JP4820494B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus suitable for diagnosing by injecting an ultrasonic contrast agent into a subject.
[0002]
[Prior art]
An ultrasound diagnostic apparatus transmits and receives ultrasound with a subject via an ultrasound probe, and based on a received signal including a reflected wave from a tissue, that is, a reflected echo signal, an ultrasound diagnostic image Information useful for diagnosis such as the above is obtained.
[0003]
For example, an ultrasonic beam can be sequentially transmitted while scanning the subject, and an image such as a tomographic image can be generated based on a reflected echo signal composed of the reflected wave. That is, by determining the pixel position corresponding to the reflected echo signal based on the transmission direction and the round-trip propagation time, and determining the luminance of the pixel based on the intensity of the reflected echo signal corrected for attenuation due to the propagation distance, A two-dimensional or three-dimensional gray image can be generated. Such an image generation method is generally called a B mode (abbreviation of Brightness Mode) and is widely used.
[0004]
By the way, the ultrasonic beam is formed by generating ultrasonic waves from a plurality of transducers arranged in parallel with the subject, and the direction in which the wave fronts from the transducers coincide is the direction of the ultrasonic beam. In order to improve the resolution of a desired detection depth, a transmission focus process is also known in which an ultrasonic beam is narrowed by a set depth by shifting the operation timing of each transducer.
[0005]
In addition, it has been proposed to perform diagnosis by injecting an ultrasonic contrast agent into a subject and enhancing the contrast of the image. An ultrasonic contrast agent is a solution in which fine bubbles are mixed in a solution, and is also referred to as a contrast agent. When this bubble receives an ultrasonic wave, it emits a specific sound wave. As a result, a strong reflected echo signal is detected from a portion of the subject containing the ultrasonic contrast agent. For example, when diagnosis is performed by injecting an ultrasound contrast agent into blood, the contrast of a portion having blood flow can be emphasized and displayed as an image.
[0006]
[Problems to be solved by the invention]
However, in the prior art, when the transmission focus process is performed, the contrast effect of the ultrasound contrast agent becomes uneven with respect to the depth. In other words, since the sound pressure of the ultrasonic beam increases near the focus depth, bubbles are more likely to be broken or deformed near the focus depth than other portions. Therefore, a large sound pressure acts on each bubble near the focus depth, and as a result a large echo signal is generated, so even if the bubbles are evenly distributed, the reflected echo signal is stronger than the other parts. The part is displayed as an image with a strong contrast. If the contrast of the image is different from the actual concentration distribution of the contrast agent, for example, when diagnosing the blood flow state of the myocardium, the region far from the focus depth is displayed with a weak contrast. However, it may be mistaken for an ischemic state.
[0007]
In view of such a problem, an object of the present invention is to make the contrast effect of an ultrasound contrast agent uniform when a transmission focus process is performed to generate an ultrasound diagnostic image.
[0008]
[Means for Solving the Problems]
The present invention relates to a signal and an ultrasonic probe for transmitting and receiving ultrasonic waves to a subject, driving means for driving the drive signal is focused ultrasonic probe, the signal received by the ultrasonic probe A signal processing means for processing, an image converting means for converting the received signal signal-processed by the signal processing means into an image, and a display means for displaying an image of a subject including a blood vessel into which an ultrasound contrast agent has been injected. The target is an ultrasonic diagnostic apparatus. The image conversion means is configured to apply a correction coefficient set in advance to the received received signal to correct the intensity of the received signal and convert it to an image. The correction coefficient is a focus point of the subject. The above-described object is achieved by setting according to the depth .
[0009]
According to the present invention, the correction coefficient such as the luminance of a pixel can be set so that the intensity of the received signal is corrected according to the focus point depth and the contrast effect of the ultrasonic contrast agent becomes uniform. The correction of the received signal or the setting of the correction coefficient may be performed according to the set focus depth of the transmission focus process.
[0010]
This makes it possible to set a correction coefficient that lowers the intensity of the ultrasonic signal, that is, the intensity of the received signal from the set focus point depth at which the sound pressure is high, or the intensity of the received signal from other parts. By setting the value relatively high, the contrast effect of the ultrasound contrast agent can be made uniform even when the transmission focus process is performed, and the luminance distribution of the image can be brought close to the actual distribution amount of the ultrasound contrast agent.
[0011]
The correction amount of the reflected echo signal according to the focus point depth of such a detection site may be determined based on an experiment using an ultrasonic phantom. For example, a correlation curve between the focus point depth when the transmission focus process is performed and the intensity of the ultrasonic signal in the subject may be obtained by experiment, and the correction amount may be set based on this. As a parameter representing the intensity of such an ultrasonic signal, for example, a sound pressure such as a mechanical index (MI) can be used. Further, the correction amount may be determined based on a theoretical formula instead of an experiment. In these cases, the setting means for setting the correction coefficient may include a correction table in which a correction amount data string corresponding to the focus point depth of the detection site is accumulated.
