JPH057583A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To achieve a spiral data collection by rotating an X-ray generator a plurality of times forwardly and reversely while a bed device is moved in the direction of the body axis of an object to be inspected to perform the same scanning as by a continuous rotation type X-ray CT apparatus with a simple and inexpensive construction. CONSTITUTION:An object 4 to be inspected carried on a bed device 2 is inserted into a tunnel part at the center of a gantry 1 and scanned by X rays to be generated from an X-ray tube rotating and built in the gantry 1. The gantry 1 and the bed device 2 are connected to a console 3 with a cable or the like. A control signal is outputted from the console 3 to control the bed feeding of the bed device 2 along with the rotation of the X-ray tube and an X-ray detector in the gantry 1 and the X-ray exposure. The X-ray tube and the X-ray detector in the gantry 1 are rotated a plurality of times forwardly and reversely while the bed device 2 feeds a bed in the direction of body axis of the object 4 to be inspected thereby achieving a spiral data collection with a simple and inexpensive construction.

Description

Detailed Description of the Invention

[0001]

This invention relates to an X-ray generator and an X-ray generator.
The present invention relates to a so-called third generation X-ray CT apparatus in which a line detector rotates, or a so-called fourth generation X-ray CT apparatus in which only an X-ray generator rotates.

[0002]

2. Description of the Related Art A conventional third-generation or fourth-generation X-ray CT apparatus usually has a structure in which a forward rotation and a reverse rotation are repeated every 360 °. This is because in order to be able to rotate continuously in one direction over 360 °, the electrical connection relationship including the power supply to the X-ray tube must be of the rotary type, which complicates the configuration. Because it becomes expensive.

This type of X-ray C that repeats normal and reverse rotation
In the T-apparatus, if rotation and bed feed are alternately performed,
It is possible to collect image data of many planes on the subject,
A three-dimensional image can be constructed. That is, FIG.
As shown in, at a position in the longitudinal direction Z of the subject 4,
After the data is collected by rotating in the positive direction from the point to the point b by 360 °, the subject 4 is moved in the Z direction by sending the bed, and this time, it is rotated in the opposite direction from the point c to the point d by 360 °. Collect data. If such forward / reverse rotation and bed feed are alternately repeated and data is collected at a large number of positions in the Z direction, a three-dimensional image of the subject 4 can be created.

[0004]

However, in the X-ray CT apparatus of the type in which the forward rotation and the reverse rotation are repeated as in the prior art, the rotation of the X-ray tube (and the X-ray detector) and the bed feeding are alternately performed. When collecting three-dimensional data about a subject, sequential control of operations is required, such as rotating the X-ray tube (and X-ray detector) and then feeding the bed. However, there is a problem that it takes time to collect data. This point, X-ray tube (and X-ray detector)
In the X-ray CT system of the type that continuously rotates the
If the bed is fed while continuously rotating, the subject is scanned in a spiral shape, so that three-dimensional data can be collected in a short time. However, in this case, in order to continuously rotate the X-ray tube (and the X-ray detector), a rotary type electrical connector such as a slip ring is required, which makes the configuration complicated and expensive.

In view of the above, the present invention is an X-type X-ray generator (and X-ray detector) of the type that repeats forward and reverse rotations.
An object is to improve so that spiral data acquisition can be performed using a line CT apparatus.

[0006]

In order to achieve the above object, in the X-ray CT apparatus according to the present invention, the X-ray generator is rotated four times in such a manner that the directions of rotation are alternately forward and reverse, During the first rotation and the second rotation, the subject is moved in one direction at a predetermined speed, and then the subject is moved until the fourth rotation is started to move in the movement direction. The position of the X-ray generator at the time when the fourth rotation is completed by moving the subject in the opposite direction at the same speed as above during the fourth rotation, The feature is that it is set to the position when is finished.
As a result, the data collected in the first rotation and the fourth data
According to the data collected in the above rotation, it is possible to configure the same data as the spiral data collected by moving the subject while continuously rotating the X-ray generator twice.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the gantry 1
It contains an X-ray tube, an X-ray detector, and a rotating device for rotating them in the forward and reverse directions by 360 °. The subject 4 placed on the top plate of the bed apparatus 2 is inserted into the central tunnel portion, and is scanned by the X-ray generated from the rotating X-ray tube. The gantry 1 and the bed apparatus 2 are connected to a console 3 with a cable or the like, and control signals and data are transmitted and received. The console 3 has a built-in computer for control and image reconstruction, and is further provided with a monitor device for image display, a keyboard device for input, and the like. For example, by operating the keyboard device, a control signal is issued from the console 3, and the X-ray tube and the X-ray detector in the gantry 1 are rotated and the X-ray is exposed, and the bed feeding in the bed device 2 is controlled. To be done. The data obtained from the X-ray detector in the gantry 1 is sent to the console 3 and undergoes a predetermined image reconstruction process to reconstruct the image, which is displayed on the monitor device.

