JPS6355342B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an X-ray tomography apparatus.

In conventional X-ray tomography devices, the X-ray tube device and the X-ray film are placed facing each other with the subject in between, and the straight line connecting the X-ray tube device and the X-ray film always passes through one point on the cut surface of the subject. While doing so, the two are moved relative to each other, and an X-ray transmission image on the cut surface near the point is obtained. Straight line, circle,
Various shapes such as spiral and clover shapes are adopted, but
Here, for convenience of explanation, a parallel type having the simplest straight line locus will be explained. In FIG. 1, the X-ray tube 1 and the film 2 face each other, and the X-ray tube and the film 2 move in opposite directions on a straight line parallel to the cut surface 31 as shown by the arrows. At this time,
Assuming that the X-rays emitted from the X-ray tube 1 and passing through the point O are always incident on one point A of the film 2, the second
As shown in the figure, the trajectory of the focus X of the X-ray tube 1 is X ₁ →
X ₂ →X ₃ →X ₄ , and the trajectory of point A is A ₁ →A ₂ →A ₃
→A ₄ . Assuming that the obstacle shadow S exists on a surface other than the cutting surface 31, the projected images of different portions S ₁ , S ₂ , S ₃ , and S ₄ of the obstacle shadow S are superimposed on point A. Therefore, the images of each part of S ₁ to _{S 4} are averaged, and as a result, the image of the obstacle shadow S becomes blurred. On the other hand, since the image at point O is always projected onto point A, the image does not become blurred. The following can also be said. In the parts S ₁ , S ₃ , and S ₄ of the defective shadow S where the X-ray absorption is large, the amount of transmitted X-rays is small and the image of point O is not clearly projected, but in the part S ₂ where the X-ray absorption is small, the amount of transmitted X-rays is large. Therefore, when the focal point is at _X2 , a transmitted image of point O is obtained.

That is, in principle, the relative movement of the X-ray tube 1 and film 2 has the meaning of averaging and blurring the obstruction shadows S and of searching for gaps between the obstruction shadows S. Therefore, conventionally, the reason why the robot is moved along a complicated trajectory such as a spiral instead of a simple straight line as described above is to lengthen the trajectory to more even out the obstacle shadows, and to search for all the gaps in the obstacle shadows. It can be said that it was done like this.

Based on the above consideration, the present invention is based on the above considerations, and to put it simply, the transmitted Considering that it represents the value closest to the X-ray absorption value of the substance,
An object of the present invention is to provide an X-ray tomography apparatus that improves the image quality of tomographic images.

An embodiment of the present invention will be described below. Third
In the figure, an X-ray tube 1 and an X-ray transmission image detection device 4 face each other with a subject 3 in between, and they move relative to each other so that a straight line connecting them always passes through a point O on a cut surface 31 of the subject 3. The points are similar to the conventional one. Here, the X-ray transmission image detection device 4 includes an image intensifier 41 and a television camera 42.
This television camera 42
A video signal output from the camera is stored in an image memory 51. That is, this image memory 51 has storage sections corresponding to each pixel of an X-ray transmission image photographed by the television camera 42, and receives a synchronization signal from a synchronization circuit 52 which supplies a synchronization signal to the television camera 42. A video signal for each pixel is stored in a corresponding storage section. Second
To explain with a diagram, first, the video signal of the pixel at point A obtained at the position X ₁ -A ₁ is written into one storage section. Next, when the video signal of the _pixel at point _A is obtained at the position are compared in the comparison circuit 53. Then, the switching circuit 54 is controlled based on the comparison result, and the one with the higher level of both video signals is written into the same storage section as above.

If we focus on the pixel at a certain point A in the X-ray transmission image taken by the television camera 42 in this way, we get
The highest level video signal obtained while the X-ray tube 1 and imaging device 4 move along various trajectories will be stored in the storage section corresponding to this pixel. In other words, among the X-rays that passed through point O on the cutting surface 31, data based on those that were least absorbed by materials other than the cutting surface are finally extracted, and the X-rays of the material near point O The data closest to the absorption value is obtained. Since this is also done for all other pixels, the stored content of the image memory 51 at the end of the orbital movement is the one least affected by the obstacle shadow for each pixel, and this is used for television. When displayed on the monitor 55, a tomographic image on the cut surface 31 with excellent image quality can be obtained.

Note that in the above embodiment, the video signal level is compared for each pixel and the highest one is extracted, but the method is not limited to this, and the highest one within a certain range or the lowest one can be selected ( It is possible to make various changes depending on the application (for example, when the signal level is inverted). Furthermore, as a device for obtaining an electrical video signal of an X-ray transmitted image, in addition to the image intensifier and television camera as described above, it may also be configured by combining a fluorescent plate or a mirror camera and a television camera. , a large number of X-ray sensors arranged two-dimensionally, or one-dimensional or two-dimensional X-ray sensors that can be scanned.
It can also be constructed using one or more dimensional X-ray sensors.

As described above with respect to the embodiments, according to the present invention, it is possible to obtain an X-ray tomographic image of excellent image quality in which obstructive shadows are removed. Furthermore, it is only necessary to add an X-ray transmission image detection device for obtaining electrical video signals of X-ray transmission images, an image memory, a signal processing circuit, etc. to the conventional X-ray tomography system that uses film, so it is possible to use the so-called computer tomography system. There is no need to newly install a mechanical mechanism for special scanning such as a photographing device, and there is no need for an expensive computer, so it can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional X-ray tomography apparatus, FIG. 2 is a schematic diagram for explaining the principle, and FIG. 3 is a block diagram of an embodiment of the present invention. 1... X-ray tube, 2... Film, 3... Subject, 41... Image intensifier, 42
...TV camera, 51...image memory,
52...Synchronization circuit, 53...Comparison circuit, 54...
Switching circuit, 55...television monitor.

Claims (1)

[Claims] 1 An X-ray tube device and an X-ray transmission image detection device are placed facing each other with a subject in between, and the devices are moved relative to each other while the straight line connecting the two devices always passes through one point on the cut surface of the subject. In the ray tomography apparatus, the X-ray transmission image detection device is configured with a device for obtaining an electrical video signal of the X-ray transmission image, and has a storage section corresponding to each pixel of the X-ray transmission image obtained from this device. An image memory is provided, which compares video signals for each pixel of the X-ray transmission image obtained at each position of the relative motion, and based on the comparison result, images of pixels to be stored in each storage section of the image memory. An X-ray tomography apparatus characterized in that a signal is determined.