JPWO2017047328A1 - Ultrasonic diagnostic apparatus and ultrasonic imaging method - Google Patents

Abstract

Provided is an ultrasonic diagnostic apparatus capable of calculating a two-dimensional velocity vector of a tissue in real time without sacrificing a frame rate. At the time of Doppler mode imaging, one or more Doppler auxiliary beams 32 are transmitted and received in a direction different from the Doppler transmission / reception beam 31, and a site where a structure such as a blood vessel wall 32 exists is detected. The motion velocity vector of the structure at the position of the intersections 35 and 36 where the beams in the two directions of the Doppler beam and the Doppler auxiliary beam intersect is calculated using the information obtained from the Doppler beam and the Doppler auxiliary beam. Calculate the motion velocity vector of the entire structure.

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a technique for calculating a motion velocity vector of a target tissue.

  An ultrasonic diagnostic apparatus is an apparatus that transmits ultrasonic waves into a living body, receives reflected waves, and images them according to intensity and time. In this apparatus, morphological imaging of these structures is performed by utilizing the fact that the intensity of reflected waves varies depending on the difference in acoustic impedance of soft tissues such as muscles and internal organs in a living body. Therefore, there are advantages such as low invasiveness, high real-time property, and high portability of the device compared to other imaging devices, and it is used in a wide range of fields such as cardiovascular, obstetrics and gynecology and internal medicine.

  In addition to morphological imaging, functional imaging techniques for imaging functions in a living body have been developed for ultrasonic diagnostic apparatuses. A typical example is a Doppler imaging method that performs blood flow imaging and velocity estimation from the frequency shift of an ultrasonic transmission / reception signal. In the Doppler imaging method, the movement in a direction parallel to the ultrasonic transmission / reception direction, that is, the velocity in one direction approaching or moving away from the probe is measured. This Doppler imaging is applied not only as an estimation of blood flow velocity but also as a technique for estimating the motion of a tissue such as a heart wall. There are other methods for estimating tissue motion, but Doppler imaging requires a relatively small amount of computation and is an excellent method for displaying motion in real time.

  However, Doppler imaging can only capture movement in a direction parallel to the ultrasound transmission / reception direction. Therefore, in Patent Document 1, multidirectional blood flow information is displayed by irradiating the measurement site with ultrasonic pulses used for Doppler imaging from different directions and superimposing the blood flow information obtained in each direction. Techniques to do this are disclosed. Also, in Patent Document 2, as in Patent Document 1, an ultrasonic pulse used for Doppler imaging is irradiated from different directions to a measurement site, and a velocity vector of a moving body is calculated based on the obtained individual velocity information. It is disclosed. Here, the moving body refers to both blood flow and tissue, and means for calculating both vectors is provided.

Japanese Patent Laid-Open No. 5-49939 JP 2006-55493 A

  In the above conventional technique, since the ultrasonic pulse used for Doppler imaging is irradiated twice, there is a problem that the time required for imaging one frame is approximately doubled. Further, in the above-described prior art, only the region where the ultrasonic transmission / reception signals irradiated from two different directions are superimposed is the measurement target region, and the measurement target region is greatly narrowed compared to the case of irradiation from one direction, and the probe The further away from the measurement area, the narrower the measurement target area.

  Furthermore, in the case of Doppler measurement for both blood flow and tissue, the speed of movement of the two is greatly different, and thus the repetition frequency of ultrasonic transmission and reception suitable for measurement is also greatly different. There is no means to distinguish between. Therefore, considering simultaneous measurement of both blood flow and tissue, for example, when calculating a two-dimensional vector of blood flow based on tissue motion information, iteratively separate for tissue and blood vessels. A method of transmitting and receiving an ultrasonic signal having a frequency is conceivable, but in that case, there is a problem that the frame rate is further reduced.

  An object of the present invention is to solve these problems and provide an ultrasonic diagnostic apparatus and an ultrasonic imaging method capable of performing real-time processing and calculating a motion velocity vector of a target tissue with high accuracy. And

  In order to achieve the above object, according to the present invention, an ultrasonic diagnostic apparatus uses a probe that transmits / receives ultrasonic waves to / from a subject, and 1 in a direction different from a Doppler beam transmitted / received during Doppler mode imaging. Based on a transmission / reception unit capable of transmitting / receiving more than one Doppler auxiliary beam and a reception signal obtained by the transmission / reception unit, a site where the structure exists is detected in the subject, and the Doppler beam in the site where the structure exists And an arithmetic unit that calculates a motion velocity vector of a structure at a position where the Doppler auxiliary beam intersects.

  In order to achieve the above object, according to the present invention, there is provided an ultrasonic imaging method in an ultrasonic diagnostic apparatus, wherein the ultrasonic diagnostic apparatus uses a probe that transmits / receives ultrasonic waves to / from a subject. One or more Doppler auxiliary beams are transmitted / received in a direction different from the Doppler beam transmitted / received at the time of mode imaging, and a site where the structure exists in the subject is detected based on the obtained reception signal, and the structure exists. Provided is an ultrasonic imaging method for calculating a motion velocity vector of a structure at a position where a Doppler beam and a Doppler auxiliary beam intersect at a site.

  According to the present invention, real-time processing is possible, and a two-dimensional velocity vector of a structure such as a vascular tissue can be calculated with high accuracy simultaneously with blood flow information.

1 is a block diagram illustrating a configuration example of an ultrasonic diagnostic apparatus according to Embodiment 1. FIG. Functional explanatory drawing of the tissue velocity calculating part based on Example 1. FIG. 1 is a schematic diagram illustrating an outline of an ultrasonic imaging method according to Embodiment 1. FIG. The figure for demonstrating the Doppler and Doppler auxiliary beam transmission method based on Example 1. FIG. The figure for demonstrating the other Doppler and Doppler auxiliary beam transmission methods based on Example 1. FIG. The figure which shows the transmission waveform of the other Doppler and Doppler auxiliary beam transmission methods based on Example 1. FIG. The figure which shows the frequency characteristic of the other Doppler doppler auxiliary beam transmission method based on Example 1. FIG. FIG. 3 is a schematic diagram relating to calculation unit designation according to the first embodiment. 6 is a diagram for explaining an example of a vector calculation method at an intersection of Doppler and Doppler auxiliary beams according to Embodiment 1. FIG. FIG. 3 is a schematic diagram of a tissue motion detection method using a Doppler beam according to the first embodiment. FIG. 3 is a schematic diagram of a tissue motion detection method using an ultrasonic tomogram according to the first embodiment. FIG. 3 is a diagram illustrating an example of a tissue vector calculation method by sequential calculation according to the first embodiment. FIG. 3 is a diagram illustrating an example of a tissue vector calculation method using interpolation according to the first embodiment. FIG. 3 is a comparison diagram of time taken to acquire one frame according to the first embodiment. The schematic diagram of the velocity detection method of the inner membrane, the inner membrane, and the outer membrane based on Example 2. FIG. The model enlarged view of the velocity detection method of the inner membrane, the inner membrane, and the outer membrane based on Example 2. FIG. FIG. 3 is a diagram illustrating an example of a display method of an ultrasonic diagnostic apparatus according to Examples 1 and 2.

  Hereinafter, various preferred embodiments according to the present invention will be described with reference to the drawings. Examples described below show examples of typical embodiments, and the scope of the present invention is not construed to be narrow.

  In the first embodiment, at the time of Doppler mode imaging, one or more Doppler auxiliary beams are transmitted / received in a direction different from the Doppler transmission / reception beam, and a region where a structure exists is detected based on the received data. An ultrasonic diagnostic apparatus for calculating and displaying a motion velocity vector of a structure at a position where a beam in two directions intersects at a position where the structure exists using information obtained from two-direction Doppler data. This is an example. That is, this embodiment is an ultrasonic diagnostic apparatus that uses a probe that transmits / receives ultrasonic waves to / from a subject and has one or more Doppler auxiliary beams in a direction different from the Doppler beam transmitted / received during Doppler mode imaging. Based on the transmission / reception unit capable of transmitting / receiving and the received signal obtained by the transmission / reception unit, the part where the structure exists in the subject is detected, and the Doppler beam and the Doppler auxiliary beam intersect at the part where the structure exists. 1 is an example of an ultrasonic diagnostic apparatus and an ultrasonic imaging method including a calculation unit that calculates a motion velocity vector of a structure at a position to be moved.

  First, an outline of an imaging method using the ultrasonic diagnostic apparatus of the present embodiment will be described using the schematic diagram of the ultrasonic diagnostic image of FIG. In FIG. 3, an ultrasonic diagnostic image obtained by imaging a blood vessel parallel to the probe using a linear probe as a probe for transmitting and receiving ultrasonic waves is used as an example, but this embodiment is limited to such applications. Rather, as a probe for transmitting and receiving ultrasound, using probes of other shapes such as sectors and convexes, imaging and targeting all organs such as blood vessels, heart and digestive organs that can be imaged by ultrasound To do.

  When imaging a blood vessel parallel to a probe using a linear probe, the Doppler beam 31 performs steering at an arbitrary angle. At this time, only the movement in the direction parallel to the ultrasonic transmission / reception beam from the probe is obtained from the Doppler data. Next, the Doppler auxiliary beam is irradiated from another angle. Although one Doppler auxiliary beam 32 is illustrated as an example, the Doppler auxiliary beam 32 overlaps the Doppler beam. As the Doppler auxiliary beam, at least one ultrasonic transmission / reception beam is used, but preferably 1 to 3 ultrasonic transmission / reception beams are used.

Although not shown in the drawing, the Doppler beam 31 is an aggregate of scanning lines similar to the Doppler auxiliary beam 32, and these many Doppler beams 31 intersect with the Doppler auxiliary beam 32. Of the intersecting points, a portion corresponding to the blood vessel wall 33 is determined by detecting the location of the wall, and obtained from the Doppler data in two directions at the intersecting intersections 35 and 36 (shown by black squares in the figure). Using the obtained information, the motion velocity vector (v _x , v _y ) of the part is calculated. In the figure, reference numeral 34 denotes a blood vessel lumen.

  FIG. 1 shows a block diagram of a configuration example of the ultrasonic diagnostic apparatus of this embodiment. The apparatus includes an ultrasonic diagnostic apparatus main body 1, an input unit 24, a probe 3 that transmits and receives ultrasonic waves to and from the subject 2, and a display unit 23.

  A digital analog (D / A) in which the transmission pulse electrical signal from the transmission circuit 4 for generating an ultrasonic signal is not shown in the figure for the probe 3 that transmits and receives the ultrasonic wave placed on the body surface of the subject 2 It is sent to the probe 3 through the converter. The electrical signal input to the probe 3 is converted from an electrical signal to an acoustic signal by a ceramic element installed therein and transmitted to the subject 2. Transmission is performed by a plurality of ceramic elements, and each element is subjected to a predetermined time delay so as to converge at a predetermined depth in the inspection object.

  The acoustic signal reflected in the process of propagating through the inside of the inspection object is received again by the probe 3, converted into an electric signal contrary to the time of transmission, and passed through an analog / digital (A / D) converter (not shown). It is sent as reception data to a reception circuit 5 that generates RF data from the received ultrasonic reception signal. The receiving circuit 5 performs addition processing in consideration of the time delay applied at the time of transmission on signals received by a plurality of elements, and after processing such as attenuation correction, is sent to the quadrature detection unit 8 as RF data. .

  Transmission / reception switching is controlled by the transmission / reception sequence control unit 6. The transmission / reception sequence control unit 6 switches between the tomographic image beam and the Doppler mode. That is, the transmission / reception sequence control unit 6 includes a Doppler / Doppler auxiliary beam transmission / reception sequence control unit 7 that performs transmission / reception switching control of the Doppler beam and the Doppler auxiliary beam. The Doppler / Doppler auxiliary beam transmission / reception sequence control unit 7 performs switching of the Doppler / Doppler auxiliary beam, control of the order, and setting of the steer angle as the Doppler irradiation angle. The steer angle of the Doppler beam and the irradiation target area can be arbitrarily set by the user through the input unit 24. Similarly, the steer angle and irradiation position of the Doppler auxiliary beam can be arbitrarily set by the user. Alternatively, a mechanism for automatically setting the steer angle and irradiation position of the Doppler beam based on the steer angle and position of the Doppler beam set and stored in advance is provided.

The Doppler / Doppler auxiliary beam transmission / reception sequence control unit 7 in the transmission / reception sequence control unit 6 has a mechanism for switching the number of Doppler auxiliary beams. Further, the blood flow / tissue transmission / reception sequence control unit 27 in the transmission / reception sequence control unit 3 switches a sequence suitable for simultaneously acquiring the blood flow and the structure signal in both the Doppler beam and the Doppler auxiliary beam. Details of a suitable sequence will be described later with reference to FIGS.
The Doppler / Doppler auxiliary beam transmission / reception sequence control unit 7 includes a feedback mechanism 26, and changes the position of the auxiliary beam to an appropriate position in response to the calculation result of the subsequent stage. The feedback mechanism 26 is not necessarily a necessary configuration for realizing the present embodiment. In this specification, the transmission circuit 4, the reception circuit 5, and the transmission / reception sequence control unit 6 are collectively referred to as a transmission / reception unit.

  The RF data sent from the transmission / reception unit to the quadrature detection unit 8 is subjected to quadrature detection of the RF data based on transmission / reception parameters or values arbitrarily set by the input unit 24 to form complex Base Band data. To the arithmetic processing unit. That is, the complex base band data of the Doppler beam is sent to the Doppler calculation unit 9, the complex Base Band data of the Doppler auxiliary beam is sent to the Doppler auxiliary beam calculation unit 12, and the complex Base Band data of the tomographic image is sent to the tomographic image calculation unit 15. In this specification, the Doppler calculation unit 9, the Doppler auxiliary beam calculation unit 12, the tomographic image calculation unit 15, the memory unit 25, the tissue velocity calculation unit 16, and the blood flow vector calculation shown in the subsequent stage of the orthogonal detection unit 8 are shown. The unit 21 and the display image generation unit 22 are collectively referred to as a calculation unit.

  In the configuration of the calculation unit in the ultrasonic diagnostic apparatus main body 1, the processing of the calculation unit preceding the memory unit 25, that is, the Doppler calculation unit 9, the Doppler auxiliary beam calculation unit 12, and the tomographic image calculation unit 15 are dedicated. Either hardware processing or software processing using a computer configuration including a central processing unit (CPU) (not shown) and a memory unit installed in the apparatus main body 1 can be realized. The processing of the calculation unit subsequent to the memory unit 25, that is, the processing of the tissue velocity calculation unit 16, the blood flow vector calculation unit 21, and the display image generation unit 22, preferably takes out data from the memory unit 25, This is realized by CPU program processing.

  Now, the Doppler calculation unit 9 has a blood flow velocity calculation unit 10 and a tissue velocity calculation unit 11, and from the complex Base Band data calculated from the Doppler beam, the Doppler velocity, power, and dispersion in the direction parallel to the beam are obtained by the conventional method. Calculate and transmit to the memory unit 25.

  The blood flow velocity calculation unit 10 calculates the blood flow movement from the Doppler beam. After a filter process that removes motion components other than blood flow is performed by a filter processing unit (not shown), a complex autocorrelation process is performed by a complex correlator (not shown). The filter is mainly intended to remove acoustic components derived from the structure, and is defined by the signal intensity, frequency, and the like. In complex autocorrelation processing, phase analysis by Doppler shift is performed. Using the data, average Doppler velocity calculation, dispersion calculation, and power calculation are performed. In blood flow detection, in order to detect the movement of blood cells, it is common to perform Doppler beam transmission / reception (multiple packet transmissions) at the same location multiple times and perform addition processing. It is included in the flow velocity calculation unit 10.

  The tissue velocity calculation unit 11 calculates the tissue movement from the Doppler beam. The outline has a mechanism equivalent to that of the blood flow velocity calculation unit 10, but the filter processing is improved so as to leave the tissue movement and remove the blood flow component. Although less than the blood flow velocity calculation, complex autocorrelation processing is performed in the same manner as the blood flow velocity calculation unit 10 based on the transmission data twice or more.

  Based on the average Doppler velocity, power, and variance information of the tissue calculated by the tissue velocity calculator 11, the Doppler calculator 9 can further filter the calculation result of the blood flow velocity calculator 10. .

  Similar to the Doppler calculation unit 9, the Doppler auxiliary beam calculation unit 14 includes a blood flow velocity calculation unit 13 and a tissue velocity calculation unit 14. From the complex Base Band data calculated from the Doppler beam, the Doppler auxiliary beam calculation unit 14 is parallel to the beam by a conventional method. The average Doppler speed, power, and variance are calculated and transmitted to the memory unit 25. In the Doppler auxiliary beam calculation unit 14, the blood flow velocity calculation unit 13 and the tissue velocity calculation unit 14 are roughly the same as the Doppler calculation unit 9, the blood flow velocity calculation unit 10, and the tissue velocity calculation unit 11.

  The tomographic image calculation unit 15 calculates the amplitude value of the signal from the complex base band data calculated from the tomographic image beam, and based on the amplitude information, it is a popular ultrasonic diagnostic apparatus such as gain control and logarithmic compression. A generally used post-process process is performed, and a tomographic image indicating the form information inside the inspection object is generated and sent to the memory unit 25.

  The Doppler data, Doppler auxiliary beam data, and tomographic image data stored in the memory unit 25 are, among the image data finally displayed on the display unit 23, element data of a specific line along the ultrasonic transmission / reception direction. Become. By transmitting / receiving ultrasonic waves to / from the inspection object by sequentially switching in the arrangement direction of the ceramic elements constituting the probe 2, it is acquired as all received data that is a component of the image data.

  The tissue velocity calculation unit 16 includes a calculation unit designation mechanism 17, a tissue intersection vector calculation unit 18, a tissue motion detection unit 19, and a tissue vector calculation unit 20. The Doppler beam stored in the memory unit 25, the Doppler auxiliary beam, and in some cases. Using the data for one frame of the tomographic image information, the tissue velocity vector is calculated and sent to the blood flow vector calculation unit 21 or the display image generation unit 22.

  First, the function of the tissue velocity calculation unit 16 in the configuration of the ultrasonic diagnostic apparatus of the present embodiment will be described using the functional explanatory diagram of FIG. First, the boundary of a structure such as a vascular tissue is detected from the data given from the memory unit 25 (f1). After detecting the boundary line between the structure and the blood flow, first, the intersection position of the Doppler beam and the Doppler auxiliary beam on the boundary line is detected, and the calculation position is assigned (f2). Using the tissue Doppler velocity obtained from the Doppler beams irradiated from two different angles at the position assigned by f2, the two-dimensional motion velocity at the tissue intersection is calculated (f3). In parallel with f2 and f3, a motion in a direction parallel to the beam on the boundary line of the structure detected at f1 from the Doppler beam or tomographic image information is detected (f4). Based on these, a two-dimensional vector of the entire structure boundary is finally calculated (f5).

  2, f1 and f2 are calculated by the calculation unit designating mechanism 17 in FIG. 1, f3 is calculated by the tissue intersection vector calculating unit 18 in FIG. 1, and f4 is calculated by the tissue motion detecting unit 19 in FIG. f5 is performed by the tissue vector calculation unit 20 in FIG. Detailed methods for these functions will be described later with reference to FIGS.

  The blood flow vector calculation unit 21 uses the tissue motion vector information such as the tissue velocity vector sent from the tissue velocity calculation unit 16 and the information of the Doppler beam and the Doppler auxiliary beam calculation unit sent from the memory unit 25, and This is a mechanism for calculating a blood flow vector using a method. In the realization of the present embodiment, the blood flow vector calculation unit 21 is not necessarily required.

  The display image generation unit 22 generates image data so that the tissue vector information generated so far is superimposed on any or all of ultrasonic tomographic information, Doppler velocity information, and blood flow vector information. . Although not shown in the figure, a scan converter is provided, pixel composition of data to be displayed is performed, a two-dimensional image showing the entire inspection object is reconstructed and displayed on the screen of the display unit 23. That is, the display unit 23 can display the motion velocity vector of the obtained structure superimposed on the blood flow information obtained by the Doppler beam and the tomographic image information obtained by the tomographic image data.

  In the configuration of the ultrasonic diagnostic apparatus according to the present embodiment shown in FIG. 1, the processes subsequent to the memory unit 25, that is, the processes of the tissue velocity calculation unit 16, the blood flow vector calculation unit 21, and the display image generation unit 22 are Instead of the computer configuration in the main body 1, data can be extracted from the memory unit 25, and can be separately realized by offline program processing using a normal computer configuration including a CPU and a memory unit.

  Next, details of a suitable sequence for simultaneously acquiring a blood flow-derived Doppler signal and a tissue-derived Doppler signal will be described with reference to FIGS.

  First, the principle of color Doppler imaging in ultrasound will be described. Color Doppler imaging utilizes the phenomenon that the received pulse signal deviates on the time axis because the distance from the probe to the object changes depending on the movement of the object when an ultrasonic pulse is applied to the object. Considering a certain point on the time axis, this amount of movement is captured by the rotation of the phase. Using this phenomenon, color Doppler imaging is performed by analyzing the phase from the difference in the amount of phase rotation between a plurality of transmission / reception Doppler signals, estimating the speed of movement of the object, and imaging it.

  Here, since the phase angle of the signal is used for motion estimation, the maximum flow velocity required is half of the repetitive wave number of the Doppler signal, and the vector phase rotates more than once at a higher speed (folding phenomenon). Therefore, it is necessary to match the frequency at which the pulse repeats to the speed of the object to be measured. This is a problem because the target velocity is greatly different between blood flow and tissue. For example, in Doppler imaging of an adult carotid artery, the optimal speed range for blood flow is approximately 30-50 cm / sec, whereas the optimal speed range for tissue is 2-5 cm / sec.

  Next, the difference in intensity between blood flow-derived Doppler signals and tissue-derived Doppler signals will be described. Blood flow is the movement of blood cells, but the S / N of the signal from the blood cells is low, so in order to capture the movement of normal blood cells, the signal is sent and received multiple times to the same part, called packet transmission / reception. Do. When the acquisition of information for a plurality of packets is completed, the process moves to the next scanning line and performs the same operation to acquire information for one screen and display a tomographic image. Compared with normal ultrasonic tomographic imaging, the frame rate is reduced by the number of times of transmission / reception of a plurality of packets because the same part is transmitted / received a plurality of times. Furthermore, in order to increase the S / N, although it leads to a decrease in spatial resolution, it is usual that an ultrasonic pulse with a long wavelength is used. On the other hand, since the tissue has a structure such as a fiber tissue and a muscle tissue and the signal S / N is high, an ultrasonic pulse that does not require many packets and has a short wavelength is used.

In view of these, details of a suitable sequence for simultaneously acquiring a blood flow-derived Doppler signal and a tissue-derived Doppler signal will be described. FIG. 4 shows a schematic diagram of an example of a sequence. Each 4 * 8 square in the figure represents one transmission packet, the line number in the scanning direction (Line No.) in the horizontal direction, and the transmission number in each 4 * 8 square. . As shown in the figure, assuming that the number of packets necessary for acquiring blood flow is eight times, all lines are irradiated with ultrasonic waves eight times. The 32 cells are divided into a packet 41 used only for blood flow and a packet 42 used for both tissue and blood flow. Of these, in order to calculate the blood flow velocity, it is possible to change the repetition frequency by the number of packets by using all packets and only the first and last packets 42 in the same line in the tissue signal. is there. That is, when the maximum detection speed is v _max and the number of packets is N, it is expressed as Equation 1.

