JP2013102959A - Ultrasonic diagnostic apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the direction of a scanning line of ultrasonic waves to be transmitted/received from an ultrasonic probe accurately and in a short processing time.SOLUTION: Received signals are obtained from at least three grid points (upper grid points B1n and B2n and a lower grid point An) with different depths on ultrasonic scanning lines n and m based on ultrasonic detection signals from the ultrasonic probe, and propagation times between the respective grid points (Δt1, Δt1b, Δt2, Δt2b, etc.) are calculated. The angle between the scanning lines n and m is calculated based on the calculated propagation times.

Description

  The present invention relates to an ultrasonic diagnostic apparatus and method, and in particular, a technique for calculating the ultrasonic scanning line direction and calculating the sound speed (hereinafter referred to as “local sound speed”) in a part (diagnosis site) within a subject with high accuracy. About.

The sound speed V in the subject OBJ1 made of a medium having a constant sound speed can be calculated as follows. As shown in FIG. 13A, when the distance from the reflection point (region) X1 _ROI in the subject OBJ to the ultrasonic probe 300A is L, the reflection is performed after the ultrasonic wave is reflected at the reflection point X1 _ROI. The elapsed time T until reception by the ultrasonic transducer (element) 302A0 immediately below the point X1 _ROI is T = L / V. Assuming that the elapsed time T + ΔT until the element 302Ai located at a distance X away from the element 302A0 in the X direction (the arrangement direction of the element 302A) is T + ΔT, the delay time ΔT between the elements 302A0 and 302Ai is: [Expression 1]

Therefore, by measuring the elapsed time [2T, 2T + ΔT] from when the ultrasonic wave is transmitted and reflected after the time T at the reflection point X1 _ROI until it is received by each element, the reflection point X1 _{ROI is obtained.} The distance L and the speed V can be obtained uniquely.

As described above, when the sound speed in the subject is constant, the sound speed V can be obtained, but when the internal sound speed is not constant as in the subject OBJ2 shown in FIG. In the above method, it is difficult to obtain the distance L to the reflection point (region) X2 _ROI and the sound speeds V and V ′.

  On the other hand, there has been proposed an ultrasonic diagnostic method capable of accurately calculating the local sound speed even when the sound speed in the subject is not constant (Patent Document 1).

  In this ultrasonic diagnostic method, an ultrasonic scanning line is emitted from an ultrasonic probe to a subject at a predetermined interval and reflected by the subject.

  From the received signal obtained by receiving the ultrasonic wave, from the upper lattice point to the ultrasonic probe based on the received signal reflected at the lattice point (upper lattice point) set in the target region on the target scanning line The ambient sound velocity and the reception time, which are the average sound velocity in the region, are calculated, and the reflection at the lattice point (lower lattice point) on each scanning line set between the upper lattice point and the ultrasonic probe is calculated. Based on the received signal, the ambient sound velocity and the reception time, which are the average sound speed of the region from each lower lattice point to the ultrasonic probe, are calculated, while assuming the assumed sound velocity in the region of interest, Calculate the propagation time to the lower grid point.

  Further, based on Snell's law, the incident angle of the ultrasonic wave incident on each lower lattice point from the upper lattice point, the assumed sound velocity of the region of interest and the environmental sound velocity calculated in relation to the reflection at the lower lattice point Then, the emission angle of the ultrasonic wave emitted from each lower lattice point is calculated, and the position of the ultrasonic probe element where the ultrasonic wave emitted from the lower lattice point with the calculated emission angle is incident and incident on the element. Calculate the propagation time until

  Then, the ultrasonic reception time at the position of the element of the ultrasonic probe is calculated by adding the two propagation times, and the ultrasonic reception of the reflection at the calculated reception time and the upper lattice point is calculated. The assumed sound speed is corrected so that the error from the reception time at the position of the child element is minimized, and the corrected assumed sound speed is determined as the local sound speed in the region of interest.

  Patent Document 2 discloses a method for obtaining a sound speed distribution by sequentially determining a local sound speed from a shallow region based on focus accuracy in an ultrasonic image.

  In Patent Document 3, an ultrasonic transmission transducer and a reception transducer are arranged at a predetermined distance from each other, and the received vibration from the transmission transducer is changed while changing the transmission and reception angles of these transducers. Measure the propagation time of the ultrasonic wave to the child, find the error between this measured propagation time and the propagation time of the ultrasonic wave from the transmitting transducer to the receiving transducer calculated separately based on the virtual sound velocity distribution, A method for obtaining the sound speed distribution in the subject by correcting the virtual sound speed distribution so that this error is minimized is disclosed.

JP 2010-99452 A JP 2009-56140 A Japanese Patent Laid-Open No. 5-95946

  In the ultrasonic diagnostic method described in Patent Document 1, the relative spatial position of each lower lattice point set in a shallow region is known with respect to the upper lattice point set in a region of interest as a premise of measuring the local sound speed. Must.

  However, the position of each grid point is defined by the scanning line position and the reception time, and the spatial position is unknown. In contrast, in Patent Document 1, the spatial position of each scanning line is known, and the spatial position is given by approximating the same reception time to the same depth.

  Therefore, when the scanning line direction changes due to refraction, the spatial position of each lattice point changes both in the azimuth direction and in the depth direction, resulting in an error in the calculated local sound speed.

  For example, when the measurement target is the liver, the direction of each scanning line changes due to refraction at the shallower abdominal wall.

  Also in the method described in Patent Document 2, since the focus on the ultrasonic image depends not only on the sound speed but also on refraction, the sound speed distribution cannot be obtained without obtaining refraction.

  The method described in Patent Document 3 has the following problems.

  (1) A dedicated device configuration is required to transmit and receive waves at a desired angle.

  (2) A great deal of processing time is required to search for a large number of transmission / reception times and a virtual sound velocity distribution. Even in order to obtain the sound speed of only the region of interest, there is no change in the need for a large number of transmission / reception times and processing time due to the principle of comparing the measured value with the calculated value as a result of propagation through all other regions. .

  (3) In order to calculate the propagation path, the sound velocity field is given by a model that expands into a linearly approximated triangle. However, the actual sound velocity field is more complicated, and the approximation model as described in Patent Document 3 is used. It is difficult to obtain a solution. Further, even if a model capable of reproducing a complicated sound velocity field is given, it is difficult to obtain a solution from limited transmission / reception data as in the invention described in Patent Document 3.

  The present invention has been made in view of such circumstances, and by using a new means that utilizes the received signals of each element of the ultrasonic probe, the ultrasonic scanning line direction can be accurately and reduced with a normal apparatus configuration. The purpose is to calculate the processing time. It is another object of the present invention to provide an ultrasonic diagnostic apparatus and method that can accurately calculate the speed of sound in a region of interest.

  Scan line direction information is effective in improving the accuracy of any function that requires displacement information in the azimuth direction, such as transverse wave velocity measurement, lateral speckle tracking, and image distortion correction. Also aimed at improvement.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to an aspect of the present invention transmits an ultrasonic wave to a subject, receives an ultrasonic wave reflected by the subject, and outputs an ultrasonic detection signal An ultrasonic probe including a plurality of elements, a reception signal acquisition means for acquiring a reception signal of each reflection from three or more different depths of the ultrasonic wave based on the ultrasonic detection signal, and the acquisition Scanning line direction calculating means for calculating the scanning line direction based on the received signal.

  According to one aspect of the present invention, the position of each reflection point is obtained from the reception signals of each reflection from the three or more different depths, and the scanning line direction is calculated from these positional relationships.

  In the ultrasonic diagnostic apparatus according to another aspect of the present invention, the received signal is a signal received by a plurality of elements of the ultrasonic probe.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the scanning line direction calculation means includes three or more on the first scanning line of interest among the scanning lines transmitted / received from the ultrasonic probe. A propagation time of ultrasonic waves between the lattice points corresponding to different depths and lattice points corresponding to three or more different depths on the second scanning line different from the first scanning line, Propagation time calculating means for calculating based on the received signal acquired by the received signal acquiring means, and a first lattice point among the lattice points corresponding to three or more different depths on the first scanning line as an origin And the second position of the second lattice point on the second scanning line is set to the propagation time calculated by the propagation time calculating means on the first time coordinate with the first scanning line as a reference. First position calculating means for calculating based on the second scanning line and 3 on the second scanning line Of the grid points corresponding to the different depths, the first grid point on the first scan line is set on the second time coordinate with the second grid point as the origin and the second scan line as a reference. The first position of the lattice point is calculated based on the propagation time calculated by the propagation time calculating means, and the second position calculated by the first position calculating means is the origin. The third position of the first lattice point on the first scanning line is calculated by coordinate transformation on the third time coordinate rotated by an arbitrary angle with respect to the first time coordinate. A first position of the first lattice point calculated by the position calculating means, a second position calculating means, and a third position of the first lattice point calculated by the third position calculating means. The rotation angle of the third time coordinate when the error from the position is minimized, And an angle calculating means for calculating as the angle between the second scan line 査線 is characterized in that it consists of.

  According to another aspect of the present invention, a first grid point of grid points corresponding to three or more different depths on the first scan line is set as an origin, and the first scan line is used as a reference. Calculating a second position of the second grid point on the second scan line on the first time coordinate and similarly corresponding to three or more different depths on the second scan line The first position of the first grid point on the first scan line is calculated on the second time coordinate with the second grid point of the points as the origin and the second scan line as a reference. The first lattice point on the first scanning line on the third time coordinate rotated by an arbitrary angle with respect to the first time coordinate with the calculated second position as the origin. A third position is calculated by coordinate conversion, and the calculated first position of the first grid point and the third of the first grid point after the coordinate conversion are calculated. When the error between the position is minimized, and the rotation angle of the third time coordinate calculated as the angle between the first scan line and the second scan line.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the scanning line direction calculation means includes the first scanning line and the second scanning line from n (n: an integer of 3 or more) scanning lines. (N-1) angles are calculated, and the average of these calculated angles is defined as the angle formed by the first scanning line and the second scanning line. Thereby, the calculation accuracy in the scanning line direction can be increased.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the scanning line direction calculation means includes the first scanning line and the second scanning line from n (n: an integer of 3 or more) scanning lines. (N-1) angles are calculated, and an average of these calculated angles is set as an angle formed by the first scanning line and the second scanning line, and the angle on the first scanning line is calculated. The second position of the second grid point on the second scan line is defined as (n−1) on the first time coordinate with the first grid point as the origin and the first scan line as a reference. In this case, the average of these calculated second positions is used as the position of the second grid point of the second scanning line. Thereby, the calculation accuracy in the scanning line direction and the calculation accuracy of the position of each grid point can be increased.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the scanning line direction calculation means includes three or more on the first scanning line of interest among the scanning lines transmitted / received from the ultrasonic probe. The ultrasonic wave propagation time between lattice points corresponding to different depths and second lattice points on a plurality of second scanning lines different from the first scanning line is obtained as the received signal. A propagation time calculating means for calculating based on the received signal obtained by the means, and a first lattice point of lattice points corresponding to three or more different depths on the first scanning line as an origin, and the first Position calculating means for calculating the positions of a plurality of second grid points on the second scanning line based on the propagation time calculated by the propagation time calculating means on a time coordinate with one scanning line as a reference; , A straight line with respect to a curve connecting the positions of the plurality of second lattice points. The direction of a straight line intersecting the is characterized in that the direction of the second scanning lines for the first scan line.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the propagation time calculation means calculates a first propagation time from an upper lattice point on the target scanning line to each element of the ultrasonic probe. A first propagation time calculating means; and a second propagation time from a lower lattice point set in a region between the upper lattice point and the ultrasonic probe to each element of the ultrasonic probe. A time difference on the element that maximizes the time difference between the calculated first propagation time and the second propagation time on each element of the second propagation time calculating means and the ultrasonic probe is calculated. And means for calculating the propagation time of ultrasonic waves from the upper lattice point to the lower lattice point. According to this, the first propagation time from the upper lattice point to each element of the ultrasonic probe and the second propagation time from the lower lattice point to each element of the ultrasonic probe. Based on this, it is possible to easily calculate the propagation time of the ultrasonic wave from the upper lattice point to the lower lattice point.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, an extracting unit that extracts two or more scanning lines having no refraction based on a plurality of scanning line directions calculated by the scanning line direction calculating unit, A distance calculating means for calculating a spatial distance between the two scanning lines by multiplying a time interval between lattice points of the same depth of two or more extracted scanning lines by a predetermined sound velocity; The predetermined sound velocity is calculated so that the scanning line interval at the lattice point of the scanning line having no refraction among the scanning lines transmitted from the ultrasonic probe coincides with the distance calculated by the distance calculating unit. And converting means for converting from the position of each grid point on the time coordinate to the position on the spatial coordinate based on the calculated sound speed.

  Of the scanning lines transmitted from the ultrasonic probe, the scanning line spacing at the lattice points of the scanning lines without refraction is known. For example, when the ultrasonic probe is a linear probe, the scanning line interval is determined by the physical interval between the elements. When the ultrasonic probe is a convex probe, the element interval and the scanning line spread are determined. It can be calculated from the angle and the depth of the lattice points. Then, the interval between the known scanning lines, the time interval between lattice points of the same depth on the extracted two or more scanning lines without refraction, and a predetermined sound speed are multiplied by the above two lines. The predetermined sound speed is determined so that the spatial distance between the scanning lines matches. The position of the grid point on the time coordinate is converted to the position on the space coordinate by the determined sound speed.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, lattice points corresponding to three or more different depths on the first scanning line of interest among scanning lines transmitted and received from the ultrasonic probe. And the propagation time of the ultrasonic wave between each lattice point with the second lattice points on the plurality of second scanning lines different from the first scanning line, based on the reception signal acquired by the reception signal acquisition means The propagation time calculation means for calculating the first scanning line and the first scanning line of three or more different depths on the first scanning line as the origin and the first scanning line as a reference Position calculation means for calculating positions of a plurality of second grid points on the second scanning line on the time coordinates based on the propagation time calculated by the propagation time calculation means, the first grid points, The position of the second grid point on the time coordinate is based on a predetermined sound speed. Coordinate conversion means for converting to a position on the inter-coordinate, and a scanning line corresponding to the first and second scanning lines transmitted from the ultrasonic probe and the same depth on the scanning line before refraction Are connected to the spatial coordinates of the first and second grid points, and the magnitude of the direction change at each end point or the difference in direction change at each end point of the adjacent scanning line Integration means for integrating the magnitudes over all scanning lines, and the predetermined sound speed at which the integration value by the integration means is minimized, and based on the calculated sound speed, space is calculated from the position of each lattice point on the time coordinate. Conversion means for converting the position into a coordinate position.

  The position of a plurality of second grid points on the second scan line is calculated on the time coordinate with the first scan line as a reference, and the time of the first grid point and the second grid point is calculated. The position on the coordinates is converted into a position on the space coordinates based on a predetermined sound speed. On the other hand, the positions of a plurality of end points having the same depth on the scanning line corresponding to the first and second scanning lines before being refracted are known because they are not refracted. Then, the positions of the plurality of end points and the calculated positions of the first and second grid points on the spatial coordinates are connected, the magnitude of the direction change at each end point, or each end point of the adjacent scanning line Integrate the magnitude of the direction change difference in all the scanning lines, obtain a predetermined sound speed when the integrated value is minimum, and based on this sound speed, from the position of each grid point on the time coordinate on the space coordinate The position is converted.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, an upper lattice point set in a region of interest among lattice points corresponding to three or more different depths on the first scanning line of interest; A lower lattice point set between the upper lattice point and the ultrasonic probe and a lower lattice point on a second scanning line different from the first scanning line are represented on the calculated spatial coordinates. Based on the lattice point setting means that is set based on the position of the position and the reception signal of the reflection at the lower lattice point, the environmental sound speed that is the average sound speed of the region from the lower lattice point to the ultrasonic probe is calculated An environmental sound speed calculating means for calculating a first propagation time from the upper lattice point to the lower lattice point, assuming an assumed sound speed in the region of interest, and Snell's law from the upper lattice point to the lower lattice point. The incident angle of the ultrasonic wave incident on the Means for calculating an emission angle of an ultrasonic wave emitted from the lower lattice point based on an environmental sound velocity in a region between the lower lattice point and the ultrasonic probe; and the calculated emission angle from the lower lattice point. Means for calculating the position of the element of the ultrasonic probe to which the ultrasonic wave emitted by the laser beam enters and the second propagation time until it enters the element, and the superposition at the position of the element of the ultrasonic probe. Means for calculating the reception time of the sound wave by adding the first propagation time and the second propagation time; and the reception time at the position of the element of the ultrasonic probe reflected at the upper lattice point; And a local sound speed determining means for determining the assumed sound speed that minimizes an error from the calculated reception time as a local sound speed in the region of interest.

  According to still another aspect of the present invention, an upper lattice point is set in a region of interest, and a lower lattice point is set between the upper lattice point and the ultrasonic probe, so that the sound speed (assumed sound velocity) of the region of interest is set. As a result, the first propagation time from the upper lattice point to the lower lattice point is calculated. On the other hand, from the assumed sound velocity and the environmental sound velocity that is the average sound velocity in the region from the lattice point to the ultrasonic probe, the emission angle (refracted) of the ultrasonic wave incident on the lower lattice point at a predetermined incident angle from the upper lattice point. Is calculated according to Snell's law. Snell's law is a law that expresses that there is a fixed relationship between the propagation velocity of each sound wave in two media and the incident and exit angles at the interface between the two media. It is also called. Since the refraction angle at the lower lattice point can be obtained in this way, the position of the element of the ultrasonic probe where the ultrasonic wave is incident from the lower lattice point and the second propagation time until it is incident on the element. And can be calculated. Then, the reception time at the element position of the ultrasonic probe obtained by adding the first propagation time and the second propagation time, and the ultrasonic probe of the reflection at the upper lattice point The assumed sound speed when the error from the actual reception time at the position of the child element is minimized is determined as the local sound speed in the region of interest. Since the position of the lattice point on the spatial coordinates is calculated with high accuracy, the local sound velocity obtained as described above is also highly accurate.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, an upper lattice point set in a region of interest among lattice points corresponding to three or more different depths on the first scanning line of interest; A lower lattice point set between the upper lattice point and the ultrasonic probe and a lower lattice point on a second scanning line different from the first scanning line are represented on the calculated spatial coordinates. An environment that is an average sound speed of a region from each lattice point to the ultrasonic probe based on a reception signal of reflection at the upper lattice point and the lower lattice point, and a lattice point setting unit that is set based on the position of the lattice point Environmental sound speed calculating means for calculating sound speed, and first calculation means for calculating a first received wave when the upper lattice point is a reflection point, based on the environmental sound speed calculated corresponding to the upper lattice point Assuming the assumed sound speed in the region of interest, from the upper lattice point to the lower lattice point Means for calculating a propagation time; and second calculation means for calculating a second received wave from the lower lattice point based on the ambient sound velocity calculated corresponding to the lower lattice point and the calculated propagation time; The assumed sound speed at which the error between the first received wave calculated by the first calculating means and the second received wave calculated by the second calculating means is minimized is the local sound speed in the region of interest. And a local sound speed determination means.

  According to still another aspect of the present invention, an upper lattice point is set in a region of interest, and a lower lattice point is set between the upper lattice point and the ultrasonic probe, so that the sound speed (assumed sound velocity) of the region of interest is set. And the ambient sound velocity, which is the average sound velocity in the region from each lattice point to the ultrasonic probe, is calculated based on the reception signals reflected at the upper lattice point and the lower lattice point. Then, the first received wave when the upper grid point is used as a reflection point is calculated based on the calculated environmental sound speed corresponding to the upper grid point. On the other hand, assuming the assumed sound velocity in the region of interest, the propagation time from the upper lattice point to each lower lattice point is calculated, and based on this propagation time and the ambient sound velocity calculated corresponding to the lower lattice point, A second received wave from the lattice point is calculated. Then, the assumed sound speed when the calculated error between the first received wave and the second received wave is minimized is determined as the local sound speed in the region of interest. This utilizes the fact that the received wave from the upper lattice point and the received wave from the lower lattice point coincide with each other by Huygens' principle.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the calculated predetermined sound speed is acquired as a local sound speed in a region of interest between the first lattice point and the second lattice point. It is a feature. That is, the sound speed used when calculating the position of the lattice point on the spatial coordinates is acquired as the local sound speed.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the first diagnostic signal is based on the reception signals of the reflections from the first and second grid points having different depths on the scanning line of the ultrasonic waves. Propagation time calculation means for calculating the propagation time of the ultrasonic wave between the lattice point and the second lattice point, and the first and second lattice points on the spatial coordinates converted by the conversion means And the first lattice point and the second lattice point based on the propagation time of the ultrasonic wave between the first lattice point and the second lattice point calculated by the propagation time calculating means. And a local sound speed calculating means for calculating the local sound speed in the region of interest between the two.

  According to still another aspect of the present invention, since the ultrasonic propagation distance can be obtained from the spatial coordinates of the first lattice point and the second lattice point, the propagation distance, the first lattice point, The local sound speed in the region of interest between the first lattice point and the second lattice point is calculated from the ultrasonic propagation time between the second lattice point and the second lattice point.

  The ultrasonic diagnostic apparatus according to yet another aspect of the present invention is characterized in that the local sound speed of the region of interest is calculated by averaging the local sound speeds obtained for each scanning line.

  The ultrasonic diagnostic apparatus according to still another aspect of the present invention includes an extraction unit that extracts a plurality of scanning lines without refraction based on the plurality of scanning line directions calculated by the scanning line direction calculation unit, and the extraction The local sound speed of the region of interest is calculated by averaging the local sound speeds obtained for the plurality of scanning lines without refraction. Note that the plurality of non-refractive scanning lines extracted by the extraction unit may include scanning lines whose change is small (for example, 1 degree or less) from the original scanning line direction of these scanning lines. Then, the local sound speed of the region of interest is calculated in the same manner as described above using only the information on the lattice points of the scanning line group without refraction.

  The ultrasonic diagnostic apparatus according to still another aspect of the present invention is characterized by further comprising amplitude image creating means for creating an amplitude image representing the amplitude of the ultrasonic detection signal by the luminance of a point.

  The ultrasonic diagnostic apparatus according to still another aspect of the present invention is characterized by further comprising display means for displaying the scanning line direction calculated by the scanning line direction calculation means.

  The ultrasonic diagnostic apparatus according to still another aspect of the present invention further includes display means for displaying the position of the grid point on the spatial coordinates converted by the conversion means or a line connecting the positions of the grid points. It is characterized by that.

  In the ultrasonic diagnostic apparatus according to still another aspect of the present invention, the ultrasonic diagnostic apparatus includes a steer angle adjustment unit that adjusts a steer angle of a scan line transmitted and received from the ultrasonic probe, and the scan line direction calculation unit includes: The scanning line direction is calculated based on the acquired received signal every time the steering angle is adjusted by the steering angle adjusting means. When the scanning line is incident so as to be substantially orthogonal to the boundary surface of different media, the refraction of the scanning line becomes small. Therefore, the local sound velocity in the region of interest can be obtained by adjusting the steer angle of the scan line and transmitting the scan line at a steer angle at which the refraction of the scan line is small.

  An ultrasonic diagnostic method according to another aspect of the present invention transmits ultrasonic waves from an ultrasonic probe including a plurality of elements to a subject, receives ultrasonic waves reflected by the subject, and receives ultrasonic waves. A step of acquiring a detection signal, a reception signal acquisition step of acquiring a reception signal of each reflection from three or more different depths on the scanning line of the ultrasonic wave based on the acquired ultrasonic detection signal, and the acquisition And a scanning line direction calculating step of calculating the scanning line direction based on the received signal.

  According to the present invention, the received signal of each element of the ultrasonic probe, and the received signal of each reflection from three or more different depths of the ultrasonic wave is used by a normal device configuration. The ultrasonic scanning line direction can be calculated with high accuracy, and can be calculated with a simple calculation process, whereby the sound speed (local sound speed) in the region of interest can be calculated with high accuracy, and There is an effect that the accuracy of displacement detection in the azimuth direction can be improved in functions such as transverse wave velocity measurement and lateral speckle tracking.

1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. The figure used to explain the steer angle of the ultrasonic beam emitted from the ultrasonic probe The flowchart which shows 1st Embodiment of the process sequence which calculates the local sound speed in the attention area | region of a subject. The figure which shows an example of each lattice point set to the attention area of a subject Diagram used to explain how to calculate the propagation time from the upper grid point to the lower grid point The figure used to explain the calculation method of the position of the lower grid point and the scanning line direction Figure used to explain the conversion of the position of the lower grid point from time coordinates to space coordinates The figure which showed typically the method of calculating a local sound speed by the refraction model calculation disclosed by patent document 1 The figure which showed typically the method of calculating a local sound speed using the Huygens principle disclosed by patent document 1 The flowchart which shows 2nd Embodiment of the process sequence which calculates the local sound speed in the attention area | region of a subject. The flowchart which shows other embodiment of the calculation method of the position and scanning line direction of the lower lattice point of the scanning line i + 1 adjacent to a certain scanning line i The figure used in order to explain the calculation method of the position of the lower lattice point and the scanning line direction shown in FIG. The figure which shows the reception time in the ultrasonic probe in the case where the medium (sound velocity) of the subject is uniform and non-uniform

  Preferred embodiments of an ultrasonic diagnostic apparatus and method according to the present invention will be described below with reference to the accompanying drawings.

[Device configuration]
FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention.

  The ultrasonic diagnostic apparatus 10 shown in FIG. 1 transmits an ultrasonic beam from the ultrasonic probe 300 to the subject OBJ, receives an ultrasonic beam (ultrasonic echo) reflected by the subject OBJ, and This is an apparatus for creating and displaying an ultrasonic image from a detection signal of a sound echo.

  A CPU (Central Processing Unit) 100 controls each block of the ultrasound diagnostic apparatus 10 in accordance with an operation input from the operation input unit 200.

  The operation input unit 200 is an input device that receives an operation input from an operator, and includes an operation console 202 and a pointing device 204. The console 202 has a display mode between a keyboard that accepts input of character information (for example, patient information), a mode that displays an amplitude image (B-mode image) alone, and a mode that displays a determination result of local sound speed. Display mode switching button for switching, freeze button for instructing switching between live mode and freeze mode, cine memory playback button for instructing cine memory playback, analysis for instructing analysis / measurement of ultrasonic images Includes a measurement button. The pointing device 204 is a device that receives an input for designating an area on the screen of the display unit 104, and is, for example, a trackball or a mouse. Note that a touch panel can be used as the pointing device 204.

  The storage unit 102 is a storage device that stores a control program for controlling the control of each block of the ultrasonic diagnostic apparatus 10 by the CPU 100, a parameter, a program for calculating a scanning line direction and the like according to the present invention. A hard disk or a semiconductor memory.

  The display unit 104 is, for example, a CRT (Cathode Ray Tube) display or a liquid crystal display, and displays an ultrasonic image (moving image and still image), a scanning line direction according to the present invention, a local sound velocity map, and various setting screens. indicate.

  The ultrasonic probe 300 is a probe used in contact with the subject OBJ, and includes a plurality of elements 302 constituting a one-dimensional or two-dimensional ultrasonic transducer array. The plurality of elements 302 transmit an ultrasonic beam to the subject OBJ based on the drive signal applied from the transmission circuit 402, receive an ultrasonic echo reflected from the subject OBJ, and output a detection signal.

  Each element 302 of the ultrasonic probe 300 includes a vibrator configured by forming electrodes on both ends of a piezoelectric material (piezoelectric body). Examples of the piezoelectric body constituting the vibrator include a piezoelectric ceramic such as PZT (lead zirconate titanate) and a polymer piezoelectric element such as PVDF (polyvinylidene difluoride). Can be used. When an electric signal is sent to the electrodes of the vibrator and a voltage is applied, the piezoelectric body expands and contracts, and ultrasonic waves are generated in each vibrator by the expansion and contraction of the piezoelectric body. For example, when a pulsed electric signal is sent to the electrode of the vibrator, a pulsed ultrasonic wave is generated, and when a continuous wave electric signal is sent to the electrode of the vibrator, a continuous wave ultrasonic wave is generated. Then, the ultrasonic waves generated in the respective vibrators are combined to form an ultrasonic beam. Further, when an ultrasonic wave is received by each vibrator, the piezoelectric body of each vibrator expands and contracts to generate an electric signal. The electrical signal generated in each transducer is output to the receiving circuit 404 as an ultrasonic detection signal.

  As the element 302 of the ultrasonic probe 300, a plurality of types of elements having different ultrasonic conversion methods can be used. For example, a transducer constituted by the piezoelectric body may be used as an element that transmits ultrasonic waves, and an optical transducer of an optical detection type may be used as an element that receives ultrasonic waves. Here, the light detection type ultrasonic transducer converts an ultrasonic signal into an optical signal for detection, and is, for example, a Fabry-Perot resonator or a fiber Bragg grating.

  Next, ultrasonic diagnostic processing in the live mode will be described. The live mode is a mode for displaying, analyzing, and measuring an ultrasonic image (moving image) obtained by transmitting and receiving ultrasonic waves by bringing the ultrasonic probe 300 into contact with the subject OBJ.

  When the ultrasound probe 300 is brought into contact with the subject OBJ and ultrasound diagnosis is started by an instruction input from the operation input unit 200, the CPU 100 outputs a control signal to the transmission / reception unit 400, and the ultrasound Transmission of the beam to the subject OBJ and reception of ultrasonic echoes from the subject OBJ are started. The CPU 100 sets the transmission direction of the ultrasonic beam and the reception direction of the ultrasonic echo for each element 302.

  Further, the CPU 100 selects a transmission delay pattern according to the transmission direction of the ultrasonic beam, and selects a reception delay pattern according to the reception direction of the ultrasonic echo. Here, the transmission delay pattern is pattern data of a delay time given to the drive signal in order to form an ultrasonic beam in a desired direction by ultrasonic waves transmitted from the plurality of elements 302, and the reception delay pattern is The pattern data of the delay time given to the detection signal in order to extract the ultrasonic echo from the desired direction by the ultrasonic waves received by the plurality of elements 302. The transmission delay pattern and the reception delay pattern are stored in the storage unit 102 in advance. The CPU 100 selects a transmission delay pattern and a reception delay pattern from those stored in the storage unit 102, and outputs a control signal to the transmission / reception unit 400 according to the selected transmission delay pattern and reception delay pattern to transmit / receive ultrasonic waves. Take control.

The transmission circuit 402 generates a drive signal in accordance with a control signal from the CPU 100 and applies the drive signal to the element 302. The transmission circuit 402 has delay circuits τ _{1 to} τ _N for each element 302 as shown in FIG. 2, and delays the drive signal applied to each element 302 based on the transmission delay pattern selected by the CPU 100. Let Here, the transmission circuit 402 adjusts (delays) the timing at which the drive signal is applied to each element 302 so that the ultrasonic waves transmitted from the plurality of elements 302 form an ultrasonic beam, as shown in FIG. Thus, the timing for applying the drive signal to each element 302 is adjusted (delayed) so as to adjust the direction of the ultrasonic beam (steer angle α). Note that the timing of applying the drive signal may be adjusted so that the ultrasonic waves transmitted from the plurality of elements 302 at a time reach the entire imaging region of the subject OBJ.

  The receiving circuit 404 receives and amplifies an ultrasonic detection signal output from each element 302 of the ultrasonic probe 300. As described above, since the distance between each element 302 and the ultrasonic wave reflection source in the subject OBJ is different, the time for the reflected wave to reach each element 302 is different. The reception circuit 404 includes a delay circuit, and a difference (delay) in the arrival time of the reflected wave according to a reception delay pattern set based on a sound speed selected by the CPU 100 (hereinafter referred to as “assumed sound speed”) or a sound speed distribution. Each detection signal is delayed by an amount corresponding to (time).

Next, the reception circuit 404 performs reception focus processing by matching and adding detection signals given delay times. When there is another ultrasonic reflection source at a position different from the ultrasonic reflection source X _ROI , the arrival time of the ultrasonic detection signal from the other ultrasonic reflection source is different. The phases of the ultrasonic detection signals from other ultrasonic reflection sources cancel each other. As a result, the received signal from the ultrasonic wave reflection source X _ROI becomes the largest and is focused. By the reception focus process, a sound ray signal (hereinafter referred to as “RF signal”) in which the focus of the ultrasonic echo is narrowed is formed.

  The A / D converter 406 converts the analog RF signal output from the receiving circuit 404 into a digital RF signal (hereinafter referred to as “RF data”). Here, the RF data includes phase information of the received wave (carrier wave). The RF data output from the A / D converter 406 is input to the signal processing unit 502 and the cine memory 602, respectively.

  The cine memory 602 sequentially stores the RF data input from the A / D converter 406. The cine memory 602 stores information related to the frame rate input from the CPU 100 (for example, parameters indicating the depth of the reflection position of the ultrasonic wave, the density of the scanning line, and the visual field width) in association with the RF data.

  The signal processing unit 502 corrects the attenuation due to the distance according to the depth of the reflection position of the ultrasonic wave by STC (Sensitivity Time gain Control) with respect to the RF data, and then performs an envelope detection process to obtain the B mode. Image data (image data representing the amplitude of ultrasonic echoes by the brightness (luminance) of a point) is generated.

  The B-mode image data generated by the signal processing unit 502 is obtained by a scanning method different from a normal television signal scanning method. Therefore, the DSC (Digital Scan Converter) 504 converts (raster conversion) the B-mode image data into normal image data (for example, television signal scanning method (NTSC method image data)). The image processing unit 506 performs various necessary image processing (for example, gradation processing) on the image data input from the DSC 504.

  The image memory 508 stores image data input from the image processing unit 506. The D / A converter 510 converts the image data read from the image memory 508 into an analog image signal and outputs the analog image signal to the display unit 104. Thereby, an ultrasonic image (moving image) photographed by the ultrasonic probe 300 is displayed on the display unit 104.

  In the present embodiment, the detection signal subjected to the reception focus process in the reception circuit 404 is an RF signal, but the detection signal not subjected to the reception focus process may be an RF signal. In this case, a plurality of ultrasonic detection signals output from the plurality of elements 302 are amplified in the reception circuit 404, and the amplified detection signals, that is, RF signals are A / D converted in the A / D converter 406. As a result, RF data is generated. The RF data is supplied to the signal processing unit 502 and stored in the cine memory 602. The reception focus process is performed digitally in the signal processing unit 502.

  Next, the cine memory playback mode will be described. The cine memory playback mode is a mode for displaying, analyzing and measuring an ultrasonic diagnostic image based on RF data stored in the cine memory 602.

  When the cine memory playback button on the console 202 is pressed, the CPU 100 switches the operation mode of the ultrasonic diagnostic apparatus 10 to the cine memory playback mode. In the cine memory reproduction mode, the CPU 100 instructs the cine memory reproduction unit 604 to reproduce the RF data designated by the operation input from the operator. The cine memory reproduction unit 604 reads RF data from the cine memory 602 according to a command from the CPU 100 and transmits the RF data to the signal processing unit 502 of the image signal generation unit 500. The RF data transmitted from the cine memory 602 is subjected to predetermined processing (processing similar to that in the live mode) in the signal processing unit 502, DSC 504, and image processing unit 506, and converted into image data. The data is output to the display unit 104 via the D / A converter 510. Accordingly, an ultrasonic image (moving image or still image) based on the RF data stored in the cine memory 602 is displayed on the display unit 104.

  When the freeze button on the console 202 is pressed while an ultrasonic image (moving image) is displayed in the live mode or the cine memory playback mode, the ultrasonic image displayed when the freeze button is pressed is displayed on the display unit 104. A still image is displayed. Thereby, the operator can display and observe a still image of a region of interest (ROI).

  When the measurement button on the console 202 is pressed, analysis / measurement designated by an operation input from the operator is performed. When the measurement button is pressed in each operation mode, the data analysis measurement unit 106 acquires RF data before image processing is performed from the A / D converter 406 or the cine memory 602, and uses the RF data. Operator-specified analysis / measurement (for example, tissue strain analysis (hardness diagnosis), blood flow measurement, tissue motion measurement, or IMT (Intima-Media Thickness) measurement )I do. The analysis / measurement result by the data analysis measurement unit 106 is output to the DSC 504 of the image signal generation unit 500. The DSC 504 inserts the analysis / measurement result by the data analysis / measurement unit 106 into the image data of the ultrasonic image and outputs it to the display unit 104. Thereby, the ultrasonic image and the analysis / measurement result are displayed on the display unit 104.

  In addition, when the display mode switching button is pressed, a mode for displaying the B mode image alone, a mode for displaying the determination result of the local sound speed superimposed on the B mode image (for example, color coding or luminance according to the local sound speed). The display mode is switched between a mode in which a B-mode image and a local sound speed value determination result image are displayed side by side, or a display in which the local sound speed is equalized by a line. Thereby, the operator can find a lesion, for example, by observing the determination result of the local sound speed. Note that a B-mode image obtained by performing at least one of the transmission focus process and the reception focus process may be displayed on the display unit 104 based on the determination result of the local sound speed.

  In addition, as a premise for accurately calculating the local sound velocity, the ultrasonic diagnostic apparatus 10 uses a plurality of ultrasonic beams (hereinafter referred to as “scanning”) based on reception signals at each element 302 of the ultrasonic probe 300. The scanning line direction is calculated. A method for calculating the scanning line direction will be described later. The display unit 104 can display the calculated scanning line direction.

[First Embodiment of Local Sound Velocity Measurement]
FIG. 3 is a flowchart showing a first embodiment of a processing procedure for calculating the local sound velocity in the region of interest of the subject.

  As shown in FIG. 3, first, a region of interest of the subject is set (step S1). This region of interest may be set by an operator using a pointing device on a still image of an ultrasonic image displayed on the display unit 104, or may be automatically set at a predetermined position and a predetermined size by a control program. Alternatively, binarization processing may be performed on the ultrasonic image, labeling processing may be performed in which the same numbers are assigned to pixels in which white portions (or black portions) are continuous, and the settings may be automatically performed in the order of the labeled numbers.

Subsequently, an upper lattice point and a lower lattice point are set in the set region of interest, and the environmental sound speed at each lattice point is obtained (step S2). The position of each grid point is defined by the scanning line position and the reception time. That is, as shown in FIG. 4, reflection points with different depths on the scanning lines 1, 2,..., N, which are emitted from the ultrasound probe 300 to the region of interest of the subject OBJ, are latticed. Set as a point. Here, the lower lattice point _{A 1, A 2, A 3} , ..., A n , each scanning lines 1, ..., reception time on n are the same reflection point, likewise the upper grid point B1 _{1 ,} B1 _2, B1 _3, ..., B1 _n and upper grid points B2, _1, B2 _2, B2 _3, ..., B2 _n are reflection points having the same reception time on each scanning line 1, 2, ..., n. is there.

  In FIG. 4, the lower lattice point A and the upper lattice points B1 and B2 are illustrated as lattice points having the same depth, but in actuality, between each lattice point and the ultrasonic probe 300, Since the sound speed of the area is not uniform, it becomes a reflection point of different depth in the space, and each scanning line 1, 2, ..., n that is linearly scanned is also refracted due to the difference in the sound speed of the propagation area of the scanning line, All scan lines are not necessarily parallel.

  Further, the range and number of grid points are determined in advance. Here, if the range of the lattice point used for the local sound speed calculation is wide, the error of the local sound speed value becomes large, and if it is narrow, the error with the virtual received wave becomes large. Therefore, the range of the lattice point is determined based on these factors. The interval between the lattice points in the x direction is determined by the balance between the resolution and the processing time. The interval between the lattice points in the x direction is, for example, 1 mm to 1 cm. Also, if the distance between the lower lattice point and the upper lattice point in the y direction is narrow, the error in error calculation becomes large, and if it is wide, the error in local sound speed becomes large. The interval between the lattice points in the y direction is determined based on the setting of the image resolution of the ultrasonic image, and is 1 cm as an example.

  Next, the environmental sound speed at each lattice point set as described above is calculated as follows.

<Calculation of environmental sound speed>
As shown in FIG. 13A, if the distance from a certain reflection point (grid point) X1 _ROI to the ultrasonic probe 300A is L, the lattice point X1 after the ultrasonic wave is reflected at the lattice point x1 _ROI. The elapsed time T until reception by the element 302A ₀ immediately below _ROI is T = L / V. When the elapsed time from the element 302A ₀ until received by the element 302A _i in the distance X away (array direction of elements 302A) X direction is T + [Delta] T, the delay time [Delta] T between the elements 302A ₀ and 302A _i Is represented by the following formula (1).

Accordingly, by measuring the elapsed time [2T, 2T + ΔT] from when the ultrasonic wave is transmitted and reflected after the time T at the lattice point x1 _ROI until it is received by each element, it reaches the lattice point x1 _ROI. The distance L and the speed V can be obtained uniquely.

  Here, the environmental sound speed at a certain grid point is the average sound speed in the region from the grid point to the ultrasonic probe, and is the sound speed at which the contrast and sharpness of the image are the highest. Therefore, as a method for determining the environmental sound speed, for example, a method (for example, Japanese Patent Laid-Open No. 8-317926) for determining from the contrast of the image, the spatial frequency in the scanning direction, dispersion, and the like can be applied. Further, it is preferable to focus so as to form transmission focal points at fine depth intervals in the region of interest so that the environmental sound speed can be obtained with sufficient accuracy.

  The reception time of each element reflected from the lattice point can be obtained from the environmental sound velocity thus obtained. That is, for each element reception signal reflected from the lattice point, a delay is determined assuming a certain sound speed, and when the contrast and sharpness of an image generated using the delay are the highest, the delay is This means that the reception time of each element is closest, so that it can be regarded as the reception time of each element with its sound speed (environmental sound speed), that is, with a delay. Instead of the environmental sound speed, the reception time of each element may be obtained by a method such as phase aberration analysis and used thereafter.

<Calculation of lower lattice position and scanning line direction and calculation of local sound velocity>
Next, each lower lattice point A _1, A _2, A _3, ..., _An (and upper lattice points B1 ₁ , B1 ₂ , B1 ₃ ,…, B1n, B2 ₁ , B2 ₂ , B2 ₃ ,…, B2n ,) For each scanning line 1, 2,..., N, the position of the lower grid point of the surrounding scanning line and the scanning line direction are obtained, and the local sound speed is obtained based on the position (step S3).

(i) Calculation of propagation time from upper lattice point to lower lattice point First, the propagation time from the upper lattice point to the lower lattice point is obtained for the scanning line of interest and its surrounding scanning lines.

  As shown in FIG. 5, the propagation times ΔT1, ΔT2, and ΔT3 from the lattice point (upper lattice point) B on the scanning line of interest to the lattice points (lower lattice points) A1, A2, and A3 on the peripheral scanning line are Can be calculated.

[Equation 2]
ΔTn = max (TBi-TAni)
In the above [Equation 2],
ΔTn: Propagation time from lattice point B to lattice An TBi: Propagation time from lattice point B to element i of the ultrasonic probe (reception time of lattice point B reflection at element i)
TAni: propagation time from the lattice point An to the element i of the ultrasonic probe (reception time of the lattice point An reflection at the element i)
It is.

  However, TBi and TAni indicate the propagation time of one way of the propagation path. The propagation time of each element of the ultrasonic probe or the propagation time from the environmental sound speed (the reception time or the shortest time at the element on the target scanning line). It is obtained by subtracting half of the reception time.

  FIG. 5 shows a curve indicating the reception time at each element i of the reflection ultrasonic probe at the lattice point B, and each element i of the reflection ultrasonic probe at the reflection of the lattice points A1, A2, and A3. A curve indicating the reception time is shown. According to Huygens' principle, the reception wave from the lattice point B (curve indicating the reception time) and the reception wave from the lattice points A1, A2, A3,... Are transmitted only for the propagation time from the lattice point B to each lattice point. This coincides with a virtual composite received wave (curve envelope indicating each reception time) that is virtually combined with delay. ΔTn calculated by the above [Expression 2] is a grid point from the grid point B necessary for the received wave from the grid point B and the virtual synthesized received wave from the grid points A1, A2, A3. The propagation time to An is shown. Or, instead of obtaining each propagation time ΔTn independently as in the formula [2], the position of the lower lattice points A1, A2, A3. Thus, the local sound speed between the upper lattice point B and the lower lattice points A1, A2, A3,. Each propagation time ΔTn can be obtained based on the positions of the lower lattice points A1, A2, A3.

(ii) Calculation of the position of the lower grid point and the scanning line direction Next, the angle formed by the surrounding scanning lines with respect to the scanning line of interest is obtained.

As shown in FIG. 6, to the lower lattice point A _n on one scanning line n, the position of the lower lattice point A _m on another scanning line m (Δx, Δy) is different depths on the scanning line n are the two upper lattice points B1 _n, B2 _n and a lower lattice point a _n, the propagation time between _{a m (Δt1, Δt1b, Δt2} , Δt2b) can be obtained from the following equation.

However, the position of the lower lattice point A _m (Δx, Δy) is, y-axis scanning line n, is the position on the coordinates of the origin of the lower lattice point A _n. Further, [Delta] y 'denotes the distance in the y direction of the upper lattice points B1 _n and the lower grid points A _m, V denotes the local sound velocity between the bottom grid points A _n, A _m and the upper lattice points B1 _n, B2 _n . Here, the sign of Δx is negative when it is opposite to the x-axis direction.

In the example above, relative to the lower grid point A _n, on the lattice points of the two different depths B1 _n, B2 _n (total, grid points of three different depths) but using the propagation time, it is possible to improve the accuracy of the position of the lower lattice point a _m (Δx, Δy) by using further different on grid points of depth B3 _n, B4 _n, a ....

For example, the upper lattice points B1 _n and B2 _n, B3 _n, ... position below the grid points A _m from each propagation time _{(Δx 12, Δy 12),} (Δx 13, Δy 13), ... look, on the grid point B2 _n and B3 _n, B4 _n, ... position below the grid points a _m from each propagation time _{(Δx 23, Δy 23),} (Δx 24, Δy 24), seeking ... upper grid point B3 _n and B4 _n , B5 _n, ... position below the grid points a _m from each propagation time _{(Δx 34, Δy 34),} (Δx 35, Δy 35), seeking ..., repeating this, the position of the lower lattice point a _m ([Delta] x _{ij, Δy ij) (i =} 1~N, j = 2~N + 1, where, i <after obtaining the j), the mean value position beneath the grid points _{a m (Δx, Δy)} may be.

By the above method, the scanning line n y axis, it is possible to determine the position of the lower lattice point A _m on the scanning line m on the coordinate having the origin under the grid point A _n (Δx, Δy). However, at this stage, since the local sound speed V is an unknown number, it is a position in the time coordinate system.

Next, in the same manner as above, y-axis scanning line m, the position of the lower lattice point A _n of the scan line n on the coordinate having the origin under grid point _{A m (Δx ', Δy'} ) obtained.

On the other hand, y-axis scanning line m, the position of the lower lattice point A _n of the scan line n when the coordinates of the origin the lower grid points A _m, is rotated by an angle θ about its origin ([Delta] x ", Δy ″) can be expressed by the following equation.

[Equation 4]
Δx ”= − Δx · cosθ + Δy · sinθ
Δy ”= − Δx · sinθ−Δy · cosθ
However, here, the positive direction of the angle θ is clockwise.

Note that the above [Expression 4] is different in sign from a known coordinate conversion formula when coordinates are rotated. Coordinates which, y-axis scanning line n, with respect to the position of the lower lattice point A _m calculated on the coordinate having the origin under the grid point A _n (Δx, Δy), that the origin of this position (Δx, Δy) position of the lower lattice point a _n on is because become what the sign of the position ([Delta] x, [Delta] y) was reversed.

The position of the lower lattice point A _n obtained as described above (Δx ', Δy') and the position (Δx ", Δy") and match, or the angle θ at which the error is minimum, scanning What is necessary is just to employ | adopt as an angle which the line n and the scanning line m make.

Further, as a method for determining the angle between the scan line n and scan line m in a simplified manner, at the time of obtaining the position of the lower lattice point A _m ([Delta] x, [Delta] y), determine the arctan (Δy / Δx), Part 2 Double may be viewed as θ.

  On the other hand, the direction of a straight line orthogonal to a curve (including an approximate curve by a spline interpolation method or the like) that smoothly connects the positions of the lower grid points A1, A2, A3,.

(Iii) Conversion of the position of the lower grid point from the time coordinate to the spatial coordinate Next, the position of the lower grid point on the time coordinate is calculated based on the angle formed by the surrounding scanning line with respect to the scanning line of interest. Convert to the upper position.

  The angle formed by each scanning line is 0 ° when each scanning line is not refracted when each scanning line is emitted in parallel as in the case where the ultrasonic probe 300 is a linear probe. When each scanning line is emitted so as to spread, the original spreading angle is obtained unless each scanning line is refracted.

  Based on this, among the angles formed by the surrounding scanning lines, the scanning line group close to the original angle (the angle when it is not refracted) is determined as a scanning line group having a small refraction, and extracted. It is assumed that the average value of the scanning line interval is equal to the original scanning line interval (interval when not refracted).

  For example, the interval between the original scanning lines emitted from the ultrasound probe 300 is determined from the pitch p of the elements 302 as shown in FIG. 2 when linear scanning is performed with a steer angle of 0 °.

When the average value of the scanning line interval of the scanning line group having a small refraction is Δx _ave and the original scanning line interval is W _ref , the following equation is established.

[Equation 5]
Δx _ave ≒ W _ref
Here, the scan line group with small refraction is extracted based on the angle θ formed by the surrounding scan lines obtained in (ii) for each scan line of interest. For example, after taking the difference in angle with respect to the scanning line of interest and converting it to an angle between adjacent scanning lines, the angle between each adjacent scanning line and the angle when it is not refracted (in the case of linear scanning, 0 °) Find the absolute value of the difference. Then, a scanning line group having a sum of absolute values of differences for a predetermined number of adjacent scanning lines and having a threshold value or less is determined as a scanning line group having a small refraction and extracted. Δx _ave is obtained based on the position of the lower grid point of each scanning line when the lower grid point of the target scanning line obtained in (ii) is used as the origin for the extracted scanning line group. For example, it is extracted after converting the coordinates (Δx _i , Δy _i ) with the lower grid point of the scanning line of interest as the origin to the coordinates (Δxr _i , Δyr _i ) with the lower grid point of the adjacent scanning line as the origin determined by taking the average of each? XR _i in the scan line group. Here, the subscript i represents the i-th scanning line.

Δx _ave is a variable obtained on the basis of the lower grid point position (Δx _i , Δy _i ) of each scanning line given by [Equation 3], and includes the local sound velocity V as an unknown number. Thus, the local sound speed can be obtained. As a result, the position of each lower lattice point (Δx _i , Δy _i ) given as a time coordinate according to the equation (3) with the local sound velocity V as a common unknown is calculated from the time coordinate including the scan line with large refraction. Can be converted to coordinates.

  As described above, in the case of a linear probe, scanning lines that are not refracted are parallel and have a known interval, so that Δx of the corresponding lower lattice point can be obtained spatially. On the other hand, in the case of a convex probe, the scanning line interval increases depending on the depth of the lower lattice point (distance in the scanning line direction from the probe surface), but the standard sound velocity is determined from the time depth of the corresponding lower lattice point. Thus, Δx can be obtained spatially with reference to the scanning line interval corresponding to the depth.

  Further, as another condition that enables conversion from time coordinates to space coordinates, a condition that minimizes the change in the scanning line direction due to refraction of the scanning line, or a condition that minimizes the difference between adjacent scanning line directions (adjacent Only if the matching scan lines are originally parallel).

  For this purpose, first, as shown in FIG. 7, the scanning line before refraction and the scanning line after refraction are arranged at an appropriate distance with the central axis aligned, and the end points of each scanning line are connected. Since the interval between the scanning lines before refraction is known, the position of the end point is also known. On the other hand, the lower lattice point is used as the end point of the scanning line after refraction. Here, in [Equation 3], by assuming the local sound velocity V, the position of the lower lattice point is given by spatial coordinates.

  Next, the magnitude of the direction change at each end point or the magnitude of the direction change difference at the end points of the adjacent scan lines is integrated for all the scan lines.

The direction change at the end points, as shown in FIG. _{7, θ 11, θ 12,} ..., θ 1n, θ 21, θ 22, ..., when the theta _2n, performs integration shown in the following equation.

[Equation 6]
Σ | θ _ij |
Or Σ | θ _ij −θ _ij-1 |
However, i = 1, 2, j = 1 to n
The integral value according to the above [Equation 6] varies depending on the assumed local sound speed, but the assumed local sound speed when the integral value is minimized is determined to be a true value, and the position of the lower lattice point at that time is determined. Judged as true value.

(Iv) Calculation of local sound speed Finally, the local sound speed is obtained based on the spatial coordinates of the lower lattice points of the surrounding scanning lines with respect to the scanning line of interest. Specifically, in the method disclosed in Patent Document 1, after giving the relative spatial coordinates of each lower grid point calculated in (iii), the calculation is repeated for each upper grid point on the scanning line of interest. Local sound speed can be obtained.

<First calculation method of local sound speed>
FIG. 8 is a diagram schematically showing a method of calculating the local sound speed by the refraction model calculation disclosed in Patent Document 1.

  In the following description, the direction parallel to the element surface S2 on which each element 302 of the ultrasonic probe 300 is arranged is defined as the X direction, and the direction perpendicular to the X direction (depth direction of the subject OBJ) is defined as the Y direction. To do.

As shown in FIG. 8, the upper grid point representing the region of interest ROI in the region A in the subject OBJJ is B _ROI , and the lower grid points are A1, A2,..., An,. The spatial coordinates of these lattice points are given by the method described above. That is, in FIG. 8, the y-coordinates of the respective lower lattice points are schematically matched and set at equal intervals in the x direction, but are shifted in the x and y directions according to the given spatial coordinates. .

A region between the boundary surface S1 connecting the lower lattice points A1, A2,..., An,... And the upper lattice point B _ROI in the subject OBJ is defined as a region A, and the boundary surface S1 and the ultrasonic probe 300 are A region between the element surface S2 is a region B. It is assumed that the sound speeds in the regions A and B are constant. The boundary surface S1 is not necessarily a straight line due to the refraction of the scanning line.

When the sound velocity (environmental sound velocity) in the region from the lower lattice points A1, A2,... To the element surface S2 of the ultrasonic probe 300 is substantially the same, or when the received waves from the lattice points A1, A2,. Alternatively, when the received waves can be considered to be approximately the same, or when the received waves change slowly, as shown in FIG. 8, between the upper grid point B _ROI and the lower grid points A1, A2,. Based on the sound velocity (local sound velocity) in the region A and the environmental sound velocity in the region B, the reception time at each element 302 is obtained by tracing the sound ray refracted at the boundary surface between the regions A and B according to Snell's law.

Specifically, if the assumed sound speed of the region of interest is _VA, and the incident angle of the sound ray incident on a certain lower lattice point X ′ from the upper lattice point B _ROI is Θ, the sound ray passing through the lower lattice point X ′ Can be expressed by the following equation according to Snell's law.

[Equation 7]
sinΘ / sinΘ '= V _A / V _B
Since the spatial coordinates of each lattice point are known, the incident angle Θ is also known, and by assuming the assumed sound velocity _VA , the refraction angle Θ ′ of the sound ray passing through the lower lattice point X ′ is expressed by the above [Expression 7]. ] Equation.

  As a result, the sound ray passing through the lower lattice point X ′ is incident, and the position X ″ of the element 302 on the ultrasonic probe 300 and the propagation of the sound ray from the lower lattice point X ′ to the position X ″ of the element 302 are transmitted. Time can be calculated.

Further, the propagation time from the upper lattice point B _ROI to the lower lattice points A1, A2,. This propagation time can be calculated by assuming the assumed sound velocity V _A because the distance between the respective lattice points can be obtained. Further, the value calculated in (i) may be adopted.

By tracing the sound ray as described above, it passes from the upper lattice point B _ROI to the lower lattice points A1, A2,..., And to which element position of the ultrasonic probe 300, which propagation time (reception time). ) Can be calculated respectively.

On the other hand, since the actual reception time at the position of each element 302 of the reflected ultrasound probe 300 at the lattice point B _ROI is measured in step S2, the calculated reception time and the measured reception time are calculated. The assumed sound speed when the error is minimized is determined as the true sound speed (local sound speed) in the region of interest.

<Second calculation method of local sound speed>
FIG. 9 is a diagram schematically illustrating a method of calculating the local sound speed using the Huygens principle disclosed in Patent Document 1. In FIG.

As shown in FIG. 9B, the propagation point T and the delay time ΔT of the received waves (W _A1 , W _A2 ,...) From the lower lattice points A1, A2 _,. The local sound speed at the lattice point B _ROI is obtained from the positional relationship between the lattice points A1, A2 _,. Specifically, the Huygens principle indicates that the received wave W _X from the upper grid point B _ROI matches the received wave W _SUM virtually combined with the received waves from the lower grid points A1, A2 _,. Use.

Here, the spatial coordinates of the upper lattice point B _{ROI and the} lower lattice points A1, A2,... Are given by the method described above.

As shown in FIG. 9, to calculate the waveform of the received wave W _X when the upper lattice point B _ROI and the reflection point based on the environmental sound speed V in the upper lattice point B _ROI. Further, propagation times from the upper lattice point B _ROI to the lower lattice points A1, A2,. These propagation times can be calculated by assuming the assumed sound velocity V _A because the distance between the lattice points can be obtained.

Based on the ambient sound velocity at each of the lattice points A1, A2,..., Received waves W _A1 , W _A2,. Then, these received waves W _A1 , W _A2 ,... _Are combined after being delayed by the propagation time calculated for each lattice point A1, A2,... To calculate a virtual combined received wave _WSUM .

Next, an error between the received wave W _X and the combined received wave W _SUM is calculated. Error between the received wave W _X resultant received wave W _SUM, a method, a method of phase matching addition is multiplied by the delay obtained from the resultant received wave W _SUM to the receiving wave W _X, or synthetic reception reversed cross-correlating with each other It is calculated by a method of multiplying the wave W _SUM by the delay obtained from the received wave W _X and adding the phase matching. Here, in order to obtain a delay from the received wave W _X , the lattice point B _ROI is used as a reflection point, and the time at which the ultrasonic wave propagated at the sound velocity V arrives at each element may be set as the delay. In addition, in order to obtain a delay from the combined reception wave _WSUM , an equiphase line is extracted from the phase difference of the combined reception wave between adjacent elements, and the equal phase line is used as a delay, or simply a combination of each element. The phase difference at the maximum (peak) position of the received wave may be used as the delay. Further, the cross-correlation peak position of the combined received wave from each element may be set as a delay. The error at the time of phase matching addition is obtained by a method of setting the peak to peak of the waveform after the matching addition or a method of setting the maximum value of the amplitude after the envelope detection.

The error between the received wave W _X and the synthesized received wave W _SUM varies depending on the assumed sound speed V _A. Then, the assumed sound speed when the error is minimized is determined as the true sound speed (local sound speed) in the region of interest.

<Other methods for calculating local sound speed>
In (iii), since the local sound velocity V is obtained when calculating the spatial coordinates of the lower lattice point, this local sound velocity V may be adopted.

  In (i), the propagation time from each upper lattice point on the target scanning line to each lower lattice point on the surrounding scanning line is obtained. The local sound velocity V may be obtained based on the above.

  In addition, among the surrounding scanning lines, as a scanning line group in which the scanning line direction has a small change (small refraction) from the original scanning line direction, for example, the scanning line angle θ obtained in (ii) and the original scanning line angle (For example, 0 ° for linear scanning) A scan line group having a small difference from an angle between adjacent scanning lines or an angle between original adjacent scanning lines (for example, 0 ° for linear scanning) A scanning line group with a small difference is extracted, and only the lower grid point of the scanning line group is used, and the calculation disclosed in Patent Document 1 is repeated or obtained from the propagation time for each upper grid point on the target scanning line. Also good. As the position of the lower lattice point at this time, the spatial coordinates that have already been obtained may be used, or the spatial coordinates on the premise that no refraction is performed may be used.

<Calculation of local sound velocity in the region of interest>
The local sound speed obtained for each scanning line of the region of interest as described above is averaged to obtain the local sound speed of the region of interest (step S4 in FIG. 3). Here, among each scanning line, a scanning line group in which the refraction of the surrounding scanning lines is small may be extracted, and only the local sound speed obtained for the scanning line group may be averaged. Further, the local sound speed may be obtained again based on the reception time from the upper lattice point and the lower lattice point of the scanning line group where the refraction is small and the environmental sound speed.

  At this time, for the scanning line group having a small refraction, the coordinates of the ideal condition (premise that no refraction is performed) are used as the position of the lower lattice point, and the local sound speed is calculated from the propagation time according to the method disclosed in Patent Document 1. You may ask for it. Alternatively, the environmental sound speed of each scanning line having a low refraction may be averaged, and the local sound speed may be obtained according to the method disclosed in Patent Document 1 based on the averaged environmental sound speed and each upper and lower lattice positions. Alternatively, the received signal or the focus index of each scanning line having a small refraction is averaged, and the environmental sound speed is obtained based on the average, and disclosed in Patent Document 1 based on the obtained environmental sound speed, each upper lattice position, and each lower lattice position. The local sound speed may be obtained according to a technique.

  As a method for determining a scanning line with small refraction, an absolute value or a square value of a difference with respect to a scanning line direction without refraction with respect to the surrounding scanning line is obtained, and an integrated value for each surrounding scanning line or a surrounding that is below a threshold The number of scanning lines may be used as an index.

[Second Embodiment of Local Sound Velocity Measurement]
FIG. 10 is a flowchart showing a second embodiment of the processing procedure for calculating the local sound velocity in the region of interest of the subject. In addition, the same step number is attached | subjected to the part which is common in 1st Embodiment shown in FIG. 3, The detailed description is abbreviate | omitted.

  As shown in FIG. 10, in the second embodiment, the processes in steps S3 'and S4' are different from the processes in steps S3 and S4 in the first embodiment.

  In step S3 ′, the position on the spatial coordinates of each lower grid point set in the region of interest and the scanning line direction of the scanning line passing through each lower grid point are obtained. In step S4 ′, the position is disclosed in Patent Document 1. In the method for obtaining the local sound velocity, the position on the spatial coordinates obtained in step S3 ′ is given to each lattice point, and the calculation is repeated for each upper lattice point to obtain the local sound velocity of the region of interest. Further, since the local sound speed is also obtained in the process of calculating the position of each lower lattice point on the spatial coordinates, this value may be adopted as the local sound speed. Alternatively, the local sound speed may be obtained based on the propagation time from each upper lattice point to the lower lattice point and the distance between each lattice point on the spatial coordinates.

  Further, out of the scanning line directions obtained in step S3 ′, only the scanning line group having a small refraction is extracted, and the calculation disclosed in Patent Document 1 is repeatedly focused on each lattice point of the scanning line group having a small refraction. The local sound speed of the region may be obtained, or the local sound speed may be obtained based on the propagation time from each upper lattice point to each lower lattice point and the distance between the lattice points on the spatial coordinates. At this time, as the position of the lower lattice point on the spatial coordinates, the spatial coordinates already obtained may be used, or the spatial coordinates on the assumption that the scanning line is not refracted may be used.

  FIG. 11 is a flowchart showing another embodiment of a method of calculating the position of the lower lattice point and the scanning line direction of the scanning line i + 1 adjacent to a certain scanning line i in the process of step S3 '.

This embodiment, the angle of the lower lattice point A _{i + 1} of the coordinates of the scanning line i + 1 relative to the bottom grid points A _i, and a scanning line i and the scanning line i + 1 of the scanning line i, The propagation time from the upper grid point on another scanning line is also used to calculate with high accuracy.

  In FIG. 11, first, the propagation time from each upper lattice point to the lower lattice point in the region of interest is obtained (step S10). This propagation time can be calculated by the method shown in FIG.

  Next, as shown in FIG. 12, a variable indicating a scanning line set in the region of interest is i (i = 0 to N), and a variable indicating a scanning line within a predetermined range including the scanning line i is j (j = −n to + n) (steps S12 and S14).

Subsequently, the propagation time from the upper lattice point B1 _i , B2 _i on the scanning line i to the lower lattice point A _{i + j} of the scanning line i + j, and the upper lattice point B1 _{i + j} , of the scanning line _{i + j} , Based on the propagation time from B2 _{i + j} to the lower lattice point A _i on the scanning line i, the coordinates of the lower lattice point A _{i + j} when the scanning line i is the y axis and the lower lattice point A _i is the origin, and The angles formed by the scanning line i and the scanning line i + j are obtained and stored in the lower grid point [i] [j] and the angle [i] [j], respectively (step S16). Note that the calculation method of the coordinates of the lower grid point A _{i + j} and the angle formed between the scanning line i and the scanning line i + j can be performed by the method described with reference to FIG.

  In step S18, the variable j is incremented by 1, and the processing from step S14 to step S18 is repeated until the variable j changes from -n to + n.

  When the variable j changes from -n to + n, the variable i is incremented by 1 in step S20, and the processing from step S12 to step S20 is repeated until the variable i changes from 0 to N.

  When the processing from step S12 to step S20 is completed, all lower lattice points [i] [j] and angles [i] [j] can be acquired.

  Next, the variable indicating the scanning line is again i (i = 0 to N), and the variable indicating the scanning line within the predetermined range including the scanning line i is j (j = −n + 1 to + n) (step) S22, S24).

Subsequently, from the obtained lower lattice point [i] [j], the lower lattice point [i + j] [-j + 1] corresponding to the variables i and j set in steps S22 and S24 and the lower lattice point The point [i + j] [-j] is extracted, and these differences are converted into a coordinate system with the scanning line i as the y-axis and the lower grid point A _i as the origin, and viewed from the lower grid point A _i The coordinates of the grid point A _{i + 1} are stored in the lower grid point 2 [i], which is an array indicating the coordinates of the lower grid point, and the stored number is counted. Similarly, from the obtained angle [i] [j], an angle [i + j] [-j + 1] and an angle [i + j] corresponding to the variables i and j set in steps S22 and S24. [-j] is extracted, and these differences are stored in an angle 2 [i] which is an array indicating the angle as an angle formed between the scanning line i and the scanning line i + 1, and the stored number is counted (step S26).

  In step S28, the variable j is incremented by 1, and the processing from step S24 to step S28 is repeated until the variable j changes from -n + 1 to + n.

  When the variable j changes from −n + 1 to + n, the variable i is incremented by 1 in step S30, and the processing from step S22 to step S30 is repeated until the variable i changes from 0 to N.

When the processing from step S22 to step S30 is completed, the lower lattice point 2 [i] has a lattice point A _{i +} calculated by a combination of the scanning line i, i + 1 and a scanning line other than these scanning lines. The coordinates of ₁ are accumulated and stored. Similarly, at the angle 2 [i], the scanning line i, i + calculated by the combination of the scanning line i, i + 1 and the scanning line other than these scanning lines is used. The angle formed by 1 is accumulated and stored.

  Next, the coordinates of the average lower grid point 2 are obtained by dividing the accumulated value stored in the lower grid point 2 [i] by the counted value, and stored in the angle 2 [i]. The average angle 2 is obtained by dividing the accumulated value by the counted value. Further, the coordinates of the lower grid point 2 are converted from the time coordinates to the lower grid point 3 of the space coordinates (step S32). Note that the conversion from the time coordinate to the space coordinate can be performed by the method described in FIG.

  With the above method, the spatial coordinates of the lower grid point of each scan line and the scan line direction passing through the lower grid point can be calculated with high accuracy, and the local sound velocity in the region of interest can also be calculated with high accuracy.

<Other embodiments>
Depending on the positional relationship between the plurality of scanning lines sent from the ultrasound probe 300 and the region of interest, it is conceivable that there is no scanning line group without refraction. In this case, the steer angle α of the scanning line emitted from the ultrasonic probe 300 toward the region of interest is adjusted with the delay time to each element as shown in FIG. Change the incident angle.

The steering angle α can be adjusted by delaying the drive signal applied from the transmission circuit 402 to the element i of the ultrasonic probe 300 by the delay time Δτ _i shown in the following equation.

[Equation 8]
Δτ _i = (i−1) p · sin α / V
Where p: element pitch, V: sound velocity (eg, known sound velocity in subcutaneous fat, etc.)
At the time of reception, reception focus is performed so as to form a focus at each depth in the direction of the steer angle α, and the ambient sound speed at each lattice point is obtained. Here, in order to accurately determine the ambient sound velocity at each lattice point, it is preferable to focus so as to form a transmission focal point at each depth in the direction of the steer angle α during transmission.

  In this way, a scanning line group with no refraction or a scanning line group with small refraction can be obtained by calculating the scanning line direction or the like each time the incident angle of the scanning line to the region of interest is changed.

  In addition, the present invention can be applied to an object whose sound speed is not uniform by making the region of interest small. Although the local sound velocity may be obtained independently in each region, the result of the region close to the ultrasonic probe (shallow region) may be used. For example, a scan line group with small refraction may be determined including a determination result of small refraction of the scan line in the shallow region, or scanning in the shallow region in the conversion from the time coordinate to the spatial coordinate of the position of the lower lattice point. Spatial coordinates that minimize the change from the line direction to the scanning line direction of the region of interest may be taken, or spatial coordinates from the shallow region such that the scanning line interval coincides with the scanning line interval of the region of interest may be taken.

  Further, each scanning line indicating the calculated scanning line direction, the position of the lower grid point, or a line connecting the positions of the lower grid points may be displayed on the display unit 104.

  Further, as described in <Calculation of environmental sound speed>, since the reception signal from a certain reflection point (grid point) on the ultrasonic scanning line and the environmental sound speed at the lattice point are in a certain relationship, "Signal" is a concept that includes ambient sound speed. The scanning line without refraction is not limited to the case where the scanning line is not refracted at all, but includes a scanning line with low refraction. For example, the change in the scanning line direction is 1 depending on the accuracy of the required local sound velocity. A scanning line of about the same degree or less.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasound diagnostic apparatus, 100 ... Central processing unit (CPU), 102 ... Storage part, 104 ... Display part, 106 ... Data analysis measurement part, 200 ... Operation input part, 202 ... Console, 204 ... Pointing device, 300 DESCRIPTION OF SYMBOLS ... Ultrasonic probe, 302 ... Ultrasonic transducer (element), 400 ... Transmission / reception part, 402 ... Transmission circuit, 404 ... Reception circuit, 500 ... Image signal generation part, 502 ... Signal processing part, 506 ... Image processing part, 508: Image memory, 510: D / A converter, 600: Playback unit

Claims (20)

An ultrasonic probe including a plurality of elements that transmit ultrasonic waves to the subject, receive ultrasonic waves reflected by the subject, and output ultrasonic detection signals;
A reception signal acquisition means for acquiring a reception signal of each reflection from three or more different depths of the ultrasonic wave based on the ultrasonic detection signal;
Scanning line direction calculating means for calculating a scanning line direction based on the acquired received signal;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to claim 1, wherein the received signal is a signal received by a plurality of elements of the ultrasonic probe. The scanning line direction calculation means includes
Of the scanning lines transmitted and received from the ultrasonic probe, lattice points corresponding to three or more different depths on the first scanning line of interest, and on a second scanning line different from the first scanning line Propagation time calculation means for calculating the propagation time of ultrasonic waves between the lattice points corresponding to three or more different depths based on the reception signal acquired by the reception signal acquisition means;
The first grid point of the grid points corresponding to three or more different depths on the first scan line is the origin, and on the first time coordinate with the first scan line as a reference, the First position calculating means for calculating a second position of the second grid point on the second scanning line based on the propagation time calculated by the propagation time calculating means;
The second grid point of the grid points corresponding to three or more different depths on the second scan line is the origin, and the second time coordinate with the second scan line as a reference is Second position calculating means for calculating a first position of the first grid point on the first scanning line based on the propagation time calculated by the propagation time calculating means;
The second position calculated by the first position calculating means is the origin, and the third time coordinate on the first scanning line is rotated on the third time coordinate rotated by an arbitrary angle with respect to the first time coordinate. Third position calculating means for calculating a third position of one grid point by coordinate transformation;
An error between the first position of the first grid point calculated by the second position calculation unit and the third position of the first grid point calculated by the third position calculation unit is An angle calculating means for calculating a rotation angle of the third time coordinate at the minimum as an angle formed by the first scanning line and the second scanning line;
The ultrasonic diagnostic apparatus according to claim 1 or 2, characterized by comprising:   The scanning line direction calculating means calculates (n−1) angles formed by the first scanning line and the second scanning line from n (n: an integer of 3 or more) scanning lines, The ultrasonic diagnostic apparatus according to claim 3, wherein an average of the calculated angles is an angle formed by the first scanning line and the second scanning line.   The scanning line direction calculating means calculates (n−1) angles formed by the first scanning line and the second scanning line from n (n: an integer of 3 or more) scanning lines, Is the angle formed by the first scanning line and the second scanning line, the first lattice point on the first scanning line is the origin, and the first scanning line (N-1) second positions of the second grid points on the second scanning line are calculated on the first time coordinate with reference to the average of the calculated second positions. The ultrasonic diagnostic apparatus according to claim 3, wherein the position is a position of a second lattice point of the second scanning line. The scanning line direction calculation means includes
Among the scanning lines transmitted and received from the ultrasonic probe, lattice points corresponding to three or more different depths on the first scanning line of interest, and a plurality of second points different from the first scanning line. Propagation time calculation means for calculating the propagation time of the ultrasonic wave between each lattice point with the second lattice point on the scanning line based on the reception signal acquired by the reception signal acquisition means;
Of the lattice points corresponding to three or more different depths on the first scanning line, the first lattice point is the origin, and the second coordinate is on the time coordinate with respect to the first scanning line. Position calculating means for calculating the positions of a plurality of second grid points on the scanning line based on the propagation time calculated by the propagation time calculating means;
2. The direction of the second scanning line with respect to the first scanning line is a direction of a straight line that intersects at right angles to a curve connecting the positions of the plurality of second lattice points. Or the ultrasonic diagnostic apparatus of 2. The propagation time calculation means includes
First propagation time calculation means for calculating a first propagation time from an upper lattice point on the scanning line of interest to each element of the ultrasonic probe;
Second propagation time calculating means for calculating a second propagation time from a lower lattice point set in a region between the upper lattice point and the ultrasonic probe to each element of the ultrasonic probe When,
On each element of the ultrasonic probe, the time difference on the element at which the time difference between the calculated first propagation time and the second propagation time is maximized is calculated from the upper lattice point to the lower lattice point. Means for calculating the ultrasonic propagation time;
The ultrasonic diagnostic apparatus according to claim 3, comprising: Extraction means for extracting two or more scanning lines without refraction based on a plurality of scanning line directions calculated by the scanning line direction calculation means;
A distance calculating means for calculating a spatial distance between the two scanning lines by multiplying a time interval between lattice points of the same depth of the two or more extracted scanning lines and a predetermined sound speed;
The predetermined sound velocity is calculated so that a scanning line interval at the lattice point of a scanning line having no refraction among scanning lines transmitted from the ultrasonic probe coincides with a distance calculated by the distance calculation unit. Conversion means for converting from the position of each grid point on the time coordinate to the position on the spatial coordinate based on the calculated sound speed;
The ultrasonic diagnostic apparatus according to claim 1, further comprising: Among the scanning lines transmitted and received from the ultrasonic probe, lattice points corresponding to three or more different depths on the first scanning line of interest, and a plurality of second points different from the first scanning line. Propagation time calculation means for calculating the propagation time of the ultrasonic wave between each lattice point with the second lattice point on the scanning line based on the reception signal acquired by the reception signal acquisition means;
Of the lattice points corresponding to three or more different depths on the first scanning line, the first lattice point is the origin, and the second coordinate is on the time coordinate with respect to the first scanning line. Position calculating means for calculating the positions of a plurality of second grid points on the scanning line based on the propagation time calculated by the propagation time calculating means;
Coordinate conversion means for converting the position on the time coordinate of the first lattice point and the second lattice point into a position on a spatial coordinate based on a predetermined sound velocity;
A plurality of end points of the same depth on the scanning line corresponding to the first and second scanning lines transmitted from the ultrasonic probe before being refracted; and the first and second Integration means for connecting the positions of the grid points on the spatial coordinates and integrating the magnitude of the direction change at each end point or the difference in the direction change at each end point of the adjacent scan lines with respect to all the scan lines;
Conversion means for calculating the predetermined sound speed at which an integration value by the integration means is minimized, and converting the position of each lattice point on the time coordinate to a position on a spatial coordinate based on the calculated sound speed;
The ultrasonic diagnostic apparatus according to claim 1, further comprising: An upper lattice point set in a region of interest among lattice points corresponding to three or more different depths on the first scanning line of interest, and between the upper lattice point and the ultrasonic probe Grid point setting means for setting a lower grid point to be set and a lower grid point on a second scanning line different from the first scanning line based on the position on the calculated spatial coordinates;
Based on the reception signal of the reflection at the lower grid point, an environmental sound speed calculating means for calculating an environmental sound speed that is an average sound speed of a region from the lower grid point to the ultrasonic probe;
Means for assuming a hypothetical sound velocity in the region of interest and calculating a first propagation time from the upper lattice point to the lower lattice point;
According to Snell's law, the incident angle of the ultrasonic wave incident on the lower lattice point from the upper lattice point, the assumed sound velocity of the region of interest, and the environmental sound velocity of the region between the lower lattice point and the ultrasonic probe Means for calculating an emission angle of an ultrasonic wave emitted from the lower lattice point based on:
Means for calculating a position of an element of the ultrasonic probe on which an ultrasonic wave emitted from the lower lattice point at the calculated emission angle is incident and a second propagation time until the ultrasonic wave is incident on the element;
Means for calculating the reception time of the ultrasonic wave at the position of the element of the ultrasonic probe by adding the first propagation time and the second propagation time;
Local sound speed for determining the assumed sound speed at which the error between the reception time of the reflection at the upper lattice point at the position of the element of the ultrasonic probe and the calculated reception time is minimum as the local sound speed in the region of interest A determination means;
The ultrasonic diagnostic apparatus according to claim 8 or 9, further comprising: An upper lattice point set in a region of interest among lattice points corresponding to three or more different depths on the first scanning line of interest, and between the upper lattice point and the ultrasonic probe Grid point setting means for setting a lower grid point to be set and a lower grid point on a second scanning line different from the first scanning line based on the position on the calculated spatial coordinates;
An environmental sound speed calculating means for calculating an environmental sound speed that is an average sound speed of an area from each lattice point to the ultrasonic probe, based on reception signals of reflection at the upper lattice point and the lower lattice point;
First calculation means for calculating a first received wave when the upper lattice point is a reflection point, based on an environmental sound velocity calculated corresponding to the upper lattice point;
Assuming an assumed sound velocity in the region of interest, means for calculating a propagation time from the upper lattice point to the lower lattice point;
Second calculation means for calculating a second received wave from the lower grid point based on the environmental sound velocity calculated corresponding to the lower grid point and the calculated propagation time;
The assumed sound speed at which the error between the first received wave calculated by the first calculating means and the second received wave calculated by the second calculating means is minimized is the local sound speed in the region of interest. Local sound speed determination means for determining,
The ultrasonic diagnostic apparatus according to claim 8 or 9, further comprising:   10. The ultrasonic diagnostic apparatus according to claim 8, wherein the calculated predetermined sound speed is acquired as a local sound speed in a region of interest between the first lattice point and the second lattice point. Ultrasonic diagnostic equipment. The ultrasonic waves between the first and second grid points based on the reception signals of the reflections from the first and second grid points having different depths on the ultrasonic scanning line. Propagation time calculation means for calculating the propagation time of
The positions of the first and second grid points on the space coordinates transformed by the transform unit according to claim 8 or 9, and the first grid points calculated by the propagation time calculation unit Local sound speed calculating means for calculating a local sound speed in a region of interest between the first lattice point and the second lattice point based on the propagation time of the ultrasonic wave between the second lattice point;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to any one of claims 10 to 13, wherein the local sound speed obtained for each scanning line is averaged to calculate the local sound speed of the region of interest. Extracting means for extracting a plurality of scanning lines without refraction based on the plurality of scanning line directions calculated by the scanning line direction calculating means;
The supersonic wave according to any one of claims 10 to 13, wherein the local sound speed of the region of interest is calculated by averaging the local sound speeds obtained for the extracted plurality of scanning lines without refraction. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to any one of claims 1 to 15, further comprising amplitude image creating means for creating an amplitude image representing the amplitude of the ultrasonic detection signal by the luminance of a point.   The ultrasonic diagnostic apparatus according to claim 1, further comprising display means for displaying a scanning line direction calculated by the scanning line direction calculation means.   16. The display device according to claim 8, further comprising display means for displaying the positions of the grid points on the spatial coordinates converted by the conversion means, or lines connecting the positions of the grid points. An ultrasonic diagnostic apparatus according to 1. A steer angle adjusting means for adjusting a steer angle of a scanning line transmitted and received from the ultrasonic probe;
19. The scanning line direction calculating unit calculates the scanning line direction based on the acquired reception signal every time the steering angle is adjusted by the steering angle adjusting unit. The ultrasonic diagnostic apparatus according to item 1. A step of transmitting an ultrasonic wave from an ultrasonic probe including a plurality of elements to a subject, receiving an ultrasonic wave reflected by the subject, and acquiring an ultrasonic detection signal;
A reception signal acquisition step of acquiring a reception signal of each reflection from three or more different depths of the ultrasonic wave based on the acquired ultrasonic detection signal;
A scanning line direction calculating step of calculating a scanning line direction based on the acquired reception signal;
An ultrasonic diagnostic method comprising:

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