JPS6247568A - Radial rays detector - Google Patents

Abstract

PURPOSE:To improve sensitivity, S/N and low contrast resolving power as a detector even in case an element with inferior light transmissivity is used by providing a optical wave guide path on the surface of the incident side of radial rays of a scintillator element and conducting the rays of light generating in the element to an optical semiconductor element with good efficiency. CONSTITUTION:A medium of the optical wave guide path, for instance, quartz glass 11 is joined with the surface of the incident side of the radial rays of the scintillator element 10. Then, the optical semiconductor element 12 is joined with the surface which is not exposed to the radial rays of the medium 11 using an optically transparent adhesive. Further, as to the joining of the element 10 with the medium 11, it is desirable to form each material powder in a body by a hot isostatic process. Further, a circuit which transmits an electrical signal to a signal processing system of a next step is formed by holding the element 12 by a substrate 13 and the aluminum foil 14 prevents the rays of light generating in the scintillator leaking out to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation detector, and particularly to a radiation detector used in a computed tomography apparatus.

[Technical Background of the Invention] A radiation UI layer imaging device, for example, a third-generation or fourth-generation X-ray CT device, has an X-ray detector in which a plurality of detection elements are arranged in one dimension at high density. .

In recent years, solid-state scintillation detectors that combine a scintillator and a photodiode have been widely used as X-ray detectors, instead of gas ionization chambers that have traditionally been the mainstream. This meets the requirement that the arrangement pitch of the detection elements must be made as small as possible in order to obtain high-resolution CT images, since the photodiodes used in solid-state scintillation detectors can be mounted in high density. This is because it is possible. The structure of a conventionally known scintillation detector is shown below. FIG. 4 shows a multi-channel scintillator element body 3 formed by sequentially bonding a plurality of scintillator elements 1 via a collimator plate 2. As shown in FIG. The collimator plate 2 is usually a thin plate of a heavy metal with a high X-ray absorption rate, such as lead or tungsten, and both sides of the plate are coated with a light reflecting agent to efficiently reflect the light generated by the scintillator element 1.

FIG. 5 shows a multichannel photodiode 4, in which a plurality of photodiode elements 6, which are semiconductor photodetecting elements, are formed on one semiconductor substrate 5. Each photodiode element 6 is provided with a terminal 7 for signal extraction, and this terminal 7 is electrically connected to a printed wiring terminal on an insulating substrate 8 by wire bonding or the like (not shown).

As shown in FIG. 6, the multi-channel photodiode 4 having such a configuration is adhesively bonded to the multi-channel radiation detection block 9 using a transparent adhesive, such as a glass adhesive, so that each channel coincides with the other. can be obtained.

By the way, in the radiation detector having the above configuration, the characteristics required of the scintillator element include the following.

■ High X-ray absorption rate.

■High efficiency in converting absorbed X-rays into light.

■ High light transmittance.

(Left below) ■The amount of light emitted must not change due to temperature changes. (The temperature coefficient of luminous efficiency should be small.) ■ There should be little afterglow and fast decay.

■ The emission spectrum must match the sensitivity wavelength range of the optical semiconductor device.

Gd2 is a scintillator material that satisfies these characteristics.
O2S: There is a pr phosphor. In particular, this phosphor has a very small temperature coefficient of luminous efficiency, and when used as a scintillator in the detector of a radiation tomography device,
Non-uniform changes in signal amount between channels due to changes in ambient temperature are eliminated, and it is expected that a good image will be obtained.

However, single crystal growth technology for this material is difficult, and good single crystals have not yet been obtained.
A method of sintering using the ingM method (hereinafter abbreviated as HIP method) has been attempted. Gd2O made using this method
2S: Pr scintillator has poor light transmittance.

The reason is: ■The material absorbs light. ■Voids exist in the sintered body and light is scattered. ■Coloring due to impurity contamination.

If a detector made using a scintillator with poor light transmittance is used in an X-ray CT apparatus, the sensitivity and S/N of the detector will decrease. In addition, low energy components of incident X-rays are reduced in the detected signal, and when converted into an image, low contrast 1 to last resolution becomes poor.

Therefore, when using a scintillator element with poor light transmittance, it is necessary to have a structure that effectively guides the light generated within the scintillator element to the optical semiconductor element.
S: If the above structure can be applied to a scintillator made by sintering Pr using the HIP method, the best detector for X-ray CT can be obtained.

[Object of the Invention] An object of the present invention is to improve the performance as a detector by creating a structure that effectively guides light generated within a scintillator element with poor light transmittance to an optical semiconductor element.

[Summary of the Invention] The radiation detector of the present invention includes an optical waveguide provided on the radiation incident side surface of the scintillator element, and efficiently guides the light generated within the scintillator element to the optical semiconductor element, thereby improving the light transmittance. Sensitivity as a detector even when using poor scintillator elements.

It is characterized by making it possible to improve resolution to S/N and low contrast of 1.

[Embodiment of the Invention] FIG. 1 is a cross-sectional view of the structure of an embodiment of the radiation detector of the present invention.

An optical waveguide medium such as quartz glass 11 is bonded to the surface of the scintillator element 10 on the radiation incident side.

The optical semiconductor element 12 is bonded to the surface of the medium 11 that is not exposed to radiation using an optically transparent adhesive.

Although an optically transparent adhesive may be used to join the scintillator element 10 and the optical waveguide medium 11, it is preferable that the respective raw material powders be integrally formed by hot isostatic pressing.

The light reflective layer of the optical waveguide is made of titanium dioxide (Ti 02 ).
It is formed by applying a white paint containing as a main component to all surfaces except the bonding surface with the scintillator and the bonding surface with the optical semiconductor, but these are not shown.

Reference numeral 13 denotes a substrate that holds the optical semiconductor element and forms a circuit for passing electrical signals to the next stage signal processing system.

14 is further covered with aluminum foil or the like in order to prevent the light generated within the scintillator from leaking outside.

When the medium 11 is air, light reflection! ) Only one layer is formed of a metal foil plate of a light element (for example aluminum) coated with white paint.

FIG. 2 is a further improvement of FIG.
Among the light generated in the same direction within the scintillator element 10, the light guided in the direction of radiation transmission of the scintillator element is detected.

FIG. 6 shows the scintillator element 10. Optical waveguide medium 11
．． A structure in which optical semiconductor elements 12 are closely arranged in multiple channels is shown. Reference numeral 16 denotes a radiation collimator plate, which is mainly a thin lead plate coated with white paint and provided with a light reflective layer.

[Effect of the invention] The light generated within the scintillator element can be effectively guided to the optical semiconductor element, and Gd2O2S :Pr (
A scintillator made from phosphor powder (gadolinium oxide) using the hot isostatic pressing method can compensate for the deterioration of characteristics due to the poor light transmittance, which is the only drawback, and has a high sensitivity as a detector. , S/N, and low contrast resolution improvements can be achieved.

In addition, (1) the light-receiving area of the optical semiconductor element can be reduced;

(2) Since the incident radiation does not directly reach the optical semiconductor element, S/N deterioration due to this can be prevented.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing one embodiment of a detector according to the present invention, and FIG. 3 is a configuration diagram of a scintillator element, an optical semiconductor element, and an optical waveguide medium arranged in close contact with each other in multichannels, FIG. 4 is a perspective view showing a conventional multi-channel scintillator element body, FIG. 5 is a perspective view showing a conventional multi-channel photodiode element body, and FIG. 6 is the element body shown in FIGS. 4 and 5. FIG. 10...Scintillator element 11...Optical waveguide medium 12...Optical semiconductor element 13...Substrate 14...Aluminum foil 15...Optical semiconductor element 16...Collimator plate

Claims (5)

[Claims] (1) In a radiation detector that combines a scintillator element that can emit light with radiation and a semiconductor element that converts the light from this scintillator element into an electrical signal, an optical waveguide is provided on the surface of the scintillator element on the radiation incident side. A radiation detector characterized in that an optical semiconductor element is bonded to a side surface of the optical waveguide that is not affected by radiation. (2) The optical waveguide uses quartz glass as a medium, and coats all sides except the surface where the optical semiconductor element is bonded and the surface where the scintillator element is bonded with a white paint containing titanium dioxide (TiO2) as the main component, 2. The radiation detector according to claim 1, further comprising a light reflecting layer. (3) The optical waveguide uses air as a medium, and all sides except the surface where the optical semiconductor element is bonded and the surface where the scintillator element is bonded are made of aluminum coated with a white paint containing titanium dioxide (TiO2) as the main component. 2. The radiation detector according to claim 1, wherein the light reflecting layer is formed of a thin metal plate of a light element such as. (4) The radiation detector according to claim 1, characterized in that an optical semiconductor element is bonded to the surface of the scintillator element in the radiation transmission direction. (5) The radiation detector according to claim 1, characterized in that the scintillator element is made from Gd2O2S:Pr (gadolinium sulfate) powder raw material by hot isostatic pressing.