JP2007330583A - Radiographic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an enlarged image of an effective field of view by reducing regions with halation generated during measuring a radiographic image. <P>SOLUTION: An X-ray plane detector 7 loads an X ray transmitted through a subject and converts it to an electric signal. X rays directly entering into the X-ray plane detector 7 without transmitting through the subject cause the halation. An image processing controlling means 9 takes a measured radiographic image therein from the X-ray plane detector 7, and a halation detecting part 12 detects the region with halation. An effective field of view operating part 15 finds a magnification and position information from the detected region with the halation, and an operation part 14 enlarges the image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray fluoroscopic apparatus using an X-ray flat panel detector, and more particularly to an X-ray fluoroscopic apparatus that detects a halation site during display.

  The X-ray flat panel detector is an X-ray detection means that can detect a transmitted X-ray of a subject over a wide area. The X-ray flat panel detector can normally detect the subject's transmitted X-ray, but the X-ray that passes directly through the subject does not cause halation when detected by the detector. If the image is displayed on the display screen, it is difficult to interpret the perspective image.

Therefore, in order to remove the halation at the time of display, a method is adopted in which the operator selects an optimum enlargement factor from among a plurality of preset perspective image enlargement factors.
Note that Patent Document 1 discloses an example of removing a halation site in terms of data processing.
JP 2004-16503 A

In the conventional halation removal method, since the enlargement ratio is set in advance, the halation removal along the actual fluoroscopic image may not be performed properly.
An object of the present invention is to provide a fluoroscopic apparatus capable of appropriately removing halation from an actual fluoroscopic image.

  The present invention relates to an X-ray generator that irradiates X-rays, an X-ray flat panel detector that detects X-rays transmitted through a subject, and a halation detector that detects a halation site from measured fluoroscopic image data from the detector And effective visual field information including the position of the effective visual field from the detected halation site, the effective size, and the enlargement ratio of the effective size to the predetermined pixel size, and the measurement fluoroscopy determined by the position and the effective size based on this information Disclosed is a fluoroscopic imaging device that includes a computing unit that enlarges an effective image in an image at the above-described magnification, and a display unit that displays the enlarged image.

  According to the present invention, a halation site is detected from the actually measured fluoroscopic image itself, and the image is automatically enlarged so as to remove the halation site from the fluoroscopic image, thereby obtaining a display of a fluoroscopic image with less influence of halation. It is done.

  FIG. 1 is a diagram showing an overall configuration example of a fluoroscopic imaging apparatus according to the present invention. This apparatus includes an X-ray source 1, an X-ray movable diaphragm 2, an X-ray compensation filter 3, an X-ray movable diaphragm control unit 4, a mechanism control unit 5, a table 6, and an X-ray plane detector 7 as a fluoroscopic imaging apparatus main body. And a flat detector control means 8.

  Furthermore, this apparatus has an image processing control unit 9, a display output unit 10, an image memory 11, a halation detection unit 12, a display circuit 13, a calculation unit 14, and an effective visual field calculation unit 15 as image processing units.

The operation on the fluoroscopic apparatus main body side is as follows.
At the time of imaging, the table 6 mounted on the subject is positioned by the mechanism control unit, and the aperture setting of the X-ray movable aperture unit 2 (collimator) and the selection setting of the X-ray compensation filter 3 are performed by the X-ray movable aperture control unit 4. Do. After this setting, X-rays are emitted from the X-ray tube 1. The X-ray flat detector 7 takes in X-rays including transmitted X-rays of the subject and converts them into electric signals, which are output to the image processing control means 9 via the flat detector control means 8.

The operation on the image processing means side is described. The main feature of the present invention is the configuration and operation on the image processing means side.
Upon receiving the measured transmission image data from the flat detector control means 8, the image processing control means 9 sends it to the halation detection unit 12 and temporarily stores it in the image memory 11. The halation detection unit 12 takes in the measured fluoroscopic image data from the image processing control means 9 and automatically detects where the halation has occurred. The effective visual field calculation unit 15 performs effective visual field calculation based on the halation position detection result of the halation detection unit 12. The effective visual field is an area determined by a rectangular size with respect to the measurement fluoroscopic image. For example, when the measurement fluoroscopic image size is m × n, the position of the start, the center, the end point, etc. therein is (a, b), and the effective pixel The size is expressed as i × j (where i <m, j <n).

  Since the pixel size i × j as the effective field of view is enlarged and displayed up to the pixel size P × Q of the display area, the calculation unit 15 also calculates the enlargement ratio (P × Q) / (i × j) as the ratio between the two. Ask for.

The calculation unit 14 reads the measured fluoroscopic image that takes in the calculated effective visual field information (the position of the start, the effective pixel size, and the magnification) and stores it in the image memory 11, and the position and the size according to the position of the start, the pixel size, and the like. The image is cut out and enlarged according to the enlargement ratio.
The display circuit 13 takes in the enlarged image from the calculation unit 14 and sends it to the image processing control means 9, and the display output means 10 displays the enlarged image on the display screen.
Thus, an enlarged image corresponding to the size of the display area was obtained based on the automatic detection of the effective visual field excluding the halation site, and this could be displayed on the display screen.

  FIG. 2 shows a configuration example as another embodiment. This embodiment is characterized in that the enlargement notification means 16 is added to FIG. In FIG. 1, the effective visual field calculation and the necessary enlargement processing and display are automatically performed when the measurement is performed. However, in FIG. It is intended to be performed as a trigger when it is sent via.

  Therefore, an enlargement notification means 16 that is a mouse or keyboard input such as an operation console is provided, and this output is sent to the image processing control means 9 as a trigger for operating the detection unit 12, the calculation unit 15, and the calculation unit 14. Thus, when the enlargement instruction from the enlargement notification means 16 is input, the enlargement process is executed and the display is performed.

A third embodiment will be described. In FIG. 1 and FIG. 2, the calculation unit 14 performs the cut-out and enlargement processing of the measured fluoroscopic image in the image memory 11 based on the calculated effective visual field information. However, in the third embodiment, the calculation unit 14 The logical sum of each pixel of the insertion area and the halation area is taken, this common area is recognized as a halation part, removed from the image, a new enlargement ratio is obtained for the remaining image, and the enlargement ratio (including the position) is obtained. Based on this, image enlargement is performed.
Therefore, the image processing control means 9 takes in the X-ray diaphragm insertion area data from the X-ray movable diaphragm control means 4 and sends it to the calculation unit 14. The calculation unit 14 calculates a logical OR of the pixel corresponding to the effective field information (position, effective pixel size) from the effective field calculation unit 15 and the X-ray aperture insertion region data.

  Here, the insertion region data of the X-ray diaphragm is data indicating the shape of a rectangular, polygonal, or circular X-ray diaphragm (collimator) with respect to the radiation fan beam X-ray, for example, on an xy orthogonal axis. When this is viewed as data, the corresponding pixel position with an aperture can be indicated as “1”, and the corresponding pixel location without an aperture can be indicated as “0”. On the other hand, the effective visual field information (position, effective pixel size) can also indicate a pixel position within the effective pixel size as “0” and a pixel position outside the effective pixel size as “1”. Therefore, the calculation unit 14 binarizes the image by “1” and “0” corresponding to the pixel from the aperture region data, and binarizes the image by converting “1” and “0” corresponding to the pixel from the effective visual field information. And a logical sum corresponding to the pixels of both. As a result of this logical sum, a pixel that is “0” is determined to be a pixel in the final effective visual field, and a pixel that is “1” is determined to be a pixel in the final halation region. The calculation unit 14 obtains an enlargement ratio by comparing the area of the final effective visual field size with the display screen size. The image at the final effective visual field size is enlarged at this enlargement ratio. The enlarged image is sent to the display output means 10 via the display circuit 13 and displayed on the display screen. It is also stored in the image memory 11.

FIG. 3 shows a processing flow for calculating the effective field of view and calculating the enlargement ratio. An explanatory diagram for this purpose is shown in FIGS. 4, 5, and 6. The idea of calculating the effective field of view (steps S _{1 to} S ₇ ) is that pixel values (density) are projected in the x-direction and y-direction of the orthogonal xy axis of the measurement transmission image, and the projection value is less than the halation determination value. If it is within the effective field of view, and if it is below, it is determined to be a halation site. Calculated magnification (Step _S 8 to S ₉₎ is the area ratio.
Detailed description.
In Figure 3, each independently of the vertical direction (y direction) and horizontal direction (x-direction), the line _{x i i} = 1,2, ..., while updating and P, and the line _{y j} j = 1, 2 .., R, and updating the profile value (projection value) for each line (steps S ₁ , S ₂ , S ₄ , S ₅ ). Then, the profile value is compared with the halation determination value (for example, 240) for each of the lines x _i and y _j, and xj and yj which are profile values smaller than the determination value are stored independently (step S ₃ ). Here, being smaller than the determination value means a portion where no halation occurs.

FIG. 4 shows the relationship between the fluoroscopic image around the image of the halation portion H (however, the halation portion H is displayed in white for the sake of clarity, and an animated display in which only the skeleton is emphasized) and the x and y lines. Each line is updated from left to right and up to down as indicated by arrows. 5A and 5B show profile values in the x _i and y _j lines as shown in FIG. A pixel position having a profile value less than 240 is a position where no halation occurs. In FIG. 5 (b), _{x i} halation occurs site _{0 to y} 1 on the _line, y 2 _~660, sites without the occurrence of halation becomes _y 1 ~y ₂ reversed. Figure 5 (b), the _{y j} halation occurs site _{0 to x} 1 on the _line, x 2 _~670, sites without the occurrence of halation is _x 1 ~x ₂ reversed.

5A and 5B are performed independently for all of the x and y lines, and all of them are stored. Therefore, for the stored coordinates (x ₁ , x ₂ , y ₁ , y ₂ ,...), The x and y coordinate values that are the shortest from the respective end portions are obtained in each of the four directions, up, down, left, and right. FIG. 6 shows this state as an animation as a comparison with FIG. In Figure 6, _D 1 in the vertical direction, _{D 2} in the lateral direction _D 3, _{D 4} is the shortest distance from the end, therefore, the effective field of view _{(x 1, y 1),} (x 2, y 2), The rectangular area determined by the coordinate values of (x ₃ , y ₃ ) and (x ₄ , y ₄ ) could be determined. This is the processing in step S ₆ in FIG.

Then, determine the area S1 of the rectangular area calculated above (step _S 7). A ratio between the display screen area S2 obtained in advance and the calculated S1 is obtained, and this is set as an enlargement ratio (steps S ₇ and S ₈ ). Finally, the image in the rectangle is linearly enlarged with this enlargement ratio. Thus, an enlarged view of the image cut out with an effective field of view corresponding to the size of the display screen can be obtained and displayed. A display example of the enlarged image with respect to FIG. 6 is shown in FIG. Note that instead of the display screen area, if the display area is a small display area (smaller than S2), an enlargement ratio and an enlarged image corresponding to the display area are used.

  FIG. 8 shows an application example to an actual image, and it can be seen that it is the same as FIG. 6 and FIG.

The basis of enlargement is digital zoom (pixel extension). However, if priority is given to image quality, geometric enlargement can also be used. The geometric enlargement is performed by the distance (SID) between the X-ray tube and the X-ray detector (FPD). The larger the SID, the greater the magnification rate. However, since the incident X-ray dose to the X-ray detector is attenuated when the SID is increased, it is necessary to increase the X-ray condition and the exposure dose of the patient is increased. For this reason, the operator determines whether to prioritize image quality or exposure reduction, and switches between digital zoom and geometric zoom (by a button).
Similar to the digital enlargement flow described above, geometric enlargement can be performed by calculating D1 and changing the position of the X-ray detector until D1 is minimized. In this case, the position is changed while calculating D1.

1 is an overall configuration example diagram of the present invention. It is another example of the entire configuration of the present invention. It is a processing flowchart example figure of this invention. It is explanatory drawing of the profile of a plan perspective image. It is a figure which shows the profile value in FIG. It is an effective visual field calculation explanatory drawing. It is an enlarged view by the effective visual field of this invention. It is an example of application to an actual image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray tube 2 X-ray movable diaphragm 7 X-ray plane detector 9 Image processing control means 12 Halation detection part 14 Calculation part 15 Effective visual field calculation part

Claims (1)

An X-ray generator that emits X-rays, an X-ray detector that detects X-rays that have passed through the subject, and a halation detector that detects a halation site from measured fluoroscopic image data detected by the X-ray detector; The effective visual field information including the position of the effective visual field, the effective size, and the enlargement ratio of the effective size to the predetermined pixel size is calculated from the detected halation site, and the position, the effective position is calculated based on the information of the effective visual field. A fluoroscopic imaging apparatus comprising: a calculation unit that enlarges an effective image in a measurement fluoroscopic image determined by a size at the enlargement ratio; and a display unit that displays the enlarged effective image.

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