JP2013244138A - Ultrasonic diagnostic apparatus and sound velocity display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a higher-reliability sound velocity map when acquiring a local sound velocity inside a specimen and displaying the sound velocity map based on the local sound velocity.SOLUTION: An ultrasonic diagnostic apparatus includes: a B mode image generation part 15 generating a B mode image based on a reception signal acquired by the transmission/reception of an ultrasonic wave into a subject by an ultrasonic probe 10; a sound velocity map generation part 18 acquiring a local sound velocity inside the subject based on the reception signal acquired by the ultrasonic probe 10, and generating a sound velocity map based on the acquired local sound velocity; a display control part 19 making the sound velocity map generated by the sound velocity map generation part 18 be displayed; and a display region decision part 17 deciding a non-display region of the sound velocity map based on the B mode image generated by the B mode image generation part 15. The display control part 19 does not make the sound velocity map be displayed about the non-display region.

Description

  The present invention relates to an ultrasonic diagnostic apparatus and a sound speed display method for acquiring a local sound speed in a subject using ultrasonic waves and displaying a sound speed map based on the local sound speed.

  Conventionally, there has been proposed an ultrasonic diagnostic apparatus that acquires internal information of a subject by transmitting and receiving ultrasonic waves to and from the subject.

  The principle of ultrasonic imaging in this ultrasonic diagnostic apparatus is as follows. Ultrasound is reflected at the boundary between regions having different acoustic impedances, such as the boundary between structures in the subject. Therefore, the ultrasonic wave is present in the subject by transmitting the ultrasonic wave into the subject such as a human body, receiving the ultrasonic echo generated in the subject, and obtaining the reflection position and the reflection intensity where the ultrasonic echo is generated. The contour of a structure (for example, a viscera or a diseased tissue) can be extracted.

  Thus, the ultrasonic image displayed in the conventional ultrasonic diagnostic apparatus is a tomographic image obtained by performing luminance modulation according to the intensity of the received signal of the ultrasonic echo reflected from the living body. Therefore, this tomographic image represents the tissue shape in the subject and is not appropriate for representing the tissue properties in the subject.

  On the other hand, it is generally known that the elastic modulus of each part of the tissue in the subject gives information on the tissue properties, and the distribution of the value corresponding to the elastic modulus is determined based on the received signal obtained by transmitting and receiving ultrasonic waves. A method of displaying as an image (elastography) has also been proposed. For example, since the tumor is generally harder than other tissues, the elastic modulus is increased.

  Further, since the sound velocity is given as a function of the elastic modulus, the clinical value indicated by the sound velocity of each part of the tissue in the living body is considered to be equivalent to the elastic modulus. Therefore, since it can be inferred that the sound speed map representing the distribution state of sound speed has clinical value as well as the tissue elasticity image, various methods for obtaining the sound speed in the subject have been proposed (Patent Document 1). To Patent Document 4).

JP 2010-207490 A JP 2010-99452 A JP 2010-246692 A JP 2012-71042 A

  Here, the sound velocity in the subject is also calculated based on the received signal by transmitting and receiving ultrasonic waves into the subject. However, there are scatterers inside the subject such as blood vessels, gallbladder, and benign cysts. When there is a low echo area with a small amount of noise, the signal strength of the received signal is low in the low echo area, so that the accuracy of the local sound speed value is lowered, and the reliability of the sound speed map may be lowered.

  On the other hand, if there is a high echo area where a very strong reflector such as a bone exists in the subject, the signal range of the received signal increases, so that the measurement range is saturated in the AD conversion process. There's a problem. The local sound speed is calculated based on the sharpness of the image generated from the received signal. However, if the received signal is saturated as described above, the sharpness cannot be accurately determined. The speed of sound cannot be acquired, and the reliability of the speed map may be reduced.

  In addition, when there is a region with a large amount of motion in the image generated from the received signal due to body movement due to a heartbeat or the like in the subject, or vibration of the ultrasonic probe, motion artifacts are generated in the image. As described above, since the local sound speed is calculated based on the sharpness of the image generated from the received signal, when there is a motion artifact in the image, the sharpness of the image cannot be accurately determined. An accurate local sound speed cannot be acquired, and the reliability of the sound speed map may be reduced.

  The present invention has been made in view of the above problems, and when acquiring the local sound speed in the specimen and displaying the sound speed map based on the local sound speed, it is possible to display a more reliable sound speed map. An object of the present invention is to provide an ultrasonic diagnostic apparatus and a sound speed display method.

  The ultrasonic diagnostic apparatus according to the present invention is acquired by a B-mode image generation unit that generates a B-mode image based on a reception signal acquired by transmitting and receiving ultrasonic waves into a subject by an ultrasonic probe, and an ultrasonic probe. A sound speed map generating unit that acquires a local sound speed in the subject based on the received signal and generates a sound speed map based on the acquired local sound speed, and a display for displaying the sound speed map generated by the sound speed map generating unit A control unit, and a display region determination unit that determines a non-display region of the sound speed map based on the B mode image generated by the B mode image generation unit, and the display control unit displays the sound velocity map for the non-display region. It is characterized by not being displayed.

  In the ultrasonic diagnostic apparatus according to the present invention, the display area determination unit determines that an area having a pixel value smaller than the low echo area determination threshold among the pixel values constituting the B-mode image is a non-display area. You can do it.

  Further, the display area determination unit may determine an area having a pixel value larger than a high echo area determination threshold among the pixel values constituting the B-mode image as a non-display area.

  Further, the display area determination unit can determine the non-display area based on the image obtained by performing the blurring process on the B-mode image.

  Further, the display area determination unit acquires information indicating the amount of motion of the subject in the B-mode image based on the B-mode images of different frames, and displays the non-display area based on the acquired information indicating the amount of movement. Can be determined.

  Further, the sound speed map generation unit can be configured not to acquire a local sound speed or a sound speed map for the non-display area.

  Further, the sound velocity map generation unit is configured to generate a local sound velocity in the subject based on a reception signal transmitted and received for sound velocity acquisition by the ultrasonic probe at a timing different from the reception signal acquired to generate the B-mode image. You can get that.

  Further, the sound speed map generation unit can acquire the local sound speed in the subject based on the received signal acquired to generate the B-mode image.

  In addition, the display control unit can display the sound velocity map and the B-mode image so as to overlap each other.

  The sound speed display method of the present invention generates a B-mode image based on a reception signal acquired by transmitting / receiving ultrasonic waves into a subject using an ultrasonic probe, and generates a B-mode image based on the reception signal acquired by the ultrasonic probe. In a sound speed display method for acquiring a local sound speed in a specimen, generating a sound speed map based on the acquired local sound speed, and displaying the generated sound speed map, a non-display area of the sound speed map is determined based on a B-mode image. The sound speed map is not displayed for the non-display area.

  According to the ultrasonic diagnostic apparatus and the sound speed display method of the present invention, the local sound velocity in the subject is acquired based on the received signal acquired by transmitting and receiving the ultrasonic wave into the subject by the ultrasonic probe, and the acquired When the sound speed map is generated and displayed based on the local sound speed, the non-display area of the sound speed map is determined based on the B mode image, and the sound speed map is not displayed for the non-display area. If the low echo area, the high echo area, or the motion area as described above is determined as a non-display area using an image, and the sound speed map is not displayed for these areas, the sound speed based on the local sound speed with low accuracy is used. Since the map can be prevented from being displayed, a more reliable sound velocity map can be displayed.

1 is a block diagram showing a schematic configuration of an ultrasonic diagnostic system using an embodiment of an ultrasonic diagnostic apparatus of the present invention. The figure which shows an example of a B-mode image and a B-mode image which has been blurred The figure which shows an example of the correlation coefficient image produced | generated based on the B mode image of two adjacent frames The figure for demonstrating an example of the acquisition method of local sound speed The flowchart for demonstrating the effect | action of the ultrasound diagnosing system using the ultrasound diagnosing device of this invention The figure which shows the example which displayed the sound speed map, without performing determination of a display area and a non-display area with respect to B mode image containing the gallbladder which is a low echo area | region The figure which shows the example which performed the determination of the display area and the non-display area | region, and displayed the sound speed map with respect to B mode image containing the gall bladder which is a low echo area | region The figure which shows the example which displayed the sound speed map, without performing determination of a display area and a non-display area with respect to B mode image of the liver vicinity including the motion area | region by a pulsation The figure which shows the example which performed the determination of the display area and the non-display area | region, and displayed the sound speed map with respect to B mode image of the liver vicinity including the motion area | region by a pulsation The block diagram which shows schematic structure of the ultrasound diagnosing system using other embodiment of the ultrasound diagnosing device of this invention. The figure for demonstrating the example which makes an area | region deeper than a high echo area | region into a non-display area | region

  Hereinafter, an ultrasonic diagnostic system 1 using an embodiment of an ultrasonic diagnostic apparatus and a sound velocity display method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic diagnostic system 1 of the present embodiment.

  As shown in FIG. 1, the ultrasound diagnostic system 1 of the present embodiment includes an ultrasound probe 10, a transmission control unit 11, a reception signal processing unit 12, a reception signal storage unit 13, a reception control unit 14, and a B-mode image generation unit. 15, a scanning control unit 16, a display area determination unit 17, a sound speed map generation unit 18, a display control unit 19, and a monitor 20.

  The ultrasonic probe 10 transmits ultrasonic waves toward a diagnostic site in a subject and receives ultrasonic waves reflected in the body. The ultrasonic probe 10 of the present embodiment includes a plurality of ultrasonic transducers constituting a one-dimensional ultrasonic transducer array, and each ultrasonic transducer is a vibration in which electrodes are formed at both ends of a piezoelectric element such as PZT, for example. Consists of children. This electrode is connected to the reception signal processing unit 12 and the transmission control unit 11 by a signal line. A voltage corresponding to the drive pulse voltage signal output from the transmission control unit 11 is applied to this electrode, and the vibrator generates ultrasonic waves in response to this voltage application. The vibrator generates an electrical signal when receiving the reflected ultrasonic wave, and outputs the electrical signal to the received signal processing unit 12 as a received signal.

  The transmission control unit 11 outputs a drive pulse voltage signal to each ultrasonic transducer of the ultrasonic probe 10 based on the transmission delay time output from the scanning control unit 16, and an ultrasonic wave corresponding to the transmission delay time. Is transmitted from the transducer of each ultrasonic transducer to transmit ultrasonic waves that converge at a predetermined focal point from the ultrasonic probe 10.

  The reception signal processing unit 12 includes a plurality of amplifiers and a plurality of A / D converters provided corresponding to the respective ultrasonic transducers of the ultrasonic probe 10. The reception signal output from each ultrasonic transducer is amplified by an amplifier, and the analog reception signal output from the amplifier is converted into a digital signal reception signal by an A / D converter, and the digital reception signal is received. It is output to the signal storage unit 13.

  The reception signal storage unit 13 includes a storage device such as a semiconductor memory, and stores the digital reception signal output from the reception signal processing unit 12.

  The reception control unit 14 reads the reception signal stored in the reception signal storage unit 13 and performs reception focus processing on the read reception signal based on the reception delay time output from the scanning control unit 16. A sound ray signal (hereinafter referred to as an RF signal) in which the focus of the ultrasonic echo is narrowed is generated.

  The B-mode image generation unit 15 performs various signal processing such as amplification, dynamic range, STC, echo enhancement, and the like on the RF signal generated by the reception control unit 14 to obtain tomographic image information about the tissue in the subject. A certain B-mode image (image in which the amplitude of the received signal is represented by the brightness (brightness) of the point) is generated.

  The scanning control unit 16 outputs a transmission delay time and a reception delay time to the transmission control unit 11 and the reception control unit 14, and controls transmission focus processing and reception focus processing.

  The display area determination unit 17 determines a display area and a non-display area of a sound speed map, which will be described later, based on the B mode image generated by the B mode image generation unit 15. Specifically, the display area determination unit 17 of the present embodiment includes a low echo area determination unit 30, a high echo area determination unit 31, and a motion area determination unit 32.

  The low-echo area determination unit 30 is a non-display area that has a small amount of scatterers inside such as blood vessels, gallbladder, benign cysts, and the like included in the subject and the signal intensity of the received signal detected by the ultrasound probe 10 is low. Is determined.

  Here, the local sound speed constituting each pixel of the sound speed map is calculated based on the reception signal detected by the ultrasonic probe 10, but if the signal strength of the reception signal is small, the local sound speed value is reduced. The accuracy may be reduced, and the reliability of the sound speed map may be reduced. Therefore, the low echo region determination unit 30 extracts a region of the received signal having such a low signal intensity based on the B-mode image, and determines the region as a non-display region.

  Specifically, the low echo area determination unit 30 first acquires the B-mode image generated by the B-mode image generation unit 15, and performs speckle leveling by performing blurring processing on the B-mode image. A blurred B-mode image is generated. FIG. 2 shows an example of the B-mode image and the B-mode image after the blurring process.

  Next, the low echo area determination unit 30 compares each pixel value of the blurred B-mode image with a preset threshold value for low echo area determination, and determines a pixel value smaller than the threshold value for low echo area determination. Is determined as a non-display area. Although the blurring process described above may not be performed, an area where pixel values smaller than the threshold are gathered to some extent is extracted from the B-mode image except for isolated points having pixel values smaller than the threshold. Therefore, it is desirable to perform a blurring process. In addition, as long as the process extracts a region in which small pixel values are gathered to some extent as described above, various known processing methods such as a morphological calculation process can be used in addition to the threshold process as described above. .

  The high echo area determination unit 31 is an extremely strong reflector such as a bone included in the subject, and determines an area where the signal intensity of the received signal detected by the ultrasonic probe 10 is high as a non-display area. is there.

  Here, when the signal intensity of the received signal by the ultrasonic probe 10 is large, there is a problem that the measurement range is saturated in the subsequent AD conversion processing. On the other hand, the local sound speed is calculated based on the sharpness of the image generated from the received signal. However, if the received signal is saturated as described above, the sharpness cannot be accurately determined. The local sound speed cannot be acquired, and the reliability of the sound speed map may be reduced.

  Therefore, the high echo area determination unit 31 extracts a reception signal area having a high signal intensity based on the B-mode image, and determines that area as a non-display area.

  Specifically, the high echo area determination unit 31 acquires the B mode image generated by the B mode image generation unit 15, and performs blurring processing on the B mode image in the same manner as the low echo area determination unit 30. By applying this, a blurred B-mode image with speckles smoothed is generated. Next, the high echo area determination unit 31 compares each pixel value of the blurred B-mode image with a preset threshold value for determining the high echo area, and calculates a pixel value greater than the threshold value for determining the high echo area. Is determined as a non-display area. Note that, as with the low echo area determination unit 30, the blurring process described above may not be performed. In addition, as long as it is a process for extracting a region in which large pixel values are gathered to some extent as described above, not only the threshold process described above but also various other known processing methods can be used.

  The motion region determination unit 32 determines a region having a large amount of motion in an image generated from a received signal due to body movement due to a heartbeat or the like, blurring of the ultrasonic probe 10 or the like as a non-display region of the sound velocity map.

  When the amount of motion in the image generated from the received signal is large, motion artifacts occur in the image. On the other hand, as described above, the local sound speed is calculated based on the sharpness of the image generated from the received signal. Therefore, when there is a motion artifact in the image, the sharpness of the image cannot be accurately determined. Therefore, accurate local sound speed cannot be acquired, and the reliability of the sound speed map may be lowered.

  Therefore, the motion region determination unit 32 extracts such a region with a large amount of motion based on the B-mode image, and determines that region as a non-display region.

  Specifically, the motion region determination unit 32 acquires B-mode images of a plurality of frames acquired at different timings, and acquires information indicating the amount of motion based on the amount of change between the frames. The motion region determination unit 32 according to the present embodiment calculates a correlation coefficient between frames as information indicating the amount of motion.

  FIG. 3 shows an example of a correlation coefficient image generated based on B-mode images of two adjacent frames. The B-mode image shown in FIG. 3 is an image of the vicinity of the liver. Although not shown in the B-mode image, a heart exists in the lower right of the B-mode image. The organization is moving. Therefore, in the correlation coefficient image, only the lower right area has a different correlation coefficient from the other areas.

  The motion region determination unit 32 compares each correlation coefficient constituting the correlation coefficient image as shown in FIG. 3 with a preset threshold for motion region determination, and the correlation coefficient is a threshold for motion region determination. The following areas are determined as non-display areas. The information indicating the amount of motion is not limited to the correlation coefficient, and may be a difference between two B-mode images. An area where the difference is equal to or greater than a threshold value may be determined as a non-display area. Further, the process for extracting the motion region is not limited to the above process, and various other known processing methods can be used.

  It should be noted that the range to be displayed in the sound speed map, that is, the range for determining whether or not the sound speed map is a non-display area is set in advance or arbitrarily set by the user. The display area determination unit 17 determines an area that is not determined as a non-display area within the range as a display area.

  In the present embodiment, the display area determination unit 17 includes three types of determination units, ie, a low echo region determination unit 30, a high echo region determination unit 31, and a motion region determination unit 32. It is not necessary to provide all of them, and at least one of the three types of determination units may be provided.

  The sound speed map generation unit 18 acquires the local sound speed based on the determination result in the display area determination unit 17 and the reception signal stored in the reception signal storage unit 13, and generates a sound speed map representing the distribution state of the local sound speed. Is to be generated.

  Specifically, the sound speed map generation unit 18 according to the present embodiment acquires the determination result output from the display area determination unit 17, and regarding pixel positions determined as the display area of the sound speed map, for example, Japanese Patent Application Laid-Open No. 2010-99452. The optimal sound speed of the subject and further the local sound speed are acquired using the technique described in the Japanese Patent Publication. The sound speed map generation unit 18 of the present embodiment does not acquire the optimum sound speed and the local sound speed for the pixel positions for which the display area determination unit 17 has determined the non-display area of the sound speed map.

  More specifically, the sound speed map generation unit 18 first calculates the optimum sound speed only for the pixel position determined as the display area of the sound speed map, based on the received signal stored in the received signal storage unit 13. Here, the optimum sound speed is the sound speed at which the contrast and sharpness of the image are the highest, and does not necessarily match the actual local sound speed at each pixel position. As a method for calculating the optimum sound speed, for example, a method described in JP-A-8-317926 can be employed. That is, an image is generated by performing reception focus processing while changing the assumed sound speed (reception delay time) for the received signal described above, and various images are generated based on the contrast of the image, the spatial frequency in the scan direction, the variance, and the like. A method of obtaining the optimum sound speed from the assumed sound speed can be used. Note that the method for calculating the optimum sound speed is not limited to this, and various other known methods can be used.

  Note that the reception signal used when the optimum sound speed is acquired in the sound speed map generation unit 18 of the present embodiment is different from the reception signal used when generating the B-mode image described above. That is, at a timing different from the transmission / reception of the ultrasonic wave performed to acquire the reception signal used when generating the B-mode image, the ultrasonic wave is transmitted / received for the sound speed acquisition, and the ultrasonic speed acquisition ultrasonic signal is acquired. It is assumed that the optimum sound speed is acquired using a reception signal acquired by transmitting and receiving sound waves. However, the optimum sound speed may be acquired using a reception signal for generating a B-mode image.

  Next, the local sound speed at each pixel position determined as the display area is calculated using the optimum sound speed at each pixel position determined as the display area. Hereinafter, a method for calculating the local sound speed will be described.

  As shown in FIG. 4, the sound velocity map generation unit 18 sets a pixel position for which a local sound velocity is calculated in the subject as a lattice point X, which is shallower than the lattice point X (that is, in the ultrasonic probe 10). A plurality of lattice points arranged at equal intervals in the X direction at close positions are defined as lattice points A1, A2,. It is assumed that at least the local sound speed between the lattice point X and each lattice point A1, A2,.

Based on the optimum sound speed at the lattice point X, the waveform of the virtual received wave W _X when the lattice point X is used as a reflection point is calculated.

Next, an initial value of the assumed sound speed at the lattice point X is set. Then, the assumed sound speed is sequentially changed step by step to calculate a virtual synthesized received wave _WSUM . Specifically, assuming that the local sound velocity at the lattice point X is V, the time until the ultrasonic wave propagated from the lattice point X reaches the lattice points A1, A2,... XA1 / V, XA2 / V,. Become. Here, XA1, XA2,... Are the distances between the lattice points A1, A2,. Since the optimum sound speed at the lattice points A1, A2,... Is known, the received waves from the lattice points A1, A2,. Therefore, the virtual combined received wave _WSUM can be obtained by combining the reflected waves emitted from the lattice points A1, A2,... With the delays XA1 / V, XA2 / V,.

Then, for example, by taking the mutual cross-correlation between the virtual receiving wave W _X assumed resultant received wave W _SUM, the error between the virtual receiving wave W _X and the assumed resultant received wave W _SUM is calculated. As a method of calculating an error between the virtual receiving wave W _X assumed resultant received wave W _SUM is able to adopt various known methods.

Then, for all the assumed sound speeds, the error of the virtual combined with the virtual receiving wave W _X received wave W _SUM is calculated. If strictly apply the principle of Huygens, the waveform of the assumed resultant received wave W _SUM is equal to the waveform of the virtual receiving wave W _X when the local sound speed value at the lattice point X was assumed V. Therefore, the assumed sound speed at which the difference between the virtual received wave W _X and the virtual synthesized received wave W _SUM is minimized is acquired as the local sound speed at the lattice point X. The method for calculating the local sound speed is not limited to the method described above, and other various known methods can be employed. For example, as described in Japanese Patent Application Laid-Open No. 2010-207490, the local sound speed at the pixel position between the two pixel positions is acquired by acquiring the average value of the optimum sound speeds at two pixel positions that are different in the depth direction. You may do it.

  In addition, as described above, when the local sound speed of the pixel position (X2, Y2) different from the pixel position is acquired using the optimum sound speed of the predetermined pixel position (X1, Y1), the pixel position (X1, Y1) Is the pixel position determined as the non-display area of the sound speed map and the optimum sound speed is not acquired, it is determined as the display area near the pixel position (X1, Y1) determined as the non-display area The optimum sound speed at the pixel position (X1, Y1) is obtained by interpolation using the optimum sound speed at the pixel position, and the pixel position (X2, Y2) is obtained using the optimum sound speed at the obtained pixel position (X1, Y1). What is necessary is just to acquire the local sound speed. Various known methods can be used as the interpolation method.

  Then, the sound speed map generation unit 18 generates a sound speed map of the subject based on the local sound speed of each pixel position acquired as described above. The sound velocity map represents the distribution state of the local sound velocity at each pixel position in the subject, and is generated by assigning different colors such as red and blue according to the size of the local sound velocity, for example. It is.

  The display control unit 19 generates a display control signal based on the B-mode image generated by the B-mode image generation unit 15 and the sound speed map generated by the sound speed map generation unit 18 and outputs the display control signal to the monitor 20. To do.

  The monitor 20 displays a B-mode image and a sound speed map of the subject based on the input display control signal.

  Next, the operation of the ultrasonic diagnostic system 1 of the present embodiment will be described with reference to the flowchart shown in FIG.

  First, ultrasonic waves are generated from the ultrasonic transducers of the ultrasonic probe 10 and transmitted to the subject.

  Then, the ultrasonic waves transmitted from each ultrasonic transducer propagate through the subject and are reflected one after another at the discontinuous surface of the acoustic impedance in the middle, and the echo due to this reflection is detected by each ultrasonic transducer. The received signal is output to the received signal processing unit 12.

  Then, in the reception signal processing unit 12, the reception signal output from each ultrasonic transducer is amplified by an amplifier, and the amplified analog signal is converted into a digital signal reception signal by an A / D converter and stored as a reception signal. Stored in the unit 13.

  Next, a reception signal stored in the reception signal storage unit 13 is read by the reception control unit 14, and an RF signal for each frame is acquired by performing reception focus processing on the read reception signal. The

  The RF signal for each frame acquired by the reception control unit 14 is output to the B-mode image generation unit 15. Then, the B mode image generation unit 15 generates a B mode image based on the input RF signal, the display control unit 19 generates a display control signal based on the B mode image, and based on the display control signal. The B mode image is displayed on the monitor 20 (S10).

  Here, when the user observing the B-mode image displayed on the monitor 20 wants to display the sound velocity map, the sound velocity map display mode is set using a predetermined setting input unit (not shown). The setting is input by the user (S12, YES).

  Then, in response to the setting input of the sound velocity map display mode by the user, a B-mode image is acquired by the display area determination unit 17, and the display area determination unit 17 determines each of the objects in the subject based on the acquired B-mode image. It is determined whether the pixel position is a sound speed map display area or a non-display area (S14). In the present embodiment, the determination is performed in each of the low echo region determination unit 30, the high echo region determination unit 31, and the motion region determination unit 32. Then, the determination result in the display area determination unit 17 is output to the sound velocity map generation unit 18.

  On the other hand, at this time, the ultrasonic probe 10 transmits / receives ultrasonic waves for acquiring the sound velocity, and the reception signal acquired by the transmission / reception is stored in the reception signal storage unit 13.

  Then, the sound speed map generation unit 18 reads the reception signal stored in the reception signal storage unit 13 for obtaining the sound speed, and based on the read reception signal and the determination result output from the display area determination unit 17, the sound speed map The local sound speed at the pixel position determined as the map display area is acquired.

  Next, the sound speed map generation unit 18 generates a sound speed map based on the local sound speed distribution acquired for the pixel position determined as the display area. The sound speed map generated in the sound speed map generation unit 18 is output to the display control unit 19, the display control unit 19 generates a display control signal using the input sound speed map, and the monitor 20 receives the input display. Based on the control signal, the sound velocity map is displayed superimposed on the B-mode image (S16).

  Here, an example in which the sound speed map is displayed without determining the display area and the non-display area as described above, and an example in which the sound speed map is displayed by determining the display area and the non-display area are shown.

  FIG. 6 shows an example in which a sound velocity map is displayed on a B-mode image including a gallbladder that is a low echo area without determining a display area and a non-display area. The example which performed the determination of the non-display area | region and displayed the sound speed map is shown. In the sound velocity map in FIG. 7, the gallbladder range is a non-display area.

  FIG. 8 shows an example in which a sound speed map is displayed on the B-mode image near the liver including the motion area shown in FIG. 3 without determining the display area and the non-display area. 9 shows an example in which the sound speed map is displayed by determining the display area and the non-display area. In the sound speed map in FIG. 9, the range where the amount of motion is large is the non-display area.

  According to the ultrasonic diagnostic system 1 of the above-described embodiment, the local sound velocity in the subject is acquired based on the reception signal acquired by transmitting and receiving ultrasonic waves into the subject by the ultrasonic probe 10, and the acquired local sound is obtained. When the sound speed map is generated and displayed based on the sound speed, the non-display area of the sound speed map is determined based on the B mode image, and the sound speed map is not displayed for the non-display area. If the low echo area, the high echo area, or the motion area as described above is determined as a non-display area using the, and the sound speed map is not displayed for these areas, the sound speed map based on the local sound speed with low accuracy is used. Can be prevented from being displayed, a more reliable sound velocity map can be displayed.

  Further, in the ultrasonic diagnostic system 1 of the above embodiment, the local sound speed is not acquired for the non-display area of the sound speed map so that the sound speed map of the non-display area is not displayed. Although the local sound speed is acquired, the sound speed map corresponding to the acquired local sound speed of the non-display area may not be generated, so that the sound speed map of the non-display area may not be displayed. Further, although the sound speed map is generated also for the non-display area, the display control unit 19 does not generate the display control signal based on the sound speed map of the non-display area so that the sound speed map of the non-display area is not displayed. Also good. FIG. 10 generates the sound speed map for the non-display area as described above. However, the display control unit 19 does not generate a display control signal based on the sound speed map of the non-display area, so that the sound speed map of the non-display area is displayed. 2 shows an example of the configuration of the ultrasonic diagnostic system 2 in a case where no symbol is displayed.

  In the high echo area determination unit 31 of the above embodiment, not only a high echo area such as a bone but also an area deeper than the high echo area as shown in FIG. 11 is determined as a non-display area. May be. This is because there is a high possibility that the ultrasonic wave does not reach the area deeper than the high echo area, and the local sound speed calculated based on the received signal in such an area is not likely to be accurate. Because. As a method for setting a region deeper than the high echo region, for example, as shown in FIG. 11, the pixel in the X direction is the same as the high echo region and the position in the Y direction (depth direction) is high. A region of pixels deeper than the echo region may be determined as a non-display region. Further, based on the spread of the ultrasonic wave in the depth direction, a region deeper than the high echo region shown in FIG. 11 may be determined as a non-display region.

  In the ultrasound diagnostic system 1 of the above embodiment, the local sound speed is not acquired for the non-display area of the sound speed map. However, the sound speed map generation unit 18 is not limited to this, and the sound speed map generation unit 18 does not display the sound speed map. For the area, an interpolated sound speed map may be generated based on the local sound speed of the display area near the non-display area, and the display control unit 19 may display the above-described interpolated sound speed map for the non-display area. . By displaying the interpolated sound speed map in this way, it is possible to grasp the information of the area determined as the non-display area.

  Further, the method of generating the interpolated sound speed map is not limited to the above method. For example, the interpolated sound speed map is generated in the frames before and after the received signal frame used when the display area determination unit 17 determines the non-display area. An interpolated sound speed map may be generated based on the local sound speed acquired using the received signal in the area corresponding to the non-display area. It is assumed that the area corresponding to the non-display area in the previous and subsequent frames is an area determined as a display area by the display area determination unit 17.

  In the ultrasonic diagnostic system 1 of the above embodiment, the B-mode image and the sound velocity map are superimposed and displayed simultaneously, but these may be displayed separately, or the sound velocity map. As described above, the local sound speed may be displayed as a numerical value instead of being displayed as a color image as described above.

  In addition, the transmission delay time and the reception delay time based on the local sound speed acquired by the sound speed map generation unit 18 are calculated, and the transmission focus is performed based on the transmission delay time, and the reception signal is received using the reception delay time. An RF signal may be generated by performing focus processing, and a B-mode image based on the RF signal may be displayed on the monitor 20.

DESCRIPTION OF SYMBOLS 1, 2 Ultrasonic diagnostic system 10 Ultrasonic probe 11 Transmission control part 12 Reception signal processing part 13 Reception signal memory | storage part 14 Reception control part 15 B mode image generation part 16 Scan control part 17 Display area determination part 18 Sonic map generation part 19 Display control unit 30 Low echo region determination unit 31 High echo region determination unit 32 Motion region determination unit

Claims (10)

A B-mode image generating unit that generates a B-mode image based on a reception signal acquired by transmitting and receiving ultrasonic waves into the subject by the ultrasonic probe;
A sound speed map generating unit for acquiring a local sound speed in the subject based on a reception signal acquired by the ultrasonic probe, and generating a sound speed map based on the acquired local sound speed;
A display controller for displaying the sound velocity map generated by the sound velocity map generator;
A display area determination unit that determines a non-display area of the sound velocity map based on the B mode image generated by the B mode image generation unit;
The ultrasonic diagnostic apparatus, wherein the display control unit does not display the sound velocity map for the non-display area.   The display area determination unit is configured to determine, as the non-display area, an area having a pixel value smaller than a threshold value for low echo area determination among pixel values constituting the B-mode image. Item 2. The ultrasonic diagnostic apparatus according to Item 1.   The display area determination unit is configured to determine, as the non-display area, an area having a pixel value larger than a threshold value for determining a high echo area among pixel values constituting the B-mode image. Item 3. The ultrasonic diagnostic apparatus according to Item 1 or 2.   The ultrasonic diagnosis according to claim 2 or 3, wherein the display area determination unit determines the non-display area based on an image obtained by performing a blurring process on the B-mode image. apparatus.   The display area determination unit acquires information indicating the amount of motion of the subject in the B-mode image based on B-mode images of different frames, and the non-display based on the information indicating the acquired amount of motion. The ultrasonic diagnostic apparatus according to claim 1, wherein the display area is determined.   The ultrasonic diagnostic apparatus according to claim 1, wherein the sound velocity map generation unit does not acquire the local sound velocity or the sound velocity map for the non-display area.   Based on the received signal transmitted and received for sound speed acquisition by the ultrasonic probe at a timing different from the received signal acquired to generate the B-mode image by the sound speed map generating unit, The ultrasonic diagnostic apparatus according to claim 1, wherein a local sound velocity is acquired.   The sound velocity map generation unit acquires a local sound velocity in the subject based on the received signal acquired to generate the B-mode image. The ultrasonic diagnostic apparatus according to 1.   The ultrasonic diagnostic apparatus according to claim 1, wherein the display control unit displays the sound velocity map and the B-mode image so as to overlap each other. A B-mode image is generated based on a reception signal acquired by transmission / reception of ultrasonic waves into the subject by the ultrasonic probe, and a local sound velocity in the subject is determined based on the reception signal acquired by the ultrasonic probe. In a sound speed display method for acquiring, generating a sound speed map based on the acquired local sound speed, and displaying the generated sound speed map,
Based on the B-mode image, a non-display area of the sound velocity map is determined,
The sound speed display method, wherein the sound speed map is not displayed for the non-display area.