JPH1176231A - Ultrasound diagnostic equipment - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of effectively enhancing a contrast echo component with respect to a tissue echo component. The present invention provides an ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast agent into a subject and scanning with an ultrasonic wave. The apparatus includes a band-pass filter 9 to be extracted and a band elimination filter 10 for suppressing a specific band component from the extracted harmonic components in order to enhance a contrast echo component due to a contrast effect of a contrast agent.

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 for injecting a contrast medium containing air bubbles as a main component into a subject from an artery and imaging a blood flow with high contrast.

[0002]

2. Description of the Related Art Conventionally, in the evaluation of the perfusion area of the blood flow in the myocardium, a so-called 5% human albumin in which bubbles are generated manually or by a sonicator is injected into a subject from a catheter placed in the aorta. Myocardial contrast echo has been studied. In this myocardial contrast echo method, the perfusion area of the myocardial blood flow into which the contrast agent flows is:
The brightness is enhanced and displayed on the B mode (tissue tomographic image). Similarly, a contrast echo method has been studied in the abdominal region in order to evaluate the perfusion area of blood flow or the vasculature governing the tumor.

[0003] Such a contrast echo method is applied to an ultrasonic diagnostic apparatus for general inspection. As a method for evaluating the contrast echo method, in addition to a method of visually observing a brightness enhancement region on a B-mode image, recently, There is also a movement to quantitatively evaluate a change in luminance level using a workstation.

In recent years, an ultrasonic contrast agent which is effective for evaluating the left heart system by intravenous injection has been developed, and a contrast echo method using this kind of a new contrast agent has been attempted. Its usefulness has been confirmed in cavities and abdomen.
In the circulatory field, it is effective for detecting the boundary between the endocardium and the heart chamber,
It is effective for observation of myocardial morphology, evaluation of wall motion, evaluation of heart chamber volume, and the like. In addition, a significant improvement in the sensitivity of the blood flow in the heart chamber in the Doppler mode has been recognized, and an improvement in the diagnostic performance of cardiac function evaluation is expected. In the abdominal field and peripheral blood vessels / head, significant improvement in the detection ability of color Doppler has been observed, and improvement in the diagnostic ability has been reported, for example, in the detection of vegetative blood vessels of malignant tumors.

Further, a harmonic imaging method utilizing the non-linear vibration characteristics of air bubbles, a flash echo method and an acoustic emission method for positively detecting and imaging non-linear vibrations at the time of air bubble collapse, and the like have been proposed. It is expected that visualization of perfusion of myocardium and organ parenchyma with the agent will be possible in the near future.

[0006]

However, in contrast echo by intravenous injection, the contrast agent concentration is lower than that in arterial injection, and therefore, it is not expected to increase the brightness much. The problem of being buried in the tissue echo image from the surroundings was left unresolved.

In addition, especially in the case of color Doppler in the abdomen, motion artifacts caused by movement of surrounding tissues due to respiration and the movement of blood vessel walls become a problem, and the low flow velocity detection ability is limited. It was difficult to effectively enhance with contrast agents.

The above-described harmonic imaging method, flash echo method, and acoustic emission method are very promising methods for actively utilizing only the echo (contrast echo) component scattered by bubbles to form an image. . What is important in this method is how to effectively suppress tissue echo components derived from surrounding organs and extract contrast echo components derived from a contrast agent with high sensitivity.

[0009] In all of the above-mentioned imaging methods, the common basic technique is to detect a harmonic component (harmonic component) derived from the non-linear vibration of the bubble. However, the organ also scatters the harmonic component due to the nonlinearity of propagation. It is known to Although the harmonic component of the tissue echo is at a relatively low level, there is no doubt that it interferes with the ability to extract the contrast echo component. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of effectively enhancing a contrast echo component with respect to a tissue echo component.

[0010]

According to the present invention, a contrast echo component has a broader band due to a non-linear vibration characteristic caused by a contrast agent than a tissue echo component having a similar spectrum to a transmission spectrum and a relatively sharp spectrum. Accordingly, the effect of suppressing the specific band is greater in the tissue echo component than in the contrast echo component, so that the contrast echo component can be enhanced as a result.

