JPWO2010018692A1 - Ultrasonic diagnostic equipment - Google Patents

Abstract

While maintaining the real-time property, all of the aerated contrast agent present in the tissue tomographic screen is visualized, and only the contrast agent-derived signal generated thereby is reliably distinguished and imaged. When a transmission beam is irradiated from the probe 1 onto a subject to which an ultrasound contrast agent has been administered and a tissue tomographic image is obtained using a reception echo accompanying this transmission, a plurality of transmission beams having different focal lengths are converted into focal lengths. , The correction is performed on the received echo signal, and the difference calculation unit 14 obtains the difference from the immediately preceding reception beam and integrates it with the integration processing unit 11. All the contrast medium is visualized, and only the contrast medium component is extracted and imaged.

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that can depict a finer disease site by presenting the distribution of an ultrasonic contrast agent present in a diagnostic site of a subject administered with an ultrasonic contrast agent. The present invention relates to an ultrasonic diagnostic apparatus.

  Today, the incidence of cancer diseases listed as one of the three major diseases in Japan continues to increase, and useful early diagnosis and treatment methods are strongly desired. In particular, research and development has been actively carried out for medical diagnostic imaging apparatuses that can detect the location of cancer in the very early stages, and technological advances in multiple modalities such as PET, CT, MRI, and ultrasound have progressed. It's amazing. Also, combinations of multiple modalities such as PET and CT are progressing, and superimposing molecular (functional) imaging such as specific proteins and metabolites obtained by PET on the tissue morphology imaging image obtained by CT or the like. Thus, it has become possible not only to specify a lesion site, but also to obtain knowledge that covers the progression of lesions that could not be obtained by conventional diagnostic imaging methods.

  Among them, ultrasonic diagnostic equipment has low impact on the human body, high safety, high portability, short imaging time, real-time imaging is possible, small size, low cost, high introduction rate even in clinics, etc. It is an indispensable tool for diagnosis of fetus in obstetrics and gynecology, diagnosis of abdomen, mammary gland, urinary organs, heart disease, etc. Today, in an ultrasonic diagnostic apparatus, a pulse echo type that obtains two-dimensional image data with a simple operation by simply bringing a probe into contact with the body surface is the mainstream. An acoustic pulse transmitted from the surface of the body in contact with the probe to the inside of the body is reflected at a site having a different acoustic impedance such as a tissue and a cell in the body. The reflected echo is received by the ultrasonic transducer, and the time taken for reflection is processed in the depth direction, and the reflection intensity is processed as luminance. By scanning this pulse in parallel with the body surface direction, a two-dimensional luminance image is obtained.

  In recent years, when more detailed imaging is required especially in the diagnosis of cancers typified by liver cancer, imaging may be performed after administering an ultrasound contrast agent to a subject. This is called the contrast echo method. As the ultrasonic contrast agent used at this time, microbubbles having a size of about 1 to 5 microns stabilized with a surfactant or a polymer are generally used. The microbubble contrast agent reflects an ultrasonic signal due to a difference in acoustic impedance at the gas-liquid interface, and is particularly suitable for imaging a capillary blood vessel. There are various methods for contrast echo, such as flash echo (such as Non-Patent Document 1) that captures the reperfusion of the contrast agent after the bubble is intentionally collapsed. A typical example is a harmonic imaging method (for example, Patent Document 1) that resonates and images a characteristic acoustic response.

The ultrasonic imaging method using a microbubble contrast agent has a drawback that microbubbles stay in blood vessels and do not penetrate into the tissue, so that the tissue itself cannot be imaged. Therefore, as a new ultrasonic contrast agent, as disclosed in Patent Document 2 and Non-Patent Document 2, the size of the contrast agent is set to a submicron size, aiming at leakage from new blood vessels and the like, aiming at contrasting deeper tissues. Development of new contrast methods has been carried out. In particular, the bubble contrast agent has been reported in Patent Document 2, an ultrasound imaging system approved for diagnosis, and a can contrast in ultrasound imaging intensity defined by M echanical I ndex (MI) value Therefore, early commercialization is expected.