[0012]
The correction amount of the reflected echo signal may be variably set according to the set focus depth. For example, the correction amount corresponding to each of the plurality of focus depths or the correlation between the reflected echo signal and the signal intensity parameter may be set in advance, and the set focus depth may be set at an interval between these preset focus depths. When set, the correction amount of the focus depth sandwiching this may be used to obtain the correction amount by the interpolating process.
[0013]
Incidentally, the relationship between the above-described depth and the intensity of the ultrasonic signal in the subject depends not only on the focus depth but also on the subject. For example, the intensity distribution of the ultrasound signal in the subject may differ even if ultrasound is transmitted in the same manner due to differences in physique, subcutaneous fat mass, body fat percentage, sex, and the like. Therefore, the setting means may include a means for variably setting the correction amount of the reflected echo signal or the correlation between the reflected echo signal and the signal intensity parameter.
[0014]
In addition, when a plurality of types of ultrasonic probes are provided and are used by switching, the relationship between the depth and the intensity of the ultrasonic signal may differ depending on the ultrasonic probe used. Therefore, the correction unit may variably set the correction amount of the pixel intensity according to the ultrasonic probe to be used.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an ultrasonic diagnostic apparatus to which the present invention is applied will be described. FIG. 1 is a diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to the present embodiment. The ultrasonic diagnostic apparatus includes a probe 1, a transmitter 3 that drives the probe 1 and transmits an ultrasonic beam to a subject (not shown), and a reflected echo received by the probe 1. A receiving unit 5 that is a signal processing unit that processes a signal, that is, a received signal, an image generating unit 7 that is an image converting unit that converts the received signal that has been signal-processed into an image and generates an ultrasound diagnostic image, And an image display unit 9 for displaying an image output from the image generation unit 7. In addition, a control device 11 that controls the ultrasonic diagnostic apparatus is provided, and the control device 11 is connected to the transmission unit 3, the reception unit 5, the image generation unit 7, and the image display unit 9, respectively. An input unit 13 is connected to the control device 11.
[0016]
The image generation unit 7 includes a correction unit 15 that corrects the signal intensity of the reception signal output from the reception unit 5, and a digital scan converter (DSC) that scan-converts the corrected reception signal output from the correction unit 15. ) 17. The correction unit 15 includes a line memory 19 that temporarily stores a received signal, a correction coefficient table 21 that accumulates correction coefficients, and a multiplier 23 that multiplies the received signal and the correction coefficient. The DSC 17 also includes a frame memory 25 that stores the received signal after correction.
[0017]
The input unit 13 includes an operation panel 27 having an input device such as operation keys, a panel interface 29 that recognizes an operation performed by the operation panel 27, and an operation command or the like according to the recognition of the panel interface 29. And a panel controller 31 for transmission to the network.
[0018]
Hereinafter, the operation and detailed configuration of the ultrasonic diagnostic apparatus of the present embodiment will be described by taking as an example a case where a tomographic image of a subject into which an ultrasonic contrast agent has been injected is generated. First, the transmission unit 3 transmits an ultrasonic beam to a subject (not shown) via the probe 1 in response to an instruction from the control device 11. The probe 1 has a plurality of transducers (not shown) arranged in parallel to face the subject, and the transmission unit 3 gives drive signals to the individual transducers. As a result, ultrasonic signals are generated from the individual transducers, and an ultrasonic beam that apparently travels in a direction in which the wavefronts of the ultrasonic waves from the transducers coincide is generated. The transmission unit 3 also performs a known transmission focus process. The transmission focus process is to reduce the sound field by narrowing the ultrasonic beam at a set depth by shifting the operation timing of each transducer. For example, when the vibrators are arranged in a line, the operation timing at both ends is the first, and is realized by gradually delaying as approaching the center. Further, by changing the delay time, the focus depth at which the ultrasonic beam is most focused can be variably set. In the ultrasonic diagnostic apparatus of the present embodiment, the focus depth can be variably set by the operator operating the scanning panel 27. The input from the operation panel 27 is transmitted to the control device 11 via the panel interface 29 and the panel controller 31, and the control device 11 that receives the input transmits the ultrasonic beam having the set focus depth to the transmission unit 3. Instruct.
[0019]
Then, the ultrasonic beam transmitted from the probe 1 propagates through the subject and is partially reflected when passing through a location where the acoustic impedance changes, such as a tissue boundary. Further, when the ultrasound contrast agent injected into the subject receives the ultrasound beam, the ultrasound contrast agent generates a specific sound wave. Incidentally, an ultrasonic contrast agent is a solution in which fine bubbles are mixed in a solution, and sound waves are generated by the destruction and deformation of bubbles.
[0020]
Next, the receiving unit 5 receives a received signal including a reflected wave from the tissue and a sound wave generated by the ultrasonic contrast agent via the probe 1. The received signals received as the ultrasonic signals are converted into electrical signals by the individual transducers, and the received signals output by the transducers are phased by the receiving unit 5, added, and output.
[0021]
Such transmission of an ultrasonic beam and reception of a received signal accompanying this transmission are sequentially performed while scanning the subject. Then, the image generation unit 7 generates a tomographic image of the subject based on a series of received signals related to this scanning. That is, the received signal corresponding to each ultrasonic beam is a data string composed of a time-series signal intensity, that is, an amplitude with respect to the round-trip propagation time from when the ultrasonic beam is transmitted until the received signal is received. Since the round-trip propagation time is proportional to the depth from the probe to the portion related to the received signal, the pixel position can be determined based on the transmission direction of the ultrasonic beam and the round-trip propagation time. A gray image can be generated by determining the luminance of the pixel based on the amplitude of the received signal.
[0022]
The received signal output from the receiving unit 5 is input to the image generating unit 7 and stored in the line memory 19 of the correcting unit 15. Then, the ultrasonic diagnostic apparatus of this embodiment reads the correction coefficient corresponding to the received signal from the correction coefficient table 21, and the multiplier 23 receives the corrected reception obtained by multiplying the amplitude of the received signal by the correction coefficient. An image is generated based on a wave signal, that is, a signal intensity parameter.
[0023]
Hereinafter, the features of this embodiment will be described in detail. FIG. 2 is a diagram comparing a schematic diagram showing an ultrasonic diagnostic image of a cross section of the apex of the heart with a graph showing changes in the mechanical index (MI) in the depth direction of the subject. Incidentally, MI is a value obtained by normalizing the maximum peak negative sound pressure on the sound axis with a reference sound pressure of 1 MPa, and is used as a parameter representing the intensity of the ultrasonic signal in the subject. As shown in FIG. 2, the ultrasound diagnostic image 33 has a fan-shaped field of view 35 formed by scanning the subject while changing the beam line 34 of the ultrasound beam. It is displayed in this visual field 35. The focus depth is set to the position of the focus point marker 39 shown on the screen. In this case, as shown in FIG. 2, the MI 41 of the ultrasonic beam in the subject gradually increases from the probe to the focus depth, takes a maximum value near the focus depth, and then attenuates.
[0024]
FIG. 3 is a graph comparing the MI distribution in the depth direction of the subject, the concentration distribution of the bubbles of the ultrasonic contrast agent, and the signal intensity distribution of the received signal in this case. As described above, MI has a distribution having a peak near the focus depth. Therefore, as shown in FIG. 3, even if the concentration 43 of the bubbles of the ultrasonic contrast agent is substantially uniform, the bubbles are not observed where MI is large. Strong sound waves are generated that are easily broken and deformed. As a result, the intensity 45 of the obtained received signal gradually increases from the probe to the vicinity of the focus depth, similarly to MI 41, and attenuates after reaching the maximum value near the focus depth. Therefore, when the pixel intensity of the ultrasonic diagnostic image is determined in accordance with the intensity 45 of the received signal, the focus depth is not shown on the image even though the bubbles are actually distributed substantially uniformly. The vicinity is emphasized and an image is displayed, and a uniform contrast effect cannot be obtained.
[0025]
Therefore, the ultrasonic diagnostic apparatus of the present embodiment is based on the signal intensity parameter obtained by correcting the received signal intensity by applying a correction coefficient corresponding to the focus depth based on the depth. The pixel intensity is determined. FIG. 4 is a graph comparing the MI in the depth direction of the subject, the bubble concentration of the ultrasonic contrast agent, the correction coefficient, and the graph showing the corrected signal intensity. In the ultrasonic diagnostic apparatus according to the present embodiment, the correction coefficient is stored in the correction coefficient table 21 stored in the memory as a series of data strings corresponding to the depth. When the received signal output from the receiving unit 5 is input to the line memory 19, a correction coefficient corresponding to the depth of the received signal based on the depth address attached to the received signal based on the round-trip propagation time. Are read from the correction coefficient table 21. The correction coefficient is input to the multiplier 23, and the multiplier 23 inputs a value obtained by multiplying the amplitude of the received signal and the correction coefficient, that is, the corrected received signal to the frame memory 25 of the DSC 17. The received wave signal after correction stored in the frame memory 25 is scanned and read, and is displayed by the image display unit 9 having a display device such as a CRT or LCD. At this time, the luminance of the pixel is determined based on the amplitude of the corresponding received signal.
