JP2005021661A - Tomographic x-ray equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize locating of a photographic position where exposure is reduced, concerning a tomographic X-ray equipment X-irradiating conically. <P>SOLUTION: The equipment comprises: an X-ray photographic means to photograph an examinee by a detector located opposite to an X-ray source; a scanner rotating means to rotate the X-ray source and the detector around the examinee; an examinee displacing means to displace the examinee; a collimator means to changeably restrict extent of X-ray irradiation; a reconstructional calculation means to produce an X-ray 3 dimensional reconstructed image from a profile view photographed by the X-ray photographic means; a visible light photographic means which is placed on the rotation means and photographs the examinee; and a reconstructional calculation means to reconstruct a visible light 3 dimensional image from a result of photography by the visible light photographic means, in an image processor. The equipment comprises: a correction phantom used for calculating rotational centers in the X-ray photography system and the visible light photography system; a rotational center calculating means to calculate the rotational centers in the x-ray and visible light photography systems from excursion of rotational photography, with the correction phantom; and a coordinate converting means to overlap the coordination system of the X-ray photography system on the coordination system of the visible light photography system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an X-ray tomography apparatus that irradiates X-rays in a conical shape, and realizes positioning of an imaging region with a new technique of using a visible light imaging apparatus and its imaging results.

  As shown in FIG. 23, the X-ray tomography apparatus is a measurement device that captures a two-dimensional X-ray image (projection image), an image processing device that stores the projection image and reconstructs the tomogram, and an image display that displays the image It consists of a device and an external input device for inputting information such as characters.

  The processing of the conventional X-ray tomography apparatus will be described with reference to the drawings. In the figure, 1 is a scanner, 11 is an X-ray tube, 12 is a two-dimensional detector, 19 is a scanner drive means, 2 is a collimator, 29 is a collimator drive means, 3 is a chair, 31 is a chair supporter, 39 is a chair drive Means, 4 is an image processing unit, 41 is an I / F, 42 is a memory, 43 is a hard disk, 44 is a CPU, 5 is a display device, 6 is an external input device, and 7 is a subject.

  The scanner 1 is arranged so that the X-ray tube 11 and the two-dimensional detector 12 face each other with the subject 7 interposed therebetween, as shown in the figure. The X-ray tube 11 irradiates the subject 7 with a conical X-ray from the X-ray focal point, and the two-dimensional detector 12 detects the fluoroscopic image data by detecting the intensity of the X-ray transmitted through the subject 7. To get. The X-ray tube 11 and the two-dimensional detector 12 are configured to rotate about the body axis of the subject about the center of rotation. Each time the X-ray tube 11 and the two-dimensional detector 12 are rotated by a minute angle, the X-ray tube 11 is irradiated with a conical X-ray, and the intensity of the X-ray transmitted through the subject 7 is measured by the two-dimensional detector 12. Detected. This operation is repeated for the entire circumference, and as a result, hundreds to several hundreds of transmitted X-ray intensity data are collected as the fluoroscopic image data.

The transmitted X-ray intensity data measured by the two-dimensional detector is converted into a digital signal and then sent to the image processing unit 4.
Transmitted X-ray intensity data (hereinafter referred to as a projected image) sent from the measurement unit is temporarily stored in the memory 42 in the figure, and then stored in the hard disk 43. In this way, the projection image is saved.

When displaying a projection image, the projection image stored in the hard disk 43 is read out to the memory 42, and the read data is displayed on the display device 5.
When correcting the projection image, the projection image stored in the hard disk 43 is read out to the memory 42, and the CPU 44 corrects the disturbance of the projection image caused by the sensitivity unevenness of the detector. The corrected projection image is reconstructed.

In the filtering process, the entire projection image is corrected using a correction filter such as a well-known Shepp-Logan filter in the CPU 44.
In the three-dimensional reconstruction calculation, the three-dimensional X-ray absorption coefficient distribution in the area where the subject 8 is displayed is reconstructed in the CPU 44 from the projection image obtained by performing the above-described processing, and 3 Create a dimensional reconstruction image. As a reconstruction calculation method, a cone beam reconstruction calculation based on the well-known Feldkamp method is known.

The three-dimensional reconstructed image can be stored in the hard disk 43 or the like. When displaying the three-dimensional reconstructed image, the three-dimensional reconstructed image stored in the hard disk 43 or the like is read out to the memory 42 and the data read out to the memory 42 is displayed on the display device 5. In the reprojection calculation, the three-dimensional reconstructed image stored in the hard disk 43 shown in FIG. 1 is read into the memory 42, and the CPU 44 performs the reprojection calculation disclosed in, for example, [Patent Document 1] to perform the three-dimensional reprojection. Create an image.
The three-dimensional reprojection image is stored in the hard disk 44, and in order to display it, it is read from the hard disk 44 to the memory 42 and displayed on the display device 5.

In the conventional technique, before performing reconstruction as described above, a so-called scan plan is generally performed in which an imaging range is planned using a projection image or the like. The scan plan includes, for example, a scanogram in which an X-ray tube and a detector are fixed at an arbitrary position without rotating, and X-rays are irradiated toward a subject while moving a bed to obtain a projection image.
Since this method can obtain an X-ray projection image, there is a merit that it is possible to perform a scan plan for a site that is difficult to confirm from outside the body of the subject, but it involves exposure by X-rays. There was a risk.

  In the X-ray scanning plan of the prior art, imaging is performed according to the following procedure. In other words, the examinee is first positioned on a chair or bed, and the examiner often performs remote positioning based on experience and intuition and performs fluoroscopy. The examiner repeatedly performs fine adjustment while confirming the fluoroscopic image. In many cases, fine adjustment is performed by seeing through three sets of arm rotation angles 0 °, 90 °, and 0 ° to adjust whether the desired area is included in the imaging range in the vertical and horizontal positions. In order to accurately obtain the position by the fine adjustment, the examiner is required to have experience and intuition, and the subject is forced to be exposed.

[Patent Document 2] describes that in the CT scanner, the movement of the bed is controlled using the two-dimensional imaging result of the video camera. However, it is used for the control of the bed feeding of the CT scanner, and does not disclose the idea of accurately specifying the X-ray imaging part by imaging the imaging part with visible light and configuring it three-dimensionally as in the present invention. .
In the three-dimensional reconstruction calculation, methods for accurately obtaining the rotation center of the X-ray imaging system are described in [Patent Document 3] and [Patent Document 4].

Japanese Patent Laid-Open No. 9-253079 JP-A-81-263838 Japanese Unexamined Patent Publication No. 9-17330 JP 2000-201918

An object of the present invention is to provide an X-ray tomography apparatus and an X-ray tomography method that can easily realize an accurate scan plan even if the experience and intuition are not abundant while preventing exposure of the subject by X-rays. It is to provide.
In addition, when the above apparatus is provided, it is possible to grasp an accurate geometric relationship between the visible light imaging system and the X-ray imaging system.

  According to the first feature of the present invention, an X-ray imaging unit that irradiates an X-ray from an X-ray source and images a subject by a detector disposed opposite the X-ray source, and the X-ray source And a scanner rotating means for rotating the detector around the subject, a subject moving means capable of moving the subject, and a collimator means for variably limiting the X-ray irradiation range, In an X-ray tomographic diagnosis apparatus having an image processing apparatus for generating an X-ray three-dimensional reconstructed image from a projection image photographed by the X-ray photographing means by a reconstruction calculating means, the subject placed on the rotating means and the subject The X-ray tomography apparatus is further provided with a visible light imaging unit for imaging the image, and the image processing apparatus reconstructs a visible light three-dimensional image from the imaging result of the visible light imaging unit. More preferably, the visible light photographing means is accompanied by illumination means for illuminating the subject.

  According to a second feature of the present invention, the visible light photographing means performs photographing in synchronization with the rotation angle of the scanner rotating means. X-ray tomography according to the first feature of the present invention, A photographing apparatus is provided.

  According to a third feature of the present invention, the image processing apparatus uses the visible light photographing means and the scanner rotating means, and the mask image photographed when the subject is not in the photographing range, and the subject From the live image photographed when the examiner is in the photographing range, a rotation photographed image obtained by extracting the contour of the subject is generated, and the visible light three-dimensional reconstructed image is further generated based on the contour extraction rotation photographed image. The X-ray tomography apparatus described in the first feature of the present invention is characterized in that

  According to a fourth feature of the present invention, the image processing device superimposes an X-ray three-dimensional reconstruction image region on a visible light three-dimensional projection image created based on the visible light three-dimensional reconstruction image. An X-ray tomography apparatus according to the first feature of the present invention is characterized by displaying.

  According to a fifth feature of the present invention, the image processing device displays an anatomical model such as a skeleton on a visible light three-dimensional projection image created based on the visible light three-dimensional reconstructed image. An X-ray tomography apparatus according to the first feature of the present invention is provided.

  According to the sixth aspect of the present invention, there is no parallax between the visible light imaging means and the X-ray source, that is, the optical axis of the visible light imaging means is interposed on the optical axis of the collimator means. An X-ray tomography apparatus according to the first feature of the present invention is provided.

  According to a seventh aspect of the present invention, the parallax between the optical axis of the X-ray source and the optical axis of the visible light photographing means is eliminated by a combination of the visible light photographing means and the scanner rotating means. The X-ray tomography apparatus according to the first feature of the present invention, characterized in that

  According to an eighth aspect of the present invention, the apparatus further comprises chair driving means for adjusting the position of the chair, scanner driving means for moving the X-ray tube and the X-ray detector, whereby the visible light photographing means and the The first aspect of the present invention is characterized in that the parallax between the optical axis of the X-ray source and the optical axis of the visible light photographing means is eliminated by adjusting the relative position with the subject moving means. The X-ray tomography apparatus described in 1. is provided.

  According to a ninth feature of the present invention, in the first feature of the present invention configured to obtain a scanogram image by visible light by the visible light photographing means while rotating the scanner by the subject moving means. An X-ray tomography apparatus is provided.

According to a tenth feature of the present invention, there is provided an X-ray tomography apparatus characterized in that the image processing device can display the visible light three-dimensional image and the fluoroscopic three-dimensional image in a superimposed manner.
According to the eleventh feature of the present invention, a correction phantom used for calculating the rotation center of the X-ray imaging system and the visible light imaging system, and an X-ray imaging system and a visible light imaging system from a trajectory obtained by rotating the correction phantom The rotation center calculating means for calculating the rotation center of the X-ray imaging system and a coordinate conversion means for superimposing the coordinate system of the X-ray imaging system on the coordinate system of the visible light imaging system according to the first feature of the present invention. An X-ray tomography apparatus is provided.

   According to the twelfth feature of the present invention, the correction phantom includes a transparent support material that does not absorb X-rays or has a small X-ray absorption coefficient and low visible light absorption, and a large X-ray absorption coefficient and visible light. The eleventh feature of the present invention is composed of at least two or more reference points that have a large light absorption and a clear contrast with the transparent support material, and a reference point can be distinguished from other reference points. An X-ray tomography apparatus is provided.

  According to the thirteenth feature of the present invention, the support material is a material that absorbs less X-rays and visible light, such as transparent acrylic, and has a rod shape, and the reference point is attached along the axial direction of the support material. An X-ray tomography apparatus according to an eleventh aspect of the invention is provided.

  According to a fourteenth feature of the present invention, the reference point is a material having a large X-ray absorption coefficient, such as tungsten, platinum, or an iron-nickel-chromium alloy, and is visible with respect to the transparent support material. An X-ray tomography apparatus according to the eleventh feature of the present invention is provided, which is composed of a sphere with a black color that makes the contrast clear or a color scheme that facilitates color recognition.

  According to a fifteenth feature of the present invention, the rotation center calculating means is a visible light reference point extracting means for extracting the reference point for each of a plurality of images obtained by rotating and photographing the correction phantom in a visible light photographing system, Image adding means for adding a plurality of images from which the reference points have been extracted to create a single added image, and elliptic trajectory extracting means for extracting a plurality of ellipses drawn by the reference points photographed in the added image And a center position calculating means for calculating the center position of the major axis and the minor axis of the elliptical locus, a straight line calculating means for calculating a straight line passing through each of the center positions by the least square method, and the straight line means. Calculate the coordinate value of the intersection of the ellipse with the straight line connecting the center of the elliptical trajectory, and consider the line connecting the point of the coordinate value as the short axis of each ellipse. X according to the eleventh feature of the present invention for calculating the position of A line tomography apparatus is provided.

According to a sixteenth feature of the present invention, there is provided the X-ray tomography apparatus according to the eleventh feature of the present invention, wherein the rotation center calculating means is effective even in an X-ray imaging system.
According to a seventeenth feature of the present invention, the coordinate conversion means is arranged between a reference point and a rotation center axis in an X-ray coordinate system and a visible light photographing system with respect to a reference point on the correction phantom. X-ray tomography according to the eleventh feature of the present invention, which measures the distance of, calculates the magnification of the X-ray coordinate system relative to the visible light coordinate system, and calculates the X-ray imaging system rotation center coordinates in the visible light imaging system A photographing apparatus is provided.

  Since the imaging position and the collimator 2 can be set using the image from the camera 8 arranged in the scanner 1, the X-ray exposure of the subject 7 in the scan plan can be removed. Since there is no X-ray exposure in this way, it is possible to perform fine adjustment by repeatedly setting the imaging position and collimator without resistance. Since real-time images are used even when fine adjustment is repeatedly performed, accurate and reliable positioning can be performed without loss of time. In addition, even if the image size is small, a wide-angle camera can be used to construct a three-dimensional visible light reprojection image, so that the imaging range can be determined without being greatly affected by the inspector's proficiency without relying on experience or intuition. .

  Because this method can obtain the conversion processing parameters between the coordinates of the X-ray imaging system and the coordinates of the visible light imaging system, positioning using the camera is possible, and as a result, the X-ray of the subject 7 in the scan plan Exposure can be removed. Even when the X-ray imaging system and the visible light imaging system have completely different rotational planes, this method enables positioning using a camera. For this reason, even if the image size of the X-ray imaging system is small, a wide-angle camera can be used to construct a three-dimensional visible light reprojection image, so that it can be taken without greatly affecting the proficiency of the examiner without depending on experience and intuition. The range can be determined.

