expanded. Further, the problem (A) is greatly improved by using both “use of a low-pass filter” and “correction of the phase correction amount based on the power value”. Furthermore, it is also improved by using these three together.

[Improved determination of remaining clutter components]
In the present invention, the determination of the amount of the remaining clutter component after the phase correction of the Doppler signal based on the equation (4) and the removal of the clutter component is performed by the difference in the average speed as described above. It is improved by using. As preprocessing, the Doppler signal is filtered with a low-pass filter to remove blood flow components contained in the Doppler signal. Thereafter, a constant value corresponding to the clutter component is subtracted, and a signal resulting from the subtraction is judged to calculate a residual power value of the clutter component.

B (1): Means for Achieving the Second Objective Problem (B) is caused by the fact that there is a limit only by adjusting the cutoff characteristics of the high-pass filter, which is performed in order to remove the relatively fast speed component clutter component. is doing. Therefore, in the present invention, the clutter component is removed by using both the means for adjusting the gain of the Doppler signal and the adjustment of the cutoff characteristic of the high-pass filter.

  For the gain adjustment, it is desirable to use a power value that more accurately reflects the remaining amount of the clutter component after subtracting a constant value corresponding to the clutter component, as in the control of the filtering characteristics of the high-pass filter.

  FIG. 12 shows a control example of the cutoff frequency of the high-pass filter and the gain of the Doppler signal. The signal used as the basis for determining the remaining clutter component is a signal after subtraction of a constant value. Therefore, as shown in the figure, when the signal power after this constant value subtraction is large, it may be considered that the component included in the signal is substantially only the clutter component, so the gain is lowered. Gradually remove clutter components. Further, when the signal power value increases, the cutoff frequency of the high-pass filter is gradually increased. Both the cut-off frequency and the gain are kept constant in the low and high signal power values.

  If the power value after subtraction of a certain value exceeds a certain threshold value, it is possible to prevent such clutter from being displayed by simply blanking it. Since continuous points may be conspicuous, it is not preferable. Therefore, as shown in FIG. 12, the discontinuity can be reduced by continuously changing the gain in the intermediate region of the signal power value.

  In addition, when performing blood flow presence diagnosis using a mode that displays the power of blood flow components in the CFM mode, which is often referred to as “power mode”, the signal power after subtraction of a constant value as a criterion is sufficiently high. Even if there is a case that does not reflect only the clutter component and operates to lower the gain of the blood flow component, a certain amount of blood flow is displayed on the image. Compared to it, it is more effective.

  In this way, not only control of the cutoff frequency of the high-pass filter but also signal gain adjustment for the Doppler signal (blood flow component) can be used to sufficiently remove the clutter component without making the cutoff frequency too high. can do.

C (1): Means for Achieving the Third Objective Problem (C) is due to the fact that the absolute value of the signal power after subtraction of a constant value changes depending on the difference in the body part. Therefore, in the present invention, a measure is taken to absorb the difference depending on the part of the living body with respect to the absolute value of the signal power after subtraction of the constant value.

  Specifically, the signal power value after subtraction of the constant value is corrected with the signal power value before phase correction, thereby mitigating the influence of the difference depending on the part of the living body. The signal power value before the phase correction is directly derived from the original power of the clutter component, and is relatively large in the shallow living body where the attenuation is small, and on the contrary, takes a small eye value in the deep living body where the attenuation is large. If the signal power value (corresponding to the remaining clutter component) after subtracting a constant value by equation (4) is normalized with the signal power value before phase correction, the difference in the absolute value of the signal power due to the difference in the body part Is offset.

A preferred example of this normalization is to use the feature quantity sPow defined by the equation (7) as follows. cdsPow indicates the signal power after subtraction of a constant value, and inPow indicates the signal power before phase correction.
[Equation 7]
sPow = (cdsPow) ^β / inPow (7)
In this equation, β represents the weight of signal power after subtraction of a constant value reflecting the amount of remaining clutter component.

The power value of each signal is defined using at least one data of N Doppler data strings Zi at each pixel position. As such a formula, for example, the following formula (8) which means an average value of N pieces of Doppler data can be used.

D (1): Means for Achieving the Fourth Objective Furthermore, the problem (D) is caused by the fact that the definition of the speed to be calculated and displayed differs between the CFM mode and the PW mode. Therefore, in the present invention, the definition of two types of velocity, the relative velocity of the blood flow with respect to the clutter component and the relative velocity of the blood flow with respect to the probe according to the conventional practice, is made to coincide between the CFM mode and the PW mode. To do. In particular, it is a preferable aspect that each of the circuits realizing the CFM mode and the PW mode includes a phase correction unit for obtaining a relative velocity of the blood flow with respect to the clutter component.

  In light of the above-described principle of solving the problem, the present invention is specifically configured as follows.

  As one aspect of the ultrasonic Doppler diagnostic apparatus according to the present invention, an ultrasonic signal is transmitted a plurality of times in the direction of each scanning line along the cross section in the subject and reflected from the subject. Transmission / reception means for receiving an echo signal and a Doppler signal composed of a plurality of time-series Doppler data reflected from the same spatial position in each scanning line direction based on the ultrasonic echo signal for each spatial position Doppler signal extraction means, preprocessing means for removing signal components having a large variation in time series from the Doppler signal, and the organ using the Doppler signal from which signal components have been removed by the preprocessing means Determination means for determining information related to removal of clutter components accompanying reflection of an ultrasonic signal, and removal of the clutter components from the Doppler signal based on the information And a blood flow information extracting means for extracting blood flow information of the cross section using the Doppler signal obtained by the removal of the clutter component removing means. Phase estimation means for estimating an instantaneous phase change amount of the clutter component included in the Doppler signal processed by the processing means, and the clutter component removal means is based on the phase change amount estimated by the phase estimation means. One important configuration is to include phase correction means for correcting the phase of each Doppler data of the Doppler signal.

  For this configuration, a visualization means for visualizing the blood flow information extracted by the blood flow information extraction means can be provided.

  Preferably, the preprocessing means is a low-pass filter, and the low-pass filter is a reflected ultrasonic component from a blood flow passing through the cross section as a frequency band for removing the signal component having a large variation in time series. Is set to a frequency band to eliminate

  Preferably, the clutter component removing unit may further include a subtracting unit that subtracts, for example, a constant value corresponding to the clutter component from each Doppler data of the Doppler signal phase-corrected by the phase correcting unit. Further, the phase estimation means uses the partial Doppler data in the Doppler data sequence including the Doppler data for performing phase correction in the Doppler data sequence forming the Doppler signal, and performs the instantaneous phase change. You may form in the means to estimate quantity. Further, the phase estimation means can include correction means for correcting the instantaneous phase change amount according to the power of the Doppler signal. Further, the phase estimation means may include clip processing means for clipping the absolute value of the phase change amount by a predetermined value.

