JP4599408B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus including an ultrasonic array including a large number of electroacoustic transducers, and more particularly to an ultrasonic diagnostic apparatus having a first reception beamformer and a second reception beamformer.

  Electroacoustic transducers are arranged in a two-dimensional array to measure spatial and temporal four-dimensional ultrasonic echoes, such as measuring three-dimensional blood flow in the coronary arteries of the heart and measuring stroke volume. In order to obtain a desired resolution, it is necessary to use a two-dimensional array in which thousands of electroacoustic transducers are arranged. A signal obtained from each electroacoustic transducer is subjected to a phasing process for focusing on a certain point in the imaging space by a reception beamformer. However, since a receiving beamformer having inputs of several thousand channels is not realistic in terms of apparatus scale and cost, it is necessary to reduce the number of channels to about 100 to 200 channels. In this case, it is desirable to use as many signals from the electroacoustic transducer as possible in order to obtain sufficient received signal power.

  Therefore, conventionally, 3000 ultrasonic array elements are grouped into 120 sub-arrays, each group containing 25 elements, and the individual ultrasonic array element signals are delayed and added by the intra-group receiving processor, and the addition is performed. There has been proposed a “phased array acoustic apparatus having an in-group processor” that provides a processed signal to one of the channels of a reception beamformer (see, for example, Patent Document 1).

In this “phased array acoustic apparatus having an in-group processor”, the delay line in the in-group receiving processor is any one of a charge coupled device, an analog RAM, a sample and hold circuit, an active filter, an L-C filter, and a switched capacitor filter. And a delay value is provided by a system controller having a digital control circuit. As described in Patent Document 1 (paragraph 0113, FIG. 3), while the delay data is loaded, a weak received signal is buried by digital noise generated by loading the delay data. Loading is performed only once for each scanning line.
JP 2000-33087 A

  In the conventional “phased array acoustic apparatus having an in-group processor”, there is one set of delay amount that can be set in the in-group receiving processor for one scanning line. There is a problem that a large delay amount error occurs with respect to the delay amount, and a grating lobe is generated to deteriorate the acoustic S / N.

  Accordingly, an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of obtaining an ultrasonic image with a small delay amount error at each depth of an imaging region and little acoustic S / N degradation.

An ultrasonic diagnostic apparatus according to the present invention includes a plurality of subarrays configured from electroacoustic transducer elements constituting an ultrasonic array, and a first that delays and adds reception signals from the electroacoustic transducers included in the subarray. A reception beamformer, a second reception beamformer that delays and adds an output signal of the first reception beamformer, using the output of the first reception beamformer as one channel, a first reception beamformer, and a second reception beamformer and a control unit for controlling the delay amount of the receive beamformer, once in an ultrasonic receiver for ultrasonic wave transmission is fixed delay amount .DELTA..tau _m in the first receive beamformer, the second receive beamformer To receive dynamic focus.

Delay .DELTA..tau _m of fixed, the delay amount .DELTA..tau _m in the first receive beamformer, by the delay tau _c in the second receive beamformer, optimum reception focus beam when the depth of imaging region is F _m Is set to be formed. The depth F _m is (F ₁ + F ₂ ) / 3 ≦ F _m ≦ (F ₁ + F ₂ ) / 2, where F _{1 to} F _{2 represent} the depth of the imaging region for one ultrasonic transmission.

  According to the present invention, it is possible to perform reception focusing with the smallest delay amount error over the entire imaging region, and it is possible to obtain a high-quality ultrasonic image while minimizing the deterioration of acoustic S / N.

1 is an apparatus configuration block diagram showing an embodiment of an ultrasonic diagnostic apparatus of the present invention. The delay amount profile figure for demonstrating the delay amount determination method in the 1st receiving beamformer of this invention. The fixed depth characteristic figure of an error evaluation function. The apparatus block diagram which showed the structure of the receiving system from an ultrasonic probe to the 2nd receiving beam former. The apparatus block diagram which shows another one Example of the 1st receiving beam former of this invention. The block diagram of a one-dimensional ultrasonic array. The beam profile figure of a one-dimensional ultrasonic array. The envelope surface extraction figure of the beam profile of a one-dimensional ultrasonic array. The fixed depth characteristic figure of acoustic noise. 1 is an operation conceptual diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

Explanation of symbols

1, 2: Ultrasound diagnostic device 3: Subject 10: Ultrasound probe 11-13: Delay amount profile curve 14: Delay amount error area 20: Device body 21: Transmission / reception separation switch 22: Crosspoint switch 23: Transmission Beamformer 24: Transmitting amplifier 25: Signal processing unit 26: Display units 31-33: Error evaluation function curve 40: Display 41: Device body 42: Cable 43: Ultrasonic probe 44: Display screen 45: Operation panel 50: Captured image 51: Imaging depth numerical display unit 52: Imaging depth image display unit 53: Fixed depth marker 54: Imaging region selection box 61: Fixed depth selection operation unit 62: Imaging region selection operation unit 63: Trackball 100, 700: Ultrasonic array 101-104, 10n, 801-816: Subarrays 111-114, 121-124, 131-134, 1 1 to 144, 701 to 764: array elements 200, 211 to 214, 221 to 224, 231 to 234, 241 to 244: reception amplifier 300, 390: first reception beamformer 350, 360, 370, 550: delay line group 311 to 314, 321 to 324, 331 to 334, 341 to 344, 511 to 514: delay lines 301 to 304, 380, 501: addition means 310, 510: delay amount buffer memories 400 to 404: AD converter 500: first 2 receiving beamformer 600: control unit

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

  First, the configuration of the ultrasonic diagnostic apparatus of the present invention will be described. FIG. 1 is an apparatus configuration block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. The ultrasonic diagnostic apparatus 1 includes an ultrasonic probe 10 and an apparatus main body 20. The ultrasonic probe 10 includes an ultrasonic array 100 including a plurality of array elements, a transmission / reception separation switch 21, a reception amplifier 200, The first receiving beamformer 300 and the crosspoint switch 22 are included.

  The ultrasonic array 100 is connected to a transmission / reception separation switch 21. The transmission / reception separation switch 21 connects the ultrasonic array 100 and the crosspoint switch 22 during ultrasonic transmission, and receives the ultrasonic array 100 and reception during ultrasonic reception. The amplifier 200 is connected. The cross point switch 22 is used as means for selecting which array element the transmission signal from one channel of the transmission beam former 23 is transmitted to. A signal from the transmission beam former 23 at the time of transmission is amplified by the transmission amplifier 24 so as to obtain desired ultrasonic radiation energy, and is transmitted to the ultrasonic array 100 via the cross point switch 22 and the transmission / reception separation switch 21. The The cross point switch 22 may also serve as the transmission / reception separation switch 21.

  A signal received by the ultrasonic array 100 is output to the reception amplifier 200 via the transmission / reception separation switch 21. The receiving amplifier 200 may have a TGC (Time Gain Control) function. The signal from the reception amplifier 200 is sent to the first reception beamformer 300, and the signal is delayed and added for each subarray obtained by dividing the aperture of the ultrasonic array 100. During reception for one scanning line or one transmission, the signal delay amount in the first reception beamformer is fixed. The output of the first reception beamformer 300 is converted into a digital signal by the AD converter 400 and output to the second reception beamformer 500. Note that the AD converter 400 may be included in the ultrasound probe 10.

  In the second reception beamformer 500, dynamic focus processing is performed, and the signals are delayed and added so that a reception beam corresponding to each depth of the imaging region is formed. Here, in the second reception beamformer, the input signal may be branched into a plurality of parts, and different delays may be given to form a plurality of reception beams at the same time, whereby the imaging frame rate can be improved.

