JP5490609B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic transmission technique.

  As a technique related to an ultrasonic diagnostic apparatus, for example, as described in Patent Document 1, an image forming technique using a contrast agent is known. In this technique, the contrast agent is imaged using a harmonic component obtained from bubbles contained in the contrast agent, thereby forming a contrast image that reflects, for example, a blood vessel to which the contrast agent is administered. However, although the bubble contained in the contrast agent is mainly displayed in the contrast image, the surrounding tissue or the like is not reflected, and therefore it may be difficult to determine in which part of the tissue the bubble is present.

  Therefore, a device that forms a fundamental image using the fundamental wave component included in the received signal together with the contrast image, and combines and displays the fundamental image showing the surrounding tissue and the contrast image showing the bubble is displayed. . When forming a fundamental image, it is desirable not to destroy the bubble as much as possible or to detect the bubble as much as possible.

  If the strength of the transmission signal (transmission sound pressure) is reduced, bubble destruction and detection can be suppressed. However, the received signal obtained from the tissue becomes small. Of course, if the transmission sound pressure is increased, bubble destruction and detection will be caused.

  Thus, it has been difficult to obtain a good fundamental image simply by adjusting the transmission sound pressure. Incidentally, Patent Document 2 describes a technique for adjusting the waveform of an elastic pulse, although it is not a technique related to an ultrasonic diagnostic apparatus or a bubble.

JP 2009-136626 A Japanese Patent No. 2578638

  Under such circumstances, the inventors of the present application have been researching and developing ultrasonic imaging technology using bubbles. In particular, research and development have been repeated focusing on the interaction between ultrasonic waves and bubbles.

  The present invention has been made in the course of research and development, and an object thereof is to realize an ultrasonic transmission technique that suppresses bubble destruction and detection.

  A suitable ultrasonic diagnostic apparatus that meets the above-mentioned purpose is to transmit ultrasonic waves with a probe that transmits and receives ultrasonic waves to and from a diagnostic region including bubbles, and a modified transmission waveform in which the negative side amplitude is smaller than the positive side amplitude. A transmission control unit that controls the probe, a reception processing unit that obtains a reception signal corresponding to the ultrasonic wave received by the probe, and an image forming unit that forms an ultrasonic image based on the reception signal It is characterized by that.

  In a desirable specific example, a waveform adjustment unit that adjusts the magnitude of the negative side amplitude of the modified transmission waveform, and a reception signal obtained by using the modified transmission waveform according to an amplitude adjustment amount in the waveform adjustment unit And a gain adjusting unit that adjusts the gain of.

  In a preferred embodiment, the transmission control unit controls the probe using a normal transmission waveform in which a positive side amplitude and a negative side amplitude are substantially equal and the modified transmission waveform, and the image forming unit includes: A bubble image for a bubble is formed based on a reception signal obtained using the normal transmission waveform, and a tissue image for a tissue is formed based on a reception signal obtained using the modified transmission waveform. It is characterized by.

  In a preferred embodiment, the image forming unit forms the bubble image based on a harmonic component included in a reception signal obtained by using the normal transmission waveform, and receives by using the modified transmission waveform. The tissue image is formed based on a fundamental wave component included in the signal.

  According to the present invention, an ultrasonic transmission technique that suppresses bubble destruction and detection can be realized.

1 is a diagram illustrating an overall configuration of an ultrasonic diagnostic apparatus that is preferable in the practice of the present invention. It is a figure which shows a normal transmission waveform and a deformation | transformation transmission waveform. It is a figure which shows the vibration of the bubble by a normal transmission waveform and a deformation | transformation transmission waveform. It is a figure which shows the sound pressure waveform which a bubble radiates | emits. It is a figure which shows the frequency characteristic of the sound pressure waveform which a bubble radiates | emits.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a diagram showing an overall configuration of an ultrasonic diagnostic apparatus suitable for implementing the present invention. The ultrasonic diagnostic apparatus shown in FIG. 1 is suitable for forming an image using a contrast agent containing contrast bubbles (microbubbles such as microbubbles and nanobubbles).

  The signal generation unit 12 outputs a transmission signal for transmitting an ultrasonic pulse wave, and the waveform adjustment unit 14 adjusts the amplitude of the transmission signal output from the signal generation unit 12. The ultrasonic diagnostic apparatus of FIG. 1 forms a contrast image suitable for projecting a bubble and a fundamental image suitable for projecting a tissue. A normal transmission waveform is used for forming a contrast image, and a modified transmission waveform is used for forming a fundamental image. That is, the transmission signal output from the signal generation unit 12 is used as a normal transmission waveform as it is, while the transmission signal output from the signal generation unit 12 is adjusted in the waveform adjustment unit 14 and used as a modified transmission waveform. Is done. Note that two waveforms, a normal transmission waveform and a modified transmission waveform, may be prepared in advance, and the two waveforms may be used properly.

  FIG. 2 is a diagram illustrating a normal transmission waveform and a modified transmission waveform. FIG. 2I shows a normal transmission waveform, where the horizontal axis is the time axis and the vertical axis is the amplitude in sound pressure (kPa: kilopascals). The normal transmission waveform has, for example, a Gaussian pulse shape with a center frequency of about 1.8 MHz. In the normal transmission waveform, the amplitude on the positive side and the amplitude on the negative side are approximately the same. For example, in the waveform example of FIG. 2I, the sound pressure on the positive side is about 150 kPa, and the sound pressure on the negative side is about -150 kPa.

  On the other hand, FIG. 2 (II) shows a modified transmission waveform, with the horizontal axis representing the time axis and the vertical axis representing the amplitude in terms of sound pressure (kPa). The modified transmission waveform is formed by adjusting the negative amplitude of the normal transmission waveform, and the negative amplitude is smaller than the positive amplitude. For example, in the waveform example of FIG. 2 (II), the sound pressure on the positive side is about 150 kPa, and the sound pressure on the negative side is about −50 kPa.

  Returning to FIG. 1, the transmission beamformer (transmission BF) 16 controls a plurality of vibration elements (not shown) included in the probe 20 based on the transmission signal (normal transmission waveform or modified transmission waveform) obtained from the waveform adjustment unit 14. Thus, a transmission beam is formed.

  The probe 20 transmits and receives ultrasonic waves to a diagnostic region in the living body to which the contrast agent is administered. The probe 20 includes a plurality of vibration elements that transmit and receive ultrasonic waves. The plurality of vibration elements are transmission-controlled by the transmission beam former 16 and the transmission beam is scanned. By this scanning, a two-dimensional scanning surface is formed. Note that the transmission beam may be three-dimensionally scanned to form a three-dimensional scanning region.

  In addition, a plurality of vibration elements included in the probe 20 receive ultrasonic waves reflected from the living body, and a signal obtained thereby is output to a reception beam former (reception BF) 22. Note that transmission and reception may be performed by different vibrators.

  The reception beamformer 22 processes a signal obtained from the probe 20 to form a reception beam corresponding to the transmission beam. Thus, the reception signal obtained along the reception beam is output to the signal processing unit 24.

  In the present embodiment, a contrast image is formed by the scanning plane formed based on the normal transmission waveform, and a fundamental image is formed by the scanning plane formed based on the modified transmission waveform. The normal transmission waveform is suitable for vibrating a bubble and generating a harmonic from the bubble. On the other hand, the deformed transmission waveform is suitable for suppressing generation of bubble vibration and harmonics as much as possible and obtaining a fundamental wave from a tissue existing around the bubble.

  FIG. 3 is a diagram showing bubble vibration by a normal transmission waveform and a modified transmission waveform. When a bubble having a radius of 1.3 μm (micrometer) receives each transmission waveform, how the radius of the bubble changes. The result of simulating whether to do is shown. In FIG. 3, the horizontal axis is the time axis, and the vertical axis is the bubble radius.

  FIG. 3 (I) shows the time change of the bubble radius when the normal transmission waveform of FIG. 2 (I) is applied, and FIG. 3 (II) is the case of applying the modified transmission waveform of FIG. 2 (II). Is the time change of the bubble radius. As shown in FIG. 3, the bubble oscillation radius is smaller in the case of the modified transmission waveform than in the case of the normal transmission waveform. That is, the bubble is not easily broken in the case of a modified transmission waveform.

  This phenomenon is thought to be because the negative pressure (negative sound pressure) of the transmission waveform is more greatly involved in bubble vibration. The negative pressure of the transmission waveform is a force with which the transmission waveform pulls bubbles, that is, a force that expands the bubbles. When bubbles are expanded compared to contraction, vibrations increase. Therefore, the bubble is less likely to vibrate by reducing the negative pressure of the transmission waveform.

  FIG. 4 is a diagram illustrating a sound pressure waveform emitted by a bubble. In FIG. 4, the horizontal axis is the time axis, and the vertical axis is the sound pressure (kPa) emitted by the bubble. FIG. 4 (I) shows the time variation of the sound pressure emitted by the bubble when the normal transmission waveform of FIG. 2 (I) is applied. FIG. 4 (II) shows the modified transmission waveform of FIG. 2 (II). It is the time change of the sound pressure that the bubble emits when hit. As shown in FIG. 4, the sound pressure emitted from the bubble is lower in the case of the modified transmission waveform than in the case of the normal transmission waveform. That is, it is difficult to detect bubbles in the case of a modified transmission waveform.