  In the case of the example in FIG. 4, the velocity range of the tissue is 1/7 of the velocity range of the blood flow.

At this time, the frame rate (FR _CFM ) required for imaging is not changed from that in the case of imaging only the normal blood flow, and is expressed as in Equation 2 in comparison with the tomographic image (FR _B ).

In the case of the method of FIG. 4, in order to use the optimum condition for blood flow with a long pulse, that is, a narrow band, in comparison with the case where imaging is performed using a normal short, that is, a broadband ultrasonic pulse. This degrades the spatial resolution of the tissue. Therefore, the method of FIG. 5 shows a method of transmitting a wide-band tissue packet 52 before and after the narrow-band blood flow packet 51 for each line. Also in this method, the signal is used by thinning out the repetition frequency of the tissue packet 52 so as to be lower than that of the blood flow, and therefore the maximum detection speed v _max is expressed by Equation 3.

  In the example of FIG. 5, the tissue velocity range is 1/9 of the blood flow velocity range.

At this time, the frame rate (FR _CFM ) required for imaging is expressed as shown in Equation 4.

  As a result, it is lower than that in the case of imaging only the normal blood flow, and in the case of FIG.

  As described above, the transmission / reception sequence control unit 6 of the ultrasonic diagnostic apparatus of this embodiment sorts a signal for calculating the movement of a structure such as a tissue and a signal for calculating the movement of a blood flow, The transmission / reception signal for signal acquisition for calculating the motion of a structure such as a tissue is controlled so as to be used by thinning out the transmission / reception signal for signal acquisition for calculating blood flow motion. Further, the transmission / reception sequence control unit 6 transmits / receives a blood flow motion acquisition signal having a narrow band frequency characteristic during transmission / reception of a motion acquisition signal of a structure such as a tissue having a wide band frequency characteristic. Control to do.

  Another example of improving the spatial resolution of the tissue by improving the technique of FIG. The packet transmission method and the usage method are the same as the method in FIG. 4, but the method uses a synthetic pulse of a transmission waveform as shown in FIG. That is, a combined pulse 62 of a narrow-band blood flow ultrasonic pulse and a wide-band tissue ultrasonic pulse is transmitted to and received from one transmission trigger 61. Desirably, within the allowable bandwidth of the probe, wideband pulses are irradiated at higher frequencies and narrowband pulses are irradiated at lower frequencies.

At this time, as shown in the schematic diagram of FIG. 7, the frequency band of the received signal has narrow bands 71 and 72 on the low frequency side and wide bands on the high frequency side. The signal is separated by frequency filtering or the like, and the information of the wide band 72 is used as a tissue signal (f _{tissue in the} figure) and the information of the narrow band 71 is used as a _blood flow signal (f _{blood in the} figure). Therefore, it is possible to optimize the resolution and S / N. That is, the transmission / reception sequence control unit 6 can be configured to perform transmission / reception of pulses having both a wideband frequency characteristic and a narrowband frequency characteristic, and to separate the signal from the received signal according to the frequency characteristic.

  Accordingly, a detailed processing method in the tissue velocity calculation unit 16 of the ultrasonic diagnostic apparatus according to the present embodiment will be described. The tissue velocity calculation unit 16 calculates the one-dimensional velocity information in the direction parallel to the Doppler beam or the scanning beam of the entire structure such as the tissue using the Doppler beam or the tomographic image data, and the obtained one-dimensional velocity information; A structure for calculating the motion speed vector of the entire structure using the motion speed vector of the structure at the intersecting position is provided. Therefore, first, the calculation unit designation mechanism 17 detects the boundary of a structure such as a tissue. This structure boundary detection method is a method that is performed manually, for example, a method that uses designation information when an operator of the apparatus designates a region of interest on an image displayed on the display unit 23 via the input unit 24. can give.

  As a method for automatically detecting a boundary, there is a method using tomographic image data, for example, a method for performing recognition by setting a threshold value based on luminance value information. As another example, the boundary between blood flow and tissue is automatically detected using a boundary recognition algorithm such as Snake. At this time, a filter for extracting a target tissue shape such as a morphology filter may be used. Further, the boundary detection may be performed after processing such as binarization and ternarization according to the luminance value.

  As another method for automatically detecting the boundary, there is a method using luminance value information / frequency band information of Doppler beam, that is, blood flow Doppler velocity and tissue Doppler velocity information calculated from the Doppler beam. As an example, an intermediate point between a place where a blood flow Doppler velocity exists and a place where a tissue Doppler velocity exists is recognized as a boundary. Alternatively, a structure may be defined by providing a threshold for the tissue Doppler velocity power.

  As described above, the calculation unit designating mechanism 17 first detects a site where a structure such as a tissue exists based on the luminance value information of the tomographic image data or the luminance value information / frequency band information of the Doppler beam, and then the Doppler beam. And the position where the Doppler auxiliary beam intersects.

  That is, after defining the boundary of the structure, the intersection position of the Doppler beam and the Doppler auxiliary beam on the boundary line is detected, and the calculation position is assigned. In the example of the schematic diagram of FIG. 8, the intersections 85 and 86 between the Doppler auxiliary beam 82 and the boundary 87 of the blood vessel front wall 83 and rear wall 84, which are structural bodies, correspond to the 19th line of the Doppler 81 and 8 respectively. Is the second line. Once the distance in the beam direction that intersects the line to be used is defined, the tissue intersection vector calculation unit 18 uses the tissue Doppler velocity information at that location to determine the two-dimensional velocity vector at the intersections 85 and 86 (shown as black squares in the figure). Perform the operation.

  FIG. 9 shows an enlarged view of the intersection portion represented by the black square in FIG. As shown in the figure, the tissue intersection vector calculation unit 18 calculates the intersection point based on the combined vector of the Doppler velocity vector 91 in the direction of the 19th line of the Doppler 81 and the Doppler auxiliary beam velocity vector 92 in the direction of the Doppler auxiliary beam 82. A two-dimensional velocity vector 93 at 85 can be obtained.

  In the ultrasonic diagnostic apparatus of the present embodiment, in parallel with the vector calculation at the intersection described above, or as the next step, the tissue motion detection unit 19 in FIG. 1 moves from the Doppler beam or tomographic image information onto the boundary line. The motion of a structure such as an existing tissue in the direction parallel to the Doppler beam 81 is detected.

  FIG. 10 shows a schematic diagram of the structure motion detection method when the Doppler beam 81 is used. Since the tissue velocity calculation unit 11 of the Doppler calculation unit 9 has already calculated the tissue Doppler velocity information, a portion corresponding to the boundary 87 of the structure such as the front wall 83 and the rear wall 84 of the blood vessel is included in the information. By only detecting, it is possible to detect the motion vectors 101 and 102 in the direction parallel to the Doppler beam, which is one-dimensional velocity information.

  FIG. 11 shows a schematic diagram of a tissue motion detection method using a tomographic image instead of a Doppler beam. There are several methods for detecting motion that is one-dimensional velocity information of the boundary 112 of the structure such as the front wall 113 and the rear wall 114, but most simply, the tissue motion detection unit 19 is a tomographic image calculation unit. 15 is used to detect the boundary 112 between the anterior wall 113 and the posterior wall 114 of the blood vessel using luminance information for each scanning line (scanning beam) 111 of the tomogram obtained in step 15, and to detect the boundary for each frame by a method such as an autocorrelation method. By detecting the motion vectors 115 and 116 of 112, there is a method for calculating the motion as the unified velocity information.

  Next, the tissue vector calculation unit 20 in FIG. 1 uses the two-dimensional vector at the intersection of the Doppler beam and the Doppler auxiliary beam existing on the boundary surface of the structure, and velocity information in the direction parallel to the beam on the boundary surface of the structure. Thus, the calculation for finally calculating the two-dimensional velocity vector of the entire structure boundary is performed by one of the following methods.

  First, an example using a correction coefficient will be described as a first method for obtaining a two-dimensional velocity vector of the boundary surface of a structure. As a first step, the motion ratio (correction coefficient) in the azimuth direction with respect to the motion in the beam direction is calculated based on a vector obtained by calculating at the beam intersection. That is, with respect to the one-dimensional velocity information of the entire structure, the motion ratio in the vertical direction of the structure with respect to the direction parallel to the Doppler beam or the scanning beam is calculated from the motion velocity vector of the structure at the intersecting position.

  In the example of FIG. 10, the ratio of the velocity in the vertical direction to the velocity in the direction parallel to the Doppler beam 81 is shown. In the example of FIG. 11, the velocity in the vertical direction with respect to the velocity in the direction parallel to the tomographic image and the scanning line (scanning beam) 111 is shown. The ratio is calculated as a correction factor. As a second step, it is assumed that the motion of the structure within a certain frame is equivalent, and using the above correction factor, the velocity in the direction perpendicular to the beams 81 and 111 at all points is calculated, The two-dimensional velocity vector of the boundary of the structure is calculated from the velocity of That is, using the obtained motion ratio, the motion speed vector of the entire structure is calculated from the one-dimensional speed information of the entire structure.

  Note that the motion ratio (correction coefficient) given by this method is the long axis for the movement of the circular tube in the short axis direction, particularly when the target is a blood vessel parallel to the imaging surface or a circular tube tissue such as the intestine. It is an indicator of the rate of movement in the direction. In the ultrasonic diagnostic apparatus according to the present embodiment, the image generation by the display image generation unit 22 can be separately presented to the user using the display unit 23 or the like as an index such as a motion ratio as a numerical value or an index.

  FIG. 12 shows a schematic diagram of another example of a method for obtaining a two-dimensional velocity vector of the boundary surface of the structure in the present embodiment. The tissue vector calculation unit 20 sequentially calculates the motion velocity vector of the entire structure using the one-dimensional velocity information of the entire structure, starting from the motion velocity vector of the structure at the intersecting position. In other words, in this method, the two-dimensional velocity vector obtained by the tissue intersection vector calculating unit 18 is used as a starting point, and the two-dimensional velocity vector is sequentially calculated using a mass conservation law or the like. In the figure, A and B corresponding to the intersections 85 and 86 on the boundary 87 of the front wall 83 and the rear wall 84 in FIG. 8 are the calculation start points 88, and sequentially to the right and left along the structure boundary surface, respectively. Calculate. The amount of change in velocity in the direction parallel to the Doppler beam at a point next to the calculation start point 88 is known. In the following, assuming that the law of conservation of mass in two dimensions holds, the amount of change in velocity in the direction perpendicular to the Doppler beam is the same as the amount of change in velocity in the direction parallel to the Doppler beam, so it is parallel to the Doppler beam at the adjacent point. The amount of change in the direction velocity is obtained, and the amount of change is added to the velocity in the direction perpendicular to the Doppler beam at the starting point to obtain the velocity in the direction perpendicular to the Doppler beam at that position. Thus, the two-dimensional velocity vector of the whole structure can be obtained by obtaining the vertical velocity while sequentially accumulating.

  FIG. 13 shows an example of a tissue vector calculation method by interpolation in the tissue vector calculation unit 20 of the present embodiment. The tissue vector calculation unit 20 calculates the motion velocity vector of the entire structure by interpolation and extrapolation by interpolation of the motion velocity vector of the structure at the intersecting position. This method is particularly useful when one or more Doppler auxiliary beams are used. In the example of FIG. 13, with respect to three Doppler auxiliary beams, two-dimensional velocity vectors are represented by tissue intersection vector calculation units at intersections 85 and 86 represented by three black squares on the front wall 83 and the rear wall 84, respectively. It is determined at 18. Then, the wall speed is estimated by interpolation (interpolation) using a fitting function or the like using these three intersections 85 and 86 as a reference, and calculation is performed by interpolation and extrapolation. A portion obtained by the interpolation and extrapolation is shown by a black circle 131. As an example of this interpolation, a method using the above-described correction coefficient, that is, the ratio of the velocity in the direction perpendicular to the Doppler beam to the velocity in the direction parallel to the Doppler beam is given as an example. In this method, first, a correction coefficient at each measurement point is obtained using a fitting function or the like. In addition, each component in the beam vertical direction is calculated using the correction coefficient at each measurement point calculated after interpolation.

  Another interpolation method example will be described. In the case of interpolation, the distance between the intersection positions of each auxiliary beam and the Doppler beam is calculated at a measurement point (black circle 131 in the figure) when surrounded by two intersection positions, and weighting is performed according to the distance. The velocity in the vertical direction is calculated from the velocity in the direction parallel to the Doppler beam at each measurement point while changing the reflection ratio of the correction coefficient calculated at the intersection position according to the weighting. When extrapolating, the velocity in the vertical direction is calculated using the correction coefficient of the nearest intersection position.

  According to the present embodiment described in detail above, it is possible to calculate a two-dimensional velocity vector of a structure such as a tissue without irradiating the Doppler beam twice. FIG. 14 shows a method of irradiating a Doppler beam twice, a method using both a Doppler beam and a Doppler auxiliary beam according to this embodiment, normal Doppler imaging (single Doppler beam irradiation method), and acquisition of one frame from an ultrasonic tomographic image. A comparison of the time taken for. In the figure, the vertical axis indicates the time (ms) required to acquire one frame. This figure was calculated on the assumption that the pulse transmission repetition frequency was 8 kHz, the tomographic image was 128 scans per frame, the Doppler was 64 scans per frame, 8 packets were transmitted, and three auxiliary beams were irradiated.

  As is apparent from FIG. 14, in the case of two Doppler transmissions, it takes 80% more time than the one Doppler transmission (that is, the frame rate is reduced by 45%). On the other hand, when the Doppler beam and the Doppler auxiliary beam of this embodiment are used together, the time increase is 4% (that is, the frame rate is 4% lower), and the frame rate of this method is one-way that is normal Doppler imaging. It can be said that it is equivalent to the Doppler mode.

  Further, according to the configuration of the present embodiment, as shown in FIGS. 3, 10, 12 and the like, the target area that can be calculated with respect to the viewing angle is equivalent to the conventional unidirectional Doppler mode. Furthermore, according to the calculation method using the tomographic image shown in FIG. 11, the viewing angle is equivalent to that of the tomographic image, which is improved as compared with the conventional one-way Doppler mode.

FIG. 17 shows an example of a display method in the ultrasonic diagnostic apparatus of this embodiment. By the above-described method, the display image generation unit 22 of the ultrasonic diagnostic apparatus causes the obtained motion velocity vector (arrow 171 in the figure) of the structure, blood flow information 173 obtained from the Doppler data, and blood flow velocity color. The bar 174 and the tomographic image information are superimposed and displayed as shown in FIG. Furthermore, the display image generation unit 22 displays the above-described vertical motion ratio of the structure with respect to the beam parallel direction as a slip index 172 or the like (XX in the figure). The slip index 172 can be calculated by the following equation using the velocity at the intersection of the auxiliary beam and the Doppler beam.
Slip index = velocity in the direction perpendicular to the beam / velocity in the direction parallel to the beam Although illustration is omitted, the slip image 172 is superimposed on the above-described tomographic image information by the display image generation unit 22 as a new color map. Can also be displayed.

  According to the present embodiment, real-time processing is possible without reducing the frame rate and viewing angle, and the two-dimensional velocity vector of a structure such as a vascular tissue is calculated and displayed with high accuracy simultaneously with blood flow information. It is possible to provide an ultrasonic diagnostic apparatus capable of performing the above.

  Example 2 is an example of an ultrasonic diagnostic apparatus capable of detecting and displaying a motion ratio of a structure having a layer structure. In this embodiment, the structure described in the first embodiment is a blood vessel wall, and the arithmetic unit recognizes the intima and the outer membrane of the blood vessel wall when detecting a site where the structure exists in the subject. In this embodiment, the position where the Doppler beam and the Doppler auxiliary beam intersect is specified for each of the locations of the intima and outer membrane, and the motion velocity vector is calculated at each intersecting position.

  The speed detection method for the inner membrane, outer membrane and the like in the ultrasonic diagnostic apparatus of this embodiment will be described with reference to FIG. If this method is used, it is possible to detect the motion ratio of the intima to the outer membrane. In this embodiment, the intima and adventitia in the blood vessel wall such as the carotid artery are targeted. However, the target site is not limited to this, and all layers that can be visualized by the ultrasonic diagnostic apparatus are not limited to this. Applicable to tissues and structures. The configuration of the ultrasonic diagnostic apparatus of the present embodiment is the same as that shown in FIG.

  In the example of FIG. 15, an inner membrane 151, a middle membrane 152, and an outer membrane 153 are depicted on the rear wall 84. The Doppler beam 81 and the Doppler auxiliary beam 82 pass through all these layers. FIG. 16 shows an enlarged view of a portion surrounded by a thick black dotted line in FIG. In this figure, the fourth Doppler beam 81 intersects the Doppler auxiliary beam 82 at the intersections 154 and 155 in the inner film 151 and the second Doppler beam 81 in the outer film 153. The positions of the inner membrane 151 and the outer membrane 153 are detected by the calculation unit designating mechanism 17, and the intersection beam numbers and the intersection positions of the intersection points 154 and 155 are assigned. Then, the tissue intersection vector calculation unit 18 performs one auxiliary beam. The two-dimensional velocity vectors of the inner membrane 151 and the outer membrane 153 are calculated from 82. Then, by calculating these ratios, for example, an indicator such as the amount of movement of the intima 151 with respect to the movement of the outer membrane 153 or a mechanism for presenting a numerical value of the amount of movement to the operator is provided. These indexes and numerical values are obtained by converting the movements of the intima and outer membrane of the blood vessel wall into numerical values like the slip index shown in FIG. 17 described in the first embodiment, and the display image generator 22 displays the display 23. Can be displayed.

  As described above, according to the present embodiment, when the tissue velocity calculation unit 16 detects a site where a structure that is a blood vessel wall exists in the subject, the tissue velocity calculation unit 16 detects the intima, media, or outer membrane of the blood vessel wall. A blood vessel having a layered structure is identified, the position where the Doppler beam and the Doppler auxiliary beam intersect is specified for each location of the intima, media, or outer membrane, and the motion velocity vector is calculated from the information of each intersecting position. It is possible to detect and display the motion ratio of a structure such as a wall.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Further, the above-described configuration, function, processing unit, and the like have been described as an example of creating a program that realizes part or all of them. Needless to say, it can be realized with this.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Subject 3 Probe 4 Transmission circuit 5 Reception circuit 6 Transmission / reception sequence control unit 7 Doppler / Doppler auxiliary beam transmission / reception sequence control unit 8 Orthogonal detection unit 9 Doppler calculation units 10, 13 Blood flow velocity calculation unit 11, 14 Tissue velocity calculation unit 12 Doppler auxiliary beam calculation unit 15 Tomographic image calculation unit 16 Tissue velocity calculation unit 17 Calculation unit designation mechanism 18 Tissue intersection vector calculation unit 19 Tissue motion detection unit 20 Tissue vector calculation unit 21 Blood flow vector calculation unit 22 Display Image generating unit 23 Display unit 24 Input unit 25 Memory unit 26 Feedback mechanism 27 Blood flow / tissue transmission / reception sequence control unit 31, 81 Doppler beam 32, 82 Doppler auxiliary beam 33 Blood vessel wall 34 Blood vessel lumen 35, 85, 86 Intersection 83 Blood vessel Anterior wall 84 Rear wall 87 of blood vessel Structure boundary 91 Doppler velocity vector 92 Doppler assist Over-time velocity vector 93 2-dimensional velocity vector

Claims (15)

An ultrasound diagnostic apparatus,
A transmitter / receiver capable of transmitting / receiving one or more Doppler auxiliary beams in a direction different from a Doppler beam transmitted / received at the time of Doppler mode imaging using a probe that transmits / receives ultrasonic waves to / from a subject;
Based on the received signal obtained by the transmission / reception unit, a part where a structure exists in the subject is detected, and the structure at a position where the Doppler beam and the Doppler auxiliary beam intersect at a part where the structure exists An arithmetic unit that calculates a motion velocity vector of
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The computing unit is
Using the Doppler beam or tomographic image data, calculating one-dimensional velocity information parallel to the Doppler beam or scanning beam of the entire structure,
Using the obtained one-dimensional velocity information and the velocity vector of the structure at the intersecting position, calculate the velocity vector of the entire structure.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The computing unit is
For the one-dimensional velocity information of the entire structure, the vertical motion ratio of the structure with respect to the parallel direction of the Doppler beam or the scanning beam is obtained from the motion velocity vector of the structure at the intersecting position. Operate,
Using the obtained motion ratio, the motion velocity vector of the entire structure is calculated from the one-dimensional velocity information of the entire structure.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The computing unit is
Calculating the motion velocity vector of the entire structure by interpolation and extrapolation by interpolation of the motion velocity vector of the structure at the intersecting position;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The computing unit is
Using the motion velocity vector of the structure at the intersecting position as a starting point, the motion velocity vector of the entire structure is sequentially calculated using the one-dimensional velocity information of the entire structure.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The transmission / reception unit includes a transmission / reception sequence control unit,
The transmission / reception sequence control unit performs transmission / reception switching control of the Doppler beam and the Doppler auxiliary beam.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 6,
The transmission / reception sequence control unit
The received signal is divided into a signal for calculating the movement of the structure and a signal for calculating the movement of blood flow,
The signal transmission / reception signal for calculating the motion of the structure is used by thinning out the signal acquisition / transmission signal for calculating the blood flow motion,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 6,
The transmission / reception sequence control unit
Sending / receiving the blood flow motion acquisition transmission / reception signal having a narrow-band frequency characteristic during the transmission / reception signal transmission / reception signal acquisition of the structure having a broadband frequency characteristic,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The computing unit is
A position where the structure is present in the subject based on the luminance value information / frequency band information of the Doppler beam or the luminance value information of the tomographic image data, and a position where the Doppler beam and the Doppler auxiliary beam intersect Identify
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The structure is a blood vessel wall;
The computing unit is
When detecting the site where the structure is present in the subject, the inner membrane and outer membrane of the blood vessel wall are recognized, and the position where the Doppler beam and the Doppler auxiliary beam intersect is determined by the inner membrane and the outer membrane. Identify for each location and calculate the velocity vector at each of the intersecting positions;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3,
A display unit;
The display unit displays the movement ratio in numerical form;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 9,
A display unit;
The display unit displays the obtained motion velocity vector of the structure superimposed on the blood flow information obtained by the Doppler beam and the tomographic image information obtained by the tomographic image data.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 10,
A display unit;
The display unit displays the movement of each of the intima and outer membrane of the blood vessel wall in numerical form,
An ultrasonic diagnostic apparatus. An ultrasonic imaging method in an ultrasonic diagnostic apparatus,
The ultrasonic diagnostic apparatus comprises:
Using a probe that transmits and receives ultrasound to and from the subject, one or more Doppler auxiliary beams are transmitted and received in a direction different from the Doppler beam transmitted and received during Doppler mode imaging,
Based on the obtained received signal, a part where the structure is present in the subject is detected, and the speed of movement of the structure at the position where the Doppler beam and the Doppler auxiliary beam intersect at the part where the structure is present Calculate the vector,
And an ultrasonic imaging method. The ultrasonic imaging method according to claim 14, comprising:
The ultrasonic diagnostic apparatus comprises:
Using the Doppler beam or tomographic image data, calculating one-dimensional velocity information parallel to the Doppler beam or scanning beam of the entire structure,
Using the obtained one-dimensional velocity information and the velocity vector of the structure at the intersecting position, calculate the velocity vector of the entire structure.
And an ultrasonic imaging method.

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