JPS6347457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tomography apparatus that uses a computer to reconstruct a radiation image on a tomographic plane perpendicular to the body axis of a human body.

In this type of tomography device, for example, when performing tomography of the head using a whole body device, it is desirable to improve the image resolution and improve the image quality.
There is also a desire to perform a so-called real zoom, which improves the accuracy of images only in a specific imaging area, to examine a specific part of a patient particularly closely.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved tomography apparatus that can easily improve the image quality of only a specific imaging area.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, an X-ray tube 1 is supported to rotate on a circumferential orbit 11 with a small radius, and an X-ray tube 2 is supported so as to rotate on a circumferential orbit 11 with a larger radius, which is concentric with the circumferential orbit 11. It is supported so that it rotates on top. Each of these X-ray tubes 1, 2
emits a fan-shaped radiation beam with a predetermined spread toward its rotation center O. An X-ray detector row 1 is installed at the position where each of these X-ray beams is incident.
2, 22 are arranged, and each X-ray detector row 1
2 and 22 rotate together with the X-ray tubes 1 and 2, that is, at the same angular velocity, and are supported so as to detect the X-ray beam no matter what rotational position the X-ray tubes 1 and 2 are in. X-ray tubes 1 and 2 (and detector row 1
2 and 22) rotate in the same direction (for example, in the direction of the arrow) while maintaining the relative angles shown in the figure. Note that a variable collimator 23 is provided so that the angle of the X-ray beam from the X-ray tube 2 can be changed. The subject 3 is placed near the center of rotation O of the X-ray tubes 1 and 2. Note that the focal size of the X-ray tube 1, which has a smaller radius of rotation, is designed to be smaller than the focal size of the X-ray tube 2, which has a larger radius of rotation.

FIG. 2 shows a second embodiment. In the embodiment shown in this figure, the X-ray detector array 15 is fixed on the entire circumference, and the X-ray beams from either X-ray tubes 1, 2 are The only difference is that the light is incident on the detector array 15, and the other points are the same as in FIG. 1, so the same numbers are given to the same parts and the explanation will be omitted.

Next, the operation of the embodiment shown in FIGS. 1 and 2 will be explained. First, in the case of whole-body photography, X-rays are emitted only from the X-ray tube 2 in the general photography mode. In this way, a tomographic image of normal image quality can be obtained. In addition, in the case of head photography, in the general photography mode, X-rays are emitted only from X-ray tube 1,
The X-ray tube 2 is turned off. Then, since the X-ray tube 1 is close to the subject 3, an enlarged image of the head (a subject small enough to fit within the small imaging area 4 near the center) can be obtained. Since the focal size of the X-ray tube 1 is small, the X-ray beam elements are finely divided (1
(the width of each beam is small), and images with excellent spatial resolution can be obtained. In this case, since the spread angle of the X-rays from the X-ray tube 1 is large, the utilization efficiency of the X-rays is high.

Then, during the above-mentioned whole body imaging, if X-rays are emitted not only from X-ray tube 2 but also from X-ray tube 1,
Because the beam elements of the X-rays from the If the image is reconstructed, a highly accurate image will be obtained. Note that in the figure, the X-rays from X-ray tube 1 cover the same imaging area as the X-rays from X-ray tube 2, but in reality the X-ray tube 1 is centered at 0. Because it is difficult to make the fan-shaped spread angle of the X-rays that large, the X-rays from the X-ray tube 1 can often cover only a small imaging area 4. Since highly accurate data can be obtained only in a specific area included, the image accuracy of the reconstructed image is improved only in that specific area. Therefore, so-called real zoom makes it possible to particularly closely diagnose a specific part of the patient.

In addition, in the case of a small subject 3 such as a head,
If X-rays are emitted not only from X-ray tube 1 but also from X-ray tube 2, two pieces of data can be obtained regarding one corresponding X-ray transmission path; In comparison, it is the same as using twice the X-ray dose. In other words, if you emit X-rays from X-ray tubes 1 and 2 and rotate them once, you can obtain data by emitting X-rays only from X-ray tube 1 and obtain data by rotating twice (or twice as long). The same amount of data can be obtained (obtained by slow rotation). Therefore, if these data are used, the S/N ratio of the data will be improved, and a highly accurate image can be reconstructed using these data (a so-called precision mode can be realized). At this time, the head, which is subject 3, is smaller than the whole body.
Since it fits within the imaging area 4, the variable collimator 23
is operated to narrow the spread angle of the X-ray beam emitted from the X-ray tube 2. This precision mode is possible when the subject 3 falls within the area covered by both the X-ray beam emitted from the X-ray tube 1 and the X-ray beam emitted from the X-ray tube 2. In such a case, it is not necessarily only the head, but in reality, as mentioned above, the X-ray tube 1 is close to the center 0, and it is difficult to make the fan-shaped spread angle of the X-rays that large. Since the lines can often cover only a small imaging area 4, this is limited to cases where the subject 3 is small, that is, imaging of the head or the like.

As described above with respect to the embodiments, the tomography apparatus of the present invention has two radiation sources that simultaneously rotate on two large and small concentric orbits, and the focal point of the radiation source that rotates on a circular orbit with a small radius. Because it is smaller, just by turning on and off each of these radiation sources, you can shoot in normal shooting mode, real zoom mode, etc. that correspond to the size of the subject.
Each shooting mode such as precision mode can be selected immediately, and switching between each mode is easy and does not take much time, making it extremely convenient.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG. 2 is a block diagram showing a second embodiment. 1, 2...X-ray tube, 12, 15, 22...X-ray detector row, 23...variable collimator, 3...subject.

Claims (1)

[Claims] 1. A first radiation source with a smaller radiation focus that rotates on a circular orbit with a small radius and emits a fan-shaped radiation beam with a predetermined spread toward the center of rotation, and a circle concentric with the circular orbit. a second radiation source that rotates on a circular orbit with a large radius and emits a fan-shaped radiation beam with a predetermined spread toward the center of rotation; and radiation from the first and second radiation sources. a plurality of radiation detectors for detecting beams, and the radiation beam is emitted from one or both of the first and second radiation sources while both radiation sources are simultaneously rotated. Photography equipment.