Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/48—Diagnostic techniques
  • A61B8/481—Diagnostic techniques involving the use of contrast agents, e.g. microbubbles introduced into the bloodstream
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
  • G01S15/88—Sonar systems specially adapted for specific applications
  • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
  • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
  • G01S15/895—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum

Definitions

• the present invention relates to an ultrasonic diagnostic apparatus for imaging the inside of a subject such as a living body by transmitting and receiving ultrasonic waves.
• Ultrasonic diagnostic apparatuses that transmit and receive pulsed ultrasonic waves to a living body and image the inside thereof are widely used for medical diagnosis.
• imaging modalities in the field of X-rays and MRI, contrast agents have been used for imaging of the circulatory system.
• contrast agents have not been widely used in ultrasonic diagnostics until now, but in recent years, a formulation in which microbubbles having a size on the order of microns * have been stabilized in some way. With the advent of contrast agents, the method has been widely used. This principle utilizes the fact that microbubbles with a diameter of about 1 micron resonate with the ultrasonic waves of several MHz used in ultrasonic diagnostics and vibrate with large amplitudes. The reflection produces a contrast ability.
• X-ray and MRI contrast agents do not irreversibly change their physical properties due to the effects of electromagnetic waves applied for imaging or applied magnetic fields.
• the contrast agent of the stabilized micropable preparation system may be disintegrated and disappeared by the irradiation of the ultrasonic waves irradiated for imaging, and the contrast ability may be greatly reduced. This is due to the fact that under stable imaging conditions, the image is irradiated with ultrasonic waves of sufficient intensity and frequency to obtain a good image SN ratio. It becomes a problem when trying.
• the contrast agent in the region of interest can be appropriately erased and the contrast conditions can be initialized.
• This can be considered to be a unique feature of the stabilized contrastable mic orifice-based ultrasound contrast agent that is significantly different from X-ray and MRI contrast agents.
• the most widely used and simplest measure of ultrasonic intensity is the ultrasonic energy per premature time, commonly called the ultrasonic intensity.
• MI maximum negative pressure
• no square root of the center frequency
• the intensity and irradiation frequency of the ultrasonic waves represented by these indices are low during a time phase in which it is not desired to decrease the density of the contrast agent in the subject, for example, the region of the living body to be examined.
• a mode is provided to capture images by irradiating ultrasonic waves at a low level.
• it is difficult to obtain a good image S / N ratio due to insufficient ultrasonic signal strength, and the imaging rate decreases at low ultrasonic irradiation frequency, and the change of the target body region on the ultrasonic image There is a problem that it cannot be followed sufficiently.
• the present invention firstly aims to stabilize a micro-pulverized body region of interest while irradiating ultrasonic energy necessary for obtaining a good image SN ratio and a sufficient frame rate. Second, it is possible to suppress the decrease in the density of the system contrast agent, and, if necessary, stabilize the microvapour contrast agent in the region of interest while controlling the ultrasonic intensity and mechanical index within the safety limits. It is an object of the present invention to provide an ultrasonic diagnostic apparatus that can be efficiently eliminated.
• the maximum negative pressure emphasized waveform that emphasizes the maximum amplitude negative pressure peak value that is, the maximum negative pressure emphasized waveform that is larger than the positive pressure side peak value (Fig. 6)
• the ultrasonic sound The sound pressure rise emphasis waveform whose waveform rises more steeply than its fall (Fig. 7, also called N-wave), and the sound pressure fall emphasis waveform whose fall of the ultrasonic sound pressure waveform steeper than its rise (Fig. 8 , And also called inverse N-wave).
• Figure 1 shows the results of theoretically predicting the behavior of a microbubble exposed to the sound pressure of such a waveform by numerical calculation, and comparing the total ultrasonic energy of the fundamental wave and the second harmonic with the same.
• the thick solid line indicates the case of the maximum positive pressure emphasized waveform
• the thick dotted line indicates the case of the maximum negative pressure emphasized waveform
• the thin solid line indicates the case of the sound pressure rise emphasized waveform
• the thin dotted line indicates the case of the sound pressure fall emphasized waveform.
• the sound pressure drop emphasis waveform maximizes the maximum surface area during microbubble vibration, and conversely, in the region where the ultrasonic intensity is relatively low, the sound pressure rise emphasis waveform or the maximum positive It was found that the pressure emphasis waveform minimized the maximum surface area during vibration.
• Figure 2 shows the results of a comparison of the maximum surface area during microbubble vibration for each waveform with a common mechanical index.
