JP3908348B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus for injecting a contrast medium mainly composed of bubbles from an artery into a subject and imaging a blood flow with high contrast.
[0002]
[Prior art]
Conventionally, in the evaluation of the perfusion region of intramyocardial blood flow, there is a so-called myocardial contrast echo method in which 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. Have been studied. In this myocardial contrast echo method, the perfusion region of the intramyocardial blood flow into which the contrast agent flows is displayed with enhanced brightness on the B mode (tissue tomographic image). Similarly, the contrast echo method has been studied in the abdominal region in order to evaluate the perfusion region of the blood flow or the dominant vasculature of the tumor.
[0003]
Such a contrast echo method is applied in an ultrasonic diagnostic apparatus for general examination. As an evaluation method thereof, in addition to a method of visually observing a brightness enhancement region on a B-mode image, recently, a workstation is used. There is also a movement to evaluate the change of the luminance level quantitatively by using.
[0004]
In recent years, an ultrasound contrast agent effective for the evaluation of the left heart system by intravenous injection has been developed, and a contrast echo method using this kind of new contrast agent has been attempted, and the head, heart chamber, abdomen have already been tried. Its usefulness has been confirmed. In the cardiovascular field, it is effective for detecting the boundary between the endocardium and the heart chamber, and is effective for observation of the myocardial morphology, evaluation of wall motion, evaluation of the heart chamber volume, and the like. In addition, a significant improvement in sensitivity in the Doppler mode of intracardiac blood flow is recognized, and an improvement in the diagnostic ability of cardiac function evaluation is expected. In the abdominal field and peripheral blood vessels / head, a significant improvement in color Doppler detection has been observed, and improved diagnostic performance has been reported for detection of nutritional blood vessels in malignant tumors.
[0005]
In addition, harmonic imaging using nonlinear vibration characteristics of bubbles and flash echo and acoustic emission methods that actively detect and visualize nonlinear vibrations during bubble collapse have been proposed. It is expected that imaging of myocardium and organ perfusion will be possible in the near future.
[0006]
[Problems to be solved by the invention]
However, in contrast echo by intravenous injection, the contrast agent concentration is thinner than that of arterial injection, so brightness enhancement can not be expected so much, and the enhancement region is in the tissue echo image from the surroundings such as myocardium and liver parenchyma The problem of being buried was left unresolved.
[0007]
Also, especially during color Doppler in the abdomen, motion artifacts due to movement of surrounding tissues due to breathing and the movement of the blood vessel wall are problematic, and there is a limit to the low flow velocity detection ability, and the peripheral blood vessels of the organ substance are covered with a contrast agent. It was difficult to enhance effectively.
[0008]
The above-described harmonic imaging method, flash echo method, and acoustic emission method are very promising because they are images that actively utilize only the components of echoes (contrast echoes) scattered by bubbles. What is important in this method is how to effectively suppress the tissue echo component derived from surrounding organs and extract the contrast echo component derived from the contrast agent with high sensitivity.
[0009]
All of the above-mentioned imaging methods have a common basic technique of detecting harmonic components (harmonic components) derived from non-linear vibrations of bubbles, but organs may also scatter harmonic components due to nonlinear propagation characteristics. Are known. Although the harmonic component of the tissue echo is relatively low, there is no doubt that the ability to extract the contrast echo component is hindered.
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.
[0010]
[Means for Solving the Problems]
In the present invention, the contrast echo component is broadened by the non-linear vibration characteristics of the contrast agent rather than the tissue echo component that is similar to the transmission spectrum and has a relatively sharp spectrum. Since the tissue echo component appears larger than the echo component, the contrast echo component can be enhanced as a result.
[0011]
In the present invention, the tissue echo component has a high similarity to the ultrasonic transmission spectrum, while the contrast echo component has a low similarity due to the non-linear vibration characteristics of the contrast agent. The present invention, which effectively suppresses the tissue echo component and consequently enhances the contrast echo component by passing the echo signal through a filter having the following, extracts a harmonic component from the echo signal, and 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.
[0012]
In the present invention, image data generated based on the harmonic component extracted from the echo signal is passed through a filter that extracts a relatively high spatial frequency component, thereby causing the contrast agent to be destroyed, and thereby causing the contrast agent to be destroyed. It is possible to effectively enhance a contrast echo image having a large spatial variation, that is, a high spatial collection.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows the configuration of an ultrasonic diagnostic apparatus according to the first embodiment. In the ultrasonic probe 1, a plurality of piezoelectric elements are arranged at the tip portion in order to mediate between the apparatus main body side that handles electrical signals and the subject side that imparts internal information to the ultrasonic waves. In order to drive the probe 1 and irradiate the subject with ultrasonic waves, a clock generation circuit 2, a transmission delay circuit 3, a pulser 4 and the like are provided, and a clock oscillated from the clock generation circuit 2 is transmitted to the transmission delay circuit. 3 is appropriately delayed and used as a trigger for the pulser 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. Thus, ultrasonic waves are generated from the piezoelectric element of the probe 1 that vibrates.
[0014]
This ultrasonic wave propagates in the living body, and is reflected one after another at a discontinuous surface of acoustic impedance in the middle. 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 and added with an appropriate delay time by the reception delay and addition circuit 6. This gives directivity to the echo. The echo signal is supplied to the fundamental band-pass filter 7 and the nonlinear band-pass filter 9.
[0015]
First, the fundamental band pass filter 7 passes a frequency component (fundamental frequency component) in a band centered on the fundamental frequency fd included in the echo signal, and suppresses frequency components in other bands. Thereby, a fundamental frequency component can be extracted.
[0016]
On the other hand, the non-linear band-pass filter 9 passes a frequency component (high frequency component) in a band centered on an integral multiple of the fundamental frequency fd included in the echo signal, here a frequency twice as high (2 × fd). Then, frequency components in other bands including the fundamental frequency component are suppressed. Thereby, a harmonic component can be extracted. The non-linear band elimination filter (band elimination filter) 10 is narrower than the pass band of the non-linear band-pass filter 9 from the high-frequency component extracted by the non-linear band-pass filter 9 and The frequency components in a specific band centered on the center frequency (2 × fd) are removed, and only the frequency components in other bands are passed. 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 extracted effectively. This will be described later in detail.
[0017]
The receiver 8 generates B-mode image (tissue tomographic image) data by detecting the echo signal and logarithmically amplifying it. This image data is displayed in gray on a monitor 12 via a digital scan converter (DSC) 11.
[0018]
Here, when the receiver 8 processes an echo signal whose main component is the fundamental frequency component that has passed through the fundamental wave band-pass filter 7, in a situation where the amount of contrast agent is small and the contrast effect is not sufficient. There is a possibility that the image of the contrast region is buried in the tissue image. On the other hand, when the receiver 8 processes an echo signal whose main component is the contrast echo component that has passed through the non-linear bandpass filter 9 and the non-linear band-removal filter 10, the contrast effect is small even if the amount of contrast medium is small. Even in an unsatisfactory situation, the contrast agent distribution can be captured with high contrast without being buried in the surrounding tissue image.
[0019]
As described above, this is due to the action of the non-linear band-pass filter 9 and the non-linear band elimination filter 10 to suppress the component of the tissue echo reflected by the tissue and the contrast echo reflected by the contrast agent (bubble). The reason is that only the components can be extracted effectively. This will be described below.
[0020]
FIG. 2A shows the spectrum of ultrasonic waves transmitted from the probe 1. In addition to the component of the fundamental frequency fd, a harmonic component of an integral multiple of, for example, 2 × fd is included. As is well known, the spread of these components depends on the pulse duration.
[0021]
FIG. 2B shows the spectrum of the echo signal. The solid echo shows the spectrum of the tissue echo signal reflected from the tissue boundary, and the broken line shows the spectrum of the contrast echo signal reflected from the contrast agent surface. ing. 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, but the similarity of the spectrum of the contrast echo to the transmission spectrum is low. This is due to the fact that the linearity of tissue vibration is relatively high, but the contrast agent (bubbles) has a strong tendency for non-linear vibration, which makes the spectrum of contrast echo wider than that of tissue echo. To do.
[0022]
FIG. 2C shows the spectrums of the tissue echo signal and the contrast echo signal that have passed through the nonlinear bandpass filter 9. At this point, the contrast echo component is larger than the tissue echo component, and as shown in FIG. 3A, it is considered that the contrast effect can be sufficiently exerted. As described above, the non-linear band elimination filter 10 is narrower than the pass band of the non-linear band pass filter 9 and has a frequency within a specific band centered on the center frequency (2 × fd) of this pass band. Remove ingredients.
[0023]
FIG. 2D shows the spectrums of the tissue echo signal and the contrast echo signal that have passed through the nonlinear band elimination filter 10. By the processing of the non-linear band elimination filter 10 as described above, the tissue echo component is concentrated in the vicinity of “2 × fd”, so that the suppression effect is great, but the contrast echo component is “2 × fd”. Although it is dispersed with respect to the center but is very wide, only a part is removed and the other part remains (passes).
[0024]
Therefore, as shown in FIG. 3B, the contrast agent distribution is captured with high contrast without being embedded in the surrounding tissue image even in a situation where the amount of contrast agent is small and the contrast effect is not sufficient. It becomes possible to do. Thereby, in the flash echo, the intermittent interval can be shortened and the diagnostic ability can be improved, and in the harmonic method, even a finer artery can be imaged.
(Second Embodiment)
FIG. 4 shows the configuration of an ultrasonic diagnostic apparatus according to the third embodiment. In FIG. 4, the same parts as those in FIG. In this embodiment, the echo signal from the reception delay and addition circuit 6 is sent to the receiver 8 after passing through the filter 16 as in the previous embodiment, but the coefficient data from the CPU 18 and the coefficient data storage unit 17 are the same. The filter characteristic of the filter 16 determined by
[0025]
Here, the similarity of the spectrum of the tissue echo with respect to the transmission spectrum is high, but the similarity of the spectrum of the contrast echo with respect to the transmission spectrum is lower than that, as compared with FIGS. 2 (a) and 2 (b). That's right. Focusing on this point, the filter characteristic of the filter 16 is set to a waveform obtained by mirror-inverting the spectrum of the transmission ultrasonic wave, thereby effectively suppressing the tissue echo component similar to the spectrum of the transmission ultrasonic wave, and the contrast. As a result, the echo component is emphasized.
(Third embodiment)
As shown in FIG. 5, the third embodiment performs envelope detection and logarithmic amplification on the echo signal whose harmonic component is the main component in the nonlinear band-pass filter 9, and thereafter, When the high-pass filter 19 is applied, the contrast echo component having a wider band has a larger amount of passage through the high-pass filter 19 than the sharp tissue echo component, and therefore, as in the previous embodiment. It is possible to achieve the effect.
(Fourth embodiment)
In the fourth embodiment, as shown in FIG. 6, the image data generated by the receiver 8 based on the echo signal whose harmonic component is the main component in the nonlinear band-pass filter 9 is converted into a digital scan signal. In the converter 11, the TV scan system is rearranged via the input / output buffer 20 and the frame memory 21, and then guided to the high-pass spatial filter 22, where a component having a relatively low spatial frequency is removed, Only relatively high components are allowed to pass through and are output via the input / output buffer 23.
