JP2723464B2 - 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 a technique for improving the image quality of a diagnostic image of an ultrasonic diagnostic apparatus, and more particularly to improving the image quality of a diagnostic image by improving the sensitivity of transmission and reception of an ultrasonic beam. The present invention relates to an ultrasonic diagnostic apparatus.

[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 receives an echo signal from the subject by the transmission by the ultrasonic transducer. , By performing signal processing on the received signal. There is a strong demand to make this diagnostic image clearer, improve the image quality, and obtain more accurate information from the living body. As a method of improving the image quality of this diagnostic image,
Various methods have been studied, such as improving the sensitivity of the transmission and reception, or the sensitivity of the signal processing.

As a method for improving the sensitivity of the transmission,
A method of converging the ultrasonic beam with the convex acoustic lens and improving the intensity of the transmitted wave can be considered. In the vicinity of the focal point focused by the convex acoustic lens, the intensity of the transmitted wave increases, but in the vicinity other than the vicinity of the focal point, the intensity of the transmitted wave decreases,
The sensitivity other than near the focal point decreases. As described above, since the convex acoustic lens has a single focal point, it is impossible to obtain a diagnostic image of the entire diagnostic area 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 to practical use. In the electronic focusing method, the transmission and reception of the ultrasonic transducers are focused in multiple directions in the arrangement direction, and the intensity of the transmission and reception is improved, thereby improving the image quality of the diagnostic image.

There is a proposal to improve the sensitivity of transmitting and receiving waves by performing the electronic focusing not only in the arrangement direction but also in the width direction. In this proposal, the ultrasonic vibrator is finely cut, and the cut ultrasonic vibrators are arranged in a matrix. The ultrasonic transducers arranged in a matrix need to be sufficiently small in order to maintain sufficient transmission intensity and improve positional resolution. Since it is difficult to realize an ultrasonic vibrator that is sufficiently small and has sufficient transmission strength, it has not been realized.

On the other hand, "Ishii, Sasaki:" Basic Study on Synthetic Aperture Ultrasonic Testing ", which obtains sensitivity continuously in the depth direction, Nondestructive inspection, Vol.35, No.4, P3
26, (1985) "and the like. This aperture synthesis method does not converge the ultrasonic beam, conversely, continuously diffuses the ultrasonic beam in the depth direction, in the aperture range, sequentially performs transmission and reception by each ultrasonic transducer of the transducer array, This is a method of improving the sensitivity by phasing and adding the reception of the echo signal from the subject. In this aperture synthesizing method, it is necessary to make the aperture, which is the length of the transducer array in the arrangement direction, as wide as possible, and to transmit and receive waves from each ultrasonic transducer over 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 the sensitivity is continuously obtained in the arrangement direction by the aperture synthesis method, the sensitivity has not been obtained as high as that obtained by the electronic focus method.

[0007]

As described above, an ultrasonic diagnostic apparatus using an electronic focusing method for focusing the arrangement direction of ultrasonic beams has been put to practical use, and a diagnostic image has been obtained. However, there is a strong demand to make diagnostic images clearer, improve image quality, and obtain more accurate information from living bodies. For this reason, as a method of improving the sensitivity of a diagnostic image, there has been proposed a method of performing electronic focusing in the arrangement direction and the width direction. However, it is difficult to make the ultrasonic vibrator sufficiently small and transmit wave intensity sufficiently. , Not realized. In addition, although the sensitivity is continuously obtained in the array direction by the aperture synthesis method, it has not been possible to obtain a sensitivity higher than that of the electronic focus method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to realize an ultrasonic diagnostic apparatus which improves the sensitivity of transmitting and receiving ultrasonic beams and improves the quality of diagnostic images. And

[0009]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
According to the present invention, a plurality of ultrasonic vibrations arranged in a first direction are provided.
A one-dimensional vibrator that is composed of transducers and transmits and receives ultrasonic waves.
Ray and ultrasonic waves transmitted and received by the transducer array
A diffused acoustic lens that diffuses in a second direction orthogonal to the first direction
And mechanically scans the transducer array in the second direction.
Mechanical scanning means for performing the ultrasonic scanning in the first direction.
Electronic focusing means for performing child scanning and electronic focusing
And a pattern acquired at each mechanical scanning position of the vibrator array.
Aperture for phasing and adding a number of received signals in the second direction
Combining means .

[0010]

According to the present invention, in the first direction (arrangement direction),
Electronic focus is performed in the second direction (the ultrasonic vibrator
In the width direction), phasing addition by aperture synthesis is performed.
That is, a composite focus is performed. Aperture synthesis
In this case, the received signal acquired at each mechanical scanning position is used.
You. Therefore, the ultrasonic waves are diffused in the second direction.

[0011]

This embodiment is characterized in that transmitted ultrasonic waves are intentionally diffused using an acoustic lens for ultrasonic diffusion when the aperture synthesis method is applied to the oscillation direction of the transducer array. And In addition, a convex lens having a large curvature is used as the diffusion acoustic lens, and the acoustic power is improved in the vicinity of the vibrator where it is difficult to obtain the advantage of aperture synthesis. It is characterized in that aperture synthesis is performed efficiently 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 swinging the transducer array in the width direction. FIG. 1A shows an example in which an ultrasonic beam is transmitted from a transducer array to a subject while mechanically swinging a transducer array on a trajectory W in a width direction in the order of points A, B, and C. This shows a case where a reflected wave from a subject due to transmission is received.

If the distances AP, BP, and CP from the points A, B, and C to the subject P are L _A , L _B , and L _C , and the sound velocity is c, each point A of the ultrasonic beam due to the transmitted and received waves is obtained. , B, C to the subject, the round trip times t _A , t _B , t _C are respectively t _A
= 2L _A / c, t _B = 2L _B / c, and 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 a time difference between transmitted and received waves 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), the trajectory W
Is realized as an opening.

FIG. 2 is a block diagram for realizing the above. In FIG. 2, a transmitting circuit unit 22 controls a vibrator array driving unit 21 to electronically scan the transmitted wave of the vibrator array in an array direction and to apply ultrasonic waves to an object by electronic focusing means for performing multi-stage focusing in a focal length direction. Transmit the beam. Echo signals, which are reflected waves from the subject, are received by the vibrator array, and the received waves are combined by the focus combining processing unit 23 in the array direction by combining each electronic scanning position and the multi-stage focus position. A for position data
After being converted into a digital signal by the / D converter 24, the digital signal is stored in the echo data memory 25.

Further, as shown in FIG. 1B, each oscillation position in the width direction of the vibrator array and the delay time of the transmitted / received wave correspond to one-to-one, and data for associating this correspondence, And the equation are stored in the swing control data memory unit 28 in advance.

The transducer array driving section 21 sequentially stores the echo data in a predetermined address of the echo data memory section 25 for each swing position of all the swing positions in the width direction of the transducer array. After that, the data in the echo data memory unit 25 and the oscillation control data memory unit 28 are made to correspond to each other by the width direction phasing addition unit 26 so that the phase difference due to the delay time of the transmission / reception wave for each oscillation position is synchronized. The delay time of the transmission / reception wave is canceled, the wave is transmitted by the electronic focusing means at all the oscillating positions, and the reception data from the subject is phased and added. As described above, the swing range is set to the opening,
Since data is obtained by the electronic focusing means, the aperture is widened from the width of the ultrasonic transducer to the swing area, and the receiving sensitivity is improved. After the output result of the width direction phasing addition unit 26 is converted into an analog signal by the D / A conversion unit 29,
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 vibrator array drive unit 21 includes an array oscillating unit that mechanically oscillates the vibrator array 30 by a motor 34 provided with an encoder 35 in the width direction 31, and transmits a wave from the vibrator array 30 in the arrangement direction. An electronic focusing means for performing multi-stage focusing in the focal length direction 33 while electronically scanning the transducer array 32;
A transmitting means for radiating a wave to the subject by the electronic focusing means while oscillating, and a means for receiving a reflected wave from the subject for each swing position of the vibrator array 30. The plurality of received waves are supplied to the phasing addition section 26 in the width direction of FIG.
After the phases are synchronized with each other, phasing addition is performed.

When the convex acoustic lens is used in the width direction, the intensity of the transmitted wave near the focal point can be improved and the sensitivity of the diagnostic image near the focal point can be improved, but the sensitivity other than near the focal point 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 area is used, the focal point in the diagnostic area will not be one point even in the focal length direction. As described above, 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 focal point. Thus, a method of improving the wave receiving sensitivity can be considered.

FIGS. 4 and 5 show simulation results of the receiving sensitivity when a convex acoustic lens whose focal length is sufficiently shorter than the distance in the shortest depth direction of the diagnostic area is used in the width direction.
Shown in FIGS. 6 and 7 show simulation results of the wave receiving sensitivity when a convex acoustic lens having a focal length equivalent to that of the related art is used in the width direction.

The simulation conditions shown in FIGS. 4 to 7 are as follows: the transmitting frequency of the ultrasonic beam is 3.5 MHz, the width of the ultrasonic transducer is 10 mm, the length in the arrangement direction is infinite,
The number of arrangement in the arrangement direction is one, and the swing 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 the distance in the width direction, Y [mm] is the distance in the depth direction of the subject, Z [arbitrary unit] indicates the receiving sensitivity, and the unit length of X and Y is,
0.3 and 5 mm.

FIGS. 4 and 5 show that the focal length of the convex acoustic lens in the width direction is 20 mm, FIGS. 6 and 7 show that the focal length of the convex acoustic lens in the width direction is 80 mm, and FIGS. FIGS. 5 and 7 show the simulation results in the case where the swing in the width direction is not performed.

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

Next, a simulation result when swinging in the width direction is examined. In FIG. 7 in which the focal length is 80 mm, although the sensitivity is improved in almost the entire region in the depth direction as compared with FIG. 6 in the case where the swing is not performed, in FIG. In the field, the received waves overlap in the width direction due to the swing in the width direction, and the disturbance of the sound field is further increased at the center in the width direction. On the other hand, if the focal length is 2
In FIG. 5, which is 0 mm, FIG.
In FIG. 5, although the disturbance of the sound field did not occur, the sensitivity was reduced except in the vicinity of the vibrator. This is shown in FIG. Is rising.

As described above, a convex acoustic lens whose focal length is sufficiently shorter than the distance in the shortest depth direction of the diagnostic region is used.
It is shown that the ultrasonic beam is diffused in the width direction and mechanically oscillated in the width direction in the diagnostic area, and the reception sensitivity is continuously improved in the depth direction by aperture synthesis of the reception wave. Was done.

In the above description, the swing in the width direction has been described as swinging in an arc shape. However, the same effect can be obtained by swinging in a straight line in the width direction. Also, as a method of diffusing the transmission in the width direction, a 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 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, according to the present invention ,
The image quality of the diagnostic image can be improved .

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration in which a transducer array according to an embodiment of the present invention transmits and receives waves while swinging in a width direction.

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

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

FIG. 5 shows a focal length of 20 mm according to one embodiment of the present invention.
FIG. 9 is a diagram illustrating a simulation result of a sensitivity distribution of a received wave of the ultrasonic transducer in a case where there is oscillation.

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

FIG. 7 is a diagram illustrating a simulation result of a sensitivity distribution of a received wave of the ultrasonic transducer when the focal length is 80 mm and there is oscillation.

[Explanation of symbols]

 Reference Signs List 21 transducer array driving section 23 focus synthesis processing section in arrangement direction 25 echo data memory section 26 phasing addition section in width direction 27 swing control section 28 swing control data memory section 30 transducer array 31 arrangement direction 32 width direction 33 Focal length direction 34 Motor 35 Encoder

Claims (2)

(57) [Claims] 1. A plurality of ultrasonic vibrations arranged in a first direction
A one-dimensional vibrator that is composed of transducers and transmits and receives ultrasonic waves.
Ray and ultrasonic waves transmitted and received by the transducer array are transmitted to the first direction.
A diffused acoustic lens that diffuses in a second direction orthogonal to the direction, and a machine that mechanically scans the transducer array in the second direction
Mechanical scanning means, electronic scanning and electronic scanning of ultrasonic waves in the first direction.
Electronic focusing means for performing scum, and a plurality of electronic focusing means obtained at each mechanical scanning position of the vibrator array
Aperture synthesis for phasing and adding received signals in the second direction
Ultrasonic diagnostic apparatus characterized by comprising: a means. (2) The device of claim 1, The diffuse acoustic lens focuses near the array transducer
It is a convex acoustic lens with a distance
Ultrasound diagnostic equipment.