JP5588924B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus that performs imaging of an organ or the like in a living body by transmitting and 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.
By correcting the distortion of the ultrasonic image, for example, the measurement accuracy of various parts such as the measurement of the thickness of the blood vessel wall and the size of the tumor is improved.

For example, in Patent Document 1, a plurality of lattice points are set around a diagnostic region, and a local sound velocity value is calculated based on reception data obtained by transmitting and receiving an ultrasonic beam to each lattice point. An ultrasonic diagnostic apparatus 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

In the ultrasonic diagnostic apparatuses described in Patent Document 1 and Patent Document 2, a local sound velocity value in a living body can be obtained by transmitting and receiving an ultrasonic beam from an ultrasonic probe into a subject. It is possible to display the local sound velocity value information superimposed on the image.
However, when the ultrasonic beam is transmitted toward the set lattice point or region in order to obtain the local sound velocity value, the accurate sound speed is unknown, so that the set point or region is deviated. An ultrasonic beam is transmitted to the position. Therefore, an accurate local sound velocity value cannot be obtained, and the distortion of the ultrasonic image cannot be accurately corrected. Therefore, it is impossible to accurately measure various parts such as the measurement of the thickness of the blood vessel wall and the size of the tumor.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus that can more accurately diagnose various diagnostic sites in a subject such as measurement of the thickness of a blood vessel wall and the size of a tumor.

  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 diagnostic apparatus that generates an ultrasonic image based on a received signal, a sound velocity distribution detecting unit that detects a velocity distribution of ultrasonic waves in the subject, and the velocity distribution detected by the sound velocity distribution detecting unit There is provided an ultrasonic diagnostic apparatus comprising a differentiating means for differentiating in a sound wave transmission / reception direction.

Here, it is preferable that the differentiation result obtained by differentiating the sound velocity distribution by the differentiating unit is displayed superimposed on the ultrasonic image.
Further, it is preferable that the differentiating means arranges and outputs a sound speed differential value obtained by differentiating the sound speed distribution in a direction orthogonal to an ultrasonic wave transmission / reception direction.

Moreover, it is preferable that the differentiation result is converted into a color and superimposed on the ultrasonic image for display.
Alternatively, it is preferable that the differential result is converted into a density and displayed superimposed on the ultrasonic image.

Further, the differentiating unit may differentiate the ultrasonic wave transmission / reception direction after applying a smoothing filter to the ultrasonic wave transmission / reception direction to the velocity distribution detected by the sound velocity distribution detection unit.
Further, the ultrasonic image has an area setting unit that sets an area where the ultrasonic sound velocity can be regarded as constant, and the differentiating means has an ultrasonic sound velocity within the area set by the region setting unit. It is preferable to perform differentiation in the transmission / reception direction of ultrasonic waves as constant.
Further, it is preferable that the velocity distribution detected by the sound velocity distribution detecting means is displayed superimposed on the ultrasonic image.

  According to the ultrasonic diagnostic apparatus of the present invention having the above-described configuration, the ultrasonic velocity distribution in the subject is detected, the detected velocity distribution is differentiated in the ultrasonic transmission / reception direction, and the sound velocity differential value is calculated. Since the ultrasonic image is superimposed and displayed, the boundary of the diagnostic part in the living body can be obtained accurately, and the diagnostic part in the subject can be diagnosed more accurately.

1 is a block diagram conceptually showing the configuration of an ultrasonic diagnostic apparatus according to the present invention. (A) And (B) is a figure which shows the principle of a sound speed calculation typically. It is a figure which shows typically (A) and (B) an ultrasonic image. (A) is a graph schematically showing an example of the sound speed value along the line AA in FIG. 3 (A), and (B) is a graph schematically showing the sound speed differential value of (A). (A) And (B) is a graph which shows typically an example of a sound velocity value. It is a figure which shows an ultrasonic image typically. It is a graph which shows an example of a sound velocity value typically.

  Hereinafter, the ultrasonic diagnostic apparatus 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 the ultrasonic diagnostic apparatus 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 map generation unit 24, and a differential value calculation. A unit 26, a display control unit 32, a display unit 34, a control unit 36, an operation unit 38, and a storage unit 40.
The ultrasonic diagnostic apparatus 10 in the illustrated example has a configuration for capturing an ultrasonic image and generating a sound velocity map, and differentiating the generated sound velocity value in the transmission / reception direction of the ultrasonic wave to calculate a sound velocity differential value. It has the composition to do.

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. These ultrasonic transducers transmit an ultrasonic beam according to a drive signal supplied from the transmission circuit 14 at the time of imaging an ultrasonic image, and ultrasonic waves generated by light irradiation means irradiating light. The ultrasonic echo from the subject is received and a reception signal is 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 unit 18, the cine memory 22, and the sound speed map generation 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.

  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 map generation 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.
The calculation method of the local sound speed value performed by the sound speed map generation unit 24 is not particularly limited, and can be performed, for example, 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. 2A, 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. 2B, a plurality of lattice points A1, A2,... Are arranged at equal intervals at a position shallower than the lattice point X, that is, a position close to the transducer array 42, as shown in FIG. The combined wave Wsum of the received waves W1, W2,... Received from the plurality of grid points A1, A2,... Received from the point X is received from the grid point X according to Huygens' principle. This is a method of obtaining a local sound velocity value at the lattice point X by utilizing the fact that it matches the wave Wx.

  First, optimum sound speed values for all lattice points X, A1, A2,. Here, the optimum sound speed value means that, for each lattice point, an ultrasonic image is formed by performing a focus calculation based on the set sound speed and shooting, and the contrast and sharpness of the image are changed when the set sound speed is changed variously. Is the highest sound speed value. For example, as described in JP-A-8-317926, the optimum 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.

Next, the waveform of the virtual received wave Wx emitted from the lattice point X is calculated using the optimum 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 part in the subject can be calculated, and the sound velocity map in the subject can be generated.
The sound speed map generation unit 24 supplies the generated sound speed map to the differential value calculation unit 26.

  The differential value calculation unit 26 is a part that calculates the sound speed differential value by differentiating the sound speed map supplied from the sound speed map generation unit 24 in the ultrasonic wave transmission / reception direction.

FIGS. 3A and 3B are diagrams schematically illustrating an ultrasonic image in a case where the tissue is different between the target portion P indicated by an ellipse at the center and the peripheral portion thereof. FIG. 4 (A) is a graph schematically showing the sound speed value along the line AA in FIG. 3 (A), and FIG. 4 (B) is obtained by differentiating the sound speed value in FIG. 4 (A). It is a graph which shows typically the calculated sound velocity differential value.
As shown in FIG. 4A, the sound velocity values are different between different tissues in the living body, such as the target site P and its peripheral site. Therefore, the sound speed map is differentiated in the ultrasonic wave transmission / reception direction to obtain the sound speed differential value as shown in FIG. 4B, so that the boundary between different tissues from the position where the sound speed differential value changes, that is, The position of the boundary of the target part P can be obtained. In addition, the boundary between different tissues can be displayed by displaying the obtained sound speed differential value superimposed on the ultrasonic image.
Note that when displaying the sound speed differential value superimposed on the ultrasonic image, for example, as shown in FIG. Only the sound velocity differential value may be displayed. Alternatively, it may be displayed in different colors according to the value of the sound speed differential value, or the sound speed differential value may be converted into density (luminance) and displayed.

  As described above, by obtaining the local sound velocity value and correcting the distortion of the ultrasonic image, it is possible to improve the accuracy of measurement of various parts such as the measurement of the thickness of the blood vessel wall and the size of the tumor. However, when transmitting an ultrasonic beam to determine the local sound velocity value, the accurate sound velocity value is unknown, so the ultrasonic beam cannot be transmitted accurately to the set transmission position, and accurate The local sound velocity value cannot be obtained. Therefore, the distortion of the ultrasonic image cannot be accurately corrected, and each part cannot be measured accurately.

On the other hand, the present invention detects the ultrasonic velocity distribution in the subject, differentiates the detected velocity distribution in the transmission / reception direction of the ultrasonic wave, calculates the sonic differential value, and superimposes it on the ultrasonic image And display.
Here, when ultrasonic wave transmission / reception is performed to determine the local sound speed value, in the direction orthogonal to the ultrasonic wave transmission / reception direction, not only the absolute value of the sound speed value but also the relative value due to the influence of refraction. Changes in value cannot be accurately captured. On the other hand, in the ultrasonic transmission / reception direction, the change in the sound velocity value can be accurately captured. For this reason, in the present invention, the detected velocity distribution is differentiated in the transmission / reception direction of the ultrasonic wave and the sound velocity differential value is calculated, whereby the position where the sound velocity value has changed, that is, the position of the boundary between different tissues is determined. It can be determined accurately. Therefore, it is possible to accurately measure various parts such as the measurement of the thickness of the blood vessel wall and the size of the tumor.

  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 sound speed differential value is superimposed on a B-mode image (for example, a display in which color coding or luminance is changed according to the sound speed differential 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.

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, the sound speed map generation unit 24, and the differential value calculation unit 26 are composed of a CPU and an operation program for causing the CPU to perform various processes. However, they may be constituted by digital circuits.

Next, the operation of the ultrasonic diagnostic apparatus 10 will be described.
The operator brings the ultrasonic probe 12 into contact with the surface of the subject. In this state, an ultrasonic beam is transmitted from the transducer array 42 in accordance with the drive signal supplied from the transmission circuit 14, the ultrasonic echo from the subject is received by the transducer array 42, and a received 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 ultrasonic image is displayed on the display unit 34 by the display control unit 32.
The receiving circuit 16 supplies the received data to the cine memory 22 and the sound speed map generating unit 24. The sound speed map generation unit 24 calculates the local sound speed value of each part in the subject from the received data, generates a sound speed map, and supplies it to the differential value calculation unit 26. The differential value calculation unit 26 calculates a sound speed differential value from the sound speed map. The calculated sound speed differential value is raster-converted by the DSC 48, subjected to various image processing by the image processing unit 50, and then sent to the display control unit 32. Then, according to the display mode input from the operation unit 38 by the operator, the sound speed differential value is superimposed on the B-mode image and displayed on the display unit 34.

  As described above, the ultrasonic diagnostic apparatus 10 according to the present invention detects the ultrasonic velocity distribution in the subject, differentiates the detected velocity distribution in the transmission / reception direction of the ultrasonic wave, and calculates the differential velocity of sound, By superimposing and displaying on the ultrasound image, the position of the boundary between different tissues can be obtained accurately, and the measurement of various parts such as the thickness of the blood vessel wall and the size of the tumor can be accurately performed. Can do.

  In the illustrated example, the sound speed map obtained by mapping the local sound speed values of the entire ultrasonic image is differentiated in the transmission / reception direction of the ultrasonic waves to obtain the sound speed differential value, and the sound speed differential value equal to or higher than a predetermined first threshold value is obtained. However, the present invention is not limited to this, but the present invention is not limited to this, and one line or a few lines with the ultrasonic wave transmitting / receiving direction as the extending direction are displayed. Alternatively, the local sound speed value may be differentiated to obtain the sound speed differential value, and the change position of the local sound speed value may be displayed.

Further, as shown in FIG. 5A, when the noise included in the calculated local sound speed value distribution (sound speed map) is large, a smoothing filter is applied to the sound speed map, and FIG. It may be smoothed as shown, and then the sound velocity map may be differentiated in the ultrasonic wave transmission / reception direction.
The smoothing filter is not particularly limited, and various smoothing filters such as a moving average filter, a weighted average filter, or a low-pass filter can be used.

In addition, when a smoothing filter is applied to the sound speed map, the change in the local sound speed value becomes gentle, and the position of the boundary between different tissues may become ambiguous. Therefore, as shown in FIG. 6, as a configuration having an area setting unit that sets areas Ra and Rb in which the local sound velocity values can be regarded as constant on the displayed ultrasonic image, corresponding to each tissue, FIG. As shown in FIG. 4, the sound velocity differential value may be obtained by performing differentiation while keeping the local sound velocity values in the regions Ra and Rb set by the region setting unit constant. For example, the local sound velocity value in the set region is differentiated by regarding the average value of the local sound velocity values in the region as constant.
The region setting unit may set the region in accordance with an instruction from the operation unit 38 by the operator, or may be set automatically after smoothing.

  In addition, the sound speed map generated by the sound speed map generation unit 24 may be displayed superimposed on the ultrasonic image, and the sound speed map may be displayed superimposed on the ultrasonic image. Accordingly, the sound speed map may be displayed superimposed on the ultrasonic image.

  The signal processing unit 46 generates a B-mode image signal using the sound speed map generated by the sound speed map generation unit 24 when generating the B-mode image signal from the reception data supplied from the receiving circuit. You may do it. By generating a B-mode image signal using the sound speed map generated by the sound speed map generation unit 24, an ultrasonic image with less distortion can be generated.

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 velocity map generation part 26 Differential value calculation part 32 Display control part 34 Display part 36 Control part 38 Operation part 40 Storage part 42 Vibrator Array 46 Signal processor 48 DSC
50 Image processor 52 Image memory

Claims (7)

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 equipment,
A sound velocity distribution detecting means for detecting a velocity distribution of ultrasonic waves in the subject;
An ultrasonic diagnostic apparatus, comprising: a differentiating unit that differentiates the velocity distribution detected by the sound velocity distribution detecting unit in an ultrasound transmission / reception direction. The ultrasonic diagnostic apparatus according to claim 1, wherein the differentiating unit differentiates the velocity distribution and displays a differentiation result superimposed on the ultrasonic image. The ultrasonic diagnostic apparatus according to claim 2 , wherein the differentiation result is converted into a color and displayed superimposed on the ultrasonic image. The ultrasonic diagnostic apparatus according to claim 2 , wherein the differential result is converted into a concentration and displayed superimposed on the ultrasonic image. Said differentiating means, the velocity distribution in which the sound velocity distribution detecting unit detects, after multiplied by the smoothing filter to the ultrasonic transmitting and receiving direction, any one of claims 1 to 4 for performing the derivative of ultrasonic transmitting and receiving direction 1 The ultrasonic diagnostic apparatus according to item . On the ultrasonic image, having an area setting unit for setting an area where the sound speed of the ultrasonic wave can be regarded as constant,
Said differentiating means, in the region where the region setting unit has set, as an ultrasonic sound velocity is constant, the ultrasonic diagnosis according to any one of claims 1 to 5 for the differentiation of the ultrasonic transmitting and receiving direction apparatus. The sound velocity distribution detecting means and the velocity distribution is detected, the ultrasonic diagnostic apparatus according to any one of claims 1 to 6 for displaying superimposed on the ultrasonic image.

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