JP2001353155A - Ultrasonic wave transmission/reception method and device, and ultrasonic photographing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ultrasonic wave transmission/reception method and equipment therefor a by which the harmonic echoes of a wide band can be obtained even by unipolar drive, and provided ultrasonic photographing equipment provided with the device. SOLUTION: Ultrasonic waves having a sound pressure sufficient for causing waveform distortion accompanying propagation are transmitted (608) and the ultrasonic waves provided with the sound pressure insufficient for causing the waveform distortion accompanying the propagation are transmitted in the same direction as the transmitted waves (608'). The echoes of the two kinds of the ultrasonic waves are respectively received (6161 and 616') and the signals of the difference of the two echoes are formed (618).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transmission / reception method and apparatus, and an ultrasonic imaging apparatus, and more particularly, to a method for transmitting an ultrasonic wave to produce a harmonic echo.
cs echo) ultrasonic transmission and reception method and apparatus,
Also, the present invention relates to an ultrasonic imaging apparatus including such an ultrasonic transmitting / receiving apparatus.

[0002]

2. Description of the Related Art In ultrasonic imaging, an image is generated based on a harmonic echo of a transmitted ultrasonic wave, that is, a harmonics echo. Such ultrasonic imaging is called harmonics imaging (harmonics ima).
ging). The harmonics echo image has a unique clinical value different from the fundamental echo image.

[0003] Harmonics imaging is performed using a pulse inversion method. In the pulse inversion method, the ultrasonic wave is transmitted by changing the phase by 180 ° between the first time and the second time by the bipolar drive of the ultrasonic transducer, and the sum of echoes of the ultrasonic waves is obtained. Cancels the fundamental wave echo and obtains a harmonics echo.

When performing harmonic imaging without using the pulse inversion method, a filter (fil) is used.
ter) to remove a fundamental wave component from the echo reception signal to obtain a harmonics echo.

[0005]

[0006] Depending on the configuration of the circuit for driving the ultrasonic transducer, a unipolar (un-
In some cases, only bipolar driving can be performed, and bipolar driving cannot be performed. In this case, a filter for removing the fundamental wave echo is used. However, the filter removes not only the fundamental wave echo but also the harmonics echo having a frequency close to the fundamental wave echo, so that the frequency band of the harmonics echo is narrowed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic transmitting / receiving method and apparatus for obtaining a wideband harmonics echo even with unipolar driving, and an ultrasonic imaging apparatus equipped with such an ultrasonic transmitting / receiving apparatus. .

[0007]

Means for Solving the Problems (1) According to one aspect of the present invention for solving the above-described problems, an ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation is transmitted, and a waveform accompanying propagation is transmitted. An ultrasonic wave having a sound pressure that is insufficient to cause distortion is transmitted in the same direction as the transmitted wave, echoes of the transmitted two types of ultrasonic waves are respectively received, and a difference between the received two echoes is calculated. A method for transmitting and receiving an ultrasonic wave, comprising: forming a signal.

According to the invention from this viewpoint, the difference between an echo for an ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation and an echo for an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation is obtained. , The fundamental echo included in both of them can be canceled to extract a harmonics echo.

(2) According to another aspect of the present invention for solving the above-mentioned problems, an ultrasonic wave having a sound pressure sufficient to cause waveform distortion due to propagation is transmitted, and waveform distortion due to propagation is not sufficient. An ultrasonic wave having a sound pressure is transmitted in the same direction as the transmitting wave, echoes of the two types of transmitted ultrasonic waves are respectively received, and according to a difference in transmitted sound pressure between the two received echoes. An ultrasonic transmission / reception method, comprising: adjusting a gain to form a signal representing a difference between the adjusted two echoes.

According to the invention from this viewpoint, the echo for the ultrasonic wave having a sound pressure sufficient to cause the waveform distortion accompanying the propagation and the echo for the ultrasonic wave having the sound pressure insufficient to cause the waveform distortion accompanying the propagation, Since the difference is obtained by adjusting the gain in accordance with the difference in pressure, it is possible to more completely cancel out the fundamental wave echo included in both, and to extract the harmonics echo.

(3) According to another aspect of the invention for solving the above-mentioned problems, the transmission directions of the two types of ultrasonic waves are sequentially changed, as described in (1) or (2). Is an ultrasonic transmission / reception method.

In the invention according to this aspect, a plurality of directions can be scanned by the ultrasonic waves by sequentially changing the directions of the transmission of the ultrasonic waves. (4) According to another aspect of the invention for solving the above-described problems, a first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause a waveform distortion associated with propagation, and a waveform associated with propagation. A second ultrasonic transmitting means for transmitting ultrasonic waves having a sound pressure insufficient to cause distortion; an echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves; And a difference signal forming means for forming a signal of a difference between two echoes.

According to the invention from this viewpoint, the difference between an echo for an ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation and an echo for an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation is obtained. , The fundamental echo included in both of them can be canceled to extract a harmonics echo.

(5) According to another aspect of the present invention, there is provided a first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause a waveform distortion accompanying propagation, and A second ultrasonic wave transmitting means for transmitting ultrasonic waves having a sound pressure insufficient to cause waveform distortion associated with, an echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves, Gain adjustment means for adjusting the gain of the two received echoes according to the difference in transmission sound pressure, and difference signal formation means for forming a signal of the difference between the adjusted two echoes. This is an ultrasonic transmitting and receiving apparatus.

According to the invention from this viewpoint, an echo for an ultrasonic wave having a sound pressure sufficient to cause waveform distortion due to propagation and an echo for an ultrasonic wave having a sound pressure insufficient to cause waveform distortion due to propagation are considered as sound. Since the difference is obtained by adjusting the gain in accordance with the difference in pressure, it is possible to more completely cancel out the fundamental wave echo included in both, and to extract the harmonics echo.

(6) According to another aspect of the invention for solving the above-mentioned problem, the first and second driving means sequentially change the direction of the transmission wave. An ultrasonic transmitting / receiving device according to 5).

In the invention according to this aspect, by changing the azimuth of the transmission of the ultrasonic wave sequentially, it is possible to scan a plurality of azimuths with the ultrasonic wave. (7) According to another aspect of the present invention, there is provided a first ultrasonic wave transmitting means for transmitting ultrasonic waves having a sound pressure sufficient to cause waveform distortion accompanying propagation, and a waveform associated with propagation. A second ultrasonic transmitting means for transmitting ultrasonic waves having a sound pressure insufficient to cause distortion; an echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves; An ultrasonic imaging apparatus comprising: a difference signal forming unit that forms a difference signal between two echoes; and an image generating unit that generates an image based on the formed difference signal.

According to the invention from this viewpoint, the difference between the echo for an ultrasonic wave having a sound pressure sufficient to cause waveform distortion due to propagation and the echo for an ultrasonic wave having a sound pressure insufficient to cause waveform distortion due to propagation is obtained. , The fundamental echo included in both of them can be canceled to extract a harmonics echo. Thus, harmonic imaging can be performed.

(8) According to another aspect of the present invention, there is provided a first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause a waveform distortion accompanying propagation, A second ultrasonic wave transmitting means for transmitting ultrasonic waves having a sound pressure insufficient to cause waveform distortion associated with, an echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves, Gain adjusting means for adjusting the gain of the two received echoes according to the difference in the transmitted sound pressure, difference signal forming means for forming a signal of the adjusted difference between the two echoes, And an image generating means for generating an image based on the ultrasonic image.

According to the invention from this viewpoint, the echo for an ultrasonic wave having a sound pressure sufficient to cause waveform distortion due to propagation and the echo for an ultrasonic wave having a sound pressure insufficient to cause waveform distortion due to propagation are determined. Since the difference is obtained by adjusting the gain in accordance with the difference in pressure, it is possible to more completely cancel out the fundamental wave echo included in both, and to extract the harmonics echo. Thus, harmonic imaging can be performed.

(9) According to another aspect of the invention for solving the above-mentioned problem, the first and second driving means sequentially change the direction of the transmission wave. An ultrasonic imaging apparatus according to 8).

In the invention according to this aspect, the ultrasonic waves can be scanned in a plurality of directions by sequentially changing the directions of the transmitted ultrasonic waves.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

As shown in FIG. 1, the present apparatus has an ultrasonic probe 2. The ultrasound probe 2 has an array of a plurality of ultrasound transducers (not shown). Each ultrasonic transducer is made of, for example, PZT (lead zirconate titanate (Zr) (Pb)) ceramics (ceramic).
s) and the like.

The ultrasonic probe 2 is moved by the operator to the object 4
Used in contact with The ultrasonic probe 2 has a transmitting / receiving unit 6
It is connected to the. The transmission / reception unit 6 supplies a drive signal to the ultrasonic probe 2 to transmit ultrasonic waves. The transmitting and receiving unit 6
Further, the echo signal received by the ultrasonic probe 2 is received.

The portion composed of the ultrasonic probe 2 and the transmitting / receiving section 6 is an example of the embodiment of the ultrasonic transmitting / receiving apparatus according to the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

FIG. 2 shows a block diagram of the transmission / reception section 6. As shown in the figure, the transmission / reception unit 6 transmits a signal
ing) generating unit 602. The transmission timing generation unit 602 periodically generates a transmission timing signal to transmit a transmission beamformer (beamf).
(ormer) 604.

The transmission beamformer 604 performs beamforming of transmission, and generates a beamforming signal for forming an ultrasonic beam in a predetermined direction based on a transmission timing signal. The beam forming signal is composed of a plurality of drive signals to which a time difference corresponding to the azimuth is given. The beam forming is controlled by a control unit 18 described later, and changes the direction of the transmission every two periods of the transmission timing signal. That is, the same azimuth is maintained for two successive cycles.

The output signal of the transmission beam former 604 is supplied to a driver 6 by a switching unit 606.
08 or 608 '. Switching unit 606
Is controlled by the control unit 18 described later, and the driver 608 side and the driver 60
It alternately switches to the 8 'side.

The driver 608 or 608 ′ to which the beam forming signal has been input amplifies the input signal and inputs the amplified signal to the transmission / reception switching unit 606. The amplification factor of the driver 608 is larger than the amplification factor of the driver 608 ′.
Therefore, the output signal of the driver 608 is
8 'is larger than the output signal.

The transmission / reception switching unit 610 inputs the amplified beam forming signal, that is, the drive signal to the ultrasonic transducer array. In ultrasonic transducer arrays, the transmission aperture
The ultrasonic transducers respectively generate ultrasonic waves having a phase difference corresponding to the time difference between the drive signals. By the wavefront synthesis of the ultrasonic waves, an ultrasonic beam is formed along a sound ray in a predetermined direction.

When the sound pressure of the ultrasonic beam is driven by the output signal of the driver 608, the sound pressure of the driver 608 'is higher.
Higher than when driven by the output signal of When the sound pressure of the ultrasonic beam exceeds a certain value due to the non-linearity of the ultrasonic wave propagation inside the object 4, the waveform is distorted in the process of ultrasonic wave propagation, and harmonics are generated accordingly.

There is a relationship between the sound pressure and the harmonic content as conceptually shown in FIG.
If it exceeds, the harmonic content increases rapidly. Predetermined value P
Harmonics are negligible within a range not exceeding c.

The output signal of the driver 608 has an amplitude that generates an ultrasonic beam exceeding the sound pressure Pc. The output signal of driver 608 'has an amplitude that produces an ultrasonic beam that does not exceed sound pressure Pc. This amplitude is such that the sound pressure of the ultrasonic beam is as close to Pc as possible, and the SNR (sig
It is preferable from the viewpoint of improving nal-to-noise ratio.

The portion composed of the transmission beam former 604, the switching unit 606, the driver 608, the transmission / reception switching unit 610 and the ultrasonic probe 2 is an example of the first ultrasonic transmitting means according to the present invention. Transmitting beamformer 604, switching unit 606, driver 6
08 ', the transmission / reception switching unit 610 and the ultrasonic probe 2 are an example of an embodiment of the second ultrasonic wave transmitting means in the present invention.

The transmission / reception switching unit 610 is connected to a reception beam former 612. Transmission / reception switching unit 61
0 indicates a plurality of echo signals received by the receiving aperture in the ultrasonic transducer array,
Input to 12.

The reception beamformer 612 performs beamforming of a reception wave corresponding to a sound ray of a transmission, adjusts the phase by giving a time difference to a plurality of reception echoes, and then adds them to a predetermined value. An echo reception signal is formed along the azimuth sound ray. The receiving beamforming is controlled by a control unit 18 described later, and changes the direction of the received wave every two periods of the transmission timing signal. That is, the same azimuth is maintained for two successive cycles.

The output signal of the receiving beamformer 612, that is, the echo reception signal for one sound ray, is supplied to the switching unit 614.
Through the memory 616 or 616 '. The switching unit 614 is controlled by the control unit 18 described later, and alternately switches to the memory 616 side and the memory 616 'side for each cycle of the transmission timing. by this,
The echo reception signals corresponding to one sound ray are stored alternately.

Ultrasonic probe 2, transmission / reception switching unit 61
The portion consisting of the zero, the receiving beam former 612, the switching unit 614, and the memories 616, 616 'is an example of the embodiment of the echo receiving means in the present invention.

The echo reception signals stored in the memories 616 and 616 'are read out under the control of the control unit 18 described later, and the difference between them is obtained by the subtraction unit 618. The subtraction unit 618 is an example of the embodiment of the difference signal forming means in the present invention.

The transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by a transmission timing signal generated by the transmission timing generation unit 602. The azimuth of the sound ray is changed by a predetermined amount by the transmission beam former 604 and the reception beam former 612 every two periods of the transmission timing.

As a result, two sound rays (directions)
The transmission and reception of ultrasonic waves are performed every time. First time is driver 608
The transmission of the ultrasonic beam of high sound pressure and the echo reception thereof by the output signal of the above, and the second transmission of the ultrasonic beam of low sound pressure by the output signal of the driver 608 'and the reception of the echo thereof.

The echo reception signal obtained in the first transmission / reception includes a fundamental wave echo and a harmonics echo. The echo reception signal obtained by the second transmission / reception is only the fundamental wave echo and does not include the harmonics echo.

By calculating the difference between these echoes stored in the memories 616 and 616 'by the subtraction unit 618, a fundamental wave echo commonly included in the two can be canceled to obtain a harmonics echo. .

Since a harmonics echo is obtained in this manner, there is no need for a bipolar driving means for transmitting ultrasonic waves having a phase difference of 180 ° between the first and second times, unlike the conventional pulse inversion method. . Therefore,
All of the drivers 608 and 608 'need only perform unipolar driving, and the configuration can be simplified.

Further, since a filter for removing the fundamental wave echo is not used unlike the conventional art, the band of the harmonics echo is not reduced, and a high-band harmonics echo can be obtained.

To further completely cancel the fundamental wave echo, for example, as shown in FIG. 4, a gain adjustment unit 620 is provided in the preceding stage of the memory 616 'so that the level of the fundamental wave echo is made the same in the first time and the second time. Is preferred. In this case, the gain of the gain adjustment unit 6202 is, for example, equivalent to the amplitude ratio of the output signals of the drivers 608 and 608 '. The gain adjustment unit 620 is an example of an embodiment of the gain adjustment means in the present invention.

The gain adjustment may be performed on the input side of the memory 616. However, in this case, the gain of the echo reception signal is, for example, equivalent to the reciprocal of the amplitude ratio of the output signals of the drivers 608 and 608 '.

The transmitting / receiving section 6 scans the inside of the object 4 in the order of sound rays. The sound ray sequential scanning is as shown in FIG. 5, for example. That is, the sound ray 2 extending in the z direction from the radiation point 200
In step 02, the fan-shaped two-dimensional area 206 is scanned in the θ direction, and a so-called sector scan is performed.

When the transmitting and receiving apertures are formed by using a part of the ultrasonic transducer array, the apertures are sequentially moved along the array to perform scanning as shown in FIG. 6, for example. Can be.
That is, the sound ray 202 emitted from the radiation point 200 in the z direction
Is moved in parallel along the linear trajectory 204, thereby scanning the rectangular two-dimensional area 206 in the x-direction, thereby performing a so-called linear scan.

Note that the ultrasonic transducer array is
A so-called convex array (convex array) formed along an arc extending in the ultrasonic wave transmission direction.
In the case of y), the radiation point 2 of the sound ray 202 is, for example, as shown in FIG.
It is needless to say that so-called convex scanning can be performed by moving 00 along the arc-shaped trajectory 204 and scanning the fan-shaped two-dimensional area 206 in the θ direction.

The transmission / reception unit 6 is connected to a B-mode (mode) processing unit 10. The harmonic echo reception signal for each sound ray output from the transmission / reception unit 6 is input to the B-mode processing unit 10. Hereinafter, the harmonics echo reception signal is also simply referred to as an echo reception signal.

The B-mode processing section 10 forms B-mode image data. As shown in FIG. 8, the B-mode processing unit 10 includes a logarithmic amplification unit 102 and an envelope detection unit 104. The B-mode processing unit 10 logarithmically amplifies the echo reception signal in the logarithmic amplification unit 102, performs envelope detection in the envelope detection unit 104, and indicates a signal representing the intensity of the echo at each reflection point on the sound ray, that is, the A scope A (scope) signal is obtained, and B-mode image data is formed using the instantaneous amplitude of the A scope signal as a luminance value.

The B mode processing unit 10 is connected to the image processing unit 14. The image processing unit 14 includes the B-mode processing unit 10
In this case, a B-mode image is generated on the basis of the data input from. The portion including the B-mode processing unit 10 and the image processing unit 14 is an example of an embodiment of the image generation unit according to the present invention.

As shown in FIG. 9, the image processing unit 14 includes an input data memory 142 connected by a bus 140, and a digital scan con.
verter 144, an image memory 146, and a processor 148.

The B-mode image data input from the B-mode processing unit 10 for each sound ray is stored in the input data memory 142. The data in the input data memory 142 is scan-converted by the digital scan converter 144 and stored in the image memory 146. Processor 14
8 is an input data memory 142 and an image memory 146
Are subjected to predetermined data processing.

The display section 16 is connected to the image processing section 14. The display unit 16 is provided with an image signal from the image processing unit 14 and displays an image based on the image signal. The display unit 16 has a graphic display (graphi) capable of displaying a color image.
c display).

The transmitting / receiving unit 6, the B-mode processing unit 10,
A control unit 18 is connected to the image processing unit 14 and the display unit 16. The control unit 18 supplies a control signal to each of these units to control the operation. Various notification signals are input to the control unit 18 from each controlled unit.

Under the control of the control unit 18, the B mode operation is executed. An operation unit 20 is connected to the control unit 18. The operation unit 20 is operated by the operator, and the control unit 18
, An appropriate command or information is input. The operation unit 20 includes, for example, a keyboard (keyboard) and a pointing device (pointing device).
e) and an operation panel equipped with other operation tools (pan
el).

The ultrasonic imaging by the present apparatus will be described. The operator touches the ultrasonic probe 2 to a desired portion of the object 4 and operates the operation unit 20 to perform a B-mode imaging operation.
Thus, B-mode shooting is performed under the control of the control unit 18.

The transmitting / receiving unit 6 scans the inside of the object 4 in the order of sound rays through the ultrasonic probe 2 and receives the echoes one by one. Ultrasonic transmission / reception is performed twice for the same sound ray, and a difference between the two echo reception signals is obtained, thereby obtaining a harmonic echo reception signal.

The B-mode processing unit 10 performs logarithmic amplification of the echo reception signal input from the transmission / reception unit 6 by the logarithmic amplification unit 102, performs envelope detection by the envelope detection unit 104,
A scope signal is obtained, and B-mode image data for each sound ray is formed based on the scope signal.

The image processing unit 14 stores the B-mode image data for each sound ray input from the B-mode processing unit 10 in the input data memory 142. As a result, a sound ray data space for the B-mode image data is formed in the input data memory 142.

The processor 148 includes the input data memory 1
Each of the 42 B-mode image data is scan-converted by a digital scan converter 144 and converted into an image memory 146.
Write to. The B-mode image shows a tomographic image of the body tissue on the sound ray scanning plane by harmonic echo. This image is displayed on the display unit 16 and used for a desired purpose such as diagnosis.

[0065]

As described above in detail, according to the present invention, an ultrasonic transmission / reception method and apparatus for obtaining a wideband harmonics echo even with unipolar driving, and an ultrasonic wave provided with such an ultrasonic transmission / reception apparatus An imaging device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a transmission / reception unit in the device shown in FIG.

FIG. 3 is a conceptual diagram showing the relationship between sound pressure and harmonics.

FIG. 4 is a block diagram of a transmission / reception unit in the device shown in FIG.

FIG. 5 is a schematic diagram of sound ray scanning by the device shown in FIG.

FIG. 6 is a schematic diagram of sound ray scanning by the device shown in FIG.

FIG. 7 is a schematic diagram of sound ray scanning by the device shown in FIG.

8 is a block diagram of a B-mode processing unit in the device shown in FIG.

FIG. 9 is a block diagram of an image processing unit in the apparatus shown in FIG.

[Explanation of symbols]

 2 Ultrasonic probe 4 Target 6 Transmission / reception unit 10 B-mode processing unit 14 Image processing unit 16 Display unit 18 Control unit 20 Operation unit 602 Transmission timing unit 604 Transmission beamformer 606,614 Switching unit 608,608 'Driver 610 Transmission / reception switching Unit 612 Received beamformer 616, 616 'Memory 618 Subtraction unit 620 Gain adjustment unit

Claims (9)

[Claims] 1. An ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation is transmitted, and an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation is transmitted in the same direction as the transmission. Transmitting an ultrasonic echo of the two types of transmitted ultrasonic waves, respectively, and forming a signal of a difference between the received two echoes. 2. An ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation is transmitted, and an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation is transmitted in the same direction as the transmission. Transmitting, receiving each of the two types of transmitted ultrasonic echoes, adjusting a gain of the two received echoes according to a difference in transmitted sound pressure, and calculating a difference between the adjusted two echoes. A method for transmitting and receiving an ultrasonic wave, comprising: forming a signal. 3. The ultrasonic transmission / reception method according to claim 1, wherein the transmission directions of the two types of ultrasonic waves are sequentially changed. 4. A first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation,
Second ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation, and echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves, And a difference signal forming means for forming a signal of a difference between the two received echoes. 5. A first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause a waveform distortion accompanying propagation, and an ultrasonic wave having a sound pressure insufficient to cause a waveform distortion accompanying propagation. A second ultrasonic wave transmitting means for transmitting the two types of transmitted ultrasonic waves, and an echo receiving means for receiving echoes of the two types of transmitted ultrasonic waves, respectively, and a gain according to a difference in transmitted sound pressure between the two received echoes. An ultrasonic transmission / reception apparatus comprising: a gain adjusting unit that adjusts a difference between the two echoes; and a difference signal forming unit that forms a signal of a difference between the adjusted two echoes. 6. The ultrasonic transmitting / receiving apparatus according to claim 4, wherein said first and second driving means sequentially change the direction of said transmission. 7. A first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause a waveform distortion accompanying propagation, and an ultrasonic wave having a sound pressure insufficient to cause a waveform distortion accompanying propagation. Second ultrasonic wave transmitting means for transmitting the ultrasonic waves, echo receiving means for respectively receiving echoes of the two types of transmitted ultrasonic waves, and difference signal formation for forming a signal representing a difference between the two received echoes. And an image generating means for generating an image based on the signal of the formed difference. 8. A first ultrasonic wave transmitting means for transmitting an ultrasonic wave having a sound pressure sufficient to cause waveform distortion accompanying propagation, and an ultrasonic wave having a sound pressure insufficient to cause waveform distortion accompanying propagation. A second ultrasonic wave transmitting means for transmitting the ultrasonic waves, an echo receiving means for respectively receiving the echoes of the two types of transmitted ultrasonic waves, and a gain for the two received echoes according to a difference in transmitted sound pressure. Gain adjusting means for adjusting the difference, a difference signal forming means for forming a signal of a difference between the adjusted two echoes, and an image generating means for generating an image based on the formed difference signal. An ultrasonic imaging apparatus characterized by the above-mentioned. 9. The ultrasonic imaging apparatus according to claim 7, wherein the first and second driving units sequentially change the direction of the transmission.