JPH1184013A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector excellent in both radiation absorbing efficiency and luminous efficiency. SOLUTION: A fluorescent element is constituted as a double-layer structure wherein fluorescent elements 1 excellent in luminous efficiency are formed on the radiation incidence side, and fluorescent elements 2 excellent in transparency and radiation absorbing efficiency are formed under the elements 1. A photodiode array substrate 3 is formed under the elements 2. The fluorescent elements 1 and the fluorescent elements 2 are arranged in an array type, and shielding material 4 is inserted between the neighboring elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector used in a radiographic apparatus and the like.

[0002]

2. Description of the Related Art For example, in an X-ray tomography apparatus, an X-ray tube which rotates around a subject around a body axis of the subject, and a detector which detects X-rays transmitted through the subject are provided. At least, the X-ray tube is rotated at a predetermined angle around the body axis of the subject, and the X-ray tube is irradiated with the X-rays to the subject, and output from the detector that detects the X-rays transmitted through the subject. Image reconstruction processing is performed based on such data to obtain a tomographic image.

[0003] In this type of apparatus, high quality images are required in order to enable accurate medical judgment. For this purpose, it is important to improve the performance of the detector.

Conventionally, a radiation detector is configured as shown in FIG. A radiation detector comprising a scintillator 41 and a plurality of radiation detectors including photoelectric conversion elements 43 such as photodiodes bonded to the lower surface of the scintillator 41 via an adhesive 42 having a high light transmittance via a shielding plate 45 is arranged. Forming an array.

When the radiation enters the upper surface of the scintillator 41, the radiation is converted into light in the scintillator 41,
The emitted light is detected by the photoelectric conversion element 43 and converted into an electric signal, and a signal proportional to the incident radiation dose is extracted.

As such a scintillator, Gd ₂
A ceramic scintillator containing O ₂ S as a main component or a CdWO ₄ single crystal scintillator is used.

[0007]

However, Gd ₂ O ₂ S
The main component of the ceramic scintillator is CdWO ₄
The luminous efficiency by radiation is higher than that of the single crystal scintillator, and the luminous intensity of the CdWO ₄ single crystal scintillator is 2-3.
Although it is doubled, since the inside of the scintillator is opaque,
If the thickness is increased, the light emitted in the scintillator cannot reach the photoelectric conversion element, so that the thickness cannot be increased too much, and the radiation absorption efficiency becomes about 90%. Could not be converted to light.

On the other hand, CdWO ₄ single crystal scintillator
Since it is excellent in transparency, its thickness can be increased to make the radiation absorption efficiency 100%, and the conversion efficiency to light is excellent, but the luminous efficiency is Gd ₂ O ₂ S. There is a problem that it is about 1/2 to 1/3 of the ceramic scintillator as the main component.

The present invention has been made to solve the above problems, and provides a radiation detector having both good radiation absorption efficiency and luminous efficiency.

[0010]

In order to achieve the above object, a radiation detector according to the present invention comprises a phosphor element emitting light by radiation and a photoelectric conversion element detecting fluorescence by the phosphor element. In the radiation detector, the phosphor element is a phosphor element having good luminous efficiency on the radiation incident side,
On the lower side, it has a two-layer structure of a phosphor element having good transparency and good radiation absorption efficiency.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a radiation detector according to the present invention.

1 is a fluorescent element having good radiation emission efficiency such as a ceramic scintillator containing Gd ₂ O ₂ S as a main component, and 2 is a fluorescent substance having high transparency and good radiation absorption efficiency such as a CdWO ₄ single crystal scintillator. The body element 3 is a photodiode array substrate as a photoelectric conversion element that converts light from the phosphor element into an electric signal, and 4 is a shielding member for preventing crosstalk between channels.

A phosphor element 1 is arranged on the radiation incident side,
For example, the thickness is formed to be 1 to 1.5 mm. Under the phosphor element 1, the phosphor element 2 is thicker than the phosphor element 1 via an optical adhesive, for example, 2 to 2.5 mm.
Further, a photodiode array substrate 3 is formed below the phosphor element 2.

Here, an optical adhesive which is transparent and has an intermediate value between the refractive indices of the phosphor element 1 and the phosphor element 2 is used.

The phosphor elements 1 and 2 are arranged in an array, and a shielding member 4 is inserted between adjacent elements.

The operation of the radiation detector in which the phosphor elements are formed in a two-layer structure will be described.

For example, in a radiation tomography apparatus,
Both the shooting mode and the fluoroscopy mode are used.

The photographing mode is a mode in which high-energy, high-dose radiation is applied in order to obtain a high-accuracy image, but the radiation absorption efficiency of the phosphor element 1 is, for example, 9%.
Even if it is 0%, the remaining 10% of the radiation is
Is completely converted to light.

The light emitted from the phosphor element 1 and the light emitted from the phosphor element 2 both pass through the transparent phosphor element 2 and reach the photodiode array substrate 3, where they are converted into electric signals. No loss of radiation absorption.

On the other hand, the fluoroscopic mode is a mode in which a fluoroscopic image of the subject is obtained by the radiation that has passed through the subject, so that low-energy, low-dose radiation is irradiated as much as possible. Since the radiation is low-energy radiation, it is almost completely absorbed by the phosphor element 1, and furthermore, the phosphor element 1 uses a material having good luminous efficiency, so that light having a high intensity, for example, Gd ₂ O ₂ S In the case of a ceramic scintillator containing as a main component, light emission is obtained two to three times that of a CdWO ₄ single crystal scintillator, and the light passes through the phosphor element 2 which is very excellent in transparency. Since the light can reach the photodiode array substrate 3 without attenuation and a large signal can be obtained even with a low dose of radiation, a high quality image can be formed.

FIG. 2 shows a method of manufacturing a radiation detector.

5 is a phosphor having high transparency and good radiation absorption efficiency, such as a CdWO ₄ single crystal scintillator;
Phosphor with good radiation emission efficiency such as a ceramic scintillator containing d ₂ O ₂ S as a main component, 6, 8, and 11 are optical adhesives having radiation and light transmission properties, and 9 is a ceramic or crystal such as alumina. A radiation-transparent substrate or film made of, 10 is a cut groove, 3 is a photodiode array substrate as a photoelectric conversion element for converting fluorescence from a phosphor into an electric signal, and 4 is a shielding material.

First, as shown in FIG. 2A, a rectangular parallelepiped phosphor 7 is bonded onto a film 9 with an optical adhesive 8, and a rectangular parallelepiped phosphor 5 is bonded thereon with an optical adhesive 6.

Next, a plurality of grooves 10 are cut in parallel with the phosphors 5 and 7 using a multi-wire saw or a diamond cutter as shown in FIG. At this time, the groove 10 to be cut should not be cut to the lower end of the phosphor 7 or the depth of the optical adhesive 8. In this way, phosphor element rows that are completely divided into an array at a predetermined pitch are formed.

Here, the shielding member 4 is inserted into the groove 10 and fixed.

Then, as shown in (c), the radiation detector is completed by further bonding and fixing the photodiode array substrate 3 on the phosphor 5 via the optical adhesive 11.

In the above embodiment, the phosphor element 1 is Gd ₂ O
_Although a ceramic scintillator containing ₂ S as a main component is used, for example, a crystal or the like containing CsI: Tl as a main component can be used.

In the above-described embodiment, the radiation detectors arranged in a one-dimensional array are described. However, grooves are formed in a direction perpendicular to the grooves cut in the phosphors 5 and 7. , By inserting a shielding plate into this groove,
The radiation detector may be a two-dimensional array.

[0030]

As described above, according to the present invention,
Both radiation absorption efficiency and radiation emission efficiency can provide a high radiation detector, and high energy, even when irradiating high dose radiation, low energy, even when irradiating low dose radiation, In any case, a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a radiation detector according to one embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the radiation detector of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional radiation detector.

Claims (1)

[Claims] 1. A radiation detector comprising: a fluorescent element that emits light by radiation; and a photoelectric conversion element that detects fluorescence by the fluorescent element, wherein the fluorescent element has fluorescent light with high emission efficiency on a radiation incident side. A radiation detector comprising a two-layer structure of a body element and a phosphor element having a high transparency and a high radiation absorption efficiency below the body element.