According to Non-Patent Document 3, an aerated contrast agent encapsulates a low-boiling poorly water-soluble liquid in an overheated state in advance, and eliminates overheating with ultrasonic energy at a target site to restore the original boiling point of the liquid. It is a type of contrast agent that is vaporized into bubbles and has two characteristics. First, by setting the diameter of the particles to 0.5 microns or less, it is possible to achieve a tissue other than blood vessels, which is difficult with a conventional microbubble contrast agent. Second, it is possible to localize microbubbles by irradiating ultrasonic waves only on the target site. For these reasons, it is particularly suitable as an ultrasonic contrast agent for imaging a diseased tissue or the like in detail, and as a sensitizer for local treatment using microbubbles.
JP 2002-177268 A JP 2008-24604 A Japanese Journal of Medical Ultrasonics, Vol.23, Supplement 1; 1996; 67-195 Circulation, Vol.94; 1996; 3334 Japanese Journal of Applied Physics, Vol.44, 2005; 44: 4548

  When tissue ultrasound imaging is performed using an aerated contrast agent, ultrasound with a certain negative pressure is required to cause a phase change from a droplet to a bubble using the sound pressure of the ultrasound. . Furthermore, an ultrasonic probe provided in a general ultrasonic diagnostic apparatus scans a transmission beam converged at a focal point to obtain a tissue tomographic image. When an attempt is made to contrast an aerated contrast agent, Bubbles are generated only at the focal part where the sound pressure is locally increased (not visible as a contrast agent).

  In other words, if administered at an appropriate concentration, all contrast agents present in the ultrasonic tissue tomogram are acoustically shining, even if they exist at other sites in the tomogram. This means that the contrast agent is acoustically visualized only at the focal point of the ultrasound beam. This characteristic makes it possible to localize microbubbles. However, in order to accurately diagnose a lesion, it is desirable to visualize a contrast medium over a wide range and obtain more information.

  In addition, since imaging of aerated contrast agent is performed in a relatively high sound pressure region of diagnostic ultrasound, it is difficult to distinguish the signal level from a strong echo source such as a tissue boundary from the signal level due to aeration. There is also. If echo signals due to bubble formation are integrated in the time direction, the tissue-derived component can be suppressed and the contrast-derived signal can be emphasized, but the real-time property is significantly reduced as a trade-off.

  Based on these problems, the present invention visualizes all the aerated contrast medium present in the tissue tomographic screen while maintaining the real-time property, and reliably distinguishes and generates only the contrast medium-derived signal generated thereby. It aims at providing the technique to do.

  In order to achieve the above-described object, the ultrasonic diagnostic apparatus of the present invention uses a probe configured of a plurality of ultrasonic irradiation sources from the body surface of a subject to which an ultrasonic contrast agent is administered. When a transmission beam is formed by temporally controlling the voltage applied to the source and a tissue tomogram is formed using the received echo signal corresponding to this transmission beam, each ultrasonic irradiation source Different transmission beams with different focal lengths obtained by changing the temporal control of the applied voltage are irradiated in time series so that the transmission beams with longer focal lengths come first. A received echo signal beam profile is defined as a reference from each received echo signal obtained corresponding to each transmitted beam having a different beam profile, and all received echo signals have the reference beam profile. After correcting the received echo signal intensity at each point so that the received echo signal is substantially equivalent to that obtained by the received beam, a plurality of received echo signals W ( n) and the received echo signals W (n−1) and (n ≠ 1) are obtained to visualize all the aerated contrast agents present in the target region and extract only the contrast agent components. Image.

  In this way, by irradiating transmission beams having the same waveform in order from the longest focal length, it is possible to bubble all the aerated contrast agent present on the ultrasonic scanning line. At this time, the focal length and the interval between the adjacent focal lengths should be defined by the concentration of the locally existing contrast agent, the characteristics of the transmission beam, and the region of interest. As for the concentration of the contrast agent, it is possible to define a certain range by assuming a dose safe for a predetermined living body. The present invention includes a processing unit that calculates a focal length condition that can be influenced by characteristics such as a focal length, an applied voltage, and a frequency of a transmission beam. Furthermore, the focal distance and the contrast range are variable, and individual differences of the subject such as the contrast agent concentration and the region of interest can be reflected.

  By the way, the bubbles are widely used as an ultrasonic contrast agent because they have the property of reflecting ultrasonic waves. Therefore, they also have the characteristic of shielding ultrasonic waves when present at high concentrations. In the present invention, in order to avoid the shielding of the ultrasonic wave by the generated bubbles, the transmission beam having the longest focal length is irradiated first, and the focal length is shortened in order.

  In the present invention, at least one signal among a plurality of reception echo signals by a plurality of transmission beams has an imaging field of view necessary for acquiring a tissue tomographic image, and only reception echo signals around the focal point are acquired in other transmission beams. It has the characteristic of doing. This means that the pulse repetition frequency (PRF) is kept high, and the reduction in the imaging frame rate caused by irradiating multiple beams to the same part of the subject is minimized, and real-time characteristics can be maintained. To do.

  Next, processing of a plurality of reception echo signals by a plurality of transmission beams will be described. In this invention, it has the calculating part which irradiates the same site | part and takes the difference of the two received echo signals obtained most recently. Since the time interval between the two most recent pulses is on the order of several kHz, and the movement is at least three orders of magnitude faster than the component derived from the body movement of the subject, the tissue component in principle shows exactly the same response. Therefore, by this difference processing, it is possible to extract only the contrast agent component and display the detailed contrast agent distribution.

  When performing the above difference calculation, if two received echo signals are transmitted by beams having different focal lengths, the difference in sound pressure distribution due to the difference in focal lengths must be corrected in order to obtain a difference in received echo signals. Don't be. The ultrasonic diagnostic apparatus according to the present invention receives the received echo signal immediately before except for the first received echo signal among the received echo signals obtained by a plurality of transmission beams having different focal lengths irradiated on the same part of the subject. A calculation unit for converting into a received echo signal assuming the same focal length as the echo signal, and a storage unit storing numerical values necessary for the conversion process.

  At this time, the difference process and the conversion calculation process accompanying the difference process may be limited to only the vicinity of the focal distance where bubble formation may occur in the received echo signal, and the calculation process may be performed. Furthermore, the individual difference information obtained by the above calculation processing has contrast agent information at each focal point, and by integrating this, the distribution information of the contrast agent in the region of interest in the tomogram is obtained. Can be presented.

  In the present invention, the tissue tomographic image data obtained by sequentially mapping the received echo signals to the depth necessary for obtaining the tissue tomographic image in the azimuth direction, and the contrast agent distribution image data calculated from the contrast agent distribution information are independently obtained. Can be displayed side by side, displayed side by side, or one can be superimposed on the other. When superimposing, it is possible to display one on a gray scale and the other on a color scale having different colors. In particular, the contrast agent distribution image data can be displayed in different colors or intensities depending on the contrast agent concentration or the amount that can be converted into the concentration. Furthermore, in order to display clearly the part where the contrast agent exists at low concentration, as the contrast agent distribution image data, concentration information of multiple frames obtained by multiple times of imaging by the above method is integrated and displayed on a single screen display. It is also possible to do.

  According to the present invention, all of the aerated contrast agent existing in the tissue tomographic screen of the subject is visualized, and only the contrast agent-derived signal generated thereby is reliably distinguished and displayed superimposed on the tissue tomographic image. This makes it possible to grasp more detailed contrast medium distribution information. For this reason, more detailed information on the state of the lesion can be provided, small lesions and numerous lesions can be easily detected, and early diagnosis of lesions and accurate and safe treatment can be assisted.