• the thick solid line, the thick dotted line, the thin solid line, and the thin dotted line in the figure are the same as in FIG.
• the maximum surface area during vibration was the maximum at the time of the maximum positive pressure emphasis waveform. Therefore, it is considered that the maximum positive pressure emphasized waveform is suitable for efficiently eliminating the stabilized microbubble-based contrast agent in the target living body region under the condition of a constant mechanical index.
• the present invention is suitable for suppressing the decrease in the density of the stabilized micro-purple contrast agent in the region of interest by superimposing the harmonics on the fundamental wave and controlling the order correlation between the two.
• the problem is solved by creating a waveform that has been reduced or, conversely, a waveform that is suitable for efficient reduction, and using the waveform appropriately as needed.
• the ultrasonic diagnostic apparatus of the present invention uses the ultrasonic probe to transmit and receive ultrasonic waves to and from the object to which the contrast agent has been introduced, thereby imaging the inside of the object to be inspected.
• the ultrasonic probe is configured to transmit an ultrasonic pulse in which a fundamental wave and a harmonic including at least a second harmonic of the fundamental wave are superimposed. It is characterized by
• the present invention is characterized in that, in the above configuration, the ultrasonic pulse transmitted from the ultrasonic probe includes a sound pressure drop emphasis waveform in which the fall of the ultrasonic waveform is sharper than the rise.
• the ultrasonic wave transmitted from the probe is characterized in that it comprises a maximum positive pressure emphasis waveform in which the maximum amplitude positive pressure side peak value is greater than the negative pressure side peak value.
• the present invention is characterized in that, in the above configuration, the sound pressure drop emphasizing waveform and the maximum positive pressure emphasizing waveform are switchable according to a transmission mode.
• the present invention is characterized in that, in the above configuration, an ultrasonic image captured using an ultrasonic pulse having the sound pressure drop emphasizing waveform or the maximum positive pressure emphasizing waveform is displayed.
• the present invention is characterized in that, in the above configuration, the contrast agent contains micro purple, and a center frequency of the fundamental wave is set in accordance with a resonance frequency of the micro purple.
• the ultrasonic pulse may have a waveform in which the fundamental wave and a 2nd harmonic having a phase shifted by ⁇ / 2 at the zero cross point of the fundamental wave are superimposed. It is characterized by.
• the invention is characterized in that, in the above configuration, the ultrasonic pulse has a waveform in which the fundamental wave and the fundamental wave are superimposed with a double harmonic having the same phase at a zero cross point thereof. I do.
• a maximum positive pressure emphasized waveform in which a maximum amplitude positive sound pressure side peak value is larger than a negative sound pressure side peak value, and a maximum amplitude negative sound pressure side peak value is a positive sound pressure side
• the present invention in the above configuration, transmits an ultrasonic pulse wave having the sound pressure rise emphasis waveform or the maximum positive pressure emphasis waveform as a main component. And a second mode for transmitting an ultrasonic pulse wave having the sound pressure drop emphasizing waveform or the maximum positive pressure emphasizing waveform as a main component.
• FIG. 1 shows the maximum surface area during microbubble vibration comparing the total ultrasonic energy of the fundamental wave and the second harmonic wave as a common one.
• Fig. 2 shows the maximum surface area during microbubble vibration comparing the same mechanical index.
• FIG. 3 is a block diagram illustrating a configuration of one embodiment of the present invention
• FIG. 4 is a block diagram illustrating a configuration of another embodiment of the present invention
• FIG. 5 is a block diagram illustrating the configuration of another embodiment of the present invention.
• Fig. 6 shows the transmitted sound pressure waveform (1) measured by a needle-shaped hydrophone immediately adjacent to the probe of the ultrasonic diagnostic apparatus.
• Fig. 6 shows the waveform measured by the needle-shaped hydrophone immediately adjacent to the probe of the ultrasonic diagnostic apparatus of the present invention.
• FIG. 1 shows the maximum surface area during microbubble vibration comparing the total ultrasonic energy of the fundamental wave and the second harmonic wave as a common one.
• Fig. 2 shows the maximum surface area during microbubble vibration comparing the same
• FIG. 7 is a diagram showing a transmitted sound pressure waveform (2)
• FIG. 7 is a diagram showing a transmitted sound pressure waveform (3) measured by a needle-type microphone near the probe of the ultrasonic diagnostic apparatus of the present invention.
