JPS6255867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tomography apparatus that facilitates positioning.

Computerized tomography equipment is one of the radiological diagnostic equipment.
There is an X-ray tomography device called tomography (hereinafter referred to as a CT device).

This CT device has, for example, an X-ray tube that emits flat Fan beam X-rays that spread out in a fan shape, and an X-ray detection device that has a large number of X-ray detection elements arranged side by side, facing each other across the tomographic plane of the subject. The fan beam X-rays are emitted toward the X-ray detection device, and each time the X-ray is emitted, the angle relative to the tomographic plane is changed by one degree, and the process is repeated. After collecting X-ray absorption data for various angles of the tomographic plane, this data is analyzed by a computer, the X-ray absorption rate of each position on the tomographic plane is calculated, and the gradation level is calculated according to the absorption rate. This reconstruction allows the composition of each part of the tomographic plane to be analyzed in as many as 2,000 gradations, making it possible to obtain clear tomographic images of everything from soft tissue to hard tissue.

By the way, in such a CT device, the thickness of the X-ray beam irradiated to the tomographic plane of the subject depends on the purpose of the diagnosis, for example, a few millimeters for a preliminary diagnosis, and a few millimeters for a detailed diagnosis. The beam is narrowed down to the thickness of 0.5mm and irradiated onto the tomographic plane of the subject to be inspected.

At this time, especially when the thickness of the tomographic plane to be viewed is several millimeters and you want to make a detailed diagnosis, the thickness of the X-ray beam is narrowed down according to the thickness of the tomographic plane, that is, the slice width. Accurately position the subject in advance with respect to the CT device gantry (mechanical pedestal that houses and supports the X-ray tube and X-ray detection device) so that the X-ray beam passes through the plane (the position of the desired tomographic plane). It is necessary to set it to .

In other words, since the slice width is narrow, even a small amount of
This is because if the irradiation position of the line beam deviates from the desired position, an image of the intended tomographic plane cannot be obtained.

Also, when slicing a wide tomographic plane or slicing to any other width,
It is important to position the slice in advance so that the slice will be sliced at the desired slice position, in order to prevent unnecessary X-ray exposure and to prevent various wastes such as the trouble of re-imaging and the waste of film. be.

However, when determining this position, it is necessary to plan in advance which cross-sectional plane of the subject to image, and generally an X-ray television device or the like is used to compare the suspicious area and its surroundings. Fluoroscopy and X-ray photography are performed over a wide range of areas, and the slice position is determined based on the preliminary diagnosis results.

After the position is determined in this way,
The position of the tomographic plane of the subject on the top plate is determined relative to the gantry, and then the top plate is slid by the distance to the position of the X-ray beam to perform positioning.

This situation is shown in FIG. That is, in the figure,
1 is an X-ray tube, 2 is an X-ray detection device, 3 is a gantry that accommodates these and whose tilt angle can be adjusted, and 3a is an imaging hole for inserting a subject into the gantry.

XR represents the X-ray beam emitted by the X-ray tube 1, and S represents the slice width using its thickness. 4 is the top drive stand, 5
is a subject, and 6 is a top plate on which the subject 5 is placed. The top plate 6 is provided on the top plate drive stand 4, and its height position is adjusted and slid by the top plate drive stand 4, and the subject 5 is placed in the imaging hole 3 of the gantry 3.
Move it into a. A is a cross section of the subject 5 to be photographed, and 7 is a positioning device installed above the photographing hole 3a of the gantry 3 and emits a fan beam light for positioning. This positioning fan beam light is emitted so that it has the same irradiation field as the X-ray beam XR.

In such an apparatus, if the cross section to be photographed of the subject 5 placed on the top plate 6 is A, then
The fan beam of the positioning device 7 is aligned with this cross section A. Since this fan beam light and the X-ray beam XR passing through the imaging hole 3a of the gantry 3 are in a parallel state, if the fan beam light and A match, the X-ray beam XR and cross section A match.

In such a method, cross section A is the X-ray beam
What completely matches XR is that the imaging hole 3a is narrow because positioning is done within the imaging hole 3a of the gantry 3.
The position of the X-ray beam XR irradiation field, which is several tens to several tens of centimeters deep, is extremely difficult for the operator (physician) to see directly with the naked eye, and in practice it is extremely difficult to align the position.

In addition, as shown in Fig. 2, a fictitious photographing position is set a distance L from the actual photographing position, and a floodlight is used to emit fan beam light FB at an appropriate position on the wall or ceiling of the room outside the gantry 3. 7, and after aligning the cross section A of the subject 5 to be photographed using this fan beam light FB, the top plate 6 is sent by a distance L into the photographing hole 3a of the gantry 3, and the X-ray beam XR is Some are designed to align with the irradiation field. Since this method performs positioning externally, it is superior to the above-mentioned method in terms of operability, but since the projector 7 is installed on a wall or ceiling, it is difficult to maintain accuracy, and especially when projecting light from a wall, Fan beam light FB during alignment
There is a drawback that the operator has to either block or take a position where it is easy to block. Furthermore, if the cross section A of the subject 5 to be photographed is tilted, the gantry 3 must be tilted to match the slope of the cross section A to perform the photograph. fixed in a certain direction,
In addition to being unable to perform positioning on such an inclined cross section, there are other disadvantages such as the need to provide a highly accurate tilting device that is linked to the gantry 3 if positioning is to be possible. .

The present invention has been made in view of the above-mentioned circumstances, and by providing a floodlight at the entrance of the photographing hole of the gantry and positioning the cross section of the subject to be photographed there, positioning can be easily performed and it can be An object of the present invention is to provide a tomography apparatus that can easily and accurately position the cross section of the object.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. FIG. 3 is a side view showing the configuration of this device, in which 1 is an X-ray tube, 2 is an X-ray detection device, 3 is a gantry, 3a is an imaging hole,
Reference numeral 4 indicates a top plate drive base, 5 indicates a subject, 6 indicates a top plate, and 7 indicates a floodlight that emits a fan beam light FB for positioning. This projector 7 is attached to the upper position of 3a. And this floodlight 7
is set in advance so that the line beam XR from the X-ray tube 1 and the fan beam light FB emitted from the projector 7 are parallel to each other. Further, the fan beam light FB is in a positional relationship that is shifted in parallel to the X-ray beam XR, and is separated by a distance L1. The gantry 3 is generally configured to be rotatable so that the inclination angle of the imaging hole 3a can be adjusted around the imaging hole center position O in the X-ray beam irradiation field within the imaging hole 3a, and this inclination angle is adjusted. A drive device is provided for adjusting the tilt angle upon command.
As a drive device for adjusting this inclination angle, for example, a rack 3b is attached to the bottom side of the gantry 3, a pinion 11a that meshes with the rack 3b is attached to the base of the gantry 3, and the pinion 11a is connected to the motor 1.
1, the inclination angle of the gantry 3 can be controlled. Similarly, for the top plate 6, a rack 6a is attached to the top plate 6, a pinion 12a that meshes with the rack 6a is attached to the motor 12 provided on the top plate drive base 4 side, and the pinion 12a is rotationally driven by the motor 12, so that the gantry 3 is rotated. The top plate 6 is configured to move forward and backward relative to the photographing hole 3a. The rotation of each motor 11, 12 is controlled by a motor control circuit 13, 15 for controlling the motor.
Although not shown, the gantry 3 is provided with a detector that obtains information on its inclination angle. The simplest method for this detector is, for example, using an encoder that generates an output corresponding to the rotation angle of the motor 11 on the gantry side. The tilting of the gantry 3 is carried out by the computer 16 of the CT device determining the control amount in response to a command given from the operation console 17 and giving this to the motor control circuit 15. Similarly, this configuration is implemented by the computer 16 determining the control amount in response to a command given from the console 17, and providing this to the motor control circuit 13, and is no different from the configuration of a general CT device. However, this device is further provided with a correction circuit 14 that uses the inclination angle information obtained from the detector to perform correction using a set of calculations described later, and the control amount after correction by this correction circuit 14 is used in the motor control circuit. Try to give it to 13.

In this device with such a configuration, if the gantry 3 is vertical and the cross section of the subject 5 to be photographed is vertical, the subject 5 can be photographed using the fan beam light FB from the projector 7 at the entrance of the photographing hole 3a. By positioning the target cross-section and then moving the top plate 6 toward the gantry 3 by a distance L1, the cross-section to be imaged of the subject 5 can be aligned with the irradiation field of the X-ray beam XR.