  The output of the second reception beamformer 500 is subjected to desired signal processing by the signal processing unit 25, converted into image information by the display unit 26, and displayed. The control unit 600 controls the transmission beam direction, the reception beam direction, the delay amount, display, and the like. The control unit 600 includes an interface for designating the range of the imaging region. For example, when the depth of the imaging region is designated by the user, an appropriate value to be given by the first reception beamformer 300 or the second reception beamformer 500 The delay amount is determined and transferred to the first reception beamformer 300 and the second reception beamformer 500.

  Next, the receiving system of the ultrasonic diagnostic apparatus of the present invention will be described in detail with reference to the drawings. FIG. 4 is an apparatus configuration block diagram showing the configuration of the reception system from the ultrasound probe 10 to the second reception beamformer 500 of the ultrasound diagnostic apparatus 1. In the following, it is assumed that the number of array elements constituting the ultrasonic array 100 is 16. The ultrasonic array 100 includes subarrays 101 to 104 each including four array elements, and the subarrays 101 to 104 include array elements 111 to 114, 121 to 124, 131 to 134, and 141 to 144, respectively. ing. At the time of reception, a signal from the ultrasonic array 100 is output to the reception amplifier 200 by a transmission / reception separation switch 21 (not shown). The signals of all the array elements 111 to 144 are amplified by the individual reception amplifiers 211 to 244 and output to the first reception beamformer 300.

  The first reception beamformer 300 includes a delay line group 350 including delay lines 311 to 344, a delay amount buffer memory 310 for the delay line group 350, and addition means 301 to 304. The outputs of the reception amplifiers 211 to 244 are given different delay amounts, added for each subarray, AD-converted for each subarray by the AD converters 401 to 404, and output to the second reception beamformer 500. The For example, the signals of the array elements 111 to 114 constituting the subarray 101 are amplified by the receiving amplifiers 211 to 214, given a desired delay by the delay lines 311 to 314, and added by the adding means 301. The output signal from the adding means 301 is converted into a digital signal by the AD converter 401 and becomes an input signal per channel of the second reception beamformer 500. Similarly, the subarrays 102 to 104 are input signals per channel of the second reception beamformer 500.

  The second reception beamformer 500 includes a delay line group 550 composed of digital delay lines 511 to 514, a delay amount buffer memory 510 for the delay line group 550, and an adding unit 501.

  When the range of the imaging area is set, the control unit 600 calculates an optimum delay amount corresponding to the range of the imaging area, and uses this to calculate the delay amount buffer memory 310 of the first reception beamformer 300 and the second reception beam. Transfer to the delay amount buffer memory 510 of the former 500. Delay data from the delay amount buffer memory 310 is fixed during reception for one scanning line or one transmission, and the delay data is loaded into the delay line group 350 before reception. In the second reception beamformer, dynamic focus processing is performed, and appropriate delays are given by the digital delay lines 511 to 514 for each depth.

Next, the optimum condition between the depth of the imaging area and the amount of delay given to the intra-group reception processor is examined. FIG. 2 is a delay amount profile of the one-dimensional ultrasonic array showing the relationship between the fixed delay amount in the first reception beamformer and the dynamic delay amount in the second reception beamformer. 1-dimensional ultrasonic array 100 is divided into n sub-arrays 10n, signals from each of the ultrasonic array elements subarray 10n located x _n1 ~x _n2 is processed by the first reception beamformer 300 Thus, it is provided to one channel of the second receive beamformer 500. Assuming that an ideal receive focus beam is formed at a depth F _m in order to determine fixed delay data in the first receive beamformer 300, the profile of the delay amount Δτ _ideal becomes a curve 11. The delay amount Δτ _{c to} be given by the second receive beamformer with respect to the depth F _m is obtained from the phase center of the subarray 10n as follows.

Here, i is an imaginary unit, and ω is an angular frequency of the ultrasonic wave. Therefore, the fixed delay amount Δτ _{m to} be given by the first reception beamformer is obtained as Δτ _m = Δτ _ideal −Δτ _c .

Next, considering that an ideal reception focus beam is formed at the depth F, the profile of the delay amount τ _ideal becomes a curve 13. As in the case of the depth F _m , the delay amount τ _{c to} be given by the second reception beamformer is expressed by Equation (2).

The actual delay amount is τ _c + Δτ _m together with the delay amount Δτ _m in the first reception beamformer obtained previously, and the delay amount profile is shown as a curve 12 in FIG. Therefore, the error from the ideal delay amount is
τ _ideal − (τ _c + Δτ _m ) = (τ _ideal −Δτ _ideal ) − (τ _c −Δτ _c )
If this error is large, the error between subarrays is also large, which causes the generation of grating lobes. Therefore, the parameters affecting the size of the area of .DELTA.e _n region 14 shown by oblique lines in FIG. 2 to the deterioration of the sound S / N, all the sub-arrays 10n, and with respect to depth F ₁ to F ₂ of the imaging region the integral of .DELTA.e _n, the function E depth F _m as the following equation (3), defined as the error evaluation function.

To determine the depth F _m which minimizes the deterioration of sound S / N, may be obtained depth F _m to be dE / dF _m = 0. In order to simplify the problem, assuming that the depth of the imaging region is F _{1 to} F ₂ and the depth F _m (F ₁ <F _m <F ₂ ) is sufficiently far away, the value of the phase center for any depth Suppose that the coordinate x with respect to x _c (x _n1 <x _c <x _n2 ). If the speed of sound is c ₀ , the delay amounts τ _ideal , Δτ _ideal , τ _c , and Δτ _c are approximated as follows.

Substituting equation (4) into equation (3) and executing integration for x and F yields the following equation (5).

Next, a simulation result performed for examining the relationship between the depth F _m represented by the equation (5) and the error evaluation function E will be described with reference to FIG. In the simulation, the aperture L of the one-dimensional ultrasonic array is 19.2 mm, the number of elements is 64 (element pitch 0.3 mm), the frequency is 2.5 MHz, the sound velocity is 1500 m / s, and the depths F _{1 to} F ₂ of the imaging region are calculated. Assuming that the F number is 1 to 9 (F ₁ = 19.2 mm, F ₂ = 172.8 mm), the one-dimensional ultrasonic array is divided into 8, 16, and 32 sub-arrays, respectively. FIG. 3 is a fixed depth characteristic diagram of the error evaluation function E under the above conditions. The horizontal axis indicates the F number F _m / L corresponding to the depth F _m , and the vertical axis indicates the value of the error evaluation function E on the logarithmic axis. ing. In the figure, solid lines 31 to 33 show the results in the case of 8, 16, and 32 subarrays, respectively. From the simulation results of FIG. 3, the minimum value of the error evaluation function E is around F _m / L = 5, and increases slightly when the number of subarrays is small, and when F _m / L> 3, the error evaluation function E It can be seen that the value of can be kept low.

From the above results, with respect to the error evaluation function E depth F _m, has a curved relationship convex downward, the optimum value of the above-mentioned depth F _m, using equation _{(5), dE / dF m} = 0 That is, the depth F _{m at} which df / dF _m = 0 is obtained, and as a result, F _m = (F ₁ + F ₂ ) / 2 is obtained as the optimum value. Accordingly, when the depth F _{1 to} F ₂ (F ₂ > F ₁ ) of the imaging region is sufficiently far from the ultrasonic array, the fixed delay amount in the first reception beamformer is F _m = (F ₁ + F ₂ ) It has become clear that it may be determined so that an optimal reception focus beam is formed at a depth F _m of ₂ ) / 2.

The above result is a result when the depth F _{1 to} F ₂ (F ₂ > F ₁ ) of the imaging region is sufficiently far from the ultrasonic array, and the intensity of the grating lobe is not directly evaluated. Absent. Therefore, hereinafter, simulation results obtained by directly evaluating the grating lobe including a case where the depth of the imaging region is shallow will be described with reference to FIGS.

  In the simulation, a one-dimensional array 700 including 64 point sound source-like elements 701 to 764 (element pitch 0.3 mm, array dimension L = 18.9 mm) as shown in FIG. One subarray was configured, and all 16 subarrays 801 to 816 were configured. Each of the subarrays 801 to 816 is delayed and added by the first receive beamformer, and the 16 outputs from the first receive beamformer are delayed and added by the second receive beamformer. Done. The delay amount given by the first reception beamformer is fixed, and the second reception beamformer performs reception dynamic focus according to the depth. The frequency was 2.5 MHz and the sound velocity of the acoustic medium was 1500 m / s.

  FIG. 7 shows a two-dimensional beam profile of the angle and depth from the center of the one-dimensional array formed by the one-dimensional ultrasonic array 700 of FIG. In FIG. 7, the depth of the imaging region is set to 20 mm to 180 mm, the delay amount in the first reception beamformer is fixed so that optimum beam forming is performed at a depth of 68 mm, and the scanning line direction is a one-dimensional ultrasonic array. 700 is the front direction (0 degree direction). From FIG. 7, it can be seen that the grating lobes are generated in the directions of ± 30 degrees and ± 90 degrees when the depth is shallower than 68 mm and when the depth is deep.

In order to define the grating lobe as acoustic noise, first, the envelope surface of the beam profile as shown in FIG. 7 is extracted. The envelope surface of FIG. 7 is shown as in FIG. In the following, the acoustic energy difference N _m = P between the total acoustic energy P _m of the envelope surface as shown in FIG. 8 and the acoustic energy S _i of the envelope surface of the beam profile when ideal focusing is performed at each depth. _m− S _i is calculated, and N _m is defined as acoustic noise.

FIG. 9 shows the relationship between the fixed depth F _m at which the same optimum focus beam as the ideal state is formed by the delay amount given by the first reception beam former and the second reception beam former, and the acoustic noise Nm. It is the fixed depth characteristic figure of the acoustic noise which showed the relationship. In the drawing, curves 34 to 38 indicate depth ranges F _{1 to} F ₂ (F ₁ <F ₂ ) of the imaging region, which are 20 mm to 180 mm, 20 mm to 150 mm, 40 mm to 120 mm, 100 mm to 180 mm, and 160 mm to 180 mm, respectively. Corresponds to the case. In the curves 36 to 38 in which the distance from the one-dimensional ultrasonic array can be regarded as being far away, almost the same as the result shown in FIG. 3, F _m = (F ₁ + F ₂ ) / 2 is the optimum value of the fixed depth. However, when the imaging region includes a region that cannot be regarded as being far away, such as the curves 34 and 35, the optimum value of the fixed depth is about F _m = (F ₁ + F ₂ ) / 3. Here sufficiently far and is equivalent to the relationship between the minimum value F ₁ of the depth of half the dimension L / 2 and the imaging region of the one-dimensional array is _{arcTan (L / 2F 1) ≒} L / 2F 1, in the case of one-dimensional ultrasonic array 700 shown in FIG. 6, the F ₁ ≧ 40 mm, arcTan to within about _{2% (L / 2F 1)} ≒ L / 2F 1 holds.

From the above, when the minimum depth F ₁ of the imaging region is in a shallow place that cannot be regarded as being far away, and the minimum depth F ₂ of the imaging region is sufficiently far away, the first received beam The fixed delay amount in the former may be determined so that an optimum reception focus beam is formed at a depth F _m where F _m = (F ₁ + F ₂ ) / 3.

Therefore, including the result shown in FIG. 3, the fixed delay amount in the first receive beamformer is that the depth F _m is (F ₁ + F ₂ ) / 3 ≦ F _m ≦ (F ₁ + F ₂ ) / 2. may be determined as a range, when imaging to deep especially from shallow is _{F m = (F 1 + F} 2) / 3, when imaging a sufficiently deep is _{F m = (F 1 + F} 2 ) / 2.

  The above results are obtained when the sound speed of the object to be measured is constant at 1500 m / s, and is applied when the object to be measured is homogeneous and the sound speed is substantially constant. However, if the object to be measured is a living body, for example, the sound speed has a width of about (1560 ± 70) m / s depending on the type of living tissue. Therefore, when calculating the delay time as shown in Equation (4), it is necessary to consider that an error occurs between the focus distance determined from the set sound speed and the actual focus distance.

In the ultrasonic diagnostic apparatus of the present invention, it is assumed that the set value of the sound speed is c ₀ and the actual sound speed of the object to be measured is c ₀ + Δc. Further, the focus distance when the sound speed is c ₀ is F ₀ , and the actual focus distance is F ₀ + ΔF. At this time, since the delay time obtained from the set value is equal to the actual delay time, the relational expression F ₀ c ₀ = (F ₀ + ΔF) (c ₀ + Δc) is established. From this relational expression, ΔF / F ₀ = − (Δc / c ₀ ) / (1 + Δc / c ₀ ) is obtained. As described above, for example, if the sound velocity of the living tissue is (1560 ± 70) m / s, and c ₀ = 1560 m / s and Δc = ± 70 m / s, | ΔF / F ₀ | ≦ 4. 3%. Actually, it is desirable to set | ΔF / F ₀ | ≦ 5% in consideration of effects such as refraction caused when sound waves propagate through different tissues.

From the above results, after obtaining the depth F _m for determining the fixed delay amount in the first reception beamformer described above, the depth F _m can be finely adjusted within the range of ± 5% of the value. It is desirable in practice.

Next, a method for determining a delay amount to be given by the first reception beamformer 300 and the second reception beamformer 500 when the imaging range depths F _{1 to} F ₂ are given will be described by taking the subarray 101 as an example.

First, a depth F _m for determining a fixed delay amount given by the first reception beamformer 300 from the minimum value F ₁ and the maximum value F ₂ of the depth of the imaging range is (F ₁ + F ₂ ) / 3. ≦ F _m ≦ (F ₁ + F ₂ ) / 2. Here, an algorithm for obtaining the depth F _m will be described. First, information on the boundary between the depth that can be regarded as a short distance and the depth that can be regarded as a far distance is given to the ultrasonic probe, and the depth of these boundaries is assumed to be D. The boundary depth D is, for example, a value such that arcTan (L / 2D) ≈L / 2D is established with an error of 2%, with the length L / 2 being half the diameter L of the ultrasonic probe as a representative dimension. Just choose.

First, when the minimum value F ₁ of the depths F _{1 to} F ₂ of the imaging region is F ₁ ≧ D, F _m = (F ₁ + F ₂ ) / 2. When the minimum value F ₁ of the depths F _{1 to} F ₂ of the imaging region is equal to the aperture (F number is 1) and F ₁ = L, F _m = (F ₁ + F ₂ ) / 3. In the range of L <F ₁ <D, for example, the relational expression of (F ₁ + F ₂ ) / 3 <F _m <(F ₁ + F ₂ ) / 2 is linear between L <F ₁ <D. Interpolation is performed, and the optimum depth F _m is obtained from the relational expression of F _m = (F ₁ + F ₂ ) (DL) / (3D−2L−F ₁ ).

Next, for the array elements 111 to 114, a delay amount Δτ _ideal when an ideal reception focus beam is formed at the depth F _m is obtained, and the smallest delay amount among them is Δτ _min . Thus, the delay amount Δτ _{m to} be given to the delay lines 311 to 314 in the first reception beamformer 300 is obtained as Δτ _m = Δτ _ideal −Δτ _min .

Next, when the same delay amount Δτ _c is given to the array elements 111 to 114 constituting the subarray 101 and added, the received beam is focused at the depth F _m , and the expression (1) is used for the subarray 101. A delay amount Δτ _c is obtained. Further, a difference Δτ _d = Δτ _c −Δτ _min between Δτ _c and Δτ _min is obtained.

When acquiring data of the depth F of the imaging region, the second reception beamformer 500 performs dynamic focus processing. That is, the delay amount given by the delay line 511 in the second reception beamformer 500 is obtained as follows. First, when the same delay amount τ _c is given to and added to the array elements 111 to 114 constituting the subarray 101, the received beam is focused at the depth F, and the delay amount is expressed using the equation (2) for the subarray 101. Find τ _c . From the delay amount τ _c and Δτ _d , the delay amount τ _c ′ to be given by the delay line 511 is obtained as τ _c ′ = τ _c −Δτ _d . The delay amounts Δτ _m and τ _c ′ to be given by the first reception beamformer 300 and the second reception beamformer 500 are obtained for all the other subarrays 102 to 104 by the same calculation method.

As described above, when the reception beam is formed at the depth F, if the depth of the imaging region is sufficiently far away, the delay data like the curve 12 in FIG. 2 is given. Since the curve 12 is obtained as the depth F _m = (F ₁ + F ₂ ) / 2, as described above, the difference from the delay data curve 13 in which an ideal received focus beam is formed at the depth F is the smallest. It is suppressed. Therefore, it is possible to minimize the influence of the grating lobe at the depths F _{1 to} F ₂ of the imaging region. Similarly, even when the imaging region includes a shallow depth, an appropriate fixed depth F _m is selected as described above, and the influence of the grating lobe can be minimized.

Further, when data of F _{min to} F _max is collected by m transmissions with respect to the minimum value F _min and the maximum value F _max of the depth of the imaging region, for example, F _{min to} F _{max by} m transmissions. The depth F _{1 to} F ₂ of the imaging region in one transmission is determined so that the entire image can be captured, and the delay amount fixed by the delay line group 350 for m sets of F _{1 to} F ₂ by the above-described method. Δτ _m may be obtained respectively.

Since the direction of the grating lobe generated in each of the m sets is different, data from F _{min to} F _max is collected using Δτ _m fixed to one set of F _{1 to} F ₂ . This may be performed for all sets of F _{1 to} F ₂ to add all the collected data.

  Further, as shown in FIG. 5, two delay line groups in the first reception beamformer are connected in series, and a first delay line group 360, a second delay line group 370, an adding means 380, a delay amount buffer, and so on. The first reception beamformer 390 configured from the memory 310 is used, the delay amount to be given by the first delay line group 360 is fixed in all scanning line directions, and the second delay line group 370 has a beam direction. If the delay amount for changing only the delay time is given, the size of the delay data to be loaded to each scanning line becomes small, and high-speed imaging and memory saving can be realized.

  The delay line groups 360 and 370 in the first reception beamformer described above include at least one element among a charge coupled device, an L-C filter, a sample and hold circuit, a switched capacitor circuit, and an analog RAM. To do.

  Although the above-described embodiment is intended for a one-dimensional ultrasonic array, the apparatus configuration having the first and second reception beamformers is from 2000 to 3000 elements like a reception signal from the two-dimensional ultrasonic array. This is a particularly effective configuration for reducing the number of received signals to 100-200 channels. The idea of the present invention and the above-described reception sequence and control are not limited to the application to the one-dimensional ultrasonic array, but are also applied to the two-dimensional ultrasonic array.

  A specific example of an operation at the time of ultrasonic diagnosis performed under the configuration and control as described above will be described with reference to the drawings.

FIG. 10 is an operation conceptual diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. The ultrasonic diagnostic apparatus 2 includes an apparatus main body 41, a cable 42, an ultrasonic probe 43, a display 40, and an operation panel 45 for a user to input imaging conditions. When the ultrasonic probe 43 is applied to the subject 3, a captured image 50 is displayed on the display screen 44 of the display 40. At this time, the depth information of the imaging region of the captured image 50 is displayed on the display screen 44 in the imaging depth numerical value display unit 51 and the imaging depth image display unit 52. The imaging depth numerical display unit 51 has a fixed depth F for determining the minimum value F ₁ and maximum value F ₂ of the depth of the imaging region and the delay amount of the first reception beamformer (not shown) included in the ultrasonic probe 43. Numerical value information of _m is displayed, and in the imaging depth image display unit 52, such depth information is displayed graphically, for example, information on the fixed depth is represented by a fixed depth marker 53.

The range of the imaging area can be selected by operating the imaging area selection box 54 displayed on the display screen 44 by operating the imaging area selection operation unit 62 or the trackball 63 provided on the operation panel 45, for example. When the range of the imaging region is designated, the optimal fixed depth F _m is calculated from the minimum value F ₁ and the maximum value F _{2 of the} imaging region depth obtained from this, and the _first fixed in the ultrasound probe 43 is calculated. The amount of delay in the receiving beamformer is set and imaging is performed. Further, the fixed depth F _m can be arbitrarily set by the user continuously or stepwise by means of a fixed depth selection operation unit 61 provided on the operation panel 45, whereby the first depth F _m included in the ultrasonic probe 43 is set. The setting of the delay amount in one reception beamformer and the depth information represented by the imaging depth numerical value display unit 51 and the imaging depth image display unit 52 in the display screen 44 are changed following the real time.

  Through the operation of the ultrasonic diagnostic apparatus as described above, the optimum reception focus is performed with respect to the depth of the imaging region, and a high-quality diagnostic image can be obtained with an inexpensive apparatus configuration, and at any depth. It is also possible to display a clear image with high resolution.

Claims (5)

A plurality of subarrays composed of electroacoustic transducer elements;
A first receive beamformer for delaying and adding received signals from a plurality of electroacoustic transducers constituting the sub-array;
A second receive beamformer that delays and adds the output signal of the first receive beamformer with the output of the first receive beamformer as one channel;
A control unit for controlling a delay amount of the first reception beamformer and the second reception beamformer,
During ultrasonic receiving for one ultrasonic transmission have rows dynamic focus received by the second receive beamformer fixed delay amount .DELTA..tau _m in the first receive beamformer,
From the delay amount Δτ _m in the first reception beamformer and the delay amount τ _c in the second reception beamformer , the delay amount Δτ so that a reception focus beam having an imaging region depth of F _m is formed. set the _m,
When the depth of the imaging area for one ultrasonic transmission is F _{1 to} F ₂ (F ₂ > F ₁ ), (F ₁ + F ₂ ) / 3 ≦ F _m ≦ (F ₁ + F ₂ ) / 2 An ultrasonic diagnostic apparatus characterized by being. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the system control unit receives the minimum value F ₁ and the maximum value F ₂ of the depth of the imaging region, or the input of the imaging region, in the first reception beamformer. An ultrasonic diagnostic apparatus characterized by calculating a delay amount Δτ _m . The ultrasonic diagnostic apparatus according to claim 1, wherein an ultrasonic beam is transmitted a plurality of times (m times) to the depths F _{min to} F _max of the entire imaging region in one scanning line, and the imaging region for each transmission is transmitted. An ultrasonic diagnostic apparatus characterized in that imaging is performed by changing the depths F _{1m to} F _2m and changing the delay amount Δτ _m for each of the depths F _{1m to} F _2m . The ultrasonic diagnostic apparatus according to claim 1, wherein an ultrasonic beam is transmitted a plurality of times (m times) with respect to the depths F _{min to} F _max of the entire imaging region in one scanning line, and the transmission is performed for each transmission. Imaging is performed by changing the delay amount Δτ _m, and a reception beam corresponding to the depths F _{min to} F _max of the entire imaging region is formed for each transmission by the first reception beam former and the second reception beam former. An ultrasonic diagnostic apparatus characterized in that m reception beams for one scanning line are added to form a reception beam for depths F _{min to} F _max of the entire imaging region on the scanning line.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the first reception beamformer includes only a first delay line that gives a fixed delay amount to all scanning lines and an angle component with respect to one scanning line. An ultrasonic diagnostic apparatus comprising: a second delay line that provides

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