JPS58165825A - Method and apparatus for taking tomographic x-ray photography - 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] The present invention relates to tomography.

Tomography shows a clear image of only a thin layer of the object.

Other areas penetrated by the X-rays appear dim as a result of the simultaneous movement of the X-ray source and film cassette during the exposure.

Linear tomography and panoramic tomography are distinguished by clear differences in their results and the parameters used. In linear tomography, only one frame is exposed by the X-rays in its width, and only the part of the object that is focused on the center of rotation of the X-rays or that passes through the center and reaches the central plane is clear. Show photos. The thickness of the imaged layer is determined by the rotation angle. In known devices, the x-ray source and the film cassette are not in a relatively stationary relationship, so that the angles of the x-ray beam and film plane and/or the distance between the x-ray source and the film cassette arrangement vary. The amount of shooting varies.

Usually, the movement of the film cassette and the X-ray source takes place in a linear manner.

・In ξ-norama tomography, the rotation angle is usually somewhat large. The film is advanced within the film cassette simultaneously with the rotation of the film cassette and the x-ray source, and the film is continuously exposed through a narrow slot in the front of the film cassette as the film is advanced a portion of the frame at a time. The clearly visible panoramic layer is determined by the film transport speed. That is, the point of the object irradiated with X-rays at a speed equal to the speed of the film will be clearly imaged on the film.

Particularly in skull tomography, both linear and panoramic tomography can be used effectively since there are many different types of objects to be imaged. Many possibilities of radiography are guaranteed if there is a device capable of both linear and panoramic tomography. Such equipment is of course expensive. On the other hand, when linear and panoramic tomography are required for the same subject, it is difficult to direct two separate devices to exactly the same point on the subject.

The present invention aims to overcome these drawbacks in the prior art and to enable linear and panoramic tomography to be obtained with one device. The aim of the invention is to provide a simple, easy to operate and reliable radiographic device which offers many tomographic possibilities.

Hereinafter, the present invention will be explained based on embodiments shown in the accompanying drawings.

Reference numeral 1 designates a stationary frame in which an X-ray source 2 and a film cassette device 4 are movably set. As shown in FIGS. 1 and 2, the X-ray source 2 and the film cassette device 4 are supported by a rotating member 15 so as to be rotatable around a rotating shaft 7, and the rotating member 15 is vertically supported by a bearing. It is attached to a movable slide member 16. Rotation of the rotating member 150 is performed by a motor 14, and movement of the slide 8 member 16 is performed by a stepping motor 12 and a screw mechanism 16. The apparatus further comprises a film transport device 3, primary collimator means 8 and secondary collimator means 9, the primary collimator means 8 being associated with the X-ray source 2 and directing the X-ray beam to be focused onto the object 5. A secondary collimator means 9 is attached to the cassette device 4 to determine the path of the X-rays transmitted through the object 5 to the film, or the size of the aperture 10. In panoramic tomography, the collimator means 9 limit harmful diffused X-rays from entering the film.

Furthermore, the illustrated device has a light projector 11 which generates a light emitting line and makes it possible to position the object 5 so that a desired layer of the object can be imaged and the imaging can be repeated. The lights from the projectors intersect at right angles,
It can indicate the axis of rotation. Since the same initial position with respect to the subject can be obtained with great precision for the X-ray source 2 and the film cassette device 4, for example a microprocessor etc. It is easy to program the operations required to take pictures. The control system 6 controls different movements (movement of the sliding member 16, rotation of the rotating member 15,
The correct position and/or operating method for each element is selected, along with the correct parameter values for the film transport), and the monitoring and co-operation of each movement is carried out, so that the exposure is completely automatic. The selection of the method will be described in detail later.

FIG. 6 shows a film cassette device 4 according to the present invention. The device comprises a film support or cassette 22 and a guide plate 23 with collimator means 9 between them. the X-ray beam limiting plate acting as collimator means is movable in the direction of the arrow;
Its freedom of movement is determined by the guide 8 element 20.21. These movements can be performed automatically by known mechanisms.

As shown in Figure 3, the size of the aperture 10 is determined by the position of the collimator means. When the aperture 10 is maximized, the entire frame of film can be exposed at once. The exposed film frame is slightly curved according to the film support 220 curvature. Also, if necessary,
As shown in FIG. 4, a separate film cassette 30 can be used, in which case the film frame is flat. In this case, an element 24 for supporting the film cassette 60 is attached to the guide 9 plate 26. Further, in this case, since the film cassette 30 is stationary, the collimator means 9 is not activated and does not affect film exposure, so there is no need to move the collimator means.

FIG. 5 shows the collimator means 8. As shown, an electrically actuated mechanism 25 acts on the lever arm 26 and is adapted to pivot the limit plate 27 via a bearing 29. The limit plate changes the width of the aperture 28 through which the x-ray beam passes. Of course, the X-ray beam can also be restricted by other known methods.

Panoramic tomography is performed by the apparatus according to the invention as follows.

Collimator means 8, 9 are arranged to limit the x-ray beam emitted by the x-ray source 2 to form a relatively narrow x-ray fan beam. The layer of the object to be imaged is determined by selecting the transport speed of the film during its exposure through the aperture 10 limited by the collimator means 9 and by selecting other movement parameters. If all the parameters necessary for the exposure are programmed prior to the exposure, it is only necessary to select the required program so that the control system 6 makes the necessary adjustments and controls. occurs simultaneously with the somewhat wide rotational movement required by panoramic tomography (sliding member 1
6) As a result of the linear movement, the X-ray beam can be directed vertically at the layer to be imaged. This essentially minimizes distortion of the photo if the layer being photographed differs from the arc.