[0026]
As shown in FIG. 4, the correction coefficient 47 relatively weakens a received signal having a depth with a large MI, such as a focus depth, and relatively strengthened a received signal having a depth with a small MI. Is set. The correction coefficient 47 is a distribution in which the intensity distribution of the received signal 49 after correction shows a curve substantially similar to the concentration distribution of the ultrasonic contrast agent when a series of received signals having different depths are corrected. It is set to be.
[0027]
In the case of this embodiment, such a correction coefficient is set based on an experimental result using an ultrasonic phantom. Ultrasonic phantoms are widely used for calibration and evaluation of ultrasonic diagnostic equipment and probes. Generally, a material having sound velocity characteristics and attenuation coefficient substantially equivalent to those of soft tissues of a living body is enclosed in a case. It is configured. When setting a correction coefficient corresponding to a desired focus depth, an ultrasonic beam having the focus depth is transmitted to the ultrasonic phantom, and MI in the phantom is measured at a plurality of locations while changing the measurement depth. Thereby, the MI distribution in the depth direction as shown in FIG. 4 is obtained. Then, the correction coefficient is set so that the received signals from the respective depths with respect to the measured MI distribution are made uniform when it is assumed that the ultrasonic contrast agent is uniformly distributed.
[0028]
The ultrasonic diagnostic apparatus of the present embodiment accumulates correction coefficients corresponding to a plurality of focus depths in the correction coefficient table 21, and switches them according to the focus depth at the time of diagnosis. Further, in the case of the focus depth for which the correction coefficient is not set in advance, the correction coefficient is obtained by insertion based on the preset correction coefficient having the closest focus depth.
[0029]
The MI distribution in the depth direction also depends on the subject. That is, even if an ultrasonic beam is transmitted from the probe 1 in the same manner, the MI distribution in the subject may differ depending on the subject's physique, subcutaneous fat mass, fat ratio, sex, and the like. Therefore, the correction coefficient table 21 has various correction coefficients corresponding to the characteristics of the subject, and can be switched according to the input from the operation panel 10. Further, since the MI distribution in the depth direction also depends on the type of the probe 1, correction coefficients corresponding to the various probes 1 are also stored in the correction coefficient table 21, which is also input from the operation panel 10. Or the type of the probe 1 is automatically detected and switched.
[0030]
Hereinafter, effects obtained by the ultrasonic diagnostic apparatus of the present embodiment will be described. According to the ultrasonic diagnostic apparatus of this embodiment, the intensity of the received signal near the set focus depth where the signal intensity of the ultrasonic beam is large is relatively lowered, and the intensity of the received signal of other parts is relatively decreased. Therefore, even if transmission focus processing is performed, the contrast effect of the ultrasound contrast agent can be made uniform, and the luminance distribution of the image can be brought close to the actual distribution amount of the ultrasound contrast agent.
[0031]
FIG. 5 is a schematic diagram showing a cardiac apex two-chamber cross-sectional image obtained by the ultrasonic diagnostic apparatus of the present embodiment, and a diagram showing a luminance distribution of the pixel. FIG. 6 is a schematic diagram showing the apical two-chamber cross-sectional image when correction is not performed, and a diagram showing the luminance distribution of the pixel. When transmission focus processing is performed and correction is not performed, the MI distribution in the depth direction is non-uniform. Therefore, even if the ultrasound contrast agent is distributed substantially uniformly in the myocardium, the image is shown in FIG. As shown, the vicinity of the focus depth is highlighted. For this reason, an ultrasonic contrast agent far from the focus depth exhibits only a relatively weak contrast effect, and as a result, an image is displayed with a weak contrast, which may be mistaken for an ischemic state. On the other hand, when the correction according to the feature of the present embodiment is performed, the contrast effect of the ultrasound contrast agent is made uniform, and as a result, a uniform contrast image as shown in FIG. 5 can be obtained. There is an effect that an ischemic state and the like can be appropriately diagnosed.
[0032]
Further, since the correction coefficient is switched to an appropriate one according to the focus depth, the characteristics of the subject, and the type of the probe, a suitable diagnostic image can be obtained in various diagnostic situations.
[0033]
Although the present embodiment has been described by taking as an example the case of generating a two-dimensional B-mode tomographic image, the present invention can also be applied to the case of generating a three-dimensional image.
