JP3482361B2 - Ultrasound diagnostic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to the structure of a phasing addition circuit.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus, a delay time is given to a reception signal received by each vibrating element forming an array transducer so that reflected wave fronts from a reception focus point may coincide with each other. Phasing addition is performed to add received signals to each other. By this phasing addition, a reception ultrasonic beam having a sharp directivity can be obtained.

FIG. 6 is a block diagram for explaining the configuration of the reception phasing addition section of the ultrasonic diagnostic apparatus of the first conventional technique. The reflected wave of the ultrasonic wave from the subject is received by the N vibration elements 2, amplified by the amplifier 4, and then input to the reception phasing addition unit 6. The reception phasing addition unit 6 is a circuit that performs phasing addition of the reception signals obtained by the vibrating elements 2 and outputs the signals, and an ADC (Analog-to-
A digital converter) 8 and a delay device 10 are provided. The received signal from the vibration element 2 amplified by the amplifier 4 is AD
Converted to a digital signal at C8. Delay device 10 is RA
This is a digital delay circuit using an M (Random Access Memory), and an address circuit (not shown) controls the timing of reading the digital signal value stored in the RAM, thereby obtaining an arbitrary signal delay. In this way, the received signals delayed for each vibrating element 2 are added by the adder 14 and passed to the subsequent signal processing unit (not shown).

In this configuration, the delay time can be continuously variably controlled by the delay device 10 for each oscillating element 2 (that is, for each channel), and thus the reception dynamic focus can be realized.

The ADC 8 used in the ultrasonic probe is
Its performance is high performance such as resolution of 12 bits and sampling rate of 40 MHz, and is generally expensive. Further, the cost of the RAM configuring the delay device 10 is not negligible. The conventional device requires the ADC 8 and the delay device 10 for each channel of the array transducer, and generally the number of the channels is very large, which increases the cost of the device.

The second conventional device described below reduces the cost of the device. FIG. 7 is a block diagram illustrating the configuration of a reception phasing addition unit in the conventional ultrasonic probe device. In this configuration, the reception signals of N channels in total output from the array transducer are amplified by the amplifier 4 for each channel and input to the preceding phasing addition circuit 22 provided in the reception phasing addition unit 20. In the preceding phasing addition circuit 22, the delay adder 24 phasing-adds the reception signals for each adjacent n channels, and generates and outputs the reception signals of N / n channels. Each reception signal output from the preceding phasing addition circuit 22 is converted into a digital signal by the ADC 26, and then input to the delay unit 28 which is a digital delay circuit including a RAM or the like. The delay device 28 applies a delay set for each N / n channel received signal, and the adder 3
0 adds these and outputs to the following signal processing part which is not shown in figure. As described above, in this conventional device, the ADC 26 and the delay device 28 required are reduced by bundling the channels into a predetermined number of channel groups in the pre-phase phasing addition circuit 22.

In this configuration, the phasing addition condition in each delay adder 24 and the delay time of each delay device 28 are set according to the target reception focus point. Basically, of the delay time given to each channel, an offset amount that can be commonly given to adjacent n channels is used as the delay unit 2
8 and the delay adder 24 is configured to adjust the delay time difference between the n channels.

The phasing addition condition of each delay adder 24 is determined corresponding to the target reception focus point. Therefore, when performing dynamic focusing with this device, not only the delay time of the delay unit 28 is continuously variably controlled, but also the phasing addition condition of the delay adder 24 is linked with the movement of each reception focus point. It is necessary to variably control. FIG. 8 is a schematic diagram for explaining the phasing addition condition set in the delay adder 24. In the figure, the vertical axis is the delay time difference dτ between two adjacent channels, and the horizontal axis is the target reception focus depth F. Each curve in the figure is the target 2
The change in dτ with respect to F is shown using the distance x between the vibration element of the channel and the center position of the array transducer as a parameter. (A) and (b) of the figure respectively correspond to the case where the deflection angles of the reception beam are θ = 0 ° and θ = 30 °. For example, in the case of setting F = 40 mm, the phasing addition condition is set so that dτ at F = 40 mm is given between each two adjacent channels as indicated by “◯” on each curve in the figure. Is set. When F is changed, the set of “◯” corresponding to dτ set between two adjacent channels moves in the F-axis direction while F forms a constant straight line in the figure.

The delay adder 24 corresponds to an analog signal and is composed of a delay line with a tap and an analog switch for selecting the tap. In order to change the delay time in the delay adder 24, it is necessary to switch the analog switch, but noise is generated at that time. Therefore, in order to avoid the influence of the noise, normally two delay adders 24 are provided. The received signal from the vibrating element 2 is input to both systems, one of the outputs of the two delay adders is selected, and is connected to the ADC 26. While the received signal is delayed and added by the selected delay adder and output, the other delay adder in the pair taps to set the delay time for the next target reception focus point. Switching operation is performed. In this way, the reception beam in which the influence of noise is avoided can be obtained by moving the reception focus point while alternately performing the reception operation and the phasing addition condition setting operation using the two delay adders.

The configuration of the reception phasing addition section 20 in the above-mentioned second conventional apparatus is as follows:
This is a two-stage configuration that is called a post-stage phasing addition circuit. A related technique of the apparatus having the two-stage phasing addition circuit is disclosed in US Pat. No. 4,829,491.

[0011]

As described above, the first conventional device has a problem that the cost of the device increases. On the other hand, in the second conventional apparatus that performs phasing addition in two stages, the former stage and the latter stage, the cost is reduced because the received signals are bundled for each of a plurality of channels. However, two phasing stage addition circuits are required. Therefore, the cost increases accordingly. Therefore, there is a problem that the cost reduction effect is not sufficient. Here, if the pre-stage phasing addition circuit is provided as one system, the cost can be further reduced, but the phasing addition condition of the pre-stage delay adder cannot be changed during the dynamic focusing (that is, Since the phasing addition condition corresponds to a fixed focus), there is a problem that the image quality of the ultrasonic diagnostic apparatus deteriorates.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of obtaining good image quality while reducing the cost by simplifying the apparatus configuration. .

[0013]

An ultrasonic diagnostic apparatus according to the present invention is an ultrasonic diagnostic apparatus in which a reception beam is formed by a reception dynamic focus that continuously changes the depth of a target reception focus. An array transducer that consists of elements and transmits and receives ultrasonic waves, and the above-mentioned plurality of vibrating elements are divided into a plurality of groups, and a delay time difference suitable for group-specific reception focus is set between the plurality of vibrating elements in each group. At the same time, the target reception focus can be adjusted by phasing and adding the received signals of each vibrating element to each group, and selecting the pre-phase phasing addition circuit that generates the reception signals for each group and the plurality of groups that form the reception aperture. A variable aperture control circuit that widens the aperture of the receiving aperture as it gets deeper, and reception by multiple groups by group selection of the variable aperture control circuit A phasing addition circuit for performing phasing addition according to a target reception focus by receiving dynamic focus, and a scan control section for controlling phasing addition in the preceding phasing addition circuit and the following phasing addition circuit. The scan control unit sets the group-specific reception focus of each group deeper as the group moves away from the center of the reception aperture, and sets the group-specific reception focus of each group while each reception beam is formed. The delay time difference adapted is fixed, and the setting of the delay time difference adapted to the group-specific reception focus of each group can be switched between the reception beams having different deflection angles θ .

According to the present invention, in the preceding-stage phasing addition circuit, the received signals from the vibrating element are phasing-added by a plurality of channels and bundled. The bundled reception signals are phased and added by the post-phased phase adding circuit, and at this time, variable aperture control is performed. That is, for example, when the receiving focus is set at a short distance, the aperture of the receiving aperture is narrowed, that is, the group-specific received signals output from the group of the array transducers from the center are phased by the post-phase phasing addition circuit. On the other hand, when the reception focus is adjusted to a long distance, the grouped reception signals of the outer groups are controlled to be phased and added. Here, as described in the second related art, in the conventional two-stage phasing addition, the phasing addition condition set in each of the respective oscillating elements and each group of oscillating elements in the previous stage is the common reception focus point. It corresponded to. On the other hand, in the present invention,
A delay time difference (phasing addition condition) corresponding to a common reception focus point is set for the vibration elements belonging to each group, but the phasing addition condition is basically based on different reception focus points between different groups. Is set. That is, each group is set with a delay time difference between the vibrating elements in the group based on different reception focus (group-specific focus). By setting the group-by-group reception focus in this way, the reception focus obtained as a result of the phasing addition in the post-stage phasing addition circuit has a certain extent near the target reception focus. In the present invention, the reception focus for each group is obtained in accordance with the depth set according to the distance between the corresponding group and the reception aperture center, and the group subjected to phasing addition being changed by the variable aperture control. The state of reception focus (degree of spread, center position of spread, etc.) is adjusted.

[0015]

According to the present invention, the dynamic phasing addition is performed by changing the target reception focus by the post-phase phasing addition circuit and performing phasing addition according to it.
At this time, the resulting spread state of the reception focus is adjusted according to the target reception focus.

[0017]

According to the present invention, the setting of the delay time difference between the oscillating elements in each group, which is set in the preceding phasing addition circuit, is fixed while the reception beam is formed, but is different between different reception beams. The settings can be configured to be switchable. Even if noise or the like is generated by changing the setting of the delay time difference, in the present invention, since the setting is changed at the intervals at which the reception beams are switched, it is possible to prevent the noise or the like from adversely affecting the image quality.

[0019]

According to the variable aperture method, the spatial resolution at a shallow depth of the subject is improved by narrowing the reception aperture, and the spatial resolution at a deep position is improved by widening the aperture.
Correspondingly, in the present invention, when the target reception focus is set to be shallow and the reception aperture is set to be narrow, a group suitable for shallow group-specific reception focus is subjected to phasing addition by the subsequent phasing addition circuit, while the target When the reception focus is deep and the reception aperture is set wide, a group suitable for the deep group-specific reception focus is further added to the phasing addition. As a result, suitable reception focus is realized regardless of whether the target reception focus is shallow or deep, and the image quality can be improved.

Preferably, the front-stage phasing addition circuit is a circuit that processes an analog signal, and the second-stage phasing addition circuit is a circuit that processes a digital signal. Desirably,
The scan control unit further switches the setting of the delay time difference suitable for the reception focus for each group according to the depth of the transmission focus of the ultrasonic waves emitted from the array transducer.

The transmission focus is generally set to the region of interest of observation. According to the present invention, the reception focus for each group is switched according to the depth of the transmission focus, so that the reception focus adapted to the region of interest is realized.

The preferred embodiment of the present invention on the following, the respective groups are those composed of two vibration elements adjacent each. Since the group includes a plurality of vibrating elements, the configuration of the post-phase phasing addition circuit can be simplified, while the small group can provide a preferable image quality. Desirably, the preceding phasing addition circuit includes a plurality of circuits corresponding to the plurality of groups, and a plurality of delay adders in which the delay time differences are set, and each of the delay adders includes the two A delay line having a plurality of taps to which one of the two vibrating elements is selectively connected; and an adder for adding the other of the two vibrating elements and the output of the delay line to output the reception signal for each group. ,including.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram of a sector electronic scanning type ultrasonic diagnostic apparatus according to an embodiment of the present invention.
The array transducer 50 is provided in the probe that is brought into contact with the subject. Each vibrating element forming the array transducer 50 is
It has a function of receiving a transmission signal generated by the transmission drive unit 52 and emitting an ultrasonic pulse into the living body, and a function of detecting a reflected wave of the ultrasonic pulse from the subject and outputting a reception signal. The received signal for each transducer (for each channel) output from the array transducer 50 is amplified by the amplifier 54 and then added by the reception phasing adder 56 to generate one echo signal. The echo signal is input to the echo signal processing unit 58. The echo signal processing unit 58 is, for example, B
Generates mode image data and Doppler image data
(Digital Scan Converter) Output to 60. DSC6
At 0, the image data based on the observation of the subject and other display contents are combined, and the monitor 62 reads the combined image data from the DSC 60 at a predetermined frame rate and displays it.