Next, if the cross section to be photographed is tilted, tilt the gantry 3 according to the slope of the cross section, and match the fan beam light FB of the projector 7, so that the irradiation field of the X-ray beam XR also crosses the cross section. However, since the gantry 3 is tilted, the distance from the position determined by the fan beam light FB to the irradiation field of the X-ray beam XR differs from the above-mentioned L1. That is, when the gantry 3 is tilted by an angle θ with respect to the perpendicular line, the feeding amount L2 of the top plate 6 is as follows.

L2cosθ=L1 ∴ L2=L1/cosθ ...(1) Therefore, the inclination angle θ is obtained by the detector that obtains information on the inclination angle θ of the gantry 3, and this is used to calculate the inclination angle θ for the feed amount L given by the computer 14. ,
By multiplying the feeding amount L1 by 1/cos θ and making a correction using the correction circuit 14, and giving it to the motor control circuit 13 as the feeding amount of the top plate 6 to send the top plate 6, the cross section of the object 5 and the X-ray beam It is possible to accurately match the irradiation field.

In this way, place an X at the entrance of the gantry's photographing hole.
Fan beam light FB parallel to the radiation field of line beam XR
The projector projects the fan beam light FB to align the cross-section of the object to be imaged, and then sends the object into the imaging hole and aligns it with the irradiation field of the X-ray beam XR. Even if the cross-section to be photographed is tilted, all you need to do is tilt the gantry so that the fan beam light FB matches the cross-section to be photographed, making positioning settings simple and easy. Since the gantry is located near the entrance of the photographing hole, the operator can set the position at a position that is very easy to see without blocking the fan beam light, and when the gantry is tilted, the inclination angle θ It has excellent features such as the ability to align the X-ray beam position with the cross-section to be photographed extremely accurately by using a calculation circuit etc. to calculate the feed amount of the top plate to be corrected by 1/cosθ in accordance with the feed amount. It is possible to provide a tomography apparatus having the following.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope of the gist. If projectors 7a and 7b are added to the left and right sides near the opening of the photographing hole 3a of the gantry 3, and the fan beam light is applied from three directions around the outer circumference of the subject 5, positioning becomes even more accurate. Setting operations are also easier.

[Brief explanation of the drawing]

1 and 2 are side views showing a conventional example, FIG. 3 is a view for explaining one embodiment of the present invention, and FIG. 4 is a front view showing another example. 1... X-ray tube, 2... X-ray detection device, 3... Gantry, 3a... Imaging hole, 3b, 6a... Rack, 5... Subject, 6... Top plate, 7, 7a, 7b
...Floodlight, A...Cross section to be photographed, XR...
...X-ray beam, FB...Fan beam light, 11,
12...Motor, 11a, 12a...Pinion,
13, 15...Motor control circuit, 14...Correction circuit, 16...Computer.

Claims (1)

[Scope of Claims] 1. Detection in which a predetermined cross-sectional area at a predetermined imaging position within the imaging hole is set as a detection field of view in a gantry having an imaging hole for placing a subject, and incoming radiation in the detection field of view is detected. A detector is installed, and this detector is used to detect radiation from a radiation source obtained from a cross section to be imaged of the subject placed at the imaging position from various directions, and collect data on the detected radiation of the cross section. By analyzing the
In the tomography apparatus for reconstructing an image of the cross section, the gantry is provided with an inclination angle adjustment mechanism so that the inclination angle of the imaging cross section can be adjusted, and the gantry has the detection field of view near the opening of the imaging hole. A light projector is provided for projecting a light beam for positioning a cross section of the object to be photographed in a state parallel to the surface, and
The position of the subject after positioning of the cross-section to be photographed by the projector is provided on the subject moving/holding means which has a drive mechanism and carries the subject and moves it in parallel to send it to the photographing hole and hold the subject. A calculating means for correcting the distance from 1. A tomography apparatus characterized in that the tomography apparatus is configured to control the feeding of the subject by the subject moving and holding means after the positioning by the amount of feeding. 2. The calculation means maintains the movement of the object by 1/cos θ (θ is the inclination angle of the detection field of view of the gantry) when the angle formed by the forward/backward axis of the object moving and holding means with respect to the gantry and the detection field of view of the gantry is not a right angle. 2. The tomography apparatus according to claim 1, wherein the tomography apparatus is configured to apply correction to the amount of the object fed by the means.