JP2006340954A - X-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus which can autodiagnose with a subject laid. <P>SOLUTION: The X-ray CT apparatus comprises a rotor 3, an X-ray tube 4 and an X-ray detector 5, a shifting means 7, a collimator 8, an opening/closing means 8c, an X ray detecting means 9, a comparing means, and a regulating means 10. The rotor 3 rotates around a subject. The X-ray tube 4 and the X-ray detector 5 are positioned opposite to each other on the rotor 3 to sandwich the subject. The shifting means 7 shifts the X-ray tube 4 along the body axial of the subject. The collimator 8 narrows an X ray 6 ejected from the X-ray tube 4 to the subject. The opening/closing means 8c opens and closes the collimator 8. The X-ray detecting means 9 detects the X-ray output of the X-ray tube 4. The comparing means compares a predetermined value with the X-ray output which is detected by the X-ray detecting means 9 when the shifting means 7 shifts the X-ray tube 4 with the collimator 8 completely closed. Also, the regulating means 10 autodiagnoses the deviation in focus of the X-ray tube 4 based on a comparison result given by the comparing means. The apparatus can prevent the subject from being exposed in vain, because the collimator 8 is completely closed while the X-ray CT apparatus lay the subject on a bed 2 to autodiagnose. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray CT apparatus capable of self-diagnosis of an apparatus in a state where a subject is placed on a bed.

Conventional X-ray CT apparatuses that perform tomographic imaging of a subject using X-rays are based on a rotating body in which an X-ray tube and an X-ray detector are arranged at positions facing each other with the subject interposed therebetween. It is configured to perform tomography by rotating.
In the X-ray CT apparatus having the above-described configuration, when the X-ray tube is operated for a long time, the anode in the X-ray tube expands and contracts due to thermal expansion due to heat generation of the X-ray tube. There is a problem that X-rays emitted from the X-ray tube do not hit the X-ray detector.

In recent years, the rotating body has been rotated at a high speed to enable high-speed scanning. However, there is a problem in that the focal point of the X-ray tube is shifted due to the centrifugal force generated at that time, in order to improve these problems. In recent X-ray CT apparatuses, scanning is performed while monitoring the output signal output from the X-ray detector, and if the output from the X-ray detector decreases due to the defocus of the X-ray tube, the X-ray tube X-rays irradiated from the X-ray tube are reliably detected by moving the collimator plate provided near the X-ray tube or moving the X-ray tube itself in the direction of defocus (in the body axis direction of the subject). Countermeasures are taken so that the light is received by the detector (eg, Patent Document 1).
The X-ray CT apparatus described in Patent Document 1 has a drive mechanism that moves the X-ray tube in the body axis direction. When the anode of the X-ray tube expands and contracts due to thermal expansion or the like, the focus shifts. After correcting the error due to the X-ray X-ray output, the shift amount of the focal position is detected by the X-ray detector, and the movement of the X-ray tube is controlled in the body axis direction of the subject to correct the defocus. It is like that.
JP-A-6-178769

  However, in the X-ray CT apparatus that detects the defocus of the X-ray tube by monitoring the output of the conventional X-ray detector, in order to avoid the exposure of the X-ray to the subject, the X-ray CT apparatus is in a very early stage. Even if the measurement operation is stopped after measuring the output of the X-ray detector and detecting an abnormality as a result, there is a problem that invalid exposure to the subject cannot be avoided.

On the other hand, when the X-ray emitted from the X-ray tube is detected as in the X-ray CT apparatus described in Patent Document 1 and the focus of the X-ray tube is shifted, the X-ray tube is moved in the body axis direction. In the case of correcting the shift by moving, the X-ray is directly detected and the amount of focus shift is measured, so the above problem does not occur. However, the X-ray CT apparatus is provided with a self-diagnosis function. When measuring the defocus of the X-ray tube by the self-diagnosis function, the self-diagnosis must be performed in a state where the subject is not placed on the bed in order to avoid invalid exposure to the subject.
For this reason, it takes a long time from the self-diagnosis of the X-ray CT apparatus to the actual X-ray imaging of the subject, and there are problems such as poor work efficiency.
The present invention has been made to remedy such a problem, and an object of the present invention is to provide an X-ray CT apparatus capable of self-diagnosis of an apparatus with a subject lying down.

