JP4373735B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that extracts a predetermined signal component from a received signal obtained by transmitting and receiving ultrasonic waves.

  An imaging method using an ultrasonic contrast agent in an ultrasonic diagnostic apparatus is known. The ultrasound contrast agent contains microbubbles having strong nonlinear scattering characteristics, and therefore, the echo from the ultrasound contrast agent contains a larger nonlinear scattering component than the echo from the living tissue. This nonlinear scattering characteristic of the ultrasonic contrast agent is used, for example, for visualization of blood flow. That is, an ultrasound contrast agent is administered into a blood vessel, and is used for imaging a minute blood flow that is buried in echoes from surrounding tissues with only a linear scattering component.

  A received signal in a transmission / reception wave accompanied by nonlinear scattering includes a signal component due to nonlinear scattering such as second-order scattering and third-order scattering in addition to a linear fundamental wave component due to first-order scattering (linear scattering). Examples of signal components due to nonlinear scattering include second harmonic components due to second-order scattering, third-order harmonic components due to third-order scattering, and nonlinear fundamental wave components. In an ultrasonic diagnostic apparatus that uses nonlinear scattering characteristics, these second-order harmonic components, third-order harmonic components, or nonlinear fundamental wave components are used.

  Patent Document 1 discloses an ultrasonic imaging method using a nonlinear fundamental wave component among signal components due to nonlinear scattering. In the method described in this document, an ultrasonic wave is transmitted a plurality of times while changing a transmitted sound pressure, and a reception signal obtained by a plurality of transmissions is appropriately combined from a received signal. A third-order scattering nonlinear signal including a nonlinear fundamental wave component is extracted.

  On the other hand, an ultrasonic diagnostic apparatus that performs multistage focus transmission is known. Multi-stage focus transmission realizes good transmission / reception characteristics from a short distance to a long distance by transmitting ultrasonic waves to a plurality of focus points in each ultrasonic beam direction.

  Patent Document 2 discloses an ultrasonic diagnostic apparatus that performs multistage focus transmission and uses nonlinear scattering characteristics. The apparatus described in this document performs multistage focus transmission in order to obtain a signal component due to nonlinear scattering well from a short distance to a long distance.

Special table 2003-500150 gazette JP 2001-245889 A

  In multistage focus transmission, ultrasonic waves are transmitted to a plurality of focus points in each ultrasonic beam direction. For this reason, a decrease in the frame rate becomes a problem. In order to solve this, a technique is known in which different frequencies are assigned to a plurality of transmission focus points and ultrasonic waves are transmitted to the plurality of focus points almost simultaneously. For example, when performing multistage focus transmission for two points, a short-distance focus point and a long-distance focus point, high-frequency ultrasonic waves are used for the short-distance focus point and low-frequency focus points are used. Ultrasound is used. And the received signal acquired by multistage focus transmission is classified into a high frequency component and a low frequency component by a band pass filter.

  However, a problem arises when performing multistage focus transmission using different frequencies in an ultrasonic diagnostic apparatus using nonlinear scattering characteristics. In other words, depending on the interrelationship of the frequencies used for transmission to the far-distance focus point and the short-distance focus point, harmonic components due to low-frequency transmission to the long-distance focus point correspond to the short-distance focus point. In the frequency band of the received signal. As a result, it is not possible to appropriately extract a predetermined signal component such as a nonlinear fundamental wave component from the received signal corresponding to the short distance focus point.

  Accordingly, an object of the present invention is to extract a predetermined signal component from a reception signal acquired by multistage focus transmission.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention is an ultrasonic diagnostic apparatus that transmits a plurality of times for each transmission focus point in multistage focus transmission. A transmission processing unit that performs transmission weighting for each of the plurality of transmissions by using a transmission weighting value set consisting of transmission weighting values for each transmission, A reception weight value set for each transmission focus point, and using a reception weight value set consisting of reception weight values for each transmission, for a received signal acquired at each of the multiple transmissions Reception processing means for performing reception weighting addition, and from a plurality of transmission weight value sets and a plurality of reception weight value sets for a plurality of transmission focus points That weight set is a extract satisfy the condition for extracting a predetermined signal component contained in the received signal.

  According to the above configuration, it is possible to extract a predetermined signal component included in the received signal by setting conditions for a plurality of weight values belonging to the weight value set. For example, a predetermined signal component can be extracted by removing unnecessary signal components from the second harmonic component, the third harmonic component, or the nonlinear fundamental wave component included in the received signal.

  Preferably, the predetermined signal component is a nonlinear fundamental wave component. Preferably, the extraction condition includes a condition for removing a harmonic component included in the received signal. Preferably, the extraction condition includes a condition for removing a linear fundamental wave component included in the received signal.

  Preferably, as the multi-stage focus transmission, multi-stage transmission including transmission to the first transmission focus point and transmission to the second transmission focus point is performed twice, and the transmission processing means includes the first transmission focus. Using the first transmission weight set corresponding to the point, the transmission weighting is performed for the two high-frequency transmissions to the first transmission focus point in the two multi-stage transmissions, and the second Using the second transmission weight set corresponding to the transmission focus point, transmission weighting is performed on the two low-frequency transmissions to the second transmission focus point in the two multistage transmissions, and the reception is performed. The processing means uses the first reception weight value set corresponding to the first transmission focus point, and adds the reception weight to the high frequency band reception signal acquired twice by the two multistage transmissions. And using the second reception weight value set corresponding to the second transmission focus point, reception weight addition is performed on the low frequency band reception signal acquired twice by the two multistage transmissions. , The first transmission weight value set, the second transmission weight value set, the first reception weight value set, and the second reception weight value set, the weight value set is the high frequency band reception signal and the low frequency band reception. It is assumed that the extraction condition for extracting the nonlinear fundamental wave component included in the signal is satisfied.

  According to the above configuration, it is possible to extract a predetermined signal component from the received signal while minimizing the sacrifice of the frame rate by minimizing the number of multistage transmissions to two.

In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes transmission to a first transmission focus point and transmission to a second transmission focus point as multistage focus transmission. In an ultrasonic diagnostic apparatus that performs multistage transmission N times (N is an integer of 2 or more), a low-band transmission signal is generated in a low-frequency band corresponding to the second transmission focus point, and the first transmission focus point A transmission signal generator for generating a high-band transmission signal in a high-frequency band corresponding to N, and N transmissions corresponding to each of N transmissions to the first transmission focus point in the N multistage transmissions First transmission processing means for performing transmission weighting on the N multistage transmissions using a first transmission weighting value set {α _H1 , α _H2 ,..., Α _HN } including weight values; In the N multi-stage transmission Said second N times of the second transmission weighting value set of each of N transmit weighting values corresponding to the transmitting of the transmission focusing point _{{α L1, α L2, ···} , α LN} using the , Using the second transmission processing means for performing transmission weighting on the N number of multi-stage transmissions, the band pass filter for the high frequency band, and the band pass filter for the low frequency band. Corresponding to each of the high-band received signal acquired N times, and a received signal classification unit that separates each of the received signals acquired N times corresponding to each wave into a high-band received signal and a low-band received signal Using the first reception weight value set {β _H1 , β _H2 ,..., Β _HN } composed of N reception weight values, reception weight addition is performed on the high-band reception signal acquired N times. First reception processing means to perform and before N times of acquisition Second reception weighting value set of N received weighting values corresponding to each of the low-band reception signal _{{β L1, β L2, ···} , β LN} by using the low band to be acquired N times Second reception processing means for performing reception weighting addition on the received signal, the first transmission weighting value set, the second transmission weighting value set, the first reception weighting value set, and the second reception weighting. It is assumed that a set of weight values composed of value sets satisfies an extraction condition for extracting a predetermined signal component included in the high-band received signal and the low-band received signal.