(Example 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of the hardware configuration of the X-ray tomography apparatus of the present invention. In this example, a sitting X-ray diagnostic apparatus for imaging the head and neck is shown, but the X-ray tomography apparatus may be a C-arm type apparatus, a CT apparatus, a subject rotation type apparatus, or the like.

  In the figure, 1 is a scanner, 11 is an X-ray tube that emits X-rays, 13 is a detector that detects irradiated X-rays, 17 is a scanner support, and 18 is a scanner that substantially matches the body axis of the subject. Rotating shaft, 19 is a scanner driving means, 2 is a collimator for limiting the X-ray range to be irradiated, 29 is a collimator driving means, 3 is a chair, 31 is a chair supporter, 39 is a chair driving means, 4 is an image processing unit, 41 Is an interface I / F for inputting / outputting an X-ray projection image and a visible light photographing image and communicating with the scanner driving means 19, the chair driving means 39, and the collimator driving means 29, 42 is a memory for storing image data, 43 is an arithmetic operation Hard disk that stores image data necessary for processing, 44 is a CPU that performs arithmetic processing, 5 is a display device, 6 is an external input device, 7 is a subject, 8 is a camera that captures visible light and does not cause exposure, 9 Indicates lighting. The measuring device is constituted by these.

FIG. 2 is a diagram showing the arrangement of the camera 8 and the illumination 9 with respect to the scanner 1 in the measuring apparatus shown in FIG. The camera 8 is disposed at a position shifted from the focal point of the X-ray tube 11 by an angle t about a scanner rotation axis 18 that substantially coincides with the body axis of the subject 7. When the scanner 1 is rotated by an angle t, a visible light image from the same rotation angle as the image viewed from the focal position of the X-ray tube 11 can be obtained by the camera 8. Further, by illuminating the illumination 9 from the camera 8 side, it is possible to always obtain an image with little shadow on the subject 7. Here, the illumination 9 used above is separate from the camera 8. However, in order to reduce shadows, a ring-shaped illumination attached around the lens of the camera 8 is desirable. In order to further reduce the shadow, it is possible to illuminate the subject from various directions using a plurality of light sources. Further, if a ring light and a plurality of light sources are used, it is possible to further reduce shadows.
The camera 8 takes a picture in synchronization with the rotation angle of the scanner 1. The subject 7 is rotated around 360 ° to obtain a plurality of angle-synchronized rotational images.

FIG. 3 is a diagram showing a process of generating a three-dimensional reconstructed image based on the rotation photographed image obtained by the camera 8. In a state where the subject 7 is not sitting on the chair, the camera 8 rotates and obtains a plurality of mask images. When taking a mask image, the chair 3 is moved to a predetermined position. A plurality of the predetermined positions can be set in accordance with, for example, the difference in the physique between the child and the adult, and the parts such as the head, tooth and jaw, and neck.
Further, the shooting range by the camera 8 is wider than that of the X-ray projection image, and a wide field of view including the X-ray projection image is shot. Alternatively, the shooting range of the camera 8 can be enlarged or reduced according to the situation.

The mask image does not need to be taken every time before the subject 7 is photographed, and the rotated image photographed at the predetermined position is stored in the hard disk 43 in the image processing apparatus. Accordingly, it can be expanded in the memory 42 and used for image processing.
The subject 7 is seated on the chair, and the position of the chair 3 is moved by the chair driving means 39 in accordance with the physique and part of the subject 7. Then, while the subject 7 is sitting on the chair 3, the camera 8 takes a picture while rotating the scanner support 14 to obtain a plurality of live images.

  Next, in order to extract the subject 7 from the live image, first, an image is created by subtracting a plurality of mask images and the live image for each angle. The mask image used here is taken at the same position as the position of the chair 3 in the live image. If the image obtained by the camera 8 is in color, it is mapped in gray scale and converted to monochrome display before performing the difference. In addition, since an image matrix of 128 × 128 pixels or less is sufficient, in the case of a camera capable of obtaining a large image matrix, pixels are regularly thinned and used.

Since the background of the chair 3 and the detector 13 other than the subject 7 is the same between the mask image and the live image, the pixel values of the background other than the subject are almost 0 in these difference images. For this reason, for example, a region having a pixel value other than ± 20 is extracted as the subject extraction region. A subject-extracted image is generated in which the pixel value of the subject extraction region is 1 and the background pixel value other than the subject extraction region is 0.
Here, it is preferable that the chair 3 is as small as possible in order to obtain a sufficient image from the rear of the imaging region of the subject 7. For example, when photographing a tooth and jaw part, it is desirable that the headrest and the portion supporting it are made as narrow as possible so that the subject extracted image can be sufficiently generated. More preferably, a more complete subject extraction image can be obtained if the headrest and the portion supporting it are made of a transparent material.

  Based on a plurality of subject extraction images obtained by rotational imaging, a cone beam reconstruction calculation by the well-known Feldkamp method is executed in the CPU 44 to create a visible light three-dimensional reconstruction image. The visible light three-dimensional reconstruction image is stored in the hard disk 43 shown in FIG.

  In the three-dimensional reconstructed image display, the visible light three-dimensional reconstructed image stored in the hard disk 43 by the above three-dimensional reconstructed image storage is read to the memory 42 shown in FIG. 1, and the data read to the memory 42 is displayed on the display device Display in 5. In the reprojection calculation, the visible light three-dimensional reconstructed image stored in the hard disk 43 is read into the memory 42, and the reprojection calculation is performed in the CPU 44 by, for example, the reprojection calculation means disclosed in [Patent Document 1], so that the visible light is visible. Create an optical 3D reprojection image. Hereinafter, the reconstructed image basically means a tomographic image of the subject, and the reprojected image indicates a three-dimensional image constructed from the reconstructed image.

  Further, based on the live image and the subject extracted image, a subject extracted live image is generated by replacing the background of the subject of the live image with a blue screen or the like. A plurality of subjects extracted live images can be texture-mapped on the surface of the subject of the three-dimensional reprojection image to obtain a color three-dimensional projection image of the subject.

  FIGS. 4 and 5 are diagrams showing that a fluoroscopic reconstructed image region by X-rays is superimposed on the visible light three-dimensional projection image. The visible light 3D reconstruction image is generated based on the position of the rotation center axis of the scanner on the camera image, the geometric distance between the camera and the rotation center axis, the pixel size, etc. The geometric position of the scanner 1 and the camera 8 such as the rotation center axis, rotation surface, and rotation center of the scanner can be reproduced on the 3D reprojected image.

In addition, these geometric positions are determined by the X-ray three-dimensional reconstructed image and the perspective three-dimensional reprojected image obtained by the X-ray obtained by the X-ray tube 11 and the detector 13 arranged on the same scanner. Can be matched with the target position.
The center position of rotation of the scanner 1 on the visible three-dimensional projection image can be rotated by mechanically adjusting the installation position of the camera 8 with respect to the installation positions of the X-ray tube 11 and the detector 13 or by correcting with software. It is also possible to match the geometric positions of the surface and the center of rotation.

  The fluoroscopic three-dimensional reprojection image area by X-ray differs depending on the shape of the detector 13. When the detector 13 is circular like an image intensifier, the perspective three-dimensional reprojection image region is spherical. In addition, when the detector 13 is rectangular like a flat panel, the perspective three-dimensional reprojection image area is cylindrical. Since the perspective 3D projection image area is determined by the geometrical conditions and reconstruction conditions on the scanner, reconstruction area information corresponding to the shape and size of the detector can be modeled without having to shoot every time. Hold as.

  The subject's visible 3D reprojection image generated based on the camera image and the X-ray perspective 3D reprojection image area model are superimposed as shown in Fig. 4 and Fig. 5. By displaying the image, it is possible to express as an image which region of the subject body 7 that is currently sitting can be re-projected in a three-dimensional manner with X-rays. The operator can check these superimposed images using the display device of FIG.

FIG. 6 is a diagram showing the relative movement between the camera system coordinate system and the X-ray measurement system coordinate system.
If the X-ray fluoroscopic three-dimensional reprojection image area model does not include the part to be measured by the subject 7, operate the external input device in FIG. The model and the visible light three-dimensional reprojection image of the subject generated based on the camera image are relatively moved and adjusted. In FIG. 6, by moving the X-ray measurement system coordinate system in the front direction of the subject with respect to the camera measuring instrument coordinates, the entire tooth jaw of the subject is included in the three-dimensional reprojection image area by X-rays It shows that it was set as follows. The movement amount of the X-ray measurement system coordinate system with respect to the camera measurement system coordinate system is reflected in the chair driving means 39 shown in FIG.

FIG. 7 is a diagram showing a change in the visual field size of the detector.
When changing the perspective three-dimensional reprojection image area by X-ray, operate the external input device in Fig. 1 to change the perspective three-dimensional reprojection image area model by X-ray to make a more appropriate three-dimensional reprojection Specifies the image area. FIG. 7 shows the result of selecting a region model that is larger than FIG. By selecting a wide area model, a wider range of 3D reprojection images can be obtained. In addition, by selecting a small area model, it is possible to obtain an image of only the part of interest in detail and to suppress exposure of the subject. This change in the perspective three-dimensional reprojection image region model by X-rays is reflected in the position and size change of the detector 13 shown in FIG.

FIG. 8 is a diagram showing a change of the visual field size by the collimator 2.
When changing the perspective three-dimensional reprojection image region by X-ray, the external input device 6 in FIG. 1 is operated to change the position of the blade of the collimator 2 and specify the perspective three-dimensional reprojection image region. FIG. 8 shows the result of reflecting the result of limiting the vertical visual field by the collimator 2 in the area model. The collimator 2 can be set while confirming the region where the exposure of the subject 7 is restricted by the collimator 2.
FIG. 6 shows the result of selecting a region model that is larger than FIG. By selecting a wide area model, a wider range of 3D reprojection images can be obtained.
The change of the visual field size is set by operating the collimator 2 via the collimator driving means 29.

FIG. 9 is a diagram showing that an anatomical model such as a skeleton is superimposed on the visible light three-dimensional projection image. The visible light 3D projection image from the camera 8 is different from the X-ray perspective 3D projection image because it does not have internal information. By fusing the images, it can be used as a guide for adjusting the reconstruction area.
In order to fuse the skull and the forehead model to the visible light 3D projection image by the camera, the head model can be template-matched to the visible light 3D projection image by the camera. There are methods such as template matching of fluoroscopic three-dimensional projection images using X-rays.

FIG. 10 is a diagram showing the measurement apparatus of the present embodiment according to the present invention, and shows a case where there is a vertical shift of a distance s between the focal point of the camera 8 and the focal point of the X-ray tube 11.
The focal point of the camera 8 is shifted from the focal point of the X-ray tube 11 in the upward direction of the rotation axis 18 by a distance s. When the chair 3 is moved upward by a distance s, a visible light image having the same parallax as the image viewed from the focal position of the X-ray tube is obtained by this camera. At this time, the rotation angle around the scanner rotation axis 18 is the same.
When photographing with X-rays, the position of the chair 3 is moved downward by the same distance s.
For example, when setting an X-ray imaging region on a visible light three-dimensional projection image, it is possible to move the X-ray imaging region as shown in FIGS. It will be necessary to consider parallax.

  11 and 12 are diagrams showing an example of the arrangement of the X-ray tube 11, the collimator 2, and the camera 8 in the configuration of the measuring apparatus shown in FIG. X-rays are emitted from the focal point 111 of the X-ray tube 11 toward the radiation port 112. The irradiation range of the X-rays irradiated from the radiation port 112 is narrowed by the collimator 2. A mirror 113 is disposed between the radiation port 112 and the collimator 2, and the focal point 81 of the camera 8 is disposed at a position that is a mirror image target of the focal position of the X-ray tube with respect to the mirror surface. The mirror may be a half mirror. In this way, it is also possible to arrange the optical axis of the camera and the focus of the X-ray tube. In this case, since the imaging result of the camera 8 is a mirror image, it is necessary to invert the image in the CPU 4 or the like in order to match the imaging result with the X-ray. In the case of the configuration of FIG. 12, parallax does not occur between the optical axis of the camera 8 and the X-ray focal point 111 to the X-ray optical axis along the radiation port 112. It is not necessary to correct the amount of parallax for the scan plan, and the cost can be reduced while improving the processing speed.

  Although the present embodiment has been described mainly for dental CT that performs imaging of the tooth and jaw, the present invention relates to a CT apparatus, an X-ray C arm apparatus, a surgical X-ray C arm apparatus, and a mobile X-ray C. Needless to say, it can also be used for arm devices. In this case, in particular, the CT apparatus and the X-ray C arm apparatus can effectively implement the present invention by using a transparent bed or chair.

  Prior art X-ray scanning plans place the subject on a chair or bed, and the inspector often relies on experience and intuition to remotely position and see through, see through the fluoroscopic image. Make fine adjustments repeatedly. In many cases, fine adjustment is performed by seeing through three sets of arm rotation angles 0 °, 90 °, and 0 ° to adjust whether the desired area is included in the imaging range in the vertical and horizontal positions. In order to accurately obtain the position by the fine adjustment, the examiner needs experience and intuition, and the subject is forced to be exposed. On the other hand, in this application, the rough positioning in the said prior art becomes unnecessary, and it can respond by switching the height of a chair into about three steps according to the physique of a subject. This can be realized because the field angle of the visible light camera can be made much wider than the X-ray fluoroscopic range. Here, the height of the three-stage chair is, for example, a man, a woman, or a child.

  In the present application, the fluoroscopy and fine adjustment in the above conventional example can be replaced by rotational shooting with visible light, image reconstruction, and three-dimensional reprojection, and can be operated remotely.Rotary shooting is usually 5 seconds per rotation, reconstruction is Since it takes about 60 seconds and 3D reprojection takes about 30 seconds, it can be executed in the same or shorter time as a conventional X-ray scan plan. In the past, X-ray imaging range was fine-tuned based on experience and intuition, but it is also possible to automatically set the X-ray imaging range on the visible light 3D projection image using a CPU, etc. X-ray imaging range can be determined without any loss.

(Example 2)
Example 2 will be described below.
The configuration of the second embodiment is basically the same as that of the first embodiment, and has the configuration shown in FIG.
Unless otherwise noted, the same reference numerals represent the same parts.
FIG. 2 is a diagram showing the measurement apparatus according to the present embodiment of the present invention, and shows a case where there is a vertical shift of a distance s between the focal point of the camera 8 and the focal point of the X-ray tube 11.
The focal point of the camera 8 is shifted from the focal point of the X-ray tube 11 in the upward direction of the rotation axis 18 by a distance s. In such an arrangement, the visible light imaging system and the X-ray imaging system have rotational angle positions. Moreover, since it is fixed to the same scanner, it shares the same rotation center axis. However, since the mounting positions are different in the height direction, each has a different plane of rotation. Also, the visual field range and the image matrix are different.

  FIG. 13 is a diagram illustrating the relationship between the visible light imaging system and the X-ray imaging system. In FIG. 2, the camera is disposed above, and the visible light photographing system located above is indicated by a broken line. On the other hand, the X-ray imaging system located below is indicated by a solid line. Here, z and z 'are the rotation center axes of the scanner, and coincide with each other in the visible light imaging system and the X-ray imaging system. The rotation plane is different between the visible light imaging system and the X-ray imaging system, the visible light imaging system is represented by the x′-y ′ plane, and the X-ray imaging system is represented by the xy plane. The image plane rotating around the rotation center axis perpendicular to the rotation plane is represented by the u′-v ′ plane in the visible light imaging system and the u-v plane by the X-ray imaging system. The mapping of the rotation axis (Center axis) and rotation plane (Mid plane) onto the image plane is expressed as coordinates on the image plane, and the rotation center of the visible light imaging system is represented by (c ', m'). The rotation center of the X-ray imaging system is represented by (c, m). Note that the correction phantom is shifted from the center of rotation, and the correction phantom at the same position is imaged by the visible light imaging system and the X-ray imaging system.

FIG. 14 is a diagram illustrating photographing of the correction phantom in the visible light photographing system. FIG. 16 is a diagram illustrating a correction phantom image captured by a visible light imaging system. Support material and reference point can be confirmed.
FIG. 15 is a diagram showing imaging of the correction phantom in the X-ray imaging system. FIG. 17 is a diagram showing a correction phantom image captured by an X-ray imaging system. Support material and reference point can be confirmed.
FIGS. 16 and 17 are both correction phantom images taken from the same angle direction. However, as shown in FIGS. 13 to 15, since the images were taken while rotating around the correction phantom, the images were taken from all angle directions. A correction phantom image is acquired. The images shown in FIGS. 18 and 19 are obtained by adding the correction phantom images from all the angles. The locus of the reference point by rotating shooting is displayed as an ellipse. The line connecting the midpoints of the major axis of this ellipse is the center axis of rotation, the minor axis is plotted at the intersection of each major axis on the center axis of rotation, and the coordinate where the minor axis is 0 is the plane of rotation. These are the rotation centers (c ′, m ′) and (c, m) determined by the intersection of the rotation center axis and the rotation surface. The method for obtaining the details of the rotation center is described in [Patent Document 3].

  20 and 21 are conceptual diagrams showing the calculated rotation center coordinates in a correction phantom image captured by a visible light imaging system and an X-ray imaging system. The coordinates (p ′, q ′) and (p, q) of an arbitrary reference point that can be specified on the image of the correction phantom are obtained from the center of gravity of the pixel luminance. From the coordinates (p ′, q ′) and (p, q) of the reference point, the distances of the perpendiculars drawn to the rotation center axis are given by | p′−c ′ | and | p−c |, respectively. Thus, the magnification ratio | p−c | / | p′−c ′ | of the visible light imaging system with respect to the X-ray imaging system is obtained.

FIG. 22 is a conceptual diagram showing the positional relationship by superimposing the correction phantom image captured by the visible light imaging system and the correction phantom image captured by the X-ray imaging system. It is also possible to actually superimpose a correction phantom image captured by an X-ray imaging system based on the identifiable reference point by multiplying by the magnification. Here, the v ′ coordinate M of the rotation center of the X-ray imaging system in the visible light imaging system is given by the following equation. M = q ′ − (q−m) · | p−c | / | p′−c ′ |.
Therefore, the 'coordinate' of the rotation center of the X-ray imaging system in the visible light imaging system is given by (c ', M).
Although the present embodiment has been described mainly for dental CT that performs imaging of the tooth and jaw, the present invention relates to a CT apparatus, an X-ray C arm apparatus, a surgical X-ray C arm apparatus, and a mobile X-ray C. Needless to say, it can also be used for arm devices. In this case, in particular, the CT apparatus and the X-ray C arm apparatus can effectively implement the present invention by using a transparent bed or chair.
It is also possible to improve the accuracy of conversion processing parameters by performing statistical processing using a plurality of reference points.

  By calculating the conversion processing parameters between the coordinate systems described above, the X-ray imaging system can be accurately positioned using the visible light imaging system camera. This calculation method also enables accurate positioning without depending on the mechanical accuracy of the X-ray tube and camera attachment. Further, the arrangement of the correction phantom is simple, and the correction parameters can be easily calculated.

The figure which shows the hardware constitutions of the measuring device by one Embodiment of this invention. The figure which shows about the arrangement | positioning of the camera and illumination with respect to the scanner by one Embodiment of this invention. The figure which shows the process of producing | generating a three-dimensional reconstruction image based on the rotation picked-up image obtained with the camera by one Embodiment of this invention. The figure which shows displaying the reconstruction image area | region by X-rays superimposed on one Embodiment of this invention. The figure which shows displaying the reconstruction image area | region by X-rays superimposed on one Embodiment of this invention. The figure which shows the relative movement of the camera coordinate system and X-ray measurement system coordinate system by one Embodiment of this invention. The figure which shows the change of the visual field size of the detector by one Embodiment of this invention. The figure which shows the change of the visual field size by the collimator by one Embodiment of this invention. The figure which shows displaying an anatomical model, such as a skeleton, in accordance with one Embodiment of this invention in piles. The figure which shows the measuring device by one Embodiment of this invention. The figure which shows the measuring device by one Embodiment of this invention. 4 shows an example of the arrangement of the X-ray tube 11, the collimator 2, and the camera 8 in the configuration of the measuring device according to the embodiment of the present invention. The figure which shows the relationship between the visible light imaging system and X-ray imaging system by the camera by one Embodiment of this invention. The figure which shows the relationship between the rotation center in the visible light imaging | photography system by one Embodiment of this invention, a rotation surface, the correction | amendment phantom, and a picked-up image. The figure which shows the relationship between the rotation center in the X-ray imaging system by one Embodiment of this invention, a rotation surface, the correction | amendment phantom, and a picked-up image. The figure which shows the picked-up image of the correction phantom in the visible light imaging | photography system by one Embodiment of this invention. The figure which shows the picked-up image of the correction phantom in the X-ray imaging system by one Embodiment of this invention. The figure which shows the addition process result of the picked-up image of the correction phantom in the visible light imaging | photography system by one Embodiment of this invention. The figure which shows the addition process result of the picked-up image of the correction phantom in the X-ray imaging system by one Embodiment of this invention. The figure which shows the relationship between the picked-up image of the correction phantom in the visible light imaging | photography system by one Embodiment of this invention, a rotation center, a rotation surface, and also a reference point. The figure which shows the relationship between the picked-up image of the correction | amendment phantom in the X-ray imaging system by one Embodiment of this invention, a rotation center, a rotation surface, and also a reference point. The figure which shows the relationship between the visible light imaging system and X-ray imaging system by one Embodiment of this invention. The figure which shows the measuring device by a prior art.

Explanation of symbols

  1 scanner, 2 collimator, 3 chair, 4 image processing unit, 5 display device, 6 external input device, 7 subject, 8 visible light camera, 9 illumination, 11 X-ray tube, 12, 13 detector, 17 scanner support 18 scanner rotation axis, 19 scanner drive means, 29 collimator drive means, 31 chair support, 39 chair drive means, 41 interface I / F, 42 memory, 43 hard disk, 44 CPU, 81 focus, 111 X-ray source center , 112 Radiation port, 113 mirror

Claims (3)

X-ray imaging means for irradiating an X-ray from an X-ray source and imaging the subject by a detector arranged opposite the X-ray source, and the X-ray source and the detector around the subject A scanner rotating means for rotating; a subject moving means capable of moving the subject; and a collimator means for variably limiting an X-ray irradiation range; An X-ray tomographic diagnosis apparatus having an image processing apparatus for generating an X-ray three-dimensional reconstructed image by a reconstruction calculation means, further comprising a visible light imaging means that is placed on the rotating means and images the subject. The X-ray tomography apparatus is characterized in that the image processing apparatus reconstructs a three-dimensional visible light image from the imaging result of the visible light imaging means. A correction phantom used for calculating the rotation center of the X-ray imaging system and the visible light imaging system, and a rotation center calculating means for calculating the rotation center of the X-ray imaging system and the visible light imaging system from a locus obtained by rotating the correction phantom. The X-ray tomography apparatus according to claim 1, further comprising coordinate conversion means for superimposing an X-ray imaging system coordinate system on a visible light imaging system coordinate system. The image processing apparatus uses the visible light photographing means and the scanner rotating means, and takes a mask image taken when the subject is not in the photographing range, and photographs when the subject is in the photographing range. 2. A rotation image obtained by extracting the contour of the subject from a live image is generated, and the visible light three-dimensional reconstructed image is generated based on the contour extraction rotation image. X-ray tomography apparatus according to claim 1.

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