  An X-ray CT apparatus of the present invention includes a rotating body that rotates about a subject, an X-ray tube and an X-ray detector that are arranged on the rotating body so as to face each other with the subject interposed therebetween, and an X-ray tube Shift means for shifting in the body axis direction, a collimator for narrowing the X-rays irradiated to the subject from the X-ray tube, an opening / closing means for opening and closing the collimator, and an X-ray detection means for detecting the X-ray output of the X-ray tube And the X-ray output detected by the X-ray detection means when the X-ray tube is shifted by the shift means in the fully closed state of the collimator and a preset set value are compared. It comprises a comparison means and a control means for self-diagnosis of the X-ray tube defocus based on the comparison result of the comparison means.

With the above configuration, even if the X-ray CT apparatus performs self-diagnosis with the subject placed on the bed, the collimator is in the fully closed state, so that it is possible to prevent invalid exposure of the subject in advance. Since the time from the self-diagnosis of the X-ray CT apparatus to the actual X-ray imaging of the subject can be greatly shortened, the work efficiency at the time of tomography improves.
In addition, since the X-ray output detection accuracy is improved by directly detecting the X-rays emitted from the X-ray tube, the self-diagnosis accuracy is also improved.

  The X-ray CT apparatus of the present invention is provided with display means for displaying a self-diagnosis result determined by the control means.

  With the above-described configuration, when an abnormality occurs in the X-ray tube or a defocus occurs before tomographic imaging of the subject or during imaging, the X-ray CT apparatus is operated according to the self-diagnosis result displayed on the display means. By stopping automatically or manually, X-ray imaging is not performed while the X-ray output is lowered, thereby improving the safety of the X-ray CT apparatus and viewing the self-diagnosis result displayed on the display means. Therefore, maintenance can be performed easily.

  According to the X-ray CT apparatus of the present invention, self-diagnosis of the X-ray CT apparatus can be performed in a state where the subject is laid on a bed, so that invalid exposure of the subject can be prevented in advance.

Embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an X-ray CT apparatus, FIG. 2 is a schematic diagram thereof, and FIG. 3 is a flowchart showing a self-diagnosis method.
A gantry 1 of the X-ray CT apparatus shown in FIG. 1 has a circular opening 1a at the center, and a bed 2 for placing a subject (not shown) horizontally at the center of the opening 1a. is set up.
In the gantry 1, a disk-like rotating body 3 that rotates about the subject is provided, and the X-ray tube 4 and the X-ray detector 5 are opposed to the rotating body 3 with the subject interposed therebetween. Is arranged.
The X-ray tube 4 irradiates the subject with X-rays 6. The X-ray 6 transmitted through the subject is detected by the X-ray detector 5, converted into an electrical signal, and an image (not shown) as an output signal. It is output to the processing means.
The X-ray detector 5 is formed in an arc shape centered on the focal point of the X-ray tube 4, and a large number of light receiving element groups (in the channel direction orthogonal to the body axis of the subject) are formed on the light receiving surface of the X-ray 6. (Not shown) are arranged, and the light receiving element groups are arranged in a plurality of rows in the body axis direction (slice direction).

The X-ray tube 4 can be shifted in the body axis direction of the subject by the shift means 7.
The shift means 7 is composed of an electric motor 7a whose rotation is controlled by a control means 10 which will be described later, and a shift mechanism 7b such as a worm gear which is rotationally driven by the electric motor 7a and shifts the X-ray tube 4 in the body axis direction. A collimator 8 for collimating the X-ray 6 into a fan-shaped beam and an X-ray detection means 9 for detecting the defocus of the X-ray tube 4 from the output of the X-ray 6 are provided immediately below the X-ray tube 4. Yes.
The collimator 8 is formed by a pair of shutter plates 8b facing each other with a slit 8a forming a fan-shaped beam, and each shutter plate 8b can be opened and closed steplessly from a fully closed state to a fully open state by an opening / closing means 8c. By changing the width of the slit 8 by opening and closing each shutter plate 8b in the body axis direction of the subject, the slice width of the X-ray 6 that slices the subject can be arbitrarily adjusted. .

On the other hand, the output of the X-rays 6 irradiated from the X-ray tube 4 toward the subject is detected by the X-ray detection means 9 installed in the vicinity of the collimator 8.
The X-ray detection means 9 detects a part of the X-ray 6 generated from the anode 4a of the X-ray tube 4, and the output of the X-ray tube 4 detected by the X-ray detection means 9 is It is sent to the control means 10.
The control means 10 is connected to a console 11 installed at a position distant from the X-ray CT apparatus. By operating the console 11, self-diagnosis of the X-ray CT apparatus and the focus of the X-ray tube 5 are achieved. Adjustments can be made.

Next, a self-diagnosis method of the X-ray CT apparatus will be described with reference to the flowchart shown in FIG.
When taking an X-ray tomographic image of a subject with an X-ray CT apparatus, a self-diagnostic button (not shown) is set when the photographing mode is set in step S1 of FIG. The shutter plate 8b of the collimator 8 is in a fully closed state at this time.
Next, the X-ray 6 is irradiated from the X-ray tube 4 at the same time as the rotating body rotates. However, since the collimator 8 is in the fully closed state, the X-ray 6 does not reach the subject, thereby invalidating the subject. There is no exposure.

Next, the process proceeds to step S2, and the control means 10 determines whether the X-ray tube 2 is shifted in the body axis direction of the subject by the shift means 7 and whether the X-ray output of the X-ray tube 2 has reached a predetermined output at step S3. Is determined.
When the control means 10 determines that the X-ray output of the X-ray tube 2 has reached a predetermined output, the process proceeds to step S4 and the output of the X-ray 6 irradiated from the X-ray tube 2 is converted to the X-ray detection means. 9 measures and sends the measured value to the control means 10.
The control means 10 is provided on the console 11 when the X-ray output sent from the X-ray detection means 9 has reached a preset set value and it is determined that the X-ray tube 2 has no defocus. At the same time, the display unit 12 displays the self-diagnosis result as normal, and at the same time, the operation of the X-ray CT apparatus is permitted, and the measurement operation of the X-ray output is terminated in step S5.

On the other hand, if it is determined in step S3 of the flowchart shown in FIG. 3 that the X-ray output of the X-ray tube 2 has not reached the predetermined output, the process proceeds to step S6, and the X-ray output is measured by the X-ray detection means 9. Is stopped and the process proceeds to step S7.
In step S7, a self-diagnosis for searching for the cause of the error from the error information of the data stored in the control means 10 is executed.
In step S8, it is determined whether the X-ray output can be measured from the self-diagnosis result. If the measurement is possible, the process returns to step S1, and the flow is repeated again from step S1.
If it is determined in step S8 that measurement is impossible, the self-diagnosis result indicating that the operation of the X-ray CT apparatus is impossible is displayed on the display means 12 of the console 11 together with the content of the error, and at the same time, the X-ray CT apparatus. Is prohibited, and the measurement ends in step S5.

The above is the action of self-diagnosis before tomography by the X-ray CT apparatus in the state where the subject is laid on the bed, but the same flow is repeated during tomography of the subject, and the X-ray tube 4 X-ray output and defocus of the X-ray tube 4 are monitored.
If an abnormality occurs in the X-ray output of the X-ray tube 4 or the X-ray output decreases due to defocusing of the X-ray tube 4, the flow from step S3 to step S8 is executed, and as a result, an error is confirmed. If the measurement is impossible due to the error content, the error content and the fact that the X-ray CT apparatus cannot be operated are displayed on the display means 12 of the console 11, and the X-ray CT apparatus is stopped at the same time. Then, subsequent operation is prohibited.
As a result, even when the X-ray output of the X-ray tube 4 decreases during the tomography of the subject or when a defocus occurs, the X-ray CT apparatus is automatically stopped, so that the subject is ineffectively exposed. It can be prevented in advance.

  The X-ray CT apparatus of the present invention can perform self-diagnosis of the X-ray CT apparatus while the subject is laid on a bed, and is optimal for an X-ray CT apparatus that performs tomography of the subject.

1 is a schematic configuration diagram of an X-ray CT apparatus according to an embodiment of the present invention. 1 is a schematic diagram of an X-ray CT apparatus according to an embodiment of the present invention. It is a flowchart which shows the self-diagnosis method of the X-ray CT apparatus which becomes embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gantry 3 Rotating body 4 X-ray tube 5 X-ray detector 7 Shift means 8 Collimator 8c Opening / closing means 9 X-ray detection means 10 Control apparatus 12 Display means

Claims (2)

  A rotating body that rotates about the subject, an X-ray tube and an X-ray detector arranged on the rotating body so as to face each other with the subject interposed therebetween, and the X-ray tube in the body axis direction of the subject Shift means for shifting, collimator for narrowing X-rays irradiated to the subject from the X-ray tube, opening / closing means for opening and closing the collimator, and X-ray detection means for detecting the X-ray output of the X-ray tube An X-ray CT apparatus comprising: an X-ray output detected by the X-ray detection means when the X-ray tube is shifted by the shift means in a fully closed state of the collimator; and a preset set value; An X-ray CT apparatus comprising: comparing means for comparing the first and second control means; and control means for self-diagnosis of defocus of the X-ray tube based on a comparison result of the comparing means. The X-ray CT apparatus according to claim 1, further comprising display means for displaying a self-diagnosis result determined by the control means.

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