Preferably, the extraction condition includes a condition for removing a second harmonic component due to the low-band transmission signal included in the high-band received signal, and is included in the weight value set for the condition. It is assumed that the weight values satisfy α _L1 ² β _H1 + α _L2 ² β _H2 + α _L3 ² β _H3 +... + Α _LN ² β _HN = 0. According to the above configuration, the second harmonic component caused by the low-band transmission signal included in the high-band reception signal can be removed.

Preferably, the extraction condition includes a condition for removing a linear fundamental wave component included in the high-band received signal, and the weight value included in the weight value set for the condition is α _H1 β. _H1 + α _H2 β _H2 + α _H3 β _H3 +... + Α _HN β _HN = 0. According to the above configuration, the linear fundamental wave component included in the high-band received signal can be removed.

Preferably, the extraction condition includes a condition for removing a linear fundamental wave component included in the low-band received signal, and a weight value included in the weight value set for the condition is expressed by α _L1 β _It is assumed that _L1 + α _L2 β _L2 + α _L3 β _L3 +... + Α _LN β _LN = 0. According to the above configuration, the linear fundamental wave component included in the low-band received signal can be removed.

Preferably, the predetermined signal component is a nonlinear fundamental component included in each of the high-band received signal and the low-band received signal, and is included in the weight value set for extracting the nonlinear fundamental component. Weighting value is α _L1 ² β _H1 + α _L2 ² β _H2 + α _L3 ² β _H3 + ... + α _LN ² β _HN = 0, and α _H1 β _H1 + α _H2 β _H2 + α _H3 β _H3 + ... + α _{It is assumed that HN} β _HN = 0 and α _L1 β _L1 + α _L2 β _L2 + α _L3 β _L3 +... + Α _LN β _LN = 0. According to the above configuration, the second harmonic component due to the low-band transmission signal included in the high-band reception signal is removed, and the linear fundamental wave component included in each of the high-band reception signal and the low-band reception signal is removed. Thus, the nonlinear fundamental wave component included in each of the high band received signal and the low band received signal can be extracted.

  Desirably, the transmission to the first transmission focus point and the transmission to the second transmission focus point are executed with a time difference at each of the N multistage transmissions. According to the above configuration, it is possible to suppress the generation of the correlation signal component between the high-band transmission signal and the low-band transmission signal in the reception signal. That is, when transmission to the first transmission focus point and transmission to the second transmission focus point are performed simultaneously, a correlation signal component between the high-band transmission signal and the low-band transmission signal is generated as a result of high-order scattering. However, this can be avoided in the above configuration.

  Desirably, it further includes a transmission sound pressure uniforming means for setting a transmission condition according to the deflection angle of the ultrasonic beam so that the transmission sound pressure is uniform within the scanning plane of the ultrasonic beam, The transmission condition is set so that the transmitted sound pressure increases as the deflection angle increases. In the above configuration, the deflection angle is the angle of the ultrasonic beam with respect to the normal of the transducer surface of the probe that transmits and receives ultrasonic waves. According to the above configuration, a uniform image quality can be realized over the image plane of the ultrasonic image acquired corresponding to the scanning plane. More preferably, the transmission sound pressure uniform means corrects a transmission weight value for each transmission focus point by using a correction function g (φ) (φ is a deflection angle) for each transmission focus point of multi-stage focus transmission. The transmission conditions are set.

  A predetermined signal component can be extracted from the reception signal acquired by multistage focus transmission.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

FIG. 1 is a diagram for explaining transmission and reception of ultrasonic waves by the ultrasonic diagnostic apparatus of the present embodiment. The ultrasonic diagnostic apparatus according to the present embodiment controls the delay amount of each of the plurality of vibration elements 21 included in the probe 18, directs the ultrasonic beam in a predetermined direction, and sets the focal distance to a predetermined depth. It has a function to set. Then, for each ultrasonic beam direction 100, multistage focus transmission is executed for the two focal points, that is, the short-distance focal point 102 and the long-distance focal point 104. Is acquired. When performing multi-stage focus transmission, a high frequency pulse f _H is used for the short-distance focal point 102, and a low frequency pulse f _L is used for the long-distance focal point 104.

FIG. 2 shows a schematic diagram of the frequency spectrum of the ultrasonic wave transmitted and received by the ultrasonic diagnostic apparatus of the present embodiment, FIG. 2A shows the transmission spectrum, and FIG. Shows the reception spectrum. In both FIG. 2A and FIG. 2B, the horizontal axis represents frequency and the vertical axis represents power (energy). The probe band 110 indicates the transmittable / receiveable band of the probe 18 (FIG. 1), and the f _L band 112 and the f _H band 114 indicate the band of the low frequency pulse f _{L and} the band of the high frequency pulse f _H , respectively. Show. Further, the center frequency (fundamental frequency) of the low frequency pulse f _L is f ₁ , and the center frequency (fundamental wave frequency) of the high frequency pulse f _H is f ₂ (f ₁ <f ₂ ).

As shown in FIG. 2A, the f _H band 114 is set on the high frequency band side and the f _L band 112 is set on the low frequency band side with the vicinity of the center frequency of the probe band 110 as a boundary. . The f _H band 114 and the f _L band 112 may be overlapped with each other in the vicinity of the center frequency of the probe band 110. However, when the bands are overlapped, side lobes are generated. The f _H band 114 and the f _L band 112 are desirably set separately. The f _H band 114 and the f _L band 112 are formed with approximately the same bandwidth, and the center frequency f ₂ of the high frequency pulse f _H is set to a frequency that is approximately twice the center frequency f ₁ of the low frequency pulse f _L. . For example, when the probe band 110 is 6 MHz, f ₁ = 1.875 MHz and f ₂ = 3.75 MHz are set.

When the reception signal is acquired using the transmission spectrum shown in FIG. 2A, the reception spectrum shown in FIG. 2B is obtained. Since the transmission signal is set to be separated into the f _L band 112 and the f _H band 114, a reception signal corresponding to each band of the transmission signal is obtained. As a result, the reception spectrum also includes the f _L band 112 and the f _H band. Band 114 appears. However, the f _L band 112 of the reception spectrum includes a nonlinear fundamental wave component 122 due to the low frequency pulse f _L in addition to the linear fundamental wave component 120 due to the low frequency pulse f _L used for transmission. In addition, in the f _H band 114 of the reception spectrum, in addition to the linear fundamental wave component 120 by the high frequency pulse f _H used for transmission and the nonlinear fundamental wave component 122 by the high frequency pulse f _H , the second harmonic by the low frequency pulse f _L is used. A wave component 124 is included. The nonlinear fundamental wave component 122 and the second harmonic component 124 are signal components generated by nonlinear scattering. The reason is as follows.

数１で示される送信信号Ｔに対応する受信信号Ｒは、Ｔのｎ乗に比例するｎ次散乱波の散乱係数（比例係数）をａ_nとすると次式で示される。

なお、４次以上の散乱係数は比較的小さく無視できるため、数２では４次以上の散乱係数を０としている。数２に示すように、受信信号Ｒにおいて、１次散乱によって線形基本波成分が発生し、２次散乱によってＤＣ成分および２次高調波成分が発生し、さらに、３次散乱によって非線形基本波成分および３次高調波成分が発生する。線形基本波成分および非線形基本波成分は送信中心周波数と同じ周波数成分であり、２次高調波成分は送信中心周波数の２倍の周波数成分であり、３次高調波成分は送信中心周波数の３倍の周波数成分である。 In order to explain signal components generated by nonlinear scattering, the transmission signal T is modeled as follows.

The reception signal R corresponding to the transmission signal T expressed by Equation ₁ is represented by the following equation, where the scattering coefficient (proportional coefficient) of the nth-order scattered wave proportional to T to the nth power is represented by an.

Since the scattering coefficient of the fourth order or higher is relatively small and can be ignored, the scattering coefficient of the fourth order or higher is set to 0 in Equation 2. As shown in Equation 2, in the received signal R, a linear fundamental wave component is generated by the first-order scattering, a DC component and a second-order harmonic component are generated by the second-order scattering, and a nonlinear fundamental wave component is further generated by the third-order scattering. And third harmonic components are generated. The linear fundamental component and the nonlinear fundamental component are the same frequency components as the transmission center frequency, the second harmonic component is twice the frequency component of the transmission center frequency, and the third harmonic component is three times the transmission center frequency. Is the frequency component.

For this reason, as shown in FIG. 2B, in the f _L band 112 of the reception spectrum, in addition to the linear fundamental wave component 120 due to the low frequency pulse f _L used for transmission, the low frequency pulse f _L itself A nonlinear fundamental wave component 122 generated by third-order scattering is included. Further, the f _H band 114 of the reception spectrum includes a linear fundamental wave component 120 due to the high-frequency pulse f _H used for transmission and a nonlinear fundamental wave component 122 generated by the third-order scattering of the high-frequency pulse f _H itself. The second harmonic component 124 generated by the second order scattering of the low frequency pulse f _L is included. That is, since the center frequency f ₂ of the high frequency pulses f _H is set to twice the central frequency f ₁ of the low frequency pulse f _L, the secondary harmonic component generated by the secondary diffusion of the low frequency pulse f _L 124 Enters the f _H band 114. In this embodiment, the linear fundamental wave component 120 and the second harmonic component 124 are canceled by the method described below, and the nonlinear fundamental wave component 122 included in the reception spectrum is extracted.

  In the ultrasonic diagnostic apparatus of the present embodiment, multi-stage focus transmission is performed in the order of the far-distance focus 104 and the short-distance focus 102 for each ultrasonic beam direction 100 shown in FIG. 1, and this multi-stage focus transmission is performed. This is performed twice, and weighted addition is performed on the received signal obtained by the two transmissions.

FIG. 3 is a diagram for explaining two times of multi-stage focus transmission. In the first transmission, the low-frequency pulse f _L is transmitted to the long-distance focal point, and then the high-frequency pulse f _H is transmitted to the short-distance focal point, and the received signal is acquired. Furthermore, for the same ultrasonic beam direction, in the second transmission, the low frequency pulse f _L is transmitted to the far focus and then the high frequency pulse f _H is transmitted to the short focus. The received signal is obtained.

In the multi-stage focus transmission twice, the low frequency pulse f _L and the high frequency pulse f _H are each given a predetermined weight. In FIG. 3, the low-frequency pulse f _L and the high-frequency pulse f _H are both weighted “1” in the first transmission, and the low-frequency pulse f _L is weighted “0.707” in the second transmission. The high-frequency pulse f _H is weighted “0.5”. Further, the received signals obtained by the two transmissions are also weighted, and the weighted received signals are added. By setting predetermined conditions for the transmission weight value and the reception weight value, the nonlinear fundamental wave component is extracted by canceling the linear fundamental wave component and the second harmonic component in the weighted addition received signal. be able to.

  FIG. 4 is a diagram for explaining a weighting process for a transmission signal and a reception signal used for two-stage multi-focus transmission. FIG. 4 shows a process from generation of a transmission signal to weighting for the reception signal. Processing is shown.

FIG. 4I shows the first transmission / reception processing. f _L1 is a low-frequency pulse for long-distance focus in the first multistage focus transmission. The low-frequency pulse f _L1 is multiplied by a transmission weight coefficient α ₃ (S100), and an ultrasonic wave corresponding to the transmission signal α ₃ f _L1 subjected to the weighting process is transmitted to obtain a reception signal (S102). . Received signal R _L1 acquired as a result of transmission / reception is input to bandpass filters BPF _H and BPF _L and subjected to extraction processing of frequency components corresponding to the respective frequencies (S104 and S106). BPF _H is a band-pass filter that extracts a received signal component in the f _H band 114 (FIG. 2), and BPF _L is a band-pass filter that extracts a received signal component in the f _L band 112 (FIG. 2). Then, the output of BPF _H is multiplied by the reception weight coefficient β ₁ and the received signal BPF _H (R _L1 ) subjected to the weighting process is output (S108). Further, the output of BPF _L is multiplied by the reception weight coefficient β ₃ and the received signal BPF _L (R _L1 ) subjected to the weighting process is output (S110).

On the other hand, f _H1 is a high-frequency pulse for short-distance focus in the first multistage focus transmission. The high-frequency pulse f _H1 is multiplied by a transmission weight coefficient α ₁ (S100 ′), and an ultrasonic wave corresponding to the weighted transmission signal α ₁ f _H1 is transmitted to acquire a reception signal (S102 ′). ). Received signal R _H1 acquired as a result of transmission / reception is input to bandpass filters BPF _H and BPF _L , and frequency component extraction processing corresponding to each frequency is performed (S104 ′ and S106 ′). Then, the output of BPF _H is multiplied by the reception weight coefficient β ₁ and the received signal BPF _H (R _H1 ) subjected to the weighting process is output (S108 ′). Further, the output of BPF _L is multiplied by the reception weight coefficient β ₃ and the received signal BPF _L (R _H1 ) subjected to the weighting process is output (S110 ′).

