JP2013244195A - Ultrasonic signal processing apparatus and ultrasonic signal processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic signal processing apparatus capable of easily analyzing a sonic velocity value within a subject after the completion of ultrasonic scanning, and an ultrasonic signal processing method.SOLUTION: When setting of a threshold of a reliability index is received by an operating unit 14 (step S32), an arithmetic processing unit 28 calculates an optimum sonic velocity value in a region lower than the threshold by using an optimum sonic velocity value equal to/higher than the threshold set for the reliability index (step S34). A display operation unit 34 creates a sonic velocity map indicating a sonic velocity distribution within a subject OBJ by using the optimum sonic velocity value for each region, which is calculated in step S34 (step S36), and displays it on a display unit 16 (step S38).

Description

  The present invention relates to an ultrasonic signal processing apparatus and an ultrasonic signal processing method, and more particularly to an ultrasonic signal processing apparatus and an ultrasonic signal processing method for receiving an ultrasonic echo reflected by a subject and recording an ultrasonic signal.

  In Patent Document 1, after measuring the sound speed in the subject N times (N is an integer of 2 or more) based on the beam focusing degree in the reception focus processing, an average value and reliability of the sound speed measured N times are calculated. Display on the display unit (paragraphs [0055] to [0056], [0063] to [0064]).

  Patent Document 2 discloses that a profile representing a change in an evaluation value for a phasing addition result when a plurality of trial delay conditions corresponding to a plurality of sound speeds is changed is generated for each reference region. (Paragraphs [0012], [0037] and [0047]).

JP 2009-078124 A JP 2010-119481 A

  The element data before beam forming is useful for correcting the sound speed in the subject and creating a sound speed map, but the amount of data is enormous compared to the line data after beam forming. For this reason, in order to record element data, a huge memory capacity is required.

For example, in an ultrasonic signal processing apparatus that records 64 channels, sampling frequency is 40 MHz, and the amplitude of received data is 2 bytes, when taking data of 240 lines and 5 cm depth, the data of the line data after beam forming The amount is
2 (Byte) × 0.05 (m) × 2 / 1,540 (m / s) × 40 (MHz) × 240 (Line) = 1.23 (MByte)
It becomes. On the other hand, the amount of element data before beamforming is
1.23 (MByte) x 64 (ch) = 78.72 (MByte)
It becomes.

For example, when storing 10-point transmission focus element data to create a sound velocity map, the amount of element data is:
78.72 (MByte) x 10 (points) = 787.2 (MByte)
It becomes. As described above, a memory capacity of about 1 (Giga Byte) is required every time element data for sound velocity map is stored.

For example, when storing a sonic moving image of 100 frames, the data amount of element data corresponding to the sonic moving image is:
787.2 (MByte) x 100 (frame) = 78.72 (GByte)
It becomes.

  Since it is difficult to store such a large amount of element data, when performing ultrasonic signal processing (for example, calculation and display of sound speed correction, optimum sound speed value and local sound speed value) using element data In this case, the used element data used for the calculation is deleted as needed while performing the processing. However, if the element data is erased, the image (eg, B-mode image) is frozen after the ultrasonic scan is completed, and then the analysis is resumed by returning to the moving image frame before the frozen frame, or the inspection is completed. It was not possible to perform analysis later.

  Further, even if all element data obtained by ultrasonic scanning are stored, there is a problem that it takes time to analyze such a large amount of element data.

  Patent Documents 1 and 2 each describe the reliability of the average value of sound velocity and the evaluation value of the phase matching addition result. These values are used for reanalysis of the sound velocity value of a subject that has been ultrasonically imaged in the past. It wasn't something to do.

  The present invention has been made in view of such circumstances, and an ultrasonic signal processing apparatus and an ultrasonic signal processing method capable of easily analyzing a sound velocity value in a subject after completion of an ultrasonic scan. The purpose is to provide.

  In order to solve the above-described problem, an ultrasonic signal processing device according to a first aspect of the present invention transmits an ultrasonic wave to a subject, receives an ultrasonic wave reflected by the subject, and receives an ultrasonic detection signal. An ultrasonic probe including a plurality of elements that output a sound speed, a sound speed calculating means for calculating a sound speed for each region in the subject based on the ultrasonic detection signal, and reliability of the sound speed based on the ultrasonic detection signal. A reliability index calculation means for calculating the reliability index to be shown, a storage means for storing the sound speed and the reliability index of the sound speed in association with each other, a threshold setting means for receiving the setting of the reliability index threshold, and a threshold value greater than or equal to the set threshold Sound speed distribution calculating means for calculating the sound speed distribution in the subject using the sound speed of the reliability index.

  The ultrasonic signal processing apparatus according to the second aspect of the present invention is the ultrasonic signal processing apparatus according to the first aspect, wherein the sound speed calculation means has the highest at least one of contrast and sharpness of the ultrasonic image in the region of interest in the subject. The optimal sound speed is calculated.

  In the ultrasonic signal processing device according to the third aspect of the present invention, in the second aspect, the reliability index calculating means calculates the local sound speed for each region in the subject calculated based on the optimum sound speed. It is comprised as follows.

  The ultrasonic signal processing apparatus according to the fourth aspect of the present invention is the ultrasonic signal processing apparatus according to any one of the first to third aspects, wherein the sound speed distribution calculating means uses the sound speed of the reliability index equal to or greater than a set threshold value. Is calculated by interpolating the sound speed in a region where is less than the threshold.

  The ultrasonic signal processing apparatus according to the fifth aspect of the present invention is the ultrasonic signal processing apparatus according to any one of the first to third aspects, wherein the sound speed distribution calculating means uses only the sound speed of the reliability index equal to or higher than the set threshold value. The sound velocity image showing the distribution of sound velocity in the inside is created.

  An ultrasonic signal processing method according to a sixth aspect of the present invention includes a plurality of elements that transmit ultrasonic waves to a subject, receive ultrasonic waves reflected by the subject, and output ultrasonic detection signals. Based on the ultrasonic detection signal detected by the ultrasonic probe, a sound speed calculation step for calculating the sound speed for each region in the subject, and a reliability index indicating the reliability of the sound speed based on the ultrasonic detection signal are calculated. A reliability index calculation step, a storage step for associating and storing the sound speed and the sound speed reliability index, a threshold setting step for accepting the setting of the reliability index threshold value, and the sound speed of the reliability index equal to or higher than the set threshold value. And a sound speed distribution calculating step for calculating a sound speed distribution in the subject.

  In the ultrasonic signal processing method according to the seventh aspect of the present invention, at least one of the contrast and sharpness of the ultrasonic image in the region of interest in the subject is the highest in the sound speed calculation step of the sixth aspect. The optimum sound speed is calculated.

  In the ultrasonic signal processing method according to the eighth aspect of the present invention, the local sound speed for each region in the subject calculated based on the optimum sound speed is calculated in the reliability index calculation step of the seventh aspect. It is configured.

  In the ultrasonic signal processing method according to the ninth aspect of the present invention, in the sound velocity distribution calculating steps of the sixth to eighth aspects, the reliability index is calculated using the sound speed of the reliability index equal to or greater than a set threshold value. The sound velocity in the region below the threshold value is calculated by interpolation.

  In the ultrasonic signal processing method according to the tenth aspect of the present invention, in the sound velocity distribution calculating steps of the sixth to eighth aspects, only the sound velocity of the reliability index equal to or higher than a set threshold value is used. The sound velocity image showing the distribution of the sound velocity at is created.

  According to the present invention, by storing the sound speed obtained based on the ultrasonic detection signal and its reliability index in association with each other, the sound speed distribution using the reliability index even after the end of the ultrasonic scan. The image (sound speed map) showing the sound speed distribution based on the recalculation and the recalculation result can be created.

1 is a block diagram showing an ultrasonic signal processing apparatus according to a first embodiment of the present invention. The figure which shows typically the example of the file structure for storing the optimum sound velocity value and its reliability index The figure which shows typically another example of the file structure for storing the optimal sound velocity value and its reliability index The flowchart which shows the process of the ultrasonic signal processing method which concerns on the 1st Embodiment of this invention. The flowchart which shows 1st Embodiment of the analysis process using the optimal sound speed value preserve | saved in the memory for preservation | save, and its reliability parameter | index. Ultrasonic image example Example of superimposing a sound velocity map on an ultrasound image (B-mode image) The flowchart which shows the process of the ultrasonic signal processing method which concerns on the 2nd Embodiment of this invention. The figure which shows typically the calculation process of the local sound speed value which concerns on this embodiment. The flowchart which shows the analysis process using the reliability parameter | index of the local sound speed value calculated | required based on the optimal sound speed value preserve | saved in the memory for preservation | save, and the optimal sound speed value

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an ultrasonic signal processing apparatus and an ultrasonic signal processing method according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a block diagram showing an ultrasonic signal processing apparatus according to the first embodiment of the present invention.

  The ultrasonic signal processing apparatus 10 shown in FIG. 1 transmits an ultrasonic beam from the ultrasonic probe 18 to the subject OBJ, receives and records an ultrasonic echo reflected by the subject OBJ, and generates ultrasonic waves. This is an apparatus for creating and displaying an ultrasonic image from an echo detection signal (ultrasonic detection signal).

  The control unit (control processor) 12 controls each block of the ultrasonic signal processing apparatus 10 in accordance with an operation input from the operation unit 14. The control unit 12 includes a storage area for storing a control program for controlling each block of the ultrasonic signal processing apparatus 10.

  The operation unit 14 is an input device that receives an operation input from an operator. The operation unit 14 includes a keyboard that receives input of character information (for example, patient information), and a pointing device (for example, a trackball, a mouse, a touch panel, etc.) that receives input for specifying an area on the screen of the display unit 16. Yes. Further, the operation unit 14 includes a display mode switching button for switching the display mode, a moving image playback button for instructing moving image playback, and analysis / measurement of an ultrasonic image (for example, strain analysis (hardness diagnosis) of a tissue part) It includes an analysis / measurement button for instructing blood flow measurement, tissue movement measurement, or IMT (Intima-Media Thickness measurement).

  The display unit 16 is, for example, a CRT (Cathode Ray Tube) display or a liquid crystal display. The display unit 16 displays ultrasonic images (moving images and still images) and various setting screens.

  The ultrasonic probe 18 is a probe used in contact with the subject OBJ, and includes a plurality of ultrasonic transducers (elements) 20 constituting a one-dimensional or two-dimensional transducer array. The element 20 transmits an ultrasonic beam to the subject OBJ based on a drive signal applied from the transmission / reception control unit 24 via the transmission / reception unit 22. Each element 20 receives an ultrasonic echo reflected by the subject OBJ and outputs a detection signal (element data).

  The element 20 includes, for example, a vibrator configured 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 an electric signal is sent to the electrodes of the vibrator and a voltage is applied, 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 transmission / reception unit 22 as an ultrasonic detection signal.

  As the ultrasonic transducer, a plurality of types of elements having different ultrasonic conversion methods can be used. For example, as an element for transmitting an ultrasonic wave, an ultrasonic transducer using the above-described piezoelectric body, and as an element for receiving an ultrasonic wave, a light detection type ultrasonic transducer that converts an ultrasonic signal into an optical signal and detects it. (For example, a Fabry-Perot resonator or a fiber Bragg grating) may be used.

  When the ultrasonic probe 18 is brought into contact with the subject OBJ and ultrasonic diagnosis is started by an instruction input from the operation unit 14, the control unit 12 sends control signals to the transmission / reception unit 22 and the transmission / reception control unit 24. Then, the transmission of the ultrasonic beam to the subject OBJ and the reception of the ultrasonic echo from the subject OBJ are started. The control unit 12 sets the transmission direction of the ultrasonic beam and the reception direction of the ultrasonic echo for each element 20.

  Further, the control unit 12 selects a transmission delay pattern according to the transmission direction of the ultrasonic beam, and selects a reception delay pattern according to the reception direction of the ultrasonic echo. 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 plurality of elements 20. The reception delay pattern is pattern data of a delay time given to a detection signal in order to extract an ultrasonic echo from a desired direction by ultrasonic waves received by a plurality of elements 20. The transmission delay pattern and the reception delay pattern are stored in the control unit 12 in advance. The control unit 12 selects a transmission delay pattern and a reception delay pattern from those stored in advance, and sends a control signal to the transmission / reception unit 22 via the transmission / reception control unit 24 according to the selected transmission delay pattern and reception delay pattern. Output and control transmission / reception of ultrasonic waves.

  The transmission / reception control unit 24 generates a drive signal according to the control signal from the control unit 12 and applies the drive signal to the element 20 via the transmission / reception unit 22. At this time, the transmission / reception control unit 24 delays the drive signal applied to each element 20 based on the transmission delay pattern selected by the control unit 12 (transmission focus). Here, the transmission / reception control unit 24 adjusts (delays) the timing of applying the drive signal to each element 20 so that the ultrasonic waves transmitted from the plurality of elements 20 form an ultrasonic beam. Note that the timing of applying the drive signal may be adjusted so that the ultrasonic waves transmitted from the plurality of elements 20 reach the entire imaging region of the subject OBJ.

  The transmission / reception unit 22 receives and amplifies the ultrasonic detection signal output from each element 20. Since the distance between each element 20 and the ultrasonic wave reflection source in the subject OBJ is different, the time for the reflected wave to reach each element 20 is different. The transmission / reception unit 22 includes a delay circuit, and changes the arrival time difference (delay time) of the reflected wave in accordance with the sound speed (assumed sound speed) or the distribution of sound speeds set based on the reception delay pattern selected by the control unit 12. Each detection signal is delayed by a corresponding amount.

  When the display mode is the live mode, the transmission / reception unit 22 performs reception focus processing (beam forming) by matching and adding the detection signals given delay times. For example, when there is another ultrasonic reflection source at a position different from the ultrasonic reflection source in the subject OBJ, the arrival time of the ultrasonic detection signal from the other ultrasonic reflection source is different. For this reason, the phase of the ultrasonic detection signal from another ultrasonic wave reflection source cancels out by adding in the addition circuit of the transmission / reception unit 22. As a result, the reception signal from the ultrasonic reflection source becomes the largest, and the ultrasonic reflection source is focused. By the reception focus processing, a sound ray signal (hereinafter referred to as an RF signal) in which the focus of the ultrasonic echo is narrowed is formed.

  In the present embodiment, the detection signal subjected to the reception focus process in the transmission / reception unit 22 is an RF signal, but the detection signal not subjected to the reception focus process may be an RF signal. In this case, the reception focus process is performed digitally in the arithmetic processing unit 28.

  The analog RF signal output from the transmission / reception unit 22 is converted 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 is input to the element data memory 26 and temporarily stored.

  The element data memory 26 sequentially stores the RF data. Further, the element data memory 26 stores information related to the frame rate input from the control unit 12 (for example, parameters indicating the reflection position depth, scanning line density, and field width) in association with the RF data. .

  The arithmetic processing unit (processor for calculation) 28 transfers the element data temporarily stored in the element data memory 26 to the primary storage memory 32 and primarily stores it. Here, as the element data memory 26 and the primary storage memory 32, a volatile memory can be used. The element data memory 26 and the primary storage memory 32 may be shared by a single memory. The arithmetic processing unit 28 performs envelope detection processing on the RF data after correcting attenuation by distance according to the depth of the ultrasonic reflection position by STC (Sensitivity Time gain Control).

  Further, the arithmetic processing unit 28 calculates an optimum sound speed value and a local sound speed value for each region in the subject OBJ. In addition, the arithmetic processing unit 28 calculates a reliability index indicating the reliability of the optimum sound speed value calculated for each region in the subject OBJ. The optimum sound speed value and its reliability index are temporarily stored in the calculation result holding unit 30.

  Here, the optimum sound speed value is obtained as, for example, the sound speed value at which at least one of the contrast and the sharpness of the image in the region of interest (ROI) in the subject OBJ is the highest in the B-mode image. That is, the optimum sound speed value is a virtual sound speed value obtained by performing reception focus corresponding to the average sound speed value in the area from the ultrasonic probe 18 to the target area.

  The local sound speed value is a sound speed value in the region of interest, and is obtained by a method described in, for example, Japanese Patent Application Laid-Open No. 2010-099452 based on the optimum sound speed value.

  The display calculation unit 34 generates B-mode image data (image data representing the amplitude of the ultrasonic echo by the brightness (luminance) of the point) from the RF data output from the calculation processing unit 28. Since the B-mode image data is obtained by a scanning method different from a normal television signal scanning method, the B-mode image data is obtained from normal image data (for example, a television signal scanning method (NTSC (National Television System Committee) image data) (raster conversion). The image data is subjected to various necessary image processing (for example, gradation processing) by the display calculation unit 34, converted into an analog image signal, and output to the display unit 16. Thereby, an ultrasonic image (moving image) photographed by the ultrasonic probe 18 is displayed on the display unit 16.

  When the operation unit 14 receives an instruction input for moving image reproduction, the control unit 12 switches the operation mode of the ultrasonic signal processing apparatus 10 to the moving image reproduction mode. In the moving image playback mode, the arithmetic processing unit 28 reads RF data from the primary storage memory 32 in accordance with a command from the control unit 12, performs predetermined processing (processing similar to that in the live mode), and converts it into image data. After that, it is converted into an analog image signal and output to the display unit 16. Accordingly, an ultrasonic image (moving image or still image) based on the RF data stored in the primary storage memory 32 is displayed on the display unit 16.

  When a freeze instruction is input from the operation unit 14 while an ultrasonic image (moving image) is displayed in the live mode or the moving image playback mode, the ultrasonic image displayed when the freeze button is pressed is displayed on the display unit 16. Still image is displayed. Thereby, the operator can display and observe a still image of a region of interest (ROI).

  The display calculation unit 34 creates an image (sound speed map) indicating the distribution of sound speed in the subject OBJ in response to an operation input from the operation unit 14 in the live mode or the moving image playback mode, and outputs the image to the display unit 16. To do. The sound speed map is created based on the optimum sound speed value temporarily stored in the calculation result holding unit 30 and its reliability index. The display mode of the sound speed map can be selected by the operator by setting the display mode using the operation unit 14. As the display mode, for example, an ultrasonic image (tomographic image, B-mode image) and a sound velocity map are displayed side by side on the screen of the display unit 16, and a mode in which the ultrasonic image and the sound velocity map are superimposed and displayed (for example, a sound velocity). There is a display in which color coding or luminance is changed according to the value, a display in which dots having the same sound speed value are connected by a line), a mode in which the sound speed value is displayed as a numerical value on the B mode image, and the like. When the sound speed map is displayed, a scale indicating the correspondence between the sound speed value and the contrast or hue in the sound speed map may be displayed near the sound speed map.

  The storage memory 36 stores the optimum sound velocity value and its reliability index in association with each other.

  2 and 3 are diagrams schematically showing an example of a file structure for storing the optimum sound speed value and its reliability index.

  In the example shown in FIG. 2, the optimum sound speed value and its reliability index are included in attached information (for example, header information) in a file for storing a B-mode image (hereinafter referred to as an inspected data storage file F1). ) Is stored.

  In the example shown in FIG. 3, the optimum sound speed value and its reliability index are stored in a dedicated inspected data storage file F2. In addition, in the inspected data storage file F2, storage location information (link information) for the B-mode image is stored in the attached information. The inspected data storage file F2 may be stored in association with the B-mode image file, or may store a luminance value for each region where the optimum sound speed value is calculated.

  The file structure for storing the optimum sound speed value and its reliability index is not limited to the examples of FIGS. Further, in the examined data storage files F1 and F2, for example, information on the subject OBJ (for example, identification information of the subject OBJ (patient), storage date and time of element data, etc.), information on transmission / reception conditions of ultrasound ( For example, the transmission / reception mode, frequency, transmission / reception rate, transmission / reception address, transmission focus position coordinates corresponding to each element data, depth information, and the like) may be stored as attached information.

[Ultrasonic signal processing]
FIG. 4 is a flowchart showing processing of the ultrasonic signal processing method according to the first embodiment of the present invention.

  First, an ultrasonic beam is transmitted from the ultrasonic probe 18 into the subject OBJ, and an ultrasonic echo reflected from the subject OBJ is received by the ultrasonic probe 18. Thereby, an ultrasonic detection signal is acquired (step S10). This ultrasonic detection signal is temporarily stored in the element data memory 26.

  Next, the arithmetic processing unit 28 calculates an optimum sound velocity value for each region (point) for the ultrasonically scanned region (step S12). The optimum sound speed value is calculated as, for example, a sound speed value at which at least one of the contrast and sharpness of the image in the region of interest (ROI) in the subject OBJ is the highest in the B-mode image.

  Next, the arithmetic processing unit 28 calculates a reliability index of the optimum sound speed value for each region (step S14). Here, the reliability index is, for example, an index obtained by normalizing the amplitude value of the RF signal obtained by beam forming the ultrasonic detection signal using the optimum sound speed value, and the distortion degree of the waveform of the element data is normalized. It is an indicator.

  The display calculation unit 34 creates a sound speed map indicating the sound speed distribution in the subject OBJ using the optimum sound speed value for each region calculated in step S12 (step S16), and displays the sound speed map on the display unit 16 (step S16). S18).

  In addition, the arithmetic processing unit 28 associates the optimum sound speed value for each region calculated in steps S12 to S14 and the reliability index thereof, and stores them in the storage memory 36 (step S20).

[Analysis process using reliability index]
FIG. 5 is a flowchart showing an analysis process using the optimum sound velocity value stored in the storage memory 36 and its reliability index.

  When information related to the subject OBJ (for example, identification information of the subject OBJ (patient), storage date / time of element data, etc.) is input from the operation unit 14, the control unit 12 performs an examination corresponding to the information related to the subject OBJ. The saved data storage file is read from the storage memory 36, and the optimum sound speed value and its reliability index are read (step S30). The optimum sound speed value and its reliability index are displayed on the display unit 16 together with the B-mode image.

  When the setting of the threshold value of the reliability index is accepted by the operation unit 14 (step S32), the arithmetic processing unit 28 uses the optimal sound speed value that is equal to or higher than the threshold value for which the reliability index is set, to obtain the optimal sound speed value in the region below the threshold value. Is calculated (step S34).

  The display calculation unit 34 creates a sound speed map indicating the sound speed distribution in the subject OBJ using the optimum sound speed value for each region calculated in step S34 (step S36), and displays the sound speed map on the display unit 16 (step S36). S38).

  FIG. 6 shows an example of an ultrasonic image. In the example shown in FIG. 6, the optimum sound speed value and its reliability index in the region R1 are 1450 m / s and 0.8, respectively, and the optimal sound speed value and its reliability index in the region R2 are 1800 m / s and 0.2, respectively. The optimum sound velocity value and its reliability index in R3 are 1550 m / s and 0.9, respectively.

  When the threshold value set in step S32 is 0.5, the optimum sound speed value in the region R2 is the optimum sound speed value in the regions R1, R3, etc. around the region R2, and the region R2, the surrounding regions R1, R3, etc. It is obtained by interpolation based on the distance. Then, the optimum sound speed value 1800 m / s in the region R2 stored in the inspected data storage file is not used for creating the sound speed map in step S36.

  FIG. 7 shows an example in which the sound velocity map IMG2 is superimposed and displayed on the ultrasonic image (B-mode image) IMG1. In FIG. 7, the X axis indicates the scanning direction (the arrangement direction of the elements 20), and the Z axis indicates the depth direction in the subject OBJ. In addition, the code | symbol B1 in a figure is a scale which shows the correspondence of the sound speed value and color in the sound speed map IMG2.

  In the sound speed map IMG2 shown in FIG. 7, the region R10 in which the reliability index of the optimal sound speed value is equal to or greater than the threshold set in step S32 is colored according to the optimal sound speed value. On the other hand, the region R12 in which the reliability index of the optimum sound speed value is less than the threshold is not given a color corresponding to the optimum sound speed value.

  According to the present embodiment, the optimum sound speed value and its reliability index are stored in association with each other, so that the optimum sound speed value can be recalculated and re-calculated using the reliability index even after the ultrasonic scan is completed. It is possible to create a sound speed map of optimum sound speed values based on the calculation result.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 8 is a flowchart showing processing of the ultrasonic signal processing method according to the second embodiment of the present invention.

  First, an ultrasonic beam is transmitted from the ultrasonic probe 18 into the subject OBJ, and an ultrasonic echo reflected from the subject OBJ is received by the ultrasonic probe 18. Thereby, an ultrasonic detection signal is acquired (step S50). This ultrasonic detection signal is temporarily stored in the element data memory 26.

Next, the arithmetic processing unit 28 calculates an optimum sound velocity value for each region (point) for the ultrasonically scanned region (step S52). Then, the arithmetic processing unit 28 calculates a local sound velocity value for each region of interest (point of _interest ) X _ROI in the subject OBJ based on the optimum sound velocity value for each region (step S54).

FIG. 9 is a diagram schematically illustrating a local sound speed value calculation process according to the present embodiment. 9A and 9B, the X-axis indicates the scanning direction (the arrangement direction of the elements 20), and the Z-axis indicates the depth direction in the subject OBJ. 9 attention point in (b) _{X ROI} and the point A1, A2, ..., and sonic Va in the region A between the An, the points A1, A2, ..., in the region B between An and the ultrasonic probe 18 It is assumed that the sound speed Vb is constant. In FIG. 9B, the boundary S1 between the region A and the region B is linear, but it may be curved or irregular.

The received wave W _x shown in FIG. 9A is a received wave received when the point of interest X _ROI is used as a reflection point based on the optimum sound speed value at the point of interest X _ROI (local sound speed value calculation target). is there.

The synthesized received wave W _SUM shown in FIG. 9B is a received wave (W _A1 , W _A2 ,..., Respectively) in which the ultrasonic wave propagated from the point of _interest X _ROI is received through the points A1, A2,. W _An ) is a combined received wave obtained by combining. If the distances from the point of _interest X _ROI to the points A1, A2,..., An are X _ROI A1, X _ROI A2, ..., X _ROI An, respectively, the ultrasonic waves from the point of _interest X _ROI are points A1, A2,. The time to reach An is X _ROI A1 / Va, X _ROI A2 / Va,..., X _ROI An / Va, respectively. Further, the received waveform when the ultrasonic waves emitted from the points A1, A2,..., An reach the element surface S2 of the ultrasonic probe is calculated based on the optimum sound velocity value at each point. The synthesized received wave _WSUM synthesizes the reflected waves (ultrasonic echoes) emitted from the points A1, A2,..., An with the delays X _ROI A1 / Va, X _ROI A2 / Va, ..., X _ROI An / Va, respectively. Can be obtained.

According to Huygens' principle, the received wave W _x and the synthesized received wave W _SUM coincide. For this reason, the sound speed value Va at which the difference between the received wave W _x and the combined received wave W _SUM is minimized is set as the local sound speed value at the point of interest X _ROI (region A). The difference between the received wave W _x and the combined received wave W _SUM is obtained by, for example, a method of obtaining a cross-correlation between the received waveform or the reception time of each element 20 of the received wave W _x and the combined received wave W _SUM .

In the example shown in FIGS. 9A and 9B, the region from the ultrasonic probe 18 to the point of interest X _ROI is divided into two layers in the Z direction, and the local sound velocity value is obtained. However, the present invention is not limited to this. For example, it may be divided into three or more layers in the Z direction, and the local sound velocity value may be obtained in order from the layer on the ultrasonic probe 18 side. Further, the local sound speed value may be obtained by assuming a plurality of regions having different optimum sound speed values in the X direction.

Next, the arithmetic processing unit 28 calculates the reliability index of the local sound speed value for each target point _{X ROI} (step S56). Here, the reliability index of the local sound speed value is, for example, the above-described one or a plurality of regions (points A1,..., An, X _ROI (that is, points used for _obtaining the local sound speed value at the point of interest X _ROI )). The average value of the amplitude value of the RF signal obtained by beam forming the ultrasonic detection signal obtained when obtaining the optimum sound speed value in () is obtained, and is normalized using the local sound speed value at the point of _{interest XROI} . Can be calculated. Further, it is an index that standardizes the average value of the degree of distortion of the waveform of the element data obtained when obtaining the optimum sound velocity value in the one or a plurality of regions (points A1,..., An, X _ROI ).

  The display calculation unit 34 creates a sound speed map indicating the distribution of sound speed in the subject OBJ using the local sound speed value for each region calculated in step S12 (step S58), and displays it on the display unit 16 (step S58). S60).

  Further, the arithmetic processing unit 28 associates the optimum sound speed value for each region calculated in steps S52 to S14, the local sound speed value, and the reliability index of the local sound speed value in association with each other, and stores them in the storage memory 36 (step S62).

  FIG. 10 is a flowchart showing an analysis process using the optimum sound speed value stored in the storage memory 36 and the reliability index of the local sound speed value obtained based on the optimum sound speed value.

  When information related to the subject OBJ (for example, identification information of the subject OBJ (patient), storage date / time of element data, etc.) is input from the operation unit 14, the control unit 12 performs an examination corresponding to the information related to the subject OBJ. The saved data storage file is read from the storage memory 36, and the optimum sound speed value and the reliability index of the local sound speed value obtained based on the optimum sound speed value are read (step S70). The optimum sound speed value and its reliability index are displayed on the display unit 16 together with the B-mode image.

  When setting of the threshold value of the reliability index is accepted by the operation unit 14 (step S72), the arithmetic processing unit 28 uses the local sound speed value that is equal to or higher than the threshold value for which the reliability index is set, and the local sound speed value in the region below the threshold value. Is calculated (step S74).

  The display calculation unit 34 creates a sound velocity map indicating the distribution of sound velocity in the subject OBJ using the local sound velocity value calculated for each region in step S74 (step S76), and displays it on the display unit 16 (step S76). S78).

  Note that local sound velocity values having a reliability index less than the threshold value may not be displayed on the sound velocity map.

  According to the present embodiment, by storing the optimum sound speed value, the local sound speed value calculated using the optimum sound speed value, and the reliability index thereof in association with each other, even after the end of the ultrasound scan, It is possible to recalculate the local sound speed value using the reliability index, create a sound speed map of the local sound speed value based on the recalculation result, and the like.

  In the above embodiment, the example in which the ultrasonic transducer (element 20) is arranged one-dimensionally has been described, but the present invention is not limited to this. For example, in each of the above embodiments, the ultrasonic transducer is arranged in a two-dimensional manner, or the ultrasonic transducer is not a flat surface but an arbitrary curved surface (for example, a convex surface that is convex with respect to the object OBJ). ) Can also be applied.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic signal processing apparatus, 12 ... Control part (control processor), 14 ... Operation part, 16 ... Display part, 18 ... Ultrasonic probe (probe), 20 ... Ultrasonic transducer (element), 22 ... Transmission / reception unit, 24 ... Transmission / reception control unit, 26 ... Element data memory, 28 ... Calculation processing unit (processor for calculation), 30 ... Calculation result holding unit, 32 ... Memory for primary storage, 34 ... Display calculation unit, 36 ... Storage memory

Claims (10)

An ultrasonic probe including a plurality of elements that transmit ultrasonic waves to the subject, receive ultrasonic waves reflected by the subject, and output ultrasonic detection signals;
A sound speed calculating means for calculating a sound speed for each region in the subject based on the ultrasonic detection signal;
A reliability index calculating means for calculating a reliability index indicating the reliability of the sound speed based on the ultrasonic detection signal;
Storage means for associating and storing the sound speed and a reliability index of the sound speed;
Threshold setting means for receiving setting of a threshold value of the reliability index;
A sound speed distribution calculating means for calculating a sound speed distribution in the subject using the sound speed of the reliability index equal to or higher than the set threshold;
An ultrasonic signal processing apparatus.   The ultrasonic signal processing apparatus according to claim 1, wherein the sound speed calculation unit calculates an optimum sound speed at which at least one of contrast and sharpness of an ultrasonic image in a region of interest in a subject is highest.   The ultrasonic signal processing apparatus according to claim 2, wherein the reliability index calculating unit calculates a local sound speed for each region in the subject calculated based on the optimum sound speed.   4. The sound velocity distribution calculating means interpolates and calculates a sound velocity in a region where the reliability index is less than the threshold value using a sound velocity of the reliability index equal to or greater than the set threshold value. 5. The ultrasonic signal processing apparatus according to item.   4. The sound speed distribution calculating unit creates a sound speed image indicating a sound speed distribution in the subject using only the sound speed of the reliability index equal to or higher than the set threshold value. 5. The ultrasonic signal processing apparatus described. Based on an ultrasonic detection signal detected by an ultrasonic probe including a plurality of elements that transmit ultrasonic waves to the subject and receive ultrasonic waves reflected by the subject and output ultrasonic detection signals A sound speed calculating step for calculating the sound speed for each region in the subject,
A reliability index calculation step of calculating a reliability index indicating the reliability of the sound speed based on the ultrasonic detection signal;
A storage step of associating and storing the sound speed and a reliability index of the sound speed;
A threshold value setting step for receiving a setting of the threshold value of the reliability index;
A sound speed distribution calculating step of calculating a sound speed distribution in the subject using the sound speed of the reliability index equal to or higher than the set threshold;
An ultrasonic signal processing method comprising:   The ultrasonic signal processing method according to claim 6, wherein in the sound speed calculation step, an optimal sound speed at which at least one of contrast and sharpness of an ultrasonic image in a region of interest in a subject is highest is calculated.   The ultrasonic signal processing method according to claim 7, wherein, in the reliability index calculating step, a local sound speed for each region in the subject calculated based on the optimum sound speed is calculated.   9. The sound velocity distribution calculating step, wherein the sound velocity of the reliability index equal to or higher than the set threshold is used to interpolate and calculate the sound velocity in a region where the reliability index is less than the threshold. The ultrasonic signal processing method according to item.   9. The sound velocity image showing the sound velocity distribution in the subject is created using only the sound velocity of the reliability index equal to or higher than the set threshold value in the sound velocity distribution calculating step. The ultrasonic signal processing method as described.