JP2012249925A - Ultrasonic image producing method and ultrasonic image diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic image producing method and an ultrasonic image diagnostic apparatus, capable of quickly deciding the presence or absence of influence of refraction, shortening the time taken for measurement or calculation, performing measurement or calculation with a small measurement error, and calculating accurate local sound velocity values.SOLUTION: In the ultrasonic image producing method, main sound measurement is performed in such a way that a B-mode image is captured, a region-of-interest is set, a lattice is set in the set region-of-interest, and local sound velocities are calculated at a plurality of lattice points. Prior to performing the main sound velocity measurement, environmental sound velocity values of two or more lattice points located at different positions in a scanning direction of ultrasonic waves are each measured in the lattice as preliminary sound velocity measurement, and the main sound velocity measurement is performed when the difference between a maximum value and a minimum value of the measured environmental sound velocity values is equal to or lower than a predetermined threshold. Thus, the problem is solved.

Description

  The present invention relates to an ultrasonic image generation method and an ultrasonic image diagnostic apparatus for imaging an internal organ or the like by transmitting / receiving ultrasonic waves to generate an ultrasonic diagnostic image used for diagnosis.

  Conventionally, in the medical field, an ultrasonic diagnostic apparatus using an ultrasonic image has been put into practical use. In general, this type of ultrasonic diagnostic apparatus has an ultrasonic probe (ultrasonic probe) having a built-in transducer array, and an apparatus main body connected to the ultrasonic probe. Ultrasound images are transmitted by transmitting ultrasonic waves from the probe to the subject, receiving ultrasonic echoes from the subject with the ultrasonic probe, and processing the received signals electrically with the device body Is generated.

By the way, in the ultrasonic diagnostic apparatus, when generating an ultrasonic image, the ultrasonic image is generated on the assumption that the sound speed in the living body of the subject is constant. However, since there is a variation in the actual sound speed value in the living body, this variation causes a spatial distortion in the ultrasonic image.
On the other hand, in recent years, in order to more accurately diagnose a diagnosis site in a subject, a sound speed value (local sound speed value) at an arbitrary diagnosis site is measured, and such image distortion is corrected. It has been broken.

For example, Patent Document 1 discloses an environmental sound speed value (optimal sound speed value) based on reception data obtained by setting a plurality of lattice points around a diagnostic region and transmitting / receiving an ultrasonic beam to / from each lattice point. ), And an ultrasonic diagnostic apparatus that calculates a local sound velocity value at each lattice point from environmental sound velocity values at a plurality of lattice points has been proposed.
Also, in Patent Document 2, the degree of beam convergence in focus processing is determined in a plurality of first regions, a sound speed value is obtained for each region, and a plurality of second regions subdivided from the first region. There has been proposed an ultrasonic diagnostic apparatus that obtains a sound velocity value for the above region.

JP 2010-99452 A JP 2009-279306 A

  By the way, when measuring the sound velocity value in the living body, the sound velocity value (environmental sound velocity value) obtained from transmission / reception of the ultrasonic beam may be disturbed in the azimuth direction (lateral direction). For example, when measuring the abdomen, the sound speed value is disturbed in the azimuth direction. This is presumed that sound waves are refracted in the fat layer and muscle layer of the abdominal wall before going to the liver. In this way, the sound speed value may be measured higher than the actual sound speed due to refraction or the like in a certain region.

When calculating the local sound speed value at each lattice point from the environmental sound speeds at a plurality of lattice points as in Patent Document 1, or at a plurality of subdivided second regions as in Patent Document 2, If the environmental sound speed (the sound speed value in the first area) is measured higher than the actual sound speed, the accurate local sound speed value (the sound speed value in the second area) cannot be determined. There is a fear.
In addition, when the local sound velocity value is obtained as in Patent Document 1 and Patent Document 2, it takes time to perform the calculation. Therefore, after performing all the measurements and calculations, the measurement error due to the influence of such refraction is found. As a result, computation time is wasted.

  The object of the present invention is to solve the above-mentioned problems of the prior art, to quickly grasp the influence of refraction, to shorten the time required for measurement and calculation, and to perform measurement and calculation with little measurement error. Another object of the present invention is to provide an ultrasonic image generation method and an ultrasonic diagnostic imaging apparatus that can obtain an accurate local sound velocity value.

