JPH07275232A - X-ray ct device - Google Patents

Abstract

PURPOSE:To provide an X-ray CT device by which a specific slice thickness is obtained in a collimator by a means of continuously varying width in longitudinal direction at a passage of X-rays in the collinator. CONSTITUTION:X-rays irradiated from above pass through a gap surrounded by a pair of blades 21A, 21B arranged mutually in parallel. A blade guide 23A is disposed at both ends of the blades 21A, 21B. A blade interval setting guide 24A is disposed on the center side of the blades 21A, 21B, adjoining to the blade guide 23. The blade guide 23A is moved in arrow-B direction with a blade guide driving mechanism 26, so that the separation distance of the blades 21A, 21B, being mutually in paralleled relation, is varied continuously. Thus, a slice thickness corresponding to the separation distance of the blades 21A, 21B is set freely. Accordingly, in normal scanning, the slice thickness is set freely in relation with frequency of move of a table with a testee thereon, as desired.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an X-ray CT apparatus.

[0002]

2. Description of the Related Art In an X-ray CT apparatus, an X-ray tube and an X-ray detector, which face each other around a body axis of a subject, rotate, whereby information from the X-ray detector is rotated. Is an image diagnostic apparatus for creating a tomographic image on a plane orthogonal to the body axis of the subject.

In this case, the X-rays from the X-ray tube are input to the X-ray detector with a predetermined spread angle via a so-called collimator. In other words, the X-ray width of the subject in the body axis direction can be set to a predetermined value.

This X-ray width corresponds to the so-called slice thickness of the subject, and the tomographic image shows image information such as organs present within this slice thickness.

Conventionally, this X-ray width is, for example, 1
It can be set to 0 mm, 5 mm, 3 mm, and 2 mm, and so-called scan conditions, that is, tube current, scan time, table movement amount, and the like can be set accordingly.

[0006]

However, the X-ray CT apparatus configured as described above has a selection branch for only some set slice thicknesses and cannot set other slice thicknesses. Came to be pointed out.

This has often caused the following problems.

[0008] For example, in the normal scan method in which tomographic images are sequentially obtained with a predetermined slice thickness along the body axis direction of the subject without gaps, for example, when a slice thickness of 10 mm is taken, a clearer image is obtained. When attempting to obtain the slice thickness, the slice thickness of the next stage is 5 mm, even though the number of intermittent movements of the table on which the subject is placed is increased and the amount of exposure to the subject is unnecessarily increased. I had no choice but to image it.

Further, the X-ray tube and the X-ray detector are constantly rotated, and the subject is moved in the body axis direction thereof.
In the volume scan method in which some tomographic images are obtained by performing interpolation processing on the information from the line detector, the moving speed of the table on which the subject is placed is usually limited, and a tomographic image with a desired effective slice thickness is obtained. I couldn't get it.

Therefore, the present invention has been made under such circumstances, and the object of the present invention is to obtain a predetermined slice thickness in a collimator X.
It is to provide a line CT apparatus.

[0011]

In order to achieve such an object, the present invention provides an X-ray tube and an X-ray detector which rotate about an imaginary axis as opposed to each other about the imaginary axis. In an X-ray CT apparatus including a collimator arranged at the X-ray irradiation port of the X-ray tube, there is provided means for continuously varying the width of the X-ray passage port of the collimator in the axial direction. It is a feature.

[0012]

According to the X-ray CT apparatus thus constructed,
In the normal scan method, a desired slice thickness can be freely set in relation to the number of movements of the table on which the subject is placed.

Therefore, it is possible to optimize the desired sharpness of the tomographic image in consideration of the exposure dose of the subject.

In the volume scan system,
Since the effective slice thickness can be obtained by using the moving speed of the table on which the subject is placed and the slice thickness that can be set to a free value as parameters, the effective slice thickness required even when the moving speed of the table is restricted. It becomes possible to obtain a thick tomographic image.

[0015]

FIG. 2 is a perspective view showing an embodiment of the X-ray CT apparatus according to the present invention.

In FIG. 1, there is a scanner 1, and this scanner 1 is provided with a measurement space 2 consisting of a through hole.

There is a bed 4 on which a subject is mounted, and this bed can be moved in the measurement space 2 by a drive mechanism (not shown).

As the bed 4 moves, the subject 3 mounted on the bed 4 moves along the central axis of the measurement space 2.

As shown in FIG. 3, which is a sectional view taken along the line III-III in FIG. 2, around the measurement space 2 in the scanner 1, an X-ray tube 11 that rotates about the central axis of the measurement space 2 is provided. And the X-ray detector 12 are arranged.

That is, the X-ray tube 11 and the X-ray detector 12 which are arranged to face each other with the subject 3 in the measurement space 2 in between.
Are provided, and the X-ray tube 11 and the X-ray detector 12 can be integrated to rotate around the subject 3.

Here, the X-ray detector 12 comprises a plurality (usually 320 to 1000) of detectors 1 in the rotation direction thereof.
2N are arranged as a group of detectors arranged side by side, and a tomographic image of the subject 3 (a tomographic image cut by the rotating surfaces of the X-ray tube 11 and the X-ray detector 12 is obtained from the output of each detector 12N during rotation. ) It is designed to create data.

The X-ray tube 11 is provided with a collimator 14 at its X-ray irradiation port, and the collimator 14 narrows the X-rays into a predetermined bundle of rays to irradiate the subject 3. . The collimator 14 will be described in detail later.

The signal from the X-ray detector 12 is input to the image processing apparatus 5 arranged outside the scanner 1, and the tomographic image created by this image processing apparatus 5 is displayed on the monitor 7. Has become.

When a tomographic image is created in this way,
It is known that there are a normal scan method and a volume scan method.

The normal scan method is a method for sequentially obtaining tomographic images with a predetermined slice thickness along the body axis direction of the subject 3 without gaps, and accordingly, the bed 4 is sequentially moved within the width of the slice thickness. It is designed to let you.

In the volume scan method, the X-ray tube 11 and the X-ray detector 12 are constantly rotated and the subject 3
Is moved at a constant speed in the body axis direction, whereby the signal from the X-ray detector 12 is subjected to interpolation processing to obtain some tomographic images.

Therefore, according to the adoption of each of these methods,
A bed movement control signal is sent from the image processing device 5 to the drive mechanism in the bed 4.

FIG. 1 is a perspective view showing an embodiment of the collimator 14.

An arrow A in FIG. 1 indicates a direction that is coincident with the direction in which the collimator 14 is observed in FIG.

In FIG. 1, there is a pair of blades 21A and 21B arranged in parallel with each other. Each blade 21
X-rays emitted from above in the drawing can pass through the space surrounded by A and 21B.

Blade guides 23A and 23B (not shown) are arranged at both ends of the pair of blades 21A and 21B, respectively, and a blade interval is provided adjacent to the blade guides 23A and 23B on the center side of the blades 21A and 21B. Setting guides 24A and 24B (not shown) are arranged.

Blade interval setting guides 24A, 24B
Are arranged so as to sandwich the pair of blades 21A and 21B from above and below in the figure, and thereby each blade 21
A and 21B are regulated so that only movements that change the respective intervals are performed.

The blade guides 23A and 23B are arranged such that the end portions of the blades 21A and 21B are sandwiched between the guides 23a and 23b, respectively, in the lateral direction in the drawing.
And 23c and 23d are provided.

Guides 23a, 23b and guides 23c, 2
3d has a V shape, and 23b and 23c are common.

The blade guides 23A and 23B thus constructed can be moved in the vertical direction (direction of arrow B) in the figure by the blade guide drive mechanism 26. The blade guide drive mechanism 2
6 is driven by the input from the image processing device 5.

From this fact, each blade 21A, 21B
Keeps the parallel state, and keeps the separation distance steplessly. That is, it is possible to set an arbitrary distance.

According to the X-ray CT apparatus thus constructed, the slice thickness corresponding to the distance between the blades 21A and 21B can be arbitrarily set.

Therefore, in the normal scan method, a desired slice thickness can be freely set in relation to the number of movements of the table on which the subject is placed.

Therefore, it becomes possible to optimize the desired sharpness of the tomographic image in consideration of the exposure dose of the subject.

In the volume scan system,
Since the effective slice thickness can be obtained by using the moving speed of the table on which the subject is placed and the slice thickness that can be set to a free value as parameters, the effective slice thickness required even when the moving speed of the table is restricted. It becomes possible to obtain a thick tomographic image.

[0041]

As is apparent from the above description,
According to the X-ray CT apparatus of the present invention, the collimator can obtain a predetermined slice thickness.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a main part of an X-ray CT apparatus according to the present invention.

FIG. 2 is an overall schematic diagram showing an embodiment of an X-ray CT apparatus according to the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

 14 Collimator 21 Blade 23 Blade Guide 26 Blade Guide Drive Mechanism

Claims (1)

[Claims] 1. An X including an X-ray tube and an X-ray detector which rotate around an imaginary axis as opposed to each other around the imaginary axis, and a collimator arranged at an X-ray irradiation port of the X-ray tube. In the X-ray CT apparatus, means for continuously changing the axial width of the X-ray passage opening of the collimator is provided.
X-ray CT equipment.