JPH08336527A - Ultrasonic diagnostic system - Google Patents

Abstract

PURPOSE: To provide an ultrasonic diagnostic system capable of making the diagnosis of bloodstream movement in detail by stably and efficiently receiving an echo from a contrast medium by applying fewer amount of contrast medium. CONSTITUTION: This ultrasonic diagnostic system which injects the contrast medium in an examinee and scans the cross section of the examinee with an ultrasonic wave and generates a B-mode image based on an obtained echo signal is equipped with scanning means 4, 5 and 6 which scan the cross section of the examinee by sequentially switching a scanning line as repeating the transmission/reception of the ultrasonic wave on the same scanning line at least for twice, differential means 8, 23 which differ two echo signals with respect to the same scanning line obtained by the scanning means, and a DSC 9 which produces the B-mode image based on a differential signal by the differential means.

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 capable of detecting blood flow perfusion and quantitatively evaluating the perfusion using an ultrasonic contrast agent.

[0002]

2. Description of the Related Art Ultrasound has been widely applied from a medical point of view, but its mainstream is an ultrasonic diagnostic apparatus for obtaining a tomographic image of a soft tissue of a living body by using an ultrasonic pulse reflection method. This ultrasonic diagnostic apparatus is a non-invasive examination method and displays a tomographic image of a tissue. The X-ray diagnostic apparatus, X-ray CT apparatus, MR
Compared to other diagnostic devices such as I and nuclear medicine diagnostic devices,
It has features such as real-time display, small size and low cost, high safety without exposure to X-rays, and blood flow imaging by color flow mapping. Therefore, ultrasonic diagnosis is widely performed in the heart, abdomen, mammary gland, urology, obstetrics and gynecology. In particular, you can get real-time display of heart beats and fetal movements by simply applying an ultrasonic probe from the body surface, and because it is highly safe, you can repeat tests and move to the bedside. It is convenient because it can be easily tested.

In such an ultrasonic diagnostic apparatus, for example, the blood flow dynamics are being evaluated by injecting an ultrasonic contrast agent from a vein in the examination of the heart and abdominal organs. Since the injection of the contrast medium from the vein is less invasive, the diagnosis by the evaluation method of the hemodynamics is becoming popular. In many contrast agents, microbubbles serve as a reflection source, and if the injection amount / concentration is high, the contrast effect will be large, but due to the nature of the bubbles, the ultrasonic effect shortens the contrast effect time. In recent years, long-lasting and pressure-resistant contrast agents have been developed, but it is expected that their long-term persistence in the body will increase their invasiveness.

The most basic diagnosis using a contrast agent is to know the presence or absence of blood flow at the diagnosis site by examining the presence or absence of brightness enhancement by the contrast agent. As a more advanced diagnosis, the state of the temporal distribution of the spatial distribution of the contrast agent at the diagnosis site is examined by observing the extent of the brightness change and the degree of brightness enhancement, and the contrast agent injection to the region of interest (ROI). Time to reach it and RO
Time-varying curve (TD) of echo intensity due to contrast agent in I
It is performed by obtaining C (Time Density Curve)) or maximum brightness. Then, conventionally, the change in the echo level of the ultrasonic echo caused by the contrast agent is detected simply by visually recognizing the change in the brightness level of the B-mode image, or by storing a plurality of image data in the device, and then each of the image data is stored. Quantitative measurement of echo level changes and creation of TDC have been performed by calling an image and using a histogram calculation function or the like.

A harmonic echo is considered as a method of enhancing the enhancement effect of the contrast echo by the contrast agent by the ultrasonic diagnostic apparatus. This technique utilizes the fact that the microbubbles of the contrast agent acoustically cause a nonlinear phenomenon due to its elastic action, and that the bubble echo contains a second harmonic (harmonic) component with respect to the fundamental frequency of the transmitted ultrasonic wave. It is intended to differentiate at the frequency level from the internal organs of the body that are less likely to suffer from. That is, the echo includes the fundamental frequency component of the transmitted ultrasonic wave and the harmonics component due to the contrast agent, but by removing the fundamental frequency component with the filter, only the harmonics component can be extracted. And by generating and displaying a B-mode image based on this harmonics component,
It is possible to emphasize and visualize the portion where the contrast agent is present, that is, the blood flow portion.