According to the present invention, the tissue echo component has a high similarity to the transmission spectrum of the ultrasonic wave, while the contrast echo component has a low similarity due to the non-linear vibration characteristics of the contrast agent. Therefore, the transmission spectrum of the ultrasonic wave is inverted. The present invention extracts the harmonic component from the echo signal by passing the echo signal through a filter having the above-mentioned filter characteristics, thereby effectively suppressing the tissue echo component and consequently enhancing the contrast echo component. Then, even if the envelope of the extracted harmonic component is detected by a detection circuit, and a high-frequency component is further extracted from the envelope signal, the contrast echo component can be similarly enhanced.

According to the present invention, the image data generated based on the harmonic components extracted from the echo signal is passed through a filter for extracting a relatively high spatial frequency component, whereby the tissue is destroyed due to the destruction of the contrast agent. This means that a contrast echo image that fluctuates more spatially than an image, that is, a high spatial convergence, can be effectively enhanced.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) FIG. 1 shows the configuration of an ultrasonic diagnostic apparatus according to a first embodiment. In the ultrasonic probe 1, a plurality of piezoelectric elements are arranged at a distal end portion in order to mediate between an apparatus main body that handles an electric signal and a subject that applies internal information to ultrasonic waves. A clock generation circuit 2, a transmission delay circuit 3, a pulser 4, and the like are provided for driving the probe 1 to irradiate an ultrasonic wave to a subject, and a clock oscillated from the clock generation circuit 2 is transmitted to the transmission delay circuit. 3 and is used as a trigger for the pulsar 4. Then, a driving pulse is applied from the triggered pulser 4 to the piezoelectric element of the probe 1 around the fundamental frequency fd. Thereby, an ultrasonic wave is generated from the vibrated piezoelectric element of the probe 1.

The ultrasonic wave propagates in the living body, and is reflected one after another on a discontinuous surface of acoustic impedance in the middle of the ultrasonic wave.
This reflection intensity mainly depends on the difference in acoustic impedance of the discontinuous surface. The echo due to such reflection returns to the probe 1, vibrates the piezoelectric element, and generates a weak electric signal. This electric signal is amplified by the preamplifier 5, given an appropriate delay time by the reception delay and addition circuit 6, and added. This gives directivity to the echo. The echo signal is supplied to the fundamental-band bandpass filter 7 and the non-linear bandpass filter 9.

First, the bandpass filter 7 for the fundamental wave
The signal passes through a frequency component (fundamental frequency component) in a band around the fundamental frequency fd included in the echo signal, and suppresses frequency components in other bands. Thereby, a fundamental frequency component can be extracted.

On the other hand, the nonlinear band-pass filter 9 is
Passes a frequency component (high-frequency component) within a band centered on an integral multiple of the fundamental frequency fd contained in the echo signal, here a twice as high frequency (2 × fd), and passes through another band including the fundamental frequency component. Suppress frequency components. Thereby, higher harmonic components can be extracted. Then, the non-linear band elimination filter (band elimination filter) 10 converts the high-frequency component extracted by the non-linear band-pass filter 9
It is narrower than the pass band of the non-linear band-pass filter 9 and removes frequency components within a specific band centered on the center frequency (2 × fd) of this pass band, and passes only frequency components of other bands. I do. Thereby, the component of the tissue echo reflected by the tissue can be suppressed, and only the component of the contrast echo reflected by the contrast agent (bubble) can be effectively extracted. The details will be described later.

The receiver 8 detects the echo signal and performs logarithmic amplification to generate B-mode image (tissue tomographic image) data. This image data is displayed on a monitor 12 via a digital scan converter (DSC) 11 in shades.

Here, when the receiver 8 processes the echo signal mainly composed of the fundamental frequency component that has passed through the bandpass filter 7 for the fundamental wave, the amount of the contrast agent is small and the contrast effect is sufficient. Otherwise, the image of the contrast region may be buried in the tissue image. On the other hand, when the receiver 8 processes an echo signal mainly containing a contrast echo component that has passed through the non-linear band-pass filter 9 and the non-linear band elimination filter 10, even if the amount of the contrast agent is small, the contrast effect is low. Even if the situation is not sufficient, the distribution of the contrast agent can be captured with high contrast without being buried in the surrounding tissue image.

As described above, the function of the non-linear band-pass filter 9 and the non-linear band elimination filter 10 suppresses the component of the tissue echo reflected by the tissue, and is reflected by the contrast agent (bubble). The reason is that only the components of the contrast echo can be effectively extracted. Less than,
This will be described.

FIG. 2A shows a spectrum of an ultrasonic wave transmitted from the probe 1. Fundamental frequency fd
In addition to the above component, a harmonic component of an integral multiple thereof, for example, 2.times.fd is included. Note that the spread of these components is determined depending on the duration of the pulse, as is well known.

