JPS6252423B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an X-ray detector used in an X-ray tomography apparatus, and more specifically, to an X-ray detector that detects the intensity of X-rays transmitted through a subject and simultaneously The present invention relates to an X-ray detector configured to also detect the intensity of X-rays that have passed through the outside.

(Prior Art) FIG. 1 is a block diagram showing an example of a conventional X-ray detector of this type. In the figure, 1 is a subject, S is an X-ray source, and 3 is an X-ray detector. The X-ray detector 3 has a large number of anode plates 5 and cathode plates 6 arranged substantially parallel to the direction of incident X-rays 11 in a sealed case 4, and has a high-pressure gas (e.g. It is filled with xenon gas) 8. The incident X-rays pass through the X-ray entrance window 7 on the front surface of the case 4, enter the electrode compartment made up of the anode plate 5 and the cathode plate 6, and ionize the gas 8. A high voltage is applied to the electrode plates (anode plate and cathode plate), and ionized charges are captured by the anode plate. The amount of ionized charge corresponds to the X-ray energy at that time, and the current obtained from the anode plate corresponds to this energy, so it became possible to detect the incident X-ray energy by detecting this current. There is.

In this case, the X-ray detector includes an electrode compartment so-called normal channel part 9 for detecting the X-rays that have passed through the subject 1, and a so-called normal channel part 9 for detecting the X-rays that have passed through the outside of the subject (original A reference channel section 10 usually arranged outside the channel section for detection.
It is made up of. Reflection channel section 10
The X-ray detection at is the detection end for controlling the intensity of the X-ray source S.

By the way, when the subject 1 is large (as shown in the figure), the scattered radiation 12 from the subject 1 enters the reference channel section 10, which causes an error in measuring the output intensity of the X-ray source S. Normal channel section 9
The disadvantage was that it was also affected by inter-channel interference.

(Object of the Invention) The present invention was made in view of such problems, and its purpose is to prevent scattered radiation from entering the reference channel section and to prevent interference from the normal channel section. An object of the present invention is to provide a scattered radiation-protected X-ray detector for CT.

(Structure of the Invention) The present invention that achieves the above object includes a sealed case filled with an X-ray detection gas, a plurality of planar anode plates and a plurality of planar cathodes provided within the case. These plates constitute a number of detection chambers spatially partitioned by an anode plate and a cathode plate, and the central part transmits the object and enters through the X-ray entrance window at the front end of the case. An X for CT comprising a normal channel part for detecting X-rays, and a reference channel part for detecting straight X-rays passing outside the subject on the outside of the normal channel part.
In the ray detector, the front surface of the X-ray entrance window on the boundary line between the normal channel part and the reference channel part is made of a material that blocks X-rays and prevents scattered rays from the subject from entering the reference channel part. This is characterized in that an X-ray shielding plate is attached that extends in the direction of the X-ray source to the extent that the X-rays can be prevented.

(Embodiment) FIG. 2 is a configuration diagram showing an embodiment of the present invention, and the difference between this embodiment and the conventional example shown in FIG.
A scattered radiation shielding plate 21 is attached to the front surface of the radiation entrance window 7 and on the boundary between the normal channel section 9 and the reference channel section 10. The shielding plate 21 is
It is an X-ray shielding plate made of a material that does not transmit X-rays or has a large X-ray absorption, and its cross section is triangular pyramid-shaped, and the base of the triangular pyramid is joined to the front surface of the entrance window 7.
The height of the triangular pyramid is such that the scattered radiation 12 from the subject 1 does not extend beyond the tip of the pyramid and enter the reference channel section 10. The depth of the shielding plate 21 (the length in the direction perpendicular to the plane of the paper in FIG. 2) is at least the same as the width of the X-ray entrance window 7 (the width in the direction perpendicular to the plane of the paper).

By attaching such an X-ray shielding plate 21 to the front surface of the entrance window 7, the scattered rays 12 from the subject 1 are prevented from entering the reference channel section 10 as shown in the figure.
Only straight X-rays from the X-ray source S will be incident on the. Furthermore, since the width of the base of the shielding plate 21 is significantly wider than the electrode spacing, the normal channel section 9 and the reference channel section 10 are completely separated in the ionized charge movement region. Therefore, mutual interference is eliminated.

The shape of the shielding plate is not limited to a triangular pyramid cross section, but may be a trapezoid as shown in FIG. 3A, or a shape with curved side surfaces as shown in FIG. 3B.

(Effects of the Invention) As explained above, in the present invention, the X
The structure has an X-ray shielding plate attached to the front of the radiation entrance window, which prevents scattered radiation from the subject from entering the reference channel and mutual interference with the normal X-ray source. , the straight intensity from the X-ray source can be detected with high accuracy in the reference channel section.

Note that the same effect can be obtained even if the reference channel portion is provided only on one side.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional X-ray detector, Fig. 2 is a block diagram showing an embodiment of the X-ray detector according to the present invention, and Fig. 3 is a block diagram showing another embodiment of the shielding plate. FIG. S... X-ray source, 1... Subject, 4... Case, 5... Anode plate, 6... Cathode plate, 7... X-ray entrance window, 9
...Normal channel part, 10...Reference channel part, 11...X-ray, 12...Scattered ray, 21...X-ray shielding plate.

Claims (1)

[Claims] 1 A sealed case filled with X-ray detection gas, a plurality of planar anode plates and a plurality of planar cathode plates provided within the case, and a space is defined by the anode plates and the cathode plates. The central part is a normal channel part that detects the X-rays that have passed through the subject and entered the X-ray entrance window at the front end of the case. In a CT X-ray detector that is provided with a reference channel section on the outside for detecting straight X-rays passing through the outside of the object, the front surface of the X-ray entrance window is located on the boundary line between the normal channel section and the reference channel section. Scattered radiation characterized in that an X-ray shielding plate made of a substance that shields X-rays and extending in the direction of the X-ray source is attached to an extent that can prevent scattered radiation from the subject from entering the reference channel section. Protective CT X-ray detector.