JP2008188378A - X-ray tomographic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that both of arm rotary motion and rectilinear motion are taken place during X-ray irradiation, the rotary angle of the arm does not become a swing angle of a tomographic face and it is difficult to acquire a thin section-thickness tomographic image compared with the original tomographic image; and a TDI (Tissue Doppler Imaging) method is adopted, charges are transferred in the arm advancing direction and image signals are averaged to cause the lowering of the S/N ratio. <P>SOLUTION: This X-ray tomographic equipment is provided with an arm rotation section for rotating the arm by a prescribed angle using an irradiation object as a rotation center while irradiating X rays from an X-ray irradiation section, while the arm is rotated by the arm rotation part, charges are accumulated in respective pixels of an X-ray sensor according to the intensity of the X ray received by passing through the irradiation object, and after finishing the rotation, the accumulated charges are sequentially outputted as electric signals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray tomography apparatus for imaging a tomographic plane to be irradiated using an X-ray sensor, and more particularly to a dental X-ray tomography apparatus.

  In recent years, in order to see the internal structure that cannot be seen with the naked eye from the outside using X-rays, devices that convert light converted from X-rays into electric charges, such as CCDs, have been used from conventional methods using film. The method was changing. Particularly in the field of dental diagnosis, the development has been remarkable, and films have been widely replaced from small devices for oral cavity to panoramic photography and cephalo photography. Furthermore, the development of CT imaging continues, technologies that were impossible with conventional films are being realized, and new and useful diagnostic technologies are spreading.

  Under such circumstances, the desire to chew food with a sense that is as close to your teeth as possible, rather than dentures, has become stronger due to the social trend of spending as much as possible even as you become older. Suitable implant procedures are becoming widely practiced by ordinary dentists. For that purpose, it is necessary to accurately determine which part should be subjected to the implant, and therefore, a highly accurate and clear tomographic image is required.

  A photographed image in a normal dental panoramic apparatus has a considerable thickness because the thickness in the depth direction, that is, the tomographic thickness, needs to be photographed as a whole, and the tomographic thickness varies depending on the part to be photographed. In contrast, the implant procedure requires a tomographic image with a very thin thickness of about 1 mm, and requires a special imaging method that is different from a normal panoramic imaging method.

  This method of photography has been widely used in film photography, and X-ray photography is performed while rotating an irradiation device and a rotating arm with the film positioned so as to always face each other across the irradiation target. A tomographic image can be obtained. At this time, an image with a thin tomographic thickness can be obtained by increasing the rotation angle of the rotary arm called the swing angle.

  A technique for digital X-ray tomography by replacing a film with a sensor by such an imaging method has already been disclosed in Patent Document 1 and the like.

  In recent years, the development of CT apparatuses is also active, and a desired tomographic image can be obtained very easily by using the CT apparatus. If the image is obtained by CT, a considerable amount of information can be obtained at one time, so diagnosis is easy and there is little risk of imaging errors.

  However, this CT has a very large imaging device, requires a large installation area, and the above-mentioned X-ray sensor device such as a CCD is also required to have a fairly large area, so the cost of the device is extremely high. It still takes time to disseminate in general. Therefore, as described above, at present, a method of attempting tomography using a panoramic imaging device that is currently spreading all over the world is being implemented. Compared with an expensive device such as a large-area flat panel detector for CT, this device can be considerably cheap because it is a vertically long sensor.

  An example of the photographing method will be described with reference to FIGS.

  FIG. 9 is a diagram showing arm movement in the conventional X-ray tomography, and FIG. 10 shows arm movement, X-ray sensor drive signal, and X-ray irradiation timing in the conventional X-ray tomography. . Since the detailed operation of the device of the X-ray sensor is the same as that of the embodiment of the present invention, the details will be described later. Here, the outline of the movement of the arm and the X-ray sensor will be briefly described.