[0026]
Here, the tissue image is relatively stable in terms of time and space, that is, the spatial frequency is relatively low, whereas the contrast agent image is mixed with the blood flow. In addition, since the contraction and the expansion are repeated by irradiation with ultrasonic waves, it is very unstable in time and space, that is, the spatial frequency becomes relatively high.
[0027]
Accordingly, by passing such image data through the high-pass 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 passed. It can be done.
[0028]
In the processing mode of the fourth embodiment, as shown in FIG. 7, the image data from the receiver 8 is converted into the image memory 24 even before the digital scan converter 11 rearranges the TV scan method. And the spatial filter 25 can be modified to perform the same filtering process.
The present invention is not limited to the embodiments described above, and can be implemented with various modifications.
[0029]
【The invention's effect】
In the present invention, the contrast echo component is broadened by the non-linear vibration characteristics of the contrast agent rather than the tissue echo component that is similar to the transmission spectrum and has a relatively sharp spectrum. Since the tissue echo component appears larger than the echo component, the contrast echo component can be enhanced as a result.
[0030]
In the present invention, the tissue echo component has a high similarity to the ultrasonic transmission spectrum, while the contrast echo component has a low similarity due to the non-linear vibration characteristics of the contrast agent. The present invention, which effectively suppresses the tissue echo component and consequently enhances the contrast echo component by passing the echo signal through a filter having the following, extracts a harmonic component from the echo signal, and 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.
[0031]
In the present invention, image data generated based on the harmonic component extracted from the echo signal is passed through a filter that extracts a relatively high spatial frequency component, thereby causing the contrast agent to be destroyed, and thereby causing the contrast agent to be destroyed. It is possible to effectively enhance a contrast echo image having a large spatial variation, that is, a high spatial collection.
[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 changes in the spectrum of tissue echo and contrast echo due to BPF and BRF in FIG. 1;
FIG. 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 the configuration of an ultrasonic diagnostic apparatus according to the fourth embodiment.
FIG. 7 is a block diagram showing a modification of the fourth embodiment.
[Explanation of symbols]
1 ... probe,
2 ... Clock generation circuit,
3 ... transmission delay circuit,
4 ... Pulsa,
5 ... Preamp,
6: Reception delay and addition circuit,
7. Bandpass filter for fundamental wave,
8 ... Receiver,
9: Non-linear band-pass filter,
10: Non-linear band elimination filter,
11: Digital scan converter,
12 ... Monitor,
13: Quadrature 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,
20: I / O buffer,
21 ... Frame memory,
22 ... high-pass filter,
23 ... I / O buffer,
24 ... Image memory,
25: Spatial filter calculation unit.

Claims (4)

In an ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast medium into a subject and scanning with ultrasonic waves, a filter that extracts harmonic components from the echo signal, and the contrast An ultrasonic diagnostic apparatus comprising: a filter that suppresses a specific band component from the extracted harmonic component in order to emphasize a contrast echo component due to a contrast effect of the agent. In an ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast medium into a subject and scanning with ultrasonic waves, in order to emphasize the contrast echo component due to the contrast effect of the contrast medium An ultrasonic diagnostic apparatus, wherein the echo signal is passed through a filter having a filter characteristic obtained by inverting the transmission spectrum of the ultrasonic wave. In an ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast medium into a subject and scanning with ultrasonic waves, a filter that extracts harmonic components from the echo signal, and the extraction A high-frequency component is extracted from the detected envelope signal in order to enhance the contrast echo component due to the contrast effect of the contrast agent And an ultrasonic diagnostic apparatus. In an ultrasonic diagnostic apparatus that obtains ultrasonic information based on an echo signal obtained by injecting a contrast medium into a subject and scanning with ultrasonic waves, a filter that extracts harmonic components from the echo signal, and the extraction A circuit for generating image data from the generated harmonic component, and a filter for extracting a relatively high spatial frequency component from the image data in order to enhance a contrast echo component due to a contrast effect of the contrast agent. A characteristic ultrasonic diagnostic apparatus.

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