  For example, the clutter component removing unit may include a high-pass filter that performs high-pass filtering on the Doppler signal from which a constant value has been subtracted by the subtracting unit. In this case, preferably, the determination unit includes another phase correction unit that corrects the phase of each Doppler data of the Doppler signal processed by the preprocessing unit using the instantaneous phase change amount, and Another constant value subtracting means for subtracting a constant value from each Doppler data of the phase-corrected Doppler signal, and a control means for controlling the characteristics of the high-pass filter using the Doppler signal before and after the constant value subtraction. It is. Further, in this configuration, the control means includes a first computing means for computing a power value of the Doppler signal processed by the preprocessing means, and the Doppler subtracted by a constant value by the another constant value subtracting means. Second computing means for computing a power value of a signal, third computing means for computing data for determining characteristics of the high-pass filter from both power values computed by the first and second computing means, Setting means for setting the characteristics of the high-pass filter according to data may be provided. For example, the third calculation means may include a power ratio “of a power value inPow of the Doppler signal calculated by the first calculation means and a power value cdsPow of the Doppler signal calculated by the second calculation means. “cdsPow / inPow” can be configured as means for calculating the data. The setting means is preferably means for setting at least one of a cutoff frequency or an order of the high-pass filter in accordance with the power ratio. The setting means may be means for holding the cutoff frequency at a high constant value when the power ratio is further increased.

  As a preferred example, the clutter component removing unit can include an amplifying unit that amplifies the Doppler signal subtracted by a constant value with a variable gain. More preferably, a gain setting means for variably setting the variable gain based on the power ratio calculated by the third calculation means is provided. The gain setting means is means for holding, for example, the variable gain at a lower constant value when the power ratio increases.

  Preferably, the determination unit includes a phase inversion unit that inverts the instantaneous phase change amount estimated by the phase estimation unit, and the clutter component removal unit is constant by the amount of the phase change amount inverted in phase. Phase cancellation means for returning the phase of the Doppler signal from which the value has been subtracted is provided.

  As an example, in the main configuration, the blood flow information extraction means includes a plurality of analysis means for analyzing the flow velocity of the blood flow using the Doppler signal, and the analysis means of each system are relative to each other having the same significance. It is also preferable to be a means for analyzing accurate blood flow velocity information. In this case, for example, the plurality of systems of analyzing means can include analyzing means for performing CFM mode signal processing of the blood flow and analyzing means for performing PW mode signal processing of the blood flow.

  As another aspect, the ultrasonic Doppler diagnostic apparatus according to the present invention transmits an ultrasonic signal multiple times in the direction of each scanning line along the cross section in the subject and reflects the ultrasonic echo reflected from the subject. A transmission / reception means for receiving a signal, and a Doppler signal for each of the spatial positions, which is composed of a plurality of time-series Doppler data reflected from the same spatial position in each scanning line direction based on the ultrasonic echo signal. A signal extraction unit; a determination unit that determines information related to removal of a clutter component when the organ reflects the ultrasound signal using the Doppler signal; and the clutter component is removed from the Doppler signal based on the information. A clutter component removing means including a high-pass filter that performs a gain processing on the Doppler signal, and a removal of the clutter component removing means. Blood flow information extracting means for extracting blood flow information of the cross section using the obtained Doppler signal; and visualization means for visualizing the blood flow information extracted by the blood flow information extracting means. The determining means includes phase estimating means for estimating an instantaneous phase change amount of the clutter component included in the Doppler signal, and the clutter component removing means is based on the phase change amount estimated by the phase estimating means. Another main configuration is to include phase correction means for correcting the phase of each Doppler data of the signal.

  The phase estimation means can estimate the instantaneous phase change amount using Doppler data included in a minute time interval in the Doppler data sequence forming the Doppler signal. As an example, the phase estimation means includes clip processing means for clipping the absolute value of the phase change amount by a predetermined value. In addition, the clutter component removing unit may include a subtracting unit that subtracts, for example, a constant value corresponding to the clutter component from each Doppler data of the Doppler signal phase-corrected by the phase correcting unit. Further, the determining means includes another phase correction means for correcting the phase of each Doppler data of the Doppler signal using the instantaneous phase change amount, and a fixed value from each Doppler data of the phase corrected Doppler signal. There may be provided another constant value subtracting means for subtracting and a control means for controlling the characteristics of the high-pass filter and gain processing circuit using the power value of the Doppler signal before and after the constant value subtraction.

  For the other main configuration, for example, the blood flow information extracting means includes a plurality of analysis means for analyzing the blood flow velocity using the Doppler signal, and the analysis means of each system have the same meaning. It is also preferable to be a means for analyzing such relative blood flow velocity information.

  According to the ultrasonic Doppler diagnostic apparatus according to the present invention, between the data of the Doppler signals that are substantially only the clutter component by removing the relatively high velocity blood flow component (Doppler signal component from the blood flow). By sequentially correcting the instantaneous phase change amount, the clutter component from the Doppler signal even when the influence of the blood flow component becomes larger than usual, as in the case of a large blood vessel system or a blood vessel system administered with a contrast agent. Can be removed reliably and sufficiently. This reliably prevents an undesirable situation in which the influence of clutter components appears in the displayed blood flow information, improves blood flow detection capability and display capability, and provides high accuracy blood flow information to the device user. be able to.

  In particular, the clutter component can be reliably removed regardless of the amount of movement of the parenchymal organ, and a blood flow with a very low velocity can also be reliably detected.

  In addition, even when there is a large amount of clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal process, the high-pass filter does not increase the cutoff frequency unnecessarily, and the high-speed residual clutter component is reliably detected. Can be reduced.

  In addition, the characteristic value of the signal that determines the magnitude of the clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal processing, the power value of the clutter component is uniformly distributed due to the influence of biological attenuation, etc. Even if it is not, it is possible to determine the size of the same component that reliably reflects the size of the clutter component, and to obtain a reliable and highly accurate clutter removal effect.

  Furthermore, the deviation of the significance of the blood flow velocity provided from both the CFM mode and the PW mode processing system is eliminated, and both the blood flow velocity relative to the clutter component or the blood flow velocity relative to the probe are both included. Can be provided, avoid unnecessary confusion for the user of the apparatus, and provide convenience.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
The ultrasonic Doppler diagnostic apparatus according to the first embodiment will be described with reference to FIGS.

  The ultrasonic Doppler diagnostic apparatus shown in FIG. 13 includes an ultrasonic probe 1 capable of bidirectional signal conversion between an ultrasonic signal and an electric signal, a transmission system circuit 2 connected to the ultrasonic probe 1, and reception / processing. The system circuit 3 is provided.

  The ultrasonic probe 1 includes an array-type piezoelectric vibrator disposed at the tip thereof. The array-type vibrator has a plurality of piezoelectric elements arranged in parallel, and the direction of the arrangement is a scanning direction, and each of the plurality of piezoelectric elements forms a transmission / reception channel.

  The transmission system circuit 2 includes a pulse generator 11 that generates a reference rate pulse, and a transmission circuit 12 that generates a drive pulse by delaying the reference rate pulse output from the pulse generator 11 for each channel. The drive pulse for each channel output from the transmission circuit 12 is supplied to each of the plurality of transducers of the ultrasonic probe 1. The transmission delay time of the drive pulse is controlled for each channel and is repeatedly supplied for each rate frequency. In response to the supply of the drive pulse, an ultrasonic pulse is emitted from each transducer. This ultrasonic pulse forms a transmission beam with a controlled transmission delay time while propagating through the subject, and a part of the ultrasonic pulse is reflected at an interface having different acoustic impedances to become an echo signal. Part or all of the returned echo signal is received by the transducer and converted into a corresponding electrical signal.

