Abstract:
The image processing device generates an operation image by adding or subtracting an original image and a standard deviation image which maps the standard deviation for the pixels configuring the original image. In this operation image, images of the structures seen in parts in the original image other than metal pieces are erased. Consequently, structures that are not metal pieces appearing in the original image in a whitish color, for example, do not appear in the operation image. If such an operation image is subjected to binarization processing in which the metal pieces appearing in a whitish color, for example, are extracted, since accurate graph cut processing is then possible, images originating from structures that are not metal pieces do not appear in the resulting image.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application refers to and claims priority as a national-phase of PCT/JP2013/003016 filed May 10, 2013 the entire contents of which are incorporated herein by reference. 
     FIGURE SELECTED FOR PUBLICATION 
     
       FIG. 1 
     
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image processing device to improve visual recognition of a radiation image, and particularly relates to the image processing device that can provide an image having high visual recognition despite incorporating an image of a metal piece into the radiation image.* 
     Technical Background 
     A medical facility equips the radiation device to obtain the subject&#39;s image using radiation. Such radiographic device comprises the image processing device to display an image having high visual recognition on the monitor by the addition of an image processing on the original image. 
     Some of the image processing devices can generate a tomographic image. According to such image processing device, when a plurality of original images that are continuously taken while changing the imaging direction are input, the original images are superimposed so as to output the tomographic image. A tomographic image is an image incorporating the image appearing when the subject is cross-sectionally imaged at a plan thereof. 
     Meantime, in the case of the subject who took a surgery to build up the bone with a metal piece in the past, an image of the metal piece is incorporated into the imaged original image. When the subject having the implanted metal piece inside body is imaged, the hardly radiation-transmissive metal piece is obviously incorporated into the original image. The metal piece on the original image appears as an extremely bright image on the original image. 
     The image processing device cannot generate the tomographic image having superior visual recognition by just simply superimposing the images incorporating the metal piece. Because a false image in the periphery of the metal piece incorporated into the generated tomographic image takes place. Then, according to the conventional image processing device, the tomographic image is generated by performing a separate image processing on the metal piece of the original image and other regions so as to prevent an occurrence of the false image in the tomographic image (e.g., see Patent Document 1, the entire contents of which are incorporated herein by reference). 
     A map capable of showing distribution of the metal piece in the original image is required so as to execute an image processing capable of reducing such false image. According to the conventional constitution, such map can be generated by executing a binarization processing on the original image. Provided the binarization processing is executed on the original image, an image as if in which an extremely dark metal piece incorporated into the original image is extracted can be obtained. The Otsu method can be applied to determine the threshold value relative to the binarization processing. 
     PRIOR ART DOCUMENTS 
     
         
         Patent Document 1: PCT/JP2012/003525 
         Non-Patent Document: Otsu N; A Threshold selection methods. IEEE from gray level histogram Trans. Systems Man, and Cybernetics 9: 62-66, 1979 
       
    
     ASPECTS AND SUMMARY OF INVENTION 
     Problems to be Solved by the Invention 
     However, there are following problems in the conventional constitution. Specifically, the binarization processing having the conventional constitution provides an inaccurate assignment of the metal piece. 
     According to the binarization processing relative to a conventional method, the metal piece cannot be extracted accurately. In some cases, more radiation absorptive cement is in-place in the periphery of the metal piece of the subject so that discrimination of the cement and the metal piece incorporated into the original image may be difficult when the binarization processing is performed. Accordingly, the conventional method for the binarization processing will include non-metal piece region in the metal piece region when the metal piece is extracted from the original image. This causes an erroneous recognition of the metal piece on the original image so that the tomographic image generation processing executed on the original image can be adversely impacted. 
     In addition, some original images have incorporated a fine whity component in the region other than the metal piece. In some cases, the binarization processing to extract the whity metal piece incorporated in the same original image may extract the fine component as well. Such erroneous extraction also provides an adverse impact on the generation processing of the tomographic image. 
     Under such circumstance, the present invention is completed and the purpose thereof is to provide an image processing device that can assuredly improve the visual recognition relative to a region other than a metal piece incorporated into the image by accurately discriminating the metal piece and other region&#39;s image relative to the image incorporating the metal piece. Means for solving the problem 
     The present invention comprises the following system to solve the above problem. Specifically, the image processing device of the present invention that is an image processing device that executes an image processing on an original image P 0  incorporating a metal piece obtained by radiation imaging of the subject having an implanted metal piece inside comprises; an image difference image generation means that is repeatedly operative to calculate the standard deviation of the pixel value of the attention pixel of the original image and the periphery of the attention pixel, an image calculation means that generates an calculation image by addition of the original image and the standard deviation image or subtraction of the standard deviation image from the original image, a calculation image binarization means that generates the binarization calculation image relative to the original image, a graph cut processing means that comprehends the distribution of the metal piece on the original image based on the binarization calculation image, obtains the representative value of pixel values of the region other than the metal piece of the original image and generates a map showing the distribution of the metal piece relative to the original image by executing the graph cut processing on the original image referring to each representative value. 
     Action and Effect 
     According to the composition of the present invention, the metal piece incorporated into the original image can be assuredly extracted based on the composition. That is, the standard deviation processing device that generates the standard deviation image in which the standard deviation is mapped relative to pixels constituting the image processing image of the present invention generates the standard deviation image in which the standard deviation is mapped relative to pixels constitution the original image, and then generates the calculation image by addition of the original image and the standard deviation image or subtraction of the standard deviation image from the original image, and further extracts the metal piece by the binarizing the calculation image thereof. In the certain calculation image, an image of the structure appearing in the region other than the metal piece of the original image is erased. Accordingly, the structure other than e.g. the metal piece incorporated whity on the original image will not appear in the calculation image. Accordingly, if the binarization processing capable of extracting e.g. the metal piece incorporated whity in the calculation image is added, an accurate graph cut processing can be performed so that an image originated in the structure other than the metal piece in the result image will never appear. 
     Further, the above image processing device preferably comprises; a metal piece cancel processing that generates a metal piece cancel image by canceling the metal piece incorporated into said original image from said original image referring to the extraction image, further wherein the metal piece is extracted from each original image continuously imaged while changing the imaging direction relative to the subject, a metal piece cancel tomographic image generation processing that generates metal piece cancel tomographic image by superimposing a plurality of the metal piece cancel image, a metal piece trimming processing that generates a trimming image by taking out the corresponding regions to the metal piece from the each original image referring to the extraction image, a metal piece tomographic image generation processing that generates metal piece tomographic image by superimposing a plurality of the trimming images, and a tomographic image generation means that executes the tomographic image adding processing so as to generate the synthetic tomographic image by adding the metal piece cancel tomographic image and the metal piece tomographic image. 
     Action and Effect 
     The image processing device of the present invention can be used for the case of generation of the tomographic image without occurrence of a false image in the periphery of the metal piece. 
     Further, the image processing device of the present invention may be mounted to a tomographic imaging device. 
     Effects of the Invention 
     The image processing device of the present invention generates the calculation image by addition or by subtraction relative to the original image and the standard deviation image in which the standard deviation is mapped relative to pixels constitution the original image. In the certain calculation image, an image of the structure appearing in the region other than the metal piece of the original image is erased. Accordingly, the structure other than e.g. the metal piece incorporated whity on the original image will not appear in the calculation image. Accordingly, if the binarization processing capable of extracting e.g. the metal piece incorporated whity in the calculation image is added, an accurate graph cut processing can be performed so that an image originated in the structure other than the metal piece in the result image will never appear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram illustrating the system of the image processing device of Embodiment 1. 
         FIG. 2  is a functional block diagram illustrating the system of the imaging device of the original image of Embodiment 1. 
         FIG. 3  is a schematic diagram illustrating an acquisition principle of the tomographic image of Embodiment 1. 
         FIGS. 4(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIG. 5  is a schematic diagram illustrating an operation of the image processing device of Embodiment 1. 
         FIG. 6  is a schematic diagram illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 7(A) ,(B),(C) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIG. 8  is a schematic diagram illustrating an operation of the image processing device of Embodiment 1. 
         FIG. 9  is a schematic diagram illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 10(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 11(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 12(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 13(A)  (B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 14(A)  (B)(C) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIG. 15  is a schematic diagram illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 16(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 17(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 18(A) ,(B) are schematic diagrams illustrating an operation of the image processing device of Embodiment 1. 
         FIGS. 19(A) ,(B) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
         FIGS. 20(A) ,(B),(C) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
         FIGS. 21(A)  (B) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
         FIGS. 22(A) ,(B),(C) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
         FIGS. 23(A) ,(B) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
         FIGS. 24(A) ,(B),(C) are schematic diagrams illustrating an operation of the tomographic image generation element of Embodiment 1. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The image processing device of the present invention is an image processing device that executes an image processing on an original image P 0  incorporating a metal piece obtained by radiation imaging of the subject having an implanted metal piece inside. Hereafter, the inventor illustrates the best modes of Embodiment of the present invention. 
     Embodiment 1 
     First, the inventor sets forth Embodiment of the image processing device  22 . Referring to  FIG. 1 , the system of the image processing device of the present invention outputs the map Ma showing the distribution of the metal piece incorporated into the original image P 0  when the original image P 0  is input. The original image P 0  can be a variety of images, but it is given that the original image P 0  is the image obtained by the X-ray radiography of the subject having an implant metal piece for the purpose of representing most effectively the characteristics of the present invention. And it is given that an image of the metal piece inside the subject is incorporated into the original image P 0 . Specifically, the original image P 0  in  FIG. 1  illustrates the metal piece m 0  constituting an artificial joint. 
     The image processing device  22  comprises each element  11 ,  12 ,  12 ,  13 ,  14 ,  15 ,  16  in order to generate the map Ma based on the original image P 0 . The standard deviation image generation element  11  generates the standard deviation image P 1  by executing the standard deviation filter on the original image P 0 . The image subtraction element  12  generates the subtraction image P 2  by subtracting the standard deviation image P 1  from the original image P 0 . The binarization element  13  generates the binarization subtraction image P 3  by executing the binarization processing relative to the subtraction image P 2 . The profile extraction element  14  generates the profile extraction image P 4  by extracting the profile of the binarization subtraction image P 3 . The snake processing element  15  recognizes the profile extracted in the profile extraction image P 4  as the initial state and executes a segmentation processing by the snake relative to the original image P 0  so as to generate the map Ma showing the distribution of the metal piece m 0  relative to the original image. The graph cut processing element  16  generates the map Ma showing the distribution of the metal piece m 0  relative to the original image based on the original image and the binarization subtraction image P 3 . The relationship between the operation in which the profile extraction element  14  and the snake processing element  15  are co-operative and the operation by the graph cut processing element is parallel. Relative the binarization subtraction image P 3 , the map Ma may be obtained by adding the image processing as to the snake processing or may be obtained by adding the image processing as to the graph cut processing. 
     The above standard deviation image generation element  11  corresponds to the standard deviation image generation means of the present invention and the image subtraction element  12  corresponds to the image calculation means of the present invention. Further, the above binarization element  13  corresponds to the binarization means of the present invention and the profile extraction element  14  corresponds to the profile extraction means of the present invention. Further, the snake processing element  15  corresponds to the snake processing means of the present invention and the graph cut processing element  16  corresponds to the graph cut processing means of the present invention. Further, the above subtraction image P 2  corresponds to the calculation image of the present invention. 
     A specific original image P 0  input into the image processing device  22  is a series of the X-ray images imaged by the tomosynthesis device. The image processing device  22  of the present invention is the device that can make the tomographic image clear which is generated by the tomosynthesis device. Here, the tomographic image that is incorporating an image obtained when the subject is sliced at a cross section is generated by using a radiographic device.  FIG. 2  is specifically illustrating such device. Referring to  FIG. 2 , the image processing device  22  comprises each element  11 ,  12 ,  13 ,  14 ,  15 ,  16  of  FIG. 1 . 
     The inventor sets forth Embodiment of the radiation tomographic device operable to generate a tomographic image of Embodiment 1. Further, X-ray of Embodiment is the radiation of the components of the present invention. Further, FPD (Flat Panel Detector) stands for Flat Panel X-ray Detector. The X-ray imaging device  50  of the present invention is for observation of artificial joint replacement surgery during the prognosis thereafter. 
       FIG. 2  is a functional block diagram illustrating the system of the X-ray imaging device  50  of Embodiment 1. Referring to  FIG. 2 , an X-ray imaging device  50  of Embodiment 1 comprises; a table  2  on which the subject M subjected to X-ray tomography is loaded, an X-ray tube  3  that is installed upper side of the table  2  (the first surface of the table  2 ) and radiates corn-like X-ray beam toward the subject M, a FPD  4  that is installed lower side of the table  2  (ground side of the table  2 ) and detects X-ray transmitting through the subject M, a synchronization move mechanism  7  that allows the X-ray tube  3  and the FPD  4  to make a synchronization move in the opposite direction each other while sandwiching the target region of the subject M under the condition in which the center axis of the cone-like X-ray beam always coincides with the center of the FPD  4 , a synchronization move control element  8  that controls the synchronization move mechanism  7 , and an X-ray grid  5  that absorbs the scattered X-ray set as covering the X-ray detection surface of the FPD  4  to detect X-ray. In this mode, the table  2  is in-place in the position sandwiched by the X-ray tube  3  and the FPD  4 . 
     The synchronization move mechanism  7  comprises the X-ray tube move mechanism  7   a  that moves the X-ray tube in the body axis direction A relative to the subject M and the FPD move mechanism  7   b  that moves the FPD  4  in the body axis direction A relative to the subject M. Further, the synchronization move control element  8  comprises the X-ray tube move control element  8   a  that controls the X-ray tube move mechanism  7   a  and the FPD move control element  8   b  that controls the FPD move mechanism  7   b . When the original image P 0  is continuously imaged, the synchronization move control element  8  moves the X-ray tube and the FPD  4  in the opposite direction each other. 
     The X-ray tube  3  radiates structure-wise cone-like pulse X-ray beam to the subject M repeatedly in accordance with control by the X-ray tube control element  6 . The collimater is attached to the X-ray tube  3  to collimate the X-ray beam to cone shape like a pyramid. And the X-ray tube  3  and the FPD  4  form the imaging system  3 ,  4  that images the X-ray projection image. The X-ray control element  6  controls the X-ray tube  3  according to the predetermined values specifying tube electric current, tube electric voltage and pulse width therefor and so forth. 
     The synchronization move mechanism  7  comprises a step of moving the X-ray tube and the FPD  4  in synchronization relative to the subject M. The synchronization move mechanism  7  moves straight the X-ray tube  3  along the straight line trajectory (longitudinal direction of the table  2 ) parallel to the body axis direction A of the subject M in accordance with control by the synchronization move control element  8 . The move directions of the X-ray tube  3  and the FPD  4  coincide with the longitudinal direction of the table  2 . In addition, during the examination, the cone-like X-ray beam radiated from the X-ray tube  3  is always radiated toward the target region of the subject M and the X-ray radiation angle thereof e.g. can be changed from the initial angle −20° till the final angle 20° by changing angle of the X-ray tube  3 . Such change of X-ray radiation angle can be conducted by the X-ray tube inclination mechanism  9 . The X-ray tube inclination control element  10  is installed so as to control the X-ray tube inclination mechanism  9 . 
     And the X-ray imaging device  50  of Embodiment 1 further comprises a main control element  25  that controls comprehensively each control element  6 ,  8 ,  10 ,  11 ,  12  and a display  27  that displays a tomographic image. The main control element  25  comprises a CPU and brings each control element  6 ,  8 ,  10  and each element  21 ,  22 ,  23 , set forth later, into reality by executing a variety of programs. The memory element  28  stores all data related to control of the X-ray imaging device, e.g. parameters related to the control of the X-ray tube  3 . The console  26  is used to input each operation relative to the X-ray imaging device  50  by the operator. 
     Further, the synchronization move mechanism  7  moves straight the FPD  4  installed under side of the table  2  in the straight line of the body axis direction A (longitudinal direction of the table  2 ) in synchronization of straight move of the X-ray tube  3  as set forth above. And the move direction is opposite direction to the move direction of the X-ray tube  3 . Specifically, the cone-like X-ray beam in changing the position of the focal point of the X-ray tube  3  and the radiation direction along with move of the X-ray tube  3  are structure-wise always received with all surfaces of the detection surface of the FPD 4 . Accordingly, the FPD  4  can receive e.g.  74  projection images while moving in the opposite direction relative to the X-ray tube  3  each other in synchronization during one examination. Specifically, referring to  FIG. 2 , the imaging systems  3 ,  4  move from the initial position illustrated as a solid line to the position illustrated as a dashed-line via the position illustrated as a broken line facing each other. Specifically, a plurality of X-ray projection images are taken while changing the positions of X-ray tube  3  and the FPD  4 . By the way, the cone-like X-ray beam always are received by all surfaces of the detection surface of the FPD  4  so that the center axis of the cone-like X-ray beam during imaging always coincides with the center point of the FPD  4 . Further, the center of the FPD  4  moves straight and such move is in the opposite direction relative to the move of the X-ray tube  3 . That is, it will be understood that the system moves the X-ray tube  3  and the FPD  4  in synchronization and in the opposite direction each other along the body axis direction A. 
     Principal of Acquisition of a Tomographic Image 
     Next, the inventor sets forth the principal of acquisition of a tomographic image of Embodiment 1. According to the system of Embodiment 1, the tomographic image can be generated by generating a plurality of the tomographic images that are images taken when the subject M is sliced on the plan.  FIG. 3  is a schematic diagram illustrating the acquisition method for the tomographic images taken by the X-ray imaging device of Embodiment 1. For example, referring to  FIG. 3 , as the virtual plan (the base slice section MA) parallel to the table  2  (horizontal relative to the perpendicular) is set forth, a series of the original images P 0  is generated by the image generation element  21  while the FPD  4  moves in synchronization in the opposite direction relative to the X-ray tube  3  according to the radiation direction of the cone-like X-ray beam from the X-ray tube  3  so that the points p, q in-place on the base slice section can be always projected to the fixed-points p, q on the X-ray detection surface of the FPD  4 . The projection images of the subject M are incorporated into the series of the original images P 0  while changing the position thereof. Then, providing the series of original images P 01  is reconstructed by the tomographic image generation element  23 , the images (e.g. fixed point p, q) in-place on the base slice section MA are accumulated and the X-ray tomographic image can be imaged. On the other hand, the point I in-place out of the base slice section MA is incorporated into the series of images of the subject M as a point i while changing the projection position on the FPD  4 . The point i, differently from the fixed points p, q, will not focus into an image and will be out of focus at the step of superimposing the X-ray projection images by the tomographic image generation element  23 . Accordingly, the series of projection images are superimposed so that the X-ray tomographic image incorporating only the image in-place on the base slice section MA of the subject M can be obtained. Accordingly, the projection images are simply superimposed so that the tomographic image on the base slice section MA can be obtained. The tomographic image generation element  23  corresponds to the tomographic image generation means of the present invention. The tomographic image generation element  23  corresponds to the tomographic image generation means of the present invention. 
     Further, the tomographic image generation element  23  can obtain the same tomographic image at any slice section horizontal to the base slice section MA. During imaging, the projection position of the point i relative to the FPD  4  moves but the move rate increases according to increasing distance between the point I before projection and the base slice surface MA. Based on this fact, if the obtained series of images of the subject M should be reconstructed while shifting to the body axis direction A at the predetermined pitch, the tomographic image at the slice section parallel to the base slice section MA can be obtained. Such reconstruction of a series of tomographic images can be executed by the tomographic image generation element  23 . 
     Operation of the Image Processing Device  22 : Operation of the Standard Deviation Image Generation Element  11   
     Next, the operation of the image processing device  22  is specifically set forth. Given the original image P 0  incorporating the metal piece m 0  is input to the image processing device  22 , the original image P 0  is input to the standard deviation image generation element  11  and then the standard deviation image P 1  is generated as illustrated in  FIGS. 4(A) ,(B). The standard deviation image P 1  is the image in which the standard deviation relative to pixels constituting the original image P 0  is mapped. The standard deviation is the measure of the dispersion used in statistics and specifically, the measure of the dispersion of pixel values of certain pixels constituting the original image and pixels in the periphery of pixels thereof. 
     The operation of the standard deviation image generation element  11  is set forth so as to generate the standard deviation image P 1 . Referring to  FIG. 5 , the standard deviation image generation element  11  specifies one of pixels constituting the original image P 0  as an attention pixel a. And the standard deviation image generation element  11  specifies e.g., a square region of 11 length by 11 width, having the attention pixel in the center thereof, as the attention region R. The attention region R should include the attention pixel a. The standard deviation image generation element  11  calculates these standard deviations by obtaining pixel values included in the attention region R from the original image P 0 . The certain calculated standard deviation is the value relative to the attention pixel a. In addition, for the convenience of drawing, the attention region R in  FIG. 5  is the square of 5 length by 5 width. 
     The standard deviation image generation element  11  specifies all pixels constituting the original image P 0  as the attention pixel a in order and calculates the standard deviation value every attention pixel a. Once the standard deviation image generation element  11  calculates the standard deviation values of all pixels constituting the original image P 0 , it conducts the mapping of standard deviation values. Specifically, the standard deviation image generation element  11  repeats the operation by which the standard deviation values are set in-place in the position of the attention pixel a upon calculation. Accordingly, all calculated standard deviation values are set in-place in one image. The calculated standard deviation values are pixel values in the standard deviation image P 1  obtained in such mode. The series of operations conducted by the standard deviation image generation element  11  can generate and present the standard deviation image P 1  by activating the standard deviation filter that specifies the calculation method for the attention region R and the standard deviation relative to each pixel constituting the original image P 0 . 
     The meaning of the standard deviation image P 1  generated in such mode is set forth. Referring to  FIG. 5 , the state when the standard deviation image generation element  11  set up a certain attention pixel a on the original image P 0  and the attention region R is illustrated. In this state, pixels having the similar pixel value exist in the periphery of the attention pixel a. The standard deviation of the attention pixel a tends to be a small value. 
     Also referring to  FIG. 6 , the state when the standard deviation image generation element  11  set up a certain attention pixel a on the original image P 0  and the attention region R is illustrated. The attention pixel a at this state is given as the position thereof is in the border between the metal piece m 0  and the other region relative to the original image P 0 . At this time, pixel values of the attention pixel a and the surrounding pixels thereof are dispersed. The standard deviation of the attention pixel a tends to be a high value. 
     Specifically, the region having a high pixel value corresponds to the region where pixel values relative to the original image P 0  are dispersed and the region having a small pixel value corresponds to the region where pixel values relative to the original image P 0  are similar. As the matter of fact, the standard deviation image P 1  provides the image in which the boundary region between the metal piece m 0  and the other region on the original image P 0  shows up as the high pixel value (referring to  FIG. 4(B) ). 
     Further, a bright spot s 0  is incorporated into the original image. The bright spot s 0  is obviously not belonging to the metal piece m 0  but it shows up brightly as well as the metal piece m 0  on the original image P 0 . The spot s 0  is a result in which the material other than the metal piece relative to the subject M, through which X-ray hardly transmits. The spot s 0  will be likely extracted together when the metal piece m 0  is being extracted from the original image P 0 . This kind of phenomenon should be prevented from an exact extraction standpoint as to the metal piece. 
     The inventor sets forth how the spot s 0  appears on the standard deviation image P 1 . The region corresponding to the spot s 0  on the standard deviation image P 1  shows up as a high pixel value as well as the metal piece m 0 . Because, the standard deviation value of pixels constituting the spot s 0  is high. The spot s 0  is the pixel showing up relative to the original image P 0 . Accordingly, the pixel constituting the spot s 0  is bright and relatively dark pixels are distributed in the surrounding region thereof. Accordingly, when the calculation of the standard deviation as to the spot s 0  is conducted, the high standard deviation value can be obtained because of the state as set forth referring to  FIG. 6 . 
     Operation of the Image Processing Device  22 : Operation of the Image Subtraction Element  12   
     The generated standard deviation image P 1  is input to the image subtraction element  12 . Referring to  FIGS. 7(A) ,(B), and (C), the image subtraction element  12  generates the subtraction image P 2  by subtracting the standard deviation image P 1  from the original image P 0 . 
     The inventor sets forth what the subtraction image P 2  is. Referring to  FIG. 7(C) , the subtraction image P 2  is incorporating the image as if darkly surrounding the bright metal piece m 0 . The inventor sets forth the rationale by which the subtraction image P 2  is in such mode. It is considered that when the standard deviation image P 1  is subtracted from the original image P 0 , how much the subtraction level is different from region to region of the original image. The high pixel value region and the low pixel value region are mixed in the original image P 1  so that the subtraction level for the original image may vary depending on the region of the image. The pixel of the original image P 0  corresponding to the region having the high pixel value relative to the standard deviation image P 1  will largely loose the pixel value thereof by the subtraction processing and the pixel of the original image P 0  corresponding to the region having the high pixel value relative to the standard deviation image P 1  will much less loose the pixel value thereof by the subtraction processing. 
     As set forth above, the region having the high pixel value relative to the standard deviation image P 1  is the boundary between the metal piece m 0  relative to the original image P 0  and the other region. Accordingly, when the subtraction processing is executed on the original image P 0 , the pixel value of the pixel in-place in the boundary region largely decreases so that the image of  FIG. 7(B)  may be provided. The subtraction image P 2  is the image as if of which the ambiguous pixels whether they are belonging to the metal piece in-place in the profile of the metal piece m 0  on the original image P 0  or not are painted with the dark pixel. 
     Next, it is considered that the bright spot s 0  in-place in the region other than the metal piece on the original image P 0  is how appears by the subtraction processing. A high pixel value is assigned to the corresponding region to the spot s 0  relative to the standard deviation image P 1 . Accordingly, when the standard deviation image P 1  is subtracted from the original image P 0 , the pixel value of the pixel constituting the spot s 0  will largely decrease. Accordingly, the image of the component appearing as the bright spot p 0  in the region other than the metal piece of the original image P 0  is erased and will not show up on the subtraction image P 2 . 
     [Operation of the Image Processing Device  22 : Operation of the Binarization Element  13 ] 
     The subtraction image P 2  is output to the binarization element  13  and the subtraction image P 2  is executed by the binarization processing. The inventor sets forth that the right region of the metal piece m 0  relative to the original image P 0  can be extracted by this mode.  FIG. 8  is a histogram, wherein the original image P 0  is developed by the pixel value. Two peaks including a peak derived from the metal piece m 0  and another peak derived from the region other than the metal piece appear in the original image P 0 . It is considered that the case in which the metal piece m 0  is being extracted from the original image P 0 . In this case, it seems better that the threshold between two peaks is set so that it can be found whether the pixel belongs to the metal piece m 0  or not on the basis of that whether the pixel value of the pixel constituting the original image P 0  is higher than the threshold value or not. 
     However, the pixels having intermediate value shown as the reference A are distributed between two peaks. Such pixels exist more in the boundary between the metal piece m 0  and the region other than that on the original image P 0 . If the threshold processing is conducted on the ambiguous region whether a metal or not, the judgment might be wrong. Specifically, the pixel even not belonging to the metal piece m 0  relative to the original image P 0  may be judged to be assigned to the metal piece m 0  or despite the pixel actually belonging to the metal piece m 0 , it may be judged as not to be assigned to the metal piece m 0 . Further, the bright spot s 0  appeared in the region other than the metal piece of the original image is belonging to the intermediate region shown as the reference A. When the original image is binarized, if the spot s 0  has a brighter pixel value than the threshold value, the spot s 0  may be wrongfully assigned to the metal piece. 
     Accordingly, in the constitution of Embodiment 1, when the metal piece m 0  is extracted, no threshold processing is directly executed on the original image P 0 .  FIG. 9  is a histogram of the subtraction image P 2 . Comparing to  FIG. 8 , it is noticeable that a number of pixels in the region A decreased. Because all pixel values of the ambiguous pixels surrounding the metal piece m 0  on the original image P 0  whether belonging to the metal piece and not or the pixels constituting the spot s 0  on the original image P 0  largely decrease and are grouped into the shaded region other than the metal piece in  FIG. 9 . 
     Referring to  FIGS. 10(A) , (B), the binarization element  13  generates the binarization subtraction image P 3  showing two regions including the region that is surely belonging to the metal piece m 0  relative to the original image P 0  and the ambiguous region belonging to either the metal piece or the non-metal piece by executing the threshold processing on the subtraction image P 2 . At this time, given the pixel value of the metal piece m 0  incorporated into the original image P 0  is known in advance, the threshold value employed by the binarization element  13  may be decided based on the pixel value thereof or may be decided by using Otsu method. Further, the binarization subtraction image P 3  corresponds to the binarization calculation image of the present invention. 
       FIGS. 11(A) , (B) is specifically illustrating the processing which the binarization element  13  executes on the subtraction image P 2  by taking out a region of the subtraction image P 2 . In the subtraction image P 2 , the dark belt-like region C is mixed in between the bright region incorporating the metal piece m 0  and the dark region represented by the reference n 0  which is not the metal piece m 0 . The belt-like region C is the region that corresponds to the region in-place in the profile of the metal piece m 0  incorporated into the original image P 0  and of which the pixel value drastically decreased by the image subtraction processing. When the binarization processing is executed on the subtraction image in this mode, the belt-like region C will not be incorporated into the region indicating a metal. Accordingly, the binarization element  13  divides the original image P 0  to the region that is surely belonging to the metal piece m 0  and the ambiguous region belonging to either the metal piece or the non-metal piece. 
     Operation of the Image Processing Device  22 : Confirmation of the Distribution of the Metal Piece m 0  Incorporated into the Original Image P 0   
     Accordingly, the generated binarization subtraction image P 3  is the image in which the metal piece m 0  is exactly taken out from the original image P 0  compared with the image for which the original image P 0  is simply binarized. However, there is a method that can perform further exactly the extraction of metal piece based on the binarization subtraction image P 3 . 
     Basically, the binarization subtraction image P 3  is the image of which the ambiguous region whether the metal piece or non-metal piece is counted as the non-metal region so that the distribution of the metal piece on the original image P 0  must be broader than the distribution of the binarization subtraction image P 3 . Therefore, the image processing device of Embodiment 1 executes the confirmation of the distribution of the metal piece m 0  incorporated into the original image P 0  using the binarization subtraction image P 3  by the subsequent image processing. Such image processing includes two methods, whichever is capable of extracting exactly the metal piece m 0  from the original image P 0 . Two methods include specifically the method utilizing the snake method and the graph cut method. The inventor sets forth two methods in order. 
     Operation of the Image Processing Device  22 : Operation of the Snake Method 
     First, the inventor sets forth the snake method. When this method is adopted, the binarization subtraction image P 3  ( FIGS. 12(A) , (B)) will be first sent to the profile extraction element  14 . Referring to  FIGS. 14(A) , (B), (C), the profile extraction element  14  generates the profile extraction image P 4  by executing the profile extraction processing on the binarization subtraction image P 3 . The profile extraction image P 4  is the image as if the silhouette of the metal region (the region assuredly belonging to the metal piece m 0  of the original image P 0 ) incorporated into the binarization subtraction image P 3  is traced by a pen. According to the profile extraction processing, the metal region of the binarization subtraction image P 3  appears on the profile extraction image P 4  as the ring drawn by closing the line having a constant line width. 
     The profile extraction image P 4  is sent to the snake processing element  15 . The snake processing element  15  analyzes the mode of the circular figure on the profile extraction image P 4  and then sets the node nd as a measure when the figure in  FIG. 13(A)  is deformed. Then, referring to  FIG. 13(B) , the snake processing element  15  decides the right profile of the metal piece m 0  relative to the original image P 0  while moving as if swinging the node nd. The snake processing element  15  is operative referring to the original image P 0 . The snake processing element  15  repeatedly reforms while applying a figure to the original image P 0  and looks for the suitable figure mode from the difference of pixel values between the pixel value of the pixel included in the figure of the original image P 0  and the pixel value of the non-included pixel while keeping the smooth mode. The snake processing element  15  recognizes the mode of the finally decided figure and binarizes so as to divide the inside region and the outside region of the figure. Then, referring to  FIG. 1 , the binarization image map Ma in which the metal piece m 0  is suitably extracted from the original image P 0  can be generated. 
     Operation of the Image Processing Device  22 : Operation of the Graph Cut Method 
     The image processing device can generate the map Ma by the different method from the above sanke method. Specifically, the image processing device  22  generates the map Ma by suitably extracting the metal piece m 0  from the original image P 0  based on the graph cut method. The binarization subtraction image P 3  is the beginning of the processing even by the graph cut method, 
     Given the graph cut method is adopted to generate the map Ma, the binarization subtraction image P 3  is sent out to the graph cut processing element  16 . Referring to  FIGS. 14(A) -(C), the graph cut processing element  16  obtains the representative value obj of the pixel value of the region corresponding to the metal piece m 0  relative to the original image P 0  based on the binarization subtraction image P 3 . The representative value obj is the most general pixel value relative to the metal piece m 0 . The region assuredly belonging to the metal piece m 0  relative to the original image P 0  is first set referring to the binarization subtraction image P 3  for the graph cut processing element  16  to calculate the representative value obj. Then, referring to  FIG. 15 , the graph cut processing element  16  performs the histogram analysis as to the certain region and obtains the pixel value most often appearing at the certain region. The pixel value obtained by this histogram is the representative value obj of the metal piece. 
     The graph cut processing element  16  obtains the representative value bg of the pixel value of the region corresponding to the region other than the metal piece m 0  relative to the original image P 0 . The representative value bg is the most general pixel value relative to the region other than metal piece m 0 . The region assuredly belonging to the region other than the metal piece m 0  relative to the original image P 0  is first set referring to the binarization subtraction image P 3  for the graph cut processing element  16  to calculate the representative value bg. Then, the graph cut processing element  16  performs the histogram analysis as to the certain region and obtains the pixel value most often appearing at the certain region. The pixel value obtained by this histogram is the representative value bg of the metal piece, 
     Then, the region corresponding to the region other than the metal piece m 0  in the binarization subtraction image P 3  includes the ambiguous region whether belonging to the metal piece or not relative to the original image P 0 . Accordingly, when the representative value bg is decided, it seems that the obtained representative value bg may deviate from the pixel value most frequently appeared in the region other than the metal piece m 0  by an impact of the pixel value of the ambiguous region. Assuredly, the histogram generated when the graph cut element  16  obtains the representative value bg includes the pixel of the ambiguous region. 
     However, the pixel value of the ambiguous region is basically similar to the pixel value of the metal piece and the pixel value of the ambiguous region, appearing in the histogram, is fewer compared to the pixels relative to the region other than the metal piece m 0 . Accordingly, the peak formed by the ambiguous pixels in the histogram is away from the main peak formed by the pixels of the region other than the metal piece m 0  and lower than the main peak. The graph cut element  16  obtains the representative value bg referring to the top of the main peak so that the pixel of the ambiguous region whether the metal piece or not may not be involved for the decision of the representative value bg. 
     The graph cut element  16  performs the graph curt processing on the original image P 0  based on the representative value obj and the representative value bg, and extracts exactly the distribution of the metal piece m 0  incorporated into the original image P 0 . The graph cut processed pixels are exactly assigned whether the pixel thereof belongs to the metal piece or the non-metal region. 
       FIGS. 16(A) ,(B) are illustrating the mode of a node n used for the graph cut method. It is given that the image comprises the pixel two dimensionally arrayed as illustrated in  FIG. 16(A) . The graph cut method interprets as the pixel a is a node n connected each other. Each node corresponds to each pixel a. Accordingly, nodes n are two dimensionally arrayed. Each node n that is two dimensionally arrayed is connected to the adjacent node n each other. The connected node n each other is closely related each other and make a lump. Then, the lump uniformly made of the entirety of image is dissolved into two lumps by disconnecting each node n one by one. Consequently, one of dissolved two lumps only comprises the node n corresponding to the pixel belonging to the metal piece. The other lump comprises only the node n corresponding to the pixel belonging to non-metal region. 
       FIGS. 17  (A), (B) are illustrating the first steps of the graph cut method. For ease of explanation, the inventor extracts the line of node n having the reference R 1  and sets forth. Firstly, two nodes na, nb are added in addition to the node n corresponding to the pixel a. The node na is a virtual node representing the pixel belonging to the metal piece. The node na is connected to all nodes n. The node nb is a virtual node representing the pixel belonging to the non-metal region. The node nb is also connected to all nodes n. 
     Next, the graph cut processing element  16  links the representative value obj to the node na and also links the representative value bg to the node nb. And next, the graph cut processing element  16  assigns the node n. For example, referring to  FIGS. 17(A) ,(B), the graph cut processing element  16  connects the node na having the same pixel value as the representative value obj among the nodes n to the node na. Further, also the node n 5  having the same pixel value as the representative value bg among the nodes n is connected to the node nb. 
     The node n 2  illustrated in  FIGS. 18  (A), (B) are the ambiguous pixel whether belonging to the metal piece or not. The graph cut processing element  16  notices the connection lines connected to the node n 2  when assigning the node n 2 . An evaluation value called cost is assigned to these lines. The graph cut processing element  16  divides the connection lines by comparing the costs. The cost is decided based on the pixel value of the pixel corresponding to the node n. Specifically, in the case of adjacent pixels having an similar pixel value, the cost of the connection line between nodes n corresponding to adjacent pixels is set as low. Then, in the case of the pixel value of a pixel, which is a value representing less X-ray exposure, the cost of the connection line between node n and the node na corresponding to the instant pixel will be set as low. Also, in the case of the pixel value of a pixel, which is a value representing a large X-ray exposure, the cost of the connection line between node n and the node nb corresponding to the instant pixel will be set as low. Accordingly, the low cost represents the close relationship between respective nodes. 
     The graph cut processing element  16  repeatedly divides the connection line while keeping the low cost connection lines. For example, referring to the embodiment of  FIGS. 18(A) ,(B), the node n 2  is disconnected from the node n on the right and the node nb and then the corresponding pixel a is judged as belonging to the metal piece. The graph cut element  16  executes such assignment as to the node n on all nodes n and generates the map Ma presented by the binarization image, which is representing the result of the assignment. The map Ma exactly represents the distribution of the metal piece relative to the original image P 0 . 
     Tomographic Image Generation Element 
     Next, the inventor sets forth the tomographic image generation element  23  by superimposing the original image P 0 . The tomographic image generation element  23  of Embodiment 1 refers not only to the original image P 0  but also to the above described map Ma on the operation thereof. According to the description as to the principal of the tomographic image generation referring to  FIG. 3 , the tomographic image can be generated if the tomographic image generation element  23  superimposes  74  original images P 0 . Accordingly, if only generation of tomographic image is expected, no generation of the map Ma by the image processing device  22  is needed. 
     However, if the original image P 0  should be simply superimposed, the tomographic image having a false image can be only obtained. Because each original image P 0  is incorporating the metal piece. The metal piece thereof cannot be fully obfuscated by superimposition of the original image P 0  because of the extreme pixel value. Accordingly, a residual image of the metal piece that cannot be completely canceled by superimposition of images may appear in the periphery of the metal piece of the tomographic image. The residual image thereof is the real identity of the false image appeared in the tomographic image. 
     The X-ray tomographic device of Embodiment 1 is a device in which such false image of the tomographic image would not take place. Specifically, the X-ray tomographic device of Embodiment 1 is the device in which no false image appears in the tomographic image by superimposing the metal piece based on the function of the image processing device  22 . Specifically, the tomographic image according to Embodiment 1 cannot be generated by superimposing as-is the original image P 0 . Specifically, referring to  FIGS. 19(A) ,(B), the tomographic image is generated by the tomographic image generation element  23  referring to the map Ma in which the metal piece is extracted from each of the original image P 0 . The map Ma is generated by that the image processing device  22  executes the extraction processing of the metal piece relative to each of 74 original images P 0 . Accordingly, 74 maps Ma will be generated 
     Operation of the Tomographic Image Generation Element  23 : Metal Piece Cancel Processing 
     The tomographic image generation element  23  generates the tomographic image referring to the map Ma generated by the image processing device  22 . The mode thereof is specifically set forth. First, the tomographic image generation element  23  executes the image processing so as to cancel the image of the metal piece incorporated into each of the original images P 0 . Specifically, referring to  FIGS. 20  (A), (B), (C), the tomographic image generation element  23  understands the position/size/range of the metal piece incorporated into the original image P 0  by referring to the map Ma. And the tomographic image generation element  23  converts the pixel value of pixels inside metal piece to the pixel value of pixels in the periphery of the metal piece. Then, the pixel value related to the conversion is e.g. an average value of pixels in the periphery of the metal piece. In such mode, the metal piece cancel image P 8  can be generated as if the metal piece incorporated into the original image P 0  is assimilated in the periphery. The metal piece cancel image P 8  is generated corresponding to each of 74 original images P 0 . Accordingly, the image processing device  23  performs the metal piece cancel processing, wherein a metal piece cancel image P 8  is generated by canceling the metal piece incorporated into the original image P 0  from the original image P 0 , referring to the map Ma in which the metal piece is extracted from each original image P 0  continuously imaged while changing the imaging direction relative to the subject M, 
     Operation of the Tomographic Image Generation Element  23 : Generation of the Metal Piece Cancel Tomographic Image 
     Referring to  FIGS. 21  (A),(B), the tomographic image generation element  23  generates the tomographic image by superimposing  74  metal piece cancel images P 8 . The image generated at this time is called as the metal piece cancel tomographic image D 1  for discrimination purpose. The metal piece cancel tomographic image D 1  is generated by superimposing the images as if the metal piece assimilated with the periphery of the metal piece so that no false image will appear in the periphery of the metal piece. However, the region corresponding to the metal piece illustrated in the inclination region of the metal piece cancel tomographic image D 1  in  FIGS. 21(A) ,(B) is completely filled up with incorrect pixel value. Because, the pixel value of the pixel inside the metal piece relative to the metal piece cancel image P 8  that is a base of the metal piece cancel tomographic image D 1  is converted to the pixel value different from the right pixel value. Hereafter, the tomographic image generation element  23  is operative to bring the pixel value of the metal piece region relative to the metal piece cancel tomographic image D 1  closer to the right pixel value. The tomographic image generation element  23  performs the metal piece cancel tomographic image generation processing that generates the metal piece cancel tomographic image D 1  by superimposing a plurality of the metal piece cancel image P 8 , 
     Operation of the Tomographic Image Generation Element  23 : Metal Piece Trimming Processing 
     Specifically, the tomographic image generation element  23  performs a different image processing on the  74  original images P 0 . Referring to  FIG. 22 , the tomographic image generation element  23  subtracts the corresponding metal piece cancel image P 8  from each of the original image P 0 . The original image P 0  and the metal piece cancel image P 8  have the same image as the region other than the metal piece so that the same regions are canceled and erased by the subtraction processing. Specifically, the trimming image P 9  is generated as if the region corresponding to the metal piece is trimmed from each of the original image P 0  by the subtraction processing with the tomographic image generation element  23 . The trimming image P 9  is more different than the above map Ma that might first be surmised similar. The map Ma is a binarization image and represents the aspect of the metal piece on the original image P 0  but, on the other hand, the trimming image P 9  represents not only the aspect of the metal piece but also light and shade inside the metal piece. Specifically, the metal piece of the trimming image P 9  looks like a thinner metal piece incorporated into the original image P 0 . Because, when respective images are subject to subtraction processing, the pixel value (pixel value of pixels in the periphery of the metal piece relative to the original image P 0 ) of the metal piece of the metal piece cancel image P 8  is subtracted from the pixel value of pixels on the metal piece of the original image P 0 . Accordingly, the tomographic image generation element  23  performs the metal piece trimming processing that generates a trimming image P 9  by taking out the corresponding regions to the metal piece from each of original image referring to the map Ma. 
     Operation of the Tomographic Image Generation Element  23 : Generation of Metal Piece Tomographic Image 
     Referring to  FIGS. 23(A) , (B), the tomographic image generation element  23  generates the tomographic image by superimposing  74  trimming images P 9 . The image generated at this time is called as the metal piece tomographic image D 2  for image discrimination purpose. The metal piece tomographic image D 2  is the tomographic image that shares the slice section with the metal piece cancel tomographic image D 1  Further, the metal piece tomographic image D 2  is generated by superimposing the image into which the only metal piece is incorporated so that the tomographic image of the metal piece can be incorporated. Accordingly, referring to  FIGS. 23(A) , (B), the region corresponding to the periphery of the metal piece, illustrated as the inclination region of the metal piece tomographic image D 2 , is not imaged at all. Accordingly, the tomographic image generation element  23  executes the metal piece tomographic image generation processing that generates the metal piece tomographic image D 2  by superimposing a plurality of the trimming image P 9 . 
     Operation of the Tomographic Image Generation Element  23 : Addition of the Tomographic Image 
     Accordingly, the tomographic image generation element  23  generates the tomographic images in two different systems. Referring to the last  FIGS. 24(A) , (B), the tomographic image generation element  23  performs the addition of the tomographic image D 1 , D 2  thereof. The image generated at this time is called as the synthetic tomographic image D 3  for image discrimination purpose. The synthetic tomographic image D 3  provides a superior visual recognition. Specifically, regions other than the metal piece of the synthetic tomographic image D 3  is originated in the metal piece trimming tomographic image D 1  so that no false image can appear. Then, the metal piece region of the synthetic tomographic image D 3  is originated in the metal piece tomographic image D 2  so that the reliability of the pixel value can be high. Accordingly, the tomographic image generation element  23  generates the synthetic tomographic image D 3  by adding the metal piece trimming tomographic image D 1  and the metal piece tomographic image D 2 . The synthetic tomographic image D 3  is displayed on the display  27  and then the operation of Embodiment 1 can be completed. 
     According to the composition of the present invention, the metal piece incorporated into the original image can be assuredly extracted based on the composition. That is, the image processing device  22  of the present invention generates the standard deviation image P 1  in which the standard deviation is mapped relative pixels constituting the original image, and then generates the subtraction image P 2  by addition or subtraction of the original image and the standard deviation image P 1 , and further extracts the metal piece by the binarization of the subtraction image thereof. In the certain subtraction image P 2 , the image of the structure appearing in the region other than the metal piece of the original image is erased. Accordingly, the structure other than e.g., the metal piece incorporated whity on the original image will not appear in the subtraction image. Accordingly, if the binarization processing capable of extracting e.g., the metal piece incorporated whity in the subtraction image P 2  is added, an accurate graph cut processing can be performed so that an image originated in the structure other than the metal piece in the result image will never appear. 
     The present invention is not limited to the above system and further following alternative Embodiment can be implemented. 
     (1) The above image processing device  22  having the image subtraction element  12  comprises the subtraction image P 2  by subtraction the standard deviation image P 1  from the original image P 0  because the metal piece m 0  is whity and shows up relative to the original image P 0  in the above Embodiment. Specifically, the above Embodiment is effective in the case of that the pixel of the metal piece m 0  relative to the original image P 0  has the high pixel value. 
     In the different case from the above Embodiment and the case of the metal piece m 0  showing up dark, the image addition element instead of the image subtraction element  12  can be more effective. The image addition element is the system that generates the addition image by addition of the original image P 0  and the standard deviation image P 1 . When the addition image is generated, the pixel value is added largely in the region near the profile of the metal piece m 0  of the original image P 0  and the region in which the dark structure other than the metal piece is incorporated. Accordingly, the addition image is the image in which the region that is surely the metal piece and the region other than the metal piece can be easily separated. Given the addition image is binarized, the same image as the binarization subtraction image P 3  set forth in Embodiment 1 can be obtained. 
     INDUSTRIAL APPLICABILITY 
     As set forth above, the image processing device of the present invention is suitable for medicinal field. 
     EXPLANATION OF REFERENCES 
     
         
         P Standard deviation image 
         P 2  Subtraction image (Calculation image) 
         P 3  Binarization subtraction image (Binarization calculation image) 
         P 4  Profile extraction image 
           11  Standard deviation image generation element (standard deviation image generation means) 
           12  Image subtraction element (Image calculation means) 
           13  Binarization element (Calculation image binarization means) 
           14  Profile extraction element (Profile extraction means) 
           15  Snake processing element (Snake processing means) 
           16  Graph cut processing element (Graph cut processing means) 
           23  Tomographic image generation element (Tomographic image generation means) 
       
    
     Having described at least one of the preferred embodiments of the present invention with reference to the accompanying drawings, it will be apparent to those skills that the invention is not limited to those precise embodiments, and that various modifications and variations can be made in the presently disclosed system without departing from the scope or spirit of the invention. Thus, it is intended that the present disclosure cover modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.