JPS58216973A - Radiation detector block - Google Patents

Abstract

PURPOSE:To accerelate a responsive speed, by a method wherein the photo-receiving surface of each photo-receiving element is made smaller than the radiation incident surface of each scintillator and the photo-output surface of each scintillator element is formed into the same shape as the photo-receiving surface of the photo-receiving element. CONSTITUTION:Each photo-receiving elements 13 are arranged on an insulator 12 unidimensionally at a same pitch in the longitudinal direction thereof. The photo-receiving surface of each element 13 is formed so as to be made smaller than the area of the X-ray incident surface of a scintillator 10. The element 10 has a rectangular parallelepiped of which the width of the short side direction in the X-ray incident surface is formed so as to be made smaller than the width in the longitudinal direction and an inverted quadrangular pyramid 10B of which the shape of the photo-output surface is same to the photo-receiving surface of the element 13. An X-ray detecting block is constituted in such a manner that the photo-receiving surface of the element 13 and the photo-output surface of the element 10 are arranged so as to be made same to the arranging pitch of the element 13. When X-rays enter the element 10, fluorescent light is emitted to be guided to the photo-receiving surface of the element 13 and converted to an electric signal by the actions of the element 13 and the insulator 12 to be outputted to a terminal 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention belongs to the technical field of radiation detectors having scintillator elements and multichannel photodiodes.

[Technical background of the invention and its problems]

Radiation tomography apparatuses, such as third-generation or fourth-generation X-ray CT apparatuses, have an X-ray detector in which a plurality of detection elements are arranged one-dimensionally at high density. In recent years, solid-state scintillation detectors that combine scintillators and photodiodes have come into widespread use as X-ray detectors, instead of gas ionization chambers that have conventionally been the mainstream. This is because the photodiodes used in solid-state scintillation detectors can be mounted in high density, so high resolution C
This is because it can meet the requirement that the arrangement pitch of the detection elements must be made as small as possible in order to obtain both T and T images. An X-ray detector, which is a solid-state scintillation detector, is constructed by one-dimensionally arranging X-ray detector blocks as shown in FIG.

As shown in FIG. 1, the X-ray detector block 1 includes a plurality of light receiving elements 3.4-3 on an insulator, for example, a ceramic layer 2.
A multi-channel photodiode 6 formed by forming E so as to be arranged in the − dimension, and scintillation elements 5A-5E bonded to the light receiving elements 6A-6E with a transparent adhesive 4, for example, a glass adhesive. Equipped with. Each scintillator element 5A to 5E is a rectangular parallelepiped, and the light receiving element 6A
Each surface except the surface to be bonded to 3E is coated with a light reflecting material 6 to prevent crosstalk. The light receiving surfaces of the light receiving elements 3A-3H are the scintillator elements 5A to 3H.
It has the same shape as the light output surface (bottom surface) of scintillator elements 5E, and can efficiently receive light emitted from scintillator elements 5A to 5E.

By the way, X-ray detectors used in X-ray CT devices have characteristics such as high radiation absorption efficiency, fast response speed, and good SIN ratio for detecting minute currents. It is necessary that the

However, in the X-ray detector block 1 having the above configuration, even if the arrangement pitch of the scintillator elements is made small, Johnson i sound occurs when used with a photodiode bias of 0. Furthermore, the response speed is limited by the light-receiving area of the light-receiving element.

Therefore, in a radiation detector block in which the radiation incidence surface of the scintillator element is made small in order to obtain a predetermined spatial resolution, and the arrangement pitch of each scintillator element is made small, how can we eliminate Johnson noise and further improve the SiW ratio? The problem is how to increase the speed of response and further increase the response speed.

[Purpose of the invention]

This invention was made in view of the above circumstances, and
The purpose of this invention is to provide a radiation detector block that improves the s ratio and has a fast response speed.

[Summary of the invention]

The outline of the present invention for achieving the above object is that each scintillator element is arranged such that its radiation entrance surfaces have the same shape and the same pitch, and that the radiation entrance surfaces have the same shape in the longitudinal direction on the insulator. In a radiation detector block formed by bonding light-receiving elements arranged one-dimensionally at a pitch, the light-receiving surface of each light-receiving element is smaller than the radiation incidence surface of each scintillator element, and each scintillator It is characterized in that the light output surface of the element has the same shape as the light receiving surface of the light receiving element.

[Embodiments of the invention]

FIG. 2 is an exploded perspective view showing one embodiment of the invention, and FIG. 6 is a schematic perspective view showing a scintillator element in one embodiment of the invention.

As shown in FIG. 2, a radiation detector block, such as an X-ray detector block, which is an embodiment of the present invention, includes at least a large number of scintillator elements 10 and multichannel photodiodes 11, each having the same shape.

In the multi-channel photodiode 11, a large number of light-receiving elements 16 are formed on an insulator 12 formed into a rectangular plate shape by, for example, vapor deposition, with a constant array pitch in the longitudinal direction of the insulator 12.

Note that 14 is a terminal for taking out an electric signal, and is formed by pressing one end of the light-receiving element 16 onto the insulator 12 so as to extend. The light receiving surface of the light receiving element 16 is
It is formed smaller than the area of the X-ray incident surface of the scintillator element 10, which will be described later.

This is to reduce Johnson noise and increase response speed by reducing the light receiving area.

As shown in FIG. 3, the scintillator element 10 has a rectangular parallelepiped portion 10A in which the width in the transverse direction on the X-ray incident surface is much smaller than the width in the longitudinal direction, and the shape of the light output surface is the same as that of the light receiving element 16. It is an integrated scintillator crystal formed to have an inverted quadrangular truncated pyramid part 10B which is the same as the light receiving surface of the crystal, and coated with a light reflecting material (not shown) on each surface except for the light output surface. .

Then, in the sXm detector block, the light-receiving surface of each light-receiving element 16 on the insulator 12 and the light output surface of each scintillator element '10 are bonded using transparent adhesive so that the arrangement pitch of the scintillator elements 10 is the same. It is made up of adhesive.

Note that the arrangement pitch of the light receiving elements 13 is determined by the arrangement pitch of the scintillator elements 10.

By arranging a large number of X-ray detector blocks having the above configuration in the longitudinal direction, an X-ray detector in an X@CT apparatus can be constructed.

In the X-ray detector block having the above configuration, X-rays are transmitted to the scintillator element 10 from the X-ray incident surface of the scintillator element 10.
When the light enters the scintillator element 10, the scintillator element 10 emits fluorescence,
The fluorescence is transmitted to the scintillator element 10 one after another by the original reflecting material.
The fluorescent light is reflected by the light receiving element 16, and the fluorescent light is emitted from the light output surface.
Fluorescence is guided to the light-receiving surface of the Light receiving element 13 and insulator 1
2, the input fluorescence is converted into an electrical signal, and the electrical signal can be taken out from the terminal 14. In that case, the light receiving surface of the light receiving element 16 is
Since it is formed smaller than the area of the line incidence surface, Johnson noise due to parallel resistance can be reduced when considered in an equivalent circuit (shot noise due to dark current can be reduced by using a photodiode with OV bias). ), therefore the Sl of the bXM detector
Not only can the N ratio be improved, but also the response speed can be increased.

Although one embodiment of this invention has been described in detail above, this invention is not limited to the above embodiment, and it goes without saying that it can be implemented with appropriate modifications within the scope of the gist of this invention. Nor.

In the present invention, in short, the scintillator element only needs to be formed so that the light receiving surface of the light receiving element and the light output surface of the scintillator element are reduced in area to have the same shape force surface. Therefore, instead of the scintillator element having the shape as in the previous embodiment, a scintillator element having the shape as shown in FIGS. 4 and 5 may be used as another embodiment. The scintillator element 10 shown in FIG. 4 has a rectangular parallelepiped portion 1 whose width in the width direction on the X-ray incident surface is much smaller than the width in the length direction.
0. (and an inverted pentahedral portion 10C in which the width in the longitudinal direction is intermittently reduced without changing the width in the transverse direction. Also, FIG. The scintillator element 10 shown in FIG.
It is formed to have a D. In each of the scintillator elements 10 shown in FIGS. 4 and 5, the area of the light output surface is smaller than that of the X-ray incident surface. By making the shape the same as the light output surface, the area of the light receiving surface of the light receiving element 16 can be reduced.
It is possible to improve the X-W ratio and increase the response speed of the X-ray detector.

〔Effect of the invention〕

According to the present invention, it is possible to provide a radiation detector block with a better SiW ratio and faster response speed than a radiation detector block in which the radiation incident surface of a scintillator element and the light receiving surface of a light receiving element have the same area. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a conventional radiation detector block, FIG. 2 is an exploded perspective view showing an embodiment of the present invention, and FIG.
The figure is a schematic perspective view showing the scintillator element in the above embodiment, and Figures i4 and 5 are schematic perspective views showing the scintillator element in other embodiments. 10...Scintillator element, 10A...Rectangular parallelepiped part,
10B... Inverted square pyramid part, 10C... Inverted pentahedron part, 10D... Inverted conical truncated part, 11... Multi-channel photodiode, 12... Insulator, 16
···Light receiving element.

Claims (4)

[Claims] (1) Each scintillator element is arranged so that each radiation entrance surface has the same shape and the same pitch, and each scintillator element is arranged one-dimensionally at the same pitch in the longitudinal direction on the insulator. In a radiation detector block formed by joining the formed light receiving elements, the light receiving surface of each light receiving element is smaller than the radiation incidence surface of each scintillator element, and the light output surface of each scintillator element is smaller than the light receiving surface of the light receiving element. A radiation detector block characterized by having the same shape as a surface. (2) The scintillator element is characterized in that the cross-sectional shape perpendicular to the radiation traveling direction has a shape whose area decreases from the radiation input surface shape to the light output surface shape. radiation detector block. (3) The radiation detector block according to claim 2, wherein the scintillator element has a shape having an inverted truncated pyramid. (4) The radiation detector block according to claim 2, wherein the scintillator element has a shape having an inverted truncated cone.