  FIG. 5 is a diagram illustrating the frequency characteristics of the sound pressure waveform emitted by the bubble. In FIG. 5, the horizontal axis represents frequency, and the vertical axis represents the magnitude of each frequency component. FIG. 5 (I) shows the frequency characteristics of the sound pressure waveform of FIG. 4 (I) corresponding to the normal transmission waveform, and FIG. 5 (II) shows the sound pressure waveform of FIG. 4 (II) corresponding to the modified transmission waveform. It is the frequency characteristic regarding.

  In the case of forming a contrast image, a normal transmission waveform is used to extract a harmonic component radiated from the bubble. As shown in FIG. 5I, in the case of the normal transmission waveform, the harmonic component radiated from the bubble is relatively large. Therefore, bubbles are easily detected in the case of a normal transmission waveform. Incidentally, as shown in FIG. 5 (II), in the case of a modified transmission waveform, the harmonic component radiated from the bubble is relatively small.

  In this way, by using the modified transmission waveform in which the negative side amplitude is made smaller than the positive side amplitude, the bubble is hardly broken and the bubble is not easily detected. On the other hand, by setting the amplitude on the positive side to the same magnitude as that of the transmission waveform used for the conventional fundamental image, for example, it is possible to suppress the adverse effect on the fundamental wave obtained from the tissue other than the bubble.

  Returning to FIG. 1, the reception signal obtained along the reception beam in the reception beam former 22 is output to the signal processing unit 24. The signal processing unit 24 extracts a harmonic component from the received signal for the contrast image obtained by using the normal transmission waveform. For example, third-order or higher harmonic components are extracted from the received signal. In extracting the harmonic components, the principle of the phase inversion method (or pulse inversion method) described in Patent Document 1 may be used. Further, the signal processing unit 24 extracts a fundamental wave component from the received signal for the fundamental image obtained by using the modified transmission waveform.

  The gain adjusting unit 26 adjusts the gain of the signal extracted by the signal processing unit 24. For example, the fundamental wave component for the fundamental image is amplified. In this gain adjustment, the magnitude of the gain in the gain adjustment unit 26 is controlled according to the amount of adjustment of the negative amplitude in the waveform adjustment unit 14. The negative amplitude in the waveform adjustment unit 14 is adjusted by the user using an operation device such as a slider. Then, the magnitude of the gain in the gain adjustment unit 26 is controlled by the control unit 40 in accordance with the adjustment amount. For example, even when the fundamental wave component for the fundamental image becomes small because the negative amplitude is set small, the fundamental image is controlled not to become dark by increasing the amplification amount of the fundamental wave component. It becomes possible.

  The image forming unit 30 forms image data of a contrast image based on the harmonic component extracted from the received signal corresponding to the normal transmission waveform. As described above (see FIG. 5), in the case of the normal transmission waveform, since the harmonic component radiated from the bubble is large, the bubble is detected well. Further, the image forming unit 30 forms image data of a fundamental image in which tissues other than bubbles are projected based on the fundamental wave component extracted from the reception signal corresponding to the modified transmission waveform.

  The contrast image and the fundamental image thus formed are displayed on the display unit 32. For example, a contrast image and a fundamental image are displayed side by side. Alternatively, the contrast image and the fundamental image may be combined to form a combined image that clearly shows both the bubble and the surrounding tissue.

  The contrast image scanning plane and the fundamental image scanning plane are formed alternately, for example. When observing bubble movement, for example, a plurality of contrast image scanning planes may be continuously formed, and then a single fundamental scanning plane may be formed and repeated. Good.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

  12 signal generator, 14 waveform adjuster, 24 signal processor, 26 gain adjuster, 30 image forming unit.

Claims (2)

A probe for transmitting and receiving ultrasound to and from a diagnostic region including a bubble;
A transmission control unit that controls the probe so as to transmit an ultrasonic wave with a modified transmission waveform in which the amplitude on the negative side is smaller than the amplitude on the positive side;
A reception processing unit for obtaining a reception signal corresponding to the ultrasonic wave received by the probe;
An image forming unit that forms an ultrasonic image based on the received signal;
I have a,
The transmission control unit controls the probe using the normal transmission waveform and the modified transmission waveform in which the positive side amplitude and the negative side amplitude are substantially equal,
The image forming unit forms a bubble image for a bubble based on a harmonic component included in a reception signal obtained using the normal transmission waveform, and a reception signal obtained using the modified transmission waveform Forming a tissue image for the tissue based on the fundamental wave component included in the
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
A waveform adjustment unit for adjusting the magnitude of the negative amplitude of the modified transmission waveform;
A gain adjusting unit that adjusts a gain of a reception signal obtained by using the modified transmission waveform in accordance with an amplitude adjustment amount in the waveform adjusting unit;
Further having
An ultrasonic diagnostic apparatus.

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