JP5681755B2 - Ultrasonic diagnostic apparatus and method for operating the same - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus that captures and displays an ultrasonic image of a diagnostic part of a subject using ultrasonic waves and an operating method thereof, and more particularly to an ultrasonic diagnostic apparatus that corrects the environmental sound speed of a diagnostic part and the method thereof It relates to the operation method.

  2. Description of the Related Art Conventionally, an ultrasound diagnostic apparatus that captures and displays an ultrasound image of a diagnostic region of a subject using ultrasound, a probe, an ultrasound transmission / reception unit, an image processing circuit, a digital scan converter (DSC), and an image It was configured with a display device.

  In such a conventional ultrasonic diagnostic apparatus, the ultrasonic sound velocity value set for the entire apparatus is fixed to a certain value.

  Since the sound speed varies depending on the tissue such as the fat layer and the muscle layer in the living body, the ultrasonic sound speed in the subject (hereinafter referred to as environmental sound speed) is not uniform. Moreover, since the thickness of the fat layer and the muscle layer differs between a fat subject and a thin subject, there are individual differences in the environmental sound speed for each subject.

  As described above, in the conventional ultrasonic diagnostic apparatus, the value of the ultrasonic sound speed (hereinafter referred to as the set sound speed) set for the entire apparatus is fixed to a certain value, so that the environmental sound speed in the subject is the set sound speed. The more the time is deviated, the more the arrival time of the reflected wave is shifted from the delay time set in the ultrasonic transmission / reception unit, the focus is deteriorated, and the image quality of the obtained ultrasonic image is deteriorated.

  Therefore, for example, Patent Literature 1 proposes an ultrasonic diagnostic apparatus that can correct the set sound speed set in the apparatus and improve the focus.

  The ultrasonic diagnostic apparatus disclosed in Patent Document 1 is focused on the ultrasonic sound velocity value input by the operation input device as a set sound velocity of the entire apparatus by a focus calculation circuit provided between the control circuit unit and the ultrasonic transmission / reception unit. The focus data storage circuit provided at the next stage of the focus calculation circuit writes the focus data calculated by the focus calculation circuit and reads the focus data and sends it to the ultrasonic transmission / reception unit. It is configured to operate so as to correct the set sound speed by capturing an ultrasonic image using the focus data read from the storage circuit.

  The ultrasonic diagnostic apparatus of Patent Document 1 includes a spatial frequency analysis circuit that inputs an output signal from an ultrasonic transmission / reception unit and analyzes a spatial frequency with respect to the amplitude of the ultrasonic reception signal, and the focus data storage circuit While taking an ultrasonic image using the focus data read out from, obtain the ultrasonic sound velocity value when the high frequency component or dispersion of the spatial frequency is the maximum for the amplitude of the ultrasonic reception signal in the spatial frequency analysis circuit, It is disclosed that the set sound speed is corrected by the ultrasonic sound speed value by feeding back the spatial frequency analysis signal to a control circuit unit.

JP-A-8-317926

  However, in the ultrasonic diagnostic apparatus disclosed in Patent Document 1, for example, while taking an ultrasonic image using the focus data read from the focus data storage circuit, the spatial frequency analysis circuit determines the amplitude of the ultrasonic reception signal with the spatial frequency. The calculation of the high frequency component or dispersion is performed.

  For this reason, in order to correct the preset sound speed, it is necessary to use an ultrasonic image that has been photographed and constructed. That is, since the spatial frequency of the entire ultrasonic image is analyzed, the set sound speed is corrected to the environmental sound speed of the entire ultrasonic image, and the set sound speed can be set, for example, for each pixel level or line image level constituting the ultrasonic image. It is not possible to appropriately correct the environmental sound speed for each time, and it is impossible to construct a highly accurate ultrasonic image.

  The present invention has been made in view of such circumstances, and determines an environmental sound speed appropriately for each pixel level or line image level constituting an ultrasonic image, and constructs a highly accurate ultrasonic image. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of performing the same and an operating method thereof.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a plurality of ultrasonic waves that transmit ultrasonic waves to a subject and receive ultrasonic waves reflected by the subject and output ultrasonic detection signals. An ultrasonic probe including a transducer, a transmission focus means for transmitting and focusing ultrasonic waves to at least two points in the subject, and reception data obtained by each transmission focus are acquired from the ultrasonic probe. There is provided an ultrasonic diagnostic apparatus comprising acquisition means for performing determination, and determination means for obtaining environmental sound velocities at respective points from received data.

  According to the above configuration, it is possible to appropriately determine the environmental sound speed for each pixel level or line image level constituting the ultrasonic image, and to construct a highly accurate ultrasonic image.

  According to a second aspect of the present invention, in the first aspect, the determining means includes a set sound speed specifying means for specifying a plurality of set sound speeds for receiving focus on the reception data obtained by each transmission focus, and a plurality of set sound speeds. A focus index calculation unit that calculates a focus index for each reception focus, and an environmental sound speed calculation unit that obtains an ambient sound speed for each point based on a focus index for each of a plurality of set sound speeds.

  According to a third aspect of the present invention, in the first aspect or the second aspect, an ultrasonic image constructing unit that constructs an ultrasonic image of each point is further provided.

  According to a fourth aspect of the present invention, a transmission focus step for transmitting and focusing ultrasonic waves to at least two or more points from an ultrasonic probe including a plurality of ultrasonic transducers and reception data obtained by each transmission focus are acquired. There is provided an operating method of an ultrasonic diagnostic apparatus comprising: an acquiring step for determining, and a determining step for determining an ambient sound velocity at each point from received data.

  As described above, according to the present invention, it is possible to appropriately determine the environmental sound speed for each pixel level or line image level constituting the ultrasonic image, and to construct a highly accurate ultrasonic image. There is.

1 is a block diagram showing an ultrasonic diagnostic apparatus according to a first embodiment of the present invention. The block diagram which shows the structure of the data analysis part of FIG. The flowchart which shows the flow of a process of the data analysis part of FIG. First diagram for explaining the processing of FIG. 2nd figure for demonstrating the process of FIG. 3rd figure for demonstrating the process of FIG. 4th figure for demonstrating the process of FIG. The flowchart which shows the flow of a process of the data analysis part which concerns on the 2nd Embodiment of this invention. 1st figure for demonstrating the process of FIG. 2nd figure for demonstrating the process of FIG. Explanatory drawing which shows a mode that the value is suppressed in the peripheral part of a line image by multiplying a coefficient.

  Hereinafter, an ultrasonic diagnostic apparatus and an operation method thereof according to the present invention will be described in detail for each embodiment with reference to the accompanying drawings.

First embodiment:
FIG. 1 is a block diagram showing an ultrasonic diagnostic apparatus according to the first embodiment of the present invention. The ultrasonic diagnostic apparatus 10 shown in FIG. 1 transmits an ultrasonic beam from an ultrasonic probe 300 to a subject OBJ. It is an apparatus that transmits and receives an ultrasonic beam reflected by the subject OBJ (hereinafter referred to as ultrasonic echo), and creates and displays an ultrasonic image from the detection signal of the ultrasonic echo.

  A CPU (Central Processing Unit) 100 controls each block of the ultrasonic diagnostic apparatus 10 according to an operation input from the operation input unit 200.

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

  The storage unit 102 is a storage device that stores a control program for executing control of each block of the ultrasonic diagnostic apparatus 10 in the CPU 100, and is, for example, a hard disk or a semiconductor memory.

  The display unit 104 is, for example, a CRT (Cathode Ray Tube) display or a liquid crystal display, and displays ultrasonic images (moving images and still images) and various setting screens.

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

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

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

  Next, details of each block of the ultrasonic diagnostic apparatus 10 will be described by taking an ultrasonic diagnostic process in the live mode as an example. The live mode is a mode for displaying, analyzing, and measuring an ultrasonic image (moving image) obtained by transmitting and receiving ultrasonic waves by bringing the ultrasonic probe 300 into contact with the subject OBJ.

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

Furthermore, CPU 100 is you select a transmission delay pattern according to the transmission direction of the ultrasonic beam. Here, the transmission delay pattern is pattern data of a delay time given to the drive signal in order to form an ultrasonic beam in a desired direction by ultrasonic waves transmitted from the plural ultrasonic transducers 302. The transmission delay pattern is stored in advance in the storage unit 102. CPU100 selects a transmission delay pattern from among those stored in the storage unit 102, performs the transmission delay pattern selected thus, the output to transmission and reception control of ultrasound control signal to the transceiver 400.

  The transmission circuit 402 generates a drive signal in accordance with a control signal from the CPU 100 and applies the drive signal to the ultrasonic transducer 302. At this time, the transmission circuit 402 delays the drive signal applied to each ultrasonic transducer 302 based on the transmission delay pattern selected by the CPU 100. Here, the transmission circuit 402 adjusts (delays) the timing at which the drive signal is applied to each ultrasonic transducer 302 so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers 302 form an ultrasonic beam. Perform focus. Note that the timing at which the drive signal is applied may be adjusted so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers 302 reach the entire imaging region of the subject OBJ.

  The receiving circuit 404 receives and amplifies the ultrasonic detection signal output from each ultrasonic transducer 302 and outputs the amplified signal to the A / D converter 406 as an analog RF signal.

  The A / D converter 406 converts the analog RF signal output from the receiving circuit 404 into a digital RF signal (hereinafter referred to as RF data). Here, the RF data includes phase information of the received wave (carrier wave). The RF data output from the A / D converter 406 is input to the signal processing unit 502, the cine memory 602, and the data analysis unit 700, respectively.

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

  As described above, since the distances between the ultrasonic transducers 302 and the ultrasonic reflection sources in the subject OBJ are different, the time for the reflected wave to reach the ultrasonic transducers 302 is different.

  The signal processing unit 502 corresponds to a difference in arrival time (delay time) of the reflected wave according to a sound speed (hereinafter, set sound speed) set based on an environmental sound speed from the data analysis unit 700 described later or a sound speed distribution. , Delay each RF data. Next, the signal processing unit 502 digitally performs reception focus processing by matching and adding RF data to which a delay time is given, and generates RF image data.

When there is another ultrasonic reflection source at a position different from the ultrasonic reflection source _XROI , since the arrival time of the ultrasonic detection signal from the other ultrasonic reflection source is different, the signal processing unit 502 adds them. Thus, the phases of the ultrasonic detection signals from other ultrasonic reflection sources cancel each other. As a result, the received signal from the ultrasonic reflection source X _ROI becomes the largest and the focus is achieved. By the reception focus processing, RF image data in which the focus of the ultrasonic echo is narrowed is formed.

  In addition, the signal processing unit 502 performs envelope detection processing on the RF image data after correcting attenuation by distance according to the depth of the ultrasonic reflection position by STC (Sensitivity Time gain Control). , B-mode image data (image data representing the amplitude of the ultrasonic echo by the brightness (luminance) of the point) is generated.

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

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

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

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

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

  When the measurement button on the console 202 is pressed, analysis / measurement designated by an operation input from the operator is performed. When the measurement button is pressed in each operation mode, the data analysis unit 700 acquires RF data before image processing is performed from the A / D converter 406 or the cine memory 602, and uses the RF data. Analysis and measurement specified by the operator (for example, strain analysis of tissue part (hardness diagnosis), blood flow measurement, tissue part motion measurement, or IMT (Intima-Media Thickness) measurement) I do.

  In addition, the data analysis unit 700 calculates the environmental sound speed of the region of interest, and outputs the calculated environmental sound speed to the signal processing unit 502. Details will be described later.

  The analysis / measurement result by the data analysis unit 700 is output to the DSC 504 of the image signal generation unit 500. The DSC 504 inserts the analysis / measurement result by the data analysis unit 700 into the image data of the ultrasonic image and outputs the result to the display unit 104. Thereby, the ultrasonic image and the analysis / measurement result are displayed on the display unit 104.

  FIG. 2 is a block diagram showing the configuration of the data analysis unit of FIG. As shown in FIG. 2, the data analysis unit 700 includes a focused area setting unit 701, a transmission focus control unit 702, a set sound speed designation unit 703, a focus index calculation unit 704, and an environmental sound speed determination unit 705.

  The attention area setting section 701 sets the attention area on the ultrasonic image displayed on the display section 104 based on the input from the operation input section 200 by the operator via the CPU 100, and constitutes the attention area setting means. .

  The transmission focus control unit 702 gives a transmission focus instruction to the CPU 100 so that the transmission circuit 402 performs transmission focus on the set region of interest, and constitutes transmission focus instruction means.

  Based on the control of the CPU 100, the set sound speed designation unit 703 designates a set sound speed for executing the reception focus on the RF data (ultrasound detection signal), and constitutes a set sound speed designation unit.

  The focus index calculation unit 704 reads RF data from the cine memory 602, performs reception focus on the RF data for each of a plurality of set sound speeds specified by the set sound speed specification unit 703, and calculates a focus index of the RF data. The focus index calculation means is configured.

  The environmental sound speed determination unit 705 determines the environmental sound speed of the region of interest based on a focus index for each of a plurality of set sound speeds, and constitutes an environmental sound speed determination unit.

  The operation of the present embodiment configured as described above will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart showing a processing flow of the data analysis unit of FIG. 4 to 7 are diagrams for explaining the processing of FIG.

  As shown in FIG. 3, the data analysis unit 700 displays a region of interest on the ultrasonic image displayed on the display unit 104 by the region-of-interest setting unit 701 based on an input from the operation input unit 200 by the operator via the CPU 100. Set (step S10).

  Next, the data analysis unit 700 sets the start sound speed Vst and the end sound speed Vend of the set sound speed V in the set sound speed designating unit 703 (step S20), and sets the start sound speed Vst to the set sound speed V (step S30).

  As shown in FIG. 4, for RF data from point reflection, RF image data whose intensity and sharpness can be analyzed when reception focus is performed can be acquired (see FIG. 4). For innumerable scattering points, the peak value and the spatial frequency in the azimuth direction collapse due to interference (see FIG. 5), and RF image data that can analyze intensity and sharpness when receiving focus is acquired. It becomes difficult.

  Therefore, the data analysis unit 700 forms a pseudo point reflection (see FIG. 6) by applying transmission focus to innumerable scattering points in the speckle region, and performs reception focus on the acquired reception element signal. The ambient sound velocity is also obtained in the speckle region by a method similar to point reflection for analyzing the intensity and sharpness.

  That is, the data analysis unit 700 issues a transmission focus instruction to the CPU 100 so that the transmission circuit 402 performs transmission focus on the region of interest set by the transmission focus control unit 702, and sets the transmission focus position to pseudo point reflection. (Step S40).

  Then, the data analysis unit 700 reads the RF data from the cine memory 602 by the focus index calculation unit 704, receives and focuses the RF data for each of the plurality of set sound speeds designated by the set sound speed designation unit 703, and outputs the RF image data. The focus index is calculated (step S50).

  Here, in the case of the point reflection RF image data in FIG. 4, as shown in FIG. 7, the peak value and the spatial frequency in the azimuth direction tend to change depending on the set sound speed, but the transmission focus is applied as shown in FIG. In this case, the trend shown in FIG. 7 is also observed in the case of the RF image data when the pseudo point reflection is formed. Therefore, the data analysis unit 700 uses the focus index calculation unit 704 to calculate the integral value, the square integral value, The peak value, contrast, half width, frequency spectrum integration, frequency spectrum integral value normalized by the maximum value or DC component, square integral value, autocorrelation value, etc. are calculated as focus indices (in the case of FIG. 7, the set sound velocity = The focus index at the time of Amp1490 is maximized).

  Next, the data analysis unit 700 determines whether or not the set sound speed V has reached the end sound speed Vend in the set sound speed designating unit 703 (step S60). If the set sound speed V is less than the end sound speed Vend, the predetermined sound speed amount ΔV is determined. The set sound speed V is added (step 70), and the process returns to step S40. If it is determined that the set sound speed V has reached the end sound speed Vend, the process proceeds to step S80.

  In step S80, the data analysis unit 700 determines the environmental sound speed of the region of interest based on the focus index for each of the plurality of set sound speeds in the environmental sound speed determination unit 705, and outputs the determined environmental sound speed to the signal processing unit 502. Then, the process ends (in the case of FIG. 7, the set sound speed of the highest focus index = Amp 1490 is the environmental sound speed).

  As described above, in this embodiment, the transmission focus is applied to the innumerable scattering points in the speckle region to produce a pseudo point reflection, and a focus index for each of a plurality of set sound speeds is generated. Therefore, it is possible to appropriately determine the environmental sound speed of the region of interest including the speckle region based on the point reflection level, and to construct a highly accurate ultrasonic image. .

Second embodiment:
Since the second embodiment has the same configuration as the first embodiment and the processing in the data analysis unit is different from the first embodiment, only the differences will be described.

  FIG. 8 is a flowchart showing the flow of processing of the data analysis unit according to the second embodiment of the present invention. 9 and 10 are diagrams for explaining the processing of FIG.

  As shown in FIG. 8, the data analysis unit 700 sets the start number Nst and the end number Nend of the parameter N in the region-of-interest setting unit 701 after the process of step S10 (step S11). Then, after the process of step S30, the data analysis unit 700 sets the start number Nst for the parameter N (step S31).

  In the present embodiment, as shown in FIG. 9, the data analysis unit 700 causes the attention area setting unit 701 to pay attention when the operator designates the attention area with respect to RF image data acquired by, for example, a line-by-line method. An area is set (step S10), reception focus assuming point reflection is performed on the receiving element data obtained in each line of the target area, a focus index is calculated, and the total of each line and depth is obtained. As a result, the environmental sound speed is obtained with high accuracy even in the speckle region.

  Therefore, the data analysis unit 700 instructs the CPU 100 to perform a transmission focus on the region of interest set by the transmission focus control unit 702 so that the transmission circuit 402 executes the transmission focus, and sets the transmission focus position as a pseudo point reflection. For example, multi-stage focusing is executed (step S40a).

  Then, the data analysis unit 700 reads out the RF data of the line N (parameter N) from the cine memory 602 by the focus index calculation unit 704, and converts the RF data of the line N into a plurality of set sound speeds designated by the set sound speed designation unit 703. On the other hand, reception focus assuming point reflection is executed, RF image data of line N is created, and a focus index is calculated (step S50a). This RF image data is hereinafter referred to as a line image.

  Next, the data analysis unit 700 determines whether or not the parameter N has reached the end number Nend in the region-of-interest setting unit 701 (step S51). If the parameter N is less than the end number Nend, the parameter N is incremented (step S51). 52) Returning to step S40a, if it is determined that the parameter N has reached the end number Nend, the process proceeds to step S53.

  Next, the data analysis unit 700 calculates the focus index Σ (= line Nst focus index + line Nst + 1 focus index +...) From the sum of the focus indices of the line N (parameter N) at the set speed V (step S53). .

  After the processing in steps S60 and S70, the data analysis unit 700 determines the environmental sound speed of the region of interest based on the focus index Σ for each of the plurality of set sound speeds in the environmental sound speed determination unit 705, and performs signal processing on the determined environmental sound speed. It outputs to the part 502 and complete | finishes a process (step S80).

  By the processing of FIG. 8 of the present embodiment, as shown in FIG. 10, the data analysis unit 700 performs line-by-line analysis based on RF image data based on line-by-line RF data in which the region of interest at the set speed V is multi-stage focused. The focus index is calculated, and the focus index Σ is calculated from the sum of the focus indexes for each line. Then, the data analysis unit 700 determines the environmental sound speed of the region of interest based on the focus index Σ for each set speed V.

  That is, in the present embodiment, from the reception element data obtained in each line of line-by-line, including not only the transmission focus position but also the surroundings, the reception focus is performed assuming point reflection, the image is constructed, The focus index is calculated and the sum of each line is taken to obtain the final focus index Σ to determine the environmental sound speed of the region of interest.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, smoothness of the focus index calculated from the RF image data (line image) constructed assuming point reflection for each line constituting the region of interest. The environmental sound speed of the region of interest can be determined with higher accuracy by the effect of the conversion.

  According to the present embodiment, the environmental sound speed of the region of interest can be accurately determined by the conventional method of obtaining from the final line-by-line image. That is, in the case of the point reflection shown in FIG. 4, the RF image data uses only the RF image data at the transmission focus position because the peak value at the transmission focus position corresponding to each line position varies depending on the set sound speed as shown in FIG. However, in the case of the pseudo point reflection shown in FIG. 6, the RF image data shows the tendency of FIG. Since the profile slightly changes due to interference, it is possible to accurately grasp the tendency by using it including the periphery of the transmission focus position, and this embodiment determines the environmental sound speed more accurately than the conventional method. be able to.

  The attention area in each embodiment is set by the operator. However, the present invention is not limited to this. For example, the attention area is automatically moved on the RF image data shown in FIG. The environmental sound speed can be determined for each region of interest.

  In step S50 or S50a in each of the above embodiments, the data analysis unit 700 reads RF data from the cine memory 602 by the focus index calculation unit 704. However, the present invention is not limited to this, and the focus index calculation unit 704 The RF data may be subjected to reception focus for each of a plurality of set sound speeds designated by the RF data set sound speed designation unit 703 from the / D converter 406, and a focus index of the RF image data may be calculated.

Third embodiment:
In the third embodiment, in order to obtain the environmental sound speed from the line image, only the frequency spectrum shape is used without including the image intensity.

  That is, by obtaining the environmental sound velocity from only the spatial frequency spectrum shape in the azimuth direction for the above line image (RF image data created by executing reception focus assuming point reflection) without including the image intensity, Speckle environmental sound speed can be obtained with high accuracy by the method of obtaining from the final image of the line-by-line.

  This will be described in detail below.

  In general, point reflection (PSF) of an ultrasonic image has characteristics of both “image intensity” and “frequency spectrum shape” depending on a set sound speed, as already described with reference to FIG. Therefore, it is possible to obtain the environmental sound speed by using the characteristic that it depends on the set sound speed.

  However, when the object of ultrasonic diagnosis is speckle, that is, when there is interference of ambient scattering, an error occurs in the set sound speed dependence characteristics for both the image intensity and the frequency spectrum.

  In addition, as a result of diligent research by the inventor of the present application, it has been found that which of the image intensity and the frequency spectrum hardly causes an error due to interference depends on the characteristics of the PSF.

  More specifically, the PSF when only the reception focus is performed is less susceptible to interference in the frequency spectrum shape than the image intensity, and conversely in the case of the PSF resulting from the transmission focus. It was found that image intensity is less susceptible to interference than shape.

  Therefore, when using a conventional line-by-line final image up to the transmission focus, an environmental sound speed can be accurately obtained by using an index based only on the image intensity that is not easily affected by interference, for example, “sum of squares”. Can be requested.

  Here, the line-by-line image is an image obtained by connecting the middle lines of the line images corresponding to each transmission.

  Therefore, this index can be regarded as “an index obtained by smoothing the sum of squares of the middle line of a line image for a plurality of lines”.

  Here, in consideration of the fact that the scattering point position in the line image does not necessarily coincide with the middle line (transmission focus center) and that the image peak position deviates from the middle line due to interference, “the middle line of the line image Rather than using the “square sum”, it is possible to correctly evaluate the image intensity by using the “line image contrast”, and as a result, the environmental sound speed can be obtained with high accuracy.

  Since the line image is an image in which only reception focus is performed with respect to pseudo point reflection, the PSF in that case may be less susceptible to interference in the frequency spectrum shape than in the image intensity. Understand, therefore, an index based only on the frequency spectrum shape rather than “contrast” based on both image intensity and frequency spectrum shape, for example, “sum of squares normalized by average value” or “frequency spectrum normalized by DC component” It can be seen that the environmental sound speed can be obtained with higher accuracy by using “integration”, “autocorrelation value”, “half-value width of frequency spectrum”, and the like.

  From the above, when using a line-by-line image that reaches the normal transmission focus, the sound speed of the environment can be accurately obtained by using an index based only on the image intensity, such as “sum of squares”. However, a frequency such as “the sum of squares normalized by the average value” for a line image in which only the reception focus is applied to the pseudo point reflection formed by multiplying the transmission focus by one point. It can be said that the environmental sound speed can be obtained more accurately by using the index based only on the spectrum shape.

  “The sum of squares normalized by the average value” is the same as the “integration of the square of the frequency spectrum normalized by the DC component” from the Parseval theorem, and can be obtained by simple calculation and is practical. .

  When the environmental sound speed is obtained by “the sum of squares normalized by the average value”, a line image obtained by performing only the reception focus on the pseudo point reflection formed by multiplying the transmission focus by one point as described above. By multiplying the peripheral part by a coefficient that reduces the value, the noise-dominated and unreliable image edge can be suppressed, and discontinuity can be reduced. The accuracy of sound speed can be improved.

  This is shown in FIG. In FIG. 11, the left image is a line image, and the middle graph shows the image edge suppression coefficient. The graph of the image edge suppression coefficient is shown by taking the azimuth direction pixel position on the horizontal axis and the coefficient on the vertical axis. The coefficient value at the center of the graph is 1, and the coefficient values on both sides are smaller than 1. By multiplying this value, the value at the edge of the image is suppressed. The image on the right side is obtained by multiplying the line image on the left side in FIG. 11 by the middle image edge suppression coefficient. As shown in the right image, it can be seen that the value at the edge of the image is suppressed by multiplying the coefficient.

  Even when other indices are used, suppressing the peripheral portion of the line image is effective in improving the accuracy of the environmental sound speed.

  As described above, according to the third embodiment, in order to obtain the environmental sound speed from the line image, only the frequency spectrum shape is used without including the image intensity, and particularly the reliability of the line image. In addition to suppressing the low image edge portion and multiplying the image edge portion by a coefficient such that the value becomes smaller so as to reduce discontinuity, it is possible to further improve the accuracy of the required environmental sound speed.

  When determining the environmental sound speed of the region of interest, if the region of interest is not uniform speckles and a clear structure is included in the region of interest, as in the third embodiment described above, In the method of obtaining the environmental sound speed using only the frequency spectrum shape using the line image, the accuracy may be deteriorated. That is, even if the transmission focus is applied to the middle line of the line image, an error may occur if the reflection from the peripheral line is stronger.

  In this way, when a clear structure is included in the region of interest, the environmental sound speed is determined using the final line-by-line image as in the past, without using the line image. Better. Since the line-by-line image is an image with transmission focus, it is possible to accurately obtain the environmental sound speed using an index based on the image intensity, for example, “sum of squares”.

  Therefore, as a fourth embodiment, a method for determining whether or not to determine the environmental sound speed by using an index after determining whether or not a structure is included in the region of interest. explain.

Fourth embodiment:
As a method for determining whether or not a structure is included in the region of interest, that is, whether or not the speckle is uniform, for example, the following three methods are conceivable.

  First, a method of determining whether the ratio of the number of pixels equal to or greater than a predetermined multiple of the average value to the total number of pixels in the region of interest is equal to or greater than a predetermined threshold.

  Next, as a second method, a determination is made based on whether or not there is a pixel whose primary differential value in the depth direction before or after logarithmic compression is equal to or greater than a predetermined threshold.

  A third method is to determine whether or not the degree of deviation from the Rayleigh distribution is greater than or equal to a predetermined threshold.

  Here, as a determination method based on the degree of deviation from the Rayleigh distribution, for example, the following method can be considered.

  That is, the relationship between the standard deviation σ of the Rayleigh distribution and the average value u is given by the following equation.

σ = sqrt (4 / π−1) * u
Here, sqrt () represents the square root in ().

  At this time, if the region of interest includes a structure, the value of σ increases, so the ratio between the virtual standard deviation σ0 obtained from the average value of the region of interest and the actual standard deviation σ is a predetermined threshold value. The determination can be made based on whether or not the above.

  By one of the methods shown above, it is first determined whether or not a structure is included in the region of interest, that is, whether it is uniform speckle or non-uniform.

  Next, as a result, for example, when it is determined that the structure is not included in the region of interest, the line image is used and the frequency is not included, as in the third embodiment described above. The ambient sound velocity is obtained by an index based only on the spectrum shape.

  On the other hand, when it is determined that a structure is included in the region of interest, the ambient sound speed is obtained using the final line-by-line image as in the conventional case. At this time, the ambient sound speed is determined by using at least one of an index based on only the intensity information of the line, for example, an integral value, a square integral value, a peak value, and a frequency spectrum integral value, without including the periphery of the middle line. To ask.

  As described above, according to the fourth embodiment, it is determined whether a structure is included in the region of interest, that is, whether it is a uniform speckle region, and an index corresponding to the result is used. In particular, if there is no structure in the region of interest, the line image is used, and the ambient sound speed is obtained using an index based only on the frequency spectrum shape without including the image intensity. When the target area contains structures, the normal sound (final image of line-by-line) is used to obtain the environmental sound speed without using the line image. Can be improved.

  The ultrasonic diagnostic apparatus and the operation method thereof according to the present invention have been described in detail above, but the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasound diagnostic apparatus, 100 ... CPU, 102 ... Storage part, 104 ... Display part, 200 ... Operation part, 202 ... Console, 204 ... Pointing device, 300 ... Ultrasonic probe, 302 ... Ultrasonic transducer ( Element), 400 ... transmission / reception unit, 402 ... transmission circuit, 404 ... reception circuit, 406 ... A / D converter, 500 ... image signal generation unit, 502 ... signal processing unit, 504 ... DSC, 506 ... image processing unit, 508 ... Image memory, 510 ... D / A converter, 600 ... Playback unit, 602 ... Cine memory, 604 ... Cine memory playback unit, 700 ... Data analysis unit

Claims (4)

An ultrasonic probe including a plurality of ultrasonic transducers that transmit ultrasonic waves to the subject, receive ultrasonic waves reflected by the subject, and output ultrasonic detection signals;
Transmission focus means for transmitting and focusing the ultrasonic waves from the ultrasonic probe to each of at least two points in the subject; and
Obtaining means for obtaining received data obtained by each transmission focus;
A determining means for determining respective ambient sound velocity at each point from the received data the for each point,
An ultrasonic diagnostic apparatus comprising: The determining means includes
Set sound speed designating means for designating a plurality of set sound speeds for receiving focus with respect to the reception data obtained by each transmission focus;
Focus index calculating means for calculating a focus index by receiving focus for each of the set sound speeds;
Environmental sound speed calculating means for determining the environmental sound speed for each point based on the focus index for each of the plurality of set sound speeds;
The ultrasonic diagnostic apparatus according to claim 1, comprising:   The ultrasound diagnostic apparatus according to claim 1, further comprising an ultrasound image construction unit that constructs an ultrasound image of each point based on the ambient sound velocity. A transmission focus step of transmitting and focusing ultrasonic waves to each of at least two points from an ultrasonic probe including a plurality of ultrasonic transducers;
An acquisition step of acquiring reception data obtained by each transmission focus;
A determining step of determining respective ambient sound velocity at each point from the received data the for each point,
A method for operating an ultrasonic diagnostic apparatus comprising: