JPH0426415A - X-ray ct device - Google Patents

Abstract

PURPOSE:To obtain the X-ray CT device which does not require the mechanical operation to retreat a detector and allows high-speed scanning of an X-ray focus by providing a ring type arrangement of the radiation detector fixed in proximity to the end on the side facing another ring on one side of two X-ray shieldable rings. CONSTITUTION:The X-ray generated from the X-ray focus of an X-ray generator first passes a spacing between the two X-ray shieldable rings 41, 42 on the side near the X-ray focus, then arrives at the inner side of the X-ray shieldable ring positioned on the side opposite form the X-ray focus. The X-ray detector 5 is disposed on the inner side of the ring 42 when the X-ray first passes the spacing between the two rings and, therefore, the X-ray is not made incident on this X-ray detector. The X-ray detector is disposed on the inner side of the X-ray shieldable ring positioned on the side opposite from the X-ray focus and, therefore, the X-ray is eventually made incident on this X-ray detector when the X-ray arrives at the inner side of this rig. The data is evidently collected by making the X-ray incident on the detector so as to turn around the X-ray focus even if the operation to retreat the detector therefrom is not made.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a so-called fourth generation XmCT device.

[Conventional technology]

The 4th generation X1iCT device has a large number of radiation detectors arranged in a ring shape so that the XIi focal point rotates around the subject at high speed and makes one revolution on a concentric circle inside the circumference. Since the radiation detector group does not rotate, data can be collected very quickly. In this fourth generation Xl1CT device, the X-rays emitted from the X-ray focus must pass through the subject and enter the detector on the opposite side, so the detector on the xm focus side Xl! In order not to interfere with the irradiation, the detector on the Xli focus side is moved away from the
Nutrition'”).

[Problem to be solved by the invention]

However, such a detector retraction operation ("Nut
cation") is a mechanical operation, so there is a limit even if it can be moved at high speed, which is a factor that hinders high-speed scanning of the X-ray focus. This invention has the problem that the detector X-ray CT that enables high-speed scanning of the X-ray focus without the need for mechanical evacuation
The purpose is to provide equipment.

[Means to solve the problem]

In order to achieve the above object, the X-ray CT apparatus according to the present invention includes an X-ray generator whose X-ray focus moves on the circumference around the subject, and a a collimator consisting of two X-ray shielding rings that form a gap in the body axis direction of the subject; and a drive that moves the two X-ray shielding rings in the body axis direction of the subject to change the gap between them. A ring-shaped array of radiation detectors is provided, which is fixed inside one of the two X-ray shielding rings, close to the end opposite the other ring.

[For production]

The X-rays emitted from the Xll focal point of the X-ray generator first pass through the gap between the two X-ray shielding rings on the side closer to the X-ray focal point, and then pass through the gap between the two X-ray shielding rings on the side opposite to the X-ray focal point. do X
Reach inside the line-shielding ring. Here, when the X-ray first passes through the gap between the two rings, the X-ray detector force (located inside the ring) prevents the X-ray from entering the X-ray detector. No. Next, when the Xml reaches the inside of the X-ray shielding ring located on the opposite side from the X-ray focal point, an X-ray detector is placed there, so the X-rays enter the detector. From now on, you can move the X-ray focus to 1 without retracting the detector.
It can be seen that data can be collected by rotating X-rays and making them enter the detector.The X-ray beam that contributes to data collection is the X-ray beam that enters the detector.
It depends on the spacing between the two rings mentioned above and the end position of the detector. The end position of the detector located on the inner surface of one ring is brought close to the end of that ring opposite the other ring. Therefore, the inclination angle of the X-ray beam with respect to the direction perpendicular to the subject's body axis can be minimized, and artifacts in the reconstructed image can be reduced.

[Embodiment] Hereinafter, five embodiments of the present invention will be described in detail with reference to the drawings. In Figure 1, subject 1 is placed on gantry 2.
It is inserted into the central tunnel section of. Inside this gantry 2, an X-ray tube 3, a collimator 4, and a detector 5 are arranged. The X-ray tube 3 may be one that is held in a rotating frame or the like and rotates at high speed, but it is better to use one that is formed in a ring shape as a whole and only the X-ray focal point rotates at high speed. Desirable for fast scanning. The collimator 4 has two XI!s surrounding the subject 1! Consisting of shielding rings 41 and 42, each of which is moved in the body axis direction of the subject 1 by a drive device 43 and 44 so that the radiation from the X-ray tube 3 can be focused by moving toward or away from each other. It has become. The X-ray shielding ring 41 has a flat cross section,
The X-ray shielding rings 42 have an L-shaped cross section and are each made of a highly X-ray attenuating material such as a bell. A detection element 51 is located inside this L-shaped X-ray shielding ring 42.
A radiation detector 5 consisting of an auxiliary circuit 52 and an attached circuit 52 is fixed. A large number of pressure detectors 5 are arranged in a ring shape along the circumferential direction of the X-ray shielding ring 42. The detection element 51 is the second
As shown in the figure, the upright part of the X-ray shielding ring 42 (the subject
(the part that stands perpendicular to the body axis). Since this detector 5 is fixed to the L-shaped X-ray shielding ring 42, when the shielding ring 42 is moved in the body axis direction as described above, it will move in the body axis direction accordingly. The ring-shaped arrangement of the X-ray tube 3, collimator 4, and detector 5 is arranged on a concentric circle with the body axis of the subject 1 as the center axis. The focal orbit of the X-ray tube 3 is located on the outermost concentric circle, and the circles formed by the ring-shaped arrangement of the collimator 4 and the detector 5 are circles of approximately the same size, and the focal orbit of the X-ray tube 3 is located on the innermost concentric circle. These concentric circles are called concentric circles, and these concentric circles are perpendicular to the body axis of the subject 1. The detector 5 is an X-ray shielding ring 42
As shown in Figures 1 and 2, the X-rays emitted from the Xll focal point are
Although the X-ray shielding ring 42 of the collimator 4 prevents the radiation from entering the detection element 51, the radiation enters the detection element 51 on the opposite side of the subject 1. In that case, X on the focal side
Since the X-rays passing through the gap between the radiation shielding rings 41 and 42 will be incident on the detection element 51 on the opposite side, the interval between the X-ray shielding rings 41 and 42 will determine the slice thickness. This will be explained in more detail. First, as shown in Figure 3,
The position of the line focus is F, the end position of the X-ray shielding ring 41 on the X-ray focus side is Pl, the end position of the opposite side is Ql, the end position of the X11A shielding ring 42 on the X-ray focal side is P2, the opposite side Let the end position be Q2. At this time, not all of the X-rays generated from the focal point F and passing between the X-ray shielding rings 41 and 42 enter the detection element 51 on the opposite side, and only the X-rays to the right of the point Q2 on the opposite side are detected. It does not enter the element 51. In other words, the slice thickness on the central axis (body axis of subject 1) is
This corresponds to the distance between point 01, where the line connecting point F and point Q2 intersects with the central axis, and point 02, where the line connecting point F and point P2 intersects with the central axis. At this time, the position of the X-ray shielding ring 41 is determined as point P1 on the line connecting point F and point Q2. By moving the xsi shielding rings 41, 42 in the axial direction, this 01-02 distance can be changed to increase the slice thickness to, for example, 2-1.
51111.10m+a, etc. When using various slice thicknesses in this way, the X-ray beam incident on the detection element 51 is not perpendicular to the central axis but is slightly inclined, regardless of the slice thickness. The tilt angle is kept to a minimum. In other words, since the detection element 51 is brought into close contact with the ends (Ql, Ql) of the upright part of the X-ray shielding ring 42 forming the collimator 4, the FQ of the X-ray beam incident on the detection element 51 is
The two lines can be arranged so that the angle of inclination from the direction perpendicular to the central axis is the minimum. By shifting the detector 5 in the direction of the body axis from the trajectory of the X-ray focal point and tilting the X-ray beam somewhat from the direction perpendicular to the body axis, the detector 5 can be moved without having to be mechanically retracted. , data can be obtained by rotating the X-ray focal point once. If the X-ray beam is not perpendicular to the body axis but tilted from it, artifacts will occur in the reconstructed image when the data obtained in that state is processed to reconstruct the image. Since the positional relationship that minimizes the inclination angle can be realized, artifacts can be minimized. [Effects of the Invention] According to the X-ray CT apparatus of the present invention, the mechanical operation of retracting the detector is not required, so that high-speed scanning of the X-ray focal point is possible. Furthermore, since the positional relationship is such that the inclination angle of the X-ray beam from the direction perpendicular to the body axis is minimized, artifacts in the reconstructed image can be minimized.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the vicinity of the collimator and detection element in FIG. 1,
FIG. 3 is a schematic diagram for explaining slice thickness. 1... Subject, 2... Gantry, 3... X-ray tube,
4... Collimator, 41.42... X-ray shielding ring, 43.44... Drive device, 5... Radiation detector,
51...detection element, 52...attached circuit.

Claims (1)

[Claims] (1) An X-ray generator whose X-ray focus moves on the circumference around the subject, and two X-ray shields that form a gap in the body axis direction of the subject inside the X-ray focus trajectory. a collimator consisting of a magnetic ring; a drive device that moves the two X-ray shielding rings in the axial direction of the subject's body to change the interval between the gaps; and an inner side of one of the two X-ray shielding rings. To,
An X-ray CT apparatus comprising a ring-shaped array of radiation detectors fixed close to the end of the side opposite the other ring.