JPH07124149A - CT scanner - Google Patents

Abstract

(57) [Abstract] [Purpose] The rotation angle of the rotary scanning mechanism and the feed amount of the subject feeding mechanism are made to completely correspond to each other, and the spiral scanning is performed in the correct positional relationship. [Structure] The rotation of a rotation scan mechanism driving motor 13 in the gantry 10 is detected by a shaft encoder 14, and its pulse is sent to a control device 31, and a motor 22 for driving a bed top 21 is made to correspond to the pulse. Control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CT scanner having a rotary scanning mechanism and a subject feeding mechanism, such as an X-ray CT apparatus, an emission CT apparatus using a positron or a single photon emitting nuclide.

[0002]

2. Description of the Related Art In a CT scanner having a rotary scanning mechanism and a subject feeding mechanism, it is conventionally known that a subject is spirally scanned by moving the subject while rotating it. In this case, conventionally, the rotary motion of the rotary scan mechanism and the linear motion for moving the subject are independently controlled, and the speed control of both the rotary motion and the linear motion and the start timing of those motions should be matched. Therefore, the accuracy of the data acquisition position is ensured. In other words, the accuracy of the data acquisition position during these two movements is improved by independently increasing the accuracy of each of the movements.

[0003]

However, with the conventional configuration in which the accuracy of the data acquisition position is maintained by independently controlling the rotary scanning mechanism and the subject feeding mechanism and independently increasing the accuracy thereof, If the rotational speed of the rotary scan mechanism is uneven or the linear movement speed of the feed mechanism is uneven, data cannot be obtained in the correct positional relationship, and such uneven speed does not occur. It is generally difficult to perform such control.

In view of the above, it is an object of the present invention to provide a CT scanner improved by synchronizing the movements of both the rotary scanning mechanism and the subject feeding mechanism so that their positional relationships strictly correspond. To do.

[0005]

In order to achieve the above object, according to the present invention, in a CT scanner including a rotary scanning mechanism and a moving mechanism for moving an object with respect to the rotary scanning mechanism, It is characterized by having means for detecting the rotation of the scanning mechanism and control means for controlling the movement amount of the moving mechanism by the rotation detection output.

[0006]

Since the rotation of the rotary scanning mechanism is detected and the movement amount of the moving mechanism for moving the subject is controlled by the rotation detection output, the rotation angle of the rotary scanning mechanism and the movement amount of the subject are completely synchronized. Even if there is unevenness in the rotation of the rotary scanning mechanism, it is possible to perform spiral scanning with an accurate positional relationship.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. 1 and 2 show an X-ray CT apparatus to which the present invention is applied. First, in FIG. 1, the bed top plate 2 is attached to the tunnel portion 11 of the gantry 10.
A subject (patient) 20 placed on 1 is inserted. The bed top plate 21 is adapted to move linearly in a direction of entering and retreating with respect to the tunnel portion 11. The drive is performed by the motor 22 via an appropriate mechanism. The motor 22 is controlled by the control device 31, and an output pulse from the shaft encoder 14 which detects the rotation of the motor 13 for driving the rotation scanning mechanism in the gantry 10 is input to the control device 31.

As shown in FIG. 2, a ring-shaped rotating frame 15 is concentrically arranged inside the gantry 10 so as to be rotated by a motor 13 via an appropriate mechanism. There is. The rotating frame 15 includes an X-ray tube 16 and a detector 17, and a tunnel portion 11
It is attached so as to face each other across. As a result, the X-rays from the X-ray tube 16 are applied to the subject 20 inserted in the tunnel portion 11, and the X-rays transmitted through the subject 20 are detected by the detector 17. Then, when the rotary frame 15 is rotated by the motor 13, the subject 20 is scanned with X-rays from each direction.

Here, as described above, the rotary motion of the rotary scanning mechanism is detected by the structure in which the rotation of the motor 13 is detected by the shaft encoder 14, and the detected rotary motion is detected. The rotation of the motor 22 for driving the bed top plate 21 is controlled in synchronization. That is, for example, in the control device 31, the output pulse from the shaft encoder 14 is divided or doubled, and the motor 2 is output according to the pulse amount thus generated.
Control the rotation angle of 2. When a pulse motor is used as the motor 22, the generated pulse itself is used by the motor 2.
Enter in 2. In this way the shaft encoder 1
Since the rotation angle of the motor 22 is controlled according to the output pulse of No. 4, the linear movement distance of the bed top plate 21 is completely synchronized with the rotation angle of the rotating frame 15.

Therefore, in this way, the rotating frame 15
If the X-ray tube 16 irradiates X-rays and collects data from the detector 17 in a state in which the rotation angle of X and the feed amount of the subject 20 are synchronized, the rotation speed of the rotation frame 15 was uneven. Even in this case, it becomes possible to perform a spiral scan in which the positional relationship is accurately determined.

As described above, the rotating frame 15 holds the X-ray tube 16, the detector 17, etc., and these rotate together, so that the weight of the rotating portion is generally 400-.
It will be about 500 kg. The rotation speed is about 60 rotations per minute, which is a high speed. Therefore, it is expected that such rotation is constant to some extent due to inertia, and conversely, it is difficult to control this rotation with good responsiveness due to inertia and the like. Therefore, as in the above embodiment, the bed top plate 21 and the subject 2 are referenced based on this rotation.
On the contrary, controlling the linear motion of 0 is easier and more accurate than controlling the rotary motion based on the feed amount.

The control device 31 includes a shaft encoder 14
In addition to the output pulse from, the pulse from the pulse generation circuit 32 is input, and these can be arbitrarily switched in the control device 31. Therefore, as described above, if the output pulse from the shaft encoder 14 is selected and the motor 22 is controlled by this, the spiral scan with high position accuracy can be performed, but the pulse from the pulse generation circuit 32 is selected. If the motor 22 is controlled accordingly, the bed top 21 and the subject 20 are independent of the rotational movement of the rotary scanning mechanism in the gantry 10.
The feed amount can be set. For example, the rotation of the rotary frame 15 is stopped and the X-ray tube 16 and the detector 17 are kept at a constant angle to irradiate X-rays to collect data, and a motor is generated according to a pulse from the pulse generation circuit 32. By driving 22 to move the bed top plate 21 and the subject 20 at a constant speed, a CR image of the subject 20 can be taken. In addition, when a CT image is obtained for each of a plurality of slices, the bed top plate 21 is associated with each slice position.
It is also possible to repeat the movement and the stop of and rotate the rotating frame 15 at the time of the stop to perform the scan.

Although the rotation of the motor 13 is detected by the shaft encoder 14 in the above description, the rotation frame 15
It can be variously modified without departing from the gist of the present invention, such as being configured to directly detect the rotation of the. Further, although the above-mentioned embodiment is a so-called third generation X-ray CT apparatus,
The detector is arranged all around and only the X-ray tube rotates. The 4th generation X-ray CT device or the detector is arranged all around, and the X-ray tube is also ring-shaped. The present invention can also be applied to an X-ray CT apparatus or the like that uses a so-called electron beam scanning X-ray tube in which only an electron beam that generates rays rotates. Further, although one embodiment in which the present invention is applied to the X-ray CT apparatus has been described above, the present invention can also be applied to other CT scanners including a rotary scanning mechanism and a subject feeding mechanism such as an emission CT apparatus. Of course.

[0014]

As described above with reference to the embodiments, according to the CT scanner of the present invention, the rotation angle of the rotary scanning mechanism and the feed amount of the subject feeding mechanism can be perfectly associated with each other, and the correct positional relationship can be obtained. Spiral scan can be performed to eliminate errors in data acquisition position.

[Brief description of drawings]

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

FIG. 2 is a schematic front view of a gantry part.

[Explanation of symbols]

 10 gantry 11 tunnel part 13 rotation scanning motor 14 shaft encoder 15 rotation frame 16 X-ray tube 17 detector 20 subject 21 bed top 22 bed top drive motor 31 controller 32 pulse generator circuit

Claims (1)

[Claims] 1. A CT including a rotary scanning mechanism and a moving mechanism for moving an object with respect to the rotary scanning mechanism.
The scanner is provided with a means for detecting the rotation of the rotary scanning mechanism and a control means for controlling the movement amount of the moving mechanism by the rotation detection output.
T scanner.