JPH0751270A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To provide a means to extract and draw the data following the transmitting attenuation in an organism by providing an image forming method reflecting the form of the frequency spectrum of an ultrasonic reflected signal from the organism. CONSTITUTION:A received signal is divided into different bands by plural band filter groups (20a to 20c), and strength signals detected by wave detectors (22a to 22c) are weighting added or hue added, so as to display in an image. As a result, the received signal is not handled in all the band, but compression detected at each divided band, and then weighting added, and thereby, the attenuation data following the ultrasonic wave transmission in the linving body of a patient is added to a conventional tomographic image, and the visibility of a minute difference of contrast can be improved broadly. Consequently, not only the diseased part and the healthy composition around the diseased part can be recognized easily, but also species generated by the interference between waves can be reduced effectively, and the contrast resolution can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to signal processing in an ultrasonic diagnostic apparatus, and more particularly to a technique for visualizing a biometric feature amount by attenuating a received signal in a living body by subjecting a received signal to frequency band division processing. .

[0002]

2. Description of the Related Art Diagnostic information obtained from an ultrasonic diagnostic apparatus mainly consists of anatomical information obtained from a tomographic image and blood flow information obtained from a Doppler image. Also, for the purpose of obtaining new diagnostic information, extraction of minute contrast differences,
Development of technology for extracting and drawing physical quantities such as attenuation in the living body is being promoted. The latter is called Tissue Characterization in this field, and can be used to extract individual differences between patients and use it as diagnostic information, or to feed back to the device to change device parameters. Development is in progress for the purpose of using it. However, these research results have not yet been incorporated into commercial ultrasonic devices. The main reason for this is that the scale of hardware and software is large and it is difficult to realize the cost.

Conventionally, as a technique considering the attenuation of ultrasonic waves in the living body, a TGC (Time Gain Control) circuit and a dynamic filter (Dynamic Filter) circuit are known. The former is by gradually increasing the amplification factor of the receiving system according to the depth of generation of the echo signal, and the latter is by gradually reducing the center frequency of the band filter of the receiving system according to the depth of generation of the echo signal. Also compensates for the amount of attenuation in the body and absorbs individual differences between patients.

FIG. 6 is a diagram showing a configuration of a main part of a typical ultrasonic diagnostic apparatus, which is for explaining a dynamic filter in the prior art. That is, in this device, the array type probe 10 is driven by the wave transmission circuit 11, the ultrasonic wave is radiated into the living body, and the reflected ultrasonic wave signal from the living body is received by the preamplifier group 13 and then received. Electrons are focused by the phasing unit 14, and further processed by an analog signal processing circuit including a dynamic filter circuit 15, a logarithmic compression circuit 16 and a TGC circuit 17. TGC circuit 1
The output of 7 is passed through a detector 18 and a contour enhancement circuit 19 to A
After inputting to the / D converter (not shown) and sampling, it is sent to the image control circuit 50 and displayed on the display 60 according to a predetermined format. The series of signal processes are synchronously managed by the control unit 12.

[0005]

In the conventional device described above, the intensity information of the ultrasonic reflection signal is the above-mentioned TGC.
Although it is subjected to dynamic filter processing, it can be said that it is basically displayed and analyzed as it is. Therefore, in order to visualize the individual difference depending on the patient, a subtle difference in the intensity signal is displayed by the brightness difference on the screen by using a means such as increasing the compression ratio of the compression circuit. However, the smaller the difference in brightness, the more difficult it becomes to visually recognize it, and it is considered that the difference in brightness is small in the early stage of the disease. Therefore, for early diagnosis and detection of diseases, it is desirable to draw a small difference in intensity signal, in other words, the amount of information that changes in luminance difference.

First, the problems of the conventional dynamic filter processing will be described. The dynamic filter is composed of a bandpass filter having a variable center frequency, and as shown in FIG. 7, the center frequency (m in the figure) and the bandwidth (m +, m− in the figure) are changed according to the depth direction. It is changing. Usually, this rate of change is set on the basis of a standard attenuation characteristic for each organ, and copes with the gradual decrease of the center frequency due to the in-vivo attenuation of the received signal. However, since this rate of change changes into various curves depending on the target site, individual differences, contact state between the probe and the living body surface, etc., it often does not match the set curve,
There was a problem that the information to be drawn was not displayed due to the lack of the received signal.

An object of the present invention is, firstly, to provide a band selection processing method which replaces the conventional dynamic filter. Secondly, it is an object of the present invention to provide means for imaging a minute change depending on the attenuation amount of a received signal with a relatively simple structure.

[0008]

According to the present invention, in order to achieve the above object, a received ultrasonic signal is distributed to a plurality of band-pass filters having different center frequencies.
Each filter output is individually subjected to intensity conversion processing such as logarithmic compression and detection, each processing output is weighted and added, and the addition result is displayed as luminance information.

Further, in another configuration of the present invention, a color code is added to each processing output and the weighted addition result is displayed in color (when adding each processing output, a hue is assigned to each output, Hereinafter, the method in which the addition is addition in hue is abbreviated as hue addition).

[0010]

When the intensity output is obtained for each frequency band and added to obtain the luminance information, the result is completely different from that when the intensity output is obtained as it is in a single band and is used as the intensity signal.
This is because, in the addition of a plurality of signals, the method of interference between the waves due to the phase difference is different between the detection after the addition and the detection after the individual detection. This difference has two main effects.

First, the interference between waves causes a phenomenon called so-called speckle in an image of a diagnostic device, which is an obstacle in obtaining a high-resolution image and a high-contrast image. If the frequency band is divided and the detection processing is performed individually, the generation of speckles can be significantly reduced. This is because each of the divided frequency bands has a narrower band than the original band, and thus phase interference between waves is less likely to occur.

Secondly, the attenuation that an ultrasonic signal undergoes when it propagates in a living body changes the center frequency and spectrum shape of the received signal, and the state of the change can be used as diagnostic information. This is because the attenuation varies depending on the depth direction in the living body and also varies depending on individual differences between patients.

In the present invention, by changing the weights in the weighted addition, it is possible to display an image in which high-frequency information is emphasized or to display an image in which low-frequency information is emphasized. The above individual differences and differences due to diseases can be visualized. In addition, by adding hues, it is possible to easily display the same difference as color information. For example, if the color code is blue for the low frequency component and red for the high frequency component, the frequency distribution in the screen becomes obvious.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

FIG. 1 shows a first embodiment of the present invention. Explaining the part different from FIG. 6, the output of the phasing unit 14 is the band-pass filters 20a, 20 having different center frequencies.
b, 20c, logarithmic compression circuits 21a, 21b, 2
1c is supplied. The output of each logarithmic compression circuit is selected into a signal within each frequency band by each of the band filters 20a, 20b, 20c described above.
The variable input resistance 2 is converted to an intensity signal by b and 22c.
3a, 23b, 23c and an amplifier 24 having a variable feedback resistor 25 perform weighted addition.

The added signal is digitized by the A / D converter 26, converted into a predetermined format by the image controller 50, and displayed on the display 60.
When a 3.5 MHz ultrasonic probe is used, its frequency components range from 2 MHz to 4.5 MHz depending on the depth direction. In the present embodiment, the bandpass filters share a predetermined range. As an example, when a 3.5 MHz ultrasonic probe is used and three band filters are used as described above, 2 MHz to 2.
75 MHz is shared by 20a, 2.75 MHz to 3.5
MHz is shared by 20b, and 3.5 MHz to 4.25 MHz is shared by 20c (see FIG. 2). According to the experiment, in the liver and the like, it is convenient that the ranges of the band-pass filters partially overlap each other. Here, in the present embodiment, since the weighting is determined by the size of the variable input resistors 23a, 23b, 23c, the input resistor zero, that is, non-selection is also included in the weighting. It is also possible to select and draw a single processing output from the processing circuit output. Further, by changing the size of the feedback variable resistor in correspondence with the depth direction, it is possible to add the TGC function, which is the conventional device. In this embodiment, although not shown, it goes without saying that a dynamic filter circuit including a bandpass filter that covers the entire band of the received signal may be arranged in parallel with the filter processing group of this embodiment. Further, the selection of the frequency band does not need to be continuously selected as shown in FIG. 2, and for example, one of them may have the center frequency of the other 2nd and 3rd harmonics.
In this case, a so-called non-linear phenomenon can be detected.

FIG. 3 shows a second embodiment of the present invention. The part different from FIG. 6 will now be described.
The output of 4 is a bandpass filter 20a having a different center frequency,
Logarithmic compression circuits 21a, 21b, 20b, 20c,
21c. The output of each logarithmic compression circuit is converted into an intensity signal by the detectors 22a, 22b, 22c.
The respective intensity signals are weighted by the variable amplifiers 27a, 27b and 27c, and then the A / D converters 30a, 30b and 3 are weighted.
It is digitized by 0c. The respective output signals are respectively supplied to the hue applying circuit 31 by R (Red) and G (Gre
En) and B (Blue) are representative of the hues, and the hues are added so that the intensities thereof are lightened, and then supplied to the image controller 50 and displayed on the color display 60a. In such a case, the change in the frequency spectrum due to attenuation is
The image is displayed according to the hue and the brightness in the depth direction. Here, the hue is determined by the output of which band-pass filter, and therefore by the frequency band of the signal, and the lightness represents the intensity of each signal output and thus the power of the signal obtained by integration within each frequency band. It will be. For example, at a shallow depth, a reddish hue is given to indicate that high-frequency components are dominant, and at a depth, a blueish hue is assigned to indicate that low-frequency components are dominant. . Further, in a normal tomographic image, it is possible to easily discriminate between a diseased part and a surrounding tissue that exhibit only a minute contrast difference by the hue imaging by frequency division of the present invention. This is because the shape of the frequency spectrum is often different even if the structure and the reflection intensity are different.

In the above embodiment, the analog processing has been explained in consideration, including the use of bandpass filters having different center frequencies as a method of dividing the frequency band. Even if the above-described processing such as frequency analysis is replaced with a known DSP (Digital Signal Processor) by a D-converted signal and stored in a memory and a known DSP (Digital Signal Processor), the gist of the present invention is not essentially changed. In addition, as an example of the experiment using the ultrasonic probe of 3.5 MHz, the bandpass filter has the following bands and hues in parentheses (see Fig. 2). was gotten. That is, 20a (2M
Hz to 2.75MHz: Red), 20b (2.75MHz)
To 3.5 MHz: Green) and 20c (3.5 MHz to 4.25 MHz: Blue), suitable hues were obtained.

In the above embodiment, three bandpass filters are shown for the sake of explanation, but it goes without saying that the number of filters and the method of arranging hues are not limited to this. In addition, in the present embodiment, although individual detection is performed and weighted addition is performed, after weighting is performed before detection,
May be detected. However, in this case, it is necessary to consider the time delay of each bandpass filter, logarithmic compressor, and weighting circuit.

FIG. 4 is a diagram showing another embodiment of the present invention, and shows a main part relating to the following description.
That is, an output signal representative of the number of each frequency band (for example,
The amplifier output 21a) is fed to a comparator 22 as shown in FIG.
1a is compared with a predetermined set value 222a, the comparison output is integrated by a capacitor 223a for a predetermined time, and the integrated value is fed back to the multiplier 220a. Such a configuration is equivalent to the AGC for the frequency division processing output.
(Automatic Gain Control) will be set. That is, in a filter system having a small number of components, the weight of the weighting circuit is increased, and when the number of components is too large, the weight of a certain weighting circuit is individually reduced. Note that the detector in this embodiment may be arranged after the multiplier, but it should be noted that it is preferable to arrange before the multiplication from the viewpoint of the stability of the feedback system.

FIG. 5 is a diagram showing another embodiment of the present invention. In the above embodiment, of the information handled by the ultrasonic diagnostic apparatus, only information relating to amplitude information is handled, but the present invention is also applicable to Doppler measurement and color Doppler apparatus that handle blood flow signals. That is, in the Doppler measurement, the output of the phasing circuit 14 is complex-multiplied by the reference signal to extract the Doppler detection output, and the result of frequency analysis of the Doppler detection output by a frequency analysis circuit such as FFT is displayed. Explaining with the system a in FIG. 5, the input signal is multiplied by the zero degree component and the 90 degree component generated from the phase shifter 41a to which the reference signal 40a is input by the multipliers 42a and 52a, respectively, to form a complex Doppler signal. The complex Doppler signal is a low-pass filter 43a, 5 that suppresses harmonic components associated with multiplication.
3a and high-pass filters 44a and 54a for removing fixed components such as body walls, frequency analysis is performed by the FFT 55a, and displayed as a Doppler image / waveform. Conventionally, the frequency of the reference signal has a common value at all depths (for example, 2.5 MH) as in the dynamic filter.
z), or 3.5 MHz in the shallow part, and 2.5 MHz in the deep part.

On the other hand, in the present embodiment, a plurality of complex multiplication units having different reference wave frequencies are provided, and each complex multiplication output is individually frequency-analyzed by the corresponding FFT circuit group. The results are weighted and added and displayed as the final Doppler waveform. In FIG. 5, system a,
Reference waves 40a and 40 having different frequencies corresponding to b and c
b and 40c are used. By doing this, by displaying the Doppler component that was previously deleted,
This makes it possible to examine and analyze more detailed spectrum differences, which contributes to disease discrimination. In the display, the frequency analysis results by FFT of 55a, 55b, 55c are weighted and displayed in gray scale by the adder 56, or each hue is assigned in the weighted addition of each frequency analysis result. Alternatively, hue addition may be performed to determine a subtle difference in spectrum on the hue.

In this case, the present invention is essentially different from the conventional method in which the pseudo color is simply arranged in correspondence with the magnitude of the power of the frequency analysis result by a single reference wave. Is.

In addition, in the addition of the frequency analysis result, since the processing of each series uses different reference frequencies, the obtained analysis result is corrected and added according to the following formula. That is, the Doppler frequency Δf
Is the velocity of blood flow, c is the velocity of ultrasonic wave propagation in the body, θ is the angle between the ultrasonic beam and the direction of blood flow, and f is the ultrasonic frequency.
_When it is set to ₀ , it is expressed by the equation (1), so that the correction of the equation (2) is necessary.

Δf = (2f ₀ · v / c) · cos θ (1)

Δf = (2 (f ₀₁ / f ₀₂ + 1 + f ₀₃ / f ₀₂ ) f ₀₂ v / c) · cos θ (2)

When the above-mentioned respective embodiments are examined deeply, the frequency spectrum of the reflected ultrasonic signal from the region of interest shows the attenuation effect due to the tissue or structure that has passed from the pair table to the depth. I am affected. Further, even for the target region having the same depth, if the propagation history of the incident ultrasonic wave is different, the hue is also different. Of course, this problem is secondary to relatively large organs such as the liver, where the history up to the region of interest can be regarded as common.

