JPS58116342A - Computer tomography apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a computed tomography apparatus (hereinafter abbreviated as CT apparatus), and particularly to an improvement of an R4 (Rotate-Rotate) type CT apparatus.

R-R Hojo's CTi! At f, as shown in FIG. 1, the radiation l! An irradiation device, such as an X-ray tube 1, and an array 2 of radiation detectors, such as a combination of a scintillator and a photomultiplier, are placed facing each other with a subject (patient) 3 in between. Column 2 and subject 3
Rotate 360° around the central axis O of fiK. During this rotation, the transmission of object 3 from each detector in the detector row 2G
Data related to line intensity is collected and this data is subjected to arithmetic processing to reconstruct the distribution image of the xII absorption coefficient in the subject 3, and this distribution image is output as a tomographic image to a television monitor or the like for display. etc.

By the way, in this case, as shown in Fig. 1, the rotation center axis is 0.
The imaging area 4 is a circular area inscribed in the fan shape formed by the X-ray beam incident on the detector row 2 with the center at . This shooting S
The pin 4 may be small for photographing the head, but a large one is required for photographing the chest or waist. Conventionally, the field of view can be changed according to the imaging area, for example, by changing the distance between the xlI tube l and the detector array 2 by moving them together toward the subject 3 while keeping the distance constant. In the case of a large field of view, the detector row 2 approaches the object 3 and the XlI tube 1 moves away, indicating a good condition; in the case of a small field of view, the inverse KX-ray tube 1 approaches the object 3, and the detector row 2 moves away from the object 3. I'm trying to keep it at a distance. Therefore, it is necessary to move the xIiI tube 1 and the detector row 2 together in a straight line relative to the subject 3, which has the disadvantage of being mechanically inefficient.

In view of the above, an object of the present invention is to provide an R4 type CT system that can switch between a large field of view and a small field of view with a simple mechanism.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.According to the present invention, in the case of a small field of view for head imaging,
As shown in FIG. 2, the KX-ray tube 1 and the detector row 2 face each other so that the straight line connecting X@lx and the central axis 0 of the subject 3 passes approximately through the center of the detector row 2, as in the conventional case. The detector row 2 is rotated around the X# tube 1, as shown in Figure 3, to ensure a wide field of view when photographing the chest, waist, etc. . That is, the detector array 2 rotates so that the center position of the detector array 2 deviates from the straight line connecting the xiIil tube 1 and the central axis O of the subject 3, and in this FIG. ! ! Connect tube 1 and central axis 0! Detector row 2 until one end of detector row 2 is located on the line.
is α, /! (α is the fan-shaped opening angle that the detector row 2 makes with the X1Ii! tube 1) by one rotation.

When the detector row 2 is rotated to this point, the area of the angle α from the straight line connecting the X# tube 1 and the central axis O will be covered by the Xl/a beam. At this time, Xa tube 1 must also be rotated by 9 α/2, or XI! If the focal point of the tube 1 is sufficiently small and the X@radiation angle covers the entire moved detector row 2C, it is sufficient to keep the Fi identification.

When photographing the head 31, the field of view is small ζ as shown in Figure 2.
At this time, the Bukage Hironkusu region 4 is a circular region 41 (the radius of which is R) that is inscribed in a fist shape with an angle α centered on the central axis 0.

When photographing the chest or lower back, proceed as shown in Figure 3. Then, while maintaining this state, the Oxa tube 1 and the detector array 2 are rotated 3600 times around the central axis 0. It can be seen that in the position shown in FIG. 3, only the right half of the chest 32 is irradiated with the radiation beam, or, considering the state of 1800 rotations, the left half is also irradiated. Therefore, 3600 rotations K
Therefore, the circular area 42 that is in direct contact with the straight line connecting the X-ray tube 1 and the central axis O at an angle α and whose center is at the angle 0 is the imaging area. The radius of this region 420 is 2B.

Therefore, it is possible to switch between a small field of view and a large field of view simply by rotating the detector array 2 around XINII and shifting its position. In addition, as can be seen from the comparison with Fig. 3, in the case of Fig. 1 and Fig. 2, the same data is obtained twice by rotating 3600 times, and that's all.
An improvement in i can be expected. Generally, in the case of head photography, the multiple fields of view, which are different from those of the chest and waist, can be small, but i! Excellent Ji is required, and conversely, in the case of the chest and lumbar region, the field of view must be large, but WJ quality is often required to be of the same quality, so it meets these actual requirements.

Although detailed mechanical configurations are omitted in Figures 2 and 3, the X-ray tube 1 and detector row 2 are fixed to the same frame, and this frame itself is rotated around the focal point of the XiI tube 1. All you have to do is make it possible.

In Fig. 3, the detector row 2 is changed by α/2 from the state shown in Fig. 2.
The X-ray tube is moved so that the detector row 2 is only on the right half, but it is rotated by an angle smaller than the α force so that part of the detector row 2 remains on the left half. 1 and the detector row 2 may be rotated. In this way, only a small circular area near the central axis 0 will be subject to data acquisition twice, and the image quality in this area will be improved. Therefore, it is possible to obtain an image in which the image quality is good in the central part and the image quality is poor in the peripheral part.

As described above regarding the embodiments, according to the present invention, it is possible to easily switch between a large field of view and a small field of view with a simple mechanism. Further, even when the detector array is small, that is, the number of detectors is small, a large field of view can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional example, and FIGS. 2 and 3 are schematic diagrams of an embodiment of the present invention for connecting stations. 1...X11M tube 2...Detector row 3...
・Subject 4... Photography area applicant Shimadzu Corporation

Claims (1)

[Claims] (1) @ A radiation MN4 irradiation device and a radiation detector array, which are placed facing each other with the subject in between, are rotated together around the subject, and data regarding the transmitted radiation intensity of the subject with bangs is collected from the radiation detector array. In the combinator tomography apparatus, which processes this data to reconstruct a distribution image of radiation*absorption coefficients in the subject and outputs this distribution image as a tomographic image, the radiation detector The front r-radiation detector row is rotated around the radiation irradiation device so that the central position of the row is off the line connecting the front V-radiation*m radiation device and the center of rotation, and this rotated wiping motion is A combination tool-evening tomography IV in which the radiation irradiation device and the radiation detector array are integrally rotated around the subject.