  On the other hand, the reception / processing system circuit 3 includes a reception circuit 21 connected to the ultrasonic probe 1, a B mode processing circuit 22, a CFM mode processing circuit 23, and a display circuit placed on the output side of the reception circuit 21. 24. The reception circuit 21 includes a preamplifier for each channel connected to the transducer of the probe 1, a delay circuit connected to each of the preamplifiers, and an adder that adds the delay outputs of the delay circuits. For this reason, the echo signal received by the probe 1 is subjected to delay control for reception focus and added after the analog signal of the corresponding electric quantity is taken into the receiving circuit 21 and amplified for each channel. As a result, a reception beam having a focus point determined according to the control of the reception delay time is formed in calculation, and desired directivity is obtained.

  The output terminal of the receiving circuit 21 is branched and connected to a B mode processing circuit 22 and a CFM mode processing circuit 23. The B-mode processing circuit 22 is responsible for creating B-mode black and white tomographic image data, and includes a logarithmic amplifier, an envelope detector, and an A / D converter (not shown). Therefore, the echo signal phased and added by the receiving circuit 21 is logarithmically amplified by the logarithmic amplifier, the envelope of the amplified signal is detected by the envelope detector, and further converted to a digital signal by the A / D converter. Is sent to the display system circuit 24 as a B-mode image signal.

  The display system circuit 24 includes a digital scan converter (DSC) 31 having a frame memory for B mode and a CFM, and a write / read control circuit, a color processor 32 for performing pixel color processing, and a D / A converter 33. And a TV monitor 34 for display. The digital envelope detection signal output from the B-mode processing circuit 22 is written in the B-mode frame memory of the DSC 31.

  On the other hand, the CFM processing circuit 23 is a circuit group responsible for creating CFM mode image data for observing blood flow dynamics, and the input side receives the echo signal output from the receiving circuit 21 as a real part Q and an imaginary part I. Are branched to input in two systems. For each signal system of the real part Q and the imaginary part I, a mixer 41A (41B), an LPF 42A (42B), and an A / D converter 43A (43B) are provided in this order. The CFM processing circuit 23 further includes buffer memories 44A and 44B that temporarily store the processing signals of the real part and the imaginary part from the A / D converters 43A and 43B, an MTI filter unit 45 that performs filtering processing based on the stored signal, And an arithmetic circuit 46 for performing various calculations relating to blood flow dynamics based on the output of the filter unit. The CFM processing circuit 23 further includes a reference oscillator 47 that oscillates a reference signal for reference, and a phase shifter 48 that gives a phase difference of exactly 90 degrees to the reference signal and supplies it to the mixers 41A and 41B. The reference oscillator 47 and the pulse generator 21 of the transmission system circuit 2 are driven in synchronization with each other. The reference signal has substantially the same frequency as the ultrasonic signal.

  For this reason, the echo signal output from the receiving circuit 21 is multiplied by the reference signal by the mixer 41A (41B) in each of the signal system of the real part and the imaginary part, and then the high frequency component by the LPF 42A (42B). Are removed to provide a baseband signal. That is, the echo signal is subjected to phase detection (quadrature phase detection) by the mixer 41A (41B) and the LPF 42A (42B) for each real part and imaginary part, and as a baseband Doppler signal reflecting the phase difference from the reference signal Extracted. The Doppler signal is converted into digital data by the A / D converter 43A (43B) for each real part and imaginary part, and is temporarily stored in the buffer memory 44A (44B).

  The MTI filter unit 45 is inserted in order to remove unnecessary echo signals reflected from the heart wall or the like using Doppler data groups individually stored in the buffer memories 44A and 44B. The processing of the MTI filter unit 45 achieves filtering according to the present invention. The specific configuration is as shown in FIG. 14, and the processing will be described later. The MTI filter unit 45 removes the Doppler component (clutter component) from the real organ reliably and accurately from the entire Doppler signal, and most of the remaining is extracted as the Doppler component (blood flow component) from the blood flow. .

  The real part and imaginary part Doppler data filtered by the MTI filter unit 45 are sent to the arithmetic circuit 46, respectively. The arithmetic circuit 46 estimates blood flow dynamic information using Doppler data of the real part and the imaginary part, and has, for example, an autocorrelator and an average speed calculator, a variance calculator, and a power calculator using the correlation result. Information such as the average velocity of blood flow, the distribution of velocity distribution, and the power of the reflected signal from the blood flow is estimated and calculated. The calculation result is temporarily stored in the CFM frame memory of the DSC 31 as CFM mode image data.

  In the DSC 31, the image data stored in the B-mode frame memory and the CFM-mode frame memory are read out separately by the standard TV system. Further, in parallel with this reading, one of the common pixels of both frame memories is alternatively selected to form one frame of image data in which the CFM mode image is superimposed on the B mode image (background image). . The image data is subjected to color application processing by the color processor 32, and then converted to an analog signal at a predetermined timing by the D / A converter and displayed on the TV monitor 34. As a result, a two-dimensional color image of blood flow velocity is displayed against a black and white B-mode image.

  Subsequently, the operation of this embodiment will be described focusing on the description of the configuration and operation of the MTI filter unit 45 described above.

  In order to create an image in the CFM mode, transmission / reception of ultrasonic pulses in the same scanning line direction is repeated N times (for example, 16 times). Based on the echo signal obtained every transmission and reception, the Doppler data subjected to quadrature detection is stored in the buffer memories 44A and 44B, respectively. Therefore, the baseband digital Doppler data stored in each of the buffer memories 44A and 44B is three-dimensional as shown in FIG. That is, the first dimension represents the number of scanning lines (numbers) 1 to L, the second dimension represents the number of pixels in the depth direction (numbers) 1 to M along each scanning line, and the third dimension. The dimension represents the number (number) 1 to N of Doppler data obtained by repeating transmission and reception for each pixel. The number of Doppler data is hereinafter referred to as “data number”. In the CFM mode, N pieces of Doppler data (see the hatched portion in FIG. 1) obtained in time series for each pixel are independently processed to obtain blood flow dynamic information for each pixel.

  Therefore, as shown in FIG. 17, the MTI filter unit 45 receives the digital quantity Doppler signals Zi (i = 0 to N−1) of the real part Q and the imaginary part I from the buffer memories 44A and 44B. Supplied for each position. The vertical axis direction in FIG. 17 corresponds to the amplitude value.

  The operational characteristics of the MTI filter unit 45 are based on the characteristics of the apparatus proposed in the earlier application, and are summarized in the following four items.

  (1): The instantaneous phase change of the clutter component between adjacent Doppler data is estimated, and the phase change of the entire Doppler signal is corrected according to the estimated amount (that is, the instantaneous phase change of the clutter component is corrected). Counteract). The term “instantaneous” in the present invention means that the observation time of N pieces of Doppler data is shorter.

This correction process is
(1a): Set a certain upper limit value for the estimated value of the phase change amount,
(1b): Pre-processing low-pass filtering on the Doppler signal,
(1c): Correct the phase correction amount using the signal power value.
(1a) or (1b) alone, in the combination of (1a) and (1b), in the combination of (1b) and (1c), or in the combination of (1a), (1b), (1c) It is characterized in that it is implemented.

  (2): After performing the correction process of (1) above, a constant amplitude value considered to correspond to the clutter component is subtracted to remove the clutter component.

  (3): After the processing of (1) or (2) above, high-pass filtering is performed to remove clutter components. The filtering characteristics are changed according to the characteristics of the output signal obtained by the process (2).

In this clutter component removal process,
(3a): While characterized in that the phase correction process of the above item (1) and the constant value subtraction process of the above item (2), the cutoff frequency control of the high-pass filter, and the Doppler signal gain process are used in combination. ,
(3b): performing pre-processing of low-pass filtering on the Doppler signal, then calculating a signal power value after subtraction of a constant value to determine the degree of the remaining clutter component, and
(3c): It is characterized in that the signal power value after subtraction of a constant value is corrected with the signal power value before phase correction.

  (4): If necessary, the influence of the phase change accompanying the processing of the above item (1) is canceled to obtain blood flow velocity information in accordance with the velocity concept that has been used conventionally.

In this case, especially
(4a): It is characterized in that the phase correction process using the phase correction amount according to the above item (1) is performed in both the CFM mode and the PW mode.

  In the following description, in order to make the description easy to understand, the N digital Doppler data strings forming the Doppler signal from one point (pixel) on the scanning section will be described (see the hatched portion in FIG. 1). . It is assumed that the same processing is performed for N Doppler data strings of the remaining points.

  In order to realize the various features described above, the MTI filter unit 45 divides the Doppler signals Zi of the real part and the imaginary part into two systems as shown in FIG. One system is a system for removing signal components (clutter components) mainly from organs, and the other system is a system for determining the removal characteristics of the signal component removing means.

  The one system includes a complex multiplier 45c that inputs the real part and the imaginary part of the Doppler signal Zi, and a constant value subtracter 45d, a high-pass filter (HPF) 45g, and a complex multiplier 45i on the output side. Prepare in this order.

  The other system includes a low-pass filter (LPF) 45j for inputting the real part and the imaginary part of the Doppler signal Zi, and a complex multiplier 45k, a constant value subtractor 45l, a clutter information detector 45e on the output side thereof. And a filter characteristic setting unit 45f in this order. Further, a gain setting unit 45n is interposed between the output side of the clutter information detector 45e and the amplifier 45m. The setting output of the filter characteristic setting unit 45f is output to the phase inverter 45h and the HPF 45g. Further, a clutter phase change amount estimator 45a, a multiplication signal generator 45b, a phase inverter 45h, and an amplifier 45m are provided on the output side of the low-pass filter 45j. The multiplication signal generated by the multiplication signal generator 45b is supplied to the complex multipliers 45c and 45k and the phase inverter 45h.

  First, the configuration and operation will be described from the system of characteristic determining means constituted by the circuit on the LPF 45j side.

  The real part and the imaginary part Doppler signal Zi input to the MTI filter unit 45 are input to the LPF 45j. As a result, the blood flow component having a large fluctuation included in each Doppler signal Zi is removed as preprocessing by the LPF 45j.

  The real part and imaginary part Doppler signals Zi that have undergone this pre-processing are input to the clutter phase change estimator 45a. As shown in FIG. 15, the clutter phase variation estimator 45a includes a complex multiplier 45a-1 on the input side, and a minute interval adder 45a-2 and a converter 45a-3 on the output side of the complex multiplier. , A phase corrector 45a-4 and a clip processor 45a-5 are provided in this order, and an addition average calculator 45a-6 is provided in parallel therewith. A clip value generator 45a-7 is also connected to the clip processor 45a-5.

The complex multiplier 45a-1 receives from the input Doppler signals of the real part Re [Zi] and the imaginary part Im [Zi],
[Equation 9]
[C1] i = Z _{i + 1} · Zi ^*
To obtain a real part R and an imaginary part I of C1,
[Equation 10]
[C0] i = Z _i · Z _i ^*
To obtain the power P.

The minute interval adder 45a-2 adds the real part R and the imaginary part I of the C1 value for the minute interval in the vicinity to the processing between the i-th and i + 1-th data, respectively, and the real part R of the C1 value. ^ And imaginary part I ^ are obtained. The converter 45a-3 uses the real part R ^ and the imaginary part I ^ of the C1 value.
θ = tan ⁻¹ (I ^ / R ^)
Is converted into a phase angle θ. This phase angle θ is sent to the phase corrector 45a-4 as an instantaneous phase change amount.

  On the other hand, the power P calculated by the complex multiplier 45-1 is sent to the addition average calculator 45a-6, and the N data is added and averaged based on, for example, the equation (8). The averaged power value inPow is sent to the phase corrector 45a-4. In this phase corrector 45a-4, the coefficient kp (i) is changed according to the change in the power value inPow of the Doppler signal, as shown in the equation (6), according to FIG. The instantaneous phase change amount φ is corrected.

  The instantaneous phase change amount ′ corrected by the power value of the Doppler signal is sent to the clip processor 45a-5. The processor 45a-5 is provided with the clip value (threshold value) of the phase change amount θmax and −θmax from the clip value generator 45a-7 as shown in FIG. For this reason, the clip processor 45a-5 suppresses the phase change amount θi to the clip value when the instantaneous phase change amount θi after the correction by the remaining power value exceeds the clip value.

  In this way, the instantaneous phase change amount θi reflecting the phase change of only the clutter component is estimated by the clutter phase change amount estimator 45a, and this change amount is sent to the multiplication signal generator 45b. The power value inPow calculated by the estimator 45a is sent to the clutter information detector 45e.

The multiplication signal generator 45b calculates the phase change amount sent at the time of sampling this time and the phase change amount sent up to the previous sampling,
[Equation 12]
exp {−j (θ ₁ + θ ₂ +... + θ _i−1 )} (9)
Generate a complex signal. This signal is output to complex multipliers 45c and 45k, both of which are responsible for phase correction, and to phase inverter 45h.

Therefore, in the complex multiplier 45k on the characteristic determination side (and the complex multiplier 45c on the clutter component removal side), between the input Doppler signal Zi,
[Equation 13]
Zi · exp {−j (θ ₁ + θ ₂ +... + Θ _i−1 )} (10)
Complex multiplication of is performed. By this phase correction (complex multiplication), the Doppler signal Zi is corrected for each real part and imaginary part based on the instantaneous phase change amount. For this reason, for example, the blood flow component having a large fluctuation in the Doppler signal Zi input in the form shown in FIG. 17A is removed in advance by the LPF 45j of the input stage, and the phase is corrected by the complex multiplier 45k. Conversion is performed as shown in d). By pre-removing the blood flow component by the LPF 45j, the waveform of the Doppler signal after phase correction becomes flatter than the case where the LPF 45j is not used, and only the DC component is obtained. The correction waveform becomes flat as the estimation accuracy of the phase change amount is high.

The Doppler signal Zi subjected to the LPF processing and further phase-corrected in this way is sent to the constant value subtractor 45l for each real part and imaginary part. The constant value subtracter 45d performs the constant value subtraction represented by the second term of the equation (4). Thus, as an example, the amplitude value “A · exp {j · φ ₀ }” of the first phase φ ₀ is regarded as the amplitude value of the clutter component from the Doppler signal in which the instantaneous phase change of the clutter component is canceled. Then subtract uniformly. The signal waveform from which the clutter component has been removed is as shown in FIG. That is, the amplitude value of the waveform is substantially sufficiently lowered to near zero, and the clutter component is removed satisfactorily.

  The substantially DC component Doppler signal processed by the constant value subtractor 45l is sent to the clutter information detector 45e for each of its real part and imaginary part and represents the degree of clutter component that may remain. A quantity is calculated.

As shown in FIG. 18, the clutter information detector 45e includes a complex multiplier 45e-1, an addition average calculator 45e-2, a feature amount conversion table 45e-3, and a spatial average calculator 45e- in order from the input side. 4 is provided. Among these, the complex computing unit 45e-1 and the addition average computing unit 45e-2 perform computations based on the above-described equation (8), and the complex computing unit 45e-1 is represented by [Expression 14].
[C0] i = Zi · Zi *
The addition average calculator 45e-2 calculates the power value cdsPow after subtraction of the constant value by averaging the complex multiplication values from i = 0 to N-1.

  The feature value conversion table 45e-3 is provided with the power value cdsPow after the constant value subtraction and the power value (input power value) inPow before the constant value subtraction described above. Therefore, the conversion table 45e-3 calculates the feature quantity sPow defined by the above-described equation (7) from both power values cdsPow and inPow. Thereby, the influence of the difference of the absolute value of the power signal resulting from the structure of the living body is canceled.

  In the clutter information detector 45e, the spatial average calculator 45w-4 further performs spatial average processing of the obtained feature quantity sPow. As a result, the feature quantity does not take a spatially unstable value due to ultrasonic interference called speckle. It is desirable to install the spatial average calculator 45e-4. The feature quantity sPow calculated in this way is input to the filter characteristic setting unit 45f and the gain setting unit 45n.

  In the filter characteristic setting unit 45f, the characteristic of the high-pass filter 45g corresponding to the feature amount sPow is set as shown in FIG. 12, for example. If the amount of change in the clutter component is small, the clutter component is sufficiently reduced by the processing of equation (4), so that the value of the feature amount sPow becomes small. On the contrary, when the change in the clutter component is large, the feature amount The value of sPow increases. Therefore, when the value of the feature amount sPow is small, the cutoff frequency of a high-pass filter 45g described later is set to be low. Even if it is set to such a low value, the clutter component is sufficiently reduced by the high-pass filter. Conversely, when the feature amount sPow is large, the cutoff frequency of the high-pass filter 45g is set to be high.

  In parallel with this, the gain setting unit 45n sets a signal gain as shown in FIG. 12 as an example. When the feature amount sPow increases, the power of the high-speed component as the clutter component included in the Doppler signal is large, so that even if a blood flow component is included, it is considered difficult to remove only by the high-pass filter. . Therefore, in such a situation, as shown in FIG. 12, the gain is reduced to remove the clutter component.

  On the other hand, the phase inverter 45h inverts the phase of the multiplication signal expressed by the equation (9) generated by the multiplication signal generator 45b and applies it to the gain variable amplifier 45m. The variable gain amplifier 45m amplifies the amplitude of the phase-inverted multiplication signal (see Expression (9)) with the gain set by the gain setting unit 45n and supplies the amplified signal to the complex multiplier 45i.

  Next, a system for removing clutter components will be described. In the complex multiplier 45c, complex multiplication based on the equation (10) is performed with the input Doppler signal Zi. For this reason, the complex multiplier 45c as the phase correction means corrects the Doppler signal Zi for each real part and imaginary part based on the instantaneous phase change amount by this phase correction (complex multiplication). For example, FIG. The Doppler signal Zi input in the form indicated by () is converted as shown in FIG.

  That is, it is assumed that the imaginary part signal of the Doppler signal input to the MTI filter unit 45 is as shown in FIG. This waveform is in a state where a Doppler shift component of a clutter component that changes with a large amplitude and at a low speed is superimposed on a Doppler shift component of a blood flow that does not appear in the figure but changes with a small amplitude. With respect to this waveform, the signal waveform obtained by performing the phase correction based on the instantaneous phase change amount of the clutter component has no large amplitude and low frequency waveform undulation due to the clutter component as shown in FIG. Is a waveform with a substantially constant amplitude having only fluctuations corresponding to the Doppler shift experienced by the blood flow.

This phase-corrected Doppler signal is subjected to constant value subtraction represented by the second term of equation (4) by the constant value subtractor 45d for each real part and imaginary part. As a result, the amplitude value “A · exp {j · φ ₀ }” at the first phase φ0 is uniformly regarded as the amplitude value of the clutter component from the Doppler signal in which the instantaneous phase change of the clutter component is canceled. Subtract. The signal waveform from which the clutter component has been removed is as shown in FIG. That is, the amplitude value of the waveform is reduced to nearly zero, and the clutter component is removed satisfactorily.

  The constant value removed by the constant subtractor 45d may be set to an arbitrary value among the N pieces of data of the Doppler signal, or may be set to an average value of the N pieces of Doppler data. Good.

  The Doppler signal Zi after this constant value subtraction is supplied to the high-pass filter 45g for each of its real part and imaginary part. The basic configuration of the high-pass filter 45g may be FIR type or IIR type. FIG. 19 shows an example of the IIR type. At least the order and the cut-off frequency of the filter 45g are automatically set to values set by the filter characteristic setting unit 45f. For this reason, only the high frequency component of the Doppler signal Zi passes and the clutter component is removed.

  The Doppler signal from which the clutter component has been removed by the high-pass filter 45g is subjected to complex multiplication shown in Expression (5) for each real part and imaginary part. As a result, a phase opposite to the phase amount corrected by the complex multiplier 45k is applied to the Doppler signal and converted to a Doppler signal for the ultrasonic probe. At this time, the amplitude value of the signal to be subjected to complex multiplication is set by the gain setting unit 45n according to the feature quantity sPow. This phase inversion process does not need to be executed when the blood flow velocity for the tissue is estimated and displayed.

  The Doppler signal processed in this way by the MTI filter unit 45 is sent to the calculation circuit 46, where blood flow information such as blood flow velocity, power of the Doppler signal, and distribution of velocity distribution is calculated. As described above, these pieces of information are displayed on the TV monitor 34 in an appropriate manner.

  Since the MTI filter unit 45 of the present embodiment is configured and operates as described above, the effects thereof are as follows.

  Even if the clutter component moves due to the influence of heartbeat or respiration, the clutter component can be removed reliably and accurately, and only the Doppler signal from the blood flow can be effectively extracted. In particular, when the phase change amount is obtained every moment, which is shorter than the observation time, and the phase change of the clutter component is corrected (cancelled) each time, the phase correction is performed using one phase correction amount for the entire observation time. Compared to the above, the phase correction accuracy is remarkably improved. As a result, it is possible to extract a clutter component having an almost constant amplitude value (which is still superimposed with a Doppler signal from the blood flow), and a constant value subtraction process for removing the clutter component to be performed thereafter is performed. This is much more effective than before.

  In particular, when imaging a vascular system such as a heart chamber that is sufficiently larger than the transmission / reception beam width of ultrasonic waves, or when a contrast agent is injected into a living body, the signal value of the blood flow component compared to the clutter component Even in shooting situations where the influence cannot be ignored, the low-pass filter for preprocessing, the clipping process of the phase change estimation value, and the correction process of the phase change estimation value based on the power value of the Doppler signal, Regardless of the amount of movement of the real organ, the clutter component can be sufficiently and reliably removed.

  In other words, the clutter component and the echo component from the low-speed blood flow can be reliably and finely separated, the clutter component from the moving real organ is surely removed, and the very low-speed blood flow is overlooked. It is possible to generate a blood flow image having a high detection capability and a two-dimensional distribution. Therefore, blood flow information with high diagnostic ability and high reliability can be provided.

  In addition, if there is a clutter component that still remains after such removal processing, it is reliably removed by a high-pass filter. In addition, the cutoff characteristics of the high-pass filter are adaptively controlled according to the power ratio before and after the constant value subtraction corresponding to the clutter component using the Doppler signal after preprocessing by the low-pass filter, and the power ratio The gain of the Doppler signal is also adaptively controlled in parallel. As a result, even if the remaining clutter component after the phase correction using the instantaneous phase correction amount and the clutter removal processing is large, the high-pass filter cutoff frequency is not increased unnecessarily, and a high-speed residual clutter component is ensured. Can be reduced.

  In addition, the characteristic value of the signal that determines the magnitude of the clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal processing, the power value of the clutter component is uniformly distributed due to the influence of biological attenuation, etc. Even if it is not, it is possible to determine the size of the same component that reliably reflects the size of the clutter component, and to obtain a reliable and highly accurate clutter removal effect.

  In this embodiment, as a means for changing the signal gain, a method of varying the amplitude of the complex signal to be given to the complex multiplier 45i by the gain is employed. The gain of the coefficient to be given may be changed, or the gain may be given by inserting a multiplier or ROM in the Doppler signal system.

  In the above-described embodiment, i) clip processing for setting an upper limit to the estimated value of the phase change amount, ii) preprocessing by a low-pass filter, and iii) estimation of the phase change amount based on the power value inPow of the Doppler signal In the present invention, only the process of i) or ii) may be performed alone, or the process of combining i) and ii), or ii ) And iii) may be performed alone.

[Second Embodiment]
Subsequently, an ultrasonic Doppler diagnostic apparatus according to a second embodiment of the present invention will be described with reference to FIG. In the following embodiments, the same or equivalent components as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  The ultrasonic Doppler diagnostic apparatus according to this embodiment has a simplified configuration. Specifically, like the MTI filter unit 45 shown in FIG. 20, the constant value subtracter (see FIG. 14) inserted in the clutter component removal system in the first embodiment is removed, and the complex multiplier 45c and A high-pass filter 45g is directly connected.

  The case where the configuration can be simplified in this way is a case where the constant value subtraction process of the second term is not necessary in the clutter reduction process represented by the equation (4). As shown in FIG. 17D, when the Doppler data string becomes a substantially flat signal only by the phase correction processing corresponding to the first term of the equation (4), the high-pass filter 45g is provided after the phase correction, as described above. Such a constant value subtractor is not always necessary when the filtering process is performed. Thereby, the configuration of the MTI filter unit 45 can be further simplified.

[Third Embodiment]
An ultrasonic Doppler diagnostic apparatus according to a third embodiment of the present invention will be described with reference to FIG.

  This ultrasonic Doppler diagnostic apparatus pays attention to the problems (B) and (C) among the various problems described above, and emphasizes the solution of these problems. This is considered that when contrast echography in which an ultrasound contrast agent is administered to a living body is not performed, the power value of the blood flow component is rarely extremely increased even in a large blood vessel system. In such a case, the blood flow component can be detected only by the correction circuit for the phase change amount estimation value based on the input power value mounted on the clutter phase change amount 45a shown in FIG. The effect removal is effective to a considerable extent.

  Therefore, as shown in the MTI filter unit 45 of the same figure, the configuration is such that the preprocessing LPF on the input side is removed and the complex multiplier 45c for phase correction and the constant value subtractor 45d for removing clutter components are shared. take. Thereby, the configuration of the MTI filter unit is simplified as compared with that of the above-described embodiment. Naturally, the above-described problems (B) and (C) are also solved by this simplified filter configuration.

[Fourth Embodiment]
An ultrasonic Doppler diagnostic device according to a fourth embodiment of the present invention will be described with reference to FIG.

  This ultrasonic Doppler diagnostic apparatus is characterized in that it aims to improve the performance with respect to the contrast agent as compared with the apparatus of the third embodiment while maintaining a simplified circuit configuration of the MTI filter unit. Specifically, as shown in FIG. 22, a parallel circuit for the constant value subtracter 45d is drawn from the output side of the complex multiplier 45c inserted in the system for removing the clutter component, and the LPF 45o and the constant value subtractor 45p are connected to this circuit. Are inserted in this order. The output side of the constant value subtractor 45p is connected to the input of the clutter information detector 45e described above.

  The reason for this configuration is as follows. In order to estimate only the phase change amount of the clutter component, the correction process of the phase change amount based on the input power value provided in the clutter phase change amount estimator 45a or the upper limit value clipping process of the phase change amount is effective to some extent To work. Therefore, an LPF 45o for preprocessing of the feature amount calculation indicating the degree of the clutter component remaining after the constant value subtraction is inserted in the preceding stage of the clutter information detector 45e, and this LPF output is passed through the constant value subtractor 45p to the clutter information. Input to the detector 45e. As a result, the power ratio sPow, which is the feature amount from which the influence of the blood flow component has been removed by the LPF 45o, is calculated by the clutter information detector 45e. In this calculation, it is preferable to use the power ratio sPow in which the β value shown in Expression (7) is increased and the weight of the input power value inPow is reduced.

  Since the constant value subtraction process is physically equivalent to a high pass filter, the LPF 45o and the subsequent constant value subtractor 45p may be replaced with a band pass filter (BPF). Thereby, the circuit configuration can be simplified, and another preferred embodiment is obtained.

  In each of the third and fourth embodiments described above, as described in the second embodiment, it is possible to remove the constant value subtractor 45d of the system that removes the clutter component.

[Fifth Embodiment]
An ultrasonic Doppler diagnostic device according to a fifth embodiment of the present invention will be described with reference to FIGS.

  This ultrasonic Doppler diagnostic apparatus aims to solve the above-mentioned problem (D) and obtain blood flow velocity information that is significantly consistent between the CFM mode and the PW mode.

  In order to achieve this object, this ultrasonic Doppler apparatus adopts a configuration in which the phase correction means is shared by both the CFM mode and PW mode circuits as shown in FIGS. Specifically, as shown in FIG. 24, lead wires are drawn out from the input side and the output side of the complex multiplier 45c for obtaining the blood flow velocity relative to the clutter component in the MTI filter unit 45, respectively. Connect to switch 45q. The changeover switch 45q is an electronic switch that can selectively switch the changeover path between the input side and the output side of the complex multiplier 45c for each signal path of the real part and the imaginary part. Switching is performed according to a switching signal from the controller. The MTI filter unit 45 has the same configuration as that described in the second embodiment, but this may be the circuit configuration employed in the first, third, or fourth embodiment.

  The switching output terminals of the real part and imaginary part of the changeover switch 45q are connected to a PW processing system circuit as shown in FIG. This PW processing system circuit includes range gates 61A and 61B, integrators 62A and 62B, HPFs 63A and 63B, and A / D converters 64A and 64B for each channel of the real part and the imaginary part. A calculation circuit 65 for calculating blood flow information in the PW mode is provided at the subsequent stage. The operation of these circuits is the same as that conventionally known. The blood flow information calculated by the arithmetic circuit 65 is sent to the display system DSC 31 and displayed on the TV monitor 34.

  In this circuit configuration, when PW processing for obtaining a blood flow velocity relative to the clutter component is to be performed, the switch path of the changeover switch 45q is switched to the “output side” of the complex multiplier 45c. Alternatively, when performing PW processing for obtaining a blood flow velocity relative to the ultrasonic probe in order to match the conventional practice, the switch path of the changeover switch 45q is switched to the “input side” of the complex multiplier 45c. As a result, the PW mode processing system can select the Doppler signal after phase correction or before phase correction, and alternatively select the blood flow velocity relative to the clutter component or the blood flow velocity relative to the probe. It can be calculated.

  As a result, the changeover switch 45q is switched to the “input side”, and in both the CFM mode and the PW mode, blood flow information relative to the ultrasonic probe can be calculated and displayed in accordance with conventional practice. This consistency can be taken. In addition, when the MTI filter unit that does not use the phase inverter 45h is configured, the changeover switch is switched to the “output side” to obtain the blood flow velocity relative to the clutter component in both the CFM mode and the PW mode, Significant consistency of relative speed can be taken.

  The present invention is not limited to the configuration of the embodiment described above, and various modifications can be made by those skilled in the art without departing from the spirit of the invention described in the claims. Of course, examples are also included in the present invention.

  As described above, according to the ultrasonic Doppler diagnostic apparatus according to the present invention, the blood flow component having a relatively high velocity (the Doppler signal component from the blood flow) is removed, so that only the clutter component is substantially obtained. Correct the instantaneous phase change amount between the Doppler signal data and / or adaptively change the cutoff characteristic of the subsequent high-pass filter according to the nature of the Doppler signal which has only the clutter component. By doing so, even if the influence of blood flow components becomes larger than usual, as in the case of large blood vessels or blood vessels to which contrast medium is administered, only clutter components can be reliably and sufficiently removed from the Doppler signal. Can do. This reliably prevents an undesirable situation in which the influence of clutter components appears in the displayed blood flow information, improves blood flow detection capability and display capability, and provides high accuracy blood flow information to the device user. be able to.

  In particular, the clutter component can be reliably removed regardless of the amount of movement of the parenchymal organ, and a blood flow with a very low velocity can also be reliably detected.

  In addition, even when there is a large amount of clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal process, the high-pass filter does not increase the cutoff frequency unnecessarily, and the high-speed residual clutter component is reliably detected. Can be reduced.

  In addition, the characteristic value of the signal that determines the magnitude of the clutter component remaining after the phase correction using the instantaneous phase correction amount and the clutter removal processing, the power value of the clutter component is uniformly distributed due to the influence of biological attenuation, etc. Even if it is not, it is possible to determine the size of the same component that reliably reflects the size of the clutter component, and to obtain a reliable and highly accurate clutter removal effect.

  Furthermore, the deviation of the significance of the blood flow velocity provided from both the CFM mode and the PW mode processing system is eliminated, and both the blood flow velocity relative to the clutter component or the blood flow velocity relative to the probe are both included. Can be provided, avoid unnecessary confusion for the user of the apparatus, and provide convenience.

Explanatory drawing which shows typically the set of the echo data accompanying transmission and reception several times to the same position obtained at the time of CFM mode and PW mode. The figure explaining the inconvenience of the cutoff characteristic of the conventional MTI filter. The discrete waveform figure of the Doppler data sequence (Doppler signal) for demonstrating operation | movement of the apparatus of a prior application proposal. The figure which shows the example of control of the cutoff frequency of the high-pass filter in the apparatus of a prior application proposal. The figure which shows the example of control of the attenuation amount of the high-pass filter in the apparatus of a prior application proposal. FIG. 6 is a relationship diagram between a signal power value and a coefficient for phase change correction related to one countermeasure for avoiding the influence of a clutter component when a blood vessel is thick. The figure explaining the blurring of the clutter component to the blood vessel space when the blood vessel is thick. The figure explaining the setting of the estimation upper limit of estimated value (theta) i of phase variation. The spectrum schematic diagram which shows the change of the estimated value (theta) i of the phase change amount based on the apparatus of a prior application proposal for every aspect of a blood flow. The spectrum schematic diagram which shows the change of the estimated value (theta) i of phase change amount for every aspect of blood flow when the pre-processing by the low-pass filter which concerns on this invention is performed. The spectrum schematic diagram explaining the pre-processing operation | movement by the low-pass filter which concerns on this invention for every diagnostic region | part. The figure which shows the example of control of the gain with respect to the cutoff frequency of a high-pass filter, and a Doppler signal based on this invention, respectively. 1 is a schematic block diagram of an ultrasonic Doppler diagnostic apparatus according to an embodiment of the present invention. The block diagram of the MTI filter part which concerns on 1st Embodiment. The block diagram which shows the structural example of a clutter phase change amount estimator. The graph explaining an example of the relationship between the input power value of a Doppler signal, and the coefficient for correction of a phase variation. The discrete waveform figure of the Doppler data sequence (Doppler signal) for demonstrating operation | movement of the apparatus of an Example. The block diagram which shows the structural example of a clutter information detector. The figure which shows the structural example of a high pass filter. The block diagram of the MTI filter part which concerns on 2nd Embodiment. The block diagram of the MTI filter part which concerns on 3rd Embodiment. The block diagram of the MTI filter part which concerns on 4th Embodiment. The block diagram of the ultrasonic Doppler diagnostic apparatus which concerns on 5th Embodiment. The block diagram of the MTI filter part which concerns on 5th Embodiment.

Explanation of symbols

1 Ultrasonic probe (transmission / reception means)
2 Transmission circuit (transmission / reception means)
3 Receiving / processing circuit 21 Receiving circuit (transmission / reception means)
24 Display circuit (visualization means)
41A, 41B mixer (Doppler signal extraction means)
42A, 42B LPF (Doppler signal extraction means)
43A, 43B A / D converter (Doppler signal extraction means)
44A, 44B Buffer memory (Doppler signal extraction means)
45 MTI filter unit 46 arithmetic circuit (blood flow information extracting means)
47 Reference Transmitter 48 Phaser 45a Clutter Phase Change Estimator (Decision Unit / Phase Estimation Unit)
45b Multiplication signal generator (decision means / phase estimation means)
45c Complex multiplier (clutter component removal means / phase correction means)
45i complex multiplier (clutter component removal means)
45d constant value subtracter (clutter component removal means / subtraction means)
45e Clutter information detector (determination means)
45f Filter characteristic setting device (decision means)
45g HPF (Clutter component removal means)
45h Phase inverter (determination means)
45j LPF (pre-processing means)
45k complex multiplier (decision means)
45l constant value subtracter (decision means)
45m variable gain amplifier (determination means)
45n gain setting device (decision means)
45a-1 Complex multiplier 45a-2 Minute interval adder 45a-3 Converter 45a-4 Phase corrector 45a-5 Clip processor 45a-6 Addition averaging calculator 45a-7 Clip value generator 45e-1 Complex multiplier 45e-2 addition average calculator 45e-3 feature amount exchange table 45e-4 spatial average calculator

Claims (27)

A transmission / reception means for transmitting an ultrasonic signal along the cross section in the subject a plurality of times in each scanning line direction and receiving an ultrasonic echo signal reflected from the subject;
Doppler signal extraction means for obtaining, for each spatial position, Doppler signals composed of a plurality of time-series Doppler data reflected from the same spatial position in each scanning line direction based on the ultrasonic echo signal;
Preprocessing means for removing in advance a signal component having a large variation in time series from the Doppler signal;
Determining means for determining information relating to removal of clutter components accompanying the reflection of the ultrasonic signal by the organ using the Doppler signal from which signal components have been removed by the preprocessing means;
Clutter component removal means for removing the clutter component from the Doppler signal based on the information, and blood flow information extraction for extracting blood flow information of the cross section using the Doppler signal obtained by removal of the clutter component removal means Means,
The determination means includes phase estimation means for estimating an instantaneous phase change amount of the clutter component included in the Doppler signal processed by the preprocessing means,
The ultrasonic Doppler diagnostic apparatus, wherein the clutter component removing unit includes a phase correcting unit that corrects the phase of each Doppler data of the Doppler signal based on the phase change amount estimated by the phase estimating unit. In the invention of claim 1,
An ultrasonic Doppler diagnostic apparatus comprising visualization means for visualizing the blood flow information extracted by the blood flow information extraction means. In the invention of claim 1,
The preprocessing means is a low-pass filter, and the low-pass filter removes a reflected ultrasonic component from a blood flow passing through the cross section as a frequency band for removing the signal component having a large variation in time series. Ultrasonic Doppler diagnostic device set to the band. In the invention of claim 1,
The clutter component removing means is an ultrasonic Doppler diagnostic apparatus comprising subtracting means for subtracting a fixed value from each Doppler data of the Doppler signal phase-corrected by the phase correcting means. In the invention of claim 4,
The ultrasonic Doppler diagnostic apparatus in which the constant value is set to a value corresponding to the clutter component. In the invention of claim 1,
The phase estimation means calculates the instantaneous phase change amount using a part of Doppler data in the Doppler data sequence including Doppler data for performing phase correction in the Doppler data sequence forming the Doppler signal. An ultrasonic Doppler diagnostic apparatus which is a means for estimating. In the invention of claim 1,
The ultrasonic Doppler diagnostic apparatus, wherein the phase estimation means includes correction means for correcting the instantaneous phase change amount according to the power of the Doppler signal. In the invention of claim 1,
The ultrasonic Doppler diagnostic apparatus, wherein the phase estimation means includes clip processing means for clipping an absolute value of the phase change amount by a predetermined value. In the invention of claim 4,
The ultrasonic Doppler diagnostic apparatus, wherein the clutter component removing unit includes a high-pass filter that performs high-pass filtering on the Doppler signal obtained by subtracting a constant value by the subtracting unit. In the invention of claim 9,
The determination means includes another phase correction means for correcting the phase of each Doppler data of the Doppler signal processed by the preprocessing means using the instantaneous phase change amount, and the phase-corrected Doppler signal. An ultrasonic Doppler diagnostic apparatus comprising: another constant value subtracting means for subtracting a constant value from each Doppler data; and a control means for controlling the characteristics of the high-pass filter using the Doppler signal before and after the constant value subtraction. In the invention of claim 10,
The control means calculates a power value of the Doppler signal obtained by subtracting a constant value by the first calculating means for calculating the power value of the Doppler signal processed by the preprocessing means and the other constant value subtracting means. Second calculating means, third calculating means for calculating data for determining characteristics of the high-pass filter from both power values calculated by the first and second calculating means, and the high-pass filter according to the data An ultrasonic Doppler diagnostic apparatus comprising setting means for setting the characteristics of In the invention of claim 11,
The third calculating means has a power ratio “cdsPow / power ratio between the power value inPow of the Doppler signal calculated by the first calculating means and the power value cdsPow of the Doppler signal calculated by the second calculating means. An ultrasonic Doppler diagnostic apparatus which is a means for calculating “inPow” as the data. In the invention of claim 12,
The ultrasonic Doppler diagnostic apparatus, wherein the setting means is a means for setting at least one of a cutoff frequency or an order of the high-pass filter in accordance with the power ratio. In the invention according to claim 3,
The ultrasonic Doppler diagnostic apparatus, wherein the setting means is means for holding the cutoff frequency at a high constant value when the power ratio increases. In the invention of claim 12,
The ultrasonic Doppler diagnostic apparatus, wherein the clutter component removing means includes amplification means for amplifying the Doppler signal subtracted by a constant value with a variable gain. In the invention of claim 15,
An ultrasonic Doppler diagnostic apparatus comprising gain setting means for variably setting the variable gain based on the power ratio calculated by the third calculation means. In the invention of claim 16,
The ultrasonic Doppler diagnostic apparatus, wherein the gain setting means is means for holding the variable gain at a constant value that is lower when the power ratio is higher. In the invention of claim 1,
The determining means includes phase inverting means for inverting the instantaneous phase change amount estimated by the phase estimating means, and the clutter component removing means is decremented by a fixed value by the amount of the phase change amount inverted in phase. An ultrasonic Doppler diagnostic apparatus comprising phase cancellation means for returning the phase of the Doppler signal. In the invention of claim 1,
The blood flow information extraction means includes a plurality of analysis means for analyzing the blood flow velocity using the Doppler signal, and the analysis means of each system analyzes relative blood flow velocity information having the same significance. An ultrasonic Doppler diagnostic device as a means. The invention according to claim 19,
The ultrasonic Doppler diagnostic apparatus, wherein the plurality of systems of analysis means includes analysis means for performing CFM mode signal processing of the blood flow and analysis means for performing PW mode signal processing of the blood flow. A transmission / reception means for transmitting an ultrasonic signal along the cross section in the subject a plurality of times in each scanning line direction and receiving an ultrasonic echo signal reflected from the subject;
Doppler signal extraction means for obtaining, for each spatial position, Doppler signals composed of a plurality of time-series Doppler data reflected from the same spatial position in each scanning line direction based on the ultrasonic echo signal;
Determining means for determining information on removal of clutter components associated with reflection of the ultrasound signal by the organ using the Doppler signal;
A clutter component removing means including a high-pass filter for removing the clutter component from the Doppler signal based on the information and a circuit for gain processing the Doppler signal;
Blood flow information extracting means for extracting blood flow information of the cross section using the Doppler signal obtained by the removal of the clutter component removing means;
Visualizing means for visualizing the blood flow information extracted by the blood flow information extracting means;
The determining means comprises phase estimating means for estimating an instantaneous phase change amount of the clutter component included in the Doppler signal,
The ultrasonic Doppler diagnostic apparatus, wherein the clutter component removing unit includes a phase correcting unit that corrects the phase of each Doppler data of the Doppler signal based on the phase change amount estimated by the phase estimating unit. In the invention according to claim 1 or 21,
The ultrasonic phase Doppler diagnostic apparatus, wherein the phase estimation unit estimates the instantaneous phase change amount using Doppler data included in a minute time interval in a Doppler data sequence forming the Doppler signal. In the invention of claim 21,
The ultrasonic Doppler diagnostic apparatus, wherein the phase estimation means includes clip processing means for clipping an absolute value of the phase change amount by a predetermined value. In the invention of claim 21,
The clutter component removing means is an ultrasonic Doppler diagnostic apparatus comprising subtracting means for subtracting a fixed value from each Doppler data of the Doppler signal phase-corrected by the phase correcting means. In the invention of claim 21,
The ultrasonic Doppler diagnostic apparatus in which the constant value is set to a value corresponding to the clutter component. In the invention of claim 21,
The determination means subtracts a constant value from each phase of the Doppler data of the phase corrected Doppler signal, and another phase correction means for correcting the phase of each Doppler data of the Doppler signal using the instantaneous phase change amount. An ultrasonic Doppler diagnostic apparatus comprising: another constant value subtracting means for controlling and a control means for controlling characteristics of the high-pass filter and the gain processing circuit using the power value of the Doppler signal before and after the constant value subtraction. In the invention of claim 21,
The blood flow information extraction means includes a plurality of analysis means for analyzing the blood flow velocity using the Doppler signal, and the analysis means of each system analyzes relative blood flow velocity information having the same significance. An ultrasonic Doppler diagnostic device as a means.

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