1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. The conceptual diagram showing an example of the irradiation method of the several transmission pulse by this invention. The conceptual diagram showing an example of the irradiation method of the several transmission pulse by this invention. The schematic diagram of the calculation method of the focus space | interval by this invention. The conceptual diagram showing the correction process for the difference calculation by this invention. The simplified schematic diagram of the specific example of correction | amendment calculation. The simplified schematic diagram of the specific example of correction | amendment calculation. The figure showing an example of quantitative property of contrast agent concentration information obtained by the present invention. The figure of the example of an acquisition picture at the time of carrying out the present invention. The figure which shows an example of the effect at the time of integrating | accumulating and displaying the contrast agent distribution information over several imaging time by one screen display by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Probe 2 Diagnostic machine main body 3 Input part 4 Display part 5 Reception beam former 6 Transmission beam former 7 Transmission / reception sequence control part 8 Correction calculation part 9 Correction calculation memory 10 Tissue tomographic image calculation part 11 Integration processing part 12 Display data composition Unit 13 reception processing unit 14 difference calculation unit 15 selector switch 16 transmission delay / weight selection unit

  Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus uses a pulsed ultrasonic wave to obtain and display a tomographic image of a diagnostic region of a subject to which a contrast medium has been administered in advance. A probe 1 and an input unit 3 are displayed on a diagnostic machine main body 2. The display unit 4 is connected. The diagnostic machine body 2 includes a transmission / reception sequence control unit 7, a reception beamformer 5, a transmission beamformer 6, a transmission delay / weight selection unit 16, a changeover switch 15, a wave reception processing unit 13, a tissue tomogram calculation unit 10, and a difference calculation unit. 14, a correction calculation unit 8, a correction calculation memory 9, an integration processing unit 11, and a display data synthesis unit 12.

  The probe 1 is a device responsible for transmission / reception of ultrasonic signals to / from a subject. In the present invention, any probe may be used as long as it can converge the beam and can transmit and receive ultrasonic waves that satisfy the conditions necessary for bubbling.

  The input unit 3 is a console necessary for giving various instructions to the diagnostic machine body 2. A region of interest, a focal length change, and an ultrasonic transmission condition can be changed by inputting to the console. Furthermore, the display method on the display unit 3 can be switched, for example, a two-screen display of a tissue tomogram and contrast agent distribution information or a superimposed display.

  By driving the transmission beam former 6 and the transmission delay / weight selection unit 16, the transmission beam is transmitted to the subject via the probe 1 under conditions such as an appropriately set applied voltage. The transmission beam transmission conditions are defined by the transmission / reception sequence control unit 7 as described later. The transmission / reception sequence controller 7 is one of the constituent elements that characterize the present invention.

  The reception echo signal received by the probe 1 from the inside of the subject becomes a reception echo signal to which reception directivity is given by the reception beamformer 5 in the diagnostic machine body 2. The reception beamformer 5 has a reception delay circuit (not shown), and forms a reception delay circuit according to a time range for acquiring reception echo signals by respective transmission beams defined by the transmission / reception sequence control unit 7.

  A reception processing unit 13 in the diagnostic machine main body 2 detects a reception echo signal obtained by the reception beamformer 5. The reception echo signal may exist n times as many as the scanning lines required in the azimuth direction. These received echo signals are finally sent to the display data synthesizing unit 12 through the tissue tomographic image calculation unit 10, the difference calculation unit 14, the correction calculation unit 8, and the integration processing unit 11, and are provided as image data. It is.

  The tissue tomogram calculation unit 10 uses only a reception echo signal having the longest imaging field of view among a plurality of reception echo signals transmitted by the transmission beam transmitted to the same part, and uses a raster signal sequence in the ultrasonic scanning direction as a video format. To the display data composition unit 12.

  The correction calculation unit 8 determines a reference beam profile for a plurality of reception echo signals obtained by transmission beams having different beam profiles because the focal lengths are different, and transmits all reception echo signals having the reference beam profile. The received echo signal intensity at each point is corrected and calculated so that the received echo signal is substantially equivalent to that obtained by the beam. Furthermore, it has the memory 9 which stored the numerical value required for the said conversion process. The correction calculation unit 8 and the correction calculation memory 9 that perform the correction process are one of the constituent elements that characterize the present invention. The difference calculation unit 14 calculates the difference between the received echo signals corrected by the correction calculation unit 8.

  The integration processing unit 11 irradiates the same part of the subject and stores individual differential echo signals obtained by the arithmetic processing, and performs integration processing, and integrates the differential echo signals at the respective focal points. By doing so, contrast agent distribution information is generated. Further, the contrast agent distribution information is changed from the raster signal sequence in the ultrasonic scanning direction to the raster signal sequence in the video format, and this is sent to the display data synthesis unit 12.

  The display data synthesizing unit 12 synthesizes the tissue tomographic image data and the contrast agent part image data as image data based on the display method specified by the input unit 3 and sends it to the display unit 4 together with desired setting parameters. The display unit 4 displays these data on a screen such as a cathode ray tube or a liquid crystal.

  An example of the procedure for generating image data for diagnosis and treatment support by the ultrasonic diagnostic apparatus according to the present embodiment will be described below.

  FIG. 2 is a conceptual diagram showing an example of the irradiation method of a plurality of transmission beams for forming one raster according to the present invention. One arrow in the figure represents one transmission beam S (n), and a dotted line R illustrated on the right side of each arrow represents a time range in which a reception echo signal by each transmission beam is acquired. At least three transmission beams are irradiated to the same part. The transmission beam that irradiates the same part is represented by S (n) (n: the order in which the same part is irradiated), and the focal point is represented by F (m) (m: the order of the length of the focal length, 1 = the longest focal length) The focus of the transmit beam S (n) is F (m). That is, the transmission beam with the longest focal length is irradiated first, and the focal length of the transmission beam is shortened in order. When all the contrast agent is bubbled, the distance between F (m) and F (m + 1) needs to be equal to the range in the depth direction that is bubbled by one transmission beam, as will be described later. Is calculated.

  The end point of the acquisition range of the received echo signal R is defined by the required ultrasonic imaging area when n = 1. In FIG. 2, the transmission beam S1 and the reception echo signal R1 are shown to have the same length, but S1 = R1 is not necessarily required depending on the required ultrasonic imaging region. Further, the end point of the signal acquisition range of the received echo signal R (n) where n ≠ 1 is up to the range in the depth direction that is bubbled by one transmission beam, and is calculated as described later.

  FIG. 3 is a conceptual diagram showing another example of the irradiation method of a plurality of transmission beams for forming one raster in the present invention. The transmission beam that irradiates the same part is represented by S (n) (n: the order in which the same part is irradiated), and the focal point is represented by F (m) (m: the order of the length of the focal length, 1 = the longest focal length) The focus of the transmit beams S (2n) and S (2n-1) is F (m). That is, S (2n) and S (2n-1) have the same focal length, the transmission beam with the longest focal length is irradiated first, and the focal length of the beam is shortened in order for every two transmission beams. . At this time, the calculation method of the distance between F (m) and F (m + 1) and the end point of the acquisition time range of the received echo signal R is the same as the irradiation method shown in FIG. This irradiation method takes about twice as long as the imaging time as compared with the irradiation method shown in FIG. 2, but has the advantage of simplifying the structure because the correction calculation as shown in FIG. 5 is not required.

  The control of this irradiation method is defined in the transmission / reception sequence control unit 7.

  FIG. 4 schematically shows an example of a method for calculating the focal length interval. When a certain amount of contrast agent that does not affect the health of the subject is administered, the ultrasound irradiation condition sufficient for bubbling is defined as the condition where bubbling can be obtained with half the sound pressure obtained at the focal point. The range in the depth direction where bubble formation occurs is a range F ± (a / 2) centered on the focal point.

  At this time, when the same number of elements on the probe 1 are used for transmission beam formation, the F number changes according to the focal length F (x). Since the depth of focus in the depth direction increases as the F number increases, the range of a increases accordingly. In the example of FIG. 4, a (1)> a (2).

  It is also possible to perform correction in consideration of attenuation in the living body (0.5 dB / MHz / cm in normal liver tissue) according to the focal point F (x). For example, when correction by attenuation is performed, the range a (2)> a (1). It is also possible to change the focal interval, reflecting the local concentration of the contrast agent, which is represented by Δa in FIG. For example, in the liver or the like, it is conceivable that the local concentration increases due to the uptake of the contrast agent by Kupffer cells. That is, it is expected that bubble formation will occur at a sound pressure lower than the ultrasonic conditions required for bubble formation assuming other normal tissue concentrations, and bubble formation will occur in a wider range than a. The range where bubble formation occurs is represented by a + Δa (Δa> 0). At this time, Δa is set based on the sound pressure condition necessary for bubbling required at a high concentration. When there is no need for correction, the distance between F (m) and F (m + 1) is set so that Δa = 0.

  The pulse repetition frequency has the same meaning as the reciprocal of the time range in which the received echo signal R (n) represented by the dotted line in FIGS. 2 and 3 is acquired. The longer the dotted line, the lower the frequency. When n = 1, the end point of the time range to be acquired is defined by the necessary imaging field of view as described above. In the case of n ≠ 1, the end point of the range to be acquired is the deepest point where the sound pressure higher than the strength sufficient for bubbling is obtained, and is F (m) + a / 2 + Δa in FIG. By this processing, the pulse repetition frequency is increased, so that the time required for imaging can be shortened. This is controlled by the reception beamformer 6 and the transmission / reception sequence controller 7.

  The number of transmission pulses that irradiate the same part is basically calculated based on the range of the tissue tomogram and the distance between F (m) and F (m + 1). You can also do it. This is particularly effective when a region to which a contrast medium will be present in the tissue tomogram is predicted in advance. In particular, in imaging where real-time characteristics are important, by defining the region of interest, not only the number of transmission pulses that irradiate the same part, but also the number of scanning lines required in the azimuth direction can be reduced, and the frame rate can be improved. There is also an effect that leads to.

  These transmission beams S are transmitted to the subject via the probe 1, and the received echo signal R reflected and returned also passes through the probe 1 via the reception beam former 6 and the reception processing unit 13. It is sent to the difference calculation unit 14. Here, in order to extract only the received echo signal derived from the contrast agent, the absolute value of the difference between the two received echo signals R obtained most recently by irradiating the same part of the subject is calculated. This calculation is the absolute value of {R (n) −R (n−1)} in the example of FIG. 2, where n ≠ 1, and in the example of FIG. 3, {R (2n) −R (2n−1)} It is expressed as an absolute value. When the irradiation method illustrated in FIG. 2 is applied, a difference calculation is performed after a correction calculation described below is performed in advance.

  Since the time interval between the two most recent pulses is on the order of several kHz, and the movement is at least three orders of magnitude faster than the component derived from the body movement of the subject, the tissue component in principle shows exactly the same response. Therefore, by this difference processing, it is possible to extract only the contrast agent component and display the detailed contrast agent distribution.

FIG. 5 is a conceptual diagram showing correction processing for difference calculation according to the present invention. The ultrasonic transmission beam is focused in the subject and is narrowed to the narrowest range at the focal point F. At the same time, the sound pressure on the beam center axis increases in inverse proportion to the beam width and reaches the maximum sound pressure at the focal point F. This is the relative sound pressure on the central axis normalized by the sound pressure at the front face of the transducer built in the probe 1, Z the distance from the probe normalized by the focal length, and D the sound When a parameter representing the degree of focus is used, it can be expressed as the following equation.

The ultrasonic diagnostic apparatus according to the present invention has sound pressure distribution data of ultrasonic beams having different focal points in the correction calculation memory unit 9 within a range of parameters that can be assumed based on this formula and tuning at the time of mounting. . For example, as shown in FIG. 5, the change ΔI _S of the sound pressure value of the transmission beam S (n) for each correction calculation slot Δz (that is, the distance from the sound source (probe)), and stores the signal intensity distribution value [Delta] _R of the received echo signals, assuming a uniform sound field. The correction calculation process is performed on a plurality of received echo signals assuming different ΔI _S / Δz, that is, different ΔI _R / Δz, so that the plurality of received echo signals become substantially equivalent echo signals. In addition, the received echo signal intensity for each Δz is corrected.

FIG. 6 shows a schematic diagram of a specific example of the correction calculation. The horizontal axis represents one correction calculation slot. When a uniform sound field is assumed, the received echo signals R (1) and R (2) obtained by the transmission beams S (1) and S (2) having different beam profiles are actually in the tissue. It is considered to exhibit a response, such as in the range from shaded portion dZ ₁ of dZ ₂ due to the influence of various scatterers. By correcting ΔI _R2 using the correction coefficient (ΔI _R1 / ΔI _R2 ) from the value stored in the memory unit 9, it is possible to perform correction processing even in a region affected by such a nonlinear scatterer. In this case, R (1) = corrected R (2) in the scattering part assuming the tissue, and the absolute value of the difference in the shaded part is zero. FIG. 7 shows a simplified schematic diagram of a received echo signal in a state where a contrast agent actually exists as another specific example of the correction calculation. In the range from dZ ₁ to dZ _2, the signal R (1) including the contrast agent component is corrected to R (2), and the absolute value of the difference is generated.

  At this time, the difference processing and the correction processing associated therewith are limited to the range of F ± (a / 2 + Δa) shown in FIG. 4, that is, only around the focal point where the bubble formation of the received echo signal can occur. You may do it.

  The differential processing is dynamically performed every time two received echo signals are accumulated, but the differential echo signal is temporarily stored in the integration processing unit 11. When all the differential echo signals by the plurality of received echo signals irradiated to the same part of the subject have been processed, these signals are integrated and processed as final contrast agent distribution information.

  The display data synthesizing unit 12 synthesizes the tissue tomographic image data and the contrast agent distribution image data as image data based on the display method designated by the input unit 3 and sends the image data together with desired setting parameters to the display unit 4. At this time, the tissue tomographic image data can be displayed as a gray scale image, and the contrast agent distribution image data can be displayed as different color scale images. It is also possible to display the tomographic image of the contrast agent, which is a transient signal component, at the same time for diagnosis. Further, the contrast medium distribution image data can be displayed in a color map by changing the color or intensity in accordance with the contrast medium concentration or the amount that can be converted into the density. In addition, the contrast distribution information over multiple imaging times can be integrated and displayed on a single screen display, and it is also possible to present lesion information more clearly when contrast medium is present only at low concentrations. It is. At this time, the tissue tomographic image data to be superimposed is that of the first frame, and only the contrast agent information image data is integrated in the frame direction. For example, when the data density obtained by this method is imaged at a frame rate of 30, if one second of data is accumulated and displayed, it is possible to simply obtain contrast agent information data having a density 30 times higher.

  FIG. 8 shows an example of the quantitativeness of contrast agent concentration information obtained by the present invention. This is because an aerated contrast agent having a known concentration within a range that does not affect the health of the subject is enclosed in an acrylamide gel, and all the aerated contrast agents present in the gel are based on the irradiation sequence according to the present invention. After irradiating the ultrasonic wave with the intensity that can be bubbled, the received echo signal from the region of interest is analyzed, and finally the integrated value of the differential echo signal is graphed. From the graph, it can be said that the aerated contrast agent concentration and the integrated value of the differential echo signal generated thereby have a linear relationship. That is, it can be said that the differential echo signal integrated value corresponds to relative contrast agent concentration information.

