JPH10146338A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a detailed diagnosis by considering influence of in-vivo attenuation by displaying frequency information on a reflected signal by being superimposed on a B mode image in color when this is displayed in shading by generating the B mode image on the basis of the reflected signal obtained by scanning a cross section of a subject by ultrasonic waves. SOLUTION: A reflected signal outputted from a wave receiving circuit 15 to receive a reflected wave through an ultrasonic probe 11, is supplied to a wave detecting circuit 17 and a frequency analyzing circuit 23, and an envelope of the reflected signal is detected by the wave detecting circuit 17, and its amplitude is measured. Proper processing such as correction is performed on its wave detecting signal in a signal processing circuit 19, and an obtained B mode image signal is supplied to a color-luminance synthesizing circuit 21 as a luminance signal BR. On the other hand, frequency information on the reflected signal is individually found on plural points in a cross section in the frequency analyzing circuit 23. A B mode image is displayed as a shading image on a color TV monitor 27 from output of the color-luminance synthesizing circuit 21, and a hue according to a frequency is displayed by being superimposed on it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus which provides a tissue tomographic image (shade image) in a living body by a B-mode method.

[0002]

2. Description of the Related Art The B-mode method is a method of providing two-dimensional information of a tissue structure by expressing a difference in amplitude of a reflected signal by a change in luminance. The amplitude of the reflected signal is affected by not only the difference in acoustic impedance but also the attenuation in the living body. Since the attenuation rate in the living body is not constant,
Even if the reflection intensity is the same between the strong attenuation part and the weak attenuation part, the amplitude of the reflection signal is different and displayed at different luminances.

However, there is no conventional ultrasonic diagnostic apparatus that provides information on the attenuation. Therefore, at present, physicians have not been able to make a thorough diagnosis in consideration of the effects of in vivo attenuation.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of providing attenuation information together with tissue structure information in the B mode.

[0005]

According to the present invention, a cross section of an object is scanned with an ultrasonic wave, and a B signal is obtained based on the obtained reflected signal.
In an ultrasonic diagnostic apparatus that generates a mode image and displays the B-mode image in grayscale, the frequency information of the reflection signal is displayed in a color superimposed on the B-mode image. The frequency information is obtained by comparing the amplitude of the high frequency component and the amplitude of the low frequency component of the reflection signal. The carrier component of the reflected wave is removed from the high frequency component and the low frequency component. A boundary between the high frequency component and the low frequency component is reduced depending on the depth. At least one of a peak frequency, a center frequency, and an average frequency is obtained from the frequency spectrum of the reflection signal as the frequency information. A ripple component is removed from the frequency spectrum. A color bar representing the relationship between the frequency information and the hue is displayed simultaneously with the B-mode image. The correspondence between the frequency information and the hue can be changed. The spatial change of the frequency information is graphically displayed. (Action) Ultrasonic waves propagate in a living body with attenuation. This attenuation has a property that the attenuation increases as the frequency increases. Therefore, by displaying the frequency information in color on the B-mode image, attenuation information can be provided together with the tissue structure information in the B-mode.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic diagnostic apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the ultrasonic diagnostic apparatus according to the present embodiment. At the tip of the ultrasonic probe 11, an array structure of a plurality of piezoelectric elements is provided. Note that the scanning method may be any of a mechanical method and an electronic method, and may be any type such as a sector, a linear, and a convex. Here, the description will be made as an electronic linear scan.

The wave transmitting circuit 13 transmits the ultrasonic probe 1 at the time of transmitting a wave.
Connected to 1. The transmission circuit 13 includes a clock generator, a rate pulse generator, a transmission delay circuit, a pulser, and a high-speed switch. The clock generator generates a clock pulse. The rate pulse generator divides the clock pulse,
For example, a rate pulse of 5 KHz is generated. These rate pulses are distributed into n pulses, and are individually given delay times required for focusing the ultrasonic waves in a beam form by the transmission delay circuit, and are sent to the n pulsers.

Each of the n pulsers outputs a high-frequency drive pulse at the timing of receiving the rate pulse. n
The driving pulses are supplied to the n piezoelectric elements via the high-speed switch. Thereby, ultrasonic pulses are transmitted from the n piezoelectric elements to the subject in a beam form.

[0009] The ultrasonic pulse partially reflects at the boundary of the acoustic impedance in the subject, and the rest passes through the boundary. The ultrasonic pulse propagates inside the subject while repeating reflection and passage. Ultrasound and reflected waves are attenuated during propagation. The higher the frequency, the more susceptible to this attenuation.

The receiving circuit 15 is connected to the ultrasonic probe 11 at the time of receiving a wave, and receives the reflected wave as an electric signal via the ultrasonic probe 11. The receiving circuit 15 includes n preamplifiers, a reception delay circuit, and an adder. Electric signals from the same n piezoelectric elements as transmitted are individually amplified by n preamplifiers, given a delay time opposite to that at the time of transmission by a reception delay circuit, and added by an adder, Further, it is output as a reflection signal.

In order to execute an electronic linear scan, the high-speed switch comprises n piezoelectric elements connected to the transmitting circuit 13 and the receiving circuit 15, one for each transmitting and receiving wave, or a predetermined number. It is shifted by the number of piezoelectric elements. Thereby, the cross section of the subject is scanned by the ultrasonic waves.

The reflected signal output from the receiving circuit 15 is
The signal is supplied to the detection circuit 17 and the frequency analysis circuit 23.
The detection circuit 17 detects the envelope of the reflected signal and measures its amplitude. The signal processing circuit 19 performs appropriate processing such as correction on the detection signal output from the detection circuit 17. The signal (B-mode image signal) output from the signal processing circuit 19 is supplied to the color / luminance combining circuit 21 as a luminance signal BR.

The frequency analysis circuit 23 obtains the frequency information of the reflection signal individually for a plurality of points in the cross section, and supplies the frequency signal _Finfo to the color / luminance synthesis circuit 21. Due to the above-mentioned attenuation phenomenon, the degree of attenuation of the ultrasonic wave is:
This is reflected in the frequency information of the reflected signal.

The color / luminance synthesis circuit 21 determines the luminance components of the RGB signals according to the luminance signal BR,
The hue component of the RGB signal is determined according to _info . This R
GB signal is digital scan converter (DSC)
25 and converted to a TV format signal,
It is supplied to the monitor 27. On the color TV monitor 27,
The B-mode image is displayed as a grayscale image, and a hue corresponding to the frequency is superimposed on the image.

FIG. 2 shows a detailed configuration of the frequency analysis circuit 23 of FIG. Frequency analyzing circuit 23, the frequency distribution of the reflected signal, it is in or lower tendency tends to be higher than the reference frequency f _0, further the reference frequency f ₀ or more high-frequency component amplitude and a reference frequency f ₀ following the low frequency It is configured to be able to analyze the difference between the component and the amplitude. Note that the reference frequency f ₀ can be adjusted through a panel operation by an operator.

The high-pass filter 29 is provided for extracting only high-frequency components higher than the cutoff frequency f _H contained in the reflected signal from the receiving circuit 15. The cut-off frequency f _H is set to + 3 dB relative to the reference frequency f _0. On the other hand, the low-pass filter 37
5 is provided to extract only low-frequency components lower than the cutoff frequency f _L included in the reflected signal from the reference numeral 5. This cutoff frequency f _L is -3 dB with respect to the reference frequency f ₀ .
Is set to

Here, the cutoff frequencies f _H , f
_L did not match the reference frequency f ₀ , that is, f _H
= F _L = f ₀ and f _H > f _L are not used because the filter characteristics are not sharp and the overlap between them is reduced.

The high-frequency component extracted by the high-pass filter 29 is passed through an envelope detection circuit comprising an absolute value circuit 31 and a low-pass filter 33, from which the carrier component of the ultrasonic wave is removed, the amplitude is obtained, and the signal V _H is obtained. Is supplied to the subtraction circuit 35. On the other hand, the low-frequency component extracted by the low-pass filter 37 is similarly removed through an envelope detection circuit composed of an absolute value circuit 39 and a low-pass filter 41, where the carrier component of the ultrasonic wave is removed, the amplitude is obtained, and the signal is obtained. It is supplied to the subtraction circuit 35 as _VL .

The subtraction circuit 35 subtracts _VL on the low frequency side from _VH on the high frequency side ( _VH - _VL ), and outputs the result as a frequency signal _Finfo . When the frequency signal F _info has a positive polarity, it indicates that the reflected signal has a high frequency tendency, that is, the attenuation is weaker than the standard, and the level indicates the strength of the high frequency tendency. Conversely, the frequency signal F _info
Indicates that the reflected signal has a low-frequency tendency, that is, the attenuation is stronger than the standard, and the level indicates the strength of the low-frequency tendency. Note that the standard here means a standard attenuation degree dependent only on the propagation distance of the ultrasonic wave, and the standard attenuation degree is determined depending on the reference frequency f ₀ .

FIG. 4 shows the depth-dependent characteristics of the cut-off frequency f _H of the high-pass filter 29 and the cut-off frequency f _L of the low-pass filter 37. Since the attenuation increases with the propagation distance, the deeper the attenuation, the stronger the attenuation, and the shallower the attenuation. Therefore, to more accurately determine whether the actual attenuation is stronger or weaker than the attenuation of the standard intensity according to the propagation distance, as shown in FIG.
It is necessary to lower _H and f _L as the depth increases. The high-pass filter 29 and the low-pass filter 37
Each f _H and f _L is configured to decrease as the depth increases. This makes it possible to measure whether the attenuation is strong or weak with high accuracy without being affected by the depth.

FIG. 5 shows a detailed configuration of the color / luminance combining circuit 21 shown in FIG. The color / luminance combining circuit 21 outputs the luminance signal B
The luminance component of the RGB signal is determined according to the level of R, and the hue component of the RGB signal is determined according to the level of the frequency signal _Finfo , that is, the frequency tendency of the reflection signal.

For this reason, the color / luminance synthesizing circuit 21 has a look-up table corresponding to the red signal and outputs an R signal (red signal) corresponding to the luminance signal BR and the frequency signal _Finfo (red signal ROM). A green signal ROM (G-ROM) 45 having a lookup table corresponding to the green signal and outputting a G signal (green signal) corresponding to the luminance signal BR and the frequency signal _Finfo ; And a luminance signal BR and a frequency signal F having a lookup table corresponding to a blue signal.
_{and a blue} signal ROM (B-ROM) 47 for outputting a B signal (blue signal) corresponding to _info .

Each of the ROMs 43, 45, and 47 has a plurality of types of look-up tables.
M43,45,47 selected each look-up table, a variety of hues change for hue and the level change that identifies the frequency trend of the frequency signal F _info (intensity of the frequency trend), for example, when the high-frequency trend red , A low-frequency tendency can be selected to be expressed in blue, or a frequency change from high to low can be represented by a color gradation change from purple to red.

For the luminance signal BR and the frequency signal _Finfo , the RGB signals are given by, for example, the following equations. R = BR × α _AR × F _info G = BR × α _AG × F _info B = BR × α _AB × F _info where α _AR , α _AG and α _AB are coefficients determined by the color selection signal. For example, when the high-frequency tendency is strong (when the frequency signal F _info is positive and the amplitude is high), R is large, and when the low frequency tendency is strong (when the frequency signal F _info is negative and the amplitude is high), B is high. Is large and G is constant, α
_AG × F _info is constant. FIG. 6 shows a change in the RGB signal with respect to the frequency signal F _info when the luminance signal BR is fixed.
Is shown in In the example of FIG. 6, when the frequency component of the reflected signal is relatively concentrated on the reference frequency f ₀ (F
_CENTER (= 0), that is, when the attenuation is average, the image is displayed in the same manner as a normal B-mode gray-scale image only with luminance information without hue. When the reflected signal tends to have a high frequency (F _MAX ), that is, when the attenuation is relatively small, R> G
> The amplitude difference of B is widened. Conversely, when the reflected signal tends to have a low frequency (F _MIN ), that is, when the attenuation is relatively large,
The amplitude difference of B>G> R increases.

FIG. 7 shows an example of a display screen of the color TV monitor 27. By performing coloring according to the frequency trend of the reflected signal as described above, it is understood that the portion where the hue is significantly discontinuous with respect to the surroundings has a different attenuation tendency from that of the surroundings. It is possible to improve the interpretation accuracy of the grayscale image in the mode.

FIG. 8 shows another example of the display screen of the color TV monitor 27. A color bar representing the relationship between frequency and hue is displayed together with the B-mode image colored according to the frequency tendency of the reflected signal. Thereby, the observer can easily know the frequency tendency of the reflected signal, that is, the degree of attenuation, from the hue. It is also effective to display the color bar with a scale and to display the minimum frequency and the maximum frequency.

FIG. 9 shows still another example of the display screen of the color TV monitor 27. When the line markers are displayed on the image in the depth direction and the scan direction, and the operator adjusts the position of each line marker on the region of interest through a panel operation, the spatial distribution of the frequency along each line marker is changed. Displayed as a graph. In addition, a point marker is displayed on the image, and when the operator adjusts the position of the point marker on the site of interest through a panel operation, the frequency on the point marker is displayed as a numerical value.

As shown in FIG. 10, fast Fourier transform processing (FFT) may be employed as frequency analysis. A fast Fourier transform processing circuit (FFT) 49 performs a fast Fourier transform process on the reflection signal V _ECHO . FIG. 11A shows an example of a frequency spectrum as a result of the FFT. This frequency spectrum has severe irregularities due to the influence of undesired phenomena such as multiple reflection in the subject, that is, contains a ripple component. If the next operation is performed as it is, the stability is poor. Therefore, this unnecessary ripple component is removed by the moving average process in the low-pass filter 51 (FIG. 11).
(B)). Various frequency information can be obtained from the frequency spectrum. For example, the arithmetic circuit 53 obtains the peak frequency f _P , the arithmetic circuit 55 obtains the center frequency f _C ,
Arithmetic circuit 57 obtains the average frequency f _m. Either the operator by the peak frequency f _P selected via the panel operation center frequency f _C average frequency f _m is supplied to the color-luminance composition or color 21 as the frequency signal F _info via the selection switch 59, Coloring is performed accordingly.

As described above, the frequency information of the reflected signal is provided as attenuation information, and a highly accurate diagnosis can be made from the B-mode image with reference to the attenuation information. The present invention is not limited to the embodiments described above, and can be implemented with various modifications.

[0030]

According to the present invention, there is provided an ultrasonic diagnostic apparatus which scans a cross section of an object with an ultrasonic wave, generates a B-mode image based on the obtained reflection signal, and displays the B-mode image in gray scale. The frequency information of the reflected signal is displayed in a color superimposed on the B-mode image.

The attenuation of the high frequency component of the ultrasonic wave is greater than the attenuation of the low frequency component. That is, the frequency information of the reflected signal includes the attenuation information. Therefore, by displaying the frequency information in color on the B-mode image, attenuation information can be provided together with the tissue structure information in the B-mode.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a frequency analysis circuit of FIG. 1;

FIG. 3 is a filter characteristic diagram of the frequency analysis circuit of FIG. 1;

FIG. 4 is a diagram showing a depth-dependent characteristic of a cutoff frequency of the frequency analysis circuit of FIG. 1;

FIG. 5 is a block diagram illustrating a configuration of a color / luminance combining circuit in FIG. 1;

FIG. 6 is a color composition characteristic diagram by the color / luminance composition circuit of FIG. 1;

FIG. 7 is a view showing an example of a display screen of the color TV monitor of FIG. 1;

FIG. 8 is a view showing another example of the display screen of the color TV monitor of FIG. 1;

FIG. 9 is a view showing still another example of the display screen of the color TV monitor of FIG. 1;

FIG. 10 is a block diagram showing a configuration of another frequency analysis circuit employing the FFT method.

11 is an explanatory diagram illustrating the analysis of the frequency analysis circuit of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ultrasonic probe 13 ... Transmission circuit, 15 ... Receiving circuit, 17 ... Detection circuit, 19 ... Signal processing circuit, 21 ... Color / brightness synthesis circuit, 23 ... Frequency analysis circuit, 25 ... Digital scan converter, 27 ... Color TV monitor, 29 high-pass filter, 31 absolute value circuit, 33 low-pass filter, 35 subtraction circuit, 37 low-pass filter, 39 subtraction circuit, 41 low-pass filter, 43 ROM for R signal, 45 G Signal ROM, 47 B signal ROM, 49 FFT circuit, 51 low-pass filter, 53 peak frequency calculation circuit, 55 center frequency calculation circuit, 57 average frequency calculation circuit, 59 selection switch.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Shibanuma 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture Inside the Nasu Plant of Toshiba Corporation (72) Inventor Yoshitaka Watanabe 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture Toshiba Inside Medical Engineering Co., Ltd. (72) Inventor Gen Nagano 1385-1 Shimoishigami, Otawara-shi, Tochigi Pref. Toshiba Nasu Factory Co., Ltd.

Claims (9)

[Claims] 1. A cross section of an object is scanned by an ultrasonic wave, and a B-mode image is generated based on an obtained reflection signal.
An ultrasonic diagnostic apparatus for displaying a mode image in different shades, wherein frequency information of the reflected signal is displayed in a color superimposed on the B-mode image. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the frequency information is obtained by comparing an amplitude of a high-frequency component and an amplitude of a low-frequency component of the reflection signal. 3. The ultrasonic diagnostic apparatus according to claim 2, wherein an ultrasonic carrier component is removed from said high frequency component and said low frequency component. 4. The ultrasonic diagnostic apparatus according to claim 2, wherein a boundary between the high-frequency component and the low-frequency component is reduced depending on a depth. 5. At least one of a peak frequency, a center frequency, and an average frequency from a frequency spectrum of the reflection signal.
The ultrasonic diagnostic apparatus according to claim 1, wherein one of the frequency information is obtained as the frequency information. 6. The ultrasonic diagnostic apparatus according to claim 5, wherein a ripple component is removed from said frequency spectrum. 7. The ultrasonic diagnostic apparatus according to claim 1, wherein a color bar representing a relationship between the frequency information and the hue is displayed simultaneously with the B-mode image. 8. The ultrasonic diagnostic apparatus according to claim 1, wherein the correspondence between the frequency information and the hue can be changed. 9. The ultrasonic diagnostic apparatus according to claim 1, wherein a spatial change of the frequency information is displayed as a graph.