JPH07236642A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To improve the quality of a diagnostic image by having data which is obtained by radiating a transmission wave to a subject body with a vibrator array swung in a width direction, receiving a reflection wave from a detected the subject body, mutually synchronizing these plural received wave phases, and rectifying and additing phases so as to be made a diagnostic image data. CONSTITUTION:An ultrasonic beam is transmitted to a subject body by elctroscanning the transmitted wave of a vibrator array in an arrangement direction by controlling a vibrator array driving part 21 by a transmission circuit part 22 and the ultrasonic beam is transmitted to the subject body by an electrofocusing means. An echo signal from this subject body is received and each focus position data which is obtained by combining and composition together each electronic operative position and multi- step focusing position by a focus composing/processing part 23 in an arrangement direction of received signals is converted 24 to digital signals and stored in an echo data memory part 25. Thereafter, data in the memory part 25 are made to correspond to data in a swinging control data memory part 28 by a phase rectifying and adding part 26 on the width direction, and the received wave data from the subject body are subjected to phase rectification and addition and output to a displaying part 20 in all swinging positions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the image quality of a diagnostic image of an ultrasonic diagnostic apparatus, and particularly to improving the image quality of a diagnostic image by improving the sensitivity of transmission / reception of an ultrasonic beam. The present invention relates to an ultrasonic diagnostic device.

[0002]

2. Description of the Related Art A diagnostic image obtained by an ultrasonic diagnostic apparatus transmits an ultrasonic beam from an ultrasonic transducer to a subject, and an echo signal from the subject due to this transmission is received by the ultrasonic transducer. , Can be obtained by processing the received signal. There is a strong demand for making this diagnostic image clearer, improving the image quality, and obtaining more accurate information from the living body. As a method to improve the image quality of this diagnostic image,
Various methods for improving the sensitivity of the wave transmission and the wave reception, or improving the sensitivity of the signal processing have been studied.

As a method of improving the sensitivity of the transmitted wave,
A method is conceivable in which the ultrasonic beam is focused by a convex acoustic lens to improve the strength of the transmitted wave. In the vicinity of the focus focused by this convex acoustic lens, the intensity of the transmitted wave is improved, but in the vicinity of the focus, the intensity of the transmitted wave is reduced,
Sensitivity other than near the focal point decreases. As described above, since the convex acoustic lens has only one focal point, it is impossible to obtain a diagnostic image of the entire diagnostic region with high sensitivity.

On the other hand, in a transducer array in which a plurality of ultrasonic transducers having a predetermined length in the width direction are arranged in the arrangement direction, a method of performing multi-point focusing by an electronic focusing method in the arrangement direction has been put into practical use. This electronic focusing method improves the image quality of a diagnostic image by focusing the transmitted and received waves of an ultrasonic transducer in the array direction in multiple stages to improve the intensity of the transmitted and received waves.

There has been a proposal to improve the sensitivity of transmission / reception by performing the electronic focus not only in the arrangement direction but also in the width direction. In this proposal, the ultrasonic transducers are finely cut, and the cut ultrasonic transducers are arranged in a matrix. The ultrasonic transducers arranged in the matrix form need to be sufficiently small in order to sufficiently maintain the transmission strength and improve the position resolution. Since it is difficult to realize an ultrasonic transducer that is sufficiently small and has a sufficient transmission strength, it has not been realized.

On the other hand, "Ishii, Sasaki:" Basic study on synthetic aperture ultrasonic flaw detection method "", non-destructive inspection, Vol. 35, No. 4, P3, which obtains sensitivity continuously in the depth direction.
26, (1985) ”and the like, there is a proposal of an aperture synthesis method. In this aperture synthesis method, the ultrasonic beam is not focused, on the contrary, the ultrasonic beam is continuously diffused in the depth direction, and in the aperture range, transmission and reception are sequentially performed by each ultrasonic transducer of the transducer array, This is a method of improving sensitivity by phasing addition of the received echo signals from the subject. In this aperture synthesis method, it is necessary to make the aperture, which is the length in the array direction of the transducer array, as wide as possible, and to transmit and receive waves from each ultrasonic transducer in the entire area of this aperture. It is necessary to make the aperture angle of the ultrasonic beam of the child as wide as possible. Although it has been possible to continuously obtain sensitivity in the array direction by this aperture synthesis method, it has not reached the sensitivity higher than that of the electronic focusing method.

[0007]

As described above, an ultrasonic diagnostic apparatus using the electronic focus method for focusing the array direction of ultrasonic beams has been put into practical use and diagnostic images have been obtained. However, there is a strong desire to make diagnostic images clearer, improve image quality, and obtain more accurate information from the living body. Therefore, as a method of improving the sensitivity of the diagnostic image, there is a proposal of a method of electronically focusing in the array direction and the width direction, but it is difficult to make the ultrasonic transducer sufficiently small and the transmission strength sufficient. , Not realized. Further, although it has been possible to continuously obtain sensitivity in the array direction by the aperture synthesis method, it has not reached the sensitivity higher than that of the electronic focusing method.

The present invention has been made to solve the above problems, and an object thereof is to realize an ultrasonic diagnostic apparatus which improves the sensitivity of transmission and reception of an ultrasonic beam and improves the quality of diagnostic images. And

[0009]

In an ultrasonic diagnostic apparatus including a transducer array in which a plurality of ultrasonic transducers having a predetermined length in the width direction are arranged in the arrangement direction, the transducer array is mechanically arranged in the width direction. Array oscillating means for oscillating the ultrasonic transducers, proximity focusing means for focusing the transmission of each ultrasonic transducer in the width direction with a short focal distance of each ultrasonic transducer, and transmission / reception of the transducer array. Electronic focusing means for electronically focusing waves in the array direction, and wave transmission for radiating a wave to the subject using the proximity focusing means and the electronic focusing means while oscillating the transducer array by the array oscillating means And a phasing addition unit that receives reflected waves from the subject for each swing position of the transducer array, synchronizes the phases of the plurality of received waves, and then adds them.

[0010]

In the present invention, the focal length is set to a short distance to focus in the width direction, and at a distance from this focus, the ultrasonic beam is diffused in the width direction and mechanically oscillated in the width direction while being aligned in the arrangement direction. An ultrasonic beam is transmitted to the subject while electronically focusing, echo signals from the subject are received at each swing position, the phases of the received waves are synchronized, and the data obtained by phasing and adding the received signals is used as a diagnostic image. It is obtained as data for use.

[0011]

EXAMPLE This example is characterized in that when the aperture synthesis method is applied in the oscillation direction of the transducer array, the ultrasonic wave to be transmitted is intentionally diffused by using an acoustic lens for ultrasonic wave diffusion. And In addition, a convex lens with a large curvature is used as the diffusion acoustic lens to improve the acoustic power in the vicinity of the oscillator where it is difficult to obtain the advantages of aperture synthesis, while transmitting far from the oscillator from as many oscillation positions as possible. It is characterized in that aperture synthesis is efficiently performed using waves.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a principle diagram of transmitting and receiving waves while mechanically oscillating the transducer array in the width direction. In FIG. 1A, an ultrasonic beam is transmitted from a transducer array to a subject while mechanically oscillating the transducer array on a track W in the width direction in the order of points A, B, and C. The case where the reflected wave from the subject by the transmitted wave is received is shown.

If the distances AP, BP, CP from the points A, B, C to the subject P are L _A , L _B , L _C and the speed of sound is c, each point A of the ultrasonic beam due to transmission and reception will be described. , B, C to the subject t _A , t _B , t _C are respectively t _A
= 2L _A / c, t _B = 2L _B / c, t _C = 2L _C / c, and the points A, B, and C have different times from transmission to reception of the reflected beam. FIG. 1B shows a received signal including the time difference between transmission and reception at each point. The time required for transmitting and receiving the ultrasonic beam and the position of the ultrasonic transducer are shown in FIG.
As shown in (b), there is a one-to-one correspondence, and the orbit W
The swing range of is realized as an opening.

FIG. 2 shows a block diagram for realizing the above. In FIG. 2, the transmission circuit unit 22 controls the transducer array drive unit 21, electronically scans the transmission waves of the transducer array in the array direction, and ultrasonically scans the subject with electronic focusing means for multi-stage focusing in the focal length direction. Transmit the beam. An echo signal, which is a reflected wave from the subject, is received by the transducer array, and the received waves are combined and processed by the focus combining processing unit 23 in the array direction to combine and focus each electronic scan position and each focus. Position data is A
The signal is converted into a digital signal in the / D converter 24 and then stored in the echo data memory 25.

Further, as shown in FIG. 1B, each swing position in the width direction of the transducer array and the delay time of transmission / reception have a one-to-one correspondence, and data relating this correspondence, And the equation are stored in the swing control data memory unit 28 in advance.

Further, the transducer array driving section 21 sequentially stores the respective swing positions in the width direction of the transducer array at predetermined swing addresses in the echo data memory section 25. After that, the phasing addition unit 26 in the width direction associates the data of the echo data memory unit 25 with the oscillation control data memory unit 28 to synchronize the phase difference due to the delay time of the wave transmission / reception for each oscillation position, The delay time of the wave transmission / reception is canceled, the wave is transmitted by the electronic focusing means at all swing positions, and the wave reception data from the subject is phased and added. From the above, the swing range is defined as an opening,
Since the data obtained by the electronic focusing means is obtained, the aperture is expanded from the width length of the ultrasonic transducer to the swing region, and the wave receiving sensitivity is improved. The output result of the phasing addition unit 26 in the width direction is converted into an analog signal in the D / A conversion unit 29, and then C
An image is displayed on the RT display unit 20.

FIG. 3 shows the structure of the vibrator array drive section 21.
Shown in. The transducer array driving unit 21 includes an array swinging unit that mechanically swings the transducer array 30 by a motor 34 having an encoder 35 provided in the width direction 31, and an array direction for transmitting waves from the transducer array 30. An electronic focusing means for focusing in multiple stages in the focal length direction 33 while electronically scanning 32, and the transducer array 30 in the width direction 31.
The electronic focusing means includes a transmitting means for radiating a transmitted wave to the subject while swinging the same, and a means for receiving a reflected wave from the subject for each swing position of the transducer array 30. The plurality of waves are received by the phasing addition unit 26 in the width direction of FIG.
After synchronizing the phases with, the phasing addition is performed.

Further, when the convex acoustic lens is used in the width direction, the intensity of the transmitted wave near the focus can be improved and the sensitivity of the diagnostic image near the focus can be improved, but the sensitivity other than near the focus is deteriorated. This has been described in the conventional example. However, the region where the ultrasonic beam is focused is between the ultrasonic transducer and the focal point, and the ultrasonic beam is diffused at a position far from the focal point. Here, if a convex acoustic lens whose focal length is sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used, the one-point focus is not obtained in the focal length direction in the diagnostic region. In this way, the convex acoustic lens having a focal length sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used in the width direction, and the ultrasonic beam is diffused in the width direction at a position far from the focus. Therefore, a method of improving the receiving sensitivity can be considered.

Simulation results of the wave receiving sensitivity when a convex acoustic lens having a focal length sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used in the width direction are shown in FIGS.
Shown in. 6 and 7 show simulation results of wave receiving sensitivity when a convex acoustic lens having a focal length equivalent to that of the conventional one is used in the width direction.

The simulation conditions shown in FIGS. 4 to 7 are as follows: the transmission frequency of the ultrasonic beam is 3.5 MHz, the width of the ultrasonic transducer is 10 mm, and the length in the array direction is infinite.
The number of arrangement in the arrangement direction is 1, and the swinging radius in the width direction is 80 mm
And the receiving sensitivity in the width direction with respect to the depth direction when the subject is the water surface. Here, X [mm] is a distance in the width direction, Y [mm] is a distance in the depth direction of the subject, Z [arbitrary unit] is the wave receiving sensitivity, and the unit lengths of X and Y are respectively:
0.3 and 5 mm.

4 and 5 have a focal length in the width direction of the convex acoustic lens of 20 mm, FIGS. 6 and 7 have a focal length of 80 mm in the width direction of the convex acoustic lens, and FIGS. 5 and 7 show simulation results when swinging in the width direction is performed without swinging in the direction.

First, a simulation result in the case of not swinging in the width direction will be examined. In FIG. 6 in which the focal length is 80 mm, the received wave is narrowed to some extent in the depth direction, but the sensitivity is reduced in the area other than the vicinity of the focus and the sound field near the transducer is reduced. Is disturbed. On the other hand, in FIG. 4 in which the focal length is 20 mm, the sensitivity in the vicinity of the transducer is increased and the sensitivity is reduced in other cases, but the sound field is uniformly spread and the sound field is not disturbed.

Next, the simulation result when swinging in the width direction will be examined. In FIG. 7 in which the focal length is 80 mm, the sensitivity is improved in almost the entire depth direction as compared with FIG. 6 in the case where the rocking is not performed, but in FIG. In the field, the received waves are overlapped in the width direction due to the oscillation in the width direction, and the disturbance of the sound field is further expanded at the central portion in the width direction. On the other hand, the focal length is 2
In FIG. 5, which is 0 mm, FIG.
In Fig. 5, although the sound field was not disturbed, the sensitivity was deteriorated except in the vicinity of the transducer. This means that in Fig. 5, the sensitivity is not affected in the sound field and the sensitivity is almost over the entire depth direction. Is rising.

As described above, the convex acoustic lens whose focal length is sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used,
In the diagnostic area, ultrasonic waves are diffused in the width direction, mechanically oscillated in the width direction, and the received waves are aperture-synthesized to continuously improve the receiving sensitivity in the depth direction. Was done.

In the above description, the case of swinging in an arc shape as the swing in the width direction is shown, but the same effect can be obtained by swinging in a straight line in the width direction. Also, as a method of diffusing the transmitted wave in the width direction, the case where a convex acoustic lens whose focal length is sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used is shown. The same effect can be obtained by diffusing in the direction. That is,
An acoustic lens for ultrasonic diffusion may be used.

[0026]

As described above, in the present invention,
By using the data obtained by phasing and addition as diagnostic image data, aperture synthesis is performed in the width direction, the receiving sensitivity in the width direction is continuously improved in the depth direction, and electronic focusing is performed in the array direction. Improve the strength of transmitted and received waves in the direction. By electronically focusing in the array direction and combining apertures in the width direction in this way, the transmitted / received wave intensity is made equal to that of the electronic focus method, and the wave receiving sensitivity is made higher than that of the electronic focus method to improve the image quality of the diagnostic image. It is possible to provide an ultrasonic diagnostic apparatus for the above.

[Brief description of drawings]

FIG. 1 is a principle diagram of transmitting and receiving a wave while swinging a transducer array according to an embodiment of the present invention in a width direction.

FIG. 2 is a block configuration diagram for transmitting and receiving a wave while swinging the transducer array according to the embodiment of the present invention in the width direction.

FIG. 3 is a configuration diagram of a transducer array driving unit according to an embodiment of the present invention.

FIG. 4 is a diagram showing a simulation result of a sensitivity distribution of received waves of the ultrasonic transducer when the focal length is 20 mm and there is no oscillation.

FIG. 5 is a focal length of 20 mm according to an embodiment of the present invention,
It is a figure which shows the simulation result of the sensitivity distribution of the received wave of an ultrasonic transducer | vibrator in the case of an oscillation.

FIG. 6 is a diagram showing a simulation result of a sensitivity distribution of received waves of the ultrasonic transducer when the focal length is 80 mm and there is no oscillation.

FIG. 7 is a diagram showing a simulation result of a sensitivity distribution of received waves of the ultrasonic transducer when the focal length is 80 mm and there is swinging.

[Explanation of symbols]

 21 Transducer Array Drive Unit 23 Array Focus Focus Processing Unit 25 Echo Data Memory Unit 26 Width Direction Phasing Addition Unit 27 Oscillation Control Unit 28 Oscillation Control Data Memory Unit 30 Oscillator Array 31 Array Direction 32 Width Direction 33 Focal length direction 34 Motor 35 Encoder

Claims (1)

[Claims] 1. An ultrasonic diagnostic apparatus comprising a transducer array in which a plurality of ultrasonic transducers having a predetermined length in the width direction are arranged in the arrangement direction, wherein the transducer array is mechanically oscillated in the width direction. Array oscillating means, proximity focusing means for focusing the ultrasonic transducers in the width direction by making the focal length of each of the ultrasonic transducers a short distance, and transmitting and receiving waves of the transducer array in the array direction. Electronic focusing means for electronically focusing, wave sending means for oscillating the transducer array by the array oscillating means, and radiating a wave to a subject using the near field focusing means and the electronic focusing means; An ultrasonic diagnostic apparatus comprising: a phasing addition unit that receives reflected waves from the subject for each swing position of the child array, synchronizes the phases of the plurality of received waves, and then adds them. Disconnection device.