Abstract:
An ultrasonic diagnostic apparatus is provided in which overlap of a displayed ultrasonic image and displayed diagnostic data can be avoided without imposing the burden of complicated operations on the operator. 
     An ultrasonic diagnostic apparatus includes: an ultrasonic probe for transmitting an ultrasonic beam to a tissue of a biological body and receiving a reflection wave of the ultrasonic beam reflected from the tissue; an image construction section for constructing an image frame of a first image representing a tomographic image of the tissue based on the reflection wave; an image analysis section for distinguishing a region of no interest based on an image feature quantity of the image frame, the region of no interest constituting part of the image frame which is exclusive of a region of interest that includes the tomographic image of the tissue; a data generation section for generating a second image that is for display of diagnostic data; an image synthesis section for generating a synthesized image by determining a display position of the second image based on a result of the distinguishment by the image analysis section and superimposing the second image on the image frame of the first image; and a display section for displaying the synthesized image.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an ultrasonic diagnostic apparatus. More particularly, the present invention relates to a technique of displaying diagnostic data by an ultrasonic diagnostic apparatus. 
       BACKGROUND ART 
       [0002]    The techniques of displaying diagnostic data so as not to overlap a region of interest in an ultrasonic image in an ultrasonic diagnostic apparatus are disclosed in Patent Document 1 and Patent Document 2. 
         [0003]    Patent Document 1 discloses a technique of avoiding overlap of an ultrasonic image and diagnostic data, which is realized by preliminarily storing the display position of the ultrasonic image for every one of the bodies, diagnosed sites, or measurement functions and selecting a relevant one of the bodies, diagnosed sites, or measurement functions at the time of diagnosis. 
         [0004]    Patent Document 2 discloses another technique of avoiding overlap of an ultrasonic image and diagnostic data, which is realized by an operator manually changing the vertical magnification rate, horizontal magnification rate, or display position of the text data region via a user interface. 
       CITATION LIST 
     Patent Literature  
       [0005]    Patent Document 1: Japanese Laid-Open Patent Publication No. 11-326 
         [0006]    Patent Document 2: Japanese Laid-Open Patent Publication No. 9-47453 
       SUMMARY OF INVENTION 
     Technical Problem  
       [0007]    In diagnosis with the use of an ultrasonic diagnostic apparatus, an image is obtained through an ultrasonic probe which is in contact with a skin surface of a body. The position of the region of interest in the ultrasonic image may greatly vary depending on, for example, the angle of the probe or the posture of the body at the time of obtaining the image even if the same body or the same site is diagnosed. According to the aforementioned method disclosed in Patent Document 1, the display position of the diagnostic data is preliminarily stored and uniquely fixed. Therefore, the method of Patent Document 1 has difficulty in flexibly treating the variation of the position of the region of interest which may occur due to, for example, the angle of the probe or the posture of the body. 
         [0008]    Using the method disclosed in Patent Document 2 enables change of the size of the display region of the diagnostic data and movement of the display position. However, these operations need to be manually carried out by an operator and are therefore complicated. Thus, they may disturb the concentration of the operator on the diagnosis. 
         [0009]    The present invention was conceived for the purpose of solving the above problems. One of the objects of the present invention is to provide an ultrasonic diagnostic apparatus in which overlap of an ultrasonic image and diagnostic data can be avoided without imposing the burden of complicated operations on the operator. 
       Solution to Problem  
       [0010]    An ultrasonic diagnostic apparatus of the present invention includes: an ultrasonic probe for transmitting an ultrasonic beam to a tissue of a biological body and receiving a reflection wave of the ultrasonic beam reflected from the tissue; an image construction section for constructing an image frame of a first image representing a tomographic image of the tissue based on the reflection wave; an image analysis section for distinguishing a region of no interest based on an image feature quantity of the image frame, the region of no interest constituting part of the image frame which is exclusive of a region of interest that includes the tomographic image of the tissue; a data generation section for generating a second image that is for display of diagnostic data; an image synthesis section for generating a synthesized image by determining a display position of the second image based on a result of the distinguishment by the image analysis section and superimposing the second image on the image frame of the first image; and a display section for displaying the synthesized image. 
         [0011]    The image analysis section may divide the image frame into a plurality of small regions and calculate an image feature quantity of each of the small regions based on a luminance of the small region. 
         [0012]    The image analysis section may calculate a mean value and a variance value of the luminance of each of the small regions and, and if both the mean value and the variance value are smaller than predetermined threshold values, the image analysis section may recognize the small region as being the region of no interest. 
         [0013]    The image synthesis section may assign, as the display position of the second image, a region in the image frame which is recognized by the image analysis section as being the region of no interest, and generate the synthesized image. 
         [0014]    The ultrasonic diagnostic apparatus may further include a user interface for an operator to instruct a change of the display position of the second image in the displayed synthesized image, wherein if the second region overlaps the region of interest as a result of the change of the display position of the second image which is instructed by the operator via the user interface, the image synthesis section forcedly changes the display position of the second image to a position in the region of no interest. 
         [0015]    The image analysis section may continuously perform distinguishment of the region of no interest, and if the second region overlaps the region of interest as a result of movement of the region of interest within the image frame, the image synthesis section may change the display position of the second image to a position in a region which is presently recognized as the region of no interest. 
         [0016]    The image synthesis section may hold a threshold value as to a distance between the second image and the region of interest across a display screen, and the image synthesis section may assign, as the display position of the second image, such a position that the distance between the second image and the region of interest which are displayed in the display section is smaller than the threshold value. 
       Advantageous Effects of Invention  
       [0017]    According to the present invention, a region of no interest is distinguished based on an image feature quantity of an image frame, the region of no interest constituting part of the image frame which is exclusive of a region of interest that includes a tomographic image of a tissue. The display position of the second image that is to display diagnostic data is determined based on the distinguishment result, and a synthesized image is generated by superimposing the second image on an image frame of the first image. With this configuration, overlap of the ultrasonic image and the diagnostic data can be avoided without imposing the burden of complicated operations on the operator. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a diagram showing the exterior of an ultrasonic diagnostic apparatus  100  that is an embodiment of the present invention. 
           [0019]      FIG. 2  is a block diagram showing one configuration example of the ultrasonic diagnostic apparatus  100  that is an embodiment of the present invention. 
           [0020]      FIG. 3  is a flowchart illustrating the operation procedure of the ultrasonic diagnostic apparatus  100 . 
           [0021]      FIG. 4  is a diagram showing a synthesized image  400  displayed on a monitor  107 . 
           [0022]      FIG. 5(   a ) is a diagram showing an image  500   a  where the arrangement of a diagnostic data image  503   a  is not adjusted.  FIG. 5(   b ) is a diagram showing an image  500   b  where a downsized diagnostic data image  503   b  is displayed. 
           [0023]      FIG. 6(   a ) is a diagram of an example where the position of the region of interest moves from the initial position  604  to a position  602  in an image frame  600   a  so that the region of interest overlaps a diagnostic data image  603   a .  FIG. 6(   b ) is a diagram showing an image frame  600   b  where a diagnostic data image  603   b  is moved. 
           [0024]      FIG. 7(   a ) is a diagram of an example where an operator instructs via a user interface  106  to move a diagnostic data image from the initial position  704  in a noise region  701  to a position in the region of interest  702 .  FIG. 7(   b ) is a diagram showing a forcedly-moved diagnostic data image  703 . 
           [0025]      FIG. 8  is a flowchart illustrating the operation procedure of detecting a noise region. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    Hereinafter, an embodiment of an ultrasonic diagnostic apparatus of the present invention is described with reference to the attached drawings. 
         [0027]      FIG. 1  shows the exterior of the ultrasonic diagnostic apparatus  100  of the present embodiment. The ultrasonic diagnostic apparatus  100  displays in real time on a monitor  107  a tomographic image of an internal tissue which is produced using an ultrasonic probe  101 . In that case, an image which shows the diagnostic data of a subject, for example, is superimposed on an image frame of the tomographic image and displayed on the monitor  107 . Note that this “diagnostic data” comprehensively represents information about the subject and information about the diagnostic apparatus used and the diagnostic procedure. 
         [0028]    The ultrasonic diagnostic apparatus  100  of the present embodiment determines the display position of the image that shows the diagnostic data, or the like, according to a distinguishment result as to whether it is a region of the image frame in which a tomographic image of a tissue is present (region of interest) or the other region of the image frame which is exclusive of the region of interest (region of no interest), and superimposes the image on the image frame. More specifically, the ultrasonic diagnostic apparatus  100  superimposes an image which shows the diagnostic data, or the like, on the region of no interest of the image frame. 
         [0029]    In the description below, the configuration of the ultrasonic diagnostic apparatus  100  is first described, and then, how the ultrasonic diagnostic apparatus  100  specifies a region of no interest and in what manner an image which shows, for example, data about the subject is superimposed on the specified region of no interest are described in detail. 
         [0030]      FIG. 2  is a block diagram showing a configuration example of the ultrasonic diagnostic apparatus  100  of the present embodiment. 
         [0031]    The ultrasonic diagnostic apparatus  100  includes a probe  101 , an AD converter  102 , a beam former  103 , a wave detection section  104 , an image construction section  105 , a user interface  106 , a monitor  107 , and a processor  150 . 
         [0032]    The ultrasonic probe  101  transmits and receives an ultrasonic beam. During the operation of the ultrasonic diagnostic apparatus  100 , the ultrasonic probe  101  transmits an ultrasonic beam to a tissue of a biological body and receives a reflection wave of the ultrasonic beam from the tissue of the biological body. 
         [0033]    The AD converter  102  converts the received ultrasonic reflection wave to a digital signal. The beam former  103  performs delayed combination on the AD-converted ultrasonic reflection wave. The wave detection section  104  performs envelope detection on an ultrasonic echo signal obtained by the delayed combination. 
         [0034]    The image construction section  105  performs a signal process on a detected ultrasonic echo signal to construct a tomographic image frame of the tissue. 
         [0035]    The user interface  106  is an entry device, such as a keyboard, which is utilized by an operator for entering diagnostic data (e.g., data about a subject) or data other than the diagnostic data (non-diagnostic data). Note that the user interface  106  may be utilized when instructing whether or not data is displayed on the monitor  107  or when instructing a change of the display position of displayed data. For example, when the operator instructs a change of the display position of a diagnostic data image which will be described later, the user interface  106  may be utilized. 
         [0036]    The monitor  107  may be a display device in which, for example, a liquid crystal or a cathode ray tube is used, and which is configured to display an ultrasonic image and an image of the diagnostic data. 
         [0037]    Note that a touchscreen into which the user interface  106  and the monitor  107  are integrated may be provided. 
         [0038]    The processor  150  is a so-called central processing unit (CPU) and is configured to analyze an image frame of a tomographic image (ultrasonic image) and determine the display position of the diagnostic data and/or non-diagnostic data. 
         [0039]    The processor  150  includes an image analysis section  151  for analyzing an ultrasonic image, a diagnostic data image generation section  152  for generating an image of the diagnostic data, and an image synthesis section  153  for synthesizing the ultrasonic image and the diagnostic data. Each of these components may be configured by hardware or may be configured by software running on the processor  150  to carry out the function of the component. 
         [0040]    When the processor  150  is, for example, a special-purpose integrated circuit chip which is designed and manufactured exclusively for the ultrasonic diagnostic apparatus  100 , the image analysis section  151 , the diagnostic data image generation section  152  and the image synthesis section  153  are configured as independent integrated circuits in the processor  150 . 
         [0041]    When the processor  150  is a general-purpose integrated circuit chip, the image analysis section  151 , the diagnostic data image generation section  152  and the image synthesis section  153  are realized by the processor  150  and computer programs executed by the processor  150 . Specifically, suppose that there are library programs A, B and C provided for implementing the respective functions of the image analysis section  151 , the diagnostic data image generation section  152  and the image synthesis section  153 . During the execution of the library program A, the processor  150  functions as the image analysis section  151 . During the execution of the library program B, the processor  150  functions as the diagnostic data image generation section  152 . The same applies to the other program. Note that the processor  150  may execute the plurality of programs in parallel, so that the processor  150  seemingly concurrently operates as the image analysis section  151 , the diagnostic data image generation section  152  and the image synthesis section  153 . 
         [0042]    Next, an operation of the ultrasonic diagnostic apparatus  100  is described. 
         [0043]      FIG. 3  is a flowchart which illustrates the procedure in the ultrasonic diagnostic apparatus  100 . 
         [0044]    In step S 1 , the ultrasonic diagnostic apparatus  100  constructs an image frame of a tomographic image of an internal tissue with the use of an ultrasonic beam of the probe  101 . Specifically, the probe  101  transmits an ultrasonic beam into a biological body and receives a reflection wave of the ultrasonic beam from a tissue inside the biological body, for example. The AD converter  102  converts the received reflection wave of the ultrasonic beam to a digital signal. The beam former  103  performs a delayed combination process on the digital signal. The wave detection section  104  performs envelope detection to remove a transmitted wave (carrier) component from the received signal. The resultant signal is input to the image construction section  105 . The image construction section  105  performs a filtering process, a luminance conversion process, a scan line conversion (scan convert) process, etc., on the input ultrasonic echo signal to construct an ultrasonic tomographic image frame. The ultrasonic tomographic image frame is output to the processor  150 . The image frame is first input to the image analysis section  151  in the processor  150 . 
         [0045]    In step S 2 , the image analysis section  151  analyzes the tomographic image to distinguish a noise region in the image frame. The “noise region” means a region of the image frame which is exclusive of the region that includes the image of the internal tissue. In the specification of the present application, the noise region is referred to as “region of no interest”. Part of the image of the internal tissue which is utilized by an operator for diagnosis, or which is adopted as the basis for diagnosis, is referred to as “region of interest” or “non-noise region”. The process of distinguishing the noise region will be described later in detail with reference to  FIG. 8 . 
         [0046]    Then, in step S 3 , the diagnostic data image generation section  152  generates image data based on the diagnostic data entered via the user interface. 
         [0047]    First, the operator uses the user interface  106  to perform measurements of the image, etc., and enter the diagnostic data. The diagnostic data image generation section  152  converts the entered diagnostic data to image data. This process is, for example, conversion of the diagnostic data entered in the form of text data to an image object. The diagnostic data converted to an image object is hereinafter referred to as “diagnostic data image”. 
         [0048]    In step S 4 , the image synthesis section  153  generates a synthesized image by superimposing the diagnostic data image on the image frame (or synthesizing the diagnostic data image with the image frame) such that the diagnostic data image is displayed on the noise region (region of no interest) in the image frame. Determination as to whether or not the diagnostic data image is on the noise region in the image frame may be made based on whether or not, supposing that the diagnostic data image is rectangular, the entire area of the rectangular image is within the noise region  501 . 
         [0049]    In step S 5 , the monitor  107  displays the synthesized image.  FIG. 4  shows the synthesized image  400  displayed on the monitor  107 . The synthesized image  400  includes a noise region  401  and a non-noise region  402 . A diagnostic data image  403  is displayed in the noise-region  401 . 
         [0050]    When the diagnostic data image  403  is displayed on a region of no interest, the display position of the diagnostic data image  403  is preferably as close to a region of interest as possible. This is for the purpose of minimizing the movement of the sight line of the operator. For example, in the case where the blood vessel wall of the common carotid artery is observed and the intima-media thickness measured, the measured values are preferably displayed in part of the region of no interest which is close to the blood vessel wall. 
         [0051]    Thus, the image synthesis section  153  may generate a synthesized image such that the diagnostic data image is placed at such a position that the distance between the diagnostic data image and the region of interest is smaller than a predetermined threshold value. The operator can preset the threshold value in the image synthesis section  153  via the user interface  106 . The image synthesis section  153  holds the threshold value in, for example, an internal memory, and refers to the threshold value in determination of where on the region of no interest the diagnostic data image  403  is to be displayed. 
         [0052]    In the present embodiment, even after the above process is completed, the image analysis section  151  continues the process of distinguishing the noise region as described above as long as generation of ultrasonic images is continued. This is because the positions of the region of interest and the region of no interest may vary depending on, for example, the position of the probe  101 . The process performed in this phase will be described later with reference to  FIG. 6 . 
         [0053]    Hereinafter, a specific example is described. 
         [0054]      FIG. 5(   a ) shows an image  500   a  where the arrangement of a diagnostic data image  503   a  is not adjusted. In the image  500   a , the diagnostic data image  503   a  is displayed in a predetermined size at a predetermined position. As shown, part of the diagnostic data image  503   a  lies over the noise region  501  while the other part lies over a region of interest  502 . In this example, the diagnostic data region is unduly large so that it cannot be displayed without overlapping the region of interest. 
         [0055]    In that case, the image synthesis section  153  displays a diagnostic data image  503   b , which is a downsized version of the diagnostic data image  503   a , as shown in  FIG. 5(   b ). The image synthesis section  153  downsizes the diagnostic data image stepwise and determines, at every step of downsizing, whether or not the downsized diagnostic data image can be displayed within the noise region  501 . This determination is similar to the previously-described determination as to whether or not the diagnostic data image is present on the noise region in the image frame. If the diagnostic data image is rectangular, the determination may be made based on whether or not all the vertexes at the four corners of the rectangular image are in the noise region  501 . In this way, a synthesized image  500   b , in which the diagnostic data image  503   b  is placed on the noise region  501  that is different from the region of interest  502 , can be displayed. 
         [0056]      FIG. 6(   a ) shows an example where the position of the region of interest moves from the initial position  604  to a position  602  in an image frame  600   a  so that the region of interest overlaps a diagnostic data image  603   a . Such a move of the region of interest may occur due to, for example, a variation of the angle of the probe  101  or the posture of the body. 
         [0057]    In this situation, the image synthesis section  153  can automatically move the diagnostic data image  603   b  to a position shown in  FIG. 6(   b ). The image synthesis section  153  analyzes the image  600   a  after the move of the region of interest to distinguish a noise region  601  again. Then, the diagnostic data image may be superimposed on the image frame such that the diagnostic data image is displayed on the distinguished noise region. In this way, a synthesized image  600   b  shown in  FIG. 6(   b ) can be obtained. 
         [0058]    Also, the operator can move the display position of the diagnostic data using the user interface  106 .  FIG. 7(   a ) shows an example where the operator attempts to move the diagnostic data image from the initial position  704  in a noise region  701  to a position on the region of interest  702  via a user interface  106 . In such a situation, the image synthesis section  153  of the processor  501  can automatically (or “forcedly”) move the diagnostic data image to a position on the noise region  702  as shown in  FIG. 7(   b ). 
         [0059]    Next, a method of detecting a noise region, which is implemented by the image analysis section  151 , is described.  FIG. 8  is a flowchart illustrating the operation procedure of detecting a noise region. First, in step S 11 , the image analysis section  151  divides the image frame into small regions. In the subsequent step S 12 , the image analysis section  151  calculates the mean value and the variance value of the luminance of each of the small regions. In the specification of the present application, these physical quantities are also referred to as “image feature quantities”. 
         [0060]    In the subsequent step S 13 , the image analysis section  151  determines whether or not the mean value and the variance value of each of the small regions are smaller than threshold values THm and THv, respectively. The mean value and the variance value of the luminance of the noise component have a tendency to be smaller than those of the luminance of the biological body tissue component. Therefore, if the mean value and the variance value of each of the small regions are smaller than the predetermined threshold values THm and THv, respectively, the small region is estimated to be a noise region. On the other hand, if that condition is not met, the small region is estimated to be a non-noise region (region of interest). Therefore, by determination which is made based on the above criteria, it can be distinguished whether the small region is a noise region or a region of interest. Note that the size of the small region can be arbitrarily determined, although it is desirably equal to the size of the diagnostic data image generated by the diagnostic data image generation section  152 . Note that the threshold values THm and THv can be determined as a function of the mean luminance and the variance of the entire image. Note that the threshold values may vary depending on the noise level of the ultrasonic diagnostic apparatus  100 , the site which is to undergo diagnosis, and the parameters set by a user (such as dynamic range, transmission power, etc.) Therefore, appropriate values may be determined through adjustments on the ultrasonic diagnostic apparatus  100 . 
         [0061]    According to the above process, whether or not each of the small regions is a noise region can be determined based on the image feature quantities. By making the determination on every one of the small regions, the region of interest that includes an image corresponding to the internal tissue and the noise region can be distinguished with the accuracy which depends on the size of the small region. 
         [0062]    In this example, a noise region is detected as a region of no interest, although there is a region of no interest other than the noise region. Even in such a case, the region of no interest can be detected using a variety of methods other than the method illustrated in  FIG. 8 . For example, it is highly probable that part of the image which frequently moves is a region of interest, and therefore, a method of distinguishing a region of no interest from a region of interest by means of motion detection which is based on the frame correlation may be applicable. 
         [0063]    When the shape and the luminance pattern of the region of interest are specified beforehand, such as in the case of measurement of the intima-media thickness of the blood vessel wall of the common carotid artery, the image analysis section  151  may detect the region of interest by means of pattern matching, thereby distinguishing the region of interest and the region of no interest from each other. 
         [0064]    In this example, the tomographic image (B mode) is described, although the extent of the present invention is not limited to the B mode. As a matter of course, the present invention is applicable to typical ultrasonic images of other types, such as M mode, Doppler mode, etc. 
         [0065]    In the above-described embodiment, the user himself enters the diagnostic data using the user interface  106 . However, the “diagnostic data” is merely an example. For example, non-diagnostic data which is irrelevant to diagnosis (e.g., the name of the subject, the date of production of the tomographic image, etc.) may be entered. Further, the user interface  106  may not be used in entering the diagnostic data or non-diagnostic data. The diagnostic data or non-diagnostic data may be produced by the processor  150 . For example, the processor  150  may measure and display the thickness of the tissue in a tomographic image. 
         [0066]    The procedure which has been previously described using the flowchart shown in  FIG. 3  may be implemented in the form of a computer program which is executed by the image construction section  105  and the processor  150 . Such a computer program may be recorded in a storage medium, such as CD-ROM, which is to be circulated as a commercial product in the market, or may be distributed via electric communication lines, such as the Internet. Note that, the functions of the image construction section  105  may be realized by the processor  150  which executes computer programs, instead of providing the image construction section  105  as hardware. 
       INDUSTRIAL APPLICABILITY 
       [0067]    An ultrasonic diagnostic device of the present invention can display various diagnostic data concerning a body so as not to overlap a region of interest of an ultrasonic image and is therefore useful to, for example, medical applications. 
       REFERENCE SIGNS LIST 
       [0068]      101  probe 
         [0069]      102  AD converter 
         [0070]      103  beam former 
         [0071]      104  wave detection section 
         [0072]      105  image construction section 
         [0073]      106  user interface 
         [0074]      107  monitor 
         [0075]      150  processor 
         [0076]      151  image analysis section 
         [0077]      152  diagnostic data image generation section 
         [0078]      153  image synthesis section