JPH0547209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an X-ray CT apparatus (X-ray computerized tomography apparatus), and particularly relates to an improvement of a Rotate-Rotate type X-ray CT apparatus.

(b) Prior Art In X-ray CT devices, artifacts tend to occur around large X-ray absorbing objects such as the base of the brain due to partial volume effects (partial object effects). Therefore, in order to solve this problem, the present inventor divided the X-ray detector into multiple parts in the slice thickness direction, logarithmically converted the signals obtained from each part of these multiple divided parts, and then added them together and blocked them. proposed to form file data
(See Publication No. 66246).

By the way, usually Rotate-Rotate type X-rays
Although CT devices are becoming popular, applying the above methods to them poses the problem of significantly increasing costs. In other words, Rotate-Rotate type X-ray CT
As is well known, the device includes an X-ray emitting device and
The X-ray emitting device has a large number of rows of X-ray detectors arranged opposite to the X-ray emitting device, and the X-ray emitting device and the detector row are rotated around the object placed between them. This method collects profile data and processes this profile data using a computer to reconstruct a tomographic image related to the X-ray absorption rate distribution in a specific slice plane of the subject. Since there are a large number of X-ray detectors, dividing each of them in the slice thickness direction would result in a very large total number of detectors and a large number of data acquisition devices connected to each of them. This is because it will be put away.

(C) Purpose This invention is based on the fact that the areas where artifacts occur are actually limited to relatively small anatomical areas such as the base of the brain and the spine, and that only X-ray detectors that can deal with such small areas can be used. We focused on the fact that artifacts caused by the partial volume effect can be improved by dividing the slices in the thickness direction, and by sharing data acquisition devices, we can reduce the number of data acquisition devices and suppress cost increases.
Rotate-Rotate type X-ray CT that solves the problem of artifacts due to partial volume effect
The purpose is to provide equipment.

(D) Configuration According to the present invention, the present 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. and the object placed between them to collect profile data, and by processing this profile data with a computer, the X-ray absorption rate distribution in a specific slice plane of the object is determined. In a Rotate-Rotate type X-ray CT system that reconstructs tomographic images related to A number of data collection devices at least corresponding to the total number of divided portions in the central predetermined portion are provided, and a signal of each portion of the divided portions in the central predetermined portion is sent to each of these data collection devices by a switching device. The signals of the parts in the same column position are added together, and the signals of the detectors of the undivided parts are sent as they are, and the data of each part of the divided parts in the central predetermined part is obtained from each of the data acquisition devices. If there are data in the same column position, 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.
A subject 4 is placed between them, and this subject 4
The X-ray tube 1 and the detector row can be rotated around the center. 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 not divided in this way. There is one piece in each slice thickness direction.

Then, one data acquisition device is connected to each one of the detectors 2, respectively. In other words, it is necessary to connect one data collection device to each divided portion of the detector 2 in the H section, but this increases the number of data collection devices and increases costs. Therefore, 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 128 detectors are assigned to each of the two B parts, and the detectors 2 in these parts are numbered B1 to B128 and B129 to B256 in FIG. It is attached. Each of the 256 pieces in the H section is divided into two in the thickness direction, making a total of 512 pieces, numbered H1 to H512, with an odd number followed by an even number (for example, H1 and H512).
2, H3 and H4) form one detector in the column direction. When the switch SB is pushed to the upper side of 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, in the same way as when the detector 2 is not divided at all in the slice thickness direction at the H section,
You can get 512 channels of signals arranged in rows.
On the other hand, flip the switch SB to the bottom of the diagram, and then
When SH is turned off, 512 signals are obtained from each of the divided detectors 2 of the H section, making a total of 512, and no signal from the B section is obtained. for that,
In this way, by switching the switches SB and SH, the data collecting device 3 can be shared, and 512 data collecting devices 3, D1 to D512, can be used.
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 switch SB is moved to the upper side of the figure and switch SH is turned on, the signals of each part divided in H part are added as they are, and in H part the detector 2
Data of 512 channels arranged in the column direction is obtained, which is the same as when the slice is not divided in any way in the thickness direction. 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 1 and the detector array, and is processed by the CPU using an image reconstruction algorithm. The tomographic image can be reconstructed by 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 switch SB is pushed down to the bottom of the figure and switch SH is turned off, only data from detector 2 in section H can be obtained. In other words, this is the case for a small imaging area, such as when imaging the head. Each of the detectors 2 in the H section has 2
Since the data are divided, each data acquisition device 3 obtains data S1 to S512 with a slice thickness that is 1/2 of the slice thickness of the detector 2 in section B, and these data are processed in the CPU as follows. First, they are each logarithmically transformed and then added to each other to obtain 256 channels of data Pi (i=1 to 256) arranged in the column direction Pi=1nS2i-1+1nS2i. The data of each of these 256 channels is data regarding the normal slice thickness (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 conversion, and this profile data can be used by rotating the X-ray tube 1 and the detector row. obtained from each direction and processed by the image reconstruction algorithm on the CPU.
A tomographic image with reduced artifacts caused by volume effects can be reconstructed.

Here, the detector 2 was divided into two only in the central H area, but since artifacts caused by partial volume effects are likely to occur in relatively small areas such as the base of the brain and the spine, this should be improved. The area was made small, thereby reducing costs.

In some cases, data obtained from the detector 2 on one slice surface side (H1, H3, H5,...H511) and the data obtained from the detector 2 on the other slice surface side (H2, H4, H6,... It is also possible to process the data obtained from H512) as two sets of data.

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 these can be switched.
The data collection device 3 can be used effectively in any case of head photography or whole body photography, and a large number of detectors 2 can be arranged.
Detector 2
and the number of data collection devices 3 can be reduced,
Cost increases can be avoided as much as possible.

(F) Effect Rotate-Rotate type X-ray according to this invention
With CT equipment, the data acquisition device can be used effectively in both head imaging and whole-body imaging, and because the number of detectors and data acquisition devices can be reduced, it is possible to reduce the number of detectors and data acquisition devices. image quality can be improved. Furthermore, since the slice thickness can be increased, the patient's throughput can be improved and the patient's exposure dose 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. 1...X-ray tube, 2...detector, 3...data acquisition device, 4...subject.

Claims (1)

[Claims] 1 It has an X-ray emitting device and a row of many X-ray detectors arranged opposite to this X-ray emitting device, and these X-ray emitting devices and the detector row are placed between them. X In the line CT device, a plurality of detectors in a central predetermined portion of the large number of detectors constituting the detector row are divided into a plurality of parts in the slice thickness direction, and the number of detectors at least corresponds to the total number of divided portions in the central predetermined portion. A switching device is used to send the signals of each part of the divided portion in the central predetermined portion to each of these data collecting devices, and the signals of the divided portions in the same column are added together and divided. If the data of each part of the divided part in the central predetermined part is obtained from each of the data acquisition devices, the signals of the detectors of the parts not covered are sent as they are, and if the data of each part of the divided part in the central predetermined part is obtained, the signals of the detectors in the same column position are X-rays are characterized in that they are logarithmically transformed and then added together to form brochure data.
CT device.