FIG. 4 (II) shows the second transmission / reception processing. f _L2 is a low-frequency pulse for long-distance focus in the second multistage focus transmission. The low-frequency pulse f _L2 is multiplied by a transmission weight coefficient α ₄ (S200), and an ultrasonic wave corresponding to the weighted transmission signal α ₄ f _L2 is transmitted to obtain a reception signal (S202). . Received signal R _L2 obtained as a result of transmission / reception is input to bandpass filters BPF _H and BPF _L , and frequency component extraction processing corresponding to each frequency is performed (S204 and S206). Then, the output of BPF _H is multiplied by the reception weight coefficient β ₂ and the received signal BPF _H (R _L2 ) subjected to the weighting process is output (S208). Further, the output of BPF _L is multiplied by the reception weight coefficient β ₄ and the received signal BPF _L (R _L2 ) subjected to the weighting process is output (S210).

On the other hand, f _H2 is a high-frequency pulse for short-distance focus in the second multistage focus transmission. The high-frequency pulse f _H2 is multiplied by a transmission weight coefficient α ₂ (S200 ′), and an ultrasonic wave corresponding to the weighted transmission signal α ₂ f _H2 is transmitted to obtain a reception signal (S202 ′). ). The received signal R _H2 acquired as a result of the transmission / reception wave is input to the band pass filters BPF _H and BPF _L and subjected to extraction processing of frequency components corresponding to the respective frequencies (S204 ′ and S206 ′). Then, the output of BPF _H is multiplied by the reception weight coefficient β ₂ and the received signal BPF _H (R _H2 ) subjected to the weighting process is output (S208 ′). Further, the output of BPF _L is multiplied by the reception weight coefficient β _4, and the received signal BPF _L (R _H2 ) subjected to the weighting process is output (S210 ′).

In the first transmission / reception processing shown in FIG. 4I, when f _L1 = A cos θ _L and f _H1 = A cos θ _H , the received signal BPF _H (R _L1 ) and the received signal BPF _L (R _L1 ) are Is calculated as follows. It is assumed that the center frequency of the high frequency pulse is approximately twice the center frequency of the low frequency pulse, that is, the relationship θ _H = 2 × θ _L is established.

なお、４次以上の散乱係数は比較的小さく無視できるため、数３では４次以上の散乱係数を０としている。 Since the low-frequency pulse f _L1 for far-distance focus is multiplied by the transmission weight coefficient α ₃ , an ultrasonic wave corresponding to the transmission signal α _{3 A} cos θ _L is transmitted. Received signal R _L1 corresponding to this transmission signal, the n-th order scattering coefficient (proportional coefficient) and a _n represented by the following formula.

Since the scattering coefficient of the fourth order or higher is relatively small and can be ignored, the scattering coefficient of the fourth order or higher is set to 0 in Equation 3.

As for the received signal R _L1 shown in Equation 3, components in the f _H band are extracted from the BPF _H. As a result, the second harmonic component of the received signal R _L1 is extracted. That is, BPF _H is a band-pass filter that extracts a signal in the f _H band and satisfies the relationship θ _H = 2 × θ _L , so that the second harmonic component of the received signal R _L1 is f. _This is because it appears in the _H band. Further, a linear fundamental wave component and a nonlinear fundamental wave component are extracted from the received signal R _L1 in BPF _L. Therefore, the received signals BPF _H (R _L1 ) and BPF _L (R _L1 ) that have been subjected to the weighting process are respectively expressed by the following equations.

なお、４次以上の散乱係数は比較的小さく無視できるため、数５では４次以上の散乱係数を０としている。 On the other hand, since the transmission weight coefficient α ₁ is multiplied by the short-distance focus high-frequency pulse f _H1 , an ultrasonic wave corresponding to the transmission signal α _{1 A} cos θ _H is transmitted. Received signal R _H1 corresponding to the transmission signal, the n-th order scattering coefficient (proportional coefficient) and a _n represented by the following formula.

Since the scattering coefficient of the fourth order or higher is relatively small and can be ignored, the scattering coefficient of the fourth order or higher is set to 0 in Equation 5.

このように、１回目の送受波によって、数４および数６に示される受信信号が得られる。 From the received signal R _H1 shown in Equation 5, the component in the f _H band is extracted from the BPF _H. As a result, the linear fundamental wave component and the nonlinear fundamental wave component of the received signal R _H1 are extracted. Further, since there is no frequency component in the f _L band in the received signal R _H1 , the output of BPF _L is zero. Therefore, the received signals BPF _H (R _H1 ) and BPF _L (R _H1 ) that have been subjected to the weighting process are respectively expressed by the following equations.

Thus, the received signals shown in Equations 4 and 6 are obtained by the first transmission / reception wave.

Next, in the second transmission / reception processing shown in FIG. 4 (II), if f _L2 = A cos θ _L and f _H2 = A cos θ _H , the reception signal BPF _H (R _L2 ) and the reception signal BPF _L (R _L2 ) Is calculated as follows. It is assumed that the center frequency of the high frequency pulse is approximately twice the center frequency of the low frequency pulse, that is, the relationship θ _H = 2 × θ _L is established.

なお、４次以上の散乱係数は比較的小さく無視できるため、数７では４次以上の散乱係数を０としている。 Since the low-frequency pulse f _L2 for far-distance focus is multiplied by the transmission weight coefficient α ₄ , an ultrasonic wave corresponding to the transmission signal α _{4 A} cos θ _L is transmitted. Received signal R _L2 corresponding to the transmission signal, the n-th order scattering coefficient (proportional coefficient) and a _n represented by the following formula.

Since the scattering coefficient of the fourth order or higher is relatively small and can be ignored, the scattering coefficient of the fourth order or higher is set to 0 in Equation 7.

As for the received signal R _L2 shown in Expression 7, components in the f _H band are extracted from the BPF _H. As a result, the second harmonic component of the received signal R _L2 is extracted. That is, BPF _H is a band-pass filter that extracts a signal in the f _H band and satisfies the relationship θ _H = 2 × θ _L , so that the second harmonic component of the received signal R _L2 is f. _This is because it appears in the _H band. Further, a linear fundamental wave component and a nonlinear fundamental wave component are extracted from the reception signal R _L2 at BPF _L. Therefore, the received signals BPF _H (R _L2 ) and BPF _L (R _L2 ) that have been subjected to the weighting process are respectively expressed by the following equations.

なお、４次以上の散乱係数は比較的小さく無視できるため、数９では４次以上の散乱係数を０としている。 On the other hand, since the transmission weight coefficient α ₂ is multiplied by the short-distance focus high-frequency pulse f _H2 , an ultrasonic wave corresponding to the transmission signal α _{2 A} cos θ _H is transmitted. The received signal R _H2 corresponding to the transmission signal, shown n the following scattering coefficient (proportional coefficient) by the following equation When a _n.

Since the scattering coefficient of the fourth order or higher is relatively small and can be ignored, the scattering coefficient of the fourth order or higher is set to 0 in Equation 9.

このように、２回目の送受波によって、数８および数１０に示される信号が得られる。 From the received signal R _H2 shown in Equation 9, the component in the f _H band is extracted from the BPF _H. As a result, the linear fundamental wave component and the nonlinear fundamental wave component of the received signal R _H2 are extracted. Further, since there is no frequency component in the f _L band in the received signal R _H2 , the output of BPF _L is 0. Therefore, the received signals BPF _H (R _H2 ) and BPF _L (R _H2 ) that have been subjected to the weighting process are respectively expressed by the following equations.