Taking linear tomograms with the device according to the invention is simply carried out by moving the collimator means into a position such that they pass the X-ray beam in a manner corresponding to the entire size of the film frame. In contrast to the above, when the film cassette shown in FIG. 4 is used, the collimator means 9 does not necessarily have to be moved. Also, the film transport device is not activated and the entire frame is exposed to the x-ray beam during the exposure. The thickness of the imaged layer is determined by the rotation angle.

In the present invention, the layer to be photographed can also be moved to a position a certain distance away from the rotation axis 7. This is done by moving the rotating shaft 7 with the sliding member 16 simultaneously with the rotational movement. The speed of this movement can be obtained from the following formula:

V = Wr where W is the angular velocity of rotation and r is the distance from the axis of rotation of the layer to be imaged.

Different parameter values used for linear tomography can also be preprogrammed to create different types of standard programs.

Furthermore, by varying the rotation speed to correspond to the selected rotation angle, the exposure time of the film in linear tomography can be kept constant.

[Brief explanation of drawings]

FIG. 1 is a plan view of the device according to the invention; FIG.
A side view of the figures; FIG. 6 is a collimator device for a film cassette device; FIG. 4 is a film cassette device; FIG. 5 is a collimator device for restricting X and @ entering the subject; Patent applicant Instrumentarium drawing engraving (
No change in content) 3jji:3 135-jFl Guide 2 Shishikishi 5 Procedural Amendment (Yuhashi) Commissioner of the Patent Office Wakagi Tasai, Mr. 1, Indication of Case Patent Application No. 746924 of 1987 2 , Relation to the name of the invention case Patent applicant's address

Claims (9)

[Claims] (1) having a stationary claim and an x-ray source and film cassette device movably mounted relative to the claim, the x-ray source and film cassette device being capable of positioning a subject therebetween; X transmitted through the subject
In a method of taking linear and panoramic tomographic radiographs with a device in which the line beam is always directed at the same angle onto the exposed film, the relative positioning of the object and the device is determined according to the selected layer to be imaged. After that, X
The radiation source and the film cassette device are rotated around a common rotation axis by a predetermined angle according to the selected imaging method and image range, and at the same time the X-ray beam is irradiated onto the subject and the film in the film cassette device is rotated. When taking linear tomography, the subject and the entire image area of the film are exposed simultaneously while the film remains stationary relative to the cassette device, and panoramic When taking tomographic photographs, the subject is continuously placed on the film while the film is being transported at the required speed of 8 to the layer to be photographed, exposing only part of the subject and the film at a time. A method of taking exposed tomographic X-ray photographs. (2) In order to move the layer to be imaged to a position a certain distance away from the rotation axis, simultaneously with the above rotation, move the rotation axis along the direction of the plane determined by the layer selected to be imaged using the following formula. 2. A method as claimed in claim 1, characterized in that the movement is performed at the indicated speed V. v=wr Here, W is the same speed of the above rotation, and r is the distance from the rotation axis of the layer to be photographed. (3) The method according to claim 1 or 2, wherein the layer to be photographed of the object is indicated by coordinates determined by a ray of light incident at right angles to indicate the axis of rotation. (4) In taking a linear tomographic photograph, the exposure time of the film is kept constant by changing the rotation speed according to the selected rotation angle. Method described in Crab. (5) A film cassette device (
4), and the X-ray source and film cassette device are arranged so that the X-ray beam passing through the object always irradiates the plane of the film at the same angle.
In the device for taking radiographs, the X-ray source r2) and the film cassette device (6) are rotated around a constant rotation axis (7) by an angle determined by the selected imaging method and image area. means (14) and control device (6) for and main collimator means (8) for confining the X-rays to a narrow fan beam before they enter the subject;
and a secondary collimator means (9) provided between the subject and the film cassette device (4) having slots 8) mainly corresponding to the fan-shaped beam, and primary and secondary collimators for taking a norama tomogram. t8), (9) and the film transport device (3) so that the film is continuously irradiated with the fan-shaped X-ray beam that has passed through the subject through the above slot (GO), and to take a linear tomogram. A tomographic X-ray photographing device in which the main and sub-collimators (8L (9) and the film transport device are stopped, the film is kept stationary, and the entire image field is exposed at once. (6) Claim 5, wherein the film cassette device has a support member (c) for supporting a separate film cassette (to) having a flat film for linear tomography photography. Equipment described in Section. (7) The support member (c) is connected to the second collimator device (9).
) and the subject (5). (8) A device according to any one of claims 5 to 7, wherein the axis of rotation (7) is indicated by orthogonally intersecting rays of light emitted by a projector (11). (9) In order to move the layer to be photographed by a certain distance from the rotation axis (7), the rotation axis (force) is applied simultaneously with the rotation movement at a speed expressed by the following formula in the direction of the plane determined by the layer. A device according to any one of claims 5 to 8, adapted to transfer the layer, V = Wr, where W is the angular velocity of the rotational movement and r is the distance by which the layer is transferred from the axis of rotation. .