JPH10127633A - Ultrasonic diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of an ultrasonic image by reducing a side lobe caused in an ultrasonic beam pattern. SOLUTION: In addition to an ordinary oscillator 32 for main beam formation, an oscillator 34 for side lobe formation is provided. By subtracting a 2nd received signal 102 provided by the formation of the side lobe from a 1st received signal 100 provided by the formation of a main beam, a received signal corresponding to an original main beam is generated. The same oscillator can be utilized also as the oscillators for both the main beam formation and the side lobe formation.

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 reduction of side lobes (unwanted radiation) contained in an ultrasonic beam pattern.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus is an apparatus that forms, for example, a tomographic image or a blood flow image of a living body based on echo data (received signal) obtained by transmitting and receiving ultrasonic waves. In order to improve the image quality of such an ultrasonic image, it is necessary to improve the shape of the ultrasonic beam (transmitting beam and receiving beam).

FIG. 1 shows a so-called electronic focus (transmission focus, reception focus) when transmitting and receiving ultrasonic waves using an array transducer composed of a large number of transducers to form an ultrasonic beam. FIG.
That is, in FIG. 1, reference numeral 10 denotes a sound field pattern. This sound field pattern indicates the intensity distribution of the ultrasonic wave in each direction or each direction, and may be simply referred to as a sound field or a beam pattern. The sound field pattern can be assumed for each of transmission and reception. However, in FIG. 1 and FIGS.

As shown in FIG. 1, an unnecessary side lobe usually appears around a main beam (main pole) in a sound field pattern. Incidentally, the side lobe may indicate each sub-pole, but in the present specification, the entire unnecessary radiation is defined as a side lobe. When such side lobes exist, as is well known, artifacts (false images) that do not exist originally on the ultrasonic image occur, and are a main cause of image quality deterioration. Therefore, there is a strong demand to reduce the side lobe in order to improve the accuracy of the diagnosis in ultrasonic diagnosis. Therefore, in a conventional ultrasonic diagnostic apparatus, it is performed to reduce the size of the ultrasonic vibration elements constituting the array transducer and increase the number of the elements.

[0005]

However, miniaturization of the vibrating element is accompanied by various restrictions, and an increase in the number of elements causes problems such as a complicated configuration and an increase in the cost of the apparatus. However, it is difficult to sufficiently reduce the side lobe.

FIG. 2 shows a sound field pattern when the side lobes are reduced by reducing the pitch of the vibrating element as described above. Although the side lobes 14 have been reduced to some extent, the spread of the beam at the foot cannot be sufficiently suppressed.
It is desired to reduce more effectively.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to effectively reduce side lobes inevitably present in an ultrasonic beam pattern.

It is another object of the present invention to generate a sound field corresponding to a side lobe separately from a normal sound field to specify unnecessary signal components, thereby reducing apparent side lobes by signal processing. It is in.

It is another object of the present invention to approximately generate the above-described side lobe pattern with a simple configuration.

Another object of the present invention is to reduce side lobes while minimizing the cost of the apparatus.

[0011]

To achieve the above object, the present invention provides an ultrasonic diagnostic apparatus which forms an ultrasonic image based on a reception signal obtained by transmitting and receiving an ultrasonic wave. First sound field pattern forming means for forming a main first sound field pattern, and second sound field pattern forming means for forming a second sound field pattern corresponding to a side lobe included in the first sound field pattern; , A first received signal captured by the first sound field pattern and the second received signal.
And a side lobe reducing unit configured to reduce a signal component due to a side lobe by using the second received signal captured by the sound field pattern.

According to the above configuration, the first sound field pattern is formed by the first sound field pattern forming means as a normal beam pattern having directivity. On the other hand, a second sound field pattern similar to the side lobe pattern contained in the first sound field pattern is formed by the second sound field pattern forming means. Here, the sound field pattern is basically formed by transmission and reception of ultrasonic waves, but the second sound field pattern may be formed only at the time of reception as described later. Note that the sound field pattern forming means is a concept including a means for transmitting and receiving ultrasonic waves, a means for controlling transmission and reception (electronic focusing means), and the like. As will be described later, when the second sound field pattern is formed by a single oscillator, the second sound field pattern forming means substantially corresponds to the single oscillator.

A first received signal (normal received signal) is captured under the first sound field pattern, while a second received signal (received signal by side lobe) is captured under the second sound field pattern. And a signal component (signal component due to the main beam) excluding the side lobe component from the comparison and comparison between the two.

FIG. 3 shows a side lobe pattern 18 as a second sound field pattern. The first shown in FIG.
If the pattern 18 corresponding to the above-mentioned side lobe pattern 14 is excluded from the beam pattern 16 as a sound field pattern by, for example, a difference operation, the sound field pattern 20 in which the side lobe 14 is reduced as shown in FIG. Can be obtained. In the present invention, such side lobe reduction is desirably realized by a difference operation between the first received signal and the second received signal, and the signal processing can virtually reduce the side lobe.

In a preferred aspect of the present invention, the difference calculator is provided at a stage prior to a detector for detecting a received signal. Since the phase component remains before detection, it is considered that there is an advantage that the difference calculation can be performed more effectively. Of course, even if the difference calculation is performed after the detection, a certain effect can be obtained.

In a preferred aspect of the present invention, a weighting device is provided for weighting at least one of the first received signal and the second received signal, and a difference between the first received signal and the second received signal after the weighting is provided. Is calculated.

According to the above configuration, by adjusting the levels of both received signals, the second sound field pattern can be more appropriately adapted to the side lobes of the first sound field pattern. The weight value can be changed according to various parameters such as a beam azimuth transmission frequency and a diagnostic depth.

In a preferred aspect of the present invention, the second sound field pattern corresponds to a sound field pattern of a point sound source. This is because, in the first sound field pattern in which side lobes are suppressed to some extent, the side lobe pattern generally approximates a circular or semi-circular pattern as a sound field pattern of a point sound source (single vibrating element). It is based on In a strict sense, it is impossible to form only the side lobe pattern. Therefore, the side lobe is reduced by using such an approximate pattern. The lateral width of the side lobe pattern can be adjusted by the lateral width of the vibrator or can be adjusted by the number of simultaneously driven vibrating elements.

In a preferred aspect of the present invention, the second sound field pattern is formed using one or a plurality of vibration elements. In order to form a sound field pattern of a point sound source, basically, one vibrating element may be used. However, in such a case, a plurality of vibrating elements are used in a case where sound power becomes insufficient. In this case, the received signals from the respective vibrating elements may be simply added, or the sound field pattern may be corrected and corrected using electronic beamforming.
Note that different numbers of vibrating elements may be set for transmission and reception.

In a preferred aspect of the present invention, a first vibrating element array for forming the first sound field pattern is provided separately from the first vibrating element array. And a second vibrating element array to be formed. By providing a dedicated vibrator for forming the second sound field pattern, the second sound field pattern can be made better. In this case, it is desirable that the first vibrating element array and the second vibrating element array are arranged in parallel.

In a preferred aspect of the present invention, the first
A vibration element array for forming both a sound field pattern and the second sound field pattern is included. Such dual use of the vibrator can prevent the cost of the apparatus from increasing. In addition, there is another aspect in which the size of the ultrasonic probe can be prevented.

In a preferred aspect of the present invention, the first sound field pattern and the second sound field pattern are formed by time division. Alternatively, the first sound field pattern and the second sound field pattern are formed simultaneously. When both sound field patterns are formed at the same time, it is necessary to make the frequencies of the ultrasonic waves different from each other or to form two reception sound field patterns by processing the reception signal while sharing the transmission sound field pattern.

In a preferred aspect of the present invention, a phasing addition circuit for phasing and adding a plurality of reception signals from a plurality of vibrating elements for transmitting and receiving ultrasonic waves to generate the first reception signal; And a selection circuit that selects one or a plurality of received signals from among the received signals to generate the second received signal.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 5 is a block diagram showing the overall configuration. In FIG. 1, an ultrasonic probe 30 according to this embodiment includes two transducers, a main beam forming transducer 32 and a side lobe forming transducer 34.
And

FIG. 6 shows such oscillators 32 and 34.
Is shown as a perspective view. Support 6
2 functions as a so-called backing material,
On its upper surface, a main beam forming vibrator 32 and a side lobe forming vibrator 34 are provided. The main beam forming vibrator 32 is a so-called array vibrator, and includes a plurality of vibrating elements 30a. The main beam forming transducer 32 is provided in a conventional ultrasonic probe.

On the other hand, the side lobe forming vibrator 34 is composed of a plurality of vibrating elements 34a, thereby constituting an array vibrator. As shown in FIG. 6, the main beam forming oscillator 32 and the side lobe forming oscillator 34 are provided in parallel and close to each other. In the example shown in FIG. 6, the vibrating element 30a of the main beam forming vibrator 32
Vibrating element 3 of side lobe forming vibrator 34
Although the number of 4a is smaller, a plurality of vibrating elements 30a are simultaneously used when forming the main beam, whereas a single vibrating element 34a is basically used when forming the side lobe. Is used to balance those sound powers. That is, the vibration element 34a having a larger surface area than the vibration element 30a is used. In this embodiment, the main beam forming oscillator 32 is used.
The side lobe forming vibrator 34 and the side lobe forming vibrator 34 are formed separately, but a single array vibrator may be used for both. By the way, in FIG.
The matching layer, acoustic lens, and the like provided on the front side of the and 34 are not shown.

Returning to FIG. 5, the transmitters 36 and 38 are controlled by a transmission controller 40, respectively. Transmitter 3
Numeral 6 supplies a transmission signal to the main beam forming vibrator 32, while a transmitter 38 supplies a transmission signal to the side lobe forming vibrator 34.
In this case, the transmission controller 40 performs control for realizing so-called electronic scanning and electronic focusing. Incidentally, the main beam forming transducer 32 shown in FIG. 6 performs so-called electronic linear scanning, but the present invention can be applied to a case where convex scanning or sector scanning is performed.

The transmitter 38 shown in FIG. 5 includes a plurality of vibrating elements 34a which are actually driven by the main beam forming vibrator 32 among a plurality of vibrating elements 34a constituting the side lobe forming vibrator 34. One corresponding vibration element 30
a is selected and a transmission signal is supplied to the vibrating element.

By the operation of the transmitters 36 and 38 as described above, a beam pattern including a main beam is formed by the main beam forming oscillator 32 in the same manner as in the prior art, while the side lobe forming oscillator 34 has a point sound source. A side lobe pattern similar to the pattern is formed. In the embodiment shown in FIG. 5, such pattern formation is performed in a time-division manner, and basically, a beam pattern including a main beam and a side lobe pattern are alternately formed in conjunction with electronic scanning.

The receiver 42 shown in FIG. 5 includes a plurality of amplifiers and the like, and among a plurality of vibrating elements constituting the main beam forming vibrator 32, a plurality of vibrating elements used for reception are used. It amplifies a plurality of received signals and outputs the amplified signals to the phasing adder 46. In the phasing adder 46, similarly to the conventional device, the phase adjustment is performed under the so-called electronic delay control for each received signal, thereby realizing the phasing addition. That is, electronic focusing is performed. The reception signal added by the phasing adder 46 is referred to as a first reception signal 100 for convenience.

On the other hand, the receiver 44 includes an amplifier and the like, and among a plurality of vibrating elements constituting the side lobe forming vibrator 34, receives a signal output from a vibrating element selected for reception. The signal is amplified and output to the weighting device 48. Here, the received signal output from the receiver 44 is referred to as a second received signal 102. The weighter 48 is a circuit for adjusting the level of the second received signal 102 with the first received signal.

The reception controller 50 functions as reception control means for controlling the phasing adder 46 and the weighting device 48. The reception controller 50 and the above-described transmission controller 40 are controlled by a main controller (not shown).

The buffer 52 temporarily stores the first received signal 100 and adjusts the timing with the second received signal. The first received signal 100 output from the buffer 52 and the second received signal 102 output from the weighter 48 are input to the adder 54, respectively. Specifically, the first received signal 10
A process of subtracting the second received signal from 0 is performed.
Virtually, this corresponds to an operation of deleting the sound field pattern 18 shown in FIG. 3 from the sound field pattern 16 shown in FIG. Received components caused by side lobes are excluded by this subtraction processing. Of course, the side lobe pattern is similar to the actual side lobe pattern, and it is not possible to remove all side lobes in a strict sense. However, according to the processing of this embodiment, the image quality is at least higher than that of the conventional device. Can be improved,
For example, side lobes can be significantly suppressed as compared with a case where the pitch of the vibration element is made finer.

In FIG. 5, the received signal output from the adder 54 is input to a detector 56, which performs detection in the same manner as in the prior art. Then, the received signal is input to a digital scan converter (DSC) 58 after processing such as amplification, and an ultrasonic image is constructed in the DSC 58. And the ultrasonic image is TV
The image is displayed on the monitor 60.

The present invention is also effective when displaying a two-dimensional Doppler image, in which case, for example, a quadrature detector or an autocorrelator may be provided at the subsequent stage of the adder 54.
The weighting amount in the weighting device 48 may be set in advance by experiments or the like, and may be appropriately adjusted according to the frequency of the ultrasonic wave used, the diagnostic depth, and the like.

Next, another embodiment will be described with reference to FIG. Note that the same components as those of the embodiment shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the vibrator for forming the side lobe and the vibrator for forming the main beam are not provided separately, but a vibrator 64 which is also used for them is provided. Specifically, the vibrator 64 has the same structure as the main beam forming vibrator 32 shown in FIG. In the embodiment shown in FIG. 7, the side lobe pattern is formed only at the time of reception. That is, the transmission beam pattern is shared during transmission, and a reception beam pattern close to the point sound source pattern is constructed by selecting some of the received signals during reception. Therefore, when considering transmission and reception, the side lobe pattern cannot be formed more faithfully than the embodiment shown in FIG. 5, but on the other hand, the cost of the device can be reduced by using the vibrator 64 as well.

The receiver 42 and the phasing adder 46 have the same functions as those shown in FIG. 5 and output the first received signal 100 to the adder 54.

On the other hand, the signal selector 66 selects a received signal from one or a plurality of vibrating elements among the plurality of vibrating elements constituting the vibrator 64. In this case, a reception signal corresponding to one or a plurality of vibration elements at the center of the plurality of vibration elements used in forming the main beam is selected. Therefore, when the ultrasonic beam is electronically linearly scanned, the vibrating elements selected by the signal selector 66 are also sequentially scanned. The receiver 44 performs a process such as amplification on the selected received signal, and outputs it to the weighting device 48 as the second received signal 102. Then, the first reception signal 100 and the weighted second reception signal 1
02 is input to the adder 54, and the difference processing of the received signal is performed as described above.

In the embodiment shown in FIG. 7, since the formation of the main beam and the formation of the side lobe are performed simultaneously, a circuit such as the buffer 52 shown in FIG. 5 is unnecessary.

[0042]

As described above, according to the present invention,
Side lobes inevitably included in the ultrasonic beam pattern can be effectively reduced. Further, according to the present invention, an unnecessary signal component can be specified by generating a sound field corresponding to a side lobe separately from a normal sound field, and the apparent side lobe can be reduced by signal processing. Further, according to the present invention, there is an advantage that the side lobe can be reduced by a simple configuration, and an increase in the cost of the apparatus can be avoided as much as possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a sound field pattern including a main beam and side lobes generated near the main beam.

FIG. 2 is an explanatory diagram showing a sound field pattern in which side lobes are somewhat reduced.

FIG. 3 is a diagram showing a sound field pattern corresponding to a side lobe.

FIG. 4 is a diagram showing a sound field pattern in which side lobes are reduced by the method according to the present invention.

FIG. 5 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 6 is a perspective view showing a main beam forming vibrator and a side lobe forming vibrator.

FIG. 7 is a block diagram showing another embodiment according to the present invention.

[Description of Signs] 30 ultrasonic probe, 32 transducer for forming main beam, 3
4 side lobe forming oscillator, 46 phasing adder, 4
8 weighters, 52 buffers, 54 adders, 56
Detector, 66 signal selector.

Claims (11)

[Claims] An ultrasonic diagnostic apparatus that forms an ultrasonic image based on a reception signal obtained by transmitting and receiving an ultrasonic wave, wherein a first sound field pattern that forms a first sound field pattern that mainly includes a main beam is provided. Forming means; second sound field pattern forming means for forming a second sound field pattern corresponding to a side lobe included in the first sound field pattern; and a first reception signal captured by the first sound field pattern. An ultrasonic diagnostic apparatus comprising: a side lobe reducing unit configured to reduce a signal component due to a side lobe by using a second received signal captured by the second sound field pattern. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein said side lobe reducing means is a difference calculator for calculating a difference between said first received signal and said second received signal. . 3. The ultrasonic diagnostic apparatus according to claim 2, wherein the difference calculator is provided at a stage prior to a detector that detects a received signal. 4. The apparatus according to claim 2, further comprising a weighter for weighting at least one of the first received signal and the second received signal, wherein the first received signal and the second received signal are weighted after the weighting. The ultrasonic diagnostic apparatus is characterized in that a difference between the two is calculated. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein the second sound field pattern corresponds to a sound field pattern of a point sound source. 6. The ultrasonic diagnostic apparatus according to claim 5, wherein the second sound field pattern is formed using one or a plurality of vibration elements. 7. The device according to claim 1, wherein the first vibrating element array for forming the first sound field pattern is provided separately from the first vibrating element array, and the second vibrating element array is provided separately from the second vibrating element array.
An ultrasonic diagnostic apparatus comprising: a second vibrating element array for forming a sound field pattern. 8. The ultrasonic diagnostic apparatus according to claim 1, further comprising a vibrating element array for forming both the first sound field pattern and the second sound field pattern. 9. The ultrasonic diagnostic apparatus according to claim 1, wherein the first sound field pattern and the second sound field pattern are formed in a time-division manner. 10. The ultrasonic diagnostic apparatus according to claim 1, wherein the first sound field pattern and the second sound field pattern are formed simultaneously. 11. The phasing addition circuit according to claim 1, wherein a phasing addition circuit that generates the first reception signal by phasing addition of a plurality of reception signals from a plurality of vibration elements that transmit and receive ultrasonic waves, A selecting circuit that selects one or a plurality of received signals from among the plurality of received signals to generate the second received signal.