JP2012249929A - Ultrasonic image producing method - Google Patents

Abstract

Ultrasonic wave capable of quickly grasping the presence or absence of the influence of refraction, reducing the time required for measurement / calculation, performing measurement / calculation with less measurement error, and obtaining an accurate local sound velocity value An image generation method and apparatus are provided.
A transducer array having transducers arranged two-dimensionally, wherein a plurality of pieces of information on a two-dimensional tomographic plane can be acquired, and a B-mode image is captured, When performing the sonic main measurement to set the region of interest, set the grid to the set region of interest, and calculate the local sound speed value at multiple lattice points, prior to the sound speed main measurement, In each plane, the environmental sound velocity values of two or more lattice points different in the ultrasonic scanning direction of the lattice are measured, and the measured sound velocity difference between the maximum value and the minimum value of the measured environmental sound velocity values is less than a predetermined threshold value. The above-mentioned problem is solved by performing the sonic main measurement on the tomographic plane.
[Selection] Figure 1

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 apparatus capable of obtaining 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 the ultrasonic image generating method for generating an ultrasonic image based on a received signal, the transducer array is a transducer array having transducers arranged in a two-dimensional manner, and the transducer array is arranged according to the arrangement of the transducers. A plurality of information of two-dimensional tomographic planes can be acquired in a direction orthogonal to the tomographic plane, a B-mode image is captured, a region of interest is set, and a grid is set in the set region of interest. When performing the sonic main measurement to calculate the local sound velocity values at a plurality of lattice points, prior to the sonic main measurement, as a sonic pre-measurement, in each of the plurality of tomographic planes, in the ultrasonic scanning direction of the lattice 2 or more different grids Each of the environmental sound speed values is measured, and the sound speed main measurement is performed on the tomographic plane where the difference between the measured environmental sound speed values between the maximum value and the minimum value is equal to or less than a predetermined threshold value. A sound image generation method is provided.

Here, it is preferable that the sonic velocity main measurement is performed on a tomographic plane having the smallest measured sonic velocity difference when the sonic velocity pre-measurement is performed.
Alternatively, in the sound speed pre-measurement, the environmental sound speed value is measured, and the difference between the measured sound speed difference and the predetermined threshold is sequentially performed on each tomographic plane, and the measured sound speed difference is initially equal to or less than the predetermined threshold. The sonic main measurement is preferably performed on the tomographic plane.

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. It is preferable that the sonic main measurement is performed on a tomographic plane in which the difference between the two is equal to or less than a predetermined threshold.
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 when measuring the environmental sound speed value at each tomographic plane in the sound speed pre-measurement is smaller than the number of lattice points calculating the local sound speed value in the sound speed main measurement.
In addition, it is preferable to display the lattice points having the highest frequency at which the environmental sound speed value at the time of the sound speed pre-measurement is maximum.
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 reception signal to be output, the transducer array includes transducers arranged two-dimensionally, and two-dimensionally according to the arrangement of the transducers. A two-dimensional transducer array for acquiring a plurality of tomographic plane information in a direction orthogonal to the tomographic plane, setting a region of interest in the imaging region, and setting a grid in the set region of interest Then, an area of interest setting unit for setting a plurality of lattice points, and an environmental sound speed value of two or more lattice points different from each other in the ultrasonic scanning direction of the lattice on the plurality of tomographic planes. Measurement sound that is the difference between the maximum and minimum values A sonic speed pre-measurement unit that calculates a difference, and a sonic speed book that calculates local sound speed values at a plurality of lattice points of the lattice on a tomographic plane where the measured sound speed difference calculated by the sonic speed pre-measurement unit is a predetermined threshold value or less. An ultrasonic diagnostic imaging apparatus comprising a measurement unit.

  According to the ultrasonic image generation method and the ultrasonic diagnostic imaging apparatus of the present invention having the above-described configuration, the transducer array is a transducer array having transducers arranged two-dimensionally, and the transducer array Accordingly, it is possible to acquire a plurality of information of two-dimensional tomographic planes in a direction perpendicular to the tomographic plane, and prior to the sonic velocity main measurement, as a sonic pre-measurement, in each of the plurality of tomographic planes, ultrasonic waves of the lattice Measure the ambient sound velocity values at two or more grid points that are different in the scanning direction, and measure the actual sound velocity at the tomographic plane where the measured sound velocity difference between the maximum and minimum measured environmental sound velocity values is less than or equal to a predetermined threshold. Therefore, it is possible to quickly grasp the presence or absence of the influence of refraction, reduce the time required for measurement / calculation, perform measurement / calculation with less measurement error, and obtain an accurate local sound velocity value.

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 a two-dimensional vibrator array and a tomographic plane typically. 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 an example of the configuration of an ultrasonic diagnostic apparatus that implements the ultrasonic image generation method of the present invention, and FIG. 2 is a block diagram conceptually showing the configuration of the sound speed calculation unit 24. It is.
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 two-dimensional transducer array 42.
The transducer array 42 has a plurality of ultrasonic transducers (vibrators) arranged 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.

In FIG. 3, a two-dimensional transducer array 42 and tomographic planes H ₁ , H ₂ , H ₃ ,... Hx. ..Hn is schematically shown.
As shown in FIG. 3, the tomographic plane is a plane parallel to the ultrasonic scanning direction (AZ direction) according to the arrangement of the ultrasonic transducers of the transducer array 42, and is perpendicular to the AZ direction and the depth direction. A plurality of directions are set in different directions (EL directions).
In the present invention, ultrasonic waves can be transmitted and received at each tomographic plane, and ultrasonic images can be captured and sound velocity values (local sound velocity values, environmental sound velocity values) can be measured.

  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 velocity calculation unit 24 performs a sound velocity pre-measurement for measuring the environmental sound velocity value, determines the presence or absence of a measurement error due to refraction, and then measures the local sound velocity value (main sound velocity measurement). .
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. 4 is a diagram schematically showing a tomographic plane in which the region of interest ROI and the lattice point X _ROI are set.
In FIG. 4, 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. 4, the lattice point X _ROI is set for each sound ray in the region of interest _ROI in the azimuth direction (ultrasonic scanning direction (AZ direction)). 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.

Prior to the measurement of the local sound velocity value (main sound velocity measurement), the pre-measurement unit 62 performs the sound velocity pre-measurement for several points among the plurality of lattice points X _ROI set by the region-of-interest setting unit 60 in each tomographic plane Hx. This is a part that measures the environmental sound velocity value and determines 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, an environmental sound speed comparison unit 70, and a cross-section selection unit 76.

The lattice point selection unit 66 is a part that selects a pre-measurement lattice point used for the sonic pre-measurement from the plurality of lattice 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. 5A is a diagram schematically illustrating selected pre-measurement grid points.
As shown in FIG. 5A, the lattice point selection unit 66 has lattice points Px1, Px3 located at both ends of the azimuth direction of the region of interest ROI at the shallowest position of the region of interest ROI in each tomographic plane Hx. The grid point Px2 located at the center is selected as the pre-measurement grid point used for the sonic pre-measurement.
The grid point selection unit 66 supplies information on the selected pre-measurement grid points Px1 to Px3 to the environmental sound speed calculation unit 68.

In the illustrated example, three grid points are selected as the pre-measurement grid points Px1 to Px3. 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 Px1 to Px3, the present invention is not limited to this, and if the grid point to be selected has a different position in the azimuth direction, 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 Px1 to Px3. However, the present invention is not limited to this. Any lattice point may be selected. For example, as shown in FIG. 5 (B), and the lattice points in the outer region of interest X _ROI, a lattice point located at the center thereof, may be selected as a pre-measurement grid points Px1～Px3.

The environmental sound speed calculation unit 68 is a part that calculates the environmental sound speed value at the pre-measurement grid points Px1 to Px3 in each tomographic plane Hx.
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 Px1 to Px3 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 Px1 to Px3 obtained by the environmental sound speed calculation unit 68 in each tomographic plane Hx and determines the presence or absence of a measurement error due to the influence of refraction. is there.
The environmental sound speed comparison unit 70 obtains a difference (measured sound speed difference) DvX between the maximum value and the minimum value of the environmental sound speed values of the pre-measurement grid points Px1, Px2, and Px3, and compares it with a predetermined threshold value.

6A and 6B are measurement examples of the environmental sound velocity values at the pre-measurement grid points Px1, Px2, and Px3. In FIG. 6, for the sake of simplicity, an example of measurement of the environmental sound speed value for three tomographic planes is shown. In the example shown in FIG. 6, the predetermined threshold is 100 m / s.
In the example shown in FIG. 6 (A), measured sound velocity difference Dv1 in the tomographic plane _{H 1} is approximately 160 m / s, greater than a predetermined threshold value, the measurement speed of sound differential Dv2 and Dv3 in the tomographic plane _{H 2} and _{H 3} are , About 70 m / s and about 50 m / s, respectively, which are smaller than the predetermined threshold. In this case, the tomographic plane H _1, it is determined that there is a measurement error due to the influence of refraction, the tomographic plane H ₂ and H _3, measurement error due to the effect of refraction is determined that there is no.

On the other hand, in the example shown in FIG. 6B, the measured sound speed differences Dv1, Dv2, and Dv3 at the tomographic planes H ₁ , H _2, and H ₃ are about 160 m / s, about 130 m / s, and about 110 m / s, respectively. Yes, greater than a predetermined threshold. In this case, it is determined that there is a measurement error due to the influence of refraction at the tomographic planes H ₁ , H ₂ and H ₃ .
The environmental sound speed comparison unit 70 supplies the determination result and the information on the measured sound speed difference DvX to the cross-section selection unit 76.

  The cross section selection unit 76 selects a tomographic plane Hx on which the sonic speed main measurement is performed based on the information supplied from the environmental sound speed comparison unit 70. Specifically, the measured sound speed difference DvX is compared by comparing the measured sound speed difference DvX at each tomographic plane Hx for the cross-sectional layer Hx determined by the environmental sound speed comparison unit 70 to have no measurement error due to the influence of refraction. The smallest tomographic plane Hx is selected as the tomographic plane on which the sonic main measurement is performed.

For example, in the example shown in FIG. 6A, when the environmental sound speed comparison unit 70 compares the measured sound speed differences Dv2 and Dv3 of the cross-sectional layers H ₂ and H ₃ determined as having no measurement error due to the influence of refraction, since towards Dv3 is small, the tomographic plane H _3, selected as tomographic plane to perform acoustic velocity this measurement.
On the other hand, as in the example shown in FIG. 6B, when the measured sound speed difference DvX of all the tomographic planes is larger than a predetermined threshold, no tomographic plane is selected.
The cross-section selection unit 76 supplies information on the selected tomographic plane or information indicating that there is no appropriate tomographic plane to the main measurement unit 64 and the control unit 36. The main measurement unit 64 performs the sonic main measurement on the tomographic plane selected by the cross-section selection unit 76. When there is no appropriate tomographic plane, the main measurement unit 64 does not perform the sonic main measurement.

In this way, using a two-dimensional transducer array, a plurality of information of two-dimensional tomographic planes can be acquired in a direction orthogonal to the tomographic plane, and the local sound velocity value of the set lattice point X _ROI can be obtained. Prior to the measurement (main sound speed measurement), as the sound speed pre-measurement, the environmental sound speed values of several lattice points less than the number of lattice points used in the sound speed main measurement are measured in each of the plurality of tomographic planes. Determine the presence or absence of measurement error due to influence, perform the sonic main measurement on the tomographic plane determined to have no measurement error, and if it is determined that there is a measurement error on all the tomographic planes, measure the sonic velocity main measurement. Therefore, even if there is a measurement error and re-measurement is necessary, it can be determined before performing the sonic speed measurement. Reduce the time required for computation be able to. In addition, since the sonic velocity main measurement is performed by determining the presence or absence of the influence of refraction and selecting the tomographic plane determined to have no measurement error, the measurement / calculation with a small measurement error is performed when performing the sonic velocity main measurement. And an accurate local sound velocity value can be obtained.
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 measured sound speed difference DvX is larger than a predetermined threshold value on all the tomographic planes, as shown in FIG. 7, it is possible to discriminate the lattice point having the highest frequency at which the environmental sound speed value becomes the maximum value. It is preferable to display the result of the sonic pre-measurement.

In the illustrated example, the tomographic plane Hx having the smallest measured sound speed difference DvX is selected as the tomographic plane for performing the main sound speed measurement. However, the present invention is not limited to this, and the measured sound speed difference DvX is a predetermined threshold value. Any tomographic plane Hx may be selected as long as it is smaller than the tomographic plane Hx.
In addition, it is preferable to select the tomographic plane Hx having the smallest measured sound speed difference DvX as the tomographic plane for performing the main sound speed measurement. As a result, a tomographic plane with a smaller measurement error due to the influence of refraction can be selected.

Further, in the illustrated example, the measurement sound speed difference DvX is obtained for all the tomographic planes Hx, and after determining the presence or absence of the measurement error for each tomographic plane Hx, from among the tomographic planes Hx determined to have no measurement error, Although the configuration is such that the tomographic plane Hx for performing the sonic velocity main measurement is selected, the present invention is not limited to this, and for each tomographic plane Hx, the environmental sonic velocity value is measured, the measured sonic velocity difference DvX is calculated, and the measured sonic velocity difference. The comparison between DvX and a predetermined threshold value may be sequentially performed, and the tomographic plane Hx in which the measured sound speed difference DvX first becomes equal to or smaller than the predetermined threshold value may be selected as the tomographic plane Hx on which the sonic velocity main measurement is performed.
After obtaining the measurement sound speed difference DvX for all tomographic planes Hx and determining the presence or absence of measurement errors, the configuration for selecting the tomographic plane Hx for performing the sonic velocity main measurement is to select a tomographic plane with a smaller measurement error due to refraction. It is preferable in that it can be performed. On the other hand, the configuration in which the determination of the presence or absence of measurement error is sequentially performed, and the tomographic plane Hx where the measured sound speed difference DvX first becomes equal to or less than a predetermined threshold is selected as the tomographic plane Hx for performing the main measurement of the sonic speed reduces the calculation time. It is preferable in that it can be performed.

The main measurement unit 64 is a part for _obtaining a local sound velocity value at the set lattice point X _ROI on the tomographic plane determined by the pre-measurement unit 62 as having 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. 8A, 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. 8B, 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 on the selected tomographic plane Hx.
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 information on the sound velocity map is converted into an image signal by the DSC 48 and displayed on the display unit 34.

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 (sound speed map) is superimposed on the B-mode image (for example, color coding or luminance is changed according to the local sound speed value). Or a display in which points having the same local sound velocity value are connected by a line), and the operator may select 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.
First, a B-mode image is taken at an arbitrary tomographic plane.
Specifically, when the operator contacts the surface of the subject with the ultrasonic probe 12 and starts measurement, the ultrasonic wave is emitted from the transducer array 42 according to the drive signal supplied from the transmission circuit 14 on an arbitrary tomographic plane. The beam is transmitted, the ultrasonic echo from the subject is received by the transducer array 42, and a reception signal is output.
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 for all tomographic planes Hx in response 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 determines a number of pre-measurement grid points that are smaller than the number of grid points used for the sonic main measurement for all tomographic planes Hx. The environmental sound velocity value is measured (S104), and it is determined whether or not the measured sound velocity difference DvX is equal to or smaller than a predetermined threshold value in each tomographic plane Hx (S106).

  When there is a tomographic plane Hx in which the measured sound speed difference DvX is equal to or less than a predetermined threshold, the tomographic plane Hx used for the main sound speed measurement is selected from the tomographic planes Hx in which the measured sound speed difference DvX is equal to or less than the predetermined threshold (S107). ). When the tomographic plane Hx to be subjected to the sonic main measurement is selected, a B-mode image (ultrasonic image) is captured on the selected tomographic plane Hx, and the main measurement unit 64 performs the sonic main measurement (S108). The ultrasonic image and the measurement result of the sound velocity value are displayed on the display unit 34 (S110), and the measurement ends.

  On the other hand, if the measured sound speed difference DvX is greater than or equal to a predetermined threshold value in all the cross sections, guidance indicating that there is a measurement error as a result of the sound speed pre-measurement is displayed on the display unit 34 (S112), and the measurement is performed again. Information on whether or not to perform the operation is displayed on the display unit 34 (S114). When re-measurement is performed, measurement is performed from imaging of a B-mode image used for setting the ROI (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 uses the two-dimensional transducer array to convert the information of the two-dimensional tomographic plane in the direction orthogonal to the tomographic plane. In a plurality of obtainable configurations, prior to the measurement of the local sound velocity value (main sound velocity measurement) of the set lattice point X _ROI , as the sound velocity pre-measurement, the lattice point used for the sound velocity main measurement is measured on each of the plurality of tomographic planes. Measure the environmental sound velocity values at a few grid points at different positions in the azimuth direction, determine the presence or absence of measurement errors due to the effects of refraction, and determine the sound velocity at the tomographic plane determined to have no measurement errors. If this measurement is performed and it is determined that there is a measurement error on all the tomographic planes, the sonic main measurement is not performed, so it is possible to quickly grasp the influence of refraction, and there is a measurement error. When measurement is required However, since the determination can be made before the sonic velocity main measurement is performed, the time required for the measurement / calculation can be shortened. In addition, since the sonic velocity main measurement is performed by determining the presence or absence of the influence of refraction and selecting the tomographic plane determined to have no measurement error, the measurement / calculation with a small measurement error is performed when performing the sonic velocity main measurement. And an accurate local sound velocity value can be obtained.

  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. 10 is a diagram conceptually showing the pre-measurement grid points.
As shown in FIG. 10, 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 less than a predetermined threshold, it is determined that the tomographic plane has no measurement error due to the influence of refraction.

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 76 Section selection part

Claims (10)

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,
The transducer array is a transducer array having transducers arranged two-dimensionally, and information on a two-dimensional tomographic plane is set in a direction orthogonal to the tomographic plane according to the arrangement of the transducers. , Multiple, obtainable,
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 sonic main measurement, as a sonic pre-measurement, environmental sound speed values at two or more lattice points different in the ultrasonic scanning direction of the lattice are measured on each of the plurality of tomographic planes,
A method for generating an ultrasonic image, characterized in that the sound speed main measurement is performed on the tomographic plane where a measured sound speed difference, which is a difference between a maximum value and a minimum value of a measured environmental sound speed value, is equal to or less than a predetermined threshold value.   The ultrasonic image generation method according to claim 1, wherein the sound speed main measurement is performed on a tomographic plane having the smallest difference in the measured sound speed when the sound speed pre-measurement is performed.   In the sound speed pre-measurement, the environmental sound speed value is measured and the difference between the measured sound speed difference and the predetermined threshold value is sequentially performed on each tomographic plane, and the measured sound speed difference is initially equal to or lower than the predetermined threshold value. The ultrasonic image generation method according to claim 1, wherein the sonic main measurement is performed on a tomographic plane.   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 on a tomographic plane where 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 number of lattice points when measuring the environmental sound speed value at each tomographic plane in the sound speed pre-measurement is smaller than the number of lattice points calculating the local sound speed value in the main sound speed measurement. The ultrasonic image generation method as described.   The ultrasonic image generation method according to any one of claims 1 to 6, wherein a lattice point having the highest frequency at which the environmental sound speed value during the sound speed pre-measurement is maximum is displayed in a distinguishable manner.   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 velocity value in the sound velocity main measurement is displayed 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,
The transducer array includes transducers arranged two-dimensionally, and acquires a plurality of pieces of information on a two-dimensional tomographic plane in a direction orthogonal to the tomographic plane according to the arrangement of the transducers. A two-dimensional transducer array,
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;
On the plurality of tomographic planes, environmental sound velocity values of two or more lattice points of the lattice that are different in the ultrasonic scanning direction are measured, and a measured sound velocity difference that is a difference between a maximum value and a minimum value of the measured environmental sound velocity values A sound velocity pre-measurement unit for calculating
A sound velocity main measurement unit that calculates local sound velocity values at a plurality of lattice points of the lattice on a tomographic plane in which the measured sound velocity difference calculated by the sound velocity pre-measurement unit is equal to or less than a predetermined threshold value. Ultrasound image diagnostic equipment.

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