JPH10274675A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector capable of preventing after-glow in simple constitution and obtaining a sufficient resolution. SOLUTION: When radiation is emitted from upward, it is converted into a beam by a phosphor element 1, and the beam is input to a photoelectric conversion element 3 through a next filter 2. Influence by the after-glow can be eliminated by possessing characteristics attenuating the part of optical wavelength causing the after-glow.

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 for a digital X-ray imaging apparatus, an X-ray CT apparatus, and the like.

[0002]

2. Description of the Related Art For example, a digital X-ray imaging apparatus or an X-ray C
As a radiation detector used in a T device or the like, a combination of a fluorescent element and a photoelectric conversion element is widely used.

As shown in FIG. 5, a photoelectric conversion element 12 is arranged below a fluorescent element 11, and the photoelectric conversion elements 12 are further divided and arranged inside so that signals can be taken out corresponding to channels and pixels. An output terminal 13 corresponding to the divided elements is provided.

[0004] Although not shown, a groove is formed in the fluorescent element 11 to extract a signal corresponding to a channel or a pixel and divided into strips, and a shielding plate for shielding radiation is inserted into the groove. A plurality of channels are also used.

In such a radiation detector, when radiation enters the fluorescent element 11 from above, the fluorescent element 11
Is converted into light, and the light is converted into an electric signal by the photoelectric conversion element 12 to detect the radiation.

[0006] By the way, the amount of radiation to be applied to the fluorescent element is reduced, or immediately after the irradiation is stopped, the amount of fluorescent light must be reduced or the fluorescent light must be stopped in accordance with the amount of radiation immediately. However, a phenomenon called afterglow occurs in which the fluorescence output does not immediately decrease and the output before the fluorescence remains for a while.

[0007]

When an afterglow is present, a sufficient resolution cannot be obtained when an image is reconstructed based on a signal detected by a radiation detector. Therefore, there is a method to correct the influence of this afterglow by software.However, complicated calculation is required, and hardware such as a computer is separately required, and the configuration and the calculation method become very complicated. there were.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and prevents afterglow with a simple structure.
An object of the present invention is to provide a radiation detector capable of obtaining a sufficient resolution.

[0009]

In order to achieve the above object, a radiation detector according to the present invention comprises a fluorescent element for converting incident radiation into light and a photoelectric conversion element for converting this light into an electric signal. In this radiation detector, a filter is arranged between the fluorescent element and the photoelectric conversion element so as to block transmission of a wavelength of light output due to afterglow generated in the fluorescent element.

[0010]

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 the radiation detector according to the present invention, FIG. 2 shows the wavelength distribution of light emitted from the fluorescent element, FIG. 3 shows the characteristics of the filter, and FIG. 4 shows the wavelength distribution of the light after passing through the filter. .

Reference numeral 1 denotes a fluorescent element composed of a scintillator or the like;
Denotes a filter, and 3 denotes a photoelectric conversion element such as a photodiode. The inside of the photoelectric conversion element 3 is further divided into a plurality of elements for extracting signals corresponding to a plurality of channels and pixels, and is arranged in a one-dimensional or two-dimensional manner.
An output terminal 4 is provided for independently extracting a signal from each of the divided elements.

The filter 2 is formed between the fluorescent element 1 and the photoelectric conversion element 3. When radiation is irradiated from above, the radiation is converted into light by the fluorescent element 1, and this light is input to the photoelectric conversion element 3 through the next filter 2, and the photoelectric conversion element 3 converts this light into an electric signal. ,
The signal is sent from the output terminal 4 to an image processing device or the like through a wire.

FIG. 2 shows the fluorescence spectrum of the fluorescent element 1. The horizontal axis represents the wavelength and the vertical axis represents the magnitude of the output. As can be seen from FIG. In many cases, the light is not monochromatic light, and is distributed in a certain range.

The short wavelength component is a portion used as a detection signal, but the long wavelength portion is a light component causing afterglow as shown in the figure.

Therefore, as shown in FIG. 3, a filter 2 having such a characteristic as to attenuate a long wavelength portion of the light causing the afterglow and transmit a short wavelength portion used as a detection signal is used.

FIG. 4 shows the spectrum of the fluorescence output reaching the photoelectric conversion element 3 when the filter 2 having the characteristics shown in FIG. 3 is used. Although a short wavelength portion used as a detection signal (measurement signal) appears as an output, the component relating to afterglow is almost 0, and the influence of afterglow can be eliminated.

In the above embodiment, the filter 2 is provided between the fluorescent element 1 and the photoelectric conversion element 3, but the filter may be formed on the photoelectric conversion element 3 in the form of an interference film.

[0019]

As described above, according to the present invention,
Since a filter that does not transmit the wavelength component of light generated by afterglow is provided between the fluorescent element and the photoelectric conversion element, the measurement signal can be detected without any problem and the influence of afterglow can be eliminated. , Sufficient resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a radiation detector of the present invention.

FIG. 2 is a diagram showing an emission spectrum of a fluorescent element.

FIG. 3 is a diagram showing characteristics of a filter of the radiation detector of the present invention.

FIG. 4 is a diagram showing an emission spectrum after passing through a filter.

FIG. 5 is a diagram showing a configuration of a conventional radiation detector.

Claims (1)

[Claims] 1. A radiation detector comprising: a fluorescent element for converting incident radiation into light; and a photoelectric conversion element for converting the light into an electric signal, wherein a wavelength of light output by afterglow generated in the fluorescent element is determined. A radiation detector, wherein a filter for blocking transmission is arranged between the fluorescent element and the photoelectric conversion element.