  In FIG. 9, an irradiation target 109 is horizontally long as shown in FIG. 9, and this rectangular portion is a tomographic plane to be obtained as a captured image. The X-ray irradiation unit 110 is an X-ray tube irradiation source, although not specifically illustrated. In the X-ray sensor 111, a plurality of pixels that emit an electric signal in response to the intensity of X-rays are arranged in a grid pattern. The X-ray irradiation unit 110 and the X-ray sensor 111 are arranged at positions that always face each other with the irradiation target 109 sandwiched between arms (not shown).

  In the conventional example, the arm is rotated in one direction by a predetermined angle from the start point 109a to the end point position 109b of the tomographic portion of the irradiation target 109.

  At the same time, the arm performs a linear motion while maintaining the locus so that the rotation center of the rotation is always at the position of the tomographic plane to be imaged. At this time, X-rays are continuously emitted from the X-ray irradiation unit 110, and the X-ray sensor 111 repeats charge accumulation, charge discharge, and charge transfer at a high speed at a speed according to the linear movement of the arm. As a result, a desired tomographic image can be obtained by a so-called TDI method in which only the target target portion can be photographed while moving the sensor.

  This will be described in more detail with reference to FIG. FIG. 10 is a diagram showing arm movement, X-ray sensor drive signal, and X-ray irradiation timing in the conventional X-ray tomography.

As shown in this figure, the straight arm movement, the arm rotation, and the X-ray irradiation start at the same timing and are continuously performed. In the meantime, charge accumulation and charge discharge are repeated at a high speed by the TDI method, and the discharged charges are sequentially transferred as an image signal, whereby a tomographic image in which only a desired tomographic portion can be clearly seen is obtained.
JP-A-10-2111200

  However, in the conventional X-ray tomography apparatus described above, since both the rotational motion and linear motion of the arm enter during X-ray irradiation, the irradiation range gradually moves in the irradiation target with respect to the long irradiation target. Since the rotation angle of this arm does not directly become the swing angle of the tomographic plane, it is difficult to obtain a tomographic image with a thin tomographic thickness compared to the original tomographic image, and because the TDI method is used. There is a problem that the image signal is averaged and the S / N is lowered due to the charge addition in the arm traveling direction.

  In order to solve the above-described problem, an X-ray tomography apparatus according to the present invention stores an electric charge for each of a plurality of pixels in accordance with the X-ray intensity and sequentially outputs the electric signal as an electric signal, and to the X-ray sensor. A sensor control circuit for storing and outputting electric charges by controlling the drive signals of the X-rays, an image reproducing unit for sequentially digitizing and re-arranging electric signals from the X-ray sensor, and reconstructing the images, and the X to sandwich the irradiation target An X-ray irradiation unit disposed at a position facing the line sensor, an arm that holds the X-ray sensor and the X-ray irradiation unit, and an X-ray image of the irradiation target for X-ray imaging of the tomographic plane of the irradiation target An arm rotating unit that rotates the arm by a predetermined angle while irradiating the X-ray from the X-ray irradiating unit around a predetermined range, and the sensor control circuit is configured to rotate the arm while the arm is rotating. Charge each pixel And the product, and sequentially outputs the rotation after completion of stored charge in the electric signal.

  With this configuration, the arm can be rotated by a predetermined angle while irradiating the X-ray from the X-ray irradiator around the predetermined range of the irradiation target, and the swing angle with respect to the predetermined range can be increased, resulting in a clearer image. With this, an image with a thin tomographic thickness can be obtained.

  As described above, the X-ray tomography apparatus according to the present invention accumulates charges generated according to the intensity of X-rays in each pixel of the X-ray sensor during arm rotation, and electrically charges the accumulated charges after the end of rotation. A tomographic image is generated by sequentially outputting as a signal to create a tomographic image, and a clearer and thinner tomographic image in which only the tomographic portion desired to be imaged appears clearly can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the entire apparatus in the X-ray tomography apparatus 1 of the present invention. X-rays 2 irradiated from an X-ray irradiation unit 10 are incident on an X-ray sensor 5 with respect to an irradiation object 9. . The arm 11 supports the X-ray sensor 5 and the X-ray irradiation unit 10 in a state of facing the X-ray irradiation unit 10.

  The arm 11 is configured to be rotated by the arm rotating unit 12a and linearly moved by the arm linear moving unit 12b in response to the drive signal 6 from the sensor control circuit 7. In a plurality of pixels 1 in the X-ray sensor 5, the X-ray 2 is converted and stored as an electrical signal, transmitted as an image signal to the image joining unit 13, and reproduced as an image.

  2 is a diagram showing the X-ray sensor 5 in FIG. 1, and FIG. 3 is a schematic diagram showing the internal operation of the X-ray sensor 5. As shown in FIG.

  As shown in FIG. 2, the X-ray sensor 5 has pixels 1 arranged in a grid pattern. Further, as shown in FIG. 3, the X-ray 2 is accumulated as a charge 3 through a scintillator 15 that converts the X-ray 2 into visible light, and the accumulated charge is discharged and the charge is sequentially transferred in the sensor. As a result, the electric signal 4 is generated.

  First, the operation of the X-ray sensor 5 will be described with reference to FIGS. As shown in FIG. 2, the X-ray sensor 5 has a plurality of pixels 1 arranged in a grid.

  As shown in FIG. 3, when the X-ray 2 is incident, the scintillator 15 converts the X-ray 2 into visible light and emits visible light according to its intensity. Then, the charge 3 is accumulated due to the characteristic of generating charge according to the amount of light that the X-ray sensor 5 has.

  Further, the electric charges 3 accumulated in each pixel 1 are sequentially transferred in the horizontal direction as an electric signal 4, and the signals reaching the end are sequentially transferred in the vertical direction. Then, the image signal is output from the final output terminal of the X-ray sensor 5 to the outside of the sensor.

  Note that the material of the scintillator 15 is generally CSI or the like, but this is not necessarily fixed, and other materials may be used. In the present embodiment, the X-ray sensor 5 is exemplified by a scintillator 15 that converts visible light and a CCD device that generates charges 3 according to the amount of light. A sensor using CdTe having characteristics to convert may be used. Furthermore, the scintillator 15 may be in the form of a sheet or may be arranged in a state of being separated for each pixel 1.

  At this time, the X-ray sensor 5 is controlled by the drive signal 6 sent from the sensor control circuit 7 for operations such as charge 3 accumulation, discharge and transfer. The important point here is that the sensor control circuit 7 sequentially outputs the electric charge 3 accumulated after the rotation as an electric signal. In the present embodiment, the electric charge 3 transferred from the adjacent pixel 1 is supplied by itself. Unlike the conventional TDI method of adding together with the pixel data, the charge 3 of each pixel 1 is independently and sequentially sent out. That is, the point that the data 3 of each pixel 1 of the X-ray sensor is individually independent and the charge 3 is accumulated in each pixel 1 is greatly different from the conventional one.

  Next, the entire apparatus using the X-ray sensor 5 will be described with reference to FIG.

  As described above, when imaging is started, the sensor control circuit 7 transmits the drive signal 6 to the X-ray sensor 5 to control the X-ray sensor 5.

  Further, the X-ray irradiation unit 10 is arranged at a position facing the X-ray sensor 5 with the irradiation object 2 interposed therebetween, and both the arm 11 maintains the relative position between the X-ray sensor 5 and the X-ray irradiation unit 10. Holding.

  Further, the arm rotating unit 12a has a function of rotating the arm 11 by a predetermined angle with a predetermined range of the irradiation target 9 as a rotation center. That is, the arm rotation unit 12a rotates the arm 11 at a predetermined timing, rotation speed, and rotation angle simultaneously with the start of photographing.

  The arm linear movement unit 12b has a function of linearly moving the arm 11 by a predetermined distance in parallel with the tomographic plane of the irradiation target 9 when the rotation of the arm 11 is completed. The arm linear movement unit 12b also performs linear movement of the arm 11 at a predetermined timing and movement amount.

  The image reproducing unit 8 has a function of sequentially digitizing the image signals 14 sent out from the X-ray sensor 5 after the start of imaging and rearranging them in a grid pattern to reproduce the images. That is, the image reproducing unit 8 digitizes the image signal 14 indicating the X-ray intensity of each pixel of the X-ray sensor 1 which is an analog signal by a built-in A / D converter (not shown), and further digitized image data. Are stored in a memory (not shown) so that images can be reproduced in accordance with a predetermined arrangement rule.

  The image joining unit 13 arranged in the image reproduction unit 8 has a function of connecting the image data reproduced by the image reproduction unit 8. That is, the image reproducing unit 8 has a function of connecting individual image data obtained during the rotation of the arm during the repeated operation of the rotation of the arm 11 by the arm rotation 12a and the linear movement of the arm 11 by the linear movement unit 12b. .

  In the X-ray tomography apparatus of the present embodiment as described above, the operation when tomography is performed will be described with reference to FIGS.

  FIG. 4 is a diagram showing the movement of the arm in the first embodiment of the present invention, and shows the tomographic plane 9 to be irradiated.

  The X-ray sensor 5 and the X-ray irradiator 10 are held by an arm 11, and first rotate around a tomographic plane (length: L2) within a predetermined range within the irradiation object 9, and then after the end of rotation. Move straight. Then, the linear movement of the arm 11 is stopped, and X-ray irradiation is performed only during the rotation. During this time, the X-ray sensor 5 accumulates charges. After the rotation is completed, the X-ray sensor 5 discharges the charges. Thus, image data is constructed.

  This will be described using a timing chart. FIG. 5 shows the movement of the arm 11, the drive signal 6 of the X-ray sensor, and the timing of X-ray irradiation in the first embodiment of the present invention. In FIG. 5, as described above, when X-ray tomography is started, arm rotation and X-ray irradiation are first started. During this time, in the X-ray sensor 5, charges 3 are accumulated in each pixel 1 according to the X-ray intensity.

  Then, when the arm 11 rotates by a predetermined rotation angle (vibration angle), the arm rotation and the X-ray irradiation are stopped.

  Subsequently, the arm moves straight in parallel with the desired tomographic plane (length: L2) to be irradiated by the lateral width (length: L1) of the X-ray sensor 5 or less. Since this movement amount is necessary for subsequent image stitching, a numerical value is fixed in advance. In the meantime, the X-ray sensor 5 discharges the charge 3 accumulated during the rotation of the arm 11 in each pixel 1 and subsequently transfers the charge as an image signal. Then, the image signals 14 for all the pixels are sent to the image reproducing unit 8 as shown in FIG. This operation is performed a predetermined number of times.

  In this way, the arm can be rotated by a predetermined angle centered on a predetermined range of the irradiation target while irradiating the X-ray from the X-ray irradiation unit, and a certain thickness portion of the tomographic plane (the tomographic portion to be photographed) Only the image relating to) appears clearly, and other peripheral parts that are transmitted through and incident at the same time are so-called blurred images because the object always changes. As the swing angle with respect to the predetermined range is increased, a thinner tomographic image is obtained.

  In other words, while the arm is rotating, the charge generated according to the intensity of the X-ray is accumulated in each pixel of the X-ray sensor, and the accumulated charge is sequentially output as an electrical signal after the rotation is completed to create a tomographic image. Thus, it is possible to obtain a clearer and thinner tomographic image in which only the tomographic part to be photographed appears clearly.

  Here, description will be given using an actual photographing example. FIG. 6 is a diagram showing a model of a human tooth that is an irradiation target, and the solid line indicated by the irradiation target 9a in FIG. 6 is a tomographic plane desired as a tomographic image. FIG. 7 is a model of an X-ray tomographic image obtained by the apparatus according to the present embodiment, and corresponds to the tomographic image of FIG. 6 shown from the lateral direction.

  The image reproduced with the image data obtained during one rotation of the arm 11 is an image like one of the images shown in the strips on the upper side of FIG. Then, when the rotation and straight movement of the arm 11 are repeated a plurality of times, strip-like images as shown in the upper side of FIG. The image reproducing unit 8 stores these image data in a memory.

  Further, these strip-shaped image data are joined together in the image joining portion 13 in consideration of the linear movement amount of the arm fixed and determined in advance, and tomographic image data corresponding to a desired length is reproduced.

  By such image processing, a tomographic image having a desired width of the teeth and gums as shown in the lower side of FIG. 8 is obtained.

  Since the X-ray tomography apparatus of the present invention can obtain a clear tomographic image having a thin tomographic thickness, it is very useful for diagnosis for performing dental treatment, particularly implant surgery.

The block diagram which shows the whole apparatus of the X-ray tomography apparatus of this invention The figure which shows the X-ray sensor of the X-ray tomography apparatus of this invention The schematic diagram which shows operation | movement inside the X-ray sensor of the X-ray tomography apparatus of this invention. The figure which shows the motion of the arm of the X-ray tomography apparatus of this invention The figure which shows the motion of the arm of the X-ray tomography apparatus of this invention, the drive signal of an X-ray sensor, and the timing of X-ray irradiation. The figure which shows an example of the irradiation object of the X-ray tomography apparatus of this invention X-ray tomographic image of irradiation object of X-ray tomography apparatus of the present invention The figure which shows the image joining of the X-ray tomography apparatus of this invention The figure which shows the motion of the arm of the X-ray tomography apparatus in the conventional X-ray tomography method The figure which shows the movement of the arm of the X-ray tomography apparatus in the conventional X-ray tomography, the drive signal of an X-ray sensor, and the timing of X-ray irradiation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray tomography apparatus 2 X-ray 3 Electric charge 4 Electric signal 5 X-ray sensor 5a Pixel 6 Drive signal 7 Sensor control circuit 8 Image reproduction part 9, 9a Irradiation object 10 X-ray irradiation part 11 Arm 12a Arm rotation part 12b Arm movement Section 13 Image joint section 14 Image signal 15 Scintillator

Claims (3)

An X-ray sensor that accumulates electric charge for each of the plurality of pixels according to the X-ray intensity and sequentially outputs the electric signal;
A sensor control circuit for controlling the drive signal to the X-ray sensor to accumulate and output charges;
An image reproduction unit for sequentially digitizing and rearranging the electrical signals from the X-ray sensor and reproducing the image;
An X-ray irradiation unit arranged at a position facing the X-ray sensor across the irradiation target;
An arm for holding the X-ray sensor and the X-ray irradiation unit;
An arm rotating unit that rotates the arm by a predetermined angle while irradiating X-rays from the X-ray irradiation unit around a predetermined range of the irradiation target in order to X-ray the tomographic plane of the irradiation target;
The sensor control circuit accumulates electric charge in each pixel of the X-ray sensor while the arm is rotating, and sequentially outputs the accumulated electric charge as an electric signal after the rotation is completed. The plurality of pixels of the X-ray sensor are arranged in a grid pattern, and the image reproduction unit sequentially digitizes electrical signals from the X-ray sensor and rearranges the signals in a grid pattern to reproduce an image. The X-ray tomography apparatus according to 1. An arm linear movement unit that linearly moves the arm a predetermined distance in parallel with the tomographic plane of the irradiation target with the completion of rotation of the arm;
An image joining unit that joins a plurality of pieces of image data acquired during the rotation of the arm and reproduced by the image reproduction unit by repeating the rotation of the arm by the rotation unit and the linear movement of the arm by the linear movement unit. An X-ray tomography apparatus characterized by that.

Images