FIG. 2B shows the spectrum of the echo signal. The spectrum of the tissue echo signal reflected from the boundary of the tissue is indicated by a solid line, and the spectrum of the contrast echo signal reflected from the surface of the contrast agent is indicated by a broken line. Are respectively shown. Here, as can be seen by comparing FIGS. 2A and 2B, the similarity of the spectrum of the tissue echo to the transmission spectrum is high.
The similarity of the contrast echo spectrum to the transmission spectrum is low. This is due to the fact that although the linearity of tissue vibration is relatively high, the contrast agent (bubble) has a strong tendency to nonlinearly vibrate, so that the spectrum of the contrast echo is broadened compared to the tissue echo. I do.

FIG. 2C shows the spectrum of the tissue echo signal and the spectrum of the contrast echo signal that have passed through the non-linear band-pass filter 9, respectively. At this point, the contrast echo component is larger than the tissue echo component, and as shown in FIG. 3 (a), it is considered that the contrast effect can be sufficiently exerted. As described above, the nonlinear band elimination filter 10 is narrower than the pass band of the non-linear band pass filter 9 and has a center frequency (2 ×
The frequency components within a specific band centered on fd) are removed.

FIG. 2D shows the spectra of the tissue echo signal and the contrast echo signal that have passed through the non-linear band elimination filter 10, respectively. By such processing of the non-linear band elimination filter 10, the tissue echo components are concentrated near "2 * fd", and the suppression effect is great. However, the contrast echo component has "2 * fd". Since it is dispersed at the center and s, but has a very wide band, only a part is removed and most of the other remains (passes).

Therefore, as shown in FIG. 3B, even if the amount of the contrast agent is small and the contrast effect is not sufficient, the distribution of the contrast agent is high without being buried in the surrounding tissue image. It is possible to capture with contrast. As a result, the intermittent interval can be shortened in the flash echo, the diagnostic performance can be improved, and in the harmonic method, even finer arteries can be imaged. (Second Embodiment) FIG. 4 shows the configuration of an ultrasonic diagnostic apparatus according to a third embodiment. In FIG. 4, the same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. This embodiment is similar to the previous embodiment in that the echo signal from the reception delay and addition circuit 6 is sent to the receiver 8 after passing through the filter 16, but the coefficient data from the CPU 18 and the coefficient data storage unit 17 are used. There is a characteristic only in the filter characteristic of the filter 16 determined by this.

Here, the similarity of the spectrum of the tissue echo to the transmission spectrum is high.
The similarity of the contrast echo spectrum to the transmission spectrum is low as described above by comparing FIGS. 2A and 2B. Focusing on this point, by setting the filter characteristic of the filter 16 to a waveform in which the spectrum of the transmission ultrasonic wave is mirror-inverted, a tissue echo component similar to the spectrum of the transmission ultrasonic wave is effectively suppressed, and the contrast is improved. The echo component is emphasized as a result. (Third Embodiment) In a third embodiment, as shown in FIG. 5, an echo signal having a harmonic component as a main component in a nonlinear band-pass filter 9 is subjected to envelope detection and logarithm detection by a receiver 8. When amplification is performed and the high-pass filter 19 is applied thereafter, the amount of the high-pass filter 19 that passes through the broadband contrast echo component is larger than that of the tissue echo component that remains sharp, Therefore, the same effects as in the previous embodiment can be obtained. (Fourth Embodiment) In a fourth embodiment, as shown in FIG. 6, an image generated by a receiver 8 based on an echo signal having a harmonic component as a main component in a non-linear bandpass filter 9 is used. The data is transferred to the input / output buffer 20 and the frame memory 21 in the digital scan converter 11.
Through a TV scan system, and then to a high-pass spatial filter 22, where components having a relatively low spatial frequency are removed, and only components having a relatively high spatial frequency are passed. This is output via the buffer 23.

Here, the tissue image is relatively stable both temporally and spatially, that is, the spatial frequency is relatively low, whereas the contrast agent image is obtained by mixing the contrast agent into the blood flow. Since it contracts and expands repeatedly by flowing and irradiation of ultrasonic waves, it is very unstable both temporally and spatially, that is, the spatial frequency becomes relatively high.

Accordingly, by passing such image data through the high-pass type spatial filter 22, a tissue image having a relatively low spatial frequency is suppressed, and an image of a contrast agent having a relatively high spatial frequency is effectively obtained. It can be passed.

In the processing mode of the fourth embodiment, as shown in FIG. 7, even before the digital scan converter 11 rearranges the image data from the TV scan system, the image data from the receiver 8 is converted. Image memory 24
And the spatial filter 25 can be modified to perform the same filtering. The present invention is not limited to the embodiments described above, and can be implemented with various modifications.

[0029]

According to the present invention, the contrast echo component has a broader band due to the non-linear vibration characteristic of the contrast agent than the tissue echo component having a spectrum similar to the transmission spectrum and having a relatively sharp spectrum. Is greater in the tissue echo component than in the contrast echo component, so that the contrast echo component can be enhanced as a result.

According to the present invention, the tissue echo component has a high similarity to the transmission spectrum of the ultrasonic wave, while the contrast echo component has a low similarity due to the non-linear vibration characteristics of the contrast agent. Therefore, the transmission spectrum of the ultrasonic wave is inverted. The present invention extracts the harmonic component from the echo signal by passing the echo signal through a filter having the above-mentioned filter characteristics, thereby effectively suppressing the tissue echo component and consequently enhancing the contrast echo component. Then, even if the envelope of the extracted harmonic component is detected by a detection circuit and a high-frequency component is extracted from the envelope signal, the contrast echo component can be similarly enhanced.

According to the present invention, the image data generated based on the harmonic components extracted from the echo signal is passed through a filter for extracting a relatively high spatial frequency component, whereby the tissue is destroyed due to the destruction of the contrast agent. This means that a contrast echo image that fluctuates more spatially than an image, that is, a high spatial convergence, can be effectively enhanced.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a change in the spectrum of a tissue echo and a contrast echo by the BPF and BRF of FIG. 1;

3 is a comparison diagram of an ultrasonic image obtained through the fundamental wave BPF of FIG. 1 and an ultrasonic image obtained through the non-linear BPF and the non-linear BEF.

FIG. 4 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a second embodiment.

FIG. 5 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a third embodiment.

FIG. 6 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a fourth embodiment.

FIG. 7 is a block diagram showing a modification of the fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Clock generation circuit, 3 ... Transmission delay circuit, 4 ... Pulser, 5 ... Preamplifier, 6 ... Reception delay and addition circuit, 7 ... Bandpass filter for fundamental waves, 8 ... Receiver, 9 ... Non-linear band-pass filter, 10 ... non-linear for band-elimination filter, 11 ... digital scan converter, 12 ... monitor, 13 ... quadrature phase detection circuit, 13 ₁ ... mixer, 13 ₂ ... mixer, 13 ₃ ... low-pass Filter, 13 ₄ : low-pass filter, 14: high-pass filter, 15: high-pass filter, 16: filter, 17: coefficient data storage unit, 18: CPU, 19: high-pass filter, Reference Signs List 20: input / output buffer, 21: frame memory, 22: high-pass filter, 23: input / output buffer, 24: image memory, 25: spatial filter Data operation unit.

Claims (4)

[Claims] 1. An ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast agent into a subject and scanning with an ultrasonic wave, wherein a harmonic component is extracted from the echo signal. An ultrasonic diagnostic apparatus comprising: a filter; and a filter that suppresses a specific band component from the extracted harmonic components to enhance a contrast echo component due to a contrast effect of the contrast agent. 2. An ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast agent into a subject and scanning with an ultrasonic wave, wherein a contrast echo component due to a contrast effect of the contrast agent is provided. An ultrasonic diagnostic apparatus characterized in that the echo signal is passed through a filter having a filter characteristic obtained by inverting the transmission spectrum of the ultrasonic wave in order to emphasize the ultrasonic wave. 3. An ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast agent into a subject and scanning with an ultrasonic wave, wherein a harmonic component is extracted from the echo signal. A filter, a detection circuit for detecting an envelope of the echo signal having the extracted harmonic component as a main component, and the detected envelope signal for enhancing a contrast echo component due to a contrast effect of the contrast agent. An ultrasonic diagnostic apparatus, comprising: a filter for extracting a high-frequency component from an image. 4. An ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast agent into a subject and scanning with an ultrasonic wave, wherein a harmonic component is extracted from the echo signal. A filter, a circuit that generates image data from the extracted harmonic components, and a filter that extracts a relatively high spatial frequency component from the image data to enhance a contrast echo component due to a contrast effect of the contrast agent. An ultrasonic diagnostic apparatus comprising: