JPH04276247A - Ultrasonic diagnostic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an ultrasonic diagnostic device, and in particular, the present invention relates to an ultrasonic diagnostic device, and in particular, receives reflected echoes of ultrasonic waves transmitted toward a subject such as a living body, performs signal processing, and processes ultrasonic waves based on the signal processing. The present invention relates to an ultrasonic diagnostic device that displays images.

0002

[Prior art and its problems] In this type of device,
The ultrasonic beam is controlled to focus at a specified depth position, and the ultrasonic pulse is transmitted from the transducer, and the reflected echo due to the difference in acoustic impedance at the biological tissue interface is generated.
The received signal is processed with the scattered echoes from the internal uniform tissue,
The ultrasonic image (B-mode image) is displayed by performing brightness modulation according to the signal intensity.

Recently, a variable aperture dynamic focusing technique has been used in which the focus position is dynamically changed for a transmitted beam in one direction, and the aperture is changed by appropriately selecting a set of transducers during wave reception. It is being With these, clear images with high resolution can be obtained from shallow to deep areas of the diagnostic region.

[0004] When performing variable aperture or dynamic focusing as described above, it is necessary to correctly phase synthesize the received reflected echoes. However, the oscillator-multiplexer
The phase synthesis of signals may not be performed correctly due to internal noise and external induced noise generated in a series of received signal conversion circuits such as a preamplifier and a phase controller. If phase synthesis is not performed correctly in this way, clutter (irregular signals) and grains (particular signals) will appear in the signal due to the synergistic effect with the speckles (dots caused by phase interference) of the ultrasonic echoes.
occurs and is displayed on the image.

[0005] Such a phenomenon may give an incorrect judgment in image diagnosis. In particular, when the liver region has a uniform tissue and the S/N ratio is low, the above-mentioned clutter and grains are noticeable on the image and cause image quality deterioration.

[0006] In order to make this phenomenon less noticeable, the signal pass band of the receiving dynamic filter is selected to be high to suppress clutter with many low frequency components and large grain signal components. However, with this method, signal components containing more low frequency components from deep within the body are lost, and low frequency components of the transducer transmitted energy are also lost at the same time. This leads to a decrease in the received ultrasound signal level over the entire diagnosis area, and
/N becomes a bad image, resulting in deterioration of image quality. Further, in order to improve the deterioration of the S/N ratio, it has been considered to improve the sensitivity of the vibrator, but there are limitations in terms of materials and structure. Furthermore, although it is possible to increase the vibrator drive energy to some extent, these methods also have limitations because they should be kept as low as possible in terms of safety for the human body. Therefore, it is desired to improve image quality by other means.

An object of the present invention is to provide an ultrasonic diagnostic apparatus that can improve image quality by suppressing clutter and grain signal components of defective phase synthesis signal components caused by noise without reducing received wave energy. be.

[0008]

[Means for Solving the Problems] The ultrasonic diagnostic apparatus according to the present invention is an apparatus that transmits ultrasonic waves to a subject, receives ultrasonic echoes from the subject, and displays an ultrasonic image. , an image quality deterioration signal detection means, a suppression signal generation means, and a suppression signal injection means.

The image quality deterioration signal detection means is means for detecting an image quality deterioration signal in a predetermined frequency band included in the received echo signal. The suppression signal generating means is a means for generating a suppression signal having a higher frequency than the image quality deterioration signal. The suppression signal injection means is a means for injecting the suppression signal generated by the suppression signal generation means into the received echo signal during the period in which the image quality degradation signal is included, based on the detection result of the image quality degradation signal detection means.

0010

In the ultrasonic diagnostic apparatus of the present invention, image quality deterioration signals in a predetermined frequency band such as clutter and grain contained in the received echo signal are detected by the image quality deterioration signal detecting means. On the other hand, with respect to the image quality signal, a suppression signal having a higher frequency than the image quality signal is generated by the suppression signal generating means. The suppression signal injection means injects a suppression signal into the received echo signal for a period in which it is determined that the received echo signal includes the image quality deterioration signal.

[0011] As a result, image quality deterioration signals such as clutter and grain become high frequency, and when displayed on a screen,
It becomes less noticeable. Therefore, it is possible to selectively suppress only the image quality degradation signal without reducing the level of the received echo signal, and it is possible to obtain clear images over a wide range from shallow to deep areas, while suppressing clutter and grain. It is possible to improve the image quality.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In the figure, a probe 1 consists of a plurality of micro-oscillators and is connected to a multiplexer 2. The multiplexer 2 is for selecting a vibrator for performing electronic scanning, variable aperture, etc. This multiplexer 2 includes a wave transmitting section 30 and a wave receiving section 31.
is connected. The wave transmitting section 30 includes a wave transmitting pulser 3, a wave transmitting phase generating circuit 4, and a phase synthesis controller 5.

The wave receiving section 31 includes a preamplifier 6 that amplifies the reflected echo signal, and a phase synthesis circuit 7 that performs phasing and addition of the reflected echo signals from each vibrator. Furthermore, a logarithmic amplification and detection circuit 8 is connected to the phase synthesis circuit 7 for performing logarithmic amplification and detection processing in order to obtain tomographic data. After the logarithmic amplification detection circuit 8, an A/D conversion circuit 9, a signal level injection circuit 22, and an image memory 10 are installed in order.
, a D/A conversion circuit 11, and a CRT as an image display device.
A monitor 12 is connected. A sampling clock generation circuit 18 that generates a sampling clock for A/D conversion is connected to the A/D conversion circuit 9.

The wave receiving section 31 is provided with an image quality improving section 26 for suppressing clutter and grain frequency components. The image quality improvement section 26 is comprised of a section that extracts the frequency to be suppressed, a section that determines the signal level, and an addition section.

[0015] The suppression frequency extraction section includes a frequency extraction circuit 13
, a frequency comparison circuit 14 , a frequency selection circuit 15 , a frequency division circuit 19 , and a frequency selection circuit 20 . The frequency extraction circuit 13 is a circuit that performs AC coupling on the output of the logarithmic amplification detection circuit 8, and further performs frequency-voltage (F-V) conversion processing to digitize this value. The frequency selection circuit 15 is externally set with the clutter and grain frequency bands to be suppressed. The frequency comparison circuit 14 compares the output of the frequency extraction circuit 13 with the frequency selection circuit 1.
This is a circuit for comparing the output of 5. Frequency dividing circuit 19
and the selection circuit 20 includes the sampling clock generation circuit 1
This circuit divides the clock signal from 8 and generates a suppression signal with a frequency corresponding to the clutter and grain frequency components. This frequency dividing circuit 19 and frequency selection circuit 2
0 is constituted by a PLL circuit or the like.

The signal level determination section includes a signal strength selection circuit 1
6, signal strength comparison circuit 17, and signal level selection circuit 2
1. A signal level to be compared is set to the signal strength selection circuit 16 from the outside. The signal strength comparison circuit 17 is a circuit for comparing the output of the A/D conversion circuit 9 and the signal level set in the signal strength selection circuit 16. The output of the signal strength comparison circuit 17 is given to the signal level selection circuit 21, and the signal level selection circuit 21
This circuit sets the level of the suppression signal to an optimum value using this output signal, and performs doubling weighting processing on the output signal of the frequency selection circuit 20 and digitizes it.

Further, the signal injection circuit 22 as an adding section is a circuit that digitally adds the digitized received echo signal and the suppression signal that is the output of the signal level selection circuit 21.

Each of the above components is controlled by a main controller 27. Main controller 2
Reference numeral 7 comprises a CPU 24, a data/control ROM 23 that stores data, etc. for controlling each part using control signals from the CPU 24, and a keyboard 25 for giving instructions to the CPU 24.

Next, the operation will be explained. When the device is started, the phase synthesis controller 5 controls the transmission phase generation circuit 4, and the output signal drives the transmission pulser 3. Pulses from the transmitting pulser 3 are applied to the vibrator of the probe 1 via the multiplexer 2. As a result, an ultrasonic beam is transmitted to the subject. At this time, electronic scanning of the ultrasonic beam is performed by switching control of the multiplexer 2.

On the other hand, the reflected echo from the subject is input to the preamplifier 6 via the probe 1 and the multiplexer 2, where it is amplified and input to the phase synthesis circuit 7. The phase synthesis circuit 7 performs electronic focusing processing by phasing and adding the obtained reflected echoes. At this time, variable aperture dynamic focusing is performed by dynamically switching the multiplexer 2 and preamplifier 6. The output of the phase synthesis circuit 7 is detected by the logarithmic amplification detection circuit 8, and the envelope waveform of the reflected echo signal is obtained from this output. This signal is A/D
It is digitized by the conversion circuit 9 and stored in the image memory 10 via the signal injection circuit 22. The tomographic data stored in the image memory 10 is sequentially read out in synchronization with the television signal, converted into a video signal by the D/A conversion circuit 11, and displayed on the CRT monitor 12 as an ultrasonic tomographic image.

In the wave reception processing, the signal injection circuit 22
Then, the suppression signal created by the image quality improvement unit 26 is selectively injected into the received echo signal. The operation of the image quality improvement section 26 will be explained below.

The output of the logarithmic amplification detection circuit 8 is given to an A/D conversion circuit 9 and also to a frequency extraction circuit 13. This frequency extraction circuit 13 performs AC coupling on the envelope waveform signal (hereinafter referred to as received echo signal) which is the output of the logarithmic amplification detection circuit 8, and
Convert and digitize this value. Normally 100kHz
A received echo signal of approximately 3 MHz to 3 MHz is obtained. On the other hand, the frequency band of clutter and grain that causes image quality deterioration can be predicted in advance depending on the probe used, so this frequency band (for example, 500 kHz to 70 kHz)
0kHz) or the probe to be used is specified from the keyboard 25, this frequency band is set in the frequency selection circuit 15. The frequency comparison circuit 14 compares the digital signal of the received echo signal, which is the output of the frequency extraction circuit 13, with the frequency set in the frequency selection circuit 15. Then, when the frequency of the received echo signal is within the frequency band set in the frequency selection circuit 15, a signal to that effect is output to the frequency division circuit 19 and the frequency selection circuit 20.

The frequency dividing circuit 19 divides the clock signal of the sampling clock generating circuit 18 to generate a signal of a predetermined frequency, and the frequency selecting circuit 20 divides the frequency of the clock signal of the sampling clock generating circuit 18 to generate a signal of a predetermined frequency. Select the output of circuit 19. In the example above, a signal of 500kHz to 700kHz is extracted, so here we use a 7MHz signal as a suppression signal.
Select the signal of the degree. As a result, a suppression signal having a frequency corresponding to the clutter and grain frequency components is obtained as the output of the frequency selection circuit 20. Note that if the probe or the like to be used is changed, the frequency bands of clutter and grain also change, so in this case, the frequency setting of the frequency selection circuit 15 is changed. Further, the set frequency of the frequency selection circuit 15 can be changed by the operator while observing the image displayed on the CRT monitor 12.

On the other hand, the digital signal from the A/D conversion circuit 9 is input to a signal strength comparison circuit 17. The signal strength comparison circuit 17 also receives a signal from the signal strength selection circuit 16 . In the signal strength selection circuit 16, the signal strength input from the keyboard 25 is set. The signal strength can also be set by the operator while observing the image displayed on the CRT monitor 12. The signal strength comparison circuit 17 compares the strength of the received echo signal with the signal strength set in the signal strength selection circuit 16, and determines that the received echo signal is higher than the signal strength set in the signal strength selection circuit 16. If it is larger, a signal to that effect is output to the signal level selection circuit 21. As a result, the suppression signal is set at the optimum signal level for suppression by the signal level selection circuit 21 and is provided to the signal injection circuit 22 .

In this way, when the suppression signal which is the output of the signal level selection circuit 21 is added to the clutter and grain frequency component signals of the received echo signal, the frequencies of these parts become high, and the CRT When the image is displayed on the monitor 12, it becomes inconspicuous, and the image is clearly different from, for example, a tumor (frequency is about 100 kHz). This makes it possible to avoid misdiagnosis. Furthermore, since the dynamic filter can be set to a frequency range that minimizes the loss of received wave energy, images can be displayed clearly from shallow to deep areas.

[Other Embodiments] (a) In the above embodiments, the clutter and grain frequency components are suppressed by digital processing, but analog processing may also be used. FIG. 2 shows a circuit configuration for this purpose.

In the figure, the received echo signal, which is the output of the logarithmic amplification and detection circuit 8, is input as an analog value to an image quality improvement section 26 similar to that shown in FIG. On the other hand, the output of the sampling clock generation circuit 18 is input to the frequency dividing circuit 19 in the same manner as described above. In the image quality improvement unit 26, processing similar to that described above is performed in an analog manner, and the analog suppression signal S
The signal is applied to the adder circuit 32 as a signal. In the adder circuit 32,
The suppression signal and the output of the logarithmic amplification detection circuit 8 are added in analog form and output to the A/D conversion circuit 9. The subsequent processing is the same as described above.

(b) In the present invention, the sampling clock may be directly injected into the clutter and grain frequency portions by the signal level injection circuit 22. If you do this,
The frequency divider circuit 19 and frequency selection circuit 20 are no longer necessary.

[0029]

As described above, in the present invention, since a suppression signal is injected into the clutter and grain frequency component signals included in the received echo signal, the clutter and grain frequency component signals are suppressed without reducing the received wave energy. can be selectively suppressed and reduced, improving image quality and reducing misdiagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

FIG. 2 is a partial block configuration diagram of an ultrasonic diagnostic apparatus according to another embodiment of the present invention.

[Explanation of symbols]

13 Frequency extraction circuit 14 Frequency comparison circuit 15 Frequency selection circuit 16 Signal strength selection circuit 17 Signal strength comparison circuit 19 Frequency divider circuit 20 Frequency selection circuit 21 Signal level selection circuit 22 Signal injection circuit 26 Image quality improvement department

Claims (1)

[Claims] Claim 1: An ultrasound diagnostic apparatus that transmits ultrasound waves to a subject, receives ultrasound echoes from the subject, and displays ultrasound images; an image quality deterioration signal detection means for detecting an image quality deterioration signal;
A suppression signal generating means for generating a suppression signal having a higher frequency than the image quality deterioration signal, and a suppression signal generating means for generating a received echo signal in a period in which the image quality deterioration signal is included based on the detection result of the image quality deterioration signal detection means. and a suppression signal injection means for injecting the suppression signal generated by the ultrasound diagnostic apparatus.