[0006]

There are several problems with the above-mentioned method using a contrast agent. First, the microbubbles of the contrast agent are very delicate, and they are destroyed and disappear in an extremely short time by ultrasonic irradiation. Originally, the reflection intensity of bubbles is much higher than that of scattering tissue in the living body, so the contrast effect is great even in the presence of a very small amount of micro bubbles, but in reality it disappears instantly by the irradiation of ultrasonic waves. Will end up. Therefore, in the case of diagnosis using B-mode images, it is necessary to continuously inject a very large amount of contrast medium. It can be said that the effect of enhancing the brightness by injecting the contrast agent is naturally higher as the injection amount or the concentration of the contrast agent is higher. However, increasing the injection volume will increase the invasiveness of the patient. Diagnosis by multiple injections is also highly invasive.

Next, some factors that hinder the quantitative evaluation will be described. For example, image noise is a factor on the device side,
It is conceivable that the speckle pattern may cause variations in the luminance between the local regions of the subject or the injection in the time direction, and that the factors on the contrast agent side may be the variations in the luminance due to the generation of echo scatterers and the instability of the persistence. At present, in order to avoid these factors, a method of obtaining an average result by performing a plurality of measurements can be considered.

The problems with the harmonic echo method are as follows. That is, (1) in the construction of an actual system, frequency components other than the fundamental frequency also contribute to imaging in the internal circuit of the apparatus or the ultrasonic transmission unit, and (2) subtle nonlinear development due to the propagation of ultrasonic waves. Occurs.

These problems cause unnecessary information to be added to the image of the harmonic component, which becomes a factor of reducing the enhancing effect of the contrast agent. As described above, since the ultrasonic contrast agent is disintegrated within a very short time by ultrasonic irradiation, it is difficult to capture its enhancing effect on an image. Moreover, in order to compensate for this point, a large amount of contrast medium must be continuously injected, which may cause an influence on the subject.

The present invention has been made in view of the above circumstances, and an object thereof is to stably and efficiently receive an echo from a contrast medium with a smaller amount of contrast medium administration, thereby providing more detailed blood flow dynamics. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of diagnosing.

[0011]

According to the present invention, a contrast medium is injected into a subject, and a cross section of the subject is scanned with ultrasonic waves.
In an ultrasonic diagnostic apparatus that generates a B-mode image based on the obtained echo signal, the scanning lines are sequentially switched while repeating transmission and reception of ultrasonic waves with respect to the same scanning line at least twice. Scanning means for scanning, a difference means for making a difference between two echo signals relating to the same scanning line obtained by the scanning means, and a generating means for generating the B-mode image based on the difference signal by the difference means. To have.

[0012]

According to this embodiment, ultrasonic waves are transmitted and received at least twice for the same scanning line. When the contrast agent is irradiated with ultrasonic waves, all or part of the contrast agent disappears. Therefore,
The amount of the contrast agent present in the first transmission / reception with respect to the same scanning line is certainly reduced in the second and subsequent times. In other words, the reflection component from the contrast agent included in the echo signals by the second and subsequent transmissions is reliably reduced with respect to the reflection component from the contrast agent included in the echo signals by the first transmission and reception. On the other hand, the reflection components from tissues other than the contrast agent do not change significantly between the first and second times. Therefore, the difference signal that is the difference between the echo signals of the first transmission and reception and the echo signals of the second and subsequent transmissions reflects the lost contrast agent, and a B-mode image is generated based on such a difference signal. By doing so, it becomes possible to image only the distribution of the contrast agent, that is, the blood flow dynamics. As described above, the present invention positively utilizes the negative property that the contrast agent is easily disintegrated, and emphasizes the contrast effect. Further, in the present invention, it is possible to cancel the use of a dangerous and highly invasive contrast agent that is persistent and pressure resistant in the body.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the case of observing the state of blood flow to the myocardium, but the case of identifying an abnormal site from the state of blood flow to the heart, particularly the muscles of the left ventricle, will be described below.

