Abstract:
The present invention relates to a method and apparatus for detecting dental caries and an X-ray imaging apparatus and, more particularly, a method and apparatus for detecting dental caries and an X-ray imaging apparatus that can automatically detect occurrence and the degree of progress of caries by processing dental X-ray images.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2015-0081296, filed on Jun. 9, 2015. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a method and apparatus for detecting dental caries and an X-ray imaging apparatus and, more particularly, a method and apparatus for detecting dental caries and an X-ray imaging apparatus that can automatically detect occurrence and the degree of development of caries by processing dental X-ray images. 
         [0004]    Description of the Related Art 
         [0005]    Caries is a disease caused by breakdown of the hard tissues of teeth and bacteria are generally known as the cause. 
         [0006]    In Korea, 80% of population have caries, and the development is clinically divided into four stages: The first stage of caries is limited to the enamel of a tooth; it develops to the dentine in the second stage; it develops to the nerve in the third stage; and in the fourth stage, there is only a remnant tooth root left with the crown breaking down. 
         [0007]    In general, doctors detect caries by visually looking inside the mouth of a patient or checking dental X-ray images. 
         [0008]    That is, according to the method of detecting caries in the related art, since doctors visually check the inside of the patient&#39;s mouth, it takes long time to determine caries and objective determination may not be made, so there may be an error in the determination. 
         [0009]    Further, according to the method of detecting caries in the related art, doctors have to visually minutely check the inside of the patient&#39;s mouth even if the patient does not have caries, so there is difficulty in dental examination and treatment. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been made in an effort to solve the problems and an object of the present invention is to provide a method and apparatus for detecting dental caries and an X-ray imaging apparatus that can automatically detect occurrence and the degree of development of caries by processing dental X-ray images. 
         [0011]    Further, another object of the present invention is to provide a method and apparatus for detecting dental caries and an X-ray imaging apparatus that can automatically determine the degree of development of caries by detecting where caries occurs in a tooth. 
         [0012]    Further, another object of the present invention is to provide a method and apparatus for detecting dental caries and an X-ray imaging apparatus that can reduce a diagnosis time by raising an alarm, when a patient has caries. 
         [0013]    It should be noted that objects of the present invention are not limited to the above-mentioned object and other objects of the present invention will be apparent to those skilled in the art from the following descriptions. 
         [0014]    In order to achieve the above object, according to one aspect of the present invention, there is provided a method of detecting dental caries that detects whether caries has occurred by processing a dental X-ray image, the method including: segmenting teeth in a dental X-ray image and determining whether dental caries has occurred using image values of the segmented teeth. 
         [0015]    Further, according to another aspect of the present invention, there is provided an apparatus for detecting a dental caries in a dental X-ray image comprising: an input interface receiving image data of the dental X-ray image; a storage saving the image data and the dental X-ray image; and an image processor processing the dental X-ray image, segmenting the teeth and detecting the dental caries by image values of the teeth. 
         [0016]    Further, according to another aspect of the present invention, there is provided an apparatus of detecting dental caries that includes an input interface, a display, a storage, and an image processor and detects whether dental caries has occurred by processing a dental X-ray image, in which the image processor segments teeth in a dental X-ray image and determines whether dental caries has occurred using image values of the teeth. 
         [0017]    Further, according to another aspect of the present invention, there is provided an X-ray imaging apparatus including: an X-ray source radiating an X-ray to a patient&#39;s head including the patient&#39;s mouth; an X-ray sensor disposed opposite to the X-ray source and acquiring a dental X-ray image of the patient by receiving an X-ray passing through the patient&#39;s mouth; and an apparatus for detecting dental caries that segments teeth in the dental X-ray image and determines whether dental caries has occurred using image values of the segmented teeth. 
         [0018]    Further, according to another aspect of the present invention, there is provided an intraoral X-ray imaging apparatus including: an X-ray source radiating an X-ray to the mouth of a patient; an intraoral sensor inserted into the mouth and acquiring a dental X-ray image of a structure inside the mouth; and an apparatus for detecting dental caries that segments teeth in the dental X-ray image and determines whether dental caries has occurred using image values of the segmented teeth. 
         [0019]    The present invention has the following effects. First, according to the method and apparatus for detecting dental caries and the X-ray imaging apparatus of the present invention, it is possible to automatically detect dental caries by processing a dental X-ray image, so it is possible to considerably reduce the time taken to detect caries and it is also possible to obtain an objective result in caries detection. 
         [0020]    Further, according to the method and apparatus for detecting dental caries and the X-ray imaging apparatus of the present invention, by determining whether the dental caries occurs in enamel or dentine, it is possible to automatically determine the degree of development of caries in accordance with the position of caries. 
         [0021]    Further, according to the method and apparatus for detecting dental caries and the X-ray imaging apparatus of the present invention, when caries has occurred, it is possible to reduce diagnosis time by raising an alarm and it is also possible to prevent unnecessary diagnosis by showing the degree of development of caries by outputting different sounds or images for an alarm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
           [0023]      FIG. 1  is a view showing an X-ray imaging apparatus according to an embodiment of the present invention; 
           [0024]      FIG. 2  is a view showing an intraoral X-ray imaging apparatus according to an embodiment of the present invention; 
           [0025]      FIG. 3  is a block diagram of an apparatus for detecting dental caries according to an embodiment of the present invention; and 
           [0026]      FIG. 4  is a flowchart of a method of detecting dental caries according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Terminologies used herein have been selected from that are extensively and generally used at present, but the applicant(s) has freely selected some terminologies in specific cases, so, in this case, the meanings should be understood not just from the names, but in consideration of the meanings stated or described in the following detailed description. 
         [0028]    The technical configuration of the present invention is described hereafter in detail with reference to the embodiments shown in the accompanying drawings. 
         [0029]    However, the present invention is not limited to the embodiments described herein and may be achieved in other ways. Like reference numerals indicate the same components throughout the specification. 
         [0030]    Referring to  FIG. 1 , an X-ray imaging apparatus  100  according to an embodiment of the present invention includes an X-ray source  110  that radiates an X-ray to the head of a patient, an X-ray sensor that is disposed opposite to the X-ray source  110  and acquires a dental X-ray image from the X-ray passing through the head of a patient, and an dental caries detecting device  130  that detects dental caries of a patient by processing the dental X-ray image from the X-ray sensor  120 . 
         [0031]    Though not shown in the drawings, the X-ray imaging apparatus  100  according to an embodiment of the present invention may further include arms for supporting the X-ray source  110  and the X-ray sensor  120  and supports for supporting the arms on a floor or a wall. 
         [0032]    Further, the arms may be rotary arms so that the X-ray source  110  and the X-ray sensor  120  can rotate around the head of a patient. 
         [0033]    The dental caries detecting device  130 , which may be a computer system connected with the X-ray sensor  120  through a wire or a wireless network and which can collect and process information, is, in a broad sense, an image processing system including other smart devices or an embedded system specifically manufactured for the X-ray imaging apparatus  100  of the present invention. 
         [0034]    A dental caries detection program  131  for detecting dental caries  40  by processing the dental X-ray image may be embedded in the dental caries detecting device  130 . 
         [0035]    The dental caries detection program  131  may be provided in a recording medium independently from the X-ray imaging apparatus of the present invention, and the recording medium may be specifically designed for the present invention or may be common devices well known to those skilled in the art in the computer software field. For example, the recording medium may be a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape; an optical recording medium such as a CD and a DVD; a magnetic-optical recording medium for both magnetic and optical recording; or hardware devices that can keep and execute program commands independently or in combination with each other such as a ROM, a RAM, and a flash memory. 
         [0036]    The dental caries detection program  131  may be a program in which program commands, data files, and local data structure are configured independently or in combination with each other, or may be a program written by not only machine codes made by a compiler, but also high-class language codes that can be executed by a computer using an interpreter. 
         [0037]    The present invention may further provide a server system that can keep the dental caries detection program  131  and can transmit the dental caries detection program  131  to a client system such as the dental caries detecting device  130  through a network. 
         [0038]    That is, the dental caries detecting device  130  may download the dental caries detection program  131  from the server system and install it. 
         [0039]      FIG. 2  shows an intraoral X-ray imaging apparatus  200  according to an embodiment of the present invention, in which, as compared with the X-ray imaging apparatus  100  shown in  FIG. 1 , the X-ray source  110  is substantially separated from an X-ray sensor such as a portable X-ray generator and the X-ray sensor  120  is replaced with an intraoral sensor  210  that is put into the patient&#39;s mouth to take X-ray images of the inside of the mouth, and the other components are substantially the same. 
         [0040]    The X-ray source  110  may be directly carried by a worker or may be held on a wall etc. by an arm and the intraoral sensor  210  can acquire X-ray images of the intraoral structure between the X-ray source  110  and the intraoral sensor  210  by receiving X-rays from the X-ray source  110  outside the mouth. 
         [0041]    The X-ray source  110  and the X-ray sensor  120  shown in  FIG. 1  and the X-ray source  110  and the intraoral sensor  210  shown in  FIG. 2  may be modified in various ways, depending on the types of dental X-ray images to be acquired. For example, the X-ray source  110  and the X-ray sensor  120  shown in  FIG. 1  may be used to take panoramic X-ray images, while the X-ray source  110  and the intraoral sensor  210  shown in  FIG. 2  may be used to take X-ray images of teeth (two or three teeth) in a local area inside a mouth. 
         [0042]      FIG. 3  is a block diagram showing the dental caries detecting device  130  according to an embodiment of the present invention. As shown in  FIG. 2 , the dental caries detecting device  130  may include an input interface  140 , an image processor  150 , a storage  160 , and a display  170 . 
         [0043]    The input interface  140  may be a hardware and software module for inputting user instructions for processing images according to various embodiments of the present invention. The input interface  140  may be advantageously used to input various necessary instructions to the image processor  150 , input X-ray image data from the X-ray sensor  120  to the storage  160 , or indicate some or all of X-ray images displayed by the display  170  so that the images can be processed. For example, the input interface  140  may include a keyboard, a keypad, a touch pad, and a mouse for a computer, but is not limited thereto. For example, the input interface  140  may also include a graphic user interface that can be controlled using the input devices described above. 
         [0044]    The display  170 , which is provided to display images obtained in accordance with various embodiments of the present invention, may include various display devices such as an LCD display, an LED display, an AMOLED display, and a CRT display. 
         [0045]    The storage  160  may be used to keep X-ray images. The storage  160  may be used to keep image data obtained from a medium result in the process of processing images according to various embodiments of the present invention, resultant image data obtained by processing images according to various embodiments of the present invention, and variables required for processing images according to various embodiments of the present invention. In various embodiments, the storage  160  may keep various types of images described above in a DICOM (Digital Image Communications in Medicine) format or common image formats (BMP, JPEG, and TIFF etc.). The storage  160  may further keep software and firmware for configuring the image processor  150 . The storage  160  may be any one recording medium of a flash memory type, a hard disk type, an MMC (MultiMedia Card), a card type memory (for example, an SD (Secure Digital) card or an XD (eXtream Digital) card), a RAM(Random Access Memory), an SRAM(Static Random Access Memory), a ROM(Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a PROM (Programmable Read-Only Memory), a magnetic memory, a magnetic disk, and an optical disk, but those skilled in the art may understand that the storage  160  is not limited to these devices. 
         [0046]    The image processor  150  can detect dental caries  40  by reading out some of or the entire X-ray image data from the storage  160 , and for this purpose, the image processor  150  can segment teeth in an X-ray image and determine whether dental caries  40  occurs in the teeth using at least one image value selected from contrast and brightness of the teeth. In the embodiments, the brightness is selected as the image value. 
         [0047]    In particular, when an X-ray image is a panoramic X-ray image of an upper dentition  11  and a lower dentition  12 , the image processor  150  can detect the occlusal surface  13  between the upper dentition  11  and the lower dentition  12  and segment the teeth using normal vectors perpendicular to the occlusal surface  13 . Further, the image processor  150  can segment enamel  31  and dentine  32  of the segmented teeth and can determine whether the dental caries  40  occurs in the enamel  31  or the dentine  32  by image values of enamel  31  and dentine  32 . Further, with the information of the part where the dental caries occurs, the image processor  150  can determine the degree of development of dental caries, and when the image processor  150  determines that dental caries  40  has occurred, it can raise an alarm saying that dental caries  40  has occurred through a voice, a text or an image. To this end, the dental caries detecting device  130  according to an embodiment of the present invention may include a speaker for outputting a voice or a sound, or a display unit for outputting the text or the image. 
         [0048]    The image processor  150  may be achieved by using at least one of an ASIC (Application Specific Integrated Circuit), a DSPD (Digital Signal Processors DSP), a DSPD (Digital Signal Processing Device), a PLD (Programmable Logic Device), an FPGA (Field-Programmable Gate Array), a processor, a controller, a microcontroller, and a microprocessor. Further, the image processor  150  may be a firmware/software module that can be executed on the hardware platforms described above. In this case, the firmware/software module may be configured by one or more software applications written by an appropriate program language. 
         [0049]    A method of detecting dental caries  40  according to an embodiment of the present invention is described hereafter with reference to  FIGS. 1 to 4 . 
         [0050]    Referring to  FIG. 4 , the method of detecting dental caries  40  of the present invention is started from the X-ray imaging apparatus  100  or the intraoral X-ray imaging apparatus  200  according to embodiments of the present invention. 
         [0051]    First, dental X-ray images of a patient are obtained by the X-ray sensor  120  or the intraoral sensor  210  (S 1000 ), and the dental caries detecting device  130  receives the dental X-ray images  10  and  20  (S 2000 ). 
         [0052]    Further, the dental X-ray images that the dental caries detecting device  130  receives may be a panoramic X-ray image  10  or an intraoral X-ray image  20  and may be kept in the storage  160 . 
         [0053]    Next, the image processor  150  segments the teeth in the dental X-ray images. 
         [0054]    In order to segment the teeth in the dental X-ray images, a detection algorithm that uses contrast differences between the pixels in dental X-ray image data may be used. 
         [0055]    In order to segment the teeth in the dental X-ray images, a binarization algorithm which implements a thresholding method or a histogram-based method can be used. The thresholding method check a brightness of each pixel or representative brightness of adjacent pixels of an X-ray image by a threshold value T to give a white value (brightness=1) for values larger than T and a black (brightness=0) for values smaller than T. The histogram-based method (or an Otsu&#39;s method) makes a histogram on the basis of brightness of pixels in an X-ray image and finds a threshold value that can divide the histogram into two groups. The threshold value can be an optimum threshold value such that a distribution of the histogram in each group may be minimized and a distribution of the histogram between the groups may be maximized. 
         [0056]    Alternatively, in order to segment the teeth in the X-ray images, an SRG (Seeded Region Growing) algorithm can be implemented. With the SRG (Seeded Region Growing) method a seed which is a position of an area to be expanded in an X-ray image can be designated and an area can be expanded from the seed by comparing brightness using a predetermined reference. If a difference between a peripheral pixel and the seed pixel is below the predetermined reference, the area can be expanded. Or if the difference between the peripheral pixel and the seed pixel exceeds the predetermined reference, the expansion of the area can be stopped. For the expansion direction of the area, 4-connectivity for moving up, down, left, and right or 8-connectivity for moving the directions of 4-connectivity and diagonal directions of them may be used. 
         [0057]    Further, in order to segment the teeth in the X-ray images, a level-set technique may be used. With the level-set algorithm a curve can be advanced by iterating updates an initial contour of the curve and a contour converges to a boundary of a subject. 
         [0058]    Further, in order to segment the teeth in the X-ray images, an edge detection algorithm may be used. With the edge detection technique, a contour can be extracted by applying a Sobel-Mask, a Prewitt mask, a Robert mask, a canny mask, and a Laplacian mask to a dental X-ray image. 
         [0059]    On the other hand, when the dental X-ray image is the oral X-ray image  20 , there are two to three teeth in the image. So it is not that difficult to segment the teeth using a detection algorithm like the contrast of an X-ray image. But when the dental X-ray image is the panoramic X-ray image  10 , because all of the teeth of the upper dentition  11  and the lower dentition  12  are included in the image, it is difficult to segment the teeth. 
         [0060]    In the case that the dental X-ray image is the panoramic X-ray image  10 , the image processor  150  detects the occlusal surface  13  of the upper dentition  11  and the lower dentition  12  using a detection algorithm implementing differences in contrast (S 4100 ), and then segments the teeth in the upper dentition  11  and the lower dentition  12  using a boundary detection algorithm and normal vectors perpendicular to the occlusal surface  13  (S 4200 ). In this case, it is possible to considerably reduce the amount of calculation, so that the segmentation of the teeth can be done in real time. 
         [0061]    Further, though not shown in the drawings, a process of assigning an identifier to the segmented teeth may be performed. This is for a doctor to easily recognize where a segmented tooth should be placed. 
         [0062]    Next, the image processor  150  segments enamel  31  and dentine  32  in the segmented teeth  30  (S 5000 ). 
         [0063]    The detection algorithm and the image segmentation method using a difference in contrast of enamel  31  and dentine may be used to segment the enamel  31  and the dentine  32  without a limit. 
         [0064]    Next, the image processor  150  detects a dental caries  40  in the segmented enamel  31  and dentine  32  and then determines whether caries occurs. 
         [0065]    Further, in an image by the image processor  150 , a dental caries portion is darker than normal portions. So the image processor  150  can determine whether caries occurs using an image value (a brightness value) of a tooth. For example, when the average brightness of the enamel  31  or the dentine  32  is less than threshold brightness, or when the average brightness of one or more of sections which are divided from the enamel  31  or the dentine  32  is less than the threshold brightness, to the image processor  150  may determine that the dental caries  40  has occurred. 
         [0066]    Further, if the enamel  31  or the dentine  32  is divided into a plurality of sections and then the image processor  150  can find out where the dental caries  40  occurs. 
         [0067]    That is, a doctor can easily and quickly find out whether dental caries  40  occurs even though he or she cannot see the dental caries  40  directly. 
         [0068]    Next, the image processor  150  can further determine the degree of development at each portion where dental caries  40  has occurred (S 7000 ). 
         [0069]    For example, when dental caries  40  is detected only at the enamel  31 , the first stage of caries may be determined, and when the dental caries  40  is detected at both of the enamel  31  and the dentine  32 , the second stage of caries may be determined. 
         [0070]    Further, if the dental caries  40  is not detected at the enamel  31  but only detected at the dentine  32 , it can be determined that dental caries  40  has occurred at the lower portion of a tooth where the enamel  31  does not exist. 
         [0071]    Further, although it is exemplified to detect dental caries  40  at the enamel  31  and the dentine  32  in the present invention, it may be possible to further detect dental caries  40  in the nerve or the crown of a tooth, and in this case, it is possible to minutely divide and determine the dental caries  40 . 
         [0072]    Next, when it is determined that there is a dental caries  40 , the image processor  150  outputs the fact that the dental caries has occurred by a voice or an image for a doctor to recognize the fact (S 8000 ). 
         [0073]    To this end, the dental caries detecting device  130  of the present invention may further include a speaker other than the display  170 . Further, the alarm saying that dental caries  40  has occurred may be raised with different voices or images in accordance with the degree of development of dental caries  40 . It is possible to discriminate the degree of development of dental caries  40  by giving different melodies or volumes for the voice and giving different letters, colors, characters, symbols, and emoticons for the image. 
         [0074]    Accordingly, a doctor can simply and quickly recognize not only whether dental caries  40  has occurred, but also whether dental caries  40  is developed. 
         [0075]    Although preferable embodiments of the present invention were described above with reference to the drawings, they are not limited thereto and may be changed and modified by those skilled in the art without departing from the scope of the present invention.