Patent Publication Number: US-11020088-B2

Title: Program, method and device for ultrasonic diagnosis

Description:
TECHNICAL FIELD 
     This disclosure relates to a program, method and device for ultrasonic diagnosis, which diagnose a state of a detected part that is a detection target in a detected body. 
     BACKGROUND ART 
     Conventionally, an ultrasonic diagnosis in which analytical data is generated based on reflection echoes caused by ultrasonic waves transmitted to a detected part, so as to analyze a state of the detected part that is a detection target in a detected body. For example, Patent Document 1 discloses a device which inserts, into a body joint, an endoscope having an ultrasonic wave transmitting and receiving body at a tip end thereof, and calculates a thickness of a cartilage that is a detected part, based on reflection echoes caused by pulse signals transmitted from the ultrasonic wave transmitting and receiving body. 
     REFERENCE DOCUMENT OF CONVENTIONAL ART 
     Patent Document 
     Patent Document 1: JP2002-345821A 
     DESCRIPTION OF THE DISCLOSURE 
     Problems to be Solved by the Disclosure 
     Meanwhile, in a case of analyzing a state of the detected part in a percutaneous manner by using the device described in Patent Document 1, the ultrasonic wave attenuates at a soft tissue. Since the attenuation level of the ultrasonic wave at the soft tissue varies depending on the soft tissue, there is a case where it is difficult to accurately evaluate the state of the cartilage. 
     This disclosure is made in view of the above situations and aims to accurately grasp a state of a detected part even in a case of analyzing the state of the detected part in a percutaneous manner. 
     SUMMARY OF THE DISCLOSURE 
     (1) In order to solve the subject described above, according to one aspect of the present disclosure, an ultrasonic diagnosing device for diagnosing a state of a detected part that is a detection target in a detected body is provided. The ultrasonic diagnosing device includes a level assigning module configured to assign an echo intensity to one of a plurality of levels of echo intensities, the echo intensity calculated based on one of echo signals that are caused by ultrasonic signals transmitted from an ultrasonic probe into the detected body, and being an intensity of each of the echo signals that are samples respectively corresponding to positions in an area-of-interest of the detected body, the area-of-interest defined in a depth direction of the detected body and a direction intersecting the depth direction, and a characteristic amount calculating module configured to calculate, by targeting two or more of the samples having the echo intensities assigned to the plurality of levels by the level assigning module, one or more characteristic amounts indicating a characteristic of the area-of-interest, based on a combination of the echo intensities of the two or more of the samples, the two or more of the samples having a given positional relationship with each other. 
     (2) The ultrasonic diagnosing device may further include an image generating module configured to generate an echo level image configured with a plurality of pixels having luminance levels corresponding to the echo intensities assigned to the plurality of levels by the level assigning module the plurality of pixels associated with the respective positions of the area-of-interest, respectively. 
     (3) The ultrasonic diagnosing device may further include an upper and lower limit value setting module configured to set an upper limit echo intensity and a lower limit echo intensity, the upper limit echo intensity indicating a highest value among the echo intensities assigned to the plurality of levels, the lower limit echo intensity indicating a lowest value among the echo intensities assigned to the plurality of levels. 
     (4) The area-of-interest may be designed as an area including echo signals from a front surface of the detected part. 
     (5) The ultrasonic diagnosing device may further include a co-occurrence matrix generating module configured to generate a co-occurrence matrix based on the echo intensities of the samples respectively corresponding to the positions of the area-of-interest, the echo intensities assigned to the plurality of levels by the level assigning module. The characteristic amount calculating module may calculate the one or more characteristic amounts based on the co-occurrence matrix generated by the co-occurrence matrix generating module. 
     (6) Moreover, the characteristic amount calculating module may calculate a correlation as one of the one or more characteristic amounts. 
     (7) Moreover, the co-occurrence matrix generating module may calculate as the co-occurrence matrix, a first co-occurrence matrix targeting pairs of samples corresponding to the area-of-interest, each of the pairs of the samples consisting of a pair of samples having a positional relationship in which the samples are separated by a given distance in the direction intersecting the depth direction. The characteristic amount calculating module may calculate the correlation based on the first co-occurrence matrix. 
     (8) The characteristic amount calculating module may calculate a contrast as one of the one or more characteristic amounts. 
     (9) Moreover, the co-occurrence matrix generating module may calculate as the co-occurrence matrix, a second co-occurrence matrix targeting pairs of samples corresponding to the area-of-interest, each of the pairs of the samples consisting of a pair of samples having a positional relationship in which the samples are separated by a given distance in the depth direction. The characteristic amount calculating module may calculate the contrast based on the second co-occurrence matrix. 
     (10) The ultrasonic diagnosing device may further include a front surface position detecting module configured to detect a position of a front surface of the detected part in the depth direction based on the echo signals, and an area-of-interest designing module configured to design the area-of-interest based on the position of the front surface of the detected part detected by the front surface position detecting module. 
     (11) Moreover, the level assigning module may include an upper and lower limit value setting module configured to set an upper limit echo intensity and a lower limit echo intensity, the upper limit echo intensity indicating a highest value among the echo intensities assigned to the plurality of levels, the lower limit echo intensity indicating a lowest value among the echo intensities assigned to the plurality of levels. The upper and lower limit value setting module may detect a highest signal value among the echo signals obtained from the front surface of the detected part detected by the front surface position detecting module, and may set the highest signal value as the upper limit value, and the ultrasonic diagnosing device further may include an echo level normalizing module configured to divide the echo intensities at the respective positions of the analysis area by the highest signal value detected by the upper and lower limit value setting module. 
     (12) The ultrasonic diagnosing device may further include a front surface position correcting module configured to correct positions of the samples corresponding to the area-of-interest in the depth direction so that the position of the front surface of the detected part in the area-of-interest is located within a given range in the depth direction. 
     (13) The ultrasonic diagnosing device may further include the ultrasonic probe configured to transmit the ultrasonic signals into the detected body, and a display unit configured to display one of the one or more characteristic amounts calculated by the characteristic amount calculating module and an index derived based on the one or more characteristic amounts and indicating the state of the detected part of the detected body. 
     (14) Moreover, the ultrasonic probe may be capable of transmitting and receiving ultrasonic waves in relation to the area-of-interest defined in the depth direction and a scanning direction of the ultrasonic probe, by scanning along the front surface of the detected body, the scanning direction intersecting the depth direction. 
     (15) In order to solve the subject described above, according to one aspect of the present disclosure, a method of ultrasonic diagnosis of a state of a detected part that is a detection target in a detected body is provided. The method includes assigning an echo intensity to one of a plurality of levels of echo intensities, the echo intensity calculated based on one of echo signals that are caused by ultrasonic signals transmitted from an ultrasonic probe into the detected body, and being an intensity of each of the echo signals that are samples respectively corresponding to positions in an area-of-interest of the detected body, the area-of-interest defined in a depth direction of the detected body and a direction intersecting the depth direction. The method includes calculating, by targeting two or more of the samples having the echo intensities assigned to the plurality of levels by the assigning the echo intensity to one of the plurality of levels of echo intensities, one or more characteristic amounts indicating a characteristic of the area-of-interest, based on a combination of the echo intensities of the two or more of the samples, the two or more of the samples having a given positional relationship with each other. 
     In order to solve the subject described above, according to one aspect of the present disclosure, a program for ultrasonic diagnosis of a state of a detected part that is a detection target in a detected body is provided. The program causes a computer to execute assigning an echo intensity to one of a plurality of levels of echo intensities, the echo intensity calculated based on one of echo signals that are caused by ultrasonic signals transmitted from an ultrasonic probe into the detected body, and being an intensity of each of the echo signals that are samples respectively corresponding to positions in an area-of-interest of the detected body, the area-of-interest defined in a depth direction of the detected body and a direction intersecting the depth direction. The program causes a computer to execute calculating, by targeting two or more of the samples having the echo intensities assigned to the plurality of levels by the assigning the echo intensity to one of the plurality of levels of echo intensities, one or more characteristic amounts indicating a characteristic of the area-of-interest, based on a combination of the echo intensities of the two or more of the samples, the two or more of the samples having a given positional relationship with each other. 
     Effects of the Disclosure 
     According to the present disclosure, even in a case of analyzing a state of a detected part in a percutaneous manner, the state of the detected part can accurately be grasped. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of an ultrasonic diagnosing device according to one embodiment of this disclosure. 
         FIGS. 2(A) and 2(B)  show schematic views illustrating an installed state of a probe of the ultrasonic diagnosing device on a knee. 
         FIGS. 3(A) and 3(B)  show schematic side views of an area near the knee in the state where the probe is installed thereon, in which Part (A) is a view illustrating a first state and Part (B) is a view illustrating a second state. 
         FIG. 4  is a block diagram illustrating a configuration of a signal processor of the ultrasonic diagnosing device illustrated in  FIG. 1 . 
         FIG. 5  is a view illustrating an example of an echo level image generated by an image generating module. 
         FIG. 6  is a view illustrating an example of an echo level image after a front surface position of a cartilage is corrected. 
         FIG. 7  is a view illustrating an example of an area-of-interest image assigned with gradation. 
         FIG. 8  is a schematic view illustrating a positional relationship between a pair of pixels which are generation targets of a co-occurrence matrix. 
         FIG. 9  is a chart used to calculate a correlation coefficient between a correlation COR d5θ90  and a front surface roughness of the cartilage. 
         FIG. 10  is a chart used to calculate a correlation coefficient between a contrast CNT d1θ0  and the front surface roughness of the cartilage. 
         FIG. 11  is a flowchart illustrating operation of the signal processor. 
         FIG. 12  is a view illustrating an example of waveforms of respective echo signals in the first state [T 1 ] and the second state [T 2 ]. 
         FIG. 13  is a block diagram illustrating a configuration of a signal processor of the ultrasonic diagnosing device according to a modification. 
         FIG. 14  is a chart used to calculate a correlation coefficient between a contrast CNT d5θ90  and the front surface roughness of the cartilage. 
         FIG. 15  is a block diagram illustrating a configuration of an ultrasonic diagnosing device according to another modification. 
         FIG. 16  is a block diagram illustrating a configuration of an ultrasonic diagnosing device according to another modification. 
     
    
    
     MODES FOR CARRYING OUT THE DISCLOSURE 
     A signal processor  10  and an ultrasonic diagnosing device  1  including the signal processor  10  according to one embodiment of this disclosure are described with reference to the drawings.  FIG. 1  is a block diagram illustrating a configuration of the ultrasonic diagnosing device  1  according to the embodiment of this disclosure. The ultrasonic diagnosing device  1  diagnoses a state of a cartilage (detected part) of a knee (detected body) of a patient. 
       FIGS. 2(A) and 2(B)  show schematic views illustrating an installed state of a probe  4  of the ultrasonic diagnosing device  1  according to the embodiment of this disclosure on the detected body.  FIG. 2(A)  illustrates a case in a first state (t=T 1 ) and  FIG. 2(B)  illustrates a case in a second state (t=T 2 ). 
     With the ultrasonic diagnosing device  1 , in a state where the probe  4  is made in contact with a front surface of the knee, the probe  4  is moved in up-and-down directions of the knee to switch a relative position thereof to a soft tissue  903  and the cartilage  901 , between a position in the first state illustrated in  FIG. 2(A)  and a position in the second state illustrated in  FIG. 2(B) . Further, with the ultrasonic diagnosing device  1 , ultrasonic waves are transmitted from the probe  4  in each state, and based on echo signals obtained in each state, an index indicating a state of the cartilage  901  (e.g., roughness of the cartilage front surface) is calculated as a numerical value. A user of the ultrasonic diagnosing device  1  (e.g., doctor) looks at the index displayed on a display unit  5  to diagnose the state of the cartilage of a knee joint of the patient. 
     Overall Configuration 
     As illustrated in  FIG. 1 , the ultrasonic diagnosing device  1  includes a user interface  2 , a transmission controller  3 , the probe  4 , the signal processor  10 , and the display unit  5 . 
     The user interface  2  is, for example, comprised of one of a keyboard and a touch panel, and receives an operational input from the user. In response to the operational input from the user, the user interface  2  commands the transmission controller  3  to start a detection of the cartilage front surface. Further, the user interface  2  outputs a command to set or switch a display mode of the display unit  5  to the display unit  5  in response to the operational input from the user. Note that, the user interface  2  may be incorporated with the display unit  5 . 
     The transmission controller  3  generates pulse-shaped ultrasonic signals. The transmission controller  3  generates the ultrasonic signals in each of the first state [T 1 ] and the second state [T 2 ]. 
     The transmission controller  3  outputs the ultrasonic signals to the probe  4 . The probe  4  includes a plurality of oscillators  4   a  arrayed in a direction parallel to a wave transmitting and receiving surface (see  FIGS. 3(A) and 3(B) ). This array direction of the oscillators  4   a  becomes a scanning direction. The oscillators  4   a  transmit the ultrasonic signals into the detected body, respectively. Each oscillator  4   a  transmits the ultrasonic signal at a given time interval and receives a reflection echo signal caused thereby. 
     The probe  4  includes the plurality of oscillators  4   a . As illustrated in  FIGS. 2(A) and 2(B) , the probe  4  is arranged such that an end surface thereof on the wave transmitting and receiving surface side comes in contact with a front surface of the soft tissue  903  of the knee which is the detected body. Here, as illustrated in  FIGS. 3(A) and 3(B) , the soft tissue  903  is a part existing on the front surface side of the detected body with respect to the cartilage  901 . The cartilage  901  is attached to a subchondral bone  911 . The subchondral bone  911  is a tissue coupled to a bone (cancellous bone)  902 . 
     Note that the probe may include only one oscillator. In this case, a moving direction of the oscillator becomes the scanning direction. 
     The probe  4  is moved along the front surface of the soft tissue  903  as illustrated in  FIG 2(B) , while being in contact with the front surface as illustrated in  FIG. 2(A) . Thus, as illustrated in  FIGS. 2(A) and 2(B) , the soft tissue  903  moves by following the probe  4  while sliding on the front surface of the cartilage  901 . The state of  FIG. 2(A) , which is before the probe  4  is moved, is the first state (t=T 1 ), and the state of  FIG. 2(B) , which is after the probe  4  is moved, is the second state (t=T 2 ). Here, the probe  4  is moved in the array direction (scanning direction) of the oscillators. 
     Each oscillator  4   a  transmits the ultrasonic signal into the detected body in each of the first state [T 1 ] and the second state [T 2 ]. Here, the oscillator  4   a  of the probe  4  transmits the ultrasonic signal such that a direction orthogonal to the front surface of the soft tissue  903  becomes a direction of a center axis of the transmission beam. 
     Each oscillator  4   a  receives the echo signal caused by the ultrasonic signal reflecting on the soft tissue  903  and the cartilage  901  inside the detected body, and outputs it to the signal processor  10 . The probe  4  outputs to the signal processor  10  a first echo group SW[T 1 ] including the echo signals obtained by the oscillators  4   a  in the first state [T 1 ] and a second echo group SW[T 2 ] including the echo signals obtained by the oscillators in the second state [T 2 ]. 
     The signal processor  10  analyzes the state of the cartilage  901  based on the respective echo signals, and outputs the analysis result to the display unit  5 . Specific configuration and operation of the signal processor  10  are described later in detail. 
     The display unit  5  displays the analysis result of the cartilage  901  obtained by the analysis at the signal processor  10 . Specifically, the display unit  5  displays characteristic amounts as indexes indicating the state of the cartilage, which is calculated by the signal processor  10 . The user estimates the state of the cartilage  901  of the knee of the patient based on the characteristic amounts. 
     Configuration of Signal Processor 
       FIG. 4  is a block diagram illustrating a configuration of the signal processor  10  of the ultrasonic diagnosing device  1  according to this embodiment. As illustrated in  FIG. 4 , the signal processor  10  includes an echo signal receiver  11 , an AD converter  12 , a front surface position detecting module  13 , an image generating module  14 , an echo level normalizing module  15 , a front surface position correcting module  16 , a dynamic range designing module  17 , an area-of-interest designing module  18 , a gradation module  19 , a co-occurrence matrix generating module  20 , and a characteristic amount calculating module  21 . The signal processor  10  is comprised of hardware including a CPU, a RAM and a ROM (not illustrated). Further, the signal processor  10  is configured by using software including an ultrasonic diagnosing program stored in the ROM. 
     The ultrasonic diagnosing program is a program that causes the signal processor  10  to implement an ultrasonic diagnosing method according to one embodiment of this disclosure. This program can be installed externally. This program installed is distributed in a state where it is stored in a recording medium, for example. The hardware and the software are configured to operate in cooperation with each other. Thus, the signal processor  10  can function as the echo signal receiver  11 , the AD converter  12 , the front surface position detecting module  13 , the image generating module  14 , the echo level normalizing module  15 , etc., which are described above. 
     The echo signal receiver  11  performs a given amplification on each echo signal, and outputs it to the AD converter  12 . The echo signal receiver  11  amplifies the respective echo signals individually for each of the first and second echo groups SW[T 1 ] and SW[T 2 ], and outputs them to the AD converter  12 . 
     The AD converter  12  samples each echo signal at a given time interval to discretize data. The echo signal sampled to be the discretized data becomes the echo data. Thus, echo data caused by the data sampling in a depth direction of the detected body at the given time interval can be obtained. The AD converter  12  outputs the echo data to the front surface position detecting module  13  and the image generating module  14 . 
     The front surface position detecting module  13  has a memory  13   a  and a determining submodule  13   b.    
     The memory  13   a  has enough volume to store a plurality of echo data obtained in the first state [T 1 ] and a plurality of echo data obtained in the second state [T 2 ]. The memory  13   a  stores the respective echo data outputted by the AD converter  12 . 
     Although specific processing is described later, the determining submodule  13   b  compares waveforms (echo data row in a sweep) obtained from each observed area in the first state [T 1 ], with waveforms (echo data row in a sweep) obtained from each comparison target area in the second state. Based on a result of this comparison, the determining submodule  13   b  detects a position of the comparison target area in the second state to which the selected observed area corresponds. 
     The determining submodule  13   b  detects a comparison target area in the second state [T 2 ] that is most similar to the observed area in the first state [T 1 ]. The determining submodule  13   b  detects a positional change (whether the position is not changed) of the area where the waveform (or a representative position of the area) is most similar between the first state [T 1 ] and the second state [T 2 ]. Based on a difference in tendency of the positional change of the area, the determining submodule  13   b  identifies an area corresponding to the soft tissue and an area corresponding to the cartilage, and detects a front surface position of the cartilage  901 . 
       FIG. 5  is a view illustrating an example of an echo level image generated by the image generating module  14 . Based on the echo data from the AD converter  12 , the image generating module  14  generates the echo level image based on echo signals from positions in an analysis area defined in the scanning direction of the ultrasonic probe  4  (a direction intersecting with the depth direction of the detected body) and a depth direction of the cartilage  901  (a direction perpendicular to the scanning direction and extending to the inner side of the knee), for example the image illustrated in  FIG. 5 . The echo level image is configured with a plurality of pixels arrayed in a grid form. Each pixel is disposed at a position of a display screen associated with a corresponding position of the analysis area, and has a luminance level corresponding to an echo intensity at the corresponding position of the analysis area. In this embodiment, for example, the luminance level is displayed in association with color tones which gradually change in an order of red, orange, yellow, green, blue, and dark blue, as the luminance level changes from high to low. 
     The echo level normalizing module  15  detects an intensity of an echo signal (echo intensity) that is highest among the echo signals from the respective positions of the analysis area, and divides the echo intensities at the respective positions of the analysis area by the highest echo intensity. Specifically, the echo intensities at the respective positions of the analysis area are normalized so that a highest value thereamong becomes 0 dB. 
       FIG. 6  is a view illustrating an example of the echo level image after the front surface position of the cartilage  901  is corrected. The front surface position correcting module  16  corrects the front surface position of the cartilage  901  in the echo level image generated by the image generating module  14 , so that the front surface position is located within a given range in the depth direction (becomes substantially straight). For example, the front surface position correcting module  16  corrects the front surface position of the cartilage  901  in the echo level image to be substantially straight by suitably performing delay processing on the echo signal corresponding to each front surface position in the scanning direction. 
     The dynamic range designing module  17  is provided as an upper and lower limit value setting module configured to set an upper limit value (upper limit echo intensity) and a lower limit value (lower limit echo intensity) of the echo intensities at the respective positions of the analysis area. The dynamic range designing module  17  sets the upper limit value to be the highest level value (0 dB) among the signal levels normalized by the echo level normalizing module  15 , and designs the lower limit value to be −40 dB for example. The lower limit value (−40 dB) is a value obtained experimentally, and is set to be a value with which a scattering echo in an area starting from the cartilage front surface to the inside of the cartilage can be detected. 
     Based on the analytical data (the front surface position of the cartilage) calculated by the front surface position detecting module  13 , the area-of-interest designing module  18  designs an area having a given length in the depth direction from a given position of the front surface of the cartilage (e.g., about 0.24 mm) and a given length of the front surface in the scanning direction (e.g., about 4 mm), to be an area-of-interest. 
       FIG. 7  is a view illustrating an example of an area-of-interest image assigned with gradation. The gradation module  19  assigns gradation of a plurality of levels (e.g., sixteen tones) to luminance levels of respective pixels of the area-of-interest image that is the echo level image of inside the area-of-interest designed by the area-of-interest designing module  18 . Specifically, the gradation module  19  is provided as a level assigning module configured to assign each echo intensity to one of a plurality of levels of echo intensities. Note that, in the example illustrated in  FIG. 7 , an example of the area-of-interest image assigned with gradation of four tones is illustrated. 
     The co-occurrence matrix generating module  20  generates a co-occurrence matrix based on the echo level image of inside the area-of-interest in which the luminance levels of the respective pixels are assigned with the gradation of the sixteen tones. The co-occurrence matrix is a matrix of which element is probability Pδ(i, j) (i, j=1, 2, . . . , n−1) that a pixel located at a position with a certain displacement δ=(d, θ) (d is a distance and θ is an angle, see  FIG. 8 ) from a pixel with a gradient of i has a gradient of j. Specifically, the co-occurrence matrix is given by the following Equation 1. 
     
       
         
           
             
               
                 
                   
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     In this embodiment, the co-occurrence matrix generating module  20  generates two co-occurrence matrixes (a first co-occurrence matrix P d5θ90 (i, j) and a second co-occurrence matrix P d1θ0 (i, j)). The first co-occurrence matrix P d5θ90 (i, j) is generated targeting pairs of pixels, each pair separated from each other by five pixels in the scanning direction. Further, the second co-occurrence matrix P d1θ0 (i, j) is generated targeting pairs of pixels, each pair separated from each other by one pixel in the depth direction. Note that, a value d indicating a distance between the pair of pixels is a preset value based on experiment(s) etc.; however, without limiting to the value described above, it is suitably set according to sizes of the pixels, a beam diameter, a scanning step, a sampling frequency, etc. 
     The characteristic amount calculating module  21  calculates given characteristic amounts based on the co-occurrence matrixes generated by the co-occurrence matrix generating module  20 . In this embodiment, the characteristic amount calculating module  21  calculates a correlation COR and a contrast CNT as the characteristic amounts. Specifically, the characteristic amount calculating module  21  calculates a correlation COR d5θ90  based on the first co-occurrence matrix P d5θ90 (i, j) and a contrast CNT d1θ0 (i, j) based on the second co-occurrence matrix P d1θ0 (i, j). The correlation COR and the contrast CNT are given by the following Equations 2 and 3. 
                   COR   =       1       σ   x     ⁢     σ   y         ⁢       ∑     i   =   0       n   -   1       ⁢       ∑     j   =   0       n   -   1       ⁢     {       ijP   ⁢           ⁢     δ   ⁡     (     i   ,   j     )         -       μ   x     ⁢     μ   y         }                   (   2   )               
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       FIG. 9  is a chart used to calculate a correlation coefficient between the correlation COR d5θ90  calculated based on Equation 2 and the front surface roughness of the cartilage, targeting a plurality of samples (N=26). As illustrated in  FIG. 9 , a comparatively negatively-high correlation was found between the correlation COR d5θ90  in the direction parallel to the cartilage front surface and the front surface roughness. A cause of the negative correlation can be considered to be that the echo intensity is substantially even in an in-plane direction (a direction where θ=90°) of the cartilage front surface when the cartilage has low degeneration degree (cartilage with low roughness), while the echo intensity varies in the in-plane direction of the cartilage front surface when the cartilage has high degeneration degree (cartilage with high roughness). Therefore, it can be estimated that the degeneration degree of the cartilage is low when the correlation COR d5θ90  calculated by the characteristic amount calculating module  21  is high, and the degeneration degree of the cartilage is high when the correlation COR d5θ90  is low. 
       FIG. 10  is a chart used to calculate a correlation coefficient between the contrast CNT d1θ0  calculated based on Equation 3 and the front surface roughness of the cartilage, targeting the plurality of samples (N=26). As illustrated in  FIG. 10 , a comparatively negatively-high correlation was found between the contrast CNT d1θ0  in the direction perpendicular to the cartilage front surface and the front surface roughness. A cause of the negative correlation can be considered to be that the echo intensity changes dramatically in the depth direction from the echo intensity at the cartilage front surface when the cartilage has low degeneration degree, while the echo intensity is less likely to change dramatically when the cartilage has high degeneration degree. Therefore, it can be estimated that the degeneration degree of the cartilage is low when the contrast CNT d1θ0  calculated by the characteristic amount calculating module  21  is high, and the degeneration degree of the cartilage is high when the contrast CNT d1θ0  is low. 
     Operation of Signal Processor 
       FIG. 11  is a flowchart illustrating the operation of the signal processor  10 . The operation of the signal processor  10  is described with reference to  FIG. 11 . 
     First at S 1 , the echo signal receiver  11  amplifies the respective echo signals individually for each of the first and second echo groups SW[T 1 ] and SW[T 2 ], and outputs them to the AD converter  12 . 
     Next at S 2 , the AD converter  12  samples each of the echo signals in the first and second echo groups SW[T 1 ] and SW[T 2 ] at the given time interval to discretize the data. The AD converter  12  outputs each discretized echo data to the front surface position detecting module  13 , and outputs the echo data of one of the two echo groups to the image generating module  14 . 
     Next at S 3 , the front surface position detecting module  13  detects the front surface position of the cartilage  901 . Here, a more specific method of detecting the cartilage front surface, which is implemented by the front surface position detecting module  13  at S 3 , is described with reference to  FIGS. 3 and 12 . Note that, to simplify the description, a moving distance Δx of the probe  4  (oscillators  4   a ) between the first and second states [T 1 ] and [T 2 ] is described to be in match with the arrangement interval of the oscillators. 
     First, as the first state [T 1 ], the probe  4  is made in contact with the front surface of the knee in a state where the knee, which is the detected body, is bent at a first angle, for example. In other words, the probe  4  is made in contact with the front surface of the soft tissue  903 , which corresponds to the state of  FIG. 3(A) . 
     The respective oscillators disposed at the given arrangement interval, transmit the ultrasonic signals to the direction orthogonal to the front surface of the soft tissue  903  (the scanning direction orthogonal to the wave transmitting and receiving surface). In the example of  FIGS. 3(A) and 3(B) , five oscillators are disposed in the probe  4  at an even interval in the scanning direction, and as illustrated in  FIG. 3(A) , the oscillators disposed at the respective arrangement positions transmit the ultrasonic signals to the direction orthogonal to the front surface of the soft tissue  903 . The ultrasonic signals from the respective arrangement positions reflect and scatter at respective depth positions of the soft tissue  903 , the cartilage  901 , and the subchondral bone  911 , and thus, echo signals SWT 11 , SWT 12 , SWT 13 , SWT 14  and SWT 15  from respective positions which have a given space interval from each other in the scanning direction (the scanning-directional positions) are obtained. The oscillators receive the echo signals, respectively. The echo signal group of these echo signals SWT 11 , SWT 12 , SWT 13 , SWT 14  and SWT 15  obtained by the respective oscillators is the first echo group SW[T 1 ]. 
     Next, the probe  4  is moved to the direction parallel to the front surface of the soft tissue  903  and parallel to the scanning direction, by the distance Δx in the state where the probe  4  is made in contact with the soft tissue  903 , which corresponds the second state [T 2 ] and the state of  FIG. 3(B) . Here, the soft tissue  903  moves following the movement of the probe  4 . Therefore, a relative positional relationship of the wave transmitting and receiving surface of the probe  4  with respective positions of the soft tissue  903  in the scanning direction does not change corresponding to the movement of the probe  4 . On the other hand, the cartilage  901  is fixed to the bone  902  via the subchondral bone  911  and, thus, does not move even when the probe  4  is moved. Therefore, a relative positional relationship of the wave transmitting and receiving surface of the probe  4  with respective positions of the cartilage  901  in the scanning direction changes corresponding to the movement of the probe  4 . 
     After shifting to the second state, as illustrated in  FIG. 3(B) , the ultrasonic signals are transmitted from the respective oscillators of the probe  4  to the direction orthogonal to the front surface of the soft tissue  903  (the scanning direction orthogonal to the wave transmitting and receiving surface). The ultrasonic signals from the respective scanning-directional positions reflect and scatter at respective depth positions of the soft tissue  903 , the cartilage  901 , and the subchondral bone  911 , and thus, echo signals SWT 21 , SWT 22 , SWT 23 , SWT 24  and SWT 25  from the respective positions which have a given space interval from each other in the scanning direction are obtained. The oscillators receive the echo signals, respectively. The echo signal group of these echo signals SWT 21 , SWT 22 , SWT 23 , SWT 24  and SWT 25  obtained by the respective oscillators is the second echo group SW[T 2 ]. 
     As described above, the first echo group SW[T 1 ] including the plurality of echo signals SWT 11 , SWT 12 , SWT 13 , SWT 14  and SWT 15  is acquired before the probe  4  is moved. Further, the second echo group SW[T 2 ] including the plurality of echo signals SWT 21 , SWT 22 , SWT 23 , SWT 24  and SWT 25  is acquired after the probe  4  is moved. 
       FIG. 12  is a view illustrating an example of waveforms of the respective echo signals in the first state [T 1 ] and the second state [T 2 ]. Note that in  FIG. 12 , for easier illustration of characteristics of the present disclosure, the distance Δx by which the probe  4  is moved is the same as the space interval between the oscillators, in other words, the interval between the scanning-directional positions. Further in the following description, the detection of the front surface of the cartilage  901  under this condition is described. 
     (i) Soft Tissue  903   
     As described above, the probe  4  is made in contact with the front surface of the soft tissue  903  and the soft tissue  903  is not fixed to the front surface of the cartilage  901 . Therefore, when the probe  4  is moved by the distance Δx, the soft tissue  903  also moves by the distance Δx, following the movement of the probe  4 . 
     In this case, as indicated by the waveforms of the respective echo signals in the first state [T 1 ] and the waveforms of the respective echo signals in the second state [T 2 ] in  FIG. 12 , the waveform of the echo signal SWT 11  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 21  of the second echo group SW[T 2 ] in a portion corresponding to the area of the soft tissue  903 . 
     Similarly, the waveform of the echo signal SWT 12  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 22  of the second echo group SW[T 2 ] in a portion corresponding to the area of the soft tissue  903 . The waveform of the echo signal SWT 13  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 23  of the second echo group SW[T 2 ] in a portion corresponding to the area of the soft tissue  903 . The waveform of the echo signal SWT 14  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 24  of the second echo group SW[T 2 ] in a portion corresponding to the area of the soft tissue  903 . The waveform of the echo signal SWT 15  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 25  of the second echo group SW[T 2 ] in a portion corresponding to the area of the soft tissue  903 . 
     Therefore, in the soft tissue  903 , the echo signals at the scanning-directional positions in the first state [T 1 ] substantially match with the echo signals at the scanning-directional positions in the second state [T 2 ], respectively, in terms of the position thereof with respect to the probe  4  in the scanning direction. 
     (ii) Cartilage  901   
     Even when the probe  4  is moved, the cartilage  901  does not move. Therefore, when the probe  4  is moved by the distance Δx, the relationship between the position of each oscillator of the probe  4  (each scanning-directional position) and a corresponding position of the cartilage  901  shifts by the distance Δx in the scanning direction. 
     In this case, as indicated by the waveforms of the respective echo signals in the first state [T 1 ] and the waveforms of the respective echo signals in the second state [T 2 ] in  FIG. 12 , the waveform of the echo signal SWT 11  of the first echo group SW[T 1 ] does not match with that of the echo signal SWT 21  of the second echo group SW[T 2 ] in a portion corresponding to the area of the cartilage  901 , but substantially matches with the waveform of the echo signal SWT 22  of the second echo group SW[T 2 ] in a portion corresponding to the area of the cartilage  901 . 
     Similarly, the waveform of the echo signal SWT 12  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 23  of the second echo group SW[T 2 ] in a portion corresponding to the area of the cartilage  901 . The waveform of the echo signal SWT 13  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 24  of the second echo group SW[T 2 ] in a portion corresponding to the area of the cartilage  901 . The waveform of the echo signal SWT 14  of the first echo group SW[T 1 ] substantially matches with that of the echo signal SWT 25  of the second echo group SW[T 2 ] in a portion corresponding to the area of the cartilage  901 . 
     Therefore, in the cartilage  901 , the echo signal from each scanning-directional position in the first state [T 1 ] substantially matches with the echo signal from a scanning-directional position in the second state [T 2 ], which is offset from the scanning-directional position in the first state [T 1 ] by the arrangement interval of adjacent oscillators. 
     As described above, the echo data from the soft tissue  903  and the echo data from the cartilage  901  behave differently from each other in the first and second states [T 1 ] and [T 2 ]. Therefore, by detecting this behavior (a change of a relative position of the observed point between the first and second states), the area of the soft tissue  903  can be differentiated from the area of the cartilage  901 . Further, the cartilage front surface, which is a boundary surface of the soft tissue  903  and the cartilage  901  can be detected. 
     Meanwhile at S 4 , the image generating module  14  generates the echo level image as illustrated in  FIG. 5 , based on the echo data outputted from the AD converter  12 . 
     Next at S 5 , the echo level normalizing module  15  normalizes the echo intensities at the respective positions of the analysis area. 
     Next at S 6 , the front surface position correcting module  16  corrects the echo level image so that the front surface position of the cartilage  901  in the echo level image is located within the given range in the depth direction. Note that, if the front surface position of the cartilage  901  in the echo level image is located within the given range in the depth direction, the process at S 6  is omitted. 
     Next at S 7 , the dynamic range designing module  17  sets the upper limit value to be the highest value (0 dB) among the signal levels normalized by the echo level normalizing module  15 , and sets the lower limit value to be −40 dB. 
     Next at S 8 , the area-of-interest designing module  18  designs the area having the given length in the depth direction from the given position of the front surface of the cartilage and the given length of the front surface in the scanning direction, to be the area-of-interest. 
     Next at S 9 , the gradation module  19  assigns the gradation of the plurality of levels (e.g., sixteen tones) to the luminance levels of the respective pixels of the area-of-interest image which is the echo level image of inside of the area-of-interest designed at S 8 . 
     Next at S 10 , the co-occurrence matrix generating module  20  generates the first co-occurrence matrix P d5θ90 (i, j) and the second co-occurrence matrix P d1θ0 (i, j) based on Equation 1. 
     Next at S 11 , the characteristic amount calculating module  21  calculates the correlation COR d5θ90  and the contrast CNT d1θ0  based on the first co-occurrence matrix P d5θ90 (i, j) and the second co-occurrence matrix P d1θ0 (i, j) generated at S 10  based on Equations 2 and 3, respectively. The correlation COR d5θ90  and the contrast CNT d1θ0  calculated as above are displayed on the display unit  5  as the numerical values. 
     Effects 
     As described above, with the ultrasonic diagnosing device  1  according to this embodiment, without incision of the soft tissue  903  near the knee, the characteristic amounts which are highly correlative with the state of the detected part (the front surface roughness of the cartilage  901  in this embodiment) is calculated based on the intensities of the echo signals which are the samples corresponding to the respective positions of the area-of-interest, and the state of the cartilage can be estimated. 
     Therefore, with the ultrasonic diagnosing device  1 , even in a case of analyzing the state of the cartilage  901  in a percutaneous manner, the state (front surface roughness) of the cartilage  901  can accurately be grasped. 
     Moreover, with the ultrasonic diagnosing device  1 , since the characteristic amounts are calculated based on the echo level image configured with the pixels having the illuminance levels corresponding to the echo intensities of the samples corresponding to the respective positions of the area-of-interest, the characteristic amounts can suitably be calculated. 
     Moreover, with the ultrasonic diagnosing device  1 , the upper limit echo intensity and the lower limit echo intensity are set by the dynamic range designing module  17 . Thus, the gradation can suitably be assigned to the respective pixels configuring the echo level image. 
     Moreover, with the ultrasonic diagnosing device  1 , since the area including the echo signals from the cartilage front surface of the knee is designed to be the area-of-interest, the detected part can surely be included in the diagnostic target. 
     Moreover, with the ultrasonic diagnosing device  1 , the characteristic amounts are calculated based on the co-occurrence matrixes calculated by the co-occurrence matrix generating module  20 . Thus, the characteristic amounts can suitably be calculated. 
     Moreover, with the ultrasonic diagnosing device  1 , by calculating, as one of the characteristic amounts, the correlation COR highly correlative with the front surface roughness of the cartilage  901 , the front surface roughness of the cartilage  901  can suitably be estimated. 
     Moreover, with the ultrasonic diagnosing device  1 , in the area-of-interest image, the correlation COR d5θ90  is calculated based on the first co-occurrence matrix P d5θ90  generated targeting the pairs of pixels, each pair of pixels consisting of a pair of pixels having a positional relationship in which they are separated by a given distance in the scanning direction. As illustrated in  FIG. 9 , the correlation COR d5θ90  is highly correlative with the front surface roughness. Therefore, by calculating the correlation COR d5θ90 , the front surface roughness of the cartilage  901  can more suitably be estimated. 
     Moreover, with the ultrasonic diagnosing device  1 , by calculating, as one of the characteristic amounts, the contrast CNT highly correlative with the front surface roughness of the cartilage  901 , the front surface roughness of the cartilage  901  can suitably be estimated. 
     Moreover, with the ultrasonic diagnosing device  1 , in the area-of-interest image, the contrast CNT d1θ0  is calculated based on the second co-occurrence matrix P d1θ0  generated targeting the pairs of pixels, each pair of pixels consisting of a pair of pixels having a positional relationship in which they are separated by a given distance in the depth direction. As illustrated in  FIG. 10 , the contrast CNT d1θ0  is highly correlative with the front surface roughness. Therefore, by calculating the contrast CNT d1θ0 , the front surface roughness of the cartilage  901  can more suitably be estimated. 
     Moreover, with the ultrasonic diagnosing device  1 , the area-of-interest to be the analysis target is designed based on the front surface position of the cartilage  901  detected by the front surface position detecting module. Thus, the area-of-interest can automatically be designed. 
     Moreover, with the ultrasonic diagnosing device  1 , the echo intensities at the respective positions in the echo level image are normalized through dividing them by the highest signal value among the echo signals from the cartilage  901 . In this manner, an individual difference of the soft tissue  903  in every detected body can be eliminated, and thus, more accurate characteristic amounts can be calculated for each detected body. 
     Moreover, with the ultrasonic diagnosing device  1 , the echo level image is corrected so that the front surface position of the cartilage  901  in the echo level image is located within the given range in the depth direction. Thus, the front surface position of the cartilage  901  becomes substantially straight in the depth direction, and as a result, the co-occurrence matrix can suitably be generated. 
     Moreover, with the ultrasonic diagnosing device  1 , the characteristic amounts calculated by the signal processor  10  are displayed on the display unit  5 . Thus, the user can visually confirm the characteristic amounts as the indexes indicating the degeneration degree of the cartilage  901 . 
     Although the embodiment of this disclosure is described above, this disclosure is not limited to the above, and without deviating from the scope of this disclosure, various modifications may be applied. 
     Modifications 
     (1)  FIG. 13  is a block diagram illustrating a configuration of a signal processor  10   a  of the ultrasonic diagnosing device according to a modification. The signal processor  10   a  of this modification has a configuration in which the front surface position detecting module  13  and the area-of-interest designing module  18  are omitted from the signal processor  10  of the above embodiment. 
     With the ultrasonic diagnosing device according to this modification, the echo level image generated by the image generating module  14  is displayed on the display unit  5 . Further, the user looks at the echo level image and selects part of the echo level image which includes the cartilage front surface, to be the area-of-interest. Then the signal processor  10  assigns the gradation, generates the co-occurrence matrixes, and calculates the characteristic amounts, sequentially for the area-of-interest image which is the echo level image of inside the area-of-interest. Therefore, by configuring the signal processor  10   a  as this modification, the state (front surface roughness) of the cartilage  901  can accurately be grasped even in the case of analyzing the state of the cartilage  901  in a percutaneous manner, similar to the above embodiment. 
     (2) In the above embodiment, the contrast CNT d1θ0  is calculated based on the second co-occurrence matrix P d1θ0 (i, j); however, a contrast CNT d5θ90  may be calculated based on the first co-occurrence matrix P d5θ90 (i, j). 
       FIG. 14  is a chart used to calculate a correlation coefficient between the contrast CNT d5θ90  calculated based on Equation 3 and the front surface roughness of the cartilage, targeting the plurality of samples. As illustrated in  FIG. 14 , a positive correlation was found between the contrast CNT d5θ90  in the direction parallel to the cartilage front surface and the front surface roughness. A cause of the positive correlation can be considered to be that the echo intensity is substantially even in the in-plane direction of the cartilage front surface when the cartilage has low degeneration degree, while an area where the echo intensity is locally low exists when the cartilage has high degeneration degree. Therefore, it can be estimated that the degeneration degree of the cartilage is low when the contrast CNT d5θ90  is low, and the degeneration degree of the cartilage is high when the contrast CNT d5θ90  is high. 
     (3) In the above embodiment, as the characteristic amounts, the correlation COR and the contrast CNT are calculated; however, without limiting to this, other characteristic amounts may be calculated. For example, a local homogeneity IDM, an entropy EPY, a sum average SUMA, a sum variance SUMV, etc. are calculated as characteristic amounts, and the degeneration degree of the cartilage may be estimated based thereon. These characteristic amounts can be given by the following Equations 4 to 7, respectively. 
     
       
         
           
             
               
                 
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     (4) In the above embodiment, by moving the probe  4  in the up-and-down directions in the state where it is made in contact with the knee, the position of the probe  4  relative to the soft tissue  903  and the cartilage  901  is changed and the front surface position of the cartilage  901  is detected; however, it is not limited to this. For example, the probe  4  may be fixed and the knee may be bent by a jig etc., so as to change the relative positional relationships of the probe  4  with the soft tissue  903  and the cartilage  901 . 
     (5) In the above embodiment, the depth position detected by the front surface position detecting module  13  is the front surface position of the cartilage  901 ; however, it is not limited to this. For example, movement averaging processing may be performed along the front surface position detected by the front surface position detecting module  13 . Thus, a noise (e.g., spike noise) in the front surface position detection can be smoothened. 
     (6) In the above embodiment, the numerical values of the characteristic amounts calculated by the characteristic amount calculating module  21  are displayed on the display unit  5  as they are; however, without limiting to this, indexes indicating the degeneration degree of the cartilage derived based on the characteristic amounts may be displayed on the display unit  5 . For example, each of the characteristic amounts may be categorized into one of a plurality of ranks corresponding to the numerical value of the characteristic amount, and the ranks (e.g., alphabets, such as A to C) may be displayed on the display unit  5 . 
     (7)  FIG. 15  is a block diagram illustrating a configuration of an ultrasonic diagnosing device  1   a  according to another modification. In the above embodiment, the ultrasonic diagnosing device  1  including the ultrasonic probe  4  and the display unit  5  is exemplarily illustrated; however, without limiting to this, this disclosure may be applied to an ultrasonic diagnosing device in which the ultrasonic probe  4 , the display unit  5 , etc. are omitted, such as that illustrated in  FIG. 15 . 
     (8) In the above embodiment, the echo level image is generated based on the echo signals received by the probe, and the characteristic amounts are calculated based on the echo level image; however, it is not limited to this. Specifically, even without generating the echo level image, the characteristic amounts may be calculated based on the echo intensities of the samples corresponding to the respective positions of the area-of-interest. 
       FIG. 16  is a block diagram illustrating a configuration of an ultrasonic diagnosing device  1   b  according to another modification. The ultrasonic diagnosing device  1   b  according to the other modification includes a level assigning module  19   a . The level assigning module  19   a  assigns each echo intensity to one of a plurality of levels of echo intensities, the echo intensity being an intensity of the echo data outputted by the AD converter  12 , and being each of the intensities of the echo data of the samples corresponding to the respective positions of the area-of-interest. By targeting samples which are in a given positional relationship with each other among the samples having the echo intensities assigned to the plurality of levels, the characteristic amount calculating module  21  calculates the characteristic amounts based on a combination of the echo intensities. Note that, when generating the co-occurrence matrixes with the ultrasonic diagnosing device  1   b  according to this modification, the co-occurrence matrixes are generated targeting the pairs of samples corresponding to the area-of-interest, each pair of pixels consisting of a pair of samples having a positional relationship in which they are separated by a given distance in a given direction. 
     In the above embodiment, the area-of-interest is extracted from the analysis area, and the characteristic amounts are calculated based on the echo data of the samples within the area-of-interest; however, it is not limited to this. Specifically, the entire analysis area may be designed as the area-of-interest, and the characteristic amounts may be calculated based on the echo data of the samples inside the area-of-interest (i.e., the analysis area). 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1 ,  1   a ,  1   b  Ultrasonic Diagnosing Device 
           4  Probe, Ultrasonic Probe 
           19  Gradation Module (Level Assigning Module) 
           19   a  Level Assigning Module 
           21  Characteristic Amount Calculating Module