Here, the X-ray tube and the X-ray detector in the gantry 1 first rotate 360 ° in the forward direction and then 3 in the reverse direction.
It is controlled to rotate 60 °, rotate 360 ° in the forward direction, and rotate 360 ° in the reverse direction again. in the meantime,
The bed apparatus 2 is controlled so that the bed (top plate) is fed in the body axis direction (Z direction) of the subject 4, and the subject 4 moves in the Z direction.
Can be moved in the direction.

More specifically, during the first 360 ° positive rotation, the bed is fed in the Z direction, and as shown in FIG. 2, the scan is performed from the point a to the point b of the subject 4.
Note that in FIG. 2, the subject 4 is shown as a column for convenience of explanation. Next, a rotation pause period is provided, and during that period, the bed is fed in the Z direction, so that a linear scan such as b → c is performed. Then rotate in the opposite direction,
In the meantime, the Z-direction bed feed is continuously performed at the same speed as the above-described a → b → c, which means that a spiral scan such as c → d is performed. After that, it further rotates in the forward direction, and during the forward rotation period, the bed is fed in the direction opposite to the Z direction by a distance corresponding to the bed feeding distance in the rest period of b → c, and the spiral empty space is moved from d → e. Do a scan. Then, rotation is performed in the opposite direction from this point e. During this reverse rotation, the bed is fed in the opposite direction to the Z direction at the same speed as the above a → b → c → d. Then, a spiral scan e → f is performed, and the point f coincides with the point b. The relationship between the scan angle θ and the Z-direction position here is as shown in FIG.

Combining the scan e → f with the scan a → b is the same as when the X-ray tube and the X-ray detector are continuously rotated while the bed is fed at a constant speed in the Z direction. This means that the spiral scan of can be performed. That is, an X-ray CT of the type in which normal rotation and reverse rotation are alternately repeated.
The device can also scan the same orbit as the continuously rotating type. In this case, if the forward rotation / reverse rotation switching pause period of b → c is further shortened, the distance of b → c is also shortened. Accordingly, the distance of d → e in the Z direction can be shortened accordingly, and higher speed can be achieved. is there.

When the data collected between a → b and the data collected between e → f are combined to reconstruct one tomographic image, two data at the same angle θ are added. At that time, the distance between the sampling positions (Z direction positions) of the two data having the same angle θ to be added is the same at any angle θ. Therefore, the data of the same angle θ can be simply added regardless of the angle θ, and then the image reconstruction processing can be performed, whereby a good image can be obtained.

[0012]

As described above with reference to the embodiments, according to the present invention, the X-ray CT apparatus of the type in which the forward / reverse rotation of the X-ray generator is repeated is exactly the same as the continuous rotation type X-ray CT apparatus. It becomes possible to collect data by performing a spiral scan.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a scan trajectory for a subject in the embodiment.

FIG. 3 is a graph showing a relationship between a rotation angle θ and a Z direction position in the example.

FIG. 4 is a schematic diagram showing a scan trajectory for a subject in an X-ray CT apparatus of a type in which a forward rotation / reverse rotation of an X-ray generator according to a conventional example is repeated.

[Explanation of symbols]

 1 Gantry 2 Bed device 3 Operator's table 4 Subject

Claims (1)

Claim: What is claimed is: 1. A first rotation in the forward direction is performed, a second rotation is performed in the reverse direction, a third rotation is performed in the forward direction, and then a reverse rotation is performed. X-ray generating means for performing a fourth single rotation of the subject, and the subject is moved in one direction at a predetermined speed during the first rotation and the second rotation, and then the fourth
During the fourth rotation, the subject is moved in the opposite direction at the same speed as above, and the subject is moved in the opposite direction during the fourth rotation. An X-ray CT apparatus, comprising: a subject moving means for causing the position of the X-ray generation means at the time of completion of rotation to be the position at the time of completion of the first rotation.