[0034]
In the present embodiment, the correction coefficient is set based on an experiment using an ultrasonic phantom. However, the correction coefficient may be set based on a theoretical formula.
[0035]
In addition, a known attenuation correction unit that corrects the attenuation amount with respect to the propagation distance of ultrasonic waves by a logarithmic amplifier or the like may be used together with the correction unit as in this embodiment. In this case, a parameter such as a correction coefficient may be set so that the contrast effect of the ultrasonic contrast agent is uniformized in the received signal input to the frame memory through both corrections.
[0036]
In this embodiment, correction is performed by multiplying the correction coefficient by the intensity of the received signal. However, correction may be performed by addition / subtraction.
[0037]
【The invention's effect】
According to the present invention, it is possible to make the contrast effect of the ultrasound contrast agent uniform when performing transmission focus processing to generate an ultrasound diagnostic image.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment of an ultrasonic diagnostic apparatus to which the present invention is applied.
FIG. 2 is a diagram comparing a schematic diagram showing an ultrasonic diagnostic image of a two-chamber section of the apex of the heart with a graph showing a change in MI in the depth direction of the subject.
FIG. 3 is a graph comparing graphs showing MI in the depth direction of a subject, the concentration of bubbles of an ultrasonic contrast agent, and the signal intensity of a received signal.
FIG. 4 is a diagram comparing graphs showing MI in the depth direction of a subject, the concentration of bubbles of an ultrasonic contrast agent, a correction coefficient, and a signal intensity after correction.
FIG. 5 is a schematic diagram showing a two-chamber apex image obtained by the ultrasonic diagnostic apparatus of FIG. 1, and a diagram showing a pixel luminance distribution thereof;
FIGS. 6A and 6B are a schematic diagram showing a two-chamber apical section image when no correction is performed, and a diagram showing a pixel luminance distribution thereof. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Probe 3 Transmission part 5 Reception part 7 Image generation part 9 Image display part 11 Control apparatus 13 Input part 15 Correction | amendment part 17 DSC

Claims (7)

An ultrasonic probe that transmits / receives ultrasonic waves to / from a subject, a driving unit that drives the ultrasonic probe with a focused driving signal, and a signal that processes a signal received by the ultrasonic probe Processing means, image conversion means for converting the received signal signal-processed by the signal processing means into an image, and display means for displaying an image of the subject including a blood vessel into which an ultrasound contrast agent has been injected. An ultrasound diagnostic apparatus,
The image converting means is configured to correct the intensity of the received signal by applying a preset correction coefficient to the received received signal and convert it to an image,
The ultrasonic diagnostic apparatus, wherein the correction coefficient is set according to a focus point depth of the subject and according to a size of a mechanical index . An ultrasonic probe that transmits / receives ultrasonic waves to / from a subject, a driving unit that drives the ultrasonic probe with a focused driving signal, and a signal that processes a signal received by the ultrasonic probe Processing means, image conversion means for converting the received signal signal-processed by the signal processing means into an image, and display means for displaying an image of the subject including a blood vessel into which an ultrasound contrast agent has been injected. An ultrasound diagnostic apparatus,
  The image converting means is configured to correct the intensity of the received signal by applying a preset correction coefficient to the received received signal and convert it to an image,
  The correction coefficient is set according to the focus point depth of the subject and so that the intensity distribution of the received signal after correction becomes a curve distribution substantially similar to the concentration distribution of the ultrasound contrast agent. An ultrasonic diagnostic apparatus characterized by the above. The image conversion means applies the correction coefficient set in advance according to the focus point depth and the depth of each pixel to the received signal of each pixel based on the received received signal. Is configured to correct the intensity of the image and convert it to an image,
The correction factor is, according to claim 1 or 2, characterized in that it is set the strength of the received signals of the respective pixels based on the intensity of the received signal at the focus point depth to relatively high An ultrasonic diagnostic apparatus according to 1. The ultrasonic probe is provided in a plurality of types and used individually,
The correction factor is the ultrasound diagnostic apparatus according to any one of claims 1 to 3, characterized in that which is set according to the ultrasonic probe to be used. The correction factor is, ultrasound according to any one of claims 1 to 3, characterized in that it is set based on the correlation between the intensity of the received signal of the focus point depth and within the subject Diagnostic device. The correction factor is the ultrasound diagnostic apparatus according to any one of claims 1 to 3, characterized in that it is set for different the focus point depth. Input means for inputting at least one of the physique of the subject, subcutaneous fat mass, body fat percentage, and sex;
The ultrasonic diagnostic apparatus according to claim 6 , wherein the correction coefficient is switched in response to an input from the input unit.

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