JPH0772257A - Radiation detector - Google Patents

Abstract

PURPOSE:To read recorded radiation-image information efficiently on time base and to obtain a radiation image in high S/N. CONSTITUTION:A radiation detector 30 comprises a first solid-state photodetector 31 and a scintillator 33, which is provided at the neighborhood of the solid- state photodetector 31. A second solid-state photodetector 32 having fewer pixels than pixels in the first solid-state photodetector 31 is provided at the neighborhood of the first solid-state photodetector 31 in the detector 30. Before the reading of the image information with the first solid-state photodetector 31, the image information is read out of the second solid-state photodetector 32, whose number of the pixel is smaller, and the conditions for reading the image information with the first solid-state photodetector 31 are determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector, and more particularly to a radiation detector using two solid-state photodetectors having different numbers of pixels.

[0002]

2. Description of the Related Art Conventionally, in radiography in various fields such as medical radiography for radiography for the purpose of medical diagnosis and industrial radiography for the purpose of destructive inspection of substances, etc. A so-called radiographic method combined with a radiographic film is used. According to this method, when radiation such as X-rays transmitted through the subject enters the intensifying screen, the phosphor contained in the intensifying screen absorbs the energy of this radiation and emits fluorescence (instantaneous emission). Due to this light emission, the radiographic films superposed so as to be in close contact with the intensifying screen are exposed to light, and a radiographic image is formed on the radiographic film. In this way, the radiation image can be directly obtained as an image visualized on the radiation film.

On the other hand, in various fields, a radiographic image recorded on a radiographic film is photoelectrically read to obtain an image signal, the image signal is subjected to appropriate image processing, and then the image is reproduced and recorded. It is being appreciated. For example, an X-ray image is recorded using a film having a low gamma value designed so as to be suitable for later image processing, and the X-ray image is read from the film on which the X-ray image is recorded and converted into an electric signal. By performing image processing on this electric signal (image signal) and reproducing it as a visible image on a copy photograph or the like, a reproduced image with good image quality performance such as contrast, sharpness, and graininess is obtained. (See Japanese Patent Publication No. 61-5193).

In addition, the applicant of the present invention has conducted radiation (X-ray, α
Ray, β ray, γ ray, electron beam, ultraviolet ray, etc.), a part of this radiation energy is accumulated, and when excitation light such as visible light is then irradiated, stimulated emission is shown according to the accumulated energy. By using a stimulable phosphor (stimulable phosphor), the radiation image information of a subject such as a human body is once recorded on a sheet-shaped stimulable phosphor, and this stimulable phosphor sheet is excited by a laser beam or the like. Scan to generate stimulated emission light, photoelectrically read the obtained stimulated emission light to obtain an image signal,
A radiation image recording / reproducing system for outputting a radiation image of a subject as a visible image on a recording material such as a photographic light-sensitive material or a CRT based on this image data has already been proposed (JP-A-55-12429, JP-A-56-56). No. 11395, No. 55-163472,
56-104645, 55-116340, etc.).

This system has the practical advantage of being able to record images over a very wide radiation exposure area as compared to conventional radiographic systems using silver halide photography. That is, in the stimulable phosphor, it has been recognized that the amount of emitted light stimulated by excitation after storage is proportional to the radiation exposure dose over a very wide range, and therefore the radiation exposure dose varies depending on various imaging conditions. Even if it fluctuates significantly, the amount of stimulated emission light emitted from the stimulable phosphor sheet is read by the photoelectric conversion means with the reading gain set to an appropriate value and converted into an electric signal. Recording material such as photographic light-sensitive material,
By outputting a radiation image as a visible image on a display device such as a CRT, it is possible to obtain a radiation image that is not affected by variations in radiation exposure dose.

However, in order to obtain a radiographic image with such a radiographic system, when the above-mentioned radiographic image is directly visualized, the radiographic film used for radiography and the intensifying screen are made to coincide in sensitivity region. Need to do.

In the system for photoelectrically reading a radiation image using the above-described radiographic film and stimulable phosphor sheet, image processing is performed on the radiation image to adjust the density and contrast according to the purpose. Or, the radiation image must be converted into an electric signal once, and it is necessary to perform reading scanning using an image reading device for that purpose, which makes the operation for obtaining the radiation image complicated and obtains the radiation image. It takes time to get to.

Therefore, in order to solve the above problems caused by the conventional system, a radiation detector has been proposed (for example, Japanese Patent Laid-Open Nos. 59-211263 and 2-164067).
Publication, PCT International Publication Number WO92 / 06501, Signal, n
oise, and read out considerations in the developmen
t of amorphous silicon photodiode arrays for radio
therapy and diagnostic x-ray imaging, LE Antonuk
et.al, University of Michigan, RAStreet Xerox,
PARC, SPIE Vol.1443 Medical Imaging V; Image Physic
s (1991), p.108-119).

This radiation detector comprises, for example, a plurality of solid-state photodetector elements arranged in a matrix of transparent conductive films and conductive films sandwiching an amorphous semiconductor film on a substrate made of quartz glass having a thickness of 3 mm and orthogonal to each other. As described above, a scintillator for converting radiation into visible light is laminated on a solid-state photodetector composed of a plurality of signal lines and scanning lines which are patterned in a matrix.

By arranging this radiation detector so that the scintillator faces the surface on the radiation incident side, and irradiating the radiation detector with the radiation transmitted through the subject, the radiation is directly incident on the scintillator and converted into visible light. The converted visible light is detected by the photoelectric conversion unit of the solid-state light detection element and photoelectrically converted into an image signal carrying radiation image information. This image signal is read out and output from a transfer unit provided in each solid-state light detecting element of the radiation detector by a predetermined reading means.

On the other hand, a radiation detector which does not require a scintillator has also been proposed. This radiation detector has the scintillator removed in the above-mentioned radiation detector, and (i) radiation of The solid-state photodetector (MATE
RIAL PARAMETERS IN THICK HYDROGENATED AMORPHOUS SI
LICON RADIATION DETECTORS, Lawrence Berkeley Labora
tory.University of California, Berkeley.CA 94720 Xe
rox Parc.Palo Alto.CA 94304), or (ii) a solid-state photodetector (Metal / Amorphous Silicon Multilayer Radiat) in which two or more layers are stacked with a metal plate in the radiation transmission direction.
ion Detectors, IEE TRANSACTIONS ONNUCLEAR SCIENCE.V
OL.36.NO.2.APRIL 1989), or (iii) CdTe
A radiation detector having a configuration using a semiconductor radiation detector (Japanese Patent Laid-Open No. 1-216290) such as, for example, directly detecting radiation without passing through visible light and converting it into an electric signal or the like. The signal is a solid-state photodetector arranged in a matrix in accordance with a read signal input to the scanning line similarly to the above-mentioned radiation detector (a large number of elements constituting the radiation detector of (i) to (iii) above). ) Is read and output separately.

The image signal output in this way is subjected to various signal processing by a signal processing device in the subsequent stage, and then CR.
It is reproduced as visible information or the like by a reproducing means such as T.

By using the above radiation detector, the radiation image of the subject can be obtained in real time without complicated operations, and the radiation image information can be immediately reproduced. It can be resolved.

Here, in the radiation image recording / reproducing system using the above-mentioned stimulable phosphor sheet, before the image signal is obtained by reading under the optimum reading condition according to the dose of the radiation applied to the stimulable phosphor sheet. , Pre-reading by scanning the stimulable phosphor sheet with a low-level light beam in advance to read the outline of the radiation image recorded on this sheet,
The pre-reading image signal obtained by this pre-reading is analyzed, and then the sheet is irradiated with a high-level light beam and scanned,
There is also a system configured to perform a main reading in which an image signal is obtained by reading the radiation image under optimum reading conditions.

In addition, regardless of whether the system performs the prefetching or the system that does not perform the prefetching, the obtained image signal (including the prefetched image signal) is analyzed, and the optimum image when the image signal is subjected to the image processing is analyzed. There is also a system that determines processing conditions. Here, the image processing condition is a general term for various conditions when the image signal is subjected to a process that affects the gradation and sensitivity of a reproduced image based on the image signal. The method of determining the optimum image processing conditions based on this image signal is not limited to the system using the stimulable phosphor sheet,
For example, it is also applied to a conventional system for obtaining an image signal from a radiation image recorded on a recording sheet such as an X-ray film.

The calculation for obtaining the reading condition and / or the image processing condition (hereinafter, referred to as reading condition etc.) based on the image signal (including the preread image signal) is statistically processed in advance on a large number of radiation images. The algorithm is determined from the result.

As one of the conventionally adopted algorithms, there is known a method of obtaining a histogram of an image signal and obtaining a reading condition based on the histogram (Japanese Patent Laid-Open No. 60-156055 and Japanese Laid-Open Patent Publication No. Sho 60-156055). 60-185944, JP-A-61-280163, JP-A-63-233658, JP-A-61-170730, JP-A-63-262141).

As described above, by reading under the reading condition determined based on the histogram of the image signal directly carrying the property of each image and further performing the image processing according to the image processing condition, for example, the photographing of each image is performed. Even if there is a change in the radiation energy level range stored and recorded on the sheet due to changes in the subject or imaging site, or changes in the radiation exposure dose, etc. It is possible to obtain a visible image displayed in a density range suitable for image interpretation.

[0019]

By the way, in a radiographic image for medical treatment, higher resolution is required mainly for the purpose of finding fine lesions, and in the above radiation detector as well, in order to improve the resolution, The number of pixels (the number of detection elements) per unit area is increasing.

However, when the number of pixels increases, there is a problem that it takes time to output the radiation image information accumulated in each pixel from all the pixels. For a radiation detector having a certain area, when the image information is recorded only in a part of the area, the image information is obtained from all the pixels including the pixels in the area where this information is not recorded. Is not efficient in terms of time.

Further, in order to obtain a reproduced image having an appropriate dynamic range from the image information recorded in the radiation detector, it is necessary to obtain an appropriate gain in the step of reading the image information from the radiation detector. is important. Such a pre-reading system or a system for determining image processing conditions (hereinafter collectively referred to as EDR processing) has been put to practical use in a system using a conventional stimulable phosphor sheet, but the radiation detector is When the image information is read, that information is lost, so it is not possible to read the recorded image information in advance.
As a result, there is a drawback in that the S / N of the reproduced radiation image cannot be improved.

The present invention has been made in view of the above circumstances, and provides a radiation detector capable of efficiently reading out recorded radiation image information in time and reproducing a high S / N radiation image. It is intended to be provided.

[0023]

A radiation detector according to the present invention is formed by laminating two radiation detectors having different numbers of pixels (solid-state photodetection elements).

That is, the first radiation detector according to the present invention, as described in claim 1, detects a radiation carrying image information and converts it into an output of an image signal representing a radiation image as a whole. A first solid-state photodetector in which a large number of solid-state photodetectors are arranged, and the number of solid-state photodetectors stacked in the first solid-state photodetector is smaller than that of the first solid-state photodetector. A second solid-state photodetector having a number of solid-state photodetectors.

Here, as the first and second solid-state photodetectors, for example, a matrix of a transparent conductive film and a conductive film sandwiching an amorphous semiconductor film on a substrate made of quartz glass having a predetermined thickness. A solid-state photodetector composed of a plurality of solid-state photodetectors arranged in a matrix and a plurality of signal lines and scanning lines that are patterned in a matrix so as to be orthogonal to each other, and the above-mentioned (i) radiation The solid-state photodetector whose thickness in the transmission direction is set to be about 10 times thicker than the normal one, or (ii) the solid-state photodetector in which two or more layers are stacked in the radiation transmission direction via a metal plate, (iii) CdT
A semiconductor radiation detector such as e can be used.
Further, the predetermined thickness means a thickness at which the amount of absorbed radiation is not large enough to deteriorate the image quality of a radiation image, but specifically, a certain level of strength for supporting the solid-state photodetector is required. Therefore, it is about several hundreds of microns.

Further, having the number of pixels smaller than the number of pixels of the first solid-state photodetector means that the size of each pixel is
By being set larger than the pixels of the first solid-state photodetector, it means that the number of pixels is smaller than the number of pixels of the first solid-state photodetector.

The second radiation detector according to the present invention is, as described in claim 2, provided with a plane scintillator for converting radiation carrying image information into visible light, and adjacent to the scintillator. A first solid-state photodetector in which a large number of solid-state photodetector elements are two-dimensionally arranged, each of which detects the visible light converted from each part of the scintillator and converts it into an output of an image signal representing a radiation image as a whole And a second solid-state photodetector having a smaller number of solid-state photodetectors than the number of solid-state photodetectors of the first solid-state photodetector stacked on the first solid-state photodetector or the scintillator. It is characterized by consisting of a vessel.

Here, the solid-state photodetector is different from the solid-state photodetector, which constitutes the first radiation detector of the present invention and which can directly convert radiation into an electric signal, and has a high radiation resistance. A conventional solid-state photodetector, which is not sensitive, but which converts visible light into an electrical signal can be used.

The arrangement of the constituent elements of the second radiation detector of the present invention specifically means the arrangement shown in the following (1) to (2). That is, (1) a scintillator, a first solid-state photodetector, and a second solid-state photodetector arranged in this order, or (2)
The first solid-state photodetector, the scintillator, and the second solid-state photodetector are arranged in this order.

As described in claim 3, the third radiation detector according to the present invention is the second radiation detector according to the present invention, wherein the third radiation detector is adjacent to the laminated surface or the outer surface of the second radiation detector. And a second scintillator provided as described above.

Here, the arrangement of the constituent elements of the third radiation detector of the present invention specifically means the arrangements shown in the following (3) to (5). That is, (3) the first scintillator,
A first solid-state photodetector, a second solid-state photodetector, a second scintillator arranged in this order, or (4) a first solid-state photodetector, a first scintillator, a second solid-state photodetector, Arrangement of second scintillator in order or (5) first scintillator, first solid-state photodetector, second scintillator, second
Of solid-state photodetectors.

[0032]

According to the first radiation detector of the present invention, the radiation that carries the radiation image information by passing through the subject or emitted from the subject is the first solid-state photodetector and the second solid-state photodetector. Each is detected by a photodetector.
Thus, the radiation image information detected by the two solid-state photodetectors is first read from the second solid-state photodetector having a small number of solid-state photodetection elements (pixels), and based on the read radiation image information, By recognizing the outline of the irradiation field in which the radiation image information of the subject or the subject is recorded, and reading the radiation image information only from the region that requires the reproduction of the first solid-state photodetector based on the result, the subject ( Alternatively, it is possible to omit the reading of the image information from the area (so-called blank area) where the radiation image information of the subject is not recorded or the area that does not require reproduction, and to reduce the number of pixels to be read as a whole. Therefore, desired radiation image information can be efficiently output in time.

Further, the radiation image information detected by the second solid-state photodetector is read out to recognize the recorded radiation dose and the like, and based on various information such as the recognized radiation dose, the main reading condition is obtained. (Pre-reading system) or image processing conditions (system for determining image processing conditions), and based on the result, read out radiation image information from the first solid-state photodetector in an appropriate dynamic range. You can

As described above, according to the first radiation detector of the present invention, the detected radiation image information can be efficiently read in time, and the radiation image information can be read in an appropriate dynamic range. High S /
N radiographic images can be obtained.

Further, according to the second radiation detector of the present invention, the radiation carrying the radiation image information by passing through the subject or being emitted from the subject is intensified by the scintillator according to the intensity of the radiation. Converted to visible light. The visible light obtained by this action carries the radiation image information of the subject (or the subject), and is detected as radiation image information of the subject as a whole by the first solid-state photodetector and the second solid-state photodetector. To be done. Hereinafter, the same operation as the first radiation detector of the present invention is performed.

According to the third radiation detector of the present invention, since the second scintillator is provided adjacent to the second solid-state photodetector, the radiation incident on this radiation detector is the second Is converted into visible light by the scintillator and the visible light is detected by the second solid-state photodetector, so that the light collection efficiency of the second solid-state photodetector can be increased.

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a radiation detector according to the present invention. The radiation detector 30 shown is
A first solid-state photodetector 31 having a predetermined number of pixels (solid-state photodetection elements) that detects visible light and converts it into an electric signal;
A scintillator 33 provided adjacent to the first solid-state photodetector 31, and a scintillator 33 provided adjacent to the first solid-state photodetector 33,
The second solid-state photodetector 32 has a smaller number of pixels (solid-state photodetection elements) than the number of pixels of the first solid-state photodetector 31. Here, for example, when the number of pixels of the first solid-state photodetector 31 is 640 × 400 (= 2.56 × 10 ⁵ ) pixels,
The number of pixels of the solid-state photodetector 32 is 160 × 100 (= 1.
6 × 10 ⁴⁾ may be set to about the pixel, the area of one pixel of the second solid state photodetector 32 has an area of 16 pixels of the first solid state photodetector 31. Here, the scintillator 33 is Gd
It is made of a phosphor such as ₂ O ₂ S or CsI.

FIG. 2 is a configuration diagram showing a detailed configuration of the solid-state photodetector P constituting the solid-state photodetector 31 used in the radiation detector of this embodiment. The solid-state photodetector P has signal lines 31B and 31H made of a patterned conductive film on a substrate 31A made of a resin sheet, and is made of amorphous silicon.
Photodiode 31E as a photoelectric conversion part including 31C and transparent electrode 31D, and thin film transistor 31 as a transfer part having transfer electrode 31J in amorphous silicon 31F.
It is composed of G. Transfer electrode here
Reference numeral 31J is a gate connected to a scanning line not shown, and signal line 31H is a drain connected to a signal line not shown. The solid-state photodetector 31 is configured by arranging a plurality of the solid-state photodetectors P thus configured in a two-dimensional manner. The function of the solid-state photodetector P is that the incident light is received by the photodiode 31E, and a signal charge is generated and stored in the photodiode 31E.
Next, a predetermined scanning signal is sent to the scanning line from a signal reading circuit (not shown) connected to the scanning line, a voltage is applied to the transfer electrode 31J as a gate connected to the scanning line, and the signal line 31
A current flows between B / 31H. That is, the signal charges generated in the photodiode 31E are transferred to the transfer register (not shown) through the thin film transistor 31G and output.

Next, the operation of the radiation detector 30 of the present invention will be described. FIG. 3 shows a first example of using the radiation detector 30 of the present invention to explain the operation of the radiation detector 30 of the present invention.
It is a schematic block diagram which shows the structure of the principal part of the radiation image reading apparatus of FIG.

As shown in FIG. 1, the radiation detector 30 is arranged so that the scintillator 33 becomes an incident surface of the radiation R emitted from the radiation source 20, and the radiation detector 30 is provided with an object.
By irradiating the radiation R transmitted through 10, the radiation R
Is directly incident on the scintillator 33, the radiation R is converted by the scintillator 33 into visible light having an intensity corresponding to the intensity, and the converted visible light is the first solid-state light provided adjacent to the scintillator 33. It is detected by the amorphous silicon 31C (see FIG. 2) of the detector 31. Then, this visible light is photoelectrically converted into a first image signal E carrying radiation image information and accumulated in each solid-state photodetecting element as an electrostatic capacitance signal Cp corresponding to the emission intensity of visible light in the amorphous silicon 31C, Each of the accumulated electrostatic capacitance signals Cp is individually read from each solid-state photodetecting element by applying a predetermined scanning signal from a signal reading circuit (not shown).

Further, the visible light converted by the scintillator 33 passes through the first solid-state photodetector 31 and reaches the second solid-state photodetector 32. It is detected by a similar action and photoelectrically converted into a second image signal E ′ carrying radiation image information. The image signal E'after the photoelectric conversion is accumulated in each solid-state photodetecting element as an electrostatic capacitance signal Cp 'by the same operation as described above, and each accumulated electrostatic capacitance signal Cp' is read out as a signal (not shown). When a predetermined scanning signal is given from the circuit, the respective solid-state photodetecting elements are individually read.

First, the second image signal E '(capacitance signal Cp') is output to the EDR processing device 51, and the EDR processing device 51 gives an outline of the amount of radiation applied to the radiation detector 30. Based on the recognition result, the main reading condition is determined (pre-reading system) or the image processing condition is determined (system for determining the image processing condition), and the result is written in the gain modulation means 52.

Next, the image signal E (electrostatic capacitance signal Cp) read from the first solid-state photodetector 31 is input to a variable gain (offset) amplifier 63 via an amplifier 61 and a logarithmic converter 62. Here, the gain modulation means 52 reads the image signal E input to the variable gain (offset) amplifier 63 in an appropriate dynamic range based on the written determination conditions. The image signal E read in an appropriate dynamic range is output to the A / D converter 64, converted into a digital signal, and reproduced as a visible image by the image reproducing device 65 in the subsequent stage. The reproduced visible image is an image based on the information read by the radiation detector 30 in an appropriate dynamic range, and thus can be a high S / N image.

FIG. 4 shows a second embodiment of the radiation detector 30 of the present invention for explaining the operation of the radiation detector 30 of the present invention.
It is a schematic block diagram which shows the structure of the principal part of the radiation image reading apparatus of FIG.

Similar to the first radiation image reading apparatus, the radiation R transmitted through the subject 10 is incident on the scintillator 33, the radiation R is converted into visible light by the scintillator 33, and the converted visible light is The first solid-state photodetector 31 provided adjacent to the scintillator 33 detects and photoelectrically converts it into a first image signal E carrying radiation image information. The image signal E after the photoelectric conversion is accumulated in each solid-state photodetecting element as an electrostatic capacitance signal Cp, and each accumulated electrostatic capacitance signal Cp is given by a predetermined scanning signal from a signal reading circuit (not shown). The solid-state photodetectors are read out individually.

The visible light converted by the scintillator 33 passes through the first solid-state photodetector 31, reaches the second solid-state photodetector 32, and is detected by the second solid-state photodetector 32. , Is photoelectrically converted into a second image signal E ′ carrying radiation image information. The image signal E ′ after this photoelectric conversion
Is accumulated in each solid-state photodetecting element as an electrostatic capacitance signal Cp 'by the same operation as described above, and each accumulated electrostatic capacitance signal Cp' is generated by a predetermined scanning signal from a signal reading circuit (not shown). Each is read from the detection element.

First, the second image signal E '(electrostatic capacitance signal Cp') is input to the signal value comparator 72, and the value is compared with a predetermined value Vref stored in the memory 71 in advance. It Here, the predetermined value Vref is a value between the detection value shown when the radiation detector 30 is irradiated with the radiation and the detection value shown when the radiation detector 30 is not irradiated, and determines whether or not the radiation is irradiated. It is a predetermined threshold.

As a result of the magnitude comparison by the signal value comparator 72, when the value of the image signal E'is larger than the predetermined value Vref,
The image signal E'is input to the irradiation field recognition memory 73, and it is recognized that the pixel is in the irradiation field. On the other hand, when the predetermined value Vref is larger than the value of the image signal E ', the image signal E' ′ Is not input to the irradiation field recognition memory 73, and it is recognized that the pixel is not in the irradiation field. As a result, the pixel input to the irradiation field recognition memory 73 is in the irradiation field of the radiation R, and the signal indicating the pixel is input to the read pixel selection unit 78, and the read pixel selection unit 78 corresponds to the pixel in the irradiation field. From only the pixels of the first solid-state photodetector 31,
The image signal E is read.

As described above, prior to reading the image signal E for all the pixels from the first solid-state photodetector 31 having a large number of pixels, all the pixels from the second solid-state photodetector 32 having a small number of pixels are read out. The number of read pixels can be reduced by reading the image signal E'of the pixel to recognize the radiation irradiation field and reading the image signal E only of the pixel in the irradiation field of the first solid-state photodetector 31. The radiation image information can be read efficiently.

As described above, according to the radiation detector of the present embodiment, the radiation image information can be efficiently read in time, and the radiation image of high S / N can be reproduced.

The radiation detector of the present invention can take the configuration of each embodiment shown in FIG. 5 in addition to the embodiment shown in FIG. That is, (a) the scintillator 33 is provided adjacent to the first solid-state photodetector 31.
And the second solid-state photodetector 32 is provided adjacent to the scintillator 33. (b) The first solid-state photodetector 31 is adjacent to the scintillator 33.
A second solid-state photodetector 32 is provided adjacent to the first solid-state photodetector 31 and a second scintillator 34 is provided adjacent to the second solid-state photodetector 32 (c ) A scintillator 33 adjacent to the first solid-state photodetector 31.
A second solid-state photodetector 32 is provided adjacent to the scintillator 33, and a second scintillator 34 is provided adjacent to the second solid-state photodetector 32. (d) First solid-state light Scintillator 33 adjacent to detector 31
Is provided, a second scintillator 34 is provided adjacent to the scintillator 33, and a second solid-state photodetector 32 is provided adjacent to the second scintillator 34.

In each of the above-mentioned configurations, the second scintillator 34 is provided so that the second solid-state photodetector 32 can receive a larger amount of visible light that carries radiation image information. .

The radiation detector according to the present invention is not necessarily limited to the one using the scintillator as in the above-mentioned embodiment, and in the radiation detector of the above-mentioned embodiment, instead of the ordinary solid-state photodetector, For example
(i) A solid-state photodetector whose thickness in the radiation transmission direction is set to be about 10 times thicker than a normal one, or (ii) solid-state light in which two or more layers are stacked in the radiation transmission direction via a metal plate. If a detector or (iii) a semiconductor radiation detector such as CdTe is used, it is not necessary to provide a scintillator.

[0055]

As described above in detail, in the radiation detector according to the present invention, a solid-state photodetector for signal detection for actually obtaining a reproduced image and a condition for reading image information from the solid-state photodetector are used. It is formed integrally or in close contact with the solid-state photodetector for determining the reading conditions with a smaller number of pixels, and the latter solid-state photodetector is used to determine the range necessary for reading the irradiation field etc. first. The number of pixels read out as a whole radiation detector can be reduced by detecting and only within the range is detected by the former solid-state photodetector, and the recorded radiation image information can be efficiently processed in time. Can be read.

Further, the radiation dose is read out first by the latter solid-state photodetector, an appropriate reading condition is determined, and the radiation image information is read by the former solid-state photodetector according to the condition, so that an appropriate reading condition can be obtained. Since the radiation image information can be read in the dynamic range, high S /
N radiographic images can be obtained.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a detailed configuration of a solid-state photodetector that constitutes the solid-state photodetector of the embodiment shown in FIG.

3 is a schematic configuration showing a configuration of a main part of a first radiation image reading apparatus using the radiation detector 30 of the present invention in order to explain the operation of the radiation detector 30 of the embodiment shown in FIG. Figure

FIG. 4 is a schematic configuration diagram showing a configuration of a main part of a second radiation image reading apparatus using the radiation detector 30 of the present invention in order to explain the operation of the radiation detector 30.

FIG. 5 is a schematic configuration diagram showing another embodiment of the radiation detector according to the present invention.

[Explanation of symbols]

 10 subject 20 radiation source 30 radiation detector 31 first solid-state photodetector 32 second solid-state photodetector 33 first scintillator 34 second scintillator 51 EDR processing device 52 gain modulation means 61 amplifier 62 logarithmic converter 63 Variable gain (offset) amplifier 64 A / D converter 65 Image reproduction device 71 Memory 72 Signal value comparator 73 Irradiation field recognition memory 74 Read pixel selection means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 27/14 H04N 5/32

Claims (3)

[Claims] 1. A radiation carrying image information is detected and converted into an output of an image signal representing a radiation image as a whole.
A first solid-state photodetector having a plurality of two-dimensional solid-state photodetectors, and the first solid-state photodetector laminated on the first solid-state photodetector.
And a second solid-state photodetector having a smaller number of solid-state photodetectors than the solid-state photodetector. 2. A flat scintillator for converting radiation carrying image information into visible light, and visible light converted by each part of the scintillator provided adjacent to the scintillator are detected as a whole. A first solid-state photodetector, in which a large number of solid-state photodetection elements are arranged two-dimensionally, which is converted into an output of an image signal representing a radiation image, and the first solid-state photodetector or the scintillator laminated on the first solid-state photodetector. , The first
And a second solid-state photodetector having a smaller number of solid-state photodetectors than the solid-state photodetector. 3. The radiation detector according to claim 2, further comprising a second scintillator provided adjacent to the laminated surface or the outer surface of the second solid-state photodetector.