JPS6129340A - X-ray ct 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 (A) Field of Industrial Application This invention relates to an X-ray CT apparatus (X-ray computed tomography apparatus), and particularly relates to an improvement of a Rotate-Rotate type X-ray CT apparatus.

(B) Conventional technology □ In X-ray CT equipment, partia, l volume effects (
Therefore, in order to solve this problem, the present inventor divided the X-ray detector into a plurality of slices in the slice thickness direction, and obtained images from each of these multiple divided parts. proposed to logarithmically transform the signals and then add them together to form profile data (
(See Japanese Unexamined Patent Publication No. 56-66246).

Incidentally, the Rotate'-Rotate type X-ray CT apparatus is commonly used, but if the above-mentioned method is applied to this, a problem arises in that the cost increases significantly.

That is, Rotate-Rotate type X-ray C
As is well known, the T device includes an X-ray emitting device and a number of rows of X-ray detectors arranged opposite to the X-ray emitting device. is rotated around an object placed between them to collect profile data, and this profile data is processed by a computer to reconstruct a tomographic image regarding the X-ray absorption rate distribution in a specific slice plane of the object. However, since the number of X-ray detectors that make up the detector row is large, dividing each of these in the slice thickness direction would result in a very large number of detectors, and it would be difficult to connect each of them. This is because the number of data collection devices also becomes extremely large.

(C) Purpose This invention is based on the fact that the site where artifacts occur is actually limited to a relatively small anatomical region such as the upper vertebrae, and that the X-ray detector that corresponds to such a small region is sliced. Partia can also be divided in the thickness direction.
Rotate focuses on the ability to improve artifacts caused by the lmaolu effect, and also reduces the number of data collection devices by sharing data collection devices, suppressing cost increases and solving the problem of artifacts caused by the partial volume effect. -Ro
The purpose of the present invention is to provide a tate type X-ray CT device.

(D) Configuration According to the present invention, the invention includes an X-ray emitting device and a large number of rows of X-ray detectors arranged opposite to the X-ray emitting device,
Profile data is collected by rotating these X-ray emitting devices and detector rows around the object placed between them. In a Rotate-Rotate type Xl&l CT device that reconstructs a tomographic image related to a linear absorption rate distribution, a plurality of detectors in a predetermined central portion of a large number of detectors constituting the above-mentioned detector row are arranged in a plurality of detectors in the slice thickness direction. and providing a number of data collecting devices at least corresponding to the total number of divided portions in the central predetermined portion, and sending signals of each portion of the divided portions in the central predetermined portion to each of these data collecting devices by a switching device. The data of each part of the divided part in the central predetermined part is obtained from each of the data acquisition devices by adding the signals of the same column position of the divided part and sending the signals of the detectors of the undivided part as they are. If the data is located in the same column, the data at the same column position are logarithmically transformed and then added together to form profile data.

(E) Embodiment In FIG. 1, an X-ray tube 1 and a detector row in which a large number of X-ray detectors 2 are arranged are arranged facing each other, and a subject 4 is placed between them. X-ray tube l centered around 4
and the detector row can be rotated. In the detector row, the detectors 2 located in the H section at the center are each divided into two in the slice thickness direction, and the detectors 2 located at the end B section are divided into two in this way. There is one piece in each slice thickness direction.

Then, one data collection device is connected to each detector 2, that is, detection of each section divided in the H section! ! 2, it is necessary to connect one data collection device to each divided portion, but this increases the number of data collection devices, leading to an increase in cost. Therefore, 8
As shown in FIG. 2, the number of data collecting devices 3 is reduced by sharing the data collecting devices 3 by switching the switches SB and SH. That is, for example, suppose that 512 detectors 2 are arranged in the column direction, and 1 detector is placed in each of the two B sections.
28 detectors are allocated, and the detectors 2 in these parts are numbered BINB128, B129 to B256 in FIG. Each of the 256 pieces in the H section is divided into two in the thickness direction, making a total of 512 pieces, numbered Hl-H512, with an odd number followed by an even number (for example, Hl and H2, H3 and H4). Thus, one detector in the column direction is formed. When the switch SB is pushed upward in the figure and the switch SH is turned on, the signals of each section divided in the H section are added as they are. In other words, in this case, signals of 512 channels arranged in the column direction are obtained as in the case where the detector 2 is not divided at all in the slice thickness direction in the H section. On the other hand, when the switch SB is moved to the lower side of the figure and the switch SH is turned off, 512 signals from each detector 2, which is a total of 512 after dividing the H section, are obtained, and the signal from the B section is I can't get it. Therefore, by switching the switches SB and SH in this manner, the data collection device 3 can be shared, and the data collection device 3 only needs to be 512 DI-Ds 512. Each of the data acquisition devices 3 is composed of a preamplifier, an integrator, and an A/D converter, and obtains digital data from the signals related to X-ray attenuation obtained from each detector 2, and sends this to a CPU (not shown). send.

When the switch SB is turned upward in the diagram and the switch SH is turned on, the signals of each part divided in the H part are added as they are, and the same result as when the detector 2 is not divided in the slice thickness direction in the H part is added. Data of 512 channels arranged in the column direction is obtained. The data of these 512 channels constitute one profile data, and this profile data is obtained from each direction by rotating the X-ray tube l and the detector row, and is processed by the CPU using an image reconstruction algorithm. Images can be reconstructed. At this time, a wide area, that is, the area of the torso of the subject 4 can be covered, and normal image reconstruction is possible.
' When the switch SB is moved to the lower side of the figure and the switch SH is turned off, only the data from the detector 2 of the H section can be obtained.

In other words, this applies to a small imaging area, such as when imaging the head.

Since the detectors 2 in the H part are each divided into 1 and 2 parts, each data acquisition device 3 receives data 5l of slice thickness of the slice thickness of the detector 2 in the B part.
-3512 is obtained, and these are first logarithmically transformed and then added together in the CPU as follows, and data Pi (
i=1~2P i=l n52i-1+ I n5
2i is obtained. The data of each of these 256 channels is data regarding the normal slice thickness (the slice thickness of the detector 2 in section B), and one profile data is formed by the data of these 256 channels.

In this case, accurate profile data can be formed by adding the effectively thin slice thickness data after logarithmic transformation, and this profile data can be viewed from each direction by rotating the X-ray tube l and detector row. By processing these using an image reconstruction algorithm in the CPU, p
It is possible to reconstruct a tomographic image with reduced artifacts caused by the artificial lume effect.

Here, the detector 2 was divided into two only in the central H section, but p
The areas where artifacts caused by the artial volume effect are likely to occur are relatively small areas, such as the base of the brain and the vertebrae, so we aim to improve this area by selecting a small area, thereby reducing costs. I made it.

Note that in some cases, the detector 2 on one slice surface side
(Hl, H3, H5,...H511) and the detector 2 (H2, H511) on the other slice surface side.
4, H6,...H512),
It is also possible to process the data as two sets.

In this way, only a part of the detectors 2 arranged in large numbers are divided in the slice thickness direction, and the data acquisition device 3 is shared between each divided part and when not divided, and can be switched between them. The data collection device 3 can be used effectively in both partial and whole body imaging, and the detection speed is much faster than in the case where a large number of detectors 2 are all divided in the slice thickness direction and a data collection device 3 is provided for each. Vessel 2
The number of data collection devices 3 and the number of data collection devices 3 can be reduced, and an increase in cost can be avoided as much as possible.

(f) Effect of Rotaje-Rotate type X according to this invention
With X-ray CT equipment, the data acquisition device can be used effectively for both head and whole body imaging, and the number of detectors and data acquisition devices can be reduced, so it is possible to improve brain imaging without significantly increasing costs. The image quality of the bottom part etc. can be improved. Furthermore, since the slice thickness can be increased, the throughput for the patient can be improved and the radiation dose for the patient can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of the same embodiment.

Claims (1)

[Claims] (1) It has an X-ray emitting device and a row of many X-ray detectors arranged opposite to the X-ray emitting device, and the X-ray emitting device and the detector row are arranged between them. In an X-ray CT apparatus, which collects profile data by rotating an object placed as a center, and reconstructs a tomographic image regarding the X-ray absorption rate distribution in a specific slice plane of the object by processing the profile data by computer, Among the large number of detectors constituting the detector row, a plurality of detectors in a predetermined central portion are divided into a plurality of parts in the slice thickness direction, and a number of data acquisition devices at least corresponds to the total number of divided parts in the predetermined central portion. The signal of each part of the divided part in the central predetermined part is sent to each of these data acquisition devices by a switching device, and the signals of the parts of the divided part in the same column are added together to generate the signal of the detector of the part not divided. If the data of each part of the divided part in the central predetermined part is obtained from each of the data collection devices, the data in the same column are logarithmically transformed and then sent as is. An X-ray CT apparatus characterized in that profile data is formed by adding data.