In this way, the signals shown in Equations 8 and 10 are obtained by the second transmission / reception wave.

Table 1 summarizes the received signals after the weighting processing shown in Equations 4, 6, 8, and 10 for each component in the f _H band and the f _L band.

つまり、これらの加算結果が０となれば、線形基本波成分および２次高調波成分がキャンセルされて非線形基本波成分のみが残ることになる。その条件を満たす重み係数は次式の関係を満たすことになる。

In the present embodiment, the reception signal obtained by the first transmission / reception wave and the reception signal obtained by the second transmission / reception wave are added to extract a nonlinear fundamental wave component in both the f _H band and the f _L band. In the f _H band, in addition to the nonlinear fundamental wave component, a linear fundamental wave component and a second harmonic component exist. When the first received signal and the second received signal are added, the linear fundamental wave component and the second harmonic component in the f _H band are expressed by the following equations, respectively.

That is, if these addition results are 0, the linear fundamental wave component and the second harmonic component are canceled and only the nonlinear fundamental wave component remains. The weighting coefficient that satisfies the condition satisfies the relationship of the following equation.

つまり、この加算結果が０となれば、線形基本波成分がキャンセルされて非線形基本波成分のみが残ることになり、その条件を満たす重み係数は次式の関係を満たすことになる。

On the other hand, a linear fundamental wave component exists in the f _L band in addition to the nonlinear fundamental wave component. When the first received signal and the second received signal are added, the linear fundamental wave component in the f _L band is expressed by the following equation.

That is, when this addition result is 0, the linear fundamental wave component is canceled and only the nonlinear fundamental wave component remains, and the weighting coefficient that satisfies the condition satisfies the relationship of the following equation.

つまり、送信の重み付け値および受信の重み付け値に対して、数１５の条件設定を行うことによって、重み付け加算された受信信号において、線形基本波成分および２次高調波成分をキャンセルして非線形基本波成分を抽出することができる。なお、数１５の条件式を満足する重み付け値の具体例を表２に示す。

From the above, the conditions for leaving only the nonlinear fundamental wave component in both the f _H band and the f _L band are summarized as follows.

That is, by setting the condition of Equation 15 for the transmission weight value and the reception weight value, the linear fundamental wave component and the second harmonic component are canceled in the weighted addition received signal, and the nonlinear fundamental wave is cancelled. Ingredients can be extracted. Table 2 shows specific examples of weighting values that satisfy the conditional expression (15).

  In the above, the weighting process with respect to the transmission signal and reception signal used for two multistage focus transmission was demonstrated. Next, the configuration of the ultrasonic diagnostic apparatus of this embodiment will be described.

  FIG. 5 is a block diagram showing the overall configuration of the ultrasonic diagnostic apparatus of the present embodiment. The ultrasonic diagnostic apparatus shown in FIG. 5 acquires a reception signal by executing multi-stage focus transmission twice for two depths (focal lengths) of the short distance focus and the long distance focus for each ultrasonic beam direction.

The transmission pulse f _H generator 10 is a circuit that generates a high-frequency pulse f _H for short-distance focus. In the first multi-stage focus transmission, the high-frequency pulse f _H is multiplied by a transmission weight value α ₁ and output, and then the second time. In multi-stage focus transmission, the high-frequency pulse f _H is multiplied by a transmission weight value α ₂ and output. The transmission pulse f _L generator 12 is a circuit that generates a low-frequency pulse f _L for long-distance focusing. In the first multistage focus transmission, the low-frequency pulse f _L is multiplied by a transmission weight value α ₃ and output. In the second multistage focus transmission, the low frequency pulse f _L is multiplied by the transmission weighting value α ₄ and output. Note that the transmission weight values α ₁ , α ₂ , α ₃ , and α ₄ are set so as to satisfy Formula 15, for example, set to the values shown in Table 2.

  The transmission delay circuit 14 is a circuit that outputs a drive signal corresponding to each of the plurality of transducers included in the probe 18, and each drive signal is subjected to a delay process corresponding to the corresponding transducer. The transmission delay circuit 14 controls the amount of delay for each drive signal, and changes the beam direction and focal length of the transmission beam output from the probe 18. Each drive signal output from the transmission delay circuit 14 is amplified by the transmission driver 16 and supplied to the probe 18. The probe 18 transmits an ultrasonic wave corresponding to each drive signal output from the transmission driver 16, acquires an echo from the living body, and outputs a reception signal.

The transmission to the short-distance focus and the long-distance focus for each multi-stage focus transmission is performed with a time difference so that the high-frequency pulse f _H and the low-frequency pulse f _L do not overlap. This is due to the following reason.

数１６に示すように、ｃｏｓθ_Hｃｏｓθ_Lの相関項から、ｃｏｓ（θ_H＋θ_L）とｃｏｓ（θ_H−θ_L）の角周波数成分が発生する。つまり、高周波パルスｆ_Hと低周波パルスｆ_Lが重ねられて送波されると、非線形散乱によって、非線形基本波成分や高調波成分の他に送信周波数の和成分や差成分が発生してしまう。なお、ｎ＝３の場合はｃｏｓθ_H ²ｃｏｓθ_Lなどの相関項も発生する。そのため、本実施形態では、相関の散乱波が音場において０に近くなるように、高周波パルスｆ_Hと低周波パルスｆ_Lに時間差を設けて送波し、相関項の発生を抑えている。この時間差は画像合成回路４２において補正される。 RF pulses f _H and a low frequency pulse f _L respectively f _H = A _H cosθ _H, When f _L = A _L cosθ _L, transmits the high frequency pulses f _H and a low frequency pulse f _L are stacked are transmitting at the same time signal T becomes _{T = a H cosθ H + a} L cosθ L. As described using Equation 2, as a result of nonlinear scattering, the received signal includes the n-th term of the transmission signal T. For example, considering a square term (n = 2), T ² is calculated as follows:

As shown in several 16, cos [theta] from the correlation section _H cos [theta] _L, the angular frequency component of the cos (θ _H + θ _L) and cos (θ _H -θ _L) is generated. That is, when the high-frequency pulse f _H and the low-frequency pulse f _L are superimposed and transmitted, non-linear scattering generates a sum component or difference component of the transmission frequency in addition to the non-linear fundamental wave component and the harmonic component. . When n = 3, a correlation term such as cos θ _H ² cos θ _L is also generated. Therefore, in this embodiment, the high-frequency pulse f _H and the low-frequency pulse f _L are transmitted with a time difference so that the correlation scattered wave is close to 0 in the sound field, thereby suppressing the generation of the correlation term. This time difference is corrected in the image composition circuit 42.

The reception signal for each transducer output from the probe 18 is amplified by the reception amplifier 22 and supplied to the reception phasing addition circuit 24. The reception phasing addition circuit 24 performs phasing addition processing on a plurality of reception signals obtained for each transducer. The received signal subjected to the phasing addition processing is supplied to the bandpass filters BPF _H 26 and BPF _L 28. BPF _H is a band-pass filter that extracts a received signal component in the f _H band 114 (FIG. 2), and BPF _L is a band-pass filter that extracts a received signal component in the f _L band 112 (FIG. 2).

The line buffers 30 and 32 function as a delay buffer for one line. That is, the reception signal by the first transmission in the two multi-stage focus transmissions is stored in the line buffer 30 or the line buffer 32, and when the reception signal is acquired by the second transmission, the line buffer 30 or the line buffer The reception signal by the first transmission stored in 32 is supplied to the weighting addition circuit 34 or the weighting addition circuit 36, while the reception signal by the second transmission is sent from the bandpass filter BPF _H 26 or BPF _L 28. Directly supplied to the weighted addition circuit 34 or the weighted addition circuit 36.

The weighted addition circuit 34 multiplies the _first received signal supplied from the BPF _H 26 via the line buffer 30 by the reception weight value β ₁ , and applies the second received signal directly supplied from the BPF _H 26 to the second received signal. The received weight value β ₂ is multiplied by the weighted addition for the first and second received signals and supplied to the detector 38. On the other hand, the weighted addition circuit 36 multiplies the first received signal supplied from the BPF _L 28 via the line buffer 32 by the reception weighting value β _3, and receives the second received signal directly supplied from the BPF _L 28. The signal is multiplied by the reception weight value β ₄ , weighted addition is performed on the first and second received signals, and the result is supplied to the detector 40. The received signals subjected to the weighted addition are subjected to envelope detection in the detectors 38 and 40. Note that the values of the reception weight values β ₁ , β ₂ , β ₃ , and β ₄ are set so as to satisfy Formula 15, and are set to the values shown in Table 2, for example. As a result, as described with reference to FIG. 4, the linear fundamental wave component and the second harmonic component are canceled and the nonlinear fundamental wave component is extracted. Then, the image synthesis circuit 42 generates image data by multistage synthesis of the nonlinear fundamental wave components of the f _H band and the f _L band, and the display unit 44 displays an ultrasonic image based on the image data.

  This embodiment is suitable for, for example, visualization of blood flow using an ultrasound contrast agent. In other words, since nonlinear scattering characteristics are used, it is possible to visualize a minute blood flow that is buried in echoes from surrounding tissues with only a linear scattering component. Further, since the nonlinear fundamental wave component is used, both transmission and reception can be performed in the fundamental wave band, and a narrow-band probe can be used.

  In the present embodiment, it is also possible to set transmission conditions such as transmission gain, aperture, window function, etc. according to the transmission beam so that the transmitted sound pressure (sound field) is uniform.

  FIG. 6 is a diagram for explaining the relationship between the deflection angle and the transmitted sound pressure, and FIG. 6A shows how the transmitted sound pressure changes depending on the deflection angle. In the scanning of the electron deflection (sector) probe, the sound pressure of the transmitted wave decreases (for example, decreases by several dB) as the scanning deflection angle φ, that is, the deflection angle φ of the transmission beam increases. Here, the deflection angle φ is an angle between the normal line of the transducer surface of the probe and the transmission beam. Further, even if the deflection angle φ is the same, the higher the transmission frequency, the greater the degree of sound pressure reduction. In addition to the change due to the deflection angle φ, for example, the degree of decrease in sound pressure also changes depending on the focal length. The degree of such a change in the transmitted sound pressure is known in advance through experiments and simulations, and the transmission conditions are set so as to cancel the change.

  FIG. 6B shows the correction amount of the transmitted sound pressure corresponding to the deflection angle φ. That is, the correction amount for canceling the change in the transmitted sound pressure shown in FIG. 6A and making the transmitted sound pressure uniform in the scanning plane is shown.

The sound pressure correction circuit 50 in FIG. 5 is a circuit that corrects the transmitted sound pressure. The sound pressure correction circuit 50 corrects the transmission gain for each transmission focus point by using the functions g _H (φ) and g _L (φ) for correction corresponding to each of the short distance focus and the long distance focus. I do. Here, the functions g _H (φ) and g _L (φ) are, for example, functions shown in FIG. Based on the functions g _H (φ) and g _L (φ) output from the sound pressure correction circuit 50, the transmission driver 16 adjusts the transmission gain for each transmission focus point with a correction amount corresponding to the deflection angle φ. Make corrections. As a result, the transmitted sound pressure becomes uniform, and a uniform image is realized over the image plane of the ultrasonic image.

The transmission gain may be corrected for the transmission weight values α ₁ , α ₂ , α ₃ , α ₄ in the transmission pulse f _H generator 10 and the transmission pulse f _L generator 12. That is, the transmission pulse f _H generator 10 and the transmission pulse f _L generator 12 transmit the transmission weight values g _H α ₁ , g according to the deflection angle φ based on the functions g _H (φ), g _L (φ). _H α ₂ , g _L α ₃ , and g _L α ₄ may be set.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to two multistage focus transmissions. Further, it is possible to extend the transmission so that transmission is performed N times (N is an integer of 2 or more) for each transmission focus point. In order to expand to N multi-stage focus transmission, the transmission weight value in the Nth transmission to the near focus is α _HN (generalization of α ₁ and α ₂ ), and the Nth transmission to the far focus. _Let α _LN (generalization of α ₃ and α ₄ ) be the transmission weight value in. The reception weight value for the output from the BPF _H by the Nth transmission is β _HN (generalization of β ₁ and β ₂ ), and the reception weight value for the output from the BPF _L by the Nth transmission is β _LN (Generalization of β ₃ and β ₄ ). Then, in accordance with the calculation method using Equations 3 to 10, the received signal after weighting processing corresponding to the Nth transmission is calculated, and the calculation result is classified into each component of the f _H band and the f _L band. Then, Table 3 which generalized Table 1 is obtained.

つまり、Ｎ回の多段フォーカス送信における送信の重み付け値および受信の重み付け値に対して、数１７の条件設定を行うことによって、重み付け加算された受信信号において、線形基本波成分および２次高調波成分をキャンセルして非線形基本波成分を抽出することができる。 A conditional expression for extracting nonlinear fundamental wave components in both the f _H band and the f _L band by adding the received signals obtained in each round is generalized as shown in the following expression.

That is, by setting the condition of Equation 17 for the transmission weight value and the reception weight value in N multi-stage focus transmissions, the linear fundamental wave component and the second harmonic component in the weighted received signal are set. Can be canceled to extract a nonlinear fundamental wave component.

  FIG. 7 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus that performs three-stage multi-focus transmission. The ultrasonic diagnostic apparatus in FIG. 7 is obtained by extending the one in FIG. 5 to three-stage multi-focus transmission, and parts that perform operations similar to those in FIG. 5 are denoted by the same reference numerals as in FIG. Yes. In the following, the description will focus on the differences from the ultrasonic diagnostic apparatus shown in FIG.

Transmission pulse f _H generator 10 'is a circuit that generates a high-frequency pulses f _H for short distance focus, and outputs multiplied by the high frequency pulse f transmit weighting values to _H alpha _H1 in first multi-stage focusing transmission, second In the multi-stage focus transmission, the high-frequency pulse f _H is multiplied by the transmission weight value α _H2 and output, and in the third multi-stage focus transmission, the high-frequency pulse f _H is multiplied by the transmission weight value α _H3 and output. The transmission pulse f _L generator 12 ′ is a circuit that generates a low-frequency pulse f _L for long-distance focusing. In the first multistage focus transmission, the low-frequency pulse f _L is multiplied by a transmission weight value α _L1 and output. In the second multistage focus transmission, the low frequency pulse f _L is output with the transmission weight value α _L2 , and in the third multistage focus transmission, the low frequency pulse f _L is output with the transmission weight value α _L2. To do.

A drive signal is supplied to the probe 18 via the transmission delay circuit 14 and the transmission driver 16 by the same operation as the ultrasonic diagnostic apparatus shown in FIG. 5, and the received signal acquired by the probe 18. Is subjected to predetermined processing in the reception amplifier 22 and the reception phasing addition circuit 24 and then passes through the band-pass filters BPF _H 26 and BPF _L 28.

Each of the line buffers 30a, 30b, and 30c functions as a delay buffer for one line. That is, the received signal by the first transmission output from the BPF _H 26 is stored in the line buffer 30a, and when the received signal is acquired by the second transmission, the first signal stored in the line buffer 30a is stored. A reception signal by the transmission is stored in the line buffer 30b, and a reception signal by the second transmission is stored in the line buffer 30c. When the reception signal is acquired by the third transmission, the reception signal by the first transmission stored in the line buffer 30b, the reception signal by the second transmission stored in the line buffer 30c, and A reception signal by the third transmission output from the BPF _H 26 is supplied to the weighted addition circuit 34 ′.

The weighting addition circuit 34 'multiplies the first received signal supplied from the line buffer 30b by the reception weight value _βH1, and the second received signal supplied from the line buffer 30c receives the reception weight value _βH2. The third received signal supplied directly from the BPF _H 26 is multiplied by the reception weight value β _H3 , and weighted addition is performed on the first, second and third received signals, and the detector 38 is added. To supply.

Each of the line buffers 32a, 32b, and 32c functions as a delay buffer for one line. That is, the received signal by the first transmission output from the BPF _L 28 is stored in the line buffer 32a, and when the received signal is acquired by the second transmission, the first signal stored in the line buffer 32a is stored. A reception signal by the transmission is stored in the line buffer 32b, and a reception signal by the second transmission is stored in the line buffer 32c. Then, when the reception signal is acquired by the third transmission, the reception signal by the first transmission stored in the line buffer 32b, the reception signal by the second transmission stored in the line buffer 32c, and A reception signal generated by the third transmission output from the BPF _L 28 is supplied to the weighted addition circuit 36 ′.

The weighting addition circuit 36 ′ multiplies the first received signal supplied from the line buffer 32b by the reception weight value β _L1 and receives the second received signal supplied from the line buffer 32c to the reception weight value β _L2. The third received signal directly supplied from the BPF _L 28 is multiplied by the reception weight value β _L3 , and the weighted addition is performed on the first, second, and third received signals, thereby detecting the detector 40. To supply. The received signals subjected to the weighted addition are subjected to envelope detection in the detectors 38 and 40.

The transmission weight values α _H1 , α _H2 , α _H3 , α _L1 , α _L2 , α _L3 , and the reception weight values β _H1 , β _H2 , β _H3 , β _L1 , β _L2 , β _L3 are given by It is set to satisfy the conditional expression. That is, the condition is set so as to satisfy the conditional expression when N = 3 in Equation 17 (for example, set to the value shown in Table 4), and as a result, the nonlinear fundamental wave component is extracted by weighted addition. Then, the image synthesis circuit 42 generates image data by multistage synthesis of the nonlinear fundamental wave components of the f _H band and the f _L band, and the display unit 44 displays an ultrasonic image based on the image data.

Although FIG. 7 shows the overall configuration of an ultrasonic diagnostic apparatus that performs multi-stage focus transmission three times, it can be easily expanded to an ultrasonic diagnostic apparatus that performs multi-stage focus transmission four or more times. That is, the transmission pulse f _H generator 10 ′, the transmission pulse f _L generator 12 ′, the line buffers 30a, 30b, 30c, 32a, 32b, and 32c, and the weighted addition circuits 34 ′ and 36 ′ are transmitted four or more times. What is necessary is just to modify suitably according to a wave. By increasing the number of multi-stage focus transmissions, for example, clutter can be reduced.

It is a figure for demonstrating the transmission / reception of the ultrasonic wave by suitable embodiment of this invention. It is the schematic of the frequency spectrum of the ultrasonic wave transmitted / received by the ultrasonic diagnosing device of this embodiment. It is a figure for demonstrating two times multistage focus transmission. It is a figure for demonstrating the weighting process in this embodiment. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a figure for demonstrating the relationship between a deflection angle and a transmitted sound pressure. It is a block diagram which shows the whole structure of the ultrasound diagnosing device which performs 3 times multistage focus transmission.

Explanation of symbols

10 transmission pulse f _H generator, 12 transmission pulse f _L generator, 34, 36 weighted addition circuit, 50 sound pressure correction circuit.

Claims (7)

In an ultrasonic diagnostic apparatus that performs multi-stage transmission N times (N is an integer of 2 or more) as multi-stage focus transmission, including transmission to the first transmission focus point and transmission to the second transmission focus point.
A transmission signal generator for generating a low-band transmission signal in a low-frequency band corresponding to the second transmission focus point, and generating a high-band transmission signal in a high-frequency band corresponding to the first transmission focus point;
A first transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the first transmission focus point in the N multistage transmissions. _H1 , Α _H2 , ..., α _HN }, A first transmission processing means for performing transmission weighting on the N multi-stage transmissions,
A second transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the second transmission focus point in the N multistage transmissions. _L1 , Α _L2 , ..., α _LN }, A second transmission processing means for performing transmission weighting on the N multi-stage transmissions,
Using the high-frequency band-pass filter and the low-frequency band-pass filter, a received signal acquired N times corresponding to each of the N multistage transmissions is converted into a high-band received signal and A received signal sorting unit for sorting into low-band received signals;
A first reception weight value set {β including N reception weight values corresponding to each of the high-band reception signals acquired N times _H1 , Β _H2 , ..., β _HN }, A first reception processing means for performing reception weighting addition on the high-band reception signal acquired N times,
A second reception weight value set {β including N reception weight values corresponding to each of the low-band reception signals acquired N times _L1 , Β _L2 , ..., β _LN }, A second reception processing means for performing reception weighting addition on the low-band received signal acquired N times,
Have
A set of weight values composed of the first transmission weight value set, the second transmission weight value set, the first reception weight value set, and the second reception weight value set is assigned to the high-band reception signal and the low-band reception signal. Satisfy the extraction conditions for extracting the predetermined signal components included,
The extraction condition includes a condition for removing a second harmonic component due to the low-band transmission signal included in the high-band received signal, and a weight value included in the weight value set for the condition is ,
α _L1 ² β _H1 + Α _L2 ² β _H2 + Α _L3 ² β _H3 + ... + α _LN ² β _HN = 0,
An ultrasonic diagnostic apparatus. In an ultrasonic diagnostic apparatus that performs multi-stage transmission N times (N is an integer of 2 or more) as multi-stage focus transmission, including transmission to the first transmission focus point and transmission to the second transmission focus point.
A transmission signal generator for generating a low-band transmission signal in a low-frequency band corresponding to the second transmission focus point, and generating a high-band transmission signal in a high-frequency band corresponding to the first transmission focus point;
A first transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the first transmission focus point in the N multistage transmissions. _H1 , Α _H2 , ..., α _HN }, A first transmission processing means for performing transmission weighting on the N multi-stage transmissions,
A second transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the second transmission focus point in the N multistage transmissions. _L1 , Α _L2 , ..., α _LN }, A second transmission processing means for performing transmission weighting on the N multi-stage transmissions,
Using the high-frequency band-pass filter and the low-frequency band-pass filter, a received signal acquired N times corresponding to each of the N multistage transmissions is converted into a high-band received signal and A received signal sorting unit for sorting into low-band received signals;
A first reception weight value set {β including N reception weight values corresponding to each of the high-band reception signals acquired N times _H1 , Β _H2 , ..., β _HN }, A first reception processing means for performing reception weighting addition on the high-band reception signal acquired N times,
A second reception weight value set {β including N reception weight values corresponding to each of the low-band reception signals acquired N times _L1 , Β _L2 , ..., β _LN }, A second reception processing means for performing reception weighting addition on the low-band received signal acquired N times,
Have
A set of weight values composed of the first transmission weight value set, the second transmission weight value set, the first reception weight value set, and the second reception weight value set is assigned to the high-band reception signal and the low-band reception signal. Satisfy the extraction conditions for extracting the predetermined signal components included,
The extraction condition includes a condition for removing a linear fundamental wave component included in the high-band received signal, and a weight value included in the weight value set for the condition is:
α _H1 β _H1 + Α _H2 β _H2 + Α _H3 β _H3 + ... + α _HN β _HN = 0,
An ultrasonic diagnostic apparatus. In an ultrasonic diagnostic apparatus that performs multi-stage transmission N times (N is an integer of 2 or more) as multi-stage focus transmission, including transmission to the first transmission focus point and transmission to the second transmission focus point.
A transmission signal generator for generating a low-band transmission signal in a low-frequency band corresponding to the second transmission focus point, and generating a high-band transmission signal in a high-frequency band corresponding to the first transmission focus point;
A first transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the first transmission focus point in the N multistage transmissions. _H1 , Α _H2 , ..., α _HN }, A first transmission processing means for performing transmission weighting on the N multi-stage transmissions,
A second transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the second transmission focus point in the N multistage transmissions. _L1 , Α _L2 , ..., α _LN }, A second transmission processing means for performing transmission weighting on the N multi-stage transmissions,
Using the high-frequency band-pass filter and the low-frequency band-pass filter, a received signal acquired N times corresponding to each of the N multistage transmissions is converted into a high-band received signal and A received signal sorting unit for sorting into low-band received signals;
A first reception weight value set {β including N reception weight values corresponding to each of the high-band reception signals acquired N times _H1 , Β _H2 , ..., β _HN }, A first reception processing means for performing reception weighting addition on the high-band reception signal acquired N times,
A second reception weight value set {β including N reception weight values corresponding to each of the low-band reception signals acquired N times _L1 , Β _L2 , ..., β _LN }, A second reception processing means for performing reception weighting addition on the low-band received signal acquired N times,
Have
A set of weight values composed of the first transmission weight value set, the second transmission weight value set, the first reception weight value set, and the second reception weight value set is assigned to the high-band reception signal and the low-band reception signal. Satisfy the extraction conditions for extracting the predetermined signal components included,
The extraction condition includes a condition for removing a linear fundamental wave component included in the low-band received signal, and a weighting value included in the weighting value set for the condition includes:
α _L1 β _L1 + Α _L2 β _L2 + Α _L3 β _L3 + ... + α _LN β _LN = 0,
An ultrasonic diagnostic apparatus. In an ultrasonic diagnostic apparatus that performs multi-stage transmission N times (N is an integer of 2 or more) as multi-stage focus transmission, including transmission to the first transmission focus point and transmission to the second transmission focus point.
A transmission signal generator for generating a low-band transmission signal in a low-frequency band corresponding to the second transmission focus point, and generating a high-band transmission signal in a high-frequency band corresponding to the first transmission focus point;
A first transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the first transmission focus point in the N multistage transmissions. _H1 , Α _H2 , ..., α _HN }, A first transmission processing means for performing transmission weighting on the N multi-stage transmissions,
A second transmission weight value set {α including N transmission weight values corresponding to each of N transmissions to the second transmission focus point in the N multistage transmissions. _L1 , Α _L2 , ..., α _LN }, A second transmission processing means for performing transmission weighting on the N multi-stage transmissions,
Using the high-frequency band-pass filter and the low-frequency band-pass filter, a received signal acquired N times corresponding to each of the N multistage transmissions is converted into a high-band received signal and A received signal sorting unit for sorting into low-band received signals;
A first reception weight value set {β including N reception weight values corresponding to each of the high-band reception signals acquired N times _H1 , Β _H2 , ..., β _HN }, A first reception processing means for performing reception weighting addition on the high-band reception signal acquired N times,
A second reception weight value set {β including N reception weight values corresponding to each of the low-band reception signals acquired N times _L1 , Β _L2 , ..., β _LN }, A second reception processing means for performing reception weighting addition on the low-band received signal acquired N times,
Have
A set of weight values composed of the first transmission weight value set, the second transmission weight value set, the first reception weight value set, and the second reception weight value set is assigned to the high-band reception signal and the low-band reception signal. Satisfy the extraction conditions for extracting the predetermined signal components included,
The predetermined signal component is a nonlinear fundamental wave component included in each of the high-band received signal and the low-band received signal, and a weighting value included in the weighting value set is used to extract the nonlinear fundamental wave component. ,
α _L1 ² β _H1 + Α _L2 ² β _H2 + Α _L3 ² β _H3 + ... + α _LN ² β _HN = 0 and
α _H1 β _H1 + Α _H2 β _H2 + Α _H3 β _H3 + ... + α _HN β _HN = 0 and
α _L1 β _L1 + Α _L2 β _L2 + Α _L3 β _L3 + ... + α _LN β _LN = 0,
An ultrasonic diagnostic apparatus. In the ultrasonic diagnostic apparatus according to any one of claims 1 to 4,
The transmission to the first transmission focus point and the transmission to the second transmission focus point are executed with a time difference for each of the N multistage transmissions.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 5,
A transmission sound pressure uniform means for setting a transmission condition according to the deflection angle of the ultrasonic beam so that the transmission sound pressure is uniform in the scanning plane of the ultrasonic beam;
The transmitted sound pressure uniform means sets the transmission conditions so that the transmitted sound pressure increases as the deflection angle increases.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 6,
The transmission sound pressure uniforming means corrects a transmission weight value for each transmission focus point by using a correction function g (φ) (φ is a deflection angle) for each transmission focus point of multistage focus transmission, and transmits the transmission. Set conditions,
An ultrasonic diagnostic apparatus.

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