  Next, an example of an acquired image when the present invention is implemented will be described with reference to FIG. In this figure, image data is virtually generated and shown at all stages. A reception echo signal (illustrated image obtained by imaging the first reception echo signal) by transmission beams having different focal lengths has both a tissue-derived signal and a contrast agent-derived signal at the focal point. When the difference between the two echo signals obtained by irradiating the same part of the subject and obtained immediately before is corrected assuming the same focal length, a contrast agent-derived signal at the focal point is extracted (the figure shows four different focal points). Assumed to have). By performing this integration processing, contrast agent distribution information is formed. Further, the display data synthesis unit 12 superimposes it on the tissue tomographic image and displays it on the display unit 4 by changing the color tone. It can be presented in detail.

  FIG. 10 shows an example of the effect when the contrast agent distribution information over a plurality of imaging times is integrated and displayed on a single screen display. This is because the contour of the affected area is not clear in the first frame from which accumulation starts, since only a low concentration of contrast medium distribution is obtained. However, as the frame accumulation is repeated, the contrast medium concentration is virtually increased. This is an example where the outline gradually becomes clear.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, an invention formed by an appropriate combination of a plurality of constituent elements disclosed in the above embodiment is also included in the scope of the present invention.

Claims (7)

In an ultrasonic diagnostic apparatus that transmits an ultrasonic transmission beam from a probe to a subject administered with an ultrasonic contrast agent and obtains a tomographic image of the subject using a reception echo signal by this transmission,
A transmission sequence unit that transmits a transmission beam having a different focal length to the same part three or more times, with a longer focal length first;
A reference beam profile is defined for a plurality of reception echo signals obtained by the transmission beams having different beam profiles due to different focal lengths, and all reception echo signals are obtained by transmission beams having the reference beam profile. A correction processing unit that corrects the received echo signal intensity at each point so that the received echo signal is substantially equivalent to
A difference calculation unit for obtaining a difference between the corrected plurality of received echo signals;
Storing a plurality of received echo difference signals necessary to form one raster, and integrating the same to generate contrast agent distribution image data;
A tissue tomographic image calculation unit that generates tissue tomographic image data from the received echo signal; and a display data synthesis unit that synthesizes data to be displayed on a display unit from the tissue tomographic image data and the contrast agent distribution image data. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to claim 1, wherein the received echo signal used to generate the tissue tomographic image data has a longest focal length among transmission beams necessary to form one raster. An ultrasonic diagnostic apparatus characterized by using a transmission beam.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the focal lengths F (1) to F (n) of the transmission beam necessary to form one raster (n is an irradiation order of the transmission beam, and n> 3 ) Satisfies the relationship of F (1) ≧ F (2)> F (3) ≧ F (4)>...> F (2n−1) ≧ F (2n).   The ultrasonic diagnostic apparatus according to claim 3, wherein the end point of the echo signal acquisition range of the received echo signal by the n-th transmission beam is the focal length F (n), the focal depth a, and the focal depth correction range Δa. When shown, the ultrasonic diagnostic apparatus is F (n-1) + a / 2 + Δa except for the first received echo signal.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the display data synthesis unit superimposes one of the tissue tomographic image data and the contrast agent distribution image data as a gray scale diagram and the other as a color map diagram. Ultrasonic diagnostic equipment.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the contrast medium distribution image data is displayed with a different color or intensity depending on a contrast medium concentration or an amount that can be converted into a density. Diagnostic device.   The ultrasonic diagnostic apparatus according to claim 6, wherein an integrated value obtained by integrating the contrast agent concentration or an amount that can be converted into the concentration over a plurality of imaging times is displayed.

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