JP7022404B2 - X-ray imaging device and image processing method in X-ray imaging - Google Patents

Description

The present invention relates to an X-ray imaging apparatus that obtains an X-ray image of a subject from X-ray transmission data collected by irradiating the subject with X-rays, and an image processing method in X-ray imaging, in particular. In addition to the X-ray image, an X-ray imaging device that acquires an optical image of the subject and displays the X-ray image and the optical image on top of each other to obtain a so-called fused image, and image processing in X-ray imaging. Regarding the method.

Conventionally, X-ray imaging devices such as panoramic radiography devices and dental X-ray CT devices are often used in dental practice and the like. As a result, an X-ray panoramic image or an X-ray CT image of the oral cavity can be obtained. By observing this image, the internal state of the teeth and gums can be interpreted.

This type of radiographer generally moves a pair of X-ray generator and detector around the subject, and during the movement, beam-shaped X-rays are sent to the X-ray generator at regular intervals. It has a configuration to irradiate the subject. Further, this X-ray imaging apparatus collects X-rays transmitted through the subject with a detector, and based on the X-ray transmission data obtained by the collection, the X-ray image is reconstructed by the tomosynthesis method, or CT is regenerated. It is configured to be reconstructed by a configuration algorithm.

In such an X-ray imaging apparatus, there is an example of a technique of superimposing an X-ray image generated as described above and an optical image of a subject's body surface on each other, that is, a technique of generating and displaying a so-called fusion image. It is known from Patent Document 1. Specifically, according to Patent Document 1, a video camera that captures a visible moving image of the body surface of a patient and a second that extracts position information of each part of the patient in a three-dimensional space based on the image output of the video camera. The X-ray image control means that controls the X-ray moving image of the patient in real time based on the output of the extraction means, the three-dimensional conversion means, and the second extraction means, and the patient output from the X-ray image control means. An image synthesizing means for synthesizing the X-ray moving image data and the body surface visible moving image data of the patient output from the video camera, and a composite image displaying means for displaying the moving image of the patient synthesized by the image synthesizing means. I have.

Further, as another example, the dental computed tomography (CT) apparatus described in Patent Document 2 is shown. The device includes X-ray imaging means, at least one color camera that photographs the patient's face located at the device's imaging station from multiple different directions, and the patient's face located at the imaging station. A means that is functionally connected to at least one color camera with at least one laser or corresponding lighting structure that is mounted to send light patterns to multiple different locations and is located at the imaging station. A means of creating a virtual 3D surface model from light pattern information sent to multiple different locations on the patient's face, as well as facial image information detected by at least one color camera and the patient's face. It includes a means of synthesizing a surface model to create a virtual three-dimensional texture model of a patient's face.

Further, Patent Document 3 exemplifies a dental practice system. According to this system, an X-ray output means that outputs X-rays toward the inside of a cavity, and a visualization imaging means that visualizes and photographs X-rays after the X-rays output by the X-ray output means have passed through a living body. It is provided with a display means for displaying the X-ray image taken by the visualization photographing means and the actual image corresponding to the imaging portion in parallel or superimposed.

As described above, Patent Documents 1 to 3 explain that a camera image and an X-ray image are fused and presented.

JP-A-2002-153458 (Claim 6 and the like) Special table 2013-518649 (summary, etc.) JP 2012-157683 (Claim 7 and the like)

For example, in order to find subtle changes such as whether periodontal disease has developed or how it progresses, not only the condition of the root inside the gums that can be judged from the X-ray panoramic image or X-ray CT image, but also the condition of the tooth root of the patient It is important to look at the condition of the teeth and gums, especially the change in gum color. In the conventional case, however, if there is a suspicious part in the X-ray image, it is necessary to actually visually confirm the condition of the teeth and gums. The reverse is also true. That is, the dentist needs to interpret the X-ray panoramic image and visually confirm the state (including the dental mirror), and the burden on the dentist for the interpretation is heavy. In addition, this also increases the burden on the patient, such as longer diagnosis / treatment time and longer mouth opening time.

Therefore, the present invention has been made in view of the situation faced when using the above-mentioned conventional X-ray apparatus, and in particular, a lesion in the oral cavity (occurrence of periodontal disease and its progress). An X-ray machine that can easily visually check the inner part of the dentition at the time of diagnosis, reduce the labor burden of the dentist, and reduce the burden of receiving treatment for the patient. It is an object of the present invention to provide an image processing method for radiography.

In order to achieve the above-mentioned object, according to the X-ray imaging apparatus according to one aspect of the present invention, an X-ray generator that generates X-rays and an X-ray generated from the X-ray generator are incident on the X-ray generator. A detector capable of outputting a digital amount of electric signals corresponding to incident X-rays at a constant frame rate for each pixel, the X-ray generator and the detector are held, and the oral cavity of the subject is sandwiched between them. The rotational movement mechanism that rotates and moves the pair of the X-ray generator and the detector so as to move around the oral cavity in a state of facing each other, and the rotational movement mechanism while the rotation movement mechanism is rotating and moving. The scan command means for controlling the X-ray generator and the detector to scan the oral cavity by the X-ray with the mouth of the oral cavity open, and the scan command means according to the scan command of the scan command means. An X-ray image generating means that generates an X-ray image (for example, a panoramic image) based on the electric signal output from the detector, and an X-ray image generating means that is arranged in a part of the rotational movement mechanism and is being driven during rotation of the rotational movement mechanism. An optical camera capable of taking a color optical image at a constant rate, and a color optical image for creating a color optical image from the optical image taken by the optical camera with the entire dentition inside the oral cavity in view. It is characterized by comprising a creating means and a fusion image creating means for creating a fusion image in which the X-ray image and the color optical image are positionally associated with each other and fused.

As a result, the color optical image creating means obtains a color optical image with the entire dentition in the oral cavity in view, so that the dentist can observe and treat the condition of the teeth and gums on the inner side of the dentition as much as possible. Can be known at once. This can reduce the time and effort of the subsequent dental mirror procedure, etc., reduce the labor burden of the dentist, and also reduce the burden of receiving treatment for the patient.

Here, the "color optical image of the oral cavity with the entire internal dentition in view" is "the entire gum and tooth alignment (dentition) having a standard horseshoe-shaped orbit shown by statistical data". A color image (which is also a real image seen by doctors, etc.) that attempts to optically photograph the surface. " The size of the gums and dentition varies between adults and children. Since there are individual differences in the shape of the dentition in the oral cavity, gums, missing teeth, etc., such a definition is required in the present invention.

In the attached drawing
FIG. 1 is a perspective view illustrating an outline of a panoramic image photographing apparatus as an X-ray photographing apparatus having a fusion function according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of a panoramic image capturing device. FIG. 3 is a diagram showing a projection trajectory of a standard tomographic plane set on the dentition on the XY plane. FIG. 4 is a diagram for explaining the movement of the plane set on the dentition from the standard fault plane on the XY plane. FIG. 5 is a diagram illustrating a concept of gain used for a panoramic image. FIG. 6 is a diagram showing an example of the geometric relationship between a color image captured by a camera that captures a color optical image (real image) and a feature point of an object in the imaging space (real space) of the panoramic image capturing device. Is. FIG. 7 is a flowchart showing a part of the process for specifying the position of the feature point reflected in the color optical image in the photographing space (real space) from the geometrical relationship illustrated in FIG. FIG. 8 is a flowchart showing another part of the process for specifying the position of the feature point reflected in the color optical image in the photographing space (real space) from the geometrical relationship illustrated in FIG. be. FIG. 9 is a flowchart showing still another part of the process for specifying the position of the feature point reflected in the color optical image in the photographing space (real space) from the geometrical relationship illustrated in FIG. Is. FIG. 10 is a diagram illustrating a flow of processing including a procedure for creating a fusion image in a panoramic image capturing apparatus together with a concept of an image. FIG. 11 is a photograph showing an example of an opening device to be inserted into the oral cavity of a subject (patient) at the time of photographing (the figure shows a state in which a therapeutic instrument is inserted). FIG. 12 is a photograph showing an example of the created fusion image. FIG. 13 is a diagram showing a modified example of the opening device.

Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the accompanying drawings.

First, an embodiment of the panoramic image capturing apparatus according to the present invention will be described with reference to FIGS. 1 to 12.

This panoramic image taking device is configured to scan X-rays and acquire a panoramic image of the oral cavity of the subject (patient) under the tomosynthesis method, and in parallel with this X-ray scan, the oral cavity of the subject. It is characterized in that it includes a configuration for capturing an optical image (surface image) of the above, and a configuration for obtaining a fusion image in which these captured panoramic images and optical images are fused (fused, integrated) with each other. That is, in the present embodiment, this panoramic image capturing device is configured as a composite device capable of obtaining an optical image.

The panoramic image is an image in which a curved oral cavity (gingiva, dentition, jawbone, etc.) is reconstructed as a two-dimensional image. Therefore, the optical image is also created as a two-dimensional image of the oral cavity. As will be described later, the fusion image is one image in which a panoramic image and an optical image are fused (fused). Specific embodiments of this fusion include a mode in which an optical image is superimposed (superimposed) on a part of a panoramic image, a mode in which a panoramic image is superimposed (superimposed) on a part of an optical image, and the like.

This fusion image is performed as parallel processing during scanning or post-processing after scanning. Therefore, the processing program for generating the fusion image may be integrated into the panoramic image capturing device, or a processing device such as a computer may be provided for exclusive use. In that case, it is desirable that the processing device is connected to the panoramic image capturing device so as to be able to communicate by wire or wirelessly in order to receive the collected data by scanning.

The purpose of obtaining this fusion image is that the doctor can simultaneously perform the interpretation of the X-ray transmission state and the visual observation of the state of the teeth and gums by viewing this image. Therefore, as an example, by observing this fusion image after interpreting the panoramic image, it is possible to observe the surface of the gingiva after interpreting the inside of the gingiva and the root, and by comparing the two. It is possible to know the state of the disease from multiple aspects. In particular, there is no problem with periodontal disease on an X-ray transmission image (panoramic image), but the onset of periodontal disease can be predicted from the color of the gingival surface on an optical image, and its use is great.

At this time, as will be described later, the dentist can take a panoramic image and a surface image only by operating the panoramic image taking device and performing scanning once, and can obtain the fusion image. For this reason, it is possible to reduce the trouble of opening the patient's mouth again after viewing the panoramic image and visually observing the surface of the teeth and gums with the dental mirror, as in the case of using a conventional panoramic image capturing device. can. This reduction in labor is a major factor in improving the efficiency of diagnosis and treatment.

From the viewpoint of visually observing the gums and the like with the naked eye, the optical image (surface image) is designed so that the entire dentition can be photographed as much as possible.

Therefore, the panoramic image capturing device (11) according to the present embodiment has, as its basic configuration, an X-ray generator (31, 31A) that generates X-rays and the X-rays, as can be seen from the detailed description described later. A detector (32) capable of incident X-rays generated from a generator and outputting a digital amount of electric signals corresponding to the incident X-rays at a constant frame rate for each pixel, the X-ray generator, and the above. A rotational movement mechanism that rotates and moves the X-ray generator and the pair of detectors so as to move around the oral cavity while holding the detector and facing each other across the oral cavity of the subject. (24) and. Further, the panoramic image capturing device (11) controls the X-ray generator and the detector to open the oral cavity and the mouth of the oral cavity while the rotational movement mechanism is rotating and moving. An X-ray image (for example, a panoramic image) is obtained based on the scan command unit (57) that scans based on the X-ray in the state of being in the state and the electric signal output from the detector in response to the scan command of the scan command unit. An optical camera that is arranged in a part of the rotation movement mechanism and an X-ray image generation unit (53, 56 (S54)) to be generated, and can take a color optical image at a constant rate while the rotation movement drive of the rotation movement mechanism is being driven. (91) and. Further, the panoramic image capturing apparatus (11) is a color optical image creating unit (11) that creates a color optical image from the optical image taken by the optical camera with the entire dentition inside the oral cavity as a field of view. 53, 56 (S51, S52, S53)) and a fusion image creating unit (56 (S55, S56)) that creates a fusion image in which the X-ray image and the color optical image are positionally associated with each other and fused. And.

Here, the "color optical image of the oral cavity with the entire dentition inside the oral cavity in view" means "the entire gum and dentition (dentition) along the standard horseshoe trajectory shown by the statistical data". A color image that attempts to capture the surface optically. " This color optical image corresponds to a real image (surface image) of the surface of a tooth or a dentition visually observed by a doctor or the like. The size of the gums and dentition varies between adults and children. Therefore, in the present embodiment, the shape of the dentition in the oral cavity, the gums, the omission of teeth, and the like vary from person to person, and such a definition is required. Of course, in the case of a patient with a dentition or oral cavity that deviates from such a standard horseshoe orbit, the doctor will treat each time individually, including the conventional method.

Hereinafter, the configuration, operation, and image processing of this composite type panoramic image capturing device will be described.

Among the panoramic image capturing devices according to the present embodiment, the configuration and operation relating to the acquisition of the panoramic image are the same as those of Japanese Patent Application Laid-Open No. 2007-136163 (Japanese Patent Application No. 2006-284593; Patent No. 4844886) already published by the applicant. be. Therefore, in the present application, the configuration and operation relating to the acquisition of such a panoramic image will be described only in outline. A configuration for capturing an optical image (surface image) and a configuration for generating a fusion image are integrally incorporated in this configuration and operation.

FIG. 1 shows an outline of the panoramic image capturing apparatus 1 according to this embodiment. As shown in the figure, the panoramic image capturing device 1 includes a housing 11 that collects gray level original image data for panoramic image generation from a subject (patient) P, for example, in a standing position. A computer that controls the collection of data performed by the housing 11, captures the collected data to generate a panoramic image, and interactively post-processes the panoramic image with an operator (doctor, engineer). It is provided with a control / calculation device 12 configured by.

The housing 11 includes a stand portion 13 and a photographing unit 14 that can move up and down with respect to the stand portion 13. As shown in FIG. 1, for convenience of explanation, an orthogonal coordinate system of X, Y, and Z axes with the longitudinal direction of the stand portion 13 as the Z axis is set.

The photographing unit 14 includes a vertically moving unit 23 that is substantially U-shaped when viewed from its side surface, and a rotating unit 24 that is rotatably supported by the vertically moving unit 23. The vertical movement unit 23 can be moved in the Z-axis direction (vertical direction) over a predetermined range in the height direction via a drive mechanism (not shown) installed inside the support column portion 22.

The rotation unit 24 is suspended from the vertical movement unit 23, and is urged by the drive of the rotation movement mechanism 30 to rotate. The rotating unit 24 has a substantially U-shaped shape when viewed from one side surface in the used state, and has a lateral arm 24A that rotates (rotates) in the lateral direction, that is, substantially parallel in the XY plane. The left and right vertical arms (first vertical arm, second vertical arm) 24B and 24C extending downward (Z-axis direction) from both ends of the horizontal arm 24A in the longitudinal direction are integrally provided. The rotation unit 24 is driven and operated under the control of the control / arithmetic unit 12. The rotation movement mechanism 30 is equipped with an encoder 30A that detects the position of the rotation angle.

The X-ray tube 31 and the detector 32 are equipped at the tips of the left and right vertical arms 24B and 24C, respectively. The X-ray tube 31 is, for example, a rotating anode type X-ray tube.

The detector 32 is, for example, an X-ray detector made of a semiconductor material such as CdTe (cadmium telluride), or a digital X-ray detector using an imaging plate. As an example, the detector 32 has an X-ray detection surface 32A (see FIG. 2) having a width of 6.4 mm and a length of 150 mm, and the detection surface has, for example, 64 × 1500 pixels composed of the above-mentioned X-ray detection element. It is formed. Thereby, incident X-rays can be collected as image data of a digital electric amount corresponding to the amount of the X-rays, for example, at a frame rate of 300 fps (1 frame is, for example, 64 × 1500 pixels). Hereinafter, this collected data is referred to as "frame data".

Further, in the vicinity of the detector 32 provided on one vertical arm 24C (for example, near the upper side), an optical camera 91 facing the shooting field of view and facing the other vertical arm 24B is provided. The optical camera 91 is, for example, a camera using a CMOS sensor, and as an example, the number of pixels is about 720 × 640, and the pixel size is about 50 μm × 50 μm. As will be described later, this optical camera 91 is for photographing the characteristic points of the dentition and the opening device of the oral cavity of the patient P in color. Therefore, the number of pixels and the pixel size may be different from the number of pixels and the pixel size as long as such shooting is possible. Of course, an optical camera using a CCD or the like as a shooting pixel may be used.

Further, in one of the vertical arms 24C, a lighting device 92 that irradiates the oral cavity of the patient P with the lighting light is provided. This is to brighten the inside of the oral cavity and take a clearer optical image in color.

FIG. 2 shows an electrical block diagram for controlling and processing the panoramic image capturing device.

As shown in the figure, the X-ray tube 31 is connected to the control / arithmetic unit 12 via the high voltage generator 41 and the communication line 42, and the detector 32 is connected to the control / arithmetic unit 12 via the communication line 43. ing. The high voltage generator 41 is provided in the support column portion 22, the vertical movement unit 23, or the rotary unit 24, and is exposed to X-rays such as a tube current and a tube voltage to the X-ray tube 31 by a control signal from the control / arithmetic unit 12. It is controlled according to the shooting conditions and the sequence of exposure timing. The X-ray tube 31 is provided with a slit 31A that limits the field of view of the X-rays to be irradiated.

The control / arithmetic unit 12 is configured by, for example, a personal computer capable of storing a large amount of image data in order to handle a large amount of image data, for example. That is, the control / arithmetic unit 12 is a main component thereof, and the interfaces 51, 52, 62, the buffer memory 53, and the first image memory 54 (storage) connected to each other so as to be communicable via the internal bus 50. Means), a second image memory 55, an image processor 56, a controller (CPU) 57, and a D / A converter 59. The controller 58 is communicably connected to the controller 57, and the D / A converter 59 is connected to the monitor 60.

Of these, the interfaces 51 and 52 are connected to the high voltage generator 41, the detector 32, the optical camera 91, and the lighting device 92, respectively, and the controller 57, the high voltage generator 41, and the detector 32 are connected to each other. It mediates the communication of control information and collected data exchanged between them. Further, another interface 62 connects the internal bus 50 and the communication line, and the controller 57 can communicate with an external device. As a result, the controller 57 can also capture the oral image taken by the external oral X-ray imaging device as needed, and also capture the panoramic image captured by the present imaging device and the focus-optimized image based on the image. For example, the DICOM (Digital Imaging and Communications in Medicine) standard allows it to be sent to an external server.

The buffer memory 53 temporarily stores the digital amount of frame data received from the detector 32 via the interface 52.

Further, the image processor 56 is placed under the control of the controller 57, and a panoramic image (X-ray image) of a standard tomographic plane along the dentition of the patient is generated (reconstructed), and a tooth to be imaged from a color optical image. Automatic detection of column feature points, creation of color optical images for fusion, fusion (fusion, composition, superimposition) processing of panoramic images and color optical images automatically or interactively with the operator Has the function of A program for realizing this function is stored in ROM 61 in advance.

In the present embodiment, the standard tomographic plane used for reconstructing the panoramic image is provided as a tomographic plane selected from standard tomographic planes of a plurality of sizes for adults, children, and the like prepared in advance. This standard fault plane is a virtual curved fault plane (a horseshoe-shaped fault plane when viewed from the vertical direction) set from statistical data on the shape and size of human dentition. FIG. 3 illustrates a selected standard fault plane for adults. Therefore, the teeth of the subject having the standard shape and size are aligned around this tomographic plane and along the curved plane thereof, so that the panoramic image of the standard tomographic plane itself is already the optimum focal image. However, in practice, individual subjects have dentitions that are wholly or locally offset from the standard tomographic plane.

Therefore, if the area of interest is out of focus in the panoramic image of the standard tomographic plane, which is the initial image to be reconstructed first, the optimum focus (in focus) is performed using the already collected frame data. ) Can be obtained. That is, there is no need to perform the scan again. As described above, the panoramic image capturing apparatus 1 of this embodiment adopts the configuration described in JP-A-2007-136163. Therefore, this second reconstruction can also be obtained only by reconstructing the frame data collected first and the gain (described later) according to a new desired cross-sectional position on the imaging space. As shown in FIG. 4, this new position may be a position where the fault plane to be focused is shifted from the position of the standard fault plane by a desired distance along the depth direction of the dentition, or the standard fault. On the image of the surface, it may be an oblique partial fault plane in which the region including the region of interest is moved in the depth direction of the dentition or rotated (tilted) around one axis of the region.

Returning to FIG. 2, the frame data and the image data processed or in the process of being processed by the image processor 56 are stored in the first image memory 54 so as to be readable and writable. For the first image memory 54, a large-capacity recording medium (nonvolatile and readable / writable) such as a hard disk is used. Further, the second image memory 55 is used to display the generated panoramic image data and / or the post-processed panoramic image data. The image data stored in the second image memory 55 is called by the D / A converter 59 at a predetermined cycle, converted into an analog signal, and displayed on the screen of the monitor 60.

The controller 57 controls the overall operation of the components of the device, including the drive commands of the optical camera 91 and the lighting device 92, according to a program stored in the ROM 61 that is responsible for the entire control and processing. Such a program interactively receives operation information about a predetermined item from an operator. Therefore, as will be described later, the controller 57 is responsible for generating a panoramic image of the standard tomographic surface and optimizing the focus of the panoramic image (that is, processing for further reducing image blur), and a parameter (gain) necessary for reconstruction. Or, it is possible to operate interactively by adding the setting of (called shift & add amount), the collection (scan) of frame data, and the operation information of the operator output from the operation device 58. Along with this scan, the optical camera 91 outputs the captured color image data at a constant rate. Since the optical camera 91 is attached to the rotation unit 24 for X-ray scanning, it is not necessary to rotate the optical camera 91 itself around the subject.

Therefore, as shown in FIG. 1, the patient holds the mouthpiece 26 with the jaw placed at the position of the chin rest 25 in a standing or sitting posture, and inserts a gag (see MS1 in FIG. 11). Press the forehead against the headrest 28 with the mouth open. As a result, the position of the patient's head (jaw) is fixed at substantially the center of the rotation space of the rotation unit 24. In this state, under the control of the controller 57, the rotation unit 24 rotates around the patient's head along the XY plane and / or along the plane oblique to the XY plane (see the arrow in FIG. 1). ..

During this rotation, under the control of the controller 57, the high voltage generator 41 applies a high voltage (specified tube voltage and tube current) for exposure, for example, in a pulse mode of a predetermined period to the X-ray tube 31. And drives the X-ray tube 31 in, for example, a pulse mode. As a result, pulsed X-rays are exposed from the X-ray tube 31 at predetermined intervals. Of course, the X-ray tube 31 may be driven in a continuous mode so that the X-rays are continuously irradiated.

The X-rays irradiated in this way pass through the jaw (dentition portion) of the patient located at the imaging position and are incident on the incident surface 32A of the detector 32. As described above, the detector 32 detects the incident X-rays at a very high frame rate (for example, 300 fps) and sequentially outputs them as frame data (for example, 64 × 1500 pixels) of the corresponding electric energy. This frame data is temporarily stored in the buffer memory 53 via the communication line 43 and the interface 52 of the control / arithmetic unit 12. The temporarily stored frame data is then transferred to and stored in the first image memory 54.

Therefore, the image processor 56 can generate a panoramic image along the standard tomographic plane along the dentition by reconstruction using the frame data stored in the first image memory 54. Further, the image processor 56 can generate a focus-optimized image by reconstruction using frame data forming a region of interest (ROI) designated on the panoramic image. The panoramic image itself is a cross-sectional image of the entire standard tomographic plane generated with the intention of optimizing the focus. However, in reality, due to the difference in the shape of the dentition of each subject, the standard tomographic plane alone has the least focus blur for each region (the focus is best within the range of the device's ability to exert). It is difficult to obtain an image (that is, the focus is optimized). Therefore, based on the panoramic image of the standard tomographic plane (at least the cross-sectional image covering the entire dentition), the reconstruction is performed to obtain a cross-sectional image showing the internal structure more clearly (less blurred and focused). To do. This post-processing reconstruction usually covers a portion of the underlying panoramic image. In the present embodiment, the cross-sectional image of this partial region is also regarded as a focus-optimized image.

The generation of a focus-optimized image including the base panoramic image thus involves a process called reconstruction. This reconstruction is performed by a process based on the tomosynthesis method. This tomosynthesis method is known, for example, from JP-A-2007-136163 described above, JP-A-4-1444548, etc., and simply corresponds to a plurality of frame data (two-dimensional mapping of pixel values) in a scanning direction. It is a process of shifting each other and superimposing and adding along the direction in which the data is applied. This superposition amount is called a gain (or shift & add amount) as described above. The shift-and-add process based on this gain emphasizes the pixel values of the tomographic plane at the desired position in the dentition depth direction (see FIG. 4), while blurring the pixel values of the other tomographic planes. As a result, a panoramic image of the tomographic surface at the desired position can be obtained.

The region of interest set on the panoramic image is usually designated on the panoramic image as a partial region forming a part of the panoramic image, but the entire panoramic image can also be set as the region of interest. Of course, a partially focused image is generated when a doctor or the like wants it.

The panoramic image and / or the partially focused image is stored in the first image memory 54 and displayed on the monitor 60 in an appropriate manner.

The shooting and interpretation of a panoramic image using the panoramic image capturing device 1 is roughly as described above. In this embodiment, the gain used to generate the panoramic image of the standard tomographic plane (this image is also a focus-optimized image) and the partial focus-optimized image of the specified region is referred to in JP-A-2007-136163 described above. As shown, it is set in advance by calibration using a phantom. This gain is an "amount indicating the degree of superposition", which is how much the frame data of each set is shifted and superposed. When this gain is small, the degree of superposition is dense, and when the gain is large, the degree of superposition is coarse.

An example of this gain will be described using the simplified model of FIG. In this model, the X-ray tube 31 and the detector 32 are distances D1 and D2 (respectively, a straight line connecting the X-ray tube and the detector at each point of the dentition) with respect to each other's object OB (dentition of the patient's jaw). It is assumed that the relative ratio of the direction (distance in the depth direction) along the line is kept constant and the relative operating speed is kept at a certain value to move. In this case, the amount (gain) of superimposition of frame data in which the object OB is not blurred or is less blurred (that is, in focus) is determined.

In other words, when scanned as described above, the focal plane (continuous cross section in focus) can be determined by the relative moving speed and gain of the X-rays to be scanned with respect to the subject. Since this focal plane corresponds to the ratio of the distances D1 and D2, the focal plane is located on the plane translated from the detector 32 in each depth direction.

In general, the smaller the gain, the closer the focal position is to the X-ray tube 31 in each depth direction Dpd, and the larger the gain, the farther the focal position is from the X-ray tube 31 in each depth direction Dpd. Therefore, how much gain should be set by using a phantom that quantitatively shows the distance between the X-ray tube 31 and the detector 32 in the depth direction orthogonal to the dentition at each position of the dentition? Quantitative measurement (setting) is performed in advance for each position on a straight line along each depth direction.

That is, the relationship between each position (each distance from the standard plane) and the gain is measured in advance using a phantom, and the relationship information is stored in, for example, the first image memory 54 as a look-up table LUT.

[Process to set the position of the feature point of the object from the color optical image]
Next, with reference to FIGS. 6 to 8, from the captured color optical image that forms part of the image processing performed by this panoramic image capturing device, the imaging space of the feature points of the dentition to be captured. The outline of the process of setting the position on (three-dimensional real space) will be described.

This process is executed by the image processor 56 immediately after the end of scanning or after data collection as post-processing after scanning.

FIG. 6 describes the geometrical relationship between the object OBJ that can be scanned by the panoramic image capturing apparatus 11 shown in _FIG . ₁ and the color optical images V1 and V2 captured by the optical camera 91. In the figure, an absolute coordinate system xyz based on, for example, a fixed portion of the panoramic image capturing apparatus 11 is shown. The z-axis direction corresponds to the vertical direction of the device 11.

The two color optical images V ₁ and V ₂ are actually two-dimensional images. The object OBJ abstractly simulates the dentition. The two color optical images V ₁ and V ₂ (hereinafter, the first optical image V ₁ and the second optical image V ₂ ) are rotated based on the detection signal of the encoder 30A (see FIG. 1). It is an image of the position of the rotation angle θ = θ ₁ and θ ₂ of the unit 24. These rotation angle positions are predetermined two positions during the panoramic shooting scan accompanying the rotation of the rotation unit 24, and are predetermined. Of course, this panoramic shooting scan is executed and processed in a three-dimensional space, but for ease of explanation, the schematic diagram of FIG. 6 is displayed in two dimensions as viewed from the z-axis (vertical axis) direction.

Now, the object OBJ has a feature region having a shape that can be easily distinguished from other parts, and the center point is assumed to be feature points OB ₁ , OB ₂ , and OB ₃ , and these feature points OB ₁ , OB. _2. OB ₃ shall be extracted from the first and second optical images V ₁ and V ₂ . This extraction process is executed by default by the image processor 56 under the control of the controller 57, as an example.

In the case of the principle diagram of the feature point position setting shown in FIG. 6, at the positions of the first and second optical images V ₁ and V ₂ , the first optical image V ₁ has the feature point OB ₁ of the object OBJ. , OB ₂ is reflected. However, since the third feature point OB ₃ is not in the field of view of the first optical image V ₁ , it is not captured. On the other hand, the second optical image V ₂ is an example in which all three feature points OB ₁ , OB ₂ , and OB ₃ are reflected. The distances between the first optical image V ₁ and the two feature points OB ₁ and OB ₂ are f ₁ and f ₂ , and the second optical image V 2 and the three feature points OB ₁ , OB ₂ and OB ₃ The distances to and from are f ₁ , f ₂ , and f ₃ .

The optical camera 91 captures a large number of color images at a constant rate in parallel with the X-ray scan, and stores the data in the first image memory 54 sequentially corresponding to the angle of rotation θ via the buffer memory 53. ing. Therefore, when the "process of setting the position of the feature point of the object" is instructed, the image processor 56 has the positions of the rotation angles θ = θ ₁ and θ ₂ stored in the first image memory 54. Read the color image data and process as follows.

First, the image processor 56 displays the _first optical image V1 on the monitor 60 as shown in FIG. 7 (step S10). Next, on the first optical image V ₁ , the position P ₁ B ₂ of the first feature point OB ₁ reflected therein is automatically confirmed and determined (step S11). This confirmation / determination is performed by a method such as processing the shape of the feature point OB ₁ by pattern recognition. Next, on the first optical image V ₁ , the position P ₁ B ₁ of the second feature point OB ₂ reflected therein is automatically confirmed and determined (step S12).

Next, the image processor 56 performs a focus processing of the position P ₁ B ₂ of the first feature point OB ₁ on the first optical image V1 by a known depth scan, and at the time of focusing the position P 1 B 2. The distance f ₁ is determined and stored (step S13). Further, on the first optical image V ₁ , the positions P ₁ B ₂ of the second feature point OB ₂ are similarly focused, and the distance f ₂ at the time of focusing is determined and stored (step S14). ..

Similarly, the image processor 56 displays the second optical image V ₂ on the monitor 60 (step S15). The positions of the two feature points OB ₁ and OB ₂ are confirmed on the second optical image V ₂ , and the positions P ₂ B ₁ and P ₂ B ₂ are confirmed and determined, respectively (steps S16 and S17). Further, on the second optical image V ₂ , the position P ₂ B ₃ of the third feature point OB ₃ is confirmed and determined (step S18). These confirmations / determinations are performed by a method such as threshold processing and pattern recognition for the shape of the feature point. Since the third feature point OB ₃ exists in the blind spot of the field of view of the optical camera 91 when the first optical image V ₁ is output, it is not reflected in the first optical image V ₁ , although it is not reflected in the first optical image V 1. Since it exists in the field of view of the optical camera 91 when the second optical image V ₂ is output, it is reflected in the second optical image V ₂ .

Further, the image processor 56 focuses the first feature point OB ₁ by a known depth scan, determines and stores the distance f5 at the time of focusing ₍ step S19). Further, the second feature point OB ₂ is similarly focused _, and the distance f3 at the time of focusing is determined and stored (step S20). Further, the third feature point OB ₃ is similarly focused, and the distance f4 at the time of focusing is determined and stored ₍ step S21).

Then, as shown in FIG. 8, the image processor 56 causes the monitor 60 to display the _first optical image V1 again, and on the image, the position P of the _first feature point OB1 reflected therein. ₁ B ₁ is calculated (step S31). Next, on the first optical image V ₁ , the position P ₁ B ₂ of the second feature point OB ₂ reflected therein is calculated (step S32).

Further, the image processor 56 causes the monitor 60 to display the second optical image V ₂ again, and calculates the position P ₂ B ₁ of the first feature point OB ₁ reflected therein on this image ( Step S33). Similarly, on the second optical image V ₂ , the position P ₂ B ₂ of the second feature point OB ₂ is calculated (step S34). Further, on the second optical image V ₂ , the position P ₂ B ₃ of the third feature point OB ₃ is calculated (S35).

Then, as shown in FIG. 9, the position of the first feature point OB ₁ in the two-dimensional space among the first to second feature points, that is, the position of one point on the surface of the object OBJ. Is calculated and stored from the geometrical relationship of the position P ₁ B ₂ , the distance f ₁ , the position P ₁ B ₂ , and the distance f ₅ obtained as described above (step S41). Further, the position of the second feature point OB ₂ in the two-dimensional space is calculated from the geometric relations of the positions P ₁ B ₁ , the distance f ₂ , the position P ₂ B ₂ , and the distance f ₃ obtained as described above. And memorize (step S42). Further, the position of the third feature point OB ₃ on the two-dimensional space is calculated and stored from the geometrical relationship of the position P ₂ B ₂ and the distance f ₄ obtained as described above (step S43).

As a result, the positions of the first, second and third feature points OB ₁ , OB ₂ and OB ₃ in the real space from the color image data taken by the optical camera 91, that is, the features of the surface of the object OBJ. The position of a specific part (point) is obtained. This position information in the real space is used to search for the corresponding position on the panoramic image as described later.

Therefore, as with the first, second, and third feature points OB ₁ , OB ₂ , and OB ₃ described above, the feature sites (points) found in the standard dentition of the patient's oral cavity are previously defaulted. You just have to have it. Of course, the doctor may interactively designate those characteristic sites (points) each time.

Further, although the positions of the rotation angles taken by the optical camera 91 are set to two places of θ = θ ₁ and θ ₂ , they may be three or more places depending on the number and positions of the designated feature points. For example, when viewed from the vertical direction (z-axis direction), there may be a total of three positions, that is, the position on the front side of the front tooth side of the dentition and the two positions on the side surfaces of the left and right molars. For these positions, the rotation angle command values θ = θ ₁₁ , θ ₁₂ and θ ₁₃ (see FIG. 10 described later) may be set as defaults according to the detection signal of the encoder 30A. Since the optical camera 91 outputs the color image data at a constant frame rate during the X-ray scan, the color image data taken at the positions of the rotation angles θ = θ ₁₁ , θ ₁₂ , and θ ₁₃ are read out. The first, second, and third optical images V ₁₁ , V ₁₂ , and V ₁₃ are obtained (see FIG. 10).

When each of the feature points specified on the object is reflected in the two optical images, the above-mentioned in-focus scan in the depth direction, so-called depth scan, becomes unnecessary.

[Example of creating a fusion image]
An example of creating a fusion image will be described.
The subject is subjected to an X-ray scan with the mouthpiece 26 inserted at the center of the anterior teeth (teeth 1 and 2) while inserting the opening device MSI illustrated in FIG. 11 to open the mouth. At this time, the optical photography by the optical camera 91 is executed in parallel with the panoramic photography by the X-ray scan as in the conventional case. Note that FIG. 11 is merely an example of a gag, and although a treatment device is used in the figure, such a treatment device is not used at the time of X-ray scanning.

FIG. 10 shows an outline of the creation of this fusion image. In this case, it is an example in which the above-mentioned depth scan is not used. Specifically, as shown in FIG. 10, the central portion of the unique shape formed by the cut between the left and right Nos. 1 and 2 on either the upper or lower side of the standard dentition, and the left and right No. 6 teeth. The feature points M _1L , _{M 1R} , _ML , and MR can be set by default in the central part of the peculiar surface shape formed on the outside. In this case, as shown in FIG. 10, three optical images V ₁₁ , V ₁₂ , and V are specified by designating the positions of the rotation angles θ = θ ₁₁ , θ ₁₂ , and θ ₁₃ so as to take these feature points into the field of view. ₁₃ can be obtained. In this case, in the case of a standard dentition, the feature points M _1L , _{M 1R} , _ML , and MR are reflected in the two optical images, respectively, so that depth scanning becomes unnecessary and the position and length of the optical image are simply obtained. From the relationship of distance, the positions of the feature points M _1L , _{M 1R} , _ML , and MR can be estimated in real space.

Specifically, the image processor 56 has three first to third optical images _V11 , _V12 , in which the four feature points M _1L , _{M 1R} , _ML , and MR of the dentition are reflected. As described above, the four feature points M _1L , M _1R , from each of the first to third optical images V ₁₁ , V ₁₂ , and V ₁₃ are collected from V ₁₃ (FIG. 10, step S51). The positions of _ML and _MR in the real space are specified (step S52). Next, the first to third optical images V ₁₁ , V ₁₂ , and V ₁₃ are connected based on the positions of the four feature points _{M 1L} , M _1R , _ML , and MR, and processing such as enlargement / reduction is performed (enlargement / reduction). Synthesis process: Step S53). As a result, one color optical image IM _OP is created.

On the other hand, the X-ray panoramic image IM _PA is reconstructed from the frame data output by the detector 32 (step S54). The X-ray panoramic image IM _PA may be an oral region image in which the oral region is partially cut out from the once reconstructed panoramic image and refocused by using a known method. Therefore, in the image processor 56, the positions of the four feature points M _1L , _{M 1R} , _ML , and MR of the color optical image IM _OP correspond to the positions on the X-ray panoramic image IM _PA , respectively, as described above. The search is performed based on the information on the positions of the feature points M _1L , _{M 1R} , _ML , and MR in the real space, that is, the marker positions of the dentition (step S55). As a result, as shown in FIG. 10, the positions (points) corresponding to the four feature points _{M 1L} , M _1R , _ML , and MR on the X-ray panoramic image IM _PA are M _1L ′, M _1R ′, M. _L ′ _{′ ′} and _MR ′ are set by the image processor 56.

Therefore, the image processor 56 matches these feature points M _1L , _{M 1R} , _ML , MR and their corresponding points M _1L ′, _{M 1R} ′, _ML ′ _′ , and MR ′ with each other, and appropriately reduces them. While enlarging, the color optical image of the dentition is _fused (superimposed and combined) with the color optical image of the dentition on the panoramic image IM _PA to create the fusion image IM _FU (step S56). Further, by this step 56, the fusion image IM _FU is displayed on the monitor 60.

FIG. 12 shows an example of the fusion image IM _FU actually created by this flow. In the fusion image IM _FU , an X-ray transmission image such as a jawbone is used as a background, and a color optical image IM _OP is superimposed on the dentition portion of the oral cavity.
This color optical image IM _OP can display the gums and dentition in color as much as possible to the inner end. Therefore, the dentist can judge from the surface state the color of the gums and the state of periodontal disease near the root of the tooth in the vicinity of the back teeth, in addition to the jawbone portion whose internal structure is shown at a gray level by simply absorbing X-rays. In this way, a color optical image is created from the optical image taken by the optical camera with the entire dentition inside the oral cavity as a visual field. For this reason, the color optical image IM _OP shows not only the vicinity of the anterior teeth of the dentition but also the surface image similar to the visual image in color as far as possible in the dentition, which not only reduces the time and effort for diagnosis but also diagnoses. Extremely effective as a tool. By observing this color optical image IM _OP , the dentist can greatly reduce the trouble of refitting the opening device MSI as shown in FIG. 11 and reviewing the back teeth and the vicinity of the gums with a dental mirror.

It is also possible to judge the extent of lesions and structural abnormalities by comparing the panoramic image IM _PA and the color optical image IM _OP .

In the above-described embodiment, the X-ray tube 31 and the slit 31A form a main part of the X-ray generator. The controller 57 corresponds to a scan command means (command unit) for commanding an X-ray scan. The buffer memory 53 and the image processor 56 (process S54 of the processor) form a main part of the X-ray image generation means (the generation unit). The buffer memory 53 and the image processor 56 (processes S51, S52, S53 of the processor) form a main part of the color optical image creating means (the processing unit). Further, the image processor 56 (processes S55 and S56 of the processor) forms a main part of the fusion image creating means (the processing unit). Further, the monitor 60 corresponds to a display means.

[Modification example]
A modification will be described with reference to FIG.
This variant relates to an example of a gag for allowing a color optical image to be reflected to the innermost teeth of the dentition. The gag M _OP shown in FIG. 13 is a color image including the reflection image of the mirror by placing a mirror in the oral vestibule (between the buccal mucosa and the dentition) while excluding the mouth fissure (upper and lower lips). It is an opening device M _OP configured to fit in the camera. As shown in FIG. 13 (A), the opening device includes flaps 101U and 101L that press the upper and lower lips, flaps 101L and 101R that press the left and right corners of the mouth, and an elastic connection 101C that connects these flaps. And prepare. In the figure, the reference numeral MS2 indicates the lips.

Further, the left and right flaps 101L and 101R are provided with mirrors 102L and 102R as shown in FIG. 13 (B). The mirrors 102L and 102R are located between the inside of the cheek FS and the back side of the dentition when the opening device _MOP is fitted in the mouth of the subject, and the optical reflection surface _MIR is located with respect to the dentition. It is designed to be located diagonally.

As a result, a gap SP is generated between the tooth and each of the mirrors 102L and 102R. Therefore, the reflected light of the illumination light reflected by each of the back teeth is reflected by the mirror 102L (102R) and goes outward from the opening portion. Therefore, the mirror images of the mirrors 102L and 102R are captured together by the optical camera 91 described above. Therefore, by appropriately processing the color image taken including this mirror image, the optical image can be surely taken to the deeper side of the dentition, so that the color optical image can be obtained over the entire dentition. The usefulness of the fusion image will be further enhanced.

Other modification examples will be described.

As another modification, not only the color optical image taken in parallel with the X-ray scan but also an existing or separately taken intraoral photograph (color photograph) may be fused to the panoramic image just taken.

Further, information on the dentition plaster model (three-dimensional morphological information, occlusal state information) may be taken in, and the data based on the information may be fused to the panoramic image and / color optical image described above.

Further, in the above-described embodiment, the fusion image may be displayed alone, or may be combined with the captured panoramic image and the color optical image and displayed on the monitor 60 by, for example, a screen division method. These images may be selected and displayed interactively with the operator.

Further, the optical camera 91 that captures a color optical image is not necessarily limited to a configuration in which a color image is output at a constant rate in parallel with an X-ray scan as described above. For example, based on the angle information from the encoder 30A, when the rotation angles θ = θ ₁₁ , θ ₁₂ and θ ₁₃ are reached, the shutter of the optical camera 91 is turned on to obtain only three color images in total. You may do so. As a result, the memory capacity on the device side can be reduced.

In the present embodiment, the dentition of the subject P has been described as being along a statistical standard trajectory, but there are individual differences, and the positions of the feature points (markers) of the dentition set by default are different. If it cannot be used, the doctor may manually specify the feature point each time. Thereby, the fusion image can be created according to the fusion algorithm described in the embodiment.

Further, the setting of the feature points is not limited to the case where the color optical image of the dentition is automatically recognized by processing such as pattern recognition, and the frame portion FRM of the opening device MSI illustrated in FIG. 11 is optically opaque. A plurality of, for example, punctate lead markers, which are preferably colored and whose X-ray transmittance is different from that of the tissue of the oral cavity, may be provided. Since this marker is also reflected in the color optical image and the X-ray panoramic image, a fusion image can be created based on the position in the same manner as described above.

As described above, the present invention can be implemented by incorporating various modifications or in collaboration with each other. Of course, the same applies to modifications other than those described above, as long as the gist of the invention is not deviated.

Claims (8)

X-ray generators (31, 31A) that generate X-rays and
A detector capable of outputting frame data consisting of a digital amount of electrical signals corresponding to the amount of X-rays generated from the X-ray generator through the subject and incident on each pixel at a constant frame rate. (32) and
The X-ray generator and the detector are held facing each other, and the oral cavity of the subject as the subject is positioned between the X-ray generator and the detector. A rotary movement mechanism (24) that rotates and moves a pair of an X-ray generator and the detector around the oral cavity, and
While rotating and moving the X-ray generator and the detector by the rotational movement mechanism, the X-ray generator and the X-ray generator so as to scan the oral cavity by the X-ray with the mouth of the oral cavity open. By controlling the detector, the scan command means (57) and
An X-ray image generation means (53, 56 (S54)) that generates an X-ray image based on the frame data output from the detector in response to a scan command of the scan command means.
An optical camera (91) arranged in a part of the rotational movement mechanism and capable of taking a color optical image of the oral cavity with the mouth open while the rotational movement mechanism is being driven at a constant rate.
A color optical image creating means (53, 56 (S51, S52, S53)) for creating a color optical image from the optical image taken by the optical camera with the entire dentition inside the oral cavity as a visual field. ,
A fusion image creating means (56 (S55, S56)) for creating a fusion image in which the X-ray image and the color optical image are positionally associated with each other and fused.
An X-ray imaging apparatus (11), characterized in that it is provided with. The X-ray image generation means is configured to create a panoramic image of the oral cavity as the X-ray image.
The color optical image creating means is configured to create an oral region image in which an oral region image is partially cut out from the color optical image in the oral cavity.
The first aspect of the present invention is characterized in that the fusion image creating means is configured to create an image in which the panoramic image is superposed on the panoramic image by positionally corresponding to each other as the oral region image. X-ray imaging device. The X-ray image generation means is configured to create a panoramic image of the oral cavity as the X-ray image and to create an oral region image in which the oral region is partially cut out from the panoramic image.
The fusion image creating means is configured to create an image in which the color optical image of the oral cavity is superimposed on the color optical image of the oral cavity by positionally corresponding the oral region images partially cut out from the panoramic image to each other. The X-ray imaging apparatus according to claim 1, wherein the X-ray imaging apparatus is used. The fusion image creating means causes the X-ray image and the color optical image to be previously reflected in the feature points extracted from the X-ray image and the color optical image, or in the X-ray image and the color optical image. The X-ray imaging apparatus according to any one of claims 1 to 3, wherein the fusion image is configured to correspond to each other with the markers as reference positions. The marker is a physical portion that is installed on a jig fitted to the oral cavity to open the mouth of the oral cavity and has a different X-ray transmission rate from the tissue of the oral cavity. The X-ray imaging apparatus according to claim 4, wherein the feature point is a portion showing a feature portion including a dentition of the oral cavity, which is extracted from the X-ray image. The color optical image creating means obtains the depth to the surface of the dentition of the oral cavity at a plurality of positions of the optical camera rotated by the rotational movement mechanism, and the depth is obtained from the data indicating the depth. It is configured to extract the characteristic points indicating the characteristic parts of the dentition.
The X-ray image generation means is configured to extract feature points corresponding to the feature points of the dentition from the X-ray image.
The X-ray imaging apparatus according to claim 4, wherein the fusion image creating means is configured to fuse the X-ray image and the color optical image with the feature point as a reference position. The X-ray imaging apparatus according to any one of claims 1 to 6, further comprising a display means for displaying the fusion image created by the fusion image creating means. An X-ray generator that generates X-rays and an X-ray generator
A detector capable of outputting frame data consisting of a digital amount of electrical signals corresponding to the amount of X-rays generated from the X-ray generator through the subject and incident on each pixel at a constant frame rate. When,
The X-ray generator and the detector are held facing each other, and the oral cavity of the subject as the subject is positioned between the X-ray generator and the detector. A rotary movement mechanism that rotates and moves a pair of an X-ray generator and the detector around the oral cavity, and
While rotating and moving the X-ray generator and the detector by the rotational movement mechanism, the X-ray generator and the X-ray generator so as to scan the oral cavity by the X-ray with the mouth of the oral cavity open. By controlling the detector, the scan command means and
An optical camera that is arranged in a part of the rotational movement mechanism and can take an optical image of the color of the oral cavity with the mouth open while the rotational movement mechanism is being driven at a constant rate.
In the image processing method in the X-ray imaging apparatus equipped with
An X-ray image is generated based on the frame data output from the detector in response to the scan of the scan command means.
From the optical image taken by the optical camera, a color optical image in which the entire dentition inside the oral cavity is taken into consideration is created.
To create a fusion image in which the X-ray image and the color optical image are positionally associated with each other and fused.
An image processing method characterized by being equipped with.

Images