JP3560624B2 - Image signal reading method and apparatus - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method and an apparatus for reading an image signal, and more particularly to a method and an apparatus for reading an image signal from a radiation detector that detects radiation carrying image information, converts the radiation into an image signal, and outputs the image signal.
[0002]
[Prior art]
Conventionally, in radiography in various fields such as medical radiography for radiography for medical diagnosis, industrial radiography for non-destructive inspection of substances, etc., an intensifying screen and a radiographic film have been used. A so-called combined radiographic method 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 the radiation and emits fluorescence (instantaneous emission). By this light emission, the radiographic film superimposed on the intensifying screen is exposed to light, and a radiographic image is formed on the radiographic film. In this way, the radiation image can be obtained directly as an image visualized on the radiation film.
[0003]
On the other hand, in various fields, a radiographic image recorded on a radiographic film is photoelectrically read to obtain an image signal, and after appropriate image processing is performed on the image signal, the image is reproduced and recorded. . For example, an X-ray image is recorded using a film having a low gamma value designed to be compatible with the subsequent 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 subjecting the electric signal (image signal) to image processing and reproducing it as a visible image in a copy photograph or the like, a reproduced image having good image quality performance such as contrast, sharpness, and graininess is obtained. (See Japanese Patent Publication No. 61-5193).
[0004]
Further, according to the applicant of the present invention, when radiation (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet ray, etc.) is irradiated, a part of this radiation energy is accumulated, and thereafter, when irradiated with excitation light such as visible light, the accumulated energy The radiation image information of a subject such as a human body is temporarily recorded in a sheet-shaped stimulable phosphor by using a stimulable phosphor (stimulable phosphor) which emits stimulable light in accordance with the energy thus applied. The stimulable phosphor sheet is scanned with excitation light such as laser light to generate stimulated emission light, and the obtained stimulated emission light is photoelectrically read to obtain an image signal. Based on the image data, a radiation image of the subject is obtained. A radiation image recording / reproducing system for outputting the image as a visible image to a recording material such as a photographic photosensitive material or a CRT has already been proposed (JP-A-55-12429, JP-A-56-11395, JP-A-55-163472, Id 56-10 4645, 55-116340, etc.).
[0005]
This system has the practical advantage of being able to record images over a very large radiation exposure area compared to conventional radiographic systems using silver halide photography. That is, in the case of the stimulable phosphor, it has been recognized that the amount of emitted light that is stimulated by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range. Even if fluctuates considerably, the amount of photostimulated 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. By outputting a radiation image as a visible image on a recording material such as a photographic light-sensitive material or a display device such as a CRT using, a radiation image which is not affected by a change in radiation exposure can be obtained.
[0006]
However, in order to obtain a radiographic image using such a radiographic system, when directly visualizing the above-mentioned radiographic image, it is necessary to perform radiographing by matching the sensitivity areas of the radiographic film used for radiography and the intensifying screen. There is.
[0007]
Further, in the above-described radiographic film and a system for photoelectrically reading a radiographic image using a stimulable phosphor sheet, the radiographic image is subjected to image processing as described above so that the radiographic image has a density and contrast according to the purpose. It is necessary to make adjustments or to convert the radiation image into an electrical signal once, and it is necessary to perform reading and scanning using an image reading device for that purpose. It takes time to get.
[0008]
Therefore, in order to solve the above-mentioned problems in the conventional system, a radiation detector has been proposed (for example, JP-A-59-212263, JP-A-2-16667, PCT International Publication No. WO92 / 92). / 06501 issue, Signal, noise, and read out considerations in the development of amorphous silicon photodiode arraysfor radiotherapy and diagnostic x-ray imaging, L.E.Antonuk et.al, University of Michigan, R.A.Street Xerox, PARC, SPIE Vol.1443 Medical Imaging V; Image hysics (1991), p.108-119).
[0009]
This radiation detector is composed of a plurality of solid-state photodetectors arranged in a matrix composed of a transparent conductive film and a transparent conductive film with an amorphous semiconductor film interposed therebetween on a substrate made of, for example, quartz glass having a thickness of 3 mm. It is constructed by stacking a scintillator for converting radiation into visible light on a solid-state photodetector composed of a plurality of signal lines and scanning lines patterned in a matrix.
[0010]
By arranging the radiation detector so that the scintillator faces the radiation incident side, and irradiating the radiation detector with radiation transmitted through the subject, the radiation is directly incident on the scintillator and is converted into visible light. The obtained visible light is detected by a photoelectric conversion unit of each solid-state light detection element, and is photoelectrically converted into an image signal carrying radiation image information. This image signal is read out from a transfer unit provided in each solid-state light detecting element of the radiation detector by a predetermined reading unit, and after being subjected to a predetermined image processing, is reproduced by a reproducing unit such as a CRT. By using such a radiation detector, a radiation image of a subject can be immediately reproduced without performing a complicated operation, a radiation image can be obtained immediately in real time, and the above-mentioned drawbacks of the radiographic system can be solved. can do.
[0011]
On the other hand, among the above-mentioned radiation detectors, a type in which a scintillator is removed and radiation is directly detected has been proposed. For example,
(I) A solid-state photodetector (MATERIAL PARAMETERS IN THICK HYDROGENATED AMORPHOUS SILICON RADIATION DETECTORS, Lawrence Berkeley, Canada. Parc.Palo Alto.CA 94304),
Or
(Ii) Two or more solid-state photodetectors (Metal / Amorphous Silicon Multilayer Radiation Detectors, IEEE TRANSACTIONS ON NUCLEAR SCIENCE.VOL. Or
(Iii) Semiconductor radiation detector such as CdTe (Japanese Patent Laid-Open No. 1-216290)
Etc. have been proposed. Such a radiation detector directly detects radiation without passing through a scintillator, converts the radiation into an electric signal or the like, and outputs the electric signal. The conventional system described above is similar to the radiation detector using the scintillator described above. Can be eliminated.
[0012]
[Problems to be solved by the invention]
In order to obtain a high-quality image when reproducing the image signal output from the radiation detector described above, it is necessary to secure a sufficient dynamic range of the image by increasing the amount of irradiated radiation to some extent. However, in the above-described radiation detector, the maximum value of the output image signal is limited even if a certain amount of radiation is applied due to the saturation characteristics of the capacitance of the photoelectric conversion unit and the saturation characteristics of the readout circuit. This limits the range of the image signal. Therefore, a sufficient dynamic range of the obtained image signal could not be secured.
[0013]
The present invention has been made in view of the above circumstances, and has as its object to provide a method and apparatus for reading an image signal from a radiation detector that can sufficiently secure a dynamic range of an image signal obtained by the radiation detector. .
[0014]
[Means for Solving the Problems]
A first image signal reading method according to the present invention is a method of detecting a radiation carrying image information, converting the radiation into an image signal carrying the image information as a whole, and storing the converted radiation. An image signal reading method for reading the image signal from a radiation detector including a detection element,
The image signal is read out a plurality of times while the radiation is being detected by the radiation detector.
[0015]
Here, the radiation detector is a scintillator that converts the radiation carrying image information into visible light as described above, and detects the visible light converted by each part of the scintillator, and photoelectrically converts it into an image signal carrying image information. And a solid-state photodetector that outputs an image signal by directly detecting radiation without disposing a scintillator.
[0016]
Further, the “light” in the solid-state light detection element includes not only visible light converted by the scintillator but also radiation directly applied to the element.
[0017]
Furthermore, the description "radiation is detected by the radiation detector" means that the state in which radiation is detected includes the state in which "radiation is irradiated to the radiation detector".
[0018]
In the first image signal reading method according to the present invention, the readout interval for reading out the image signal a plurality of times is changed, and the readout is performed at a predetermined readout interval among the plurality of image signals obtained by the readout a plurality of times. For one image signal and another image signal read at a short interval of a predetermined ratio with respect to the predetermined read interval, when the one image signal among the respective image signals is in a saturated state, the other image Preferably, the signal is weighted corresponding to the reciprocal of the predetermined ratio, and the weighted image signal is output.
[0019]
Here, when the image signal is saturated, the maximum value of the output image signal is limited even when a certain amount of radiation is irradiated due to the saturation characteristics of the capacitance of the photoelectric conversion unit and the saturation characteristics of the image signal reading circuit, This means that the range of the obtained image signal is limited.
[0020]
A second image signal reading method according to the present invention is arranged in a two-dimensional manner in which radiation irradiated through a subject is detected, converted into an image signal carrying a radiation image of the subject as a whole, and stored. An image signal reading method for reading the image signal from a radiation detector including a large number of solid state light detection elements,
The subject is irradiated with the radiation a plurality of times at predetermined intervals, and the image signal is read out a plurality of times in synchronization with the irradiation of the radiation.
[0021]
In the first and second image signal reading methods according to the present invention, the radiation detector includes a transfer unit for reading the stored image signal, and the transfer unit reads out the plurality of times of the image signal. Preferably, reading is performed.
[0022]
Further, the plurality of read image signals may be added and output for each of the solid-state light detection elements.
[0023]
Further, it is preferable that the plurality of readings of the image signal are performed at a reading interval shorter than a time during which the accumulated image signal is saturated.
[0024]
A first image signal reading device according to the present invention detects a radiation carrying image information, converts the radiation into an image signal carrying the image information as a whole, and accumulates the solid-state light. An image signal reading device for reading the image signal from a radiation detector including a detection element,
A control means for reading out the image signal a plurality of times while the radiation is being detected by the radiation detector is provided.
[0025]
In the first image signal reading device according to the present invention, the control means changes a reading interval for reading the image signal a plurality of times, and sets a predetermined interval among the plurality of image signals obtained by reading the image signal a plurality of times. For one image signal read at a read interval and another image signal read at a short interval of a predetermined ratio with respect to the predetermined read interval, when the one image signal among the respective image signals is in a saturated state It is preferable that the weighting means be a means for weighting the other image signal corresponding to the reciprocal of the predetermined ratio and outputting the weighted image signal.
[0026]
A second image signal reading device according to the present invention is arranged in a two-dimensional manner, which detects radiation emitted through a subject, converts the radiation into an image signal carrying a radiation image of the subject as a whole, and accumulates the signal. An image signal reading device for reading the image signal from a radiation detector including a large number of solid state light detection elements,
The object is provided with control means for irradiating the subject with the radiation a plurality of times at predetermined intervals, and reading the image signal a plurality of times in synchronization with the irradiation of the radiation.
[0027]
In the first and second image signal reading devices according to the present invention, it is preferable that the radiation detector includes a transfer unit for reading the stored image signal.
[0028]
It is preferable that the image processing apparatus further includes an adding unit that adds and outputs the plurality of read image signals for each of the solid-state light detection elements.
[0029]
Further, it is preferable that the control unit is a unit that performs the reading of the image signal a plurality of times at a reading interval shorter than a time during which the accumulated image signal is saturated.
[0030]
[Action]
A first image signal reading method and apparatus according to the present invention are such that a transfer unit reads an image signal a plurality of times while radiation is being detected by a radiation detector. For this reason, even if the maximum value of the output image signal is limited by the capacity of the photoelectric conversion unit or the saturation characteristic of the image signal reading circuit, the saturated image is obtained by adding the image signals read multiple times. An image signal higher than the signal level can be obtained. For example, by performing the addition twice, the level of the image signal doubles (0.3 digit improvement), and by performing the addition 10 times, the level of the image signal increases 10 times (1 digit improvement). Therefore, the dynamic range of the obtained image signal can be sufficiently secured.
[0031]
In addition, the reading interval for reading the image signal a plurality of times is changed, and among the obtained image signals, one image signal read at a predetermined reading interval and a short interval of a predetermined ratio with respect to the predetermined reading interval. For the other read image signals, when the capacitance of the photoelectric conversion unit is in a saturated state in one of the image signals, weighting is performed on the other image signals corresponding to a reciprocal of a predetermined ratio, By outputting a weighted image signal, even if one image signal is saturated and the maximum value of the level of the image signal is limited, the other image signals are weighted by a predetermined number of times. Thus, an image signal exceeding the saturation characteristics of the photoelectric conversion unit or the readout circuit can be obtained. Therefore, the dynamic range of the obtained image signal can be sufficiently secured.
[0032]
Furthermore, as in the second image signal reading method and apparatus according to the present invention, the subject is irradiated with radiation a plurality of times at predetermined intervals, and the image signal is read out a plurality of times in synchronization with the irradiation of the radiation. As in the first image signal reading method and apparatus according to the present invention, an image signal having a sufficient dynamic range can be obtained.
[0033]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0034]
FIG. 1 is a diagram showing an image signal reading system using a radiation detector for carrying out a first embodiment of the image signal reading method according to the present invention. As shown in FIG. 1, a system for implementing an image signal reading method according to the present invention includes a scintillator (not shown) for converting irradiated radiation into visible light, and a visible light converted by the scintillator. A plurality of two-dimensional solid-state light detection elements 23 each including a photoelectric conversion unit 18 that photoelectrically converts visible light into an image signal carrying a radiation image of a subject and a transfer unit 19 that reads out image signals stored in the photoelectric conversion unit 18. The radiation detector is configured by stacking the arranged solid-state light detectors 2. Each of the solid-state photodetectors 23 is connected by a scanning line 20a and a signal line 20b as shown in FIG. 1. The scanning line 20a extends in the horizontal direction of FIG. It is connected to the gate of the transfer section 19 (transistor) of the light detection element 23. On the other hand, the signal line 20b extends in the vertical direction in FIG. 1 and is connected to the transfer register 22 and the drain of each transfer unit 19.
[0035]
Here, the details of the solid-state light detection element 23 will be described. FIG. 2 is a diagram illustrating details of the solid-state light detection element 23. As shown in FIG. 2, the solid-state photodetector 23 has signal lines 12A and 12B made of a conductive film formed by patterning on a substrate 11 made of a resin sheet, and a photoelectric conversion unit made of amorphous silicon 13 and a transparent electrode 14. It comprises a photodiode 15 as 18, an amorphous silicon 16, and a thin film transistor 17 as a transfer section 19 including a transfer electrode 16 </ b> A (gate) provided in the amorphous silicon 16. Here, the signal line 12B is a drain, is connected to the above-described signal line 20b, and the transfer electrode 16A is connected to the scanning line 20a. By arranging a plurality of the solid-state photodetectors 23 having such a configuration in a two-dimensional manner, the solid-state photodetector 2 is constituted. ₂ O ₂ A radiation detector is constituted by laminating the scintillator 3 made of a phosphor such as S or CsI.
[0036]
Next, the operation of the image signal reading system according to the present invention will be described.
[0037]
FIG. 3 is a diagram for explaining the operation of the system for implementing the image signal reading method according to the present invention.
[0038]
As shown in FIG. 3, an X-ray 5 emitted from an X-ray source 4 is applied to a subject 6 and passes through the subject 6. The X-ray 5 transmitted through the subject 6 is applied to the radiation detector 1. The X-rays 5 applied to the radiation detector 1 are applied to the scintillator 3 and converted into visible light. The converted visible light is received by the photodiode 15 as the photoelectric conversion unit 18 of each solid-state photodetector 23 constituting the solid-state photodetector 2, and a signal charge is generated in the photodiode 15. In this way, signal charges proportional to the emission luminance of visible light, that is, the intensity of incident radiation are generated in each solid-state light detection element 23.
[0039]
Next, a transfer pulse is sent from the scanning pulse generator 21 to the transfer unit 19 provided in each of the solid-state photodetectors 23 in the top row, and the switch of the transfer unit 19 in each of the solid-state photodetectors 23 in the top row is turned on. A state (a state in which a voltage is applied to the transfer electrode 16A of the solid-state photodetector 23 and a current flows between the signal lines 12A and 12B). That is, the signal charge generated in the photodiode 15 is transferred through the thin film transistor 17 as the transfer unit 19. As a result, the signal charges of the solid-state photodetectors 23 in the uppermost row are sent to the transfer register 22 at the same time. From the output terminal 22a of the transfer register 22, an electric signal (image signal) S for each solid-state light detecting element 23 is extracted in a time-series manner.
[0040]
In this way, the transfer pulse is sent from the scanning pulse generator 21 to each column sequentially from the top row to the bottom row, and the image signal S from each solid state photodetector 23 in each row is time-sequentially output from the output terminal 22a. Is output.
[0041]
The process of outputting the image signal S by sending a pulse from the scanning pulse generator 21 is performed a plurality of times while the subject 6 is irradiated with the X-rays 5. The time interval for outputting the image signal S a plurality of times is a time until the transfer unit 19 becomes saturated, and is an interval of about several ms to several tens ms.
[0042]
The image signal S output in this manner is input to the image processing means 7 shown in FIG. The image signal S 'thus added is input to the reproducing means 8 and reproduced as a visible image.
[0043]
The image signal S is read out a plurality of times during the irradiation of the X-rays 5 transmitted through the subject 6 in this manner, and the image signal S is added for each of the solid-state light detection elements 23, so that the solid-state light detection is performed. An image signal S exceeding the saturation level of the element 23 can be obtained, and the added image signal S has a wide dynamic range. Therefore, if the added image signal S is reproduced, a high-quality image with a secured dynamic range can be obtained.
[0044]
As the reproducing means 8, various means such as a means for electronically displaying a CRT or the like and a means for recording a radiation image displayed on the CRT or the like in a video printer or the like can be employed. Further, the radiation image of the subject 6 may be recorded and stored on a magnetic tape, an optical disk, or the like.
[0045]
Next, a second embodiment of the present invention will be described.
[0046]
The second embodiment of the image signal reading method according to the present invention is characterized in that the image signal reading interval in the above-described first embodiment of the image signal reading method according to the present invention is changed. That is, the interval at which pulses are sent from the scanning pulse generator 2 shown in FIG. 1 is changed. For example, the readout interval of the image signal is set to 10 ms and the interval of 1 ms, and the image signal is read out twice. When the image signal read out at the interval of 10 ms is in a saturated state, this image signal is not output. The image signal read out at an interval of 1 ms is multiplied by 10 and output as an output.
[0047]
By outputting the image signal in this way, the image signal level is increased due to the large amount of irradiated radiation, and the image signal level is limited by the saturation characteristics of the photoelectric conversion unit or the readout circuit. However, since the image signal read at an interval of 1 ms can be multiplied by 10 to obtain an image signal of a level which should be originally obtained, the maximum level of the image signal can be improved and the dynamic range can be sufficiently secured. it can.
[0048]
That is, as shown in FIG. 4, regarding the image signals S1 and S2 whose storage intervals obtained by changing the readout interval are 10 ms and 1 ms, for the area A portion of the image signal S1, the power storage of the photoelectric conversion unit Since the capacity is not saturated, this image signal S1 is output as it is. However, since the storage capacity of the image signal S1 is saturated in the area B, the image signal S2 is multiplied by 10 and weighted so that the signals in both the A and B areas have linearity. Output. By thus multiplying the image signal S2 by 10 and weighting and outputting the signals in both the A and B regions so as to have linearity, even if the image signal S2 is saturated, the figure As shown in FIG. 4, the dynamic range can be improved by one digit.
[0049]
Next, a third embodiment of the present invention will be described.
[0050]
FIG. 5 is a diagram showing an image signal reading system using a radiation detector for carrying out a third embodiment of the image signal reading method according to the present invention. In FIG. 5, portions having the same configuration as that of the image signal reading system shown in FIG. 1 are indicated by adding "'" to the reference numerals, and detailed description thereof will be omitted.
[0051]
As shown in FIG. 5, in the third embodiment of the image signal reading method according to the present invention, the subject 6 'is irradiated with the X-rays 5' a plurality of times at predetermined intervals, and synchronized with the irradiation of the X-rays 5 ', A synchronizing means 9 for reading out the image signal S from the transfer section 19 of the solid-state photodetector 2 shown in FIG. 1 is provided.
[0052]
That is, X-rays 5 'from the X-ray source 4' are repeatedly emitted in a pulsed manner at predetermined intervals, and during irradiation of the X-rays 5 ', the solid-state photodetector 2 constituting the radiation detector 1' No pulse is generated from the scanning pulse generator 21 in the position ′, whereby an image signal having an intensity corresponding to the incident X-ray amount is stored in the transfer unit 19 of the solid-state photodetector 23. Next, while the irradiation of the X-rays 5 is stopped, a signal is sent from the synchronization means 9 to the scanning pulse generator 21 of the solid-state photodetector 2 ′, so that each solid-state photodetector 23 receives a pulse from the scanning pulse generator 21. Is transmitted, whereby the image signal S stored in each solid-state light detecting element 23 is read. Then, the read image signal S is input to the image processing means 7 ′ and added for each solid-state light detecting element 23, and the added image signal S ′ is input to the reproducing means 8 and becomes a visible image. Will be played.
[0053]
As described above, the image signal S is read out in synchronization with the X-ray 5 ′ transmitted through the subject 6 ′, and the image signal S is added for each solid-state light detecting element 23, thereby transferring the solid-state light detecting element 23. An image signal S in an amount exceeding the storage capacity of the unit 19 can be obtained, and the added image signal S has a wide dynamic range. Therefore, if the added image signal S is reproduced, a high-quality image with a secured dynamic range can be obtained.
[0054]
In addition, as the X-ray source used in the third embodiment of the present invention, a flash X-ray source (see '93 Spring Preliminary Preliminary Proceedings 31aZK-9, 10) can be used.
[0055]
Further, in the above-described embodiment, a radiation detector composed of a combination of a scintillator and a solid-state photodetector is used. However, the radiation detector is not particularly limited thereto. And the like, a radiation detector of a type that directly detects radiation without passing through a scintillator, converts the radiation into an image signal, and outputs the image signal may be used.
[0056]
In the above-described embodiment, the resin sheet is used as the substrate of the solid-state photodetector. However, the present invention is not limited to this. An inorganic material such as glass may be used.
[0057]
Further, in the above-described embodiment, the amorphous silicon layer is used as the semiconductor layer. However, the present invention is not limited to this, and any semiconductor layer may be used.
[0058]
In the first and second embodiments described above, the image signal reading method according to the present invention is used to obtain a radiation image of a subject by detecting radiation irradiated through the subject. However, the present invention is not limited to this, and can be applied to, for example, so-called autoradiography in which a radiation image of a subject is detected by detecting radiation emitted from the subject itself.
[0059]
【The invention's effect】
As described in detail above, the image signal readout method according to the present invention reads the image signal a plurality of times while the radiation detector is irradiated with the radiation carrying image information, or changes the readout interval to change the readout interval. If one image signal is different from another image signal and another image signal is saturated, the other image signals are weighted and output at a predetermined ratio. Irradiation is performed at intervals and an image signal is read out in synchronization with the predetermined interval. Therefore, an image signal having a dynamic range exceeding the saturation characteristic of the solid-state photodetector can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing details of a radiation detector for implementing an image signal reading method according to the present invention.
FIG. 2 is a cross-sectional view illustrating details of a radiation detector.
FIG. 3 is a diagram showing an image signal reading system using a radiation detector for carrying out the first embodiment of the image signal reading method according to the present invention;
FIG. 4 is a diagram showing an image signal read by a second embodiment of the image signal reading method according to the present invention;
FIG. 5 is a diagram showing an image signal readout system using a radiation detector for implementing a third embodiment of the image signal readout method according to the present invention;
[Explanation of symbols]
1,1 'radiation detector
2,2 'solid state photodetector
3,3 'scintillator
4,4 'X-ray source
5,5 'X-ray
6,6 'subject
7, 7 'information processing means
8, 8 'regenerating means
9 Synchronization means
11 Substrate
13 Amorphous silicon layer
18 Photoelectric conversion unit
19 Transfer section
23 Solid-state photodetector
S, S 'image signal

Claims (6)

The image signal is converted from a radiation detector comprising a large number of solid-state photodetectors arranged two-dimensionally, which detects radiation carrying image information, converts it into an image signal carrying the image information as a whole, and stores it. In an image signal reading method for reading,
While the radiation is being detected by the radiation detector, at a readout interval shorter than the time at which the stored image signal is saturated , all image signals stored in the solid-state light detection element are read out for each readout. An image signal reading method, wherein the image signal is read a plurality of times while reading, and the read plurality of image signals are added and output for each of the solid-state photodetectors. A radiation detector comprising a plurality of two-dimensionally arranged solid-state light detecting elements for detecting radiation emitted through a subject, converting the radiation into an image signal carrying a radiation image of the subject as a whole, and accumulating the signal. An image signal reading method for reading the image signal from
The radiation was irradiated a plurality of times at predetermined intervals to said subject at said stored as image signal read shorter than the time to saturation time, the solid state light detecting element in synchronism with each reading to the irradiation of the radiation Reading out the image signal a plurality of times while reading out all the stored image signals , and adding and outputting the plurality of read-out image signals for each of the solid-state photodetectors; Read method. 4. The image signal readout according to claim 2, wherein the radiation detector includes a transfer unit for reading out the stored image signal, and the transfer unit reads out the image signal a plurality of times. Method. The image signal is converted from a radiation detector comprising a large number of solid-state photodetectors arranged two-dimensionally, which detects radiation carrying image information, converts it into an image signal carrying the image information as a whole, and stores it. In an image signal reading device for reading,
While the radiation is being detected by the radiation detector, at a readout interval shorter than the time at which the stored image signal is saturated , all image signals stored in the solid-state light detection element are read out for each readout. Control means for reading the image signal a plurality of times while reading,
An image signal reading device comprising: adding means for adding the plurality of read image signals to each of the solid-state light detection elements and outputting the added signals. A radiation detector comprising a plurality of two-dimensionally arranged solid-state light detecting elements for detecting radiation emitted through a subject, converting the radiation into an image signal carrying a radiation image of the subject as a whole, and accumulating the signal. An image signal reading device for reading the image signal from
The radiation was irradiated a plurality of times at predetermined intervals to said subject at said stored as image signal read shorter than the time to saturation time, the solid state light detecting element in synchronism with each reading to the irradiation of the radiation Control means for reading out the image signal a plurality of times while reading out all the stored image signals ,
An image signal reading device comprising: adding means for adding the plurality of read image signals to each of the solid-state light detection elements and outputting the added signals. 6. The image signal reading device according to claim 4, wherein the radiation detector includes a transfer unit for reading the stored image signal.

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