With respect to this, in the present invention, this problem can be solved by obtaining the spatial difference of the band-divided detection signals in the vicinity of the depth of interest. In FIG. 1, a differentiator and a differentiator are arranged between the detector groups 22a, 22b, 22c and the input variable resistors 23a, 23b, 23c. Alternatively, it has an A / D converter and a memory buffer, and performs high-speed difference between lines or frames. Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0029]

EFFECTS OF THE INVENTION By individually detecting the reception signals divided into frequency bands and then performing weighted addition or hue addition, the generation of speckles due to the phase interference of ultrasonic signals is reduced, and the signals are incurred during the propagation of a living body. It becomes possible to visualize the attenuation effect and emphasize the individual difference between patients and the minute contrast difference between the diseased part and the benign part to discriminate and to greatly expand the information amount of the ultrasonic diagnostic apparatus. It is possible to improve the diagnostic ability.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a conventional circuit configuration.

FIG. 7 is a diagram showing attenuation in a living body and depth dependency of a center frequency of a received signal due to the attenuation.

[Explanation of symbols]

 10 array type ultrasonic probe 11 ultrasonic wave transmission circuit 12 system control section 13 preamplifier group 14 phase adjusting section 15 dynamic filter circuit 16 logarithmic compression circuit 17 TGC circuit 18 detector 19 contour enhancement circuit 20a, 20b, 20c Band-pass filter circuit group 21a, 21b, 21c Logarithmic compression circuit group 22a, 22b, 22c Detection circuit group 23a, 23b, 23c Input variable resistance group 24 Amplifier 25 Feedback variable resistor 26 A / D converter 30a, 30b, 30c A / D converter group 31 Hue imparting circuit 40a, 40b, 40c Reference signal group 41a, 41b, 41c Phase shifter group 42a, 42b, 42c Multiplier group 43a, 43b, 43c High-pass filter group 44a, 44b, 44c Detector group 50 image control unit 55a, 55b, 55c frequency analyzer 5 6 Hue adder 60 Display 220a Multiplying D / A converter 221a Comparator 222a Set value 223a Capacitor

Claims (8)

[Claims] 1. An ultrasonic diagnostic apparatus for processing an ultrasonic signal from the inside of a living body to draw a tomographic image or blood flow information in the body, and means for dividing a frequency band of a received signal, and for each frequency band. An ultrasonic diagnostic apparatus comprising: means for performing individual signal processing; and means for weighted addition of parallel processed outputs. 2. A means for dividing a frequency band of a received signal,
A means for performing logarithmic compression / detection processing for each frequency band,
The ultrasonic diagnostic apparatus according to claim 1, further comprising: a unit for weighting each output, a hue adding unit, and a unit for sampling and displaying the added output. 3. A means for distributing a received signal to a plurality of frequency band filters, a means for independently performing logarithmic compression / detection processing on the outputs of the plurality of filters, a means for weighting each output, and a hue addition. The ultrasonic diagnostic apparatus according to claim 1, further comprising: 4. A means for selecting one or several outputs from each of the parallel-processed outputs in accordance with the depth direction and performing weighted addition, and further comprising:
The ultrasonic diagnostic apparatus according to the item. 5. A means for distributing a received signal to a plurality of band-pass filters, a means for independently compressing and detecting the outputs of the plurality of filters, and a means for adding the hues of the outputs. The ultrasonic diagnostic system according to claim 1, further comprising means for measuring a time average value of outputs, and means for controlling a weight of each hue of hue addition based on the measured value. apparatus. 6. A means for distributing a received signal to a plurality of bandpass filters, a means for independently compressing and detecting the outputs of the plurality of filters, a means for weighting and adding the outputs, and a time average of the outputs. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for measuring a value, and means for controlling the weight of the weighting circuit based on the measured value. 7. A means for distributing a received signal to a plurality of frequency band filters, a means for independently performing logarithmic compression / detection processing on the outputs of the plurality of filters, and a means for obtaining a depth direction difference value of each output. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for weighting the difference value or hue adding means. 8. The ultrasonic wave according to claim 1, wherein a plurality of means for multiplying the input signal and the reference signal are used as means for distributing the received signal to the plurality of band-pass filters. Diagnostic device.