• the probe of the ultrasonic diagnostic apparatus of the present invention Fig. 9 shows the transmitted sound pressure waveform (4) measured by a needle-shaped hydrophone in Fig. 9, and Fig. 9 shows the results of measurement of the particle size distribution of the stabilized microphone mouth purple before and after ultrasonic irradiation by the ultrasonic diagnostic apparatus of the present invention
• FIG. 10 shows the results of measurement of the particle size distribution of stabilized microbubbles before and after ultrasonic irradiation by the ultrasonic diagnostic apparatus of the present invention (2)
• FIG. 10 shows the results of measurement of the particle size distribution of stabilized microbubbles before and after ultrasonic irradiation by the ultrasonic diagnostic apparatus of the present invention (2)
• FIG. 10 shows the results of measurement of the particle size distribution of stabilized microbubble
• FIG. 11 shows the results of the present invention.
• Figure 3 shows the results of measurement of the particle size distribution of stabilized microbubbles before and after ultrasonic irradiation by the ultrasonic diagnostic apparatus of Fig. 1.
• Fig. 12 shows the stability before and after ultrasonic irradiation by the ultrasonic diagnostic apparatus of the present invention.
• Fig. 4 shows the results of measurement of particle size distribution (4) of a micro-bubble.
• 3 and 4 are block diagrams showing a typical configuration of an apparatus in which the present invention is applied to an ultrasonic diagnostic apparatus based on a pulse echo method.
• the transmission waveform control unit 1 emphasizes the positive peak pressure value of the maximum amplitude, that is, the maximum positive pressure emphasized waveform that is larger than the negative sound pressure peak value, such as the sound pressure waveforms shown in FIGS. 5 to 8 as examples.
• the maximum negative pressure emphasis waveform in which the peak value of the maximum amplitude negative sound pressure side is emphasized that is, larger than the positive sound pressure side peak value
• the rising of the ultrasonic sound pressure waveform is steeper than the falling
• the directional ultrasonic pulse sent out from the transducer array 5 to the living body in this way is reflected by living tissue and a contrast agent, and a part of the pulse returns to the transducer array 5, and each of the constituent elements Is received.
• each signal of the element selected by the element selection switch 4 is amplified by the preamplifier 6, then subjected to AZD conversion, and temporarily stored in the reception memory 7.
• the A / D conversion is generally performed. This is because ultrasonic waves propagating in the living body Compensating that the amplitude of the received signal decreases almost in proportion to the elapsed time from the transmission corresponding to the attenuation in proportion to the seeding distance, the signal amplitude at the entrance of the A / D converter is compensated. This is a process to keep the size within a certain range. This prevents a reduction in signal dynamic range due to amplitude quantization in A / D conversion.
• by passing the signal through a band-limiting filter before the A / D conversion it is possible to prevent aliasing due to time axis quantization in the A / D conversion.
• the reception signal of each element stored in the memory 7 is given a kind of delay according to the position of each element and then added to each other to obtain a convergence effect.
• the reception convergence delay adding section 8 performs the processing.
• the optimum value of the delay time to be given to the signal of each element changes according to the focal length of the receiving wave.
• the optimum value of the focal length of the receiving wave for obtaining a good pulse echo image becomes longer in proportion to the elapsed time from the transmission and the speed of sound. Therefore, it is desirable to use a receiving method in which the delay time given to the signal of each element is changed according to the elapsed time from the transmission. In this method, as shown in FIG. 3 and FIG.
• a nonlinear component is extracted from the signal obtained by delay addition for convergence of the received wave, and this component is extracted. A similar process is performed to obtain a display signal. As a result, it is possible to obtain a Panoles echo image in which the distribution of the stabilized micro-bubble contrast agent having a large non-linear reflectivity as compared with the biological tissue is emphasized.
• a harmonic generated by a non-linear effect is separated and extracted from a fundamental wave by a band-pass filter.
• a basic method of forming a nonlinear component with the harmonic component separated by the band-pass filter is used. It cannot be used as is.
• Non-linear component extraction methods that do not depend on bandpass filters include a pulse inversion method and an amplitude modulation method.
• FIG. 3 shows an embodiment of the present invention when these are applied.
• a sound pressure waveform in which a -harmonic is superimposed on a fundamental wave as shown in Figs. 5 to 8 as an example is selected, and the amplitude is changed in a plurality of ways and transmitted.
• the principle of the nonlinear component extraction is that the amplitude of the received echo linear component is proportional to the transmission amplitude, but the amplitude of the nonlinear component is not proportional to the transmission amplitude.
• the signal after reception convergence obtained by transmitting at the first amplitude A1 is recorded in the memory 9 and the second amplitude A2 is used.
• the signal after the convergence of the signal obtained by transmitting the signal is multiplied by A1 to A2, and the difference from the signal recorded in the memory 9 is taken to eliminate the linear component and extract the nonlinear component.
• a 1 and A 2 are positive real numbers.
• the pulse inversion method uses a pair of real numbers with inverted signs and the same absolute value as A 1 and A 2.
• a waveform that emphasizes the maximum positive pressure and a waveform that emphasizes the maximum negative pressure, a waveform that emphasizes the sound pressure rise, and a waveform that emphasizes the sound pressure fall are: like this 2/00945
• microbubble contrast agents are susceptible to irreversible changes such as instability, loss, contraction, and association due to irradiation with ultrasonic pulses.
• FIG. 4 shows another embodiment of the present invention in the case of obtaining a pulse echo image in which the distribution of the contrast agent is enhanced by utilizing such properties.
• One of the sound pressure waveforms in which the harmonics are superimposed on the fundamental wave as shown in Figs. 5 to 8 as an example is selected and transmitted with a constant amplitude multiple times.
• the signal after reception convergence obtained by the first transmission is recorded in the memory 9 and the signal after reception convergence obtained by the second transmission is recorded.
• the component that does not change is eliminated, and the fluctuation component corresponding to the irreversible change of the contrast agent is extracted.
• the signal of the stationary biological tissue is completely erased, which may be inconvenient in displaying the distribution position of the contrast agent.
• the weight given to the signal obtained by the first transmission and the weight given to the signal obtained by the second transmission are not completely equal to 1: 1, but rather increased by several% or Decreased Can be dealt with.
• the time axes instead of making the time axes completely coincide when taking the difference, it is possible to deal with this by shifting the ultrasonic cycle by several%.
• the signal obtained by performing such signal processing in the fluctuation component extraction unit 11 is subjected to the processing described in the previous section to obtain a display signal.
• FIGS. 5 to 8 show transmission sound pressure waveforms when an ultrasonic wave is irradiated into water using the ultrasonic diagnostic apparatus of the embodiment of the present invention having the configuration of FIG. 3 or FIG.
• the results obtained by using a needle-shaped hydrophone near the probe are shown.
• a hydrophone capable of obtaining a voltage pressure having the same sign as the input sound pressure was used.
• the four types of sound pressure waveforms obtained by shifting the phase relationship are the maximum positive pressure emphasis waveform in Fig. 5 and the maximum negative pressure waveform in Fig. 6.
• the emphasized waveform, the sound pressure rise emphasized waveform (N wave) in Fig. 7, and the sound pressure fall emphasized waveform (inverse N wave) in Fig. 8 are shown.
• the amplitudes of the fundamental wave component and the second harmonic wave component were fixed.
• Figures 9 to 12 show the size of microbubbles before and after irradiating ultrasonic waves with the sound pressure waveforms shown in Figures 5 to 8 into water and irradiating microbubbles suspended in water a certain number of times. The results of examining the change in the distribution of (particle size) are shown.
• Figures 9 to 12 show the maximum positive pressure emphasis waveform (Fig. 5), maximum negative pressure emphasis waveform (Fig. 6), sound pressure rise emphasis waveform (Fig. 7), and sound pressure fall emphasis as sound pressure waveforms, respectively. The case where the waveform (Fig. 8) is used is shown.
• the solid line (B) shows the difference before and after the ultrasonic irradiation
• the dashed line (C) shows the difference before and after the ultrasonic irradiation
• the dashed line (D) shows the difference between the results before and after the ultrasonic irradiation.
• the number of microbubbles with a diameter of less than 1 micron has increased slightly. It is considered that the stabilized shell was counted.
• the sound pressure rise emphasis waveform, the maximum positive pressure emphasis waveform, or a waveform in between them is selected, and the fluctuation due to multiple transmissions is selected. It is advantageous to obtain a pulse echo image in which the distribution of the contrast agent is enhanced by component extraction or nonlinear component extraction by the amplitude modulation method.
• the present invention by controlling the transmission waveform, it is possible to suppress a decrease in the density of the stabilized micro-purple contrast agent in the target living body region while suppressing a decrease in the density of the favorable image SN ratio and the sufficient frame rate.
• Ultrasonic imaging is possible, and the ultrasound intensity and mechanical index are kept within safety limits, and the stabilizing microphone area of the target biological area is efficiently eliminated as needed, while the bubble-based contrast agent is efficiently used.

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• 2001
  • 2001-09-20 JP JP2001286315A patent/JP4157688B2/ja not_active Expired - Fee Related
• 2002
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