JPS63131134A - Radiation image information recorder reader - Google Patents

Abstract

PURPOSE:To correctly read image information on a subject even if there is variance in dosage by eliminating the output variation of a photoelectric reading means with a signal from a storage means for storing characteristics of shading due to the dosage variance of a radiation source, and correcting an image signal. CONSTITUTION:Plural storage type fluorescent body sheets 30 are conveyed along a specific circulation passage 26 and radiation image information on a subject 43 is recorded on or read out of the sheets. At this time, the sheets 30 are irradiated with radiation 47 while the subject 43 is not positioned at an image recording part 40 before recording and reading. Thus, an image is read out of a sheet 30 after the exposure all over and stimulated phosphorescent light corresponding to the variance in dosage is detected by a photomultiplier 57, so that its characteristics are stored in a memory 66. Then when radiation image information which is stored and recorded on the sheet 30 is read out under set photographic condition Q, a signal indicating characteristics from the memory 66 is sent to a correcting circuit 62 to correct the image signal.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention accumulates and records radiation image information on a stimulable phosphor sheet, then irradiates it with excitation light, and responds to the N product recorded image information. It relates to a radiation image information recording/reading device that detects photostimulated light, reads image information, and converts it into an electrical signal, and more specifically, a radiation image information recording and reading device that uses a stimulable phosphor sheet to be circulated and reused within the device. The present invention relates to an information recording/reading device.

(Prior art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, electron beams, etc.), part of the energy of this radiation is accumulated in the phosphor. Then, when the phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. Phosphors that exhibit these properties are called stimulable phosphors (stimulable phosphors).

Using this M-product phosphor, radiation image information of a subject such as a human body is recorded on a stimulable phosphor sheet (hereinafter referred to as a stimulable phosphor sheet), which is then scanned with excitation light. A method has been proposed in which the stimulated luminescence is generated, the stimulated luminescence is read photoelectrically to obtain an image signal, and the image signal is processed to obtain a radiation image of a subject that is suitable for diagnosis (for example, Japanese Patent Laid-Open No. 55 -12429, No. 55-116340, No. 55-163472, No. 56-11395, No. 56-1046451, etc.). This final image can be reproduced as a hard copy or on a CRT. In any case, in such a radiation image information recording and reproducing method, the stimulable phosphor sheet does not ultimately record image information, but temporarily stores image information in order to provide an image to the final recording medium as described above. Therefore, this stimulable phosphor sheet may be used repeatedly, and such repeated use is extremely economical.

Also, for example, when a mobile station such as an X-ray van is equipped with a radiation image information recording/reading device that uses a stimulable phosphor sheet, and the mobile station travels to various locations for group medical examinations to take X-ray images. It is inconvenient to stack multiple stimulable phosphor sheets, and there is a limit to the number of sheets that can be loaded onto a moving vehicle. Therefore, a stimulable phosphor sheet is made to be reusable and loaded onto a moving vehicle, radiation image information for each subject is recorded on it, and the image signal obtained by reading it is stored on a large storage capacity such as a magnetic tape. If the radiation images are copied onto a recording medium and the stimulable phosphor sheet or the like is circulated and reused, radiation images of a large number of objects can be taken using a mobile vehicle, which is extremely useful in practice. Furthermore, if continuous imaging is performed through this cyclical reuse, the imaging speed can be increased in mass medical examinations, which has an extremely large practical effect.

In order to reuse the stimulable phosphor sheet as described above, the radiation energy remaining in the stimulable phosphor sheet after the stimulated luminescence light has been read can be absorbed by, for example,
2@, No. 56-12599, the remaining radiation image may be erased by irradiating the sheet with light or heat, and the stimulable phosphor sheet may be used again for recording radiation images.

Therefore, the present applicant proposed a circulating conveyance means for conveying a stimulable phosphor sheet capable of storing and recording radiation images along a predetermined circulation path, and a means for irradiating the sheet with radiation through a subject in the circulation path. an image recording unit that accumulates and records radiation image information of the subject on this sheet;
An excitation light source is located in the circulation path and irradiates excitation light onto a sheet on which radiographic image information is accumulated and recorded in the image recording section, and an image signal is generated by reading stimulated luminescence light emitted from the sheet by the irradiation of the excitation light. a double-edge reading section consisting of a photoelectric reading means, located in the circulation path, and remaining on the sheet prior to recording an image on the sheet after the image reading is performed in the image reading section. We have previously proposed a radiation image information recording/reading device in which a stimulable phosphor sheet is repeatedly used by circulating the stimulable phosphor sheet between the various parts, and an erasing part that emits radiation energy. Showa 59-19224
No. 0). According to the radiographic image information recording/reading device having such a structure, radiographic image information can be recorded and read continuously and efficiently.

(Problems to be Solved by the Invention) By the way, in the above-mentioned radiation image information recording/reading device, radiation a is irradiated from a radiation source such as an Xa tube to a stimulable phosphor sheet when recording (photographing) radiation image information. It is difficult to make the suspension uniform over the entire irradiation surface, and a difference in dose occurs depending on the position of the irradiation surface. This radiation dose variation exists for each individual radiation source, and in the radiation image information recording/reading device described above, the position of the radiation source (distance from the subject) may be changed as appropriate; Even if a radiation source of 1
1 It varies depending on the position of the radiation source.

If there is such an affl variation, a portion of the object that has been irradiated with low IM radiation will be recorded with unduly low radiation energy on the stimulable phosphor sheet. Therefore, when reading radiation image information, the level of stimulated luminescence light from the above portion becomes unduly low, resulting in so-called shading (partial decrease in the amount of detected light). If such shading occurs at the edges, it will naturally become impossible to correctly read the radiation image information recorded on the stimulable phosphor sheet.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an 9AI image information recording/reading apparatus that can correctly read radiation image information of a subject even if there is variation in the line width of the radiation source.

(Means for Solving the Problems) The radiation image information recording/reading device of the present invention includes a circulating conveyance means for a stimulable phosphor sheet as described above, and an image recording device for accumulating and recording radiation image information on the sheet. an image reading section that irradiates the sheet with excitation light and reads the stimulant bonsai light emitted from the sheet with a photoelectric reading means; A radiation image information recording/reading device comprising: a storage means for storing shading characteristics due to line width variation of a radiation source; and a signal indicating the shading characteristics from the storage means; and a correction means for correcting the image signal so as to eliminate a change in the output of the photoelectric reading means caused by the change in the output of the photