JPH0331457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ultrasonic diagnostic apparatus that transmits and receives ultrasonic pulses using a transducer array, receives reflected waves, and displays images.

(Prior art) Ultrasonic diagnostic equipment irradiates ultrasonic pulse signals into the subject, and detects reflected waves by utilizing the characteristics of ultrasonic waves for the subject, that is, the degree of attenuation and reflection that differs depending on the tissue and its lesion. This device performs diagnosis by displaying tomographic images formed by the CRT on an image display device such as a cathode ray tube display (hereinafter referred to as CRT). FIG. 3 shows a schematic configuration of a conventional ultrasonic diagnostic apparatus. In the figure, a high frequency signal generated by a high frequency oscillator 1 is pulse-modulated by a transmission signal generator 2, and
It is input to the transmitting beamformer 3. The transmission beam former 3 applies a phase delay to the input high frequency signal according to a predetermined program, and separates the input high frequency signal into signals of, for example, 64 channels so as to form an ultrasonic beam. The signals of the 64 channels are power amplified by a transmitting/receiving circuit 4 including a transmitting amplifier, a transmitting/receiving switch, a receiving amplifier, etc., and then input to the transducer array 5. The transducer array 5 converts the input high frequency pulse signal into an ultrasonic signal and transmits the ultrasonic signal. The ultrasonic signal reflected from the reflector within the subject is received again by the transducer array 5 and converted into a high frequency electrical signal, which is input to the receiving beamformer 6 via the transmitting/receiving circuit 4. The input signals of the 64 channels are each subjected to a phase delay in the receiving beamformer 6, and are then outputted after being phased and summed. The logarithmic amplifier 7 is an amplifier that compresses the wide dynamic range of the received signal and logarithmically compresses it into a range suitable for image display. The signal compressed and amplified by the logarithmic amplifier 7 is envelope-detected by the detector 8, and is converted into a digital scan converter (hereinafter referred to as DSC).
At step 9, the signal is converted into a television format signal and displayed on CRT 10.

(Problems to be Solved by the Invention) In the above-mentioned ultrasonic diagnostic apparatus, noise called speckle noise appears like a textile or satin material in an image generated by reflected waves from a reflector inside the subject. Unable to obtain images of good quality. This noise is caused by phase interference of reflected waves from a scattering object smaller than the wavelength of the ultrasonic wave.

FIG. 4 is a diagram showing a scan method called compound scan. Figure A is a diagram in which a single probe 11 is applied to a subject 12 for observation.Moving this single probe 11 to the 11' position changes the angle with respect to the scatterer, which is effective for speckle reduction. . b is sector scan 13,
13 is a diagram showing a state in which a compound scan is performed by shifting to the position 13'. FIG. This overwriting method called compound scan is very effective for speckle reduction, but it has problems such as being difficult to operate and not being able to keep up with fast movements.
A compound scan cannot be performed solely for speckle reduction.

The present invention was made in view of the above-mentioned problems, and its purpose is to increase the signal-to-noise ratio by integrating and averaging echoes from a fixed target, and at the same time to reduce speckles such as textile fabric caused by interference of scattered waves. An object of the present invention is to realize an ultrasonic diagnostic device with improved image quality by smoothing images containing noise.

(Means for Solving the Problems) The present invention solves the above problems in an ultrasonic diagnostic apparatus that transmits and receives ultrasonic pulses using a transducer array, receives reflected waves, and displays images. means for transmitting at least one ultrasonic beam; a plurality of received signal synthesis means for simultaneously synthesizing a plurality of received signals having acoustic path differences smaller than the resolution of the ultrasonic beam; and the received signal synthesis means The invention is characterized in that it comprises arithmetic means for adding and averaging the output signals of.

(Operation) An ultrasonic signal is transmitted, a plurality of received sound rays having a path difference smaller than the beam resolution are synthesized by phasing and addition, and each signal is averaged and displayed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In the figure, parts equivalent to those in FIG. 3 are given the same reference numerals. In the figure, 6A, 6B, and 6C are a receiving beamformer A, a receiving beamformer B, and a receiving beamformer C, which respectively phase and add three receiving beams to be described later and synthesize them. 7
A, 7B, and 7C are logarithmic amplifiers A, logarithmic amplifier B, and logarithmic amplifier C that logarithmically compress and amplify the output signals of the respective receiving beamformers 6A, 6B, and 6C, and the respective output signals are sent to the coefficient multiplier A21.
A is multiplied by a coefficient for weighting in the coefficient unit B 21B and the coefficient unit C 21C, and then added to the adder 22.
The signals are added at the attenuator 23 and output with appropriate amplitude.

Next, the operation of the apparatus of the embodiment configured as described above will be explained. The high-frequency signal generated by the high-frequency oscillator 1 is pulse-modulated by the transmitting signal generator 2, subjected to delay processing in the transmitting beam former 3, and transmitted from the transducer array 5 via the transmitting/receiving circuit 4 as shown in FIG. This is the same as described for the conventional device. The transducer array 5 generates an ultrasonic beam (hereinafter referred to as an acoustic ray) in the same direction as the transmission beam, and two acoustic rays having an acoustic path difference slightly smaller than the beam resolution that can identify the minimum pin target. The signal is received and input to the receiving beamformer A6A, receiving beamformer B6B, and receiving beamformer C6C via the transmitting/receiving circuit 4. The sound rays received by the transducer array 5 are shown in FIG. In Fig. 1, the same parts as in Fig. 1 are given the same reference numerals.

Reference numeral 15 is a pin target for viewing the resolution of the sound ray, and reference numeral 16 is a minute scatterer finer than the wavelength of the ultrasonic waves in the parenchyma of, for example, the cells of an organ. Also, sound ray 1, sound ray 2, and sound ray 3 are three sound rays having a path difference within the size of the pin target 15. In the figure, an arrow is drawn in the transmission direction for convenience of explanation, but
As shown in FIG. 1, each sound ray 1, 2, 3 is a receiving beam.

In the above receiving beamformer A6A, acoustic ray 1,
The signals of the sound ray 2 are phased and added in the receiving beamformer B6B, and the signals of the sound ray 3 are added in the receiving beamformer C6C. (Actually, the sound rays 1, 2, and 3 are phased and added.
signal is generated. ) The signals of sound rays 1, 2, and 3 are respectively transmitted through logarithmic amplifier A17A, logarithmic amplifier B7B,
Logarithmically compressed and amplified in logarithmic amplifier C7C, coefficient unit A21A, coefficient unit B21B, coefficient unit C21C
The signals are weighted and added in an adder 22, and attenuated in an attenuator 23 to obtain an output signal equivalent to the average value. This signal is envelope-detected by a rectifier 8, passes through a DSC 9, and is displayed as an image on a CRT 10.

Figure 2 (b) shows a comparison of the signals a, b, c obtained by signal processing of the sound rays 1, 2, and 3 and weighted by the coefficient units 21A, 21B, and 21C, and the added signal d. This is a diagram. In the figure,
a is a signal waveform in which the signal of sound ray 1 is weighted in coefficient unit A21A, b is a signal waveform in which the signal of sound ray 2 is weighted in coefficient unit B21B, and c is a signal waveform in which the signal of sound ray 3 is weighted in coefficient unit C21C. The signal waveform d is an output waveform obtained by adding the above signals a, b, and c in an adder 22 and averaging the resulting signal in an attenuator 23. Reference numerals 17a, 17b, and 17c are signals reflected by the pin target 15 in FIG. 1, and 18 is a signal reflected by the minute scatterer 16 in FIG. As shown in FIG. 2B, when the reflected signals from sound rays such as sound rays 1, 2, and 3 that are slightly shifted within the resolution of the pin target 15 are averaged, the pin target 15 has a size equivalent to the beam width. Even if there is a slight change within the beam width, there is a sufficiently large correlation in the amplitude and phase, so a signal with almost no change can be obtained. This results in a variety of spec patterns, and even a slight deviation in the stroke can result in large changes.

Since the addition by the adder 22 is the addition of logarithmic amplifier outputs, the received signal is multiplied by the signals of each sound ray, which is equivalent to taking the correlation in the high-frequency signals of three sound rays, and the correlation is The received signal due to the very small scatterer 16 is almost eliminated by logarithmically amplifying and adding the signals. In the end, the signals from the pin targets 15 are increased by addition, and mutually unrelated signals such as speckle noise and white noise are suppressed, so that the S/N ratio increases.

As described above, according to this embodiment, by adding together the phases of 2 to 3 sound rays with a strong correlation and whose paths are slightly deviated, a target that is large in beam resolution, such as a fixed pin target, stands out. Speckle noise is suppressed, and uncorrelated noise such as electrical noise is suppressed by the 1/2 power of the number of additions, so the SN ratio is improved and images with good quality can be obtained. Ta.

Note that the present invention is not limited to the above embodiments. In the embodiment, for convenience of explanation, the receiving beam of three sound rays (FIG. 2 A) is shown with the direction of the sound rays reversed from the one sound ray of the transmitted wave, but in reality, the direction of the sound rays is reversed. Although the example of the receiving beam shown in FIG. Figure A shows a case in which received signals of three parallel sound lines are processed as described above, instead of being converged on the transducer array 5 as shown in Figure 2. beam width 3
0a is slightly wider. The figure below shows pin target 15.
This shows a case in which a received signal of three tone lines converging to , is processed as described above. The beam width 30b is widened. Figure C shows a case where the above processing is performed using a received signal based on two sound rays transmitted in parallel. 31 is the center of the received sound ray in the direction of the transmitted beam, and 32 is the sound ray obtained by combining the two received sound rays 31. Figures D and E are given the same reference numerals as Figure C. This is 2 waves transmitted with a small angle difference.
one of the transducer arrays 5.
The data of a sound ray 32 is obtained by transmitting a wave from a point and synthesizing a receiving beam 31 of the same sound ray. The diagram E shows a transmitting sound ray converged on a target.

Furthermore, it is obvious that the number of sound rays to be synthesized can be any number as long as it is two or more, and the elements to be included in each receiving beamformer do not need to be strictly the same.

Further, averaging is more effective after logarithmic compression, but when cost and phase control are difficult, a certain degree of effect can be obtained by averaging using signals before logarithmic compression.

(Effects of the Invention) As explained in detail above, according to the present invention,
The received signal from the fixed target increases, uncorrelated noise is suppressed, improving the SN ratio, and speckle noise is also eliminated, improving image quality, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of signal processing by the device of the present invention;
FIG. 3 is a schematic diagram of a conventional ultrasonic diagnostic apparatus, FIG. 4 is an explanatory diagram of a compound scan, and FIG. 5 is a diagram of another embodiment in which the sound rays are changed. 3... Transmission beam former, 5... Transducer array, 6, 6A, 6B, 6C... Receiving beam former, 7, 7A, 7B, 7C... Logarithmic amplifier, 8... Rectifier, 9... DSC, 10...
CRT, 15...Pin target, 16...Micro scatterer, 17a, 17b, 17c, 17d...Reflection signal of pin target, 18a, 18b, 18
c, 18d... Reflection signal of minute scatterer, 21A,
21B, 21C... Coefficient unit, 22... Adder, 2
3...Attenuator.

Claims (1)

[Claims] 1 In an ultrasonic diagnostic device that transmits and receives ultrasonic pulses using a transducer array, receives reflected waves, and displays images, there is a means for transmitting at least one ultrasonic beam, and a resolution of the ultrasonic beam. Ultrasonic waves characterized by comprising a plurality of received signal synthesis means for simultaneously synthesizing a plurality of received signals having small acoustic path differences, and an arithmetic means for adding and averaging the output signals of the received signal synthesis means. Diagnostic equipment.