JP2005253788A - Apparatus and method for capturing radiation image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a sense of discomfort when displaying a radiographed image captured by moving an X-ray source in almost parallel to an X-ray sensor by reducing strains of the radiographed image resulted from exposure to X rays from an oblique direction. <P>SOLUTION: The radiographed image is converted to geometrically so that the image always faces an X-ray tube. A plurality of image data are then observed as a video to grasp the three-dimensional structure of a human body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for imaging a radiation intensity distribution, and more particularly to a medical X-ray imaging apparatus and a display apparatus.

  Using an X-ray image sensor system that can output X-rays and digital images, X-ray imaging is performed while the X-ray tube and X-ray image sensor, which are X-ray generation sources, are moved in parallel in opposite directions. Patent Documents 1 to 5 disclose techniques for creating a tomographic plane.

  FIG. 5 is a diagram for explaining such a conventional technique. The X-ray tube 1 moves in the direction indicated by the arrow. The X-ray image sensor 2 generates an electrical signal corresponding to the exposure amount of the X-rays emitted from the X-ray tube 1 and reaching the sensor surface, digitized, and output as image data (X-ray image) A device for digitizing the electrical signal from the sensor 2 is not shown). Reference numeral 3 denotes a subject, which is a human body in this example.

In the apparatus configured as described above, the image sensor 2 is moved in the opposite direction in accordance with the movement of the X-ray tube 1 to always track the effective area of the X-ray beam. If the X-ray image sensor is sufficiently large, the X-ray image sensor does not need to move. However, since the X-ray tube 1 needs to generate X-rays that always go to the image sensor as it moves, its direction changes according to the movement. The shift calculation device 4 is a device for calculating a desired tomographic plane (set by the desired tomographic plane input unit 5) from the image data obtained from the X-ray sensor 2. The shift calculation device 4 calculates the shift amount of the image data obtained from the X-ray sensor 2 from a plurality of directions according to each tomographic plane position indicated by a broken line in the human body 3. Note that a desired tomographic plane position can be instructed to the shift arithmetic unit 4 from the desired tomographic plane input device 5. The addition averaging device 6 adds the images shifted by the shift calculation device 5 and blurs parts other than the desired tomographic plane to emphasize the desired tomographic plane and output a tomographic image.
Japanese Patent No. 2722730 Japanese Patent No. 2871053 Japanese Patent No. 2874317 Japanese Patent No. 3166194 Japanese Patent No. 3341684

  In the apparatus described above, an image of a tomographic plane at a desired position is constructed by calculation and presented. However, it is also possible to provide meaningful information for diagnosis and diagnosis by displaying images taken while moving the X-ray tube 1 and the X-ray sensor 2 as described above. That is, the observer can grasp the three-dimensional structure and state of the human body simply by observing the image actually obtained from the image sensor 2 (the image observed from each X-ray tube position) instead of the tomographic plane. Can be very useful diagnostic information. For example, if a plurality of images obtained as the X-ray tube 1 moves from the image sensor 2 are sequentially displayed and captured as a moving image, the three-dimensional structure can be recognized.

  However, since the image obtained in this case is due to the parallel movement of the X-ray tube 1 or the X-ray sensor 2, the image obtained by exposing X-rays from an oblique direction is distorted, There is a possibility of causing a strange feeling to the observer.

  The present invention has been made in view of the above problems, and in the case of presenting an image obtained by moving an X-ray generation source substantially parallel to an X-ray sensor and taking an X-ray image, an oblique direction is provided. The purpose is to reduce the distortion of the photographed image due to the X-ray exposure from the camera and to remove the uncomfortable feeling.

In order to achieve the above object, a radiological image acquisition apparatus according to the present invention comprises the following arrangement. That is,
A radiation image acquisition apparatus having a radiation generation apparatus including a radiation generation source and a radiation image sensor that converts radiation intensity transmitted through a subject into image information,
Obtaining means for obtaining image information from the radiation image sensor by irradiating radiation from the radiation source;
Conversion means for geometrically transforming the image information acquired by the acquisition means to project it onto an imaginary plane set to face the radiation generation source.

Using a radiation image acquisition apparatus having a radiation generation apparatus including a radiation generation source and a radiation image sensor that converts radiation intensity into image information, the radiation generation source is moved in parallel with the detection surface of the radiation image sensor. Input means for inputting a plurality of radiation images acquired by irradiation and respective radiation source positions;
Conversion means for geometrically transforming each image information input by the input means to project the image information input on an imaginary plane set to face the radiation source position corresponding to the image information; ,
Display means for displaying the image information converted by the conversion means.

  According to the present invention, when presenting an image obtained by moving an X-ray generation source substantially parallel to an X-ray sensor and performing X-ray imaging, an image captured by X-ray exposure from an oblique direction is displayed. It is possible to reduce distortion and present an image with no sense of incongruity.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a diagram illustrating a configuration of a radiological image acquisition apparatus according to the present embodiment. In FIG. 1, an X-ray tube 1 generates X-rays while performing parallel movement in a direction indicated by an arrow. The X-ray image sensor 2 generates an electrical signal corresponding to the incident X-ray dose. Digital image data is obtained by digitizing this electrical signal with a device (not shown). As the X-ray image sensor 2, an FPD (Flat Panel Detector) can be used. The FPD may be an indirect type that converts X-rays into light by a fluorescent film and converts the amount of light into an electric signal, or a direct type that directly converts an X-ray dose into an electric signal. This digital image data includes an X-ray image transmitted through the subject 3. As the X-ray tube 1 moves, the effective area of the X-ray beam is tracked by moving the image sensor 2 in the opposite direction. It is assumed that the control unit 4 performs such movement control of the X-ray tube 1 and image sensor 2 and exposure control of the X-ray tube 1. However, if the X-ray image sensor 2 is sufficiently large, the X-ray image sensor does not need to move. Since the X-ray tube 1 needs to generate X-rays that always travel toward the image sensor while moving, the direction is changed in accordance with the movement.

  The control unit 4 provides an electrical signal output from the X-ray image sensor 2 to the first image storage unit 21 as a digital image signal. The first image storage unit 21 stores a plurality of X-ray images obtained along with the movement of the X-ray tube 1 in association with the position information of the X-ray tube 1. The position information of the X-ray tube 1 is obtained by an encoder device (not shown) attached to the X-ray tube 1, for example. The geometric transformation calculation unit 22 geometrically transforms the X-ray image stored in the first image storage unit 21 using corresponding position information. Although this geometric transformation operation will be described later, the image stored in the first image storage unit 21 is aligned with the position of the X-ray tube 1 and is orthogonal to the central axis of the X-ray beam of the X-ray tube 1. Perform geometric transformation such that an image exists on an imaginary surface. The second storage unit 23 stores the image geometrically transformed by the geometric transformation calculation unit 22. The display unit 24 sequentially displays a plurality of images stored in the second image storage unit 23 as a moving image.

  The control configuration by the control unit 4, the first storage unit 21, the geometric transformation calculation unit 22, the second storage unit 23, the moving image display unit 24, and the operation unit 27 described later is performed by a so-called computer device (information processing device). It will be clear that it can also be realized.

  The geometric transformation calculation will be described. FIG. 2 shows an outline of a radiation image acquisition operation including a geometric operation according to the present embodiment. FIG. 2 is a diagram showing a state in which X-rays are irradiated from a certain angle. That is, the X-ray tube 1 is moved from the position A0 immediately above the center of the X-ray sensor 2 to the position A1 in the left direction in the drawing. At this time, an imaginary plane 35 is assumed. This aerial plane 35 is a plane that intersects perpendicularly with the center line 37 of the X-ray beam from the X-ray tube 1 at the position A1. The X-ray image (transparent shadow) projected on the X-ray sensor 2 can be converted into an image projected on the virtual plane 35 by simple geometric conversion. The image on the virtual plane 35 obtained by such conversion is an image observed from the front as viewed from the X-ray tube 1. For this reason, the observer can observe an X-ray image without a sense of incongruity by observing such an image on the virtual plane 35. In this case, the distance L to the imaginary plane 9 can be set freely.

  FIG. 3 shows the geometric transformation. In FIG. 3, lines represented by reference numerals 31, 32, and 33 represent axes (X, Y, and Z axes) of a three-dimensional space. A point indicated by 34 represents the position of the X-ray tube 1. Note that the detection surface of the X-ray sensor 2 is present on the XY plane (Z = 0). A broken line 37 indicates the center line of the X-ray beam emitted from the X-ray tube 1, and the imaginary plane 35 is a plane perpendicular to the center line 37. Reference numeral 36 denotes an arbitrary X-ray beam, which intersects the detection surface of the X-ray sensor 2, that is, the XY plane, at coordinates (x0, y0).

  Considering at which position the X-ray beam incident from the X-ray sensor 2 to the position (x0, y0) intersects with the imaginary plane 35 orthogonal to the center line 37, the intersection of the straight line 36 and the imaginary plane 35 ( x0 ', y0', z). Considering the imaginary plane 35 as a reference, the plane coordinate position (x1, y1) of (x0 ', y0', z) can be easily obtained, and the original pixel data existing at (x0, y0) is converted. Later we will move to this (x1, y1). Such movement is repeated for all pixels.

  In this case, the distance L between the X-ray tube 34 and the aerial plane 35 can be freely changed. As indicated by reference numeral 25 in FIG. 1, a desired distance is input to the geometric transformation calculation unit 22 from the operation unit 27. Further, the pixel interval of the geometrically transformed image can be determined freely, and is performed by inputting a desired pixel interval to the geometric transformation operation unit 22 from the operation unit 27 as indicated by reference numeral 26. Specifically, the calculation can be performed by obtaining the pixel value of the pixel position of the output image subjected to the geometric conversion by the interpolation operation from the pixel value of the position where each pixel of the original image is subjected to the geometric conversion. Note that changing the pixel interval and changing the distance from the imaginary plane are virtually equivalent, but for an operator who has become an X-ray device, a sensor with a sampling pitch of several mm is placed at a distance of several meters. The above configuration is provided because it is easier to understand in practice and the operability is improved when the photograph is taken.

  FIG. 4 is a flowchart for explaining processing by the radiological image acquisition apparatus of the present embodiment. First, in step S51, the position (Xf, Yf, Zf) of the X-ray tube 1 with respect to the image is obtained. In step S52, the central axis (the central line 37 in FIG. 3) of the X-ray beam emitted by the X-ray tube 1 is obtained from that position. As the central axis, a central axis defined in advance for the X-ray tube is adopted. In step S53, an equation of an imaginary orthogonal plane (imaginary plane 35) perpendicular to the central axis obtained in step S52, aX + bY + cZ + d = 0, is obtained. Then, the geometric transformation starts from step S54, and when the calculation for all the pixels is completed, this processing is terminated.

  In step S55, the pixel position (x0, y0, 0) of the original image data (z is always 0 because it is on the XY plane) is obtained. In step S56, an equation (the following equation 1) of a straight line (straight line 36 in FIG. 3) connecting the pixel position (x0, y0, 0) and the position (Xf, Yf, Zf) of the X-ray tube 1 is calculated. I do.

  In step S57, an intersection point between the straight line and the imaginary orthogonal plane (35) is calculated, and in step S58, the intersection coordinates are converted into pixel positions on the imaginary orthogonal plane (35). In step S59, the original pixel value is moved to a new pixel position, and the position conversion of one pixel is completed. In step S60, the process proceeds to the next pixel. By this processing, an image always facing the X-ray is obtained.

  The processes in steps S55 to S59 described above are performed on a plurality of images at all tube positions and stored in the second storage unit 23. By observing the stored image with the display unit 24, the observer can intuitively recognize the structure of the subject.

Second Embodiment
In the first embodiment, the pixel value is not changed, and only the geometric conversion of the position is performed. However, when an X-ray image is actually taken, the pixel value itself also depends on the distance from the X-ray tube 1. Since the X-ray itself spreads in a non-directional direction, the pixel value decreases in inverse proportion to the square of the distance. Therefore, in the second embodiment, the pixel value is corrected by a change in distance that occurs when the pixel position is converted, and a more natural X-ray image can be observed.

  First, the distance between the point (x0, y0, 0) of the original image in FIG. 3 and the X-ray tube 1 is L0, and the pixel value at this position is A0. If the distance between the point (x0 ′, y0 ′, z) on the imaginary plane 35 and the X-ray tube is L1, a new pixel value A0 ′ can be calculated by the following equation.

  Therefore, in the second embodiment, the pixel value calculated by the above formula is used as a pixel value subjected to geometric conversion.

<Third Embodiment>
In the first embodiment, image information displayed on a plane orthogonal to the central axis of the X-ray tube 1 is calculated, but the central axis of the X-ray tube 1 may not be clear. In this case, there is a method that does not stick to the central axis. For example, since the X-ray tube position and the center position of the X-ray image sensor are clear, a straight line connecting these two points is obtained, and geometric calculation is always performed using a plane orthogonal to the straight line as an imaginary plane. Even with this method, image data with a stable orientation can be obtained. In this case, the same effect can be obtained even when a specific point of the sensor is used instead of the center position of the sensor.

  As described above, according to the above-described embodiment, an X-ray image taken at an arbitrary angle is always subjected to geometric transformation as observed on a surface facing the X-ray tube, and is further displayed as a moving image. Intuitive structure recognition is possible.

  The moving image display as described above can also be realized by providing the computer device with the position and image of the X-ray sensor stored in the first storage unit 21.

  Therefore, an object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. This can also be achieved by reading and executing the program code stored in.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the structure of the radiographic image acquisition apparatus by 1st Embodiment. It is a figure explaining the imaginary image position by 1st Embodiment. It is a figure explaining the geometric conversion process by 1st Embodiment. It is a flowchart explaining the geometric conversion process by 1st Embodiment. It is a block diagram which shows a general radiographic image acquisition apparatus.

Claims (12)

A radiation image acquisition apparatus having a radiation generation apparatus including a radiation generation source and a radiation image sensor that converts radiation intensity transmitted through a subject into image information,
Obtaining means for obtaining image information from the radiation image sensor by irradiating radiation from the radiation source;
A radiographic image acquisition apparatus comprising: a conversion unit that geometrically converts the image information acquired by the acquisition unit to be projected onto an imaginary plane set to face the radiation generation source.   The radiographic image acquisition apparatus according to claim 1, wherein the aerial plane is a plane orthogonal to a central axis of a radiation beam generated from the radiation source.   The radiological image acquisition apparatus according to claim 1, wherein the aerial plane is a plane orthogonal to a straight line connecting a specific position of the radiation source and the radiographic image sensor.   The radiographic image acquisition apparatus according to claim 1, wherein the conversion unit further converts a pixel value according to a change due to the geometric conversion of a distance between the radiation source and the pixel position.   The radiographic image acquisition apparatus according to claim 1, further comprising setting means for setting a distance between the aerial plane and the radiation generation source.   The radiographic image acquisition apparatus according to claim 1, further comprising setting means for setting a pixel interval of the image on the imaginary plane. The acquisition means acquires image information corresponding to a plurality of positions of the radiation generation source from the radiation image sensor by irradiating the radiation while moving the radiation generation source,
The image processing apparatus further includes display means for projecting image information corresponding to each position of the radiation generation source onto an imaginary plane corresponding to each position by the conversion means, and sequentially displaying the obtained images. The radiographic image acquisition apparatus according to claim 1. Using a radiation image acquisition apparatus having a radiation generation apparatus including a radiation generation source and a radiation image sensor that converts radiation intensity into image information, the radiation generation source is moved in parallel with the detection surface of the radiation image sensor. Input means for inputting a plurality of radiation images acquired by irradiation and respective radiation source positions;
Conversion means for geometrically transforming each image information input by the input means to project the image information input on an imaginary plane set to face the radiation source position corresponding to the image information; ,
An information processing apparatus comprising: display means for displaying the image information converted by the conversion means. A radiation image acquisition method including a radiation generation device including a radiation generation source and a radiation image sensor that converts radiation intensity transmitted through a subject into image information,
Obtaining image information from the radiation image sensor by irradiating radiation from the radiation source; and
A radiographic image acquisition method comprising: a conversion step of geometrically transforming the image information acquired in the acquisition step so as to project the image information onto an imaginary plane set to face the radiation generation source. Using a radiation image acquisition apparatus having a radiation generation apparatus including a radiation generation source and a radiation image sensor that converts radiation intensity into image information, the radiation generation source is moved in parallel with the detection surface of the radiation image sensor. An input step of inputting a plurality of radiation images acquired by irradiation and respective radiation source positions;
A conversion step of geometrically transforming the image information input by the input means to project the image information input on an imaginary plane set to face the radiation source position based on the corresponding radiation source position; ,
A display step of displaying the image information converted in the conversion step.   A control program for causing a computer to execute the information processing method according to claim 10.   A storage medium storing a control program for causing a computer to execute the information processing method according to claim 10.

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