The transmission drive unit 52 controls the delay time of the transmission signal for each channel to focus the transmission ultrasonic wave, and the reception phasing addition unit 56 controls the delay time given to the reception signal for each channel. By doing so, reception focus is performed. The scan control unit 64 controls setting and changing of the delay time for each channel in the transmission drive unit 52 and the reception phasing addition unit 56.

The feature of this apparatus resides in the reception phasing addition unit 56. FIG. 2 is a block diagram for explaining the reception phasing addition unit 56. The reception phasing addition unit 56 includes a front phasing addition circuit 70 and a rear phasing addition circuit 72.

In the preceding phasing addition circuit 70, a plurality of adjacent vibrating elements 74 are divided into groups. In this embodiment, each group is composed of two adjacent vibrating elements 74. The pre-stage phasing addition circuit 70 includes a delay adder 76 that delays and adds the received signals from the two vibrating elements 74 forming each group. That is, the array transducer 50
Has N oscillator elements 74 (for convenience, N is an even number), N / 2 delay adders 76 are provided.

FIG. 3 is a schematic diagram showing an example of the configuration of each delay adder 76. The delay adder 76 is apparent from FIG.
Delay addition circuit that processes analog received signals
And has an LC delay line 80 with a tap in order to cause a relative delay time difference between the received signals of the two input channels. Since only one of the two channels needs to be delayed, only one delay line 80 is required. The analog switch 82 connects one of the channels to the tap corresponding to the desired delay time and the other channel to the input terminal of the adder 84. The output terminal of the delay line 80 is connected to the other input terminal of the adder 84.

In the front-stage phasing addition circuit 70, the received signals are added every two channels, and N / 2 received signals for each group are output. As shown in FIG. 2, the received signals for each group are input to the post-stage phasing addition circuit 72.

The post-stage phasing addition circuit 72 is provided with an ADC 90 and a delay device 92 for each channel. Delay device 92
Is a digital delay circuit composed of RAM or the like, and A
The group-specific reception signals converted into digital signals by the DC 90 are delayed and output to the adder 94. The adder 94 receives the reception signals for each group of N / 2 channels, adds the reception signals of the group arranged in the desired reception aperture diameter among them, and forms one echo signal, which is sent to the echo signal processing unit 58. Output. That is, the adder 94 has a variable aperture control function. Further, in the post-stage phasing addition circuit 72, the setting of the delay time of the delay device 92 can be changed to continuously change the reception focus to form a reception beam.

FIG. 4 is a schematic diagram for explaining the phasing addition condition set in the delay adder 76 of the preceding phasing addition circuit 70. In the figure, the vertical axis represents the delay time difference dτ between two adjacent channels forming a group, and the horizontal axis represents the reception focus depth F. Further, FIGS. 9A and 9B respectively show the case where the deflection angles of the reception beam are θ = 0 ° and θ = 30 °. The delay time of each channel under the condition that the receiving focus is optimally adjusted to a certain point designated by θ and F is represented by τ (k) (k = 1, 2, ..., N). This τ
Is the sum of the delay times of the front-stage phasing addition circuit and the post-stage phasing addition circuit, and corresponds to the delay time to be set in each delay device 10 in the first conventional device described above. Figure 4
Each curve of is between two adjacent channels in a group (spacing =
The difference between τ in 0.2 mm) is d τ, and this is plotted as a function of F. The parameter x is the distance between the midpoint of the two vibrating elements 74 forming the group and the center of the array transducer. is there. In both of the figures (a) and (b), x is taken at 2 mm intervals in the range of -10 to 10 mm, and each straight line having a constant dτ corresponds to x = 0 mm, and is a curve that is vertically separated from that line. Corresponds to a large x.

One of the features of this apparatus is that dτ corresponding to different F depending on x, as indicated by "○" in FIG.
Is set in the delay adder 76 of the preceding phasing addition circuit 70. That is, in this apparatus, dτ is determined in accordance with the reception focus determined for each group. Specifically, dτ is set to a value corresponding to a large F as the absolute value of x increases. For example, in the case of θ = 0 ° shown in FIG. 7A, dτ at the reception focus F = 20 mm is for the group located at x = 0 mm, and d = 0 for the group located at x = 10 mm. , Dτ at the reception focus F = 40 mm is set.

In this apparatus, the setting of dτ for each group is fixed in one reception beam. This simplifies the configuration of the reception phasing addition unit 56.

The method of setting dτ of the present apparatus suppresses the deterioration of image quality when the reception phasing addition unit 56 as a whole performs reception dynamic focusing while fixing the phasing addition condition in the preceding phasing addition circuit 70. It is suitable for This is because, by the variable aperture control, the aperture of the reception aperture is set smaller as the target reception focus becomes shorter, and the aperture of the reception aperture becomes wider as the target reception focus becomes longer. That is, when the target reception focus is a short distance, d corresponding to a small F is
The received signals from the group for which τ is set are phased and added by the adder 94, while the farther the target receiving focus is, the more the group for which dτ corresponding to a larger F is set is included in the receiving aperture. Is.

The setting of dτ for each group is θ
Is changed to form a new receive beam.

As shown in FIG. 4, dτ of each group
F corresponding to is distributed in a certain range. This will be referred to as the front focus range. The range is, for example,
It may be preferable to set a depth range (referred to as a depth of interest range) that is desired to be observed with high precision or good image quality.

For the same reason, the transmission focus F
A configuration in which the front focus range can be moved in conjunction with t is also preferable. Transmission focus Ft
Is considered to be set according to the depth of interest range. In contrast to the example of Ft = 80 mm shown in FIG.
FIG. 9 is a schematic diagram showing an example of setting conditions of the delay adder 76 corresponding to Ft = 40 mm. In FIG. 5, since the transmission focus is shallower than in the case of FIG. 4, the front focus range is also set by shifting to a shallow range.

In the above example, one reception beam from a short distance to a long distance is constructed based on the reflected wave of one transmission ultrasonic pulse. On the other hand, there is a technique called transmission multi-stage focus in which a plurality of ultrasonic pulses with different depths of the transmission focus point are sequentially emitted and the reception information of the depth corresponding to each transmission focus is connected.
In this multi-stage transmission focus, the reception beam range corresponding to each transmission focus point becomes the depth of interest range. Therefore, the delay adder 76 is interlocked with the change of the transmission focus point.
It is also preferable to change the setting of and to move the front focus range to within the reception beam range corresponding to the next transmission focus point.

[0040]

According to the ultrasonic probe of the present invention, a plurality of vibrating elements are grouped, and the delay time difference between the vibrating elements in the group is based on the different receiving focus (group-specific focus) for each group. Is set. The state of the actual receiving focus is set according to the fact that the receiving focus for each group is set to a depth according to the distance between the corresponding group and the center of the receiving aperture, and the group to be phased and added changes by the variable aperture control. There is an effect that the degree of spread, the central position of spread, and the like can be adjusted appropriately. In particular, the present invention provides that while the receive beam is formed,
When the setting value of the delay time difference of the vibrating elements in the group is fixed and the configuration of the phasing addition circuit is simplified, by setting the deeper focus for each group with a larger distance from the center of the receiving aperture, the image quality deteriorates. The effect that can suppress can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a sector electronic scanning type ultrasonic diagnostic apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram for explaining a reception phasing addition unit according to the embodiment.

FIG. 3 is a schematic diagram showing a configuration of a delay adder of the pre-phase phasing addition circuit according to the embodiment.

FIG. 4 is a schematic diagram for explaining a phasing addition condition set in the delay adder of the preceding phasing addition circuit when the transmission focus Ft = 80 mm.

FIG. 5 is a schematic diagram for explaining phasing addition conditions set in the delay adder of the preceding phasing addition circuit when the transmission focus Ft = 40 mm.

FIG. 6 is a block configuration diagram for explaining a configuration of a reception phasing addition unit of an ultrasonic diagnostic apparatus which is a first conventional technique.

FIG. 7 is a block configuration diagram for explaining a configuration of a reception phasing addition unit of an ultrasonic diagnostic apparatus which is a second conventional technique.

FIG. 8 is a schematic diagram for explaining a phasing addition condition set in the delay adder of the preceding stage phasing addition circuit according to the second conventional technique.

[Explanation of symbols]

50 array transducer, 52 transmission drive section, 54 amplification section, 56 reception phasing addition section, 58 echo signal processing section,
60 DSC, 62 monitor, 64 scan controller,
70 front phasing addition circuit, 72 rear phasing addition circuit, 7
4 vibration elements, 76 delay adder, 92 delay device, 94
Adder.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-8-317924 (JP, A) JP-A-61-196949 (JP, A) JP-A-9-322896 (JP, A) JP-A-56- 151029 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (5)

(57) [Claims] 1. In an ultrasonic diagnostic apparatus in which a reception beam is formed by a reception dynamic focus that continuously changes the depth of a target reception focus, an array transducer including a plurality of vibrating elements and transmitting and receiving ultrasonic waves. The plurality of vibrating elements are divided into a plurality of groups, and a delay time difference suitable for group-specific reception focus is set between the plurality of vibrating elements in each group, and the reception signals of the respective vibrating elements are adjusted for each group. A pre-stage phasing addition circuit that performs phase addition and generates reception signals for each group, and a variable aperture control circuit that widens the aperture of the reception aperture as the target reception focus becomes deeper by selecting multiple groups that form the reception aperture. And targeting a plurality of received signals for each group by group selection by the variable aperture control circuit by receiving dynamic focus. A post-stage phasing addition circuit that performs phasing addition according to the signal focus, and a scan control unit that controls phasing addition in the front-stage phasing addition circuit and the post-stage phasing addition circuit, the scan control unit, The group-specific reception focus of each group is set deeper as the group moves away from the center of the reception aperture, and the delay time difference adapted to the group-specific reception focus of each group is fixed while each reception beam is formed. ,
An ultrasonic diagnostic apparatus, wherein the setting of the delay time difference suitable for the group-specific reception focus of each group can be switched between the reception beams having different deflection angles θ . 2. The apparatus according to claim 1, wherein the front phasing addition circuit is a circuit that processes an analog signal, and the rear phasing addition circuit is a circuit that processes a digital signal. Sound wave diagnostic equipment. 3. The apparatus according to claim 1, wherein the scan control unit further sets a delay time difference suitable for the reception focus for each group by setting a transmission focus depth of ultrasonic waves emitted from the array transducer. An ultrasonic diagnostic apparatus characterized in that the ultrasonic diagnostic apparatus is switched according to the height. 4. A according to claim 1, 2 or 3 Symbol mounting apparatus, the ultrasonic diagnostic apparatus characterized by being composed of respective each group two adjacent transducer elements. 5. The apparatus according to claim 4 , wherein the preceding-stage phasing addition circuit includes a plurality of circuits corresponding to the plurality of groups, each circuit including a plurality of delay adders in which the delay time differences are set. The delay adder adds a delay line having a plurality of taps to which one of the two vibrating elements is selectively connected, and the other of the two vibrating elements and the output of the delay line to add the delay line. An ultrasonic diagnostic apparatus comprising: an adder that outputs a reception signal for each group.