  In order to achieve the above object, the present invention transmits an ultrasonic wave from a transducer array of an ultrasonic probe to a subject and outputs the ultrasonic echo from the subject. In an ultrasonic image generation method for generating an ultrasonic image based on a received signal, a B-mode image is captured, a region of interest is set, a lattice is set in the set region of interest, and locality at a plurality of lattice points is set. When performing the sonic velocity main measurement for calculating the sonic velocity value, prior to the sonic velocity main measurement, as the sonic velocity pre-measurement, the environmental sound velocity values of two or more lattice points different in the scanning direction of the ultrasonic wave of the lattice are respectively measured. There is provided an ultrasonic image generation method characterized in that the sound speed main measurement is performed when the difference between the measured maximum value and the minimum value of the environmental sound speed value is equal to or smaller than a predetermined threshold value.

Here, in the sound speed pre-measurement, the environmental sound speed values at two or more lattice points in the ultrasonic scanning direction are measured at different depths, and the maximum and minimum environmental sound speed values are measured at all depths. When the difference from the value is equal to or smaller than a predetermined threshold value, it is preferable to perform the sonic speed main measurement.
In addition, it is preferable to set a grid having a size exceeding the set target area.
Moreover, it is preferable that the number of lattice points at which the environmental sound speed value is measured in the sound speed pre-measurement is smaller than the number of lattice points at which the local sound speed value is calculated in the sound speed main measurement.

In addition, it is preferable that the environmental sound speed value measured in the sound speed pre-measurement is compared and a lattice point having the largest environmental sound speed value is displayed in a distinguishable manner.
Moreover, it is preferable to display a warning and a measurement result of the environmental sound speed value when the difference between the maximum value and the minimum value of the environmental sound speed value measured in the sound speed pre-measurement exceeds a predetermined threshold.
Moreover, it is preferable to display the measurement result of the local sound speed value in the sound speed main measurement superimposed on the ultrasonic image.

  In order to achieve the above object, the present invention provides an ultrasonic transducer that transmits ultrasonic waves from a transducer array of an ultrasonic probe to a subject and receives ultrasonic echoes from the subject. In an ultrasonic diagnostic imaging apparatus that generates an ultrasonic image based on a received signal to be output, a region of interest is set in an imaging region, a lattice is set in the set region of interest, and a plurality of lattice points are set A sound velocity pre-measurement that measures the environmental sound velocity values of two or more lattice points that are different from each other in the ultrasonic scanning direction, and calculates the difference between the maximum and minimum values of the measured environmental sound velocity values. And a sound speed book for calculating local sound speed values at a plurality of lattice points of the lattice when the difference between the maximum value and the minimum value of the environmental sound speed value calculated by the sound speed pre-measurement unit is equal to or less than a predetermined threshold value. Ultrasonic imaging characterized by having a measuring unit To provide a device.

  According to the ultrasonic image generation method and the ultrasonic diagnostic imaging apparatus of the present invention having the above-described configuration, two or more grids different in the scanning direction of the ultrasonic wave are used as the sound speed pre-measurement before the local sound speed value is calculated. Measure the ambient sound velocity value at each point, and if the difference between the maximum and minimum measured environmental sound velocity values is less than or equal to the specified threshold value, the sound velocity main measurement will be performed, so it is possible to quickly grasp the influence of refraction. In addition, the time required for measurement / calculation can be shortened, and measurement / calculation with a small measurement error can be performed, so that an accurate local sound velocity value can be obtained.

It is a block diagram which shows notionally the structure of the ultrasonic diagnosing device which implements the ultrasonic image generation method which concerns on this invention. It is a block diagram which shows notionally the structure of the sound speed calculating part of FIG. It is a figure which shows the set lattice point typically. (A) And (B) is a figure which shows typically the selected pre-measurement grid point. (A) And (B) is a figure which shows typically the measurement result of environmental sound speed value. It is a figure which shows a lattice point typically. (A) And (B) is a figure which shows the principle of a sound speed calculation typically. 3 is a flowchart for explaining the operation of the ultrasonic diagnostic apparatus in FIG. 1. It is a figure which shows typically the grid point for pre measurement.

  Hereinafter, an ultrasonic diagnostic apparatus for carrying out an ultrasonic image generation method of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a block diagram conceptually showing the structure of an example of an ultrasonic diagnostic apparatus that implements the ultrasonic image generation method of the present invention.
The ultrasonic diagnostic apparatus 10 includes an ultrasonic probe 12, a transmission circuit 14 and a reception circuit 16 connected to the ultrasonic probe 12, an image generation unit 18, a cine memory 22, a sound speed calculation unit 24, and a display control unit 32. A display unit 34, a control unit 36, an operation unit 38, and a storage unit 40.

The ultrasonic probe 12 has a transducer array 42 used in a normal ultrasonic diagnostic apparatus.
The transducer array 42 has a plurality of ultrasonic transducers arranged one-dimensionally or two-dimensionally. Each of these ultrasonic transducers transmits an ultrasonic beam according to a drive signal supplied from the transmission circuit 14 at the time of imaging an ultrasonic image, and receives an ultrasonic echo from a subject to receive a received signal. Output.

  Each ultrasonic transducer is, for example, a piezoelectric ceramic represented by PZT (lead zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene fluoride), or PMN-PT (magnesium niobate / lead titanate). It is constituted by a vibrator in which electrodes are formed on both ends of a piezoelectric body made of a piezoelectric single crystal represented by a solid solution).

  When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts, and pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and the synthesis of those ultrasonic waves. As a result, an ultrasonic beam is formed. In addition, each transducer generates an electric signal by expanding and contracting by receiving propagating ultrasonic waves, and these electric signals are output as ultrasonic reception signals.

  The transmission circuit 14 includes, for example, a plurality of pulsars, and is transmitted from the plurality of ultrasonic transducers of the transducer array 42 based on the transmission delay pattern selected according to the control signal from the control unit 36. The delay amount of each drive signal is adjusted so that the sound wave forms an ultrasonic beam, and then supplied to a plurality of ultrasonic transducers.

The reception circuit 16 amplifies the reception signals transmitted from the ultrasonic transducers of the transducer array 42 and performs A / D conversion, and then, based on the reception delay pattern selected according to the control signal from the control unit 36. According to the set sound speed or distribution of sound speed, the reception focus process is performed by adding each received signal with a delay. By this reception focus processing, reception data (sound ray signal) in which the focus of the ultrasonic echo is narrowed is generated.
The reception circuit 16 supplies the reception data to the image generation means 18, the cine memory 22, and the sound speed calculation unit 24.

The image generation unit 18 generates an ultrasonic image from the reception data supplied from the reception circuit 16.
The image generation unit 18 includes a signal processing unit 46, a DSC 48, an image processing unit 50, and an image memory 52.

  The signal processing unit 46 performs an envelope detection process on the received data generated by the receiving circuit 16, after performing attenuation correction according to the depth of the reflection position of the ultrasonic wave, and then performing an envelope detection process. A B-mode image signal, which is tomographic image information related to the tissue of, is generated.

A DSC (digital scan converter) 48 converts (raster conversion) the B-mode image signal generated by the signal processing unit 46 into an image signal according to a normal television signal scanning method.
Further, the DSC 48 converts a sound speed map signal supplied from a sound speed calculation unit 24 described later into an image signal in accordance with a normal television signal scanning method.

  The image processing unit 50 performs various necessary image processing such as gradation processing on the B-mode image signal input from the DSC 48, and then outputs the B-mode image signal to the display control unit 32 or stores it in the image memory 52. Store.

The display control unit 32 causes the display unit 34 to display an ultrasound diagnostic image based on the B-mode image signal that has been subjected to image processing by the image processing unit 50.
The display unit 34 includes a display device such as an LCD, for example, and displays an ultrasound diagnostic image under the control of the display control unit 32.

  The cine memory 22 sequentially stores the reception data output from the reception circuit 16. In addition, the cine memory 22 stores information related to the frame rate (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) input from the control unit 36 in association with the received data.

The sound speed calculation unit 24 is a part that calculates a local sound speed value in a tissue in a subject to be diagnosed under the control of the control unit 36 and generates a sound speed map indicating the sound speed value and position information.
Here, in the present invention, the sound speed calculation unit 24 performs the sound speed pre-measurement for measuring the environmental sound speed value, determines the presence or absence of a measurement error due to refraction, and then performs the sound speed main measurement for measuring the local sound speed value.
The sound speed calculation unit 24 includes a region-of-interest setting unit 60, a pre-measurement unit 62, and a main measurement unit 64.

The region-of-interest setting unit 60 sets a region of interest ROI in the subject, sets a two-dimensional grid in the region of interest ROI, and sets 2 in the depth direction and the azimuth direction (ultrasound scanning direction). A grid point X _ROI is set as a grid point to be measured in a plurality of dimensions.
The attention area setting unit 60 sets the attention area ROI in accordance with an input from the operation unit 38 by the operator.
In addition, the attention area setting unit 60 sets a plurality of lattice points X _ROI (lattice) according to the set attention area ROI.

FIG. 3 is a diagram schematically showing the set region of interest ROI and the lattice point X _ROI .
In FIG. 3, broken lines S <b> 1 to S <b> 13 conceptually show the sound rays of the ultrasonic beam transmitted from the transducer array 42. As shown in FIG. 3, the lattice point X _ROI is set for each sound ray in the region of interest _ROI in the azimuth direction (scanning direction of ultrasonic waves). In addition, at a shallow position in the depth direction, lattice points X _ROI are also set outside the region of interest _ROI .
In the illustrated example, three grid points X _ROI are set in the depth direction, but the present invention is not limited to this, and a plurality of points are set according to the resolution, processing time, and the like.
The attention area setting section 60 supplies information on the set attention area ROI and the plurality of grid points X _ROI to the pre-measurement section 62 and the main measurement section 64.

The pre-measurement unit 62 measures the environmental sound velocity values at several points among the plurality of lattice points X _ROI set by the region-of-interest setting unit 60 as a pre-measurement prior to the measurement of the local sound velocity value (main sound velocity measurement). This is a part for determining the presence or absence of a measurement error due to refraction.
The pre-measurement unit 62 includes a lattice point selection unit 66, an environmental sound speed calculation unit 68, and an environmental sound speed comparison unit 70.

The grid point selection unit 66 is a part that selects a pre-measurement grid point used for pre-measurement from a plurality of grid points X _ROI set by the region-of-interest setting unit 60. Here, the number of pre-measurement lattice points selected by the lattice point selection unit 66 is smaller than the number of lattice points at which the local sound velocity value is measured in the sonic velocity main measurement.
FIG. 4A is a diagram schematically showing selected pre-measurement lattice points.
As shown in FIG. 4A, the lattice point selection unit 66 has lattice points P1 and P3 located at both ends in the azimuth direction of the region of interest ROI at the shallowest position of the region of interest ROI, and a lattice located at the center thereof. Point P2 is selected as the pre-measurement grid point used for the pre-measurement.
The grid point selection unit 66 supplies information on the selected pre-measurement grid points P1 to P3 to the environmental sound speed calculation unit 68.

In the illustrated example, three grid points are selected as the pre-measurement grid points P1 to P3. However, the present invention is not limited to this, and may be two points or four or more points.
In addition, although the grid point at the shallowest position is selected as the pre-measurement grid points P1 to P3, the present invention is not limited to this, and if the selected grid point has a different azimuth position, the grid point of any depth is selected. May be. Note that it is preferable to select lattice points having the same depth as the pre-measurement lattice points.
In the illustrated example, the lattice points at both ends of the region of interest ROI and the lattice points located in the center in the azimuth direction are selected as the pre-measurement lattice points P1 to P3. However, the present invention is not limited to this. Any lattice point may be selected. For example, as shown in FIG. 4B, the grid point outside the region of _{interest XROI} and the grid point located in the center may be selected as the pre-measurement grid points P1 to P3.

The environmental sound speed calculation unit 68 is a part that calculates the environmental sound speed values at the pre-measurement grid points P1 to P3.
Here, the environmental sound speed value is the sound speed at which the contrast and sharpness of the image become the highest when the set sound speed is changed variously to form an ultrasonic image for each grid point based on the set sound speed. For example, as described in JP-A-8-317926, the environmental sound speed value can be determined based on the contrast of the image, the spatial frequency in the scanning direction, the variance, and the like.
The environmental sound speed calculation unit 68 supplies the calculated environmental sound speed values of the pre-measurement grid points P <b> 1 to P <b> 3 to the environmental sound speed comparison unit 70.

The environmental sound speed comparison unit 70 is a part that compares the environmental sound speed values of the pre-measurement grid points P1 to P3 obtained by the environmental sound speed calculation unit 68 and determines the presence or absence of a measurement error due to the influence of refraction.
The environmental sound speed comparison unit 70 obtains a difference Dv between the maximum value and the minimum value of the environmental sound speed values of the pre-measurement grid points P1, P2, and P3, and compares it with a predetermined threshold value.

5A and 5B are measurement examples of the environmental sound velocity values at the pre-measurement grid points P1, P2, and P3. In the example shown in FIG. 5, the predetermined threshold is 100 m / s.
As shown in FIG. 5A, when the difference Dv (the difference between P1 and P3 in the illustrated example) between the maximum value and the minimum value of the environmental sound speed value is smaller than a predetermined threshold value, the influence of refraction. It is determined that there is no measurement error, and a signal to that effect is supplied to the main measurement unit 64 and the control unit 36. In this case, the main measurement unit 64 measures the local sound speed value of each set grid point _XROI (main sound speed measurement).

  On the other hand, as shown in FIG. 5B, when the difference Dv (the difference between P1 and P2 in the illustrated example) between the maximum value and the minimum value of the environmental sound speed value is larger than a predetermined threshold value, It is determined that there is a measurement error due to the influence of refraction, and a signal to that effect is supplied to the main measurement unit 64 and the control unit 36. In this case, the main measurement unit 64 does not measure the local sound velocity value (main sound velocity measurement).

As described above, prior to the measurement of the local sound speed value (sound speed main measurement) of the set grid point X _ROI , as a pre-measurement, the environmental sound speed of a few grid points smaller than the number of grid points used in the sound speed main measurement is used. Measure the value, determine whether there is a measurement error due to the influence of refraction, perform the sonic speed measurement when it is determined that there is no measurement error, and if it is determined that there is a measurement error, measure the sonic speed Therefore, even if there is a measurement error and re-measurement is necessary, it can be determined before performing the sonic speed measurement. The time required for calculation can be shortened. In addition, since the presence or absence of the influence of refraction can be determined, measurement / calculation with less measurement error can be performed and the accurate local sound speed value can be obtained when performing the main sound speed measurement.
Further, in the sound speed pre-measurement, by comparing the environmental sound speed values of the lattice points at different positions in the azimuth direction, it is possible to suitably determine whether or not the sound speed value in the azimuth direction is disturbed due to refraction of sound waves.

  In the illustrated example, the predetermined threshold is set to 100 m / s. However, the present invention is not limited to this, and it is sufficient that the presence or absence of a measurement error due to the influence of refraction can be suitably determined. What is necessary is just to determine suitably according to performance etc.

  Further, when the difference Dv between the maximum value and the minimum value of the environmental sound speed value is larger than a predetermined threshold value, as shown in FIG. It is preferable to display in a distinguishable manner.

The main measurement unit 64 is a part for _obtaining a local sound velocity value at the set lattice point X _ROI when the pre-measurement unit 62 determines that there is no measurement error due to the influence of refraction.
The measurement unit 64 includes an environmental sound speed calculation unit 72 and a local sound speed calculation unit 74.

The environmental sound speed calculation unit 72 is a part that calculates the environmental sound speed value at each lattice point X _ROI . The environmental sound speed calculation unit 72 calculates the environmental sound speed value in the same manner as the environmental sound speed calculation unit 68. For each lattice point, focus calculation is performed based on the set sound speed to form an ultrasonic image, and the set sound speed is calculated. The sound speed value that maximizes the contrast and sharpness of the image when various changes are made is obtained as the environmental sound speed value.
The environmental sound speed calculation unit 72 supplies the obtained environmental sound speed value at each lattice point X _ROI to the local sound speed calculation unit 74.

The local sound speed calculation unit 74 is a part that calculates a local sound speed value at each lattice point X _ROI .
There is no particular limitation on the local sound speed value calculation method performed by the local sound speed calculation unit 74, and for example, it can be performed by the method described in Japanese Patent Application Laid-Open No. 2010-99452 filed by the applicant of the present application.

  As shown in FIG. 7A, this method focuses on a received wave Wx that reaches the transducer array 42 from a lattice point X that is a reflection point of the subject when ultrasonic waves are transmitted into the subject. Then, as shown in FIG. 7B, a plurality of lattice points arranged at equal intervals at a position shallower than the lattice point X, that is, a position close to the transducer array 42, are represented by lattice points A1, A2, ..., the combined wave Wsum of the received waves W1, W2, ... from the plurality of grid points A1, A2, ... that received the received wave from the grid point X is the Huygens principle. Thus, the local sound speed value at the lattice point X is obtained by using the fact that it matches the received wave Wx from the lattice point X.

  First, environmental sound speed values for all lattice points X, A1, A2,.

Next, the waveform of the virtual received wave Wx emitted from the lattice point X is calculated using the environmental sound velocity value for the lattice point X.
Further, the hypothetical local sound velocity value V at the lattice point X is variously changed to calculate virtual composite waves Wsum of the received waves W1, W2,... From the lattice points A1, A2,. . At this time, it is assumed that the sound velocity in the region Rxa between the lattice point X and each lattice point A1, A2,... Is uniform and equal to the local sound velocity value V at the lattice point X. The time until the ultrasonic wave propagated from the lattice point X reaches the lattice points A1, A2,... Is XA1 / V, XA2 / V,. Here, XA1, XA2,... Are the distances between the lattice points A1, A2,. Therefore, a virtual composite wave Wsum can be obtained by synthesizing the reflected waves emitted from the lattice points A1, A2,... Delayed by times XA1 / V, XA2 / V,. .

Next, errors between the plurality of virtual synthesized waves Wsum calculated by variously changing the hypothetical local sound velocity value V at the lattice point X and the virtual received wave Wx from the lattice point X are respectively calculated. The hypothetical local sound velocity value V that minimizes the error is calculated and determined as the local sound velocity value at the lattice point X. Here, as a method of calculating an error between the virtual synthesized wave Wsum and the virtual received wave Wx from the lattice point X, a method of obtaining a cross-correlation with each other, a delay obtained from the synthesized wave Wsum on the received wave Wx is used. A method of performing phase matching addition by multiplying, a method of performing phase matching addition by multiplying the synthesized wave Wsum by a delay obtained from the reception wave Wx, and the like can be employed.
As described above, the local sound velocity value at each lattice point X _ROI in the region of interest ROI can be obtained.
Local sound velocity calculation unit 74 generates a sound speed map in association with local sound speed value and position information of each lattice point _{X ROI} at each lattice point _{X ROI,} and supplies the DSC48 image generating means 18.

The control unit 36 controls each unit of the ultrasonic diagnostic apparatus based on a command input from the operation unit 38 by the operator.
The operation unit 38 is for an operator to perform an input operation, and can be formed from a keyboard, a mouse, a trackball, a touch panel, or the like.

The storage unit 40 stores an operation program and the like, and a recording medium such as a hard disk, a flexible disk, an MO, an MT, a RAM, a CD-ROM, and a DVD-ROM can be used.
The signal processing unit 46, the DSC 48, the image processing unit 50, the display control unit 32, and the sound speed calculation unit 24 are constituted by a CPU and an operation program for causing the CPU to perform various processes. You may comprise.

  The ultrasound diagnostic apparatus 10 may have a configuration in which a plurality of display modes are displayed and a desired image is displayed on the display unit 34 by selecting the display mode. For example, a mode in which an ultrasonic image (B-mode image) is displayed alone and a mode in which a local sound speed value is superimposed on the B-mode image (for example, a display in which color coding or luminance is changed according to the local sound speed value, or It is also possible to adopt a configuration in which the operator selects one of the display modes from the operation unit 38.

Next, the operation of the ultrasonic diagnostic apparatus 10 will be specifically described with reference to the flowchart of FIG.
When the operator abuts the ultrasonic probe 12 on the surface of the subject and starts measurement, an ultrasonic beam is transmitted from the transducer array 42 in accordance with the drive signal supplied from the transmission circuit 14, and the ultrasonic wave from the subject is transmitted. The transducer array 42 receives the echo and outputs a received signal.
The reception circuit 16 generates reception data from the reception signal and supplies it to the image generation means 18. The signal processing unit 46 of the image generating unit 18 processes the received data to generate a B-mode image signal. The DSC 48 performs raster conversion on the B-mode image signal, and the image processing unit 50 performs image processing, thereby generating an ultrasonic image. The generated ultrasonic image is stored in the image memory 52, and the display control unit 32 displays the ultrasonic image on the display unit 34 (S100).

Next, with reference to the displayed ultrasonic image, the operator operates the operation unit 38 to input a setting instruction for the region of interest ROI. The region-of-interest setting unit 60 sets the region of interest ROI according to an input instruction from the operation unit 38, and sets a plurality of lattice points X _ROI arranged two-dimensionally (S102).
When the region of interest ROI and the grid point X _ROI are set, the pre-measurement unit 62 measures the environmental sound speed values for a number of pre-measurement grid points that are smaller than the number of grid points used for the main sound speed measurement (S104). Then, it is determined whether or not the difference Dv between the maximum value and the minimum value of the environmental sound speed value at each pre-measurement grid point is equal to or smaller than a predetermined threshold (S106).

When the difference Dv between the maximum value and the minimum value of the environmental sound speed value at the pre-measurement grid point is equal to or less than a predetermined threshold, the main measurement unit 64 calculates the local sound speed value at each grid point X _ROI (S108). The calculation result is displayed on the display unit 34 as a sound velocity map (S110), and the measurement is terminated.

  On the other hand, when the difference Dv between the maximum value and the minimum value of the environmental sound speed value at the pre-measurement grid point is equal to or greater than a predetermined threshold value, guidance indicating that there is a measurement error as a result of the pre-measurement is displayed on the display unit 34. Then (S112), again, guidance on whether or not to perform the measurement is displayed on the display unit 34 (S114). When re-measurement is performed, measurement is performed from the B-mode image capturing (S100). On the other hand, when the re-measurement is not performed, the measurement is terminated.

As described above, the ultrasonic diagnostic apparatus 10 that performs the ultrasonic image generation method according to the present invention performs the measurement of the sonic velocity book as a pre-measurement prior to the measurement of the local sonic velocity value of the set lattice point _XROI (the sonic velocity main measurement). When it is determined that there is no measurement error by measuring the environmental sound velocity values of several lattice points that are smaller in the azimuth direction than the number of lattice points used for measurement, and determining the presence or absence of measurement errors due to the effects of refraction. In addition, if the sonic main measurement is performed and it is determined that there is a measurement error, the sonic main measurement is not performed, so it is possible to quickly grasp the presence or absence of the influence of refraction, and there is a measurement error and remeasurement is necessary. Even in such a case, since the determination can be made before the sonic main measurement is performed, the time required for the measurement / calculation can be shortened. In addition, since the presence or absence of the influence of refraction can be determined, measurement / calculation with less measurement error can be performed and the accurate local sound speed value can be obtained when performing the main sound speed measurement.

  In the illustrated example, the pre-measurement unit 62 selects the pre-measurement grid points P1 to P3 in one row of the same depth, compares the environmental sound velocity values, and determines whether there is an influence of refraction. However, the present invention is not limited to this, and the pre-measurement grid points may be selected at two or more different depths, and the environmental sound velocity values may be compared in each row.

FIG. 9 is a diagram conceptually showing the pre-measurement grid points.
As shown in FIG. 9, the lattice point selection unit 66 has lattice points P1 and P3 located at both ends in the azimuth direction of the region of interest ROI at the shallowest position of the region of interest ROI, and a lattice point P2 located at the center thereof. Is selected as a pre-measurement grid point, and at the deepest position of the region of interest ROI, the lattice points Q1 and Q3 located at both ends in the azimuth direction of the region of interest ROI and the lattice point Q2 located at the center thereof are pre-measured. Select as a grid point.

As described above, when the pre-measurement grid points are selected at a plurality of depths, the environmental sound speed comparison unit 70 determines the difference between the maximum value and the minimum value of the environmental sound speed values of the pre-measurement grid points P1 to P3. Is compared with a predetermined threshold value, and the difference between the maximum value and the minimum value of the environmental sound velocity values at the pre-measurement grid points Q1 to Q3 is determined and compared with the predetermined threshold value. As a result of comparison, when both are equal to or smaller than a predetermined threshold, the main measurement unit 64 may calculate the local sound speed value of each lattice point _XROI to obtain the sound speed map.

The present invention is basically as described above.
Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications may be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Ultrasonic diagnostic apparatus 12 Ultrasonic probe 14 Transmission circuit 16 Reception circuit 18 Image generation means 22 Cine memory 24 Sonic speed calculation part 32 Display control part 34 Display part 36 Control part 38 Operation part 40 Storage part 42 Transducer array 46 Signal processing part 48 DSC
DESCRIPTION OF SYMBOLS 50 Image processing part 52 Image memory 60 Area of interest setting part 62 Pre-measurement part 64 Main measurement part 66 Lattice point selection part 68, 72 Environmental sound speed calculation part 70 Environmental sound speed comparison part 74 Local sound speed calculation part

Claims (8)

An ultrasonic wave is generated from the transducer array of the ultrasonic probe, and an ultrasonic image is generated based on a reception signal output from the transducer array that has received an ultrasonic echo from the subject. In the sound wave image generation method,
When performing a sonic main measurement that captures a B-mode image, sets a region of interest, sets a grid in the set region of interest, and calculates local sound speed values at a plurality of lattice points,
Prior to the main sound speed measurement, as the sound speed pre-measurement, environmental sound speed values at two or more lattice points different in the ultrasonic scanning direction of the lattice are respectively measured.
An ultrasonic image generation method, characterized in that the sound speed main measurement is performed when a difference between a maximum value and a minimum value of the measured environmental sound speed value is equal to or less than a predetermined threshold value.   In the sound velocity pre-measurement, environmental sound velocity values at two or more lattice points in the ultrasonic scanning direction are measured at different depths, and the maximum and minimum environmental sound velocity values are measured at all depths. The ultrasonic image generation method according to claim 1, wherein the sonic main measurement is performed when the difference is equal to or less than a predetermined threshold.   The ultrasonic image generation method according to claim 1, wherein a grid having a size exceeding a set region of interest is set.   The ultrasonic image generation according to any one of claims 1 to 3, wherein the number of lattice points at which the environmental sound speed value is measured in the sound speed pre-measurement is smaller than the number of lattice points at which the local sound speed value is calculated in the sound speed main measurement. Method.   The ultrasonic image generation method according to claim 1, wherein the environmental sound velocity values measured in the sound velocity pre-measurement are compared, and a lattice point having the largest environmental sound velocity value is displayed so as to be distinguishable.   The warning or the measurement result of the environmental sound speed value is displayed when the difference between the maximum value and the minimum value of the environmental sound speed value measured in the sound speed pre-measurement exceeds a predetermined threshold value. An ultrasonic image generation method according to claim 1.   The ultrasonic image generation method according to claim 1, wherein a measurement result of a local sound speed value in the main sound speed measurement is displayed by being superimposed on the ultrasonic image. An ultrasonic wave is generated from the transducer array of the ultrasonic probe, and an ultrasonic image is generated based on a reception signal output from the transducer array that has received an ultrasonic echo from the subject. In the ultrasonic diagnostic imaging apparatus,
A region of interest setting section for setting a region of interest in the imaging region, setting a grid in the set region of interest, and setting a plurality of grid points;
A sound velocity pre-measurement unit that measures environmental sound velocity values of two or more lattice points different in the ultrasonic scanning direction of the lattice, and calculates a difference between a maximum value and a minimum value of the measured environmental sound velocity values;
A sound speed main measurement unit that calculates local sound speed values at a plurality of lattice points of the lattice when the difference between the maximum value and the minimum value of the environmental sound speed value calculated by the sound speed pre-measurement unit is equal to or less than a predetermined threshold; An ultrasonic diagnostic imaging apparatus comprising:

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