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to this embodiment. The ultrasonic diagnostic apparatus according to this embodiment includes an electrocardiograph (ECG) 1, an ultrasonic probe 4, an apparatus main body 22,
Connected to the device main body 22 and various instructions from the operator
It is composed of an operation panel 15 for incorporating commands and information into the apparatus main body 22. The operation panel 15 is provided with a mouse 13, a trackball 14, a mode changeover switch 16, etc. for setting a region of interest (ROI).

The ultrasonic probe 4 has a piezoelectric vibrator as an acoustic / electric reversible conversion element such as a piezoelectric ceramic. A plurality of piezoelectric vibrators are arranged in parallel and mounted on the tip of the probe 4.

The apparatus main body 22 is constructed as follows with the CPU 17 as a control center of the entire system. An ultrasonic wave transmitter 6 and an ultrasonic wave receiver 5 are connected to the probe 4. The ultrasonic transmitter 6 has a pulse generator 6A, a transmission delay circuit 6B, and a pulser 6C. The pulse generator 6A has, for example, a rate frequency fr of 5 KHz (cycle: 1 / fr second).
The rate pulse is repeatedly generated at. This rate pulse is distributed to the number of channels and sent to the transmission delay circuit 6B. The transmission delay circuit 6B focuses each ultrasonic wave into a beam and gives each rate pulse a delay time necessary for determining the transmission directivity. A trigger from the trigger signal generator 19 is supplied to the transmission delay circuit 6B as a timing signal via the timing signal generator 18. The pulser 6C applies a voltage pulse to the probe 4 for each channel at the timing when the rate pulse is received from the transmission delay circuit 6B. Thereby, the ultrasonic beam is transmitted to the subject.

The reflected wave reflected by the acoustic impedance discontinuity in the subject is received by the probe 4. The echo signal output from the probe 4 for each channel is captured by the ultrasonic wave reception unit 5. The ultrasonic wave reception unit 5 includes a preamplifier 5A, a reception delay circuit 5B, and an adder 5C. The echo signal is amplified by the preamplifier 5A for each channel,
The delay time required for determining the reception directivity is given by the reception delay circuit 5B, and then added by the adder 5C. By this addition, the reflection component from the direction corresponding to the reception directivity is emphasized. The total directivity of ultrasonic wave transmission / reception is determined by the transmission directivity and the reception directivity. This directivity is called a scanning line.

The echo signal output from the ultrasonic wave receiving unit 5 is transmitted to the receiver unit 7 and the color flow mapping (CF).
M) is sent to the unit 20. Although not shown, the receiver unit 7 is composed of a logarithmic amplifier, an envelope detection circuit, and an analog / digital converter (A / D). The logarithmic amplifier logarithmically amplifies the echo signal. The envelope detection circuit detects the envelope of the output signal from the logarithmic amplifier. This detection signal is digitized through an analog-digital converter and output as detection data.

This detected data is sent directly to the adder 23, and is also sent to the adder 23 after being delayed by the rate period 1 / fr seconds via the line memory 8. Line memory 8
Has memory elements for the number of sampling points on one scanning line. The adder 23 takes a difference between the detection data supplied synchronously from the receiver section 7 and the line memory. This difference data is the B-mode digital scan converter (D
It is sent to the display unit 11 via the (SC) unit 9 and the memory synthesis unit 10, and is visually displayed as a spatial distribution of the contrast agent, that is, a blood flow image. B mode frame memory 12
Are provided to store the output of the B-mode DSC unit 9. The difference calculation process by the adder 23 means that the brightness difference after logarithmic compression is taken, but the line memory 8 may be arranged immediately before the receiver unit 7 to take the difference between linear signals before logarithmic compression.

Although not shown, the CFM unit 20 is composed of a phase detection circuit, an analog-digital converter, an MTI filter, an autocorrelator, and a calculation unit, extracts a blood flow component due to the Doppler effect, average velocity, dispersion, power, etc. Blood flow information of is obtained for multiple points. The blood flow information is sent to the display unit 11 via the memory synthesizing unit 10 and displayed in color as an average velocity image, a dispersion image, a power image, and a combined image of these.

The electrocardiographic waveform signal detected by the electrocardiograph 1 is sent to the reference data memory 3 via the amplifier 2 and, if necessary, to the display unit 11 via the memory synthesizing unit 10 to obtain the electrocardiographic waveform. Is displayed as.

Next, the operation of this embodiment will be described. Micro bubbles are used as the contrast agent. FIG. 2 is an explanatory diagram regarding a scanning procedure by delay control by the ultrasonic wave transmission unit 6 and the ultrasonic wave reception unit 5. As shown in FIG. 2A, it is assumed that one frame of the scan area includes 120 scanning lines, and each scanning line is represented by symbols R1, R2, R3, ..., R119, R120 according to the scanning order. Shall be identified. As shown in FIG. 2B, the ultrasonic beam is repeatedly transmitted to the subject at a rate period of 1 / fr seconds, and the reflected wave is received until the next transmission. In this embodiment, every time ultrasonic wave transmission / reception is repeated twice for the same scanning line,
The scanning lines are sequentially switched. By performing such an operation from the first scanning line R1 to the last scanning line R120, scanning for one frame is completed. Such a scan for one frame is repeated.

According to such a scanning procedure, the adder 23 is supplied with the detection data of the echo signal by the first transmission / reception and the detection data of the echo signal by the second transmission / reception for the same point in synchronization. . Both detection data are subtracted, whereby the reflection component from the biological tissue is removed and only the reflection component from the contrast agent is extracted. This principle will be described below.

FIG. 3 is a schematic view of the reflection phenomenon caused by the first transmission / reception and the second transmission / reception for each of the contrast agent and the living tissue. As shown in FIGS. 3A and 3B, the ultrasonic wave transmitted at the first time is reflected by the contrast agent (microbubbles) and the biological tissue, and is received by the probe 4. The microbubbles, which are contrast agents, collapse or disappear entirely or partially when they are irradiated with ultrasonic waves, depending on the transmission power of the ultrasonic waves. That is, 1
All or part of the contrast agent is disintegrated / disappeared by the second transmission / reception. When the second transmission / reception is performed on the same scanning line in this state, naturally, the collapsed contrast agent does not reflect, as shown in FIG. On the other hand, as shown in FIG. 3D, the reflected wave is received with respect to the biological tissue as in the first time.

Since all or part of the contrast agent is destroyed in the first transmission / reception as described above, the amount of the contrast agent in the second transmission surely decreases with respect to the existing amount of the contrast agent in the first transmission / reception. In other words, the reflection component from the contrast agent included in the echo signal by the second transmission and reception is surely reduced with respect to the reflection component from the contrast agent included in the echo signal by the first transmission and reception. On the other hand, the reflection components from tissues other than the contrast agent do not change significantly between the first and second times.

Therefore, the difference data obtained by subtracting the echo signal (detection data) from the second transmission and reception from the echo signal (detection data) from the first transmission and reception reflects only the disappeared contrast agent. By generating a B-mode image based on such difference data, it is possible to image only the distribution of the contrast agent, that is, the blood flow dynamics. As described above, in this embodiment, the contrast effect is emphasized by positively utilizing the negative property that the contrast agent is easily disintegrated. Further, in this embodiment, the use of a dangerous and highly invasive and dangerous contrast agent inside the body can be canceled.

The present embodiment can be modified as follows. From the principle described above, the larger the difference between the amount of the contrast agent present during the first transmission / reception and the amount of the contrast agent present during the second transmission / reception, that is, collapse / disappear in the first transmission / reception. The more the contrast agent is, the more the contrast effect can be emphasized. Therefore, for the same scan line, n (n ≧
The contrast effect can be enhanced by repeating 3) times, for example, three times of ultrasonic wave transmission, and obtaining the difference between the first echo signal and the third echo signal. In this case, the first detection data is stored in the line memory 8 and only the transmission is performed and the reception is not performed until the third time, and the difference between the first detection data and the third detection data may be performed. . In addition,
In this case, it is preferable that the transmission power of the ultrasonic wave transmitted for the second time be sufficiently large so that most of the contrast agent is destroyed.

Another modification will be described. The configuration of this modification is shown in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals. In this modification, the difference is taken for each channel of the echo signal before the addition processing of the adder 5C and after the reception delay processing of the reception delay circuit 5B. The echo signals after the difference are added by the adder 5C. It should be noted that it means the difference between single-channel linear echo signals.

Still another modification will be described. The configuration of this modification is shown in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals. In this modification, a path in which the detection data from the receiver unit 7 is directly supplied to the DSC 9 is added.
This makes it possible to simultaneously display the image in which the contrast effect based on the difference data from the adder 23 is emphasized and the normal B-mode image output from the receiver unit 7. In this case, if the color tone of one of the two images that are normally displayed in gray scale is different from the other, it is possible to simultaneously observe the conventional B-mode image and the image in which the contrast effect is emphasized. .

[0030]

The present invention provides an ultrasonic diagnostic apparatus for injecting a contrast medium into a subject, scanning a cross section of the subject with ultrasonic waves, and generating a B-mode image based on the obtained echo signal. Scanning means for scanning the cross section of the subject by sequentially switching scanning lines while repeating transmission and reception of ultrasonic waves at least twice with respect to the same scanning line;
It comprises a difference means for making a difference between two echo signals obtained by the scanning means for the same scanning line, and a generating means for generating the B-mode image based on the difference signal by the difference means.

According to this embodiment, ultrasonic waves are transmitted and received at least twice for the same scanning line. When the contrast agent is irradiated with ultrasonic waves, all or part of the contrast agent disappears. Therefore, with respect to the amount of the contrast agent present at the time of the first transmission / reception with respect to the same scanning line, that of the second time and thereafter is certainly reduced. In other words, the reflection component from the contrast agent included in the echo signals by the second and subsequent transmissions is reliably reduced with respect to the reflection component from the contrast agent included in the echo signals by the first transmission and reception. On the other hand, the reflection components from tissues other than the contrast agent do not change significantly between the first and second times. Therefore, the difference signal that is the difference between the echo signals of the first transmission and reception and the echo signals of the second and subsequent transmissions reflects the lost contrast agent, and a B-mode image is generated based on such a difference signal. By doing so, it becomes possible to image only the distribution of the contrast agent, that is, the blood flow dynamics. Thus, the present invention is
The contrast effect is easily disintegrated, and the negative effect of the contrast agent is actively utilized to emphasize the contrast effect. Further, in the present invention, it is possible to cancel the use of a dangerous and highly invasive contrast agent that is persistent and pressure resistant in the body.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a scan procedure.

FIG. 3 is a schematic view of the reflection phenomenon caused by the first transmission / reception and the second transmission / reception with respect to each of the contrast agent and the biological tissue.

FIG. 4 is a block diagram of a modified example.

FIG. 5 is a block diagram of another modification.

[Explanation of symbols]

1 ... Electrocardiograph, 2 ... Amplifier, 3 ... Reference data memory, 4 ... Ultrasonic probe, 5 ... Ultrasonic receiving part, 6 ... Ultrasonic transmitting part, 7 ... Receiver part,
8 ... Line memory, 9 ... DSC, 1
0 ... Memory synthesis section, 11 ... Display section, 12 ...
Frame memory, 13 ... Mouse, 14 ... Trackball, 15 ... Operation panel, 16 ... Mode changeover switch, 17 ... CPU, 18 ... Timing signal generator, 19 ... Trigger generator, 20
... CFM unit, 21 ... TDC operation unit, 22 ...
Device body, 23 ... Adder.

Claims (3)

[Claims] 1. An ultrasonic diagnostic apparatus in which a contrast medium is injected into a subject, a cross section of the subject is ultrasonically scanned, and a B-mode image is generated based on the obtained echo signal. On the other hand, a scanning unit that scans the cross section of the subject by sequentially switching the scanning lines while repeating transmission and reception of ultrasonic waves at least twice, and two echo signals related to the same scanning line obtained by the scanning unit. An ultrasonic diagnostic apparatus comprising: a difference unit that makes a difference and a generation unit that generates the B-mode image based on a difference signal from the difference unit. 2. The difference means is 1 for the same scanning line.
2. The ultrasonic diagnostic apparatus according to claim 1, wherein an echo signal obtained by the transmission and reception of the first time and an echo signal obtained by the transmission and reception of the nth time (n ≧ 2) after the contrast agent is collapsed are differentiated. 3. The scanning means repeats transmission and reception of ultrasonic waves twice with respect to the same scanning line, and transmits ultrasonic pulses with a power required to destroy the contrast agent between the two transmissions and receptions. The ultrasonic diagnostic apparatus according to claim 1, wherein: