Panorama x-ray tomographic image generation apparatus, panorama x-ray tomographic imaging apparatus, and program

Abstract

To acquires a panorama X-ray tomographic image with a large amount of information on a front tooth part.SOLUTION: A panorama X-ray tomographic image generation apparatus 7 includes: a frame image memory 31 for storing data on a large quantity of frame images acquired by an X-ray detector 3 by single panorama imaging; and a panorama X-ray image generation unit 60 for obtaining a route of an X-ray flux passing through a panorama tomographic image on a set tomographic plane using lamination thickness information, which is the information for designating the thickness of a pixel value of pixels integrated in the panorama tomographic image in a reference tomographic plane, inter-tomographic plane distance information indicating a distance between two adjacent tomographic planes including the reference tomographic plane, turning arm position relation information 42, and panorama tomographic position information 43, and integrating pixel values of pixels of a panorama tomographic image in other tomographic planes to the pixel value of the pixels of the panorama tomographic image in the reference tomographic plane on the basis of the route of the X-ray flux, an average value of the integrated pixel values being the pixel value of the pixels of the panorama tomographic image in the reference tomographic plane.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a panoramic X-ray tomographic image generation device, a panoramic X-ray tomographic imaging device, and a program, and particularly relates to a panoramic X-ray tomographic image generation device, a panoramic X-ray tomographic imaging device, and a program for dental use.

Background Art

[0002] During dental treatment, panoramic X-ray tomography is performed to comprehensively examine the condition of a patient's teeth (dentition). The panoramic X-ray tomography method is an application of the rotational tomography method, in which the rotation center position is moved in accordance with the dentition shape (dental arch), and an X-ray imaging method that covers the maxillary sinus, temporomandibular joint, dentition, and chin. Conventional panoramic X-ray tomographic imaging devices are premised on acquiring X-ray tomographic images of a predetermined standard dentition. Therefore, when the dentition of a patient as a subject does not match the standard dentition, there is a problem that the X-ray tomographic image is out of focus and blurred. In addition, due to the nature of the panoramic X-ray tomography method, the anterior tooth part has a smaller rotation radius than the molar part. That is, particularly in the anterior tooth part, the distance between the rotation center position of the panoramic X-ray imaging device and the tomogram that captures the subject is short. Therefore, due to the principle of rotational tomography, the tomographic region of the anterior tooth part becomes thin, making it more difficult to position the patient with better focus.

[0003] Therefore, in recent years, panoramic X-ray tomographic imaging devices equipped with a function that can change the position of the tomogram from the position of the standard tomogram (hereinafter referred to as the variable tomogram function) have been developed. A panoramic X-ray tomographic imaging device equipped with a variable tomogram function uses an X-ray detector capable of acquiring frame image data at high speed, and by changing the shift amount and adding (overlaying) the frame image data obtained in a single shot, an X-ray tomographic image at an arbitrary depth can be obtained. Conventionally, a panoramic X-ray tomographic imaging device equipped with an autofocus function that applies this variable tomogram function has also been known (see Patent Document 1). This autofocus function uses the frame image data obtained in a single shot to generate a plurality of X-ray tomographic images with different shift amounts, and automatically extracts the tomographic plane with the best focus on the dentition of the subject through frequency analysis processing. Conventionally, there has also been known a panoramic X-ray tomographic imaging device equipped with a function of obtaining a panoramic X-ray tomographic image corresponding to an image on a tomographic plane cut obliquely in accordance with the inclination of the anterior teeth, with the problem that the tomographic area is thin in the anterior tooth region (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In panoramic X-ray tomography, since the tomographic region is thin in the anterior tooth part, the images of the anterior tooth part have characteristics different from those of the molar part where the tomographic region is originally thick. Human anterior teeth generally incline in the anteroposterior direction of the head. Due to the thin tomographic region in the anterior tooth part, it has been difficult to simultaneously capture the enamel and the root tip in the X-ray tomographic image when focusing on one anterior tooth, or to simultaneously capture the upper anterior teeth and the lower anterior teeth in the X-ray tomographic image. Also, the thin tomographic region in the anterior tooth part causes difficulties in patient positioning in the anteroposterior direction. These problems have not been solved until now, and factors such as an increase in the patient's radiation dose, such as the need to re-take pictures of the anterior tooth part separately by dental imaging, and factors that hinder smooth medical treatment have occurred.

[0006] Even if the technologies described in Patent Documents 1 and 2 are used, the tomographic region in the anterior tooth part remains thin. That is, in a conventional panoramic X-ray tomographic apparatus, the anterior tooth part does not appear in the image for regions deviated from the set tomographic positions such as the standard tomographic position, and the obtained images of the anterior tooth part are images related to only one tomographic position set in the thin tomographic region, and currently, the images have a small amount of information on the anterior tooth part.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a panoramic X-ray tomographic image generation apparatus, a panoramic X-ray tomographic apparatus, and a program capable of acquiring a panoramic X-ray tomographic image with a large amount of information on the anterior tooth part.

Means for Solving the Problems

[0008] In order to solve the above problems, a panoramic X-ray tomographic image generation apparatus according to the present invention generates a panoramic X-ray tomographic image on a tomographic plane set at an arbitrary depth in a subject based on a number of frame image data obtained by a single panoramic photographing in which a fan-shaped X-ray beam is irradiated onto the subject. The panoramic X-ray tomographic image generation apparatus includes a main storage unit that stores swing arm position relationship information including the position coordinates of the rotation center for each swing angle of the swing arm during panoramic photographing and panoramic tomographic position information that is the position information of a reference tomographic plane in the panoramic tomographic image, a frame image storage unit that stores a number of frame image data acquired by an X-ray detector in a single panoramic photographing, stacking thickness information that is information specifying the thickness of the pixel value of a pixel to be integrated into the panoramic tomographic image on the reference tomographic plane, inter-slice distance information indicating the distance between two adjacent tomographic planes including the reference tomographic plane, a panoramic X-ray image generation unit that obtains the path of the X-ray beam passing through the panoramic tomographic image on the set tomographic plane using the swing arm position relationship information, the panoramic tomographic position information, integrates the pixel values of the pixels of the panoramic tomographic image on other tomographic planes into the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane based on the path of the X-ray beam, and sets the average value of the integrated pixel values as the pixel value of the pixel of the panoramic tomographic image on the reference tomographic plane.

[0009] According to such a configuration, the panoramic X-ray tomographic image generation apparatus integrates and averages the pixel values of the pixels of the panoramic tomographic image on other tomographic planes into the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane using the input stacking thickness information and inter-slice distance information and the stored swing arm position relationship information and panoramic tomographic position information, so that the tomographic region of the anterior teeth can be thickened. In addition, instead of simply integrating the pixel values of the pixels of the panoramic tomographic image on other tomographic planes into the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane, the integration is performed for each path of the fan-shaped X-ray beam and averaged, so that the obtained panoramic X-ray tomographic image accurately reflects the internal information of the subject and has a larger amount of information on the anterior teeth than in the prior art. Note that the present invention can also be realized by a program for causing a computer to function as the panoramic X-ray tomographic imaging apparatus described above.

Advantages of the Invention

[0010] According to the present invention, a panoramic X-ray tomographic image with a large amount of information on the anterior teeth can be obtained.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0012] A mode for carrying out the panoramic X-ray tomographic image generation apparatus and the panoramic X-ray tomographic imaging apparatus according to the present invention will be described in detail with reference to the drawings. Note that the sizes and positional relationships of the members shown in the respective drawings may be exaggerated for clarity of explanation.

[0013] (First Embodiment) [Configuration of Panoramic X-ray Tomographic Imaging Apparatus] As shown in FIG. 1, the panoramic X-ray tomographic imaging apparatus 1 includes an X-ray generator 2, an X-ray detector 3, a swivel arm 4, a swivel movement device 5, an imaging control device 6, and a panoramic X-ray tomographic image generation apparatus 7.

[0014] The X-ray generator 2 has a slit (not shown), and irradiates the subject O with a fan beam-shaped X-ray flux generated by emitting X-rays through this slit. The X-ray detector 3 receives the X-rays irradiated from the X-ray generator 2 and transmitted through the subject O, and images the portion of the subject O through which the X-rays have passed at a predetermined frame rate. The X-ray detector is, for example, an X-ray image intensifier (I.I.) or a flat panel detector (FPD).

[0015] As shown in FIGS. 1 and 2(b), the light receiving surface 3a of the X-ray detector 3 is disposed to face the irradiation portion of the X-ray generator 2. In FIG. 2(b), the X-ray generator 2 is simplified and shown as a circle, and the position of one tomographic plane 101 of the subject O is illustrated. Also, the rotation center C of the swivel arm 4 moves as shown in FIG. 2(a) during panoramic imaging. The swivel arm 4 holds the X-ray generator 2 and the X-ray detector 3 such that the subject O fits between the X-ray generator 2 and the light receiving surface 3a of the X-ray detector 3.

[0016] The swivel movement device 5 has a motor for driving the swivel arm 4. The swivel movement device 5 includes an X-Y axis motor 5a and a swivel axis motor 5b. The X-Y axis motor 5a is a motor for driving the swivel arm 4 in the X-axis direction and the Y-axis direction. The swivel axis motor 5b is a motor for swiveling the swivel arm 4. Fig. 2(a) is a conceptual diagram of the dental arch, which is the subject O, viewed from above. As shown in Fig. 2(a), when taking a tomographic image 101 in panoramic X-ray imaging, the rotation center C of the swivel arm 4 moves horizontally in Fig. 2(a) according to the swivel angle of the swivel arm 4. When photographing the molar region (for example, at an angle of 90 degrees), the rotation radius is large (the tomographic region is thick), and the rotation center C is located most to the right in Fig. 2(a). When photographing the anterior tooth region (for example, at an angle of 10 degrees), the rotation radius is small (the tomographic region is thin), and the rotation center C is located most to the left in Fig. 2(a).

[0017] The imaging control device 6 controls X-ray irradiation, X-ray detection, and arm swiveling in panoramic X-ray imaging, and has a hardware configuration similar to that of a general computer. Here, the imaging control device 6 includes a CPU 10, a RAM 11, and a main storage unit 12 in order to realize the above functions.

[0018] The CPU 10 includes a swivel arm control unit 13, an X-ray irradiation control unit 14, and an X-ray detector control unit 15. The swivel arm control unit 13 is a control means for controlling the drive of the swivel arm 4. The X-ray irradiation control unit 14 is a control means for controlling the drive of the X-ray generator 2. The X-ray detector control unit 15 is a control means for controlling the drive of the X-ray detector 3. These control means are, for example, the same as the controller of the panoramic X-ray tomographic imaging device disclosed in Patent Document 1.

[0019] The CPU 10 realizes the functions of the imaging control device 6 by executing an X-ray imaging execution program. The main memory unit 12 includes, for example, a ROM, an HDD, etc., and stores a program 16 and swing arm control information 17. The main memory unit 12 stores, as the program 16, for example, a boot program executed by the CPU 10 at startup, a program related to the hardware constituting the imaging control device 6, an X-ray imaging execution program, etc. The swing arm control information 17 is control information such as the coordinates of the arm rotation center position for each swing angle of the swing arm 4 during panoramic imaging. The display unit 18 displays the operation screen of the imaging control device 6 and the control state of X-ray imaging, and is, for example, a liquid crystal display. The operation unit 19 is operated by the operator of X-ray imaging, and is, for example, a power button, each function button, or an input device such as a keyboard and a mouse. Also, the display unit 18 and the operation unit 19 can be configured by a touch panel. Although not shown, the imaging control device 6 also includes an input / output interface for the display unit 18 and the operation unit 19, and a communication interface for communicating with the panoramic X-ray tomographic image generation device 7.

[0020] [Panoramic X-ray Tomographic Image Generation Device] The panoramic X-ray tomographic image generation device 7 is a device that generates a panoramic X-ray tomographic image on a tomographic plane set at an arbitrary depth in a subject based on a large number of frame image data obtained by one panoramic imaging in which a fan-shaped X-ray beam is irradiated onto the subject. The panoramic X-ray tomographic image generation device 7 has a hardware configuration similar to that of a general computer. Here, the panoramic X-ray tomographic image generation device 7 includes a CPU 20, a RAM 30, and a main memory unit 40.

[0021] The RAM 30 includes a frame image memory (frame image storage unit) 31. The frame image memory 31 is a storage unit that stores a large number of frame image data acquired by the X-ray detector 3 during one panoramic imaging.

[0022] The main memory unit 40 includes, for example, a ROM, an HDD, etc., and stores a program 41, swing arm position relationship information 42, and panoramic tomographic position information 43. As the program 41, the main memory unit 40 stores a boot program, a program related to the hardware constituting the panoramic X-ray tomographic image generation device 7, a panoramic X-ray tomographic image generation program, and the like. The swing arm position relationship information 42 is information including, for example, the position coordinates of the rotation center C for each swing angle of the swing arm 4 during panoramic imaging, the position coordinates of the X-ray detector 3, and the position coordinates of the X-ray generator 2. Note that the main memory unit 40 only needs to store at least the position coordinates of the rotation center C for each swing angle as the swing arm position relationship information 42. This is because the position coordinates of the X-ray detector 3 and the position coordinates of the X-ray generator 2 can be obtained by calculation based on the mechanical positional relationship among the rotation center C, the X-ray detector 3, and the X-ray generator 2 in the swing arm 4. The panoramic tomographic position information 43 is the position information of the reference tomographic plane in the panoramic tomographic image. The reference tomographic plane is the tomographic plane that serves as a reference during panoramic imaging. As the reference tomographic plane, for example, a standard tomographic plane set as the tomographic plane of a standard dental arch in the panoramic X-ray tomographic imaging device can be used. Usually, a plurality of standard tomographic planes are prepared according to the size or shape of the skeleton and dental arch. For example, a standard tomographic plane for adults and a standard tomographic plane for children can be prepared.

[0023] The display unit 51 displays the panoramic X-ray tomographic image and the operation screen, and is, for example, a liquid crystal display or the like. The operation unit 52 is operated by the operator and is, for example, an input device such as a mouse or a keyboard. Also, the display unit 51 and the operation unit 52 can be configured by a touch panel. Although not shown in the figure, the panoramic X-ray tomographic image generation device 7 also includes an input / output interface for the display unit 51 and the operation unit 52, and a communication interface for communicating with the imaging control device 6.

[0024] The CPU 20 realizes the functions of the panoramic X-ray tomographic image generation device 7 by executing a panoramic X-ray tomographic image generation program. The CPU 20 includes a panoramic X-ray image generation unit 60. The laminated thickness information and the distance information between tomographic images are input to the panoramic X-ray image generation unit 60. The laminated thickness information is information specifying the thickness of the pixel values of the pixels to be integrated into the panoramic tomographic image on the reference tomographic plane. The laminated thickness information is information corresponding to the thickness of the tomographic region of the panoramic X-ray imaging method, and can be, for example, 20 mm or the like. Based on this laminated thickness information, the tomographic region of the entire imaging range becomes thicker, and naturally, the tomographic region of the anterior tooth part also becomes thicker. The specified thickness is made thicker than the normal thickness of the anterior tooth part. By specifying a thicker thickness, the information integrated into the anterior tooth part can be increased. The distance information between tomographic images indicates the distance between two adjacent tomographic planes including the reference tomographic plane. The panoramic X-ray image generation unit 60 uses the laminated thickness information, the distance information between tomographic images, the swing arm position relationship information 42, and the panoramic tomographic position information 43 to obtain the path of the X-ray beam passing through the panoramic tomographic image on the set tomographic plane, and for each path of the X-ray beam, the pixel values of the pixels of the panoramic tomographic image on the other tomographic planes are integrated and averaged with the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane. Here, averaging means calculating the average of the integrated pixel values and using the calculation result (average value) as the pixel value of the pixel of the panoramic tomographic image on the reference tomographic plane again. The average value of the integrated pixel values is obtained by dividing the integrated pixel value (final integrated result) for that pixel by the number of tomographic planes set for that pixel.

[0025] In this embodiment, the panoramic X-ray image generation unit 60 sets a predetermined tomographic plane using the frame image memory 31, and generates a panoramic tomographic image on the set tomographic plane. The panoramic X-ray image generation unit 60 obtains the path of the X-ray beam passing through the pixel columns in the vertical direction (hereinafter referred to as vertical pixel columns) in the panoramic tomographic image. For example, as shown in FIG. 2(b), when one panoramic tomographic image is arranged on the tomographic plane 101, the position information of the tomographic plane 101 and the respective position information of the rotation center C of the X-ray generator 2, the X-ray detector 3, and the swing arm 4 (swing arm position relationship information 42) are used for calculation to obtain the path of the X-ray beam irradiated from the X-ray generator 2.

[0026] The panoramic X-ray image generation unit 60 obtains the height of each pixel in the vertical pixel column based on the path of the X-ray beam. Here, the vertical pixel column in the panoramic tomographic image will be described with reference to FIG. 3(a). As a premise, in the panoramic X-ray tomograph 1 (see FIG. 1), the swing arm 4 holds the X-ray generator 2 and the X-ray detector 3 at a predetermined distance apart, so the distance between the X-ray generator 2 and the light receiving surface 3a of the X-ray detector 3 is constant. For example, focusing on the tomographic plane 21, the sum of the distance a between the tomographic plane 21 and the X-ray generator 2 and the distance b between the tomographic plane 21 and the X-ray detector 3 is a constant value. Further, the X-ray generator 2 irradiates a fan-shaped X-ray beam. Here, the fan-shaped X-ray beam spreads in the vertical direction. Therefore, the closer the tomographic plane of the subject is to the X-ray generator 2, the lower the height of the panoramic tomographic image of that tomographic plane. Conversely, the farther the tomographic plane of the subject is from the X-ray generator 2, the higher the height of the panoramic tomographic image of that tomographic plane. The panoramic X-ray image generation unit 60 takes this vertical spread into account and obtains the height of each pixel in the vertical pixel column. As shown in FIG. 3(a), for example, the height H0 of the vertical pixel column of the panoramic tomographic image of the light receiving surface 3a of the X-ray detector 3 is higher than the height H1 of the vertical pixel column of the panoramic tomographic image of the tomographic plane 21. Also, the height H1 of the vertical pixel column of the panoramic tomographic image of the tomographic plane 21 is higher than the height H2 of the vertical pixel column of the panoramic tomographic image of the tomographic plane 22.

[0027] The panoramic X-ray image generation unit 60 performs a series of arithmetic processes of integrating the pixel values of each pixel in the vertical pixel column according to the height of each pixel in the vertical pixel column with respect to the pixel values of pixels having the same height on the reference tomographic plane on the path of the X-ray beam. As described above, the panoramic X-ray image generation unit 60 obtains the path of the X-ray beam passing through the vertical pixel column in the panoramic tomographic image generated on the set tomographic plane. FIG. 3(b) is a schematic diagram showing an example of the path of the X-ray beam passing through the vertical pixel column. In this example, it is assumed that the tomographic plane 102 is set on the side of the X-ray generator 2 rather than the reference tomographic plane 103 on the path of the X-ray beam. Also, the black circles indicate pixels. The panoramic X-ray image generation unit 60 integrates the pixel value of the pixel arranged at a predetermined height on the tomographic plane 102 with respect to the pixel value of the pixel arranged at the same height on the reference tomographic plane 103.

[0028] The panoramic X-ray image generation unit 60 executes this series of arithmetic processes while sequentially changing the vertical pixel column in the panoramic tomographic image, and executes the arithmetic processes for all the set tomographic planes while sequentially updating the tomographic planes set in the frame image memory 31. When the arithmetic processes are completed for all the set tomographic planes, the panoramic X-ray image generation unit 60 obtains the average value of the integrated pixel values for all the pixels on the reference tomographic plane 103 and replaces the pixel values of the pixels on the reference tomographic plane 103. The panoramic X-ray image generation unit 60 can perform correction (hereinafter referred to as image correction processing) so that the display is equivalent to the panoramic X-ray tomographic image taken with a conventional film. As shown in Fig. 2(a), in the panoramic X-ray tomographic imaging device, when the turning angle of the turning arm changes, the distance from the tomographic plane 101 to the rotation center C changes. In other words, when the turning angle of the turning arm changes, the ratio of the distance a from the X-ray generator 2 to the tomographic plane 21 and the distance (a + b) from the X-ray generator 2 to the X-ray detector 3 shown in Fig. 3(a) changes. Therefore, in the panoramic X-ray tomographic imaging device, when the turning angle of the turning arm changes, the size (magnification) of the image projected onto the X-ray detector 3 changes. That is, a panoramic tomographic image is generated in which the magnification of the anterior tooth part is larger than that of the molar part. Note that the image correction processing is not essential in this embodiment. However, it is preferable to perform the image correction processing because it is convenient for dentists who are accustomed to the panoramic X-ray tomographic images taken with conventional films if the height of the image is corrected so that the height of the anterior tooth part matches the height of the molar part.

[0029] [Operation of the panoramic X-ray tomographic imaging device] Next, the operation of the panoramic X-ray tomographic imaging device 1 according to the first embodiment will be described with reference to Fig. 4 (appropriately refer to Fig. 1). First, the panoramic X-ray tomographic imaging device 1 executes X-ray imaging (step S10). Specifically, in this step S10, under the control of the imaging control device 6, the turning arm 4 starts turning, and the X-ray generator 2 starts X-ray irradiation (step S11). Then, the panoramic X-ray tomographic image generation device 7 collects frame image data and stores it in the frame image memory 31 (step S12). When the imaging control device 6 finishes one panoramic imaging, it ends the turning of the turning arm 4 and ends the X-ray irradiation from the X-ray generator 2 (step S13). Next, the panoramic X-ray tomographic image generation device 7 generates a panoramic X-ray tomographic image by the panoramic X-ray image generation unit 60 (step S30), and displays the panoramic X-ray tomographic image on the display unit 51 (step S50).

[0030] [Operation of the panoramic X-ray tomographic image generation device] Next, the operation of step S30 of the panoramic X-ray tomographic image generation apparatus 7 according to the first embodiment will be described with reference to FIG. 5 (refer to FIG. 1 as appropriate). First, the panoramic X-ray tomographic image generation apparatus 7 sets the stacking thickness information and the distance information between tomographic images in the panoramic X-ray image generation unit 60 (step S31). The operator can input, for example, "20 mm" as the stacking thickness information or, for example, "0.5 mm" as the distance information between tomographic images. Note that the stacking thickness information may be set to a fixed value (for example, ±10 mm) and may not require input, or the operator may select from several candidate values. Similarly, the distance information between tomographic images may be set to a fixed value (for example, at 0.1 mm intervals) and may not require input, or the operator may select from several candidate values.

[0031] Next, the panoramic X-ray tomographic image generation apparatus 7 sets a reference tomographic plane in the panoramic X-ray image generation unit 60 (step S32). The operator can perform an operation of selecting, for example, "a standard tomographic plane for adults" as the reference tomographic plane. Next, based on the stacking thickness information and the distance information between tomographic images, the panoramic X-ray image generation unit 60 sets tomographic planes at predetermined intervals in a region based on the reference tomographic plane (step S33).

[0032] Here, the processing of the panoramic X-ray tomography image generation apparatus 7 will be described with reference to FIGS. 6(a) to 6(c) (also refer to FIGS. 2(b) and 2(a) as appropriate). Here, it is assumed that a large number of frame image data are acquired by the X-ray detector 3 in a single panoramic imaging of the reference tomographic plane. At this time, FIG. 6(a) shows a conceptual diagram of the reference tomographic plane 103 when viewed from above the dental arch. As shown in FIG. 6(b), the panoramic X-ray image generation unit 60 sets tomographic planes 104 at intervals of 0.5 mm between a region expanded, for example, 10 mm outward from the reference tomographic plane 103 to a region expanded, for example, 10 mm inward. That is, the panoramic X-ray image generation unit 60 sets, for example, 20 tomographic planes outside the reference tomographic plane 103 and, for example, 20 tomographic planes inside the reference tomographic plane 103. Note that FIG. 6(c) is an enlarged view of region B in FIG. 6(b). In this example, the set thickness 105 is 20 mm, and the distance information between the tomographic planes is at intervals of 0.5 mm.

[0033] Then, the panoramic X-ray image generation unit 60 generates a panoramic tomographic image on the nth tomographic plane using the frame image memory 31 (step S34). Then, the panoramic X-ray image generation unit 60 obtains the path of the X-ray beam passing through the vertical pixel column of the panoramic tomographic image (step S35). For example, as shown in FIG. 2(b), when one panoramic tomographic image is arranged on one tomographic plane 101, the pixels arranged on the path of the X-ray beam are obtained in this panoramic tomographic image.

[0034] Then, the panoramic X-ray image generation unit 60 calculates the height of each pixel on the n-th tomographic plane in consideration of the vertical spread of the X-ray beam (step S36). Then, the panoramic X-ray image generation unit 60 integrates the pixel value of each pixel in the panoramic tomographic image with the pixel value of the pixel at the same height on the reference tomographic plane on the path of the X-ray beam (step S37). Then, the panoramic X-ray image generation unit 60 determines whether the processes of steps S35 to S37 have been executed for all the vertical pixel columns (step S38). If the processes of steps S35 to S37 have not been executed for all the vertical pixel columns (step S38: No), the panoramic X-ray image generation unit 60 selects the next vertical pixel column (step S39) and returns to step S35.

[0035] On the other hand, if the processes of steps S35 to S37 have been executed for all the vertical pixel columns (step S38: Yes), the panoramic X-ray image generation unit 60 determines whether the processes of steps S34 to S39 have been executed for all the set tomographic planes (step S40). If the processes of steps S34 to S39 have not been executed for all the tomographic planes (step S40: No), the panoramic X-ray image generation unit 60 selects the next tomographic plane (step S41) and returns to step S34. On the other hand, if the processes of steps S34 to S39 have been executed for all the tomographic planes (step S40: Yes), the panoramic X-ray image generation unit 60 replaces the pixel value of each pixel in the panoramic tomographic image of the reference tomographic plane with the average value of the integrated pixel values (step S42). Then, the panoramic X-ray image generation unit 60 executes image correction processing (step S43) and returns to the main process.

[0036] The panoramic X-ray tomographic image generation device 7 according to this embodiment can thicken the tomographic region of the anterior teeth (for example, 20 mm) as described above. On the other hand, as shown in FIG. 7(a), the tomographic region 106 of a general panoramic X-ray imaging method is horseshoe-shaped according to the jawbone, and due to the principle of rotational tomography, the tomographic region 110 of the anterior teeth with a small rotation radius is thin. Therefore, as shown in FIG. 7(b), the focus may be on only one of the inclined maxillary anterior teeth 121 and mandibular anterior teeth 122. For example, as shown in FIG. 7(c), in the case of the focus position 111, although the focus is on the apical part of the mandibular anterior teeth 122, the image is such that the focus is not on the enamel of the mandibular anterior teeth 122 or the maxillary anterior teeth 121. Also, as shown in FIG. 7(d), in the case of the focus position 112, although the focus is on the maxillary anterior teeth 121, the image is such that the focus is not on the apical part of the mandibular anterior teeth 122. That is, in the prior art, it was not possible to focus on all of the inclined maxillary anterior teeth 121 and mandibular anterior teeth 122. Therefore, conventionally, dentists had to make a diagnosis by looking at either the image of FIG. 7(c) or FIG. 7(d).

[0037] In contrast, as shown in FIG. 8(a), the panoramic X-ray tomographic image generation device 7 according to this embodiment sets other tomographic planes 104 outside or inside the reference tomographic plane 103, and can generate a panoramic X-ray tomographic image including the improved tomographic region 130 of the anterior teeth. Note that the p-axis in FIG. 8(a) is an axis corresponding to the front-back direction, and the q-axis is an axis orthogonal to the p-axis. FIG. 8(b) is a conceptual diagram of the focus positions of the maxillary anterior teeth 121 and mandibular anterior teeth 122, and FIG. 8(c) is a conceptual diagram showing the correspondence between the focus positions of the maxillary anterior teeth 121 and mandibular anterior teeth 122 and the panoramic X-ray tomographic image. According to the panoramic X-ray tomographic image generation device 7, as shown in FIG. 8(b), since the improved tomographic region 130 of the anterior teeth is thick, it is possible to focus on all of the inclined maxillary anterior teeth 121 and mandibular anterior teeth 122. Therefore, it is easier to position the patient with a better focus. Also, due to the improved tomographic region 130 of the anterior teeth, a panoramic X-ray tomographic image with a large amount of information on the anterior teeth can be obtained.

[0038] Since the panoramic X-ray tomographic image generation device 7 can acquire tomographic information over a wide range, a single panoramic X-ray tomographic image contains a lot of information. Especially in the anterior tooth region, more information is included compared to a general panoramic X-ray tomographic image. Since the panoramic X-ray tomographic image is taken for the purpose of comprehensively diagnosing the state of teeth and jaws, it is possible to provide an X-ray image that is more useful for dental treatment. Conventionally, when necessary image information in the depth direction cannot be obtained by panoramic X-ray tomography, it has been common to take additional dental X-rays. Therefore, according to the panoramic X-ray tomographic image generation device 7, it is assumed that dental X-ray photography may be unnecessary, and an effect of reducing patient exposure can also be expected.

[0039] (Second Embodiment) Next, the configuration of the panoramic X-ray tomographic imaging device 1B according to the second embodiment will be described with reference to FIG. 9. In the panoramic X-ray tomographic imaging device 1B, the same components as those of the panoramic X-ray tomographic imaging device 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The panoramic X-ray tomographic image generation device 7B has a function different from that of the first embodiment.

[0040] The panoramic X-ray tomographic image generation device 7B includes a CPU 20, a RAM 30, and a main storage unit 40. The CPU 20 includes a panoramic X-ray image generation unit 60B, and the RAM 30 includes a frame image memory 31 and a three-dimensional image memory (three-dimensional image storage unit) 32. The three-dimensional image memory 32 stores an aggregate of a plurality of panoramic tomographic images as a three-dimensional image in a virtual three-dimensional space.

[0041] The panoramic X-ray image generation unit 60B includes a panoramic tomographic image generation unit 61 and a pseudo 3D volume image generation unit 62. The pseudo 3D volume image generation unit 62 sets a plurality of tomographic planes at predetermined intervals on the virtual 3D space of the 3D image memory 32, using any one of one or more standard tomographic planes as a reference tomographic plane, the reference tomographic plane, the stack thickness information, and the distance information between tomographic planes. Then, it sets one of the plurality of tomographic planes using the frame image memory 31 and generates a panoramic tomographic image on the set tomographic plane. The pseudo 3D volume image generation unit 62 obtains the path of the X-ray beam passing through the vertical pixel column in the panoramic tomographic image, and corrects the height of the vertical pixel column according to the position of the tomographic plane for each vertical pixel column, considering the vertical spread of the X-ray beam based on the path of the X-ray beam. The pseudo 3D volume image generation unit 62 generates a pseudo 3D volume image by executing a series of arithmetic processes of sequentially arranging the pixel columns with corrected heights on the corresponding tomographic planes set on the virtual 3D space, while sequentially changing the tomographic planes for all the set tomographic planes. The panoramic tomographic image generation unit 61 obtains the path of the X-ray beam passing through the vertical pixel column on the reference tomographic plane in the pseudo 3D volume image. The panoramic tomographic image generation unit 61 obtains the pixels on the cut surface formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the path of the X-ray beam. The panoramic tomographic image generation unit 61 integrates the pixel values of each pixel with the same height on the cut surface, and replaces the pixel value of the corresponding pixel on the reference tomographic plane with the average value of the integrated pixel values, and executes this process for all the vertical pixel columns on the reference tomographic plane. The panoramic tomographic image generation unit 61 generates a panoramic tomographic image using the replaced pixels on the reference tomographic plane.

[0042] In the panoramic X-ray tomographic image generation apparatus 7B, the main memory unit 40 also stores, as a program 41B, a program for causing the panoramic X-ray tomographic image generation apparatus 7B to function.

[0043] FIG. 10(a) is a conceptual diagram of the panoramic tomographic image 141 of the reference tomographic plane. FIG. 10(b) is a conceptual diagram of constructing a pseudo 3D volume image by arranging the panoramic tomographic images 143 of each tomographic plane in the 3D space 142. Here, as an example, the tomographic planes are shifted at a predetermined interval outside the reference tomographic plane to expand the tomographic plane and three panoramic tomographic images are arranged, and also the tomographic planes are shifted at a predetermined interval inside the reference tomographic plane to shrink the tomographic plane and three panoramic tomographic images are arranged, and the state is illustrated. Note that the panoramic tomographic images can also be arranged on either the outside or the inside of the reference tomographic plane.

[0044] Here, in the pseudo 3D volume image, numerous panoramic tomographic images overlap like a stack of pancakes. For example, when viewing the pseudo 3D volume image generated by shifting the tomographic planes at 0.1 mm intervals from above, as shown in the conceptual diagram of FIG. 11(a), the panoramic tomographic images 143 of each tomographic plane arranged outside and inside the reference tomographic plane 103 overlap and form a lump.

[0045] FIG. 11(b) shows an example of the pseudo 3D volume image generated in the experiment. In FIG. 11(b), the image in the lower right shows the 3D image of the appearance of the pseudo 3D volume image. The image in the lower left is the image of the pseudo 3D volume image viewed from above. The image in the upper left is the image of the cross-section obtained by cutting the anterior tooth part of the pseudo 3D volume image in the q-axis direction from top to bottom. The image in the upper right is the image of the cross-section obtained by cutting the molar part of the pseudo 3D volume image in the p-axis direction from top to bottom.

[0046] FIG. 12 is a conceptual diagram of an X-ray transmission path in a 3D space. FIG. 12(a) corresponds to a state where the pseudo-3D volume image 145 is viewed from above in the 3D space 142. FIG. 12(b) corresponds to a state where the pseudo-3D volume image 145 is viewed from the side. Here, the pseudo-3D volume image 145 is generated by shifting tomograms at intervals of, for example, 0.1 mm outside and inside the reference tomographic plane 103. The pseudo-3D volume image 145 has an improved tomographic region 130 in the anterior tooth region. As shown in FIG. 12(a), the panoramic X-ray tomographic image generation device 7B calculates the path 146 of the X-ray beam from the X-ray generator 2 to the light-receiving surface 3a of the X-ray detector 3 through the pseudo-3D volume image 145. The panoramic X-ray tomographic image generation device 7B calculates not only the path in the width direction of the X-ray beam but also the path in the height direction of the X-ray beam. Note that in FIG. 12(a), the positions of the X-ray generator 2 and the X-ray detector 3 are examples and change with the turning angle of the turning arm 4 and the movement of the rotation center C. The panoramic X-ray tomographic image generation device 7B uses the turning arm position relationship information 42 (see FIG. 9) as this position information.

[0047] FIG. 13 is a conceptual diagram similar to FIG. 12 and shows the correspondence with the panoramic X-ray tomographic image generated in the subsequent process. The path 146 of the X-ray beam is shown by five arrows in the width direction (q direction), and each of these schematically shows the X-ray beam passing through the vertical pixel columns on the reference tomographic plane 103. If the number of necessary pixels in the width direction (q direction) in the panoramic X-ray image generated in this subsequent process is, for example, 600 pixels, the panoramic X-ray tomographic image generation device 7B calculates the path 146 of the X-ray beam assuming, for example, 600 paths in the width direction.

[0048] FIG. 14(a) is a schematic diagram of an X-ray beam viewed horizontally after generating a pseudo 3D volume image. The path of this X-ray beam passes through a vertical pixel column on the reference tomographic plane 103. Here, a cross-section obtained by cutting the pseudo 3D volume image 145 with a vertical plane that coincides with the path of the X-ray beam is shown by hatching. In FIG. 14(a), a portion corresponding to the anterior teeth is shown as the pseudo 3D volume image 145. The pseudo 3D volume image has a shape where the left side (the side away from the X-ray generator 2) is higher than the right side (the side closer to the X-ray generator 2) in FIG. 14(a). Here, the shape of the cross-section of the pseudo 3D volume image is rectangular. The height of the left side (the side away from the X-ray generator 2) of this rectangle is higher than the height of the right side (the side closer to the X-ray generator 2) of the rectangle. The pseudo 3D volume image 145 contains the pixel values of each of a large number of pixels as image data.

[0049] FIG. 14(b) is a schematic diagram of an X-ray beam viewed horizontally after generating a pseudo 3D volume image, similar to FIG. 14(a). The path of this X-ray beam passes through a vertical pixel column on the reference tomographic plane 103. However, in FIG. 14(b), the hatching on the cross-section of the pseudo 3D volume image is removed, and instead, black circles indicate each pixel (image data). Here, the shape of the cross-section of the pseudo 3D volume image is rectangular. A virtual line connecting a pixel on the left side of this rectangle and a pixel on the right side of the rectangle schematically shows that the panoramic tomographic image generation unit 61 integrates and averages the pixel values of each pixel having the same height on the cross-section. Note that when integrating the pixel values of pixels having the same height on the cross-section of the pseudo 3D volume image, the number of pixels to be integrated (the number of set tomographic planes) may differ depending on the height of the pixels, and the denominators may also differ when averaging the integrated values. Also, due to the difference in the horizontal position of each vertical pixel column on the reference tomographic plane 103, the number of pixels to be integrated may differ, and the denominators may also differ when averaging the integrated values.

[0050] [Operation of the Panoramic X-ray Tomography Apparatus] Next, the operation of the panoramic X-ray tomograph 1B according to the second embodiment will be described with reference to FIG. 15 (refer to FIGS. 9 and 4 as appropriate). The same procedures as those shown in FIG. 4 are denoted by the same reference numerals and the description thereof will be omitted. First, the panoramic X-ray tomograph 1B according to the second embodiment executes X-ray imaging (step S10). This step S10 includes the above-described steps S11, S12, and S13. Next, the panoramic X-ray tomographic image generation device 7B according to the second embodiment generates a panoramic X-ray tomographic image by the panoramic X-ray image generation unit 60B (step S30B), and displays the panoramic X-ray tomographic image on the display unit 51 (step S50). The process of step S30B includes a pseudo 3D volume image generation process (step S100) and a panoramic tomographic image generation process (step S200).

[0051] [Operation of Panoramic X-ray Tomographic Image Generation Device] Next, the operation of step S30B of the panoramic X-ray tomographic image generation device 7B according to the second embodiment will be described with reference to FIGS. 16 and 17 (refer to FIG. 9 as appropriate). The pseudo 3D volume image generation unit 62 of the panoramic X-ray tomographic image generation apparatus 7B executes a pseudo 3D volume image generation process (step S100). FIG. 16 is a flowchart showing the pseudo 3D volume image generation process of FIG. 15. The processes of steps S131 to S135 shown in FIG. 16 are substantially the same as the processes of steps S31 to S35 shown in FIG. 5. That is, the panoramic X-ray tomographic image generation apparatus 7B sets the stacking thickness information and the distance information between tomographic images in the pseudo 3D volume image generation unit 62 (step S131). Next, the panoramic X-ray tomographic image generation apparatus 7B sets a reference tomographic plane in the pseudo 3D volume image generation unit 62 (step S132). Next, based on the stacking thickness information and the distance information between tomographic images, the pseudo 3D volume image generation unit 62 sets tomographic planes at predetermined intervals in a region based on the reference tomographic plane in the 3D image memory 32 (step S133). Then, the pseudo 3D volume image generation unit 62 generates a panoramic tomographic image on the nth tomographic plane using the frame image memory 31 (step S134). Then, the pseudo 3D volume image generation unit 62 obtains the path of the X-ray beam passing through the vertical pixel column of the panoramic tomographic image on the nth tomographic plane (step S135).

[0052] Subsequently to step S135, based on the path of the X-ray beam obtained in step S135, the pseudo 3D volume image generation unit 62 corrects the height of the vertical pixel column in consideration of the vertical spread of the X-ray beam, and arranges the corrected pixel column on the nth tomographic plane in the 3D image memory 32 (step S137).

[0053] The processing of steps S138 to S141 following this step S137 is generally the same as the processing of steps S38 to S41 shown in FIG. 5. That is, the pseudo 3D volume image generation unit 62 determines whether the processing of steps S135 and S137 has been executed for all vertical pixel columns (step S138). If the processing of steps S135 and S137 has not been executed for all vertical pixel columns (step S138: No), the pseudo 3D volume image generation unit 62 selects the next vertical pixel column (step S139) and returns to step S135. On the other hand, if the processing of steps S135 and S137 has been executed for all vertical pixel columns (step S138: Yes), the pseudo 3D volume image generation unit 62 determines whether the processing of steps S134 to S139 has been executed for all tomographic planes (step S140). If the processing of steps S134 to S139 has not been executed for all tomographic planes (step S140: No), the pseudo 3D volume image generation unit 62 selects the next tomographic plane (step S141) and returns to step S134. On the other hand, if the processing of steps S134 to S139 has been executed for all tomographic planes (step S140: Yes), the panoramic X-ray tomographic image generation apparatus 7B returns to the main processing.

[0054] In addition, the panoramic tomography image generation unit 61 of the panoramic X-ray tomography image generation apparatus 7B executes a panoramic tomography image generation process (step S200). FIG. 17 is a flowchart showing the panoramic tomography image generation process of FIG. 15. As shown in FIG. 17, the panoramic tomography image generation unit 61 obtains the path of the X-ray beam passing through the vertical pixel column on the reference tomographic plane (step S201). Then, the panoramic tomography image generation unit 61 obtains the pixels on the cut surface formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the X-ray beam (step S202). Then, on the cut surface of the pseudo 3D volume image, the panoramic tomography image generation unit 61 integrates the pixel values of the pixels arranged at the same height, and sets the average value of the integrated pixel values as the pixel value of the corresponding pixel in the vertical pixel column on the reference tomographic plane (step S203). Then, the panoramic tomography image generation unit 61 determines whether the processes of steps S201 to S203 have been executed for all the vertical pixel columns on the reference tomographic plane (step S204). If the processes of steps S201 to S203 have not been executed for all the vertical pixel columns on the reference tomographic plane (step S204: No), the panoramic tomography image generation unit 61 selects the next vertical pixel column (step S205) and returns to step S201. On the other hand, if the processes of steps S201 to S203 have been executed for all the vertical pixel columns on the reference tomographic plane (step S204: Yes), the panoramic tomography image generation unit 61 generates a panoramic X-ray tomography image from the pixels on the reference tomographic plane (step S206). Then, the panoramic tomography image generation unit 61 executes an image correction process (step S207) and returns to the main process.

[0055] (Third Embodiment) Next, with reference to FIG. 18, the configuration of the panoramic X-ray tomography apparatus 1C according to the third embodiment will be described. In the panoramic X-ray tomography apparatus 1C, the same components as those of the panoramic X-ray tomography apparatus 1B shown in FIG. 9 are denoted by the same reference numerals and the description thereof is omitted. The function of the panoramic X-ray tomography image generation apparatus 7C of the panoramic X-ray tomography apparatus 1C is different from that of the second embodiment. In the panoramic X-ray tomography image generation apparatus 7C, the reference plane when obtaining the path of the X-ray beam in the pseudo 3D volume image is a tomographic plane using an autofocus function instead of the standard tomographic plane.

[0056] The panoramic X-ray tomographic image generation device 7C includes a panoramic X-ray image generation unit 60C. The panoramic X-ray image generation unit 60C includes a panoramic tomographic image generation unit 61C, a pseudo 3D volume image generation unit 62, and an autofocus unit 63. The pseudo 3D volume image generation unit 62 sets a plurality of tomographic planes at predetermined intervals on the virtual 3D space of the 3D image memory 32, using any one of one or more standard tomographic planes as a reference tomographic plane, the reference tomographic plane, the stacking thickness information, and the distance information between the tomographic planes. Then, it sets one tomographic plane out of the plurality of tomographic planes using the frame image memory 31, and generates a panoramic tomographic image on the set tomographic plane. The pseudo 3D volume image generation unit 62 obtains the path of the X-ray beam passing through the vertical pixel column in the panoramic tomographic image, and corrects the height of the vertical pixel column according to the position of the tomographic plane for each vertical pixel column, considering the vertical spread of the X-ray beam based on the path of the X-ray beam. The pseudo 3D volume image generation unit 62 generates a pseudo 3D volume image by executing a series of arithmetic processes of sequentially arranging the pixel columns with corrected heights on the corresponding tomographic planes set on the virtual 3D space, while sequentially changing the tomographic planes for all the set tomographic planes. The autofocus unit 63 generates a plurality of panoramic tomographic images with different shift amounts of the frame image data corresponding to a plurality of tomographic planes based on a large number of frame image data obtained by one panoramic photographing, and extracts an autofocus tomographic plane, which is the tomographic plane with the best focus of the subject, by frequency analysis processing. The panoramic tomographic image generation unit 61C obtains the path of the X-ray beam passing through the vertical pixel column on the autofocus tomographic plane in the pseudo 3D volume image. The panoramic tomographic image generation unit 61C obtains the pixels on the cut surface formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the path of the X-ray beam, integrates the pixel values of each pixel having the same height on the cut surface, and replaces the pixel value of the corresponding pixel on the autofocus tomographic plane with the average value of the integrated pixel values. This process is executed for all the pixels on the autofocus tomographic plane. The panoramic tomographic image generation unit 61C generates a panoramic tomographic image using the replaced pixels on the autofocus tomographic plane.

[0057] In the panoramic X-ray tomographic image generation apparatus 7C, the 3D image memory 32 of the RAM 30 is used not only to construct a pseudo 3D volume image using the generated panoramic tomographic image but also to extract the autofocus tomographic plane. Further, in the panoramic X-ray tomographic image generation apparatus 7C, the main storage unit 40 stores, as a program 41C, a program for causing the panoramic X-ray tomographic image generation apparatus 7C to function.

[0058] As the autofocus unit 63, for example, the autofocus function disclosed in Patent Document 1 can be used. FIG. 19 is a schematic diagram showing an example of the autofocus tomographic plane. The autofocus unit 63 generates a multi-tomography model, which is a model in which the position information of a plurality of tomographic planes and the position information in the high-frequency region are respectively associated by frequency analysis processing. For example, when the autofocus unit 63 acquires a multi-tomography model in which 9 sample points are associated, as shown in FIG. 19, the autofocus unit 63 connects each of the sample points 8a to 8i and interpolates the position information of each of the sample points 8a to 8i to generate an interpolated multi-tomography model M 2 having a smoothly connected curve. The position information of this connected curve indicates the autofocus tomographic plane G. Further, the autofocus unit 63 obtains the distance (rotation radius) between the positions of each of the sample points 8a to 8i and the position of the rotation center C of the swivel arm 4. In FIG. 19, the rotation radius is the distance r from the rotation center to the sample points 8a and 8ea , r e is exemplified.

[0059] [Operation of Panoramic X-ray Tomography Device] Next, the operation of the panoramic X-ray tomography device 1C according to the third embodiment will be described with reference to FIG. 20 (appropriately refer to FIGS. 18 and 15). The same procedures as those shown in FIG. 15 are denoted by the same reference numerals and the description thereof will be omitted. First, the panoramic X-ray tomography device 1C according to the third embodiment executes X-ray imaging (step S10). Next, the panoramic X-ray image generation device 7C according to the third embodiment generates a panoramic X-ray tomographic image by the panoramic X-ray image generation unit 60C (step S30C), and displays the panoramic X-ray tomographic image on the display unit 51 (step S50). In the process of step S30C, the pseudo 3D volume image generation process (step S100) is the same as the process shown in FIG. 16, so further description thereof will be omitted. Following step S100, the autofocus unit 63 of the panoramic X-ray tomography image generation device 7C obtains an autofocus tomographic plane (step S300). Then, the panoramic tomographic image generation unit 61C of the panoramic X-ray tomography image generation device 7C executes a panoramic tomographic image generation process (step S200C).

[0060] Next, the operation of step S200C will be described with reference to FIG. 21 (also refer to FIG. 18 as appropriate). As shown in FIG. 21, the panoramic tomographic image generation unit 61C obtains the path of the X-ray beam passing through the vertical pixel column on the autofocus tomographic plane (step S201C). Then, the panoramic tomographic image generation unit 61C obtains the pixels on the cut surface formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the X-ray beam (step S202C). Then, on the cut surface of the pseudo 3D volume image, the panoramic tomographic image generation unit 61C integrates the pixel values of the pixels arranged at the same height, and sets the average value of the integrated pixel values as the pixel value of the corresponding pixel in the vertical pixel column on the autofocus tomographic plane (step S203C). Then, the panoramic tomographic image generation unit 61C determines whether the processes of steps S201C to S203C have been executed for all the vertical pixel columns on the autofocus tomographic plane (step S204C). If the processes of steps S201C to S203C have not been executed for all the vertical pixel columns on the autofocus tomographic plane (step S204C: No), the panoramic tomographic image generation unit 61C selects the next vertical pixel column (step S205) and returns to step S201C. On the other hand, if the processes of steps S201C to S203C have been executed for all the vertical pixel columns on the autofocus tomographic plane (step S204C: Yes), the panoramic tomographic image generation unit 61C generates a panoramic tomographic image from the pixels on the autofocus tomographic plane (step S206C). Then, the panoramic tomographic image generation unit 61C executes image correction processing (step S207) and returns to the main processing.

[0061] (Modification of the Third Embodiment) As shown in FIG. 18, the panoramic X-ray tomographic image generation apparatus 7C according to the modification of the third embodiment includes an autofocus unit 63, a pseudo 3D volume image generation unit 62, and a panoramic tomographic image generation unit 61C. However, the panoramic X-ray tomographic image generation apparatus 7C according to the modification of the third embodiment uses the autofocus tomographic plane as the reference plane when obtaining the path of the X-ray beam in the pseudo 3D volume image, and also uses the autofocus tomographic plane as the reference plane when generating the pseudo 3D volume image.

[0062] Therefore, the pseudo 3D volume image generation unit 62 according to the modification example sets a plurality of tomographic planes at predetermined intervals on the virtual 3D space of the 3D image memory 32 on the basis of the autofocus tomographic plane G as the reference tomographic plane, using the autofocus tomographic plane, the stacking thickness information, and the distance information between tomographic planes. Then, it sets one tomographic plane out of the plurality of tomographic planes using the frame image memory 31, and generates a panoramic tomographic image on the set tomographic plane. The pseudo 3D volume image generation unit 62 obtains the path of the X-ray beam passing through the vertical pixel column in the panoramic tomographic image, and corrects the height of the vertical pixel column according to the position of the tomographic plane for each vertical pixel column in consideration of the vertical spread of the X-ray beam based on the path of the X-ray beam. The pseudo 3D volume image generation unit 62 generates a pseudo 3D volume image by executing a series of arithmetic processes of sequentially arranging the pixel columns with corrected heights on the corresponding tomographic planes set on the virtual 3D space for all the tomographic planes to be set while sequentially changing the tomographic planes. Note that the autofocus unit 63 and the panoramic tomographic image generation unit 61C are the same as those in the third embodiment.

[0063] Next, the operation of the panoramic X-ray tomograph 1C according to the modification example of the third embodiment will be described with reference to FIG. 22 (appropriately refer to FIGS. 18 and 20). The same procedures as those shown in FIG. 20 are denoted by the same reference numerals and the description thereof is omitted. In the modification example, in the process of generating a panoramic X-ray tomographic image (step S30D), the difference from the operation of the third embodiment is that a pseudo 3D volume image is generated based on the autofocus tomographic plane. Therefore, as shown in FIG. 22, the panoramic X-ray image generation unit 60C according to the modification example executes, in the process of step S30D, the process of obtaining the autofocus tomographic plane (step S300D), the pseudo 3D volume image generation process (step S100D), and the panoramic tomographic image generation process (step S200D) in this order. Here, the process of obtaining the autofocus tomographic plane (step S300D) is the same as the process of obtaining the autofocus tomographic plane (step S300) shown in FIG. 20.

[0064] The pseudo-3D volume image generation unit 62 according to the modification example sets the autofocus tomographic plane as the reference tomographic plane (step S132D) in the pseudo-3D volume image generation process (step S100D) as shown in FIG. 23. Since the processes other than step S132D in the pseudo-3D volume image generation process (step S100D) shown in FIG. 23 are the same as those in the pseudo-3D volume image generation process (step S100) shown in FIG. 16, further description thereof is omitted. In addition, since the panoramic tomographic image generation process (step S200D) shown in FIG. 22 is the same as the panoramic tomographic image generation process (step S200C) shown in FIG. 17, further description thereof is omitted.

[0065] As described above, the panoramic X-ray tomographic image generation apparatus and the panoramic X-ray tomographic imaging apparatus according to the embodiments of the present invention have been described. However, the gist of the present invention is not limited to these descriptions and should be broadly interpreted based on the descriptions in the claims. Needless to say, various changes and modifications based on these descriptions are also included in the gist of the present invention. For example, in the second embodiment, the pseudo-3D volume image is generated by shifting the tomographic planes at intervals of 0.1 mm. However, the interval is not limited to this and may be wider or narrower. In the first embodiment, the set thickness 105 is 20 mm, and the tomographic planes 104 at intervals of 0.5 mm are set respectively. However, the thickness and the interval may be wider or narrower. Further, for example, by using two panoramic tomographic images, i.e., the panoramic tomographic image of the reference tomographic plane and the panoramic tomographic image arranged at a tomographic position 5 mm outside the reference tomographic plane, and integrating the panoramic tomographic image of another tomographic position into the panoramic tomographic image of the reference tomographic plane based on the path of the X-ray beam, the same effect can be achieved.

[0066] In the panoramic X-ray tomographic image generation apparatus 7 according to the first embodiment, the process of integrating the pixel values of each pixel having the same height on the reference tomographic plane may be applied only to a specified range of turning angles including the front tooth part. Hereinafter, the specified range of turning angles including the front tooth part is referred to as a stacking range. The operation of the panoramic X-ray image generation unit 60 (see FIG. 1) of the panoramic X-ray tomographic image generation apparatus 7 according to this modification will be described with reference to FIG. 24. First, the panoramic X-ray tomographic image generation apparatus 7 sets the stacking thickness information, the distance information between tomographic planes, and the stacking range in the panoramic X-ray image generation unit 60 (step S31B). Here, if the stacking range is not set, the tomographic region of the entire imaging range becomes thick based on the stacking thickness information. However, by setting the stacking range, only the tomographic region of the specified range including the front tooth part becomes thick. Then, the panoramic X-ray tomographic image generation apparatus 7 sets a reference tomographic plane in the panoramic X-ray image generation unit 60 (step S32), and sets tomographic planes at predetermined intervals in the region based on the reference tomographic plane based on the stacking thickness information and the distance information between tomographic planes (step S33). Subsequently, the panoramic X-ray image generation unit 60 generates a panoramic tomographic image on the reference tomographic plane (step S45). Thereafter, the processes of steps S34B to S43 are the same as the processes of steps S34 to S43 in FIG. 5, so the description thereof is omitted. Note that the processes of steps S34B to S38B and S42B are the same as the processes of steps S34 to S38 and S42 in FIG. 5 except that the processes are performed in the specified stacking range.

[0067] Further, in the panoramic X-ray tomographic image generation apparatus 7B according to the second embodiment, the pseudo 3D volume image generation process and the process of integrating the pixel values of each pixel having the same height on the cut surface of the pseudo 3D volume image may be applied only to a specified range of turning angles (stacking range) including the front tooth part. The operation of the panoramic X-ray image generation unit 60B (see FIG. 9) of the panoramic X-ray tomographic image generation apparatus 7B according to this modification will be described with reference to FIGS. 25 and 26. As shown in FIG. 25, the panoramic X-ray tomographic image generation apparatus 7B sets the stacking thickness information, the distance information between tomographic images, and the stacking range in the pseudo 3D volume image generation unit 62 (step S131B). Next, the panoramic X-ray tomographic image generation apparatus 7B sets a reference tomographic plane in the pseudo 3D volume image generation unit 62 (step S132). Thereafter, the processes of steps S133 to S141 performed by the pseudo 3D volume image generation unit 62 are the same as the processes of steps S133 to S141 in FIG. 16, and thus the description thereof is omitted. Note that the processes of steps S134B to S135B and S138B are the same as the processes of steps S134 to S135 and S138 in FIG. 16, except that the processes are performed within the specified stacking range. Also, as shown in FIG. 26, the panoramic tomographic image generation unit 61 of the panoramic X-ray image generation unit 60B generates a panoramic tomographic image on the reference tomographic plane and arranges it on the reference tomographic plane of the 3D image memory 32 (step S210). Thereafter, the processes of steps S201B to S207 performed by the panoramic tomographic image generation unit 61 are the same as the processes of steps S201 to S207 in FIG. 17, and thus the description thereof is omitted. Note that the processes of steps S201B and S204B are the same as the processes of steps S201 and S204 in FIG. 17, except that the processes are performed within the specified stacking range. In a modification example of specifying the range of these turning angles (stacking range), for the outside of the specified turning angle range, a panoramic X-ray tomographic image can be generated using the pixels of the reference tomographic plane as they are. In particular, if the process is limited to only the front tooth part where the tomographic image is thin, the calculation amount can be reduced, which is preferable as it saves processing time.

[0068] Similarly, the panoramic X-ray tomographic image generation apparatus 7C according to the third embodiment and its modification example may apply the pseudo 3D volume image generation process and the process of integrating the pixel values of each pixel having the same height on the cutting plane of the pseudo 3D volume image only to the specified turning angle range (stacking range) including the front tooth part.

[0069] The panoramic X-ray tomographic image generation device 7B according to the second embodiment may change the weights (coefficients) when integrating the respective pixel values of the pixels having the same height on the cutting plane of the pseudo 3D volume image for each part such as the anterior tooth part, the premolar part, and the molar part. Further, the panoramic X-ray tomographic image generation device may change the weights (coefficients) when integrating the respective pixel values of the pixels having the same height on the cutting plane of the pseudo 3D volume image for each range of the turning angle. In the case of a normal panoramic tomographic image, the tomographic region becomes thinner in the order of the molar part, the premolar part, and the anterior tooth part. However, by gradually increasing the weights (coefficients) when integrating the pixel values in the order of the molar part, the premolar part, and the anterior tooth part, a panoramic X-ray tomographic image with reduced unnaturalness can be generated.

Explanation of Signs

[0070] 1, 1B, 1C Panoramic X-ray tomographic imaging device 2 X-ray generator 3 X-ray detector 3a Light receiving surface 4 Swivel arm 5 Swivel movement device 5a X-Y axis motor 5b Swivel axis motor 6 Imaging control device 7, 7B, 7C Panoramic X-ray tomographic image generation device 10 CPU 11 RAM 12 Main memory unit 13 Swivel arm control unit 14 X-ray irradiation control unit 15 X-ray detection unit control unit 16 Program 17 Swivel arm control information 18 Display unit 19 Operation unit 20 CPU 30 RAM 31 Frame image memory (frame image storage unit) 32 3D image memory (3D image storage unit) 40 Main memory unit 41, 41B, 41C Program 42 Swing arm position relationship information 43 Panoramic tomogram position information 51 Display unit 52 Operation unit 60, 60B, 60C Panoramic X-ray image generation unit 61, 61C Panoramic tomogram image generation unit 62 Virtual 3D volume image generation unit 63 Auto focus unit 103 Reference tomographic plane 145 Virtual 3D volume image 146 Path of X-ray beam C Center of rotation O Subject

Claims

1. A panoramic X-ray tomographic image generation device that generates a panoramic X-ray tomographic image on a tomographic plane set at an arbitrary depth in a subject based on a number of frame image data obtained by a single panoramic photographing that irradiates a fan-shaped X-ray beam on the subject, a main storage unit that stores turning arm position relationship information including the position coordinates of the rotation center for each turning angle of the turning arm during panoramic photographing, and panoramic tomographic position information that is the position information of the reference tomographic plane in the panoramic tomographic image, a frame image storage unit that stores a number of frame image data acquired by an X-ray detector in a single panoramic photographing, a panoramic X-ray image generation unit that obtains a path of an X-ray beam passing through a panoramic tomographic image on a set tomographic plane using lamination thickness information that is information specifying the thickness of the pixel value of a pixel to be integrated into the panoramic tomographic image on the reference tomographic plane, inter-slice distance information indicating the distance between two adjacent tomographic planes including the reference tomographic plane, the turning arm position relationship information, and the panoramic tomographic position information, and based on the path of the X-ray beam, integrates the pixel values of the pixels of the panoramic tomographic image on other tomographic planes into the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane, and sets the average value of the integrated pixel values as the pixel values of the pixels of the panoramic tomographic image on the reference tomographic plane. A panoramic X-ray tomographic image generation device characterized by comprising:

2. The panoramic X-ray tomographic image generation device according to claim 1, wherein the range to be laminated on the panoramic tomographic image on the reference tomographic plane is only the range of a specified turning angle including the anterior teeth part.

3. The panoramic X-ray image generation unit sets a predetermined tomographic plane using the frame image storage unit, generates a panoramic tomographic image on the set tomographic plane, obtains the path of the X-ray beam passing through the pixel column in the vertical direction in the panoramic tomographic image, obtains the height of each pixel in the pixel column in the vertical direction based on the path of the X-ray beam, and integrates the pixel value of each pixel in the pixel column in the vertical direction with respect to the pixel value of a pixel having the same height on a reference tomographic plane on the path of the X-ray beam according to the height of the pixel. A series of arithmetic processes are executed while sequentially changing the pixel column in the vertical direction in the panoramic tomographic image, and while sequentially updating the tomographic plane set in the frame image storage unit, the arithmetic process is executed for all the set tomographic planes. For all the pixels on the reference tomographic plane, the average value of the integrated pixel values is obtained respectively and used as the pixel value of the pixel on the reference tomographic plane. The panoramic X-ray tomographic image generation apparatus according to claim 1, characterized in that.

4. It includes a three-dimensional image storage unit that stores an aggregate composed of a plurality of the panoramic tomographic images as a three-dimensional image in a virtual three-dimensional space. The panoramic X-ray image generation unit After using any one of one or more standard tomographic planes as the reference tomographic plane, using the reference tomographic plane, the stack thickness information, and the distance information between tomographic planes, a plurality of tomographic planes are set at predetermined intervals on the virtual three-dimensional space of the three-dimensional image storage unit. One of the plurality of tomographic planes is set using the frame image storage unit, a panoramic tomographic image on the set tomographic plane is generated, the path of the X-ray beam passing through the pixel column in the vertical direction in the panoramic tomographic image is obtained, and based on the path of the X-ray beam, considering the spread of the X-ray beam in the vertical direction, for each pixel column in the vertical direction, the height of the pixel column in the vertical direction is corrected according to the position of the tomographic plane, and a series of arithmetic processes of sequentially arranging the pixel column with the corrected height on the corresponding tomographic plane set on the virtual three-dimensional space are executed while sequentially changing the tomographic plane for all the set tomographic planes to generate a pseudo 3D volume image. A pseudo 3D volume image generation unit. In the pseudo 3D volume image, obtain the path of the X-ray beam passing through the pixel column in the vertical direction on the reference cross-section, obtain the pixels on the cross-section formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the path of the X-ray beam, integrate the pixel values of each pixel having the same height on the cross-section, and replace the pixel value of the corresponding pixel on the reference cross-section with the value obtained by averaging the integrated pixel values. Execute this process for all pixel columns in the vertical direction on the reference cross-section, and generate a panoramic tomographic image using the replaced pixels on the reference cross-section. A panoramic tomographic image generation unit; The panoramic X-ray tomographic image generation apparatus according to claim 1, characterized by comprising the above.

5. Comprising a 3D image storage unit that stores an aggregate of a plurality of the panoramic tomographic images as a 3D image in a virtual 3D space; The panoramic X-ray image generation unit With any one of one or more standard cross-sections as the reference cross-section, using the reference cross-section, the stack thickness information, and the distance information between the cross-sections, a plurality of cross-sections are set at predetermined intervals on the virtual 3D space of the 3D image storage unit. Set one of the plurality of cross-sections using the frame image storage unit, generate a panoramic tomographic image on the set cross-section, obtain the path of the X-ray beam passing through the pixel column in the vertical direction in the panoramic tomographic image, and based on the path of the X-ray beam, considering the spread of the X-ray beam in the vertical direction, for each pixel column in the vertical direction, correct the height of the pixel column according to the position of the cross-section, and sequentially arrange the pixel columns with corrected height on the corresponding cross-sections set on the virtual 3D space. A pseudo 3D volume image generation unit that generates a pseudo 3D volume image by executing a series of arithmetic processes for all the set cross-sections while sequentially changing the cross-sections; Based on a large number of frame image data obtained by one panoramic shooting, generate a plurality of panoramic tomographic images with different shift amounts of the frame image data corresponding to a plurality of cross-sections, and extract the autofocus cross-section, which is the cross-section with the best focus of the subject, by frequency analysis processing. An autofocus unit; In the pseudo 3D volume image, obtain the path of the X-ray beam passing through the pixel column in the vertical direction on the autofocus section plane, obtain the pixels on the section plane formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the path of the X-ray beam, integrate the pixel values of each pixel having the same height on the section plane, and replace the pixel value of the corresponding pixel on the autofocus section plane with the value obtained by averaging the integrated pixel values. Execute this process for all the pixel columns in the vertical direction on the autofocus section plane, and generate a panoramic tomographic image using the replaced pixels on the autofocus section plane. A panoramic tomographic image generation unit; The panoramic X-ray tomographic image generation apparatus according to claim 1, characterized by comprising the above.

6. Comprising a 3D image storage unit that stores an aggregate of a plurality of the panoramic tomographic images as a 3D image in a virtual 3D space. The panoramic X-ray image generation unit Based on a large number of frame image data obtained by one panoramic photographing, generate a plurality of panoramic tomographic images with different shift amounts of the frame image data corresponding to a plurality of section planes, and extract, by frequency analysis processing, an autofocus section plane that is the section plane with the best focus of the subject. An autofocus unit; With the autofocus section plane as the reference section plane, using the autofocus section plane, the stack thickness information, and the distance information between the section planes, set a plurality of section planes at predetermined intervals on the virtual 3D space of the 3D image storage unit, set one of the plurality of section planes using the frame image storage unit, generate a panoramic tomographic image on the set section plane, obtain the path of the X-ray beam passing through the pixel column in the vertical direction in the panoramic tomographic image, and for each pixel column in the vertical direction, considering the spread of the X-ray beam in the vertical direction based on the path of the X-ray beam, correct the height of the pixel column according to the position of the section plane, and sequentially arrange the pixel columns with corrected height on the corresponding section plane set on the virtual 3D space. By sequentially changing the section planes and executing this series of arithmetic processes for all the section planes to be set, a pseudo 3D volume image is generated. A pseudo 3D volume image generation unit; Obtain the path of the X-ray beam passing through the pixel columns in the vertical direction on the autofocus cross-section in the pseudo 3D volume image, obtain the pixels on the cross-section formed by cutting the pseudo 3D volume image with a vertical plane that coincides with the path of the X-ray beam, integrate the respective pixel values of the pixels having the same height on the cross-section, and replace the pixel value of the corresponding pixel on the autofocus cross-section with the value obtained by averaging the integrated pixel values. Execute this process for all the pixel columns in the vertical direction on the autofocus cross-section, and generate a panoramic tomographic image using the replaced pixels on the autofocus cross-section. A panoramic tomographic image generation unit The panoramic X-ray tomographic image generation apparatus according to claim 1, characterized by comprising

7. The panoramic X-ray tomographic image generation apparatus according to any one of claims 1 to 6, An X-ray generator that irradiates the fan-shaped X-ray beam, An X-ray detector that detects the X-ray transmitted through the subject, The swivel arm that holds the X-ray generator and the X-ray detector, A swivel movement device having a motor that drives the swivel arm, Control means for controlling the drive of the swivel arm, Control means for controlling the drive of the X-ray generator, Control means for controlling the drive of the X-ray detector, A panoramic X-ray tomographic imaging apparatus, characterized by comprising

8. A program for causing a computer to function as the panoramic X-ray tomographic image generation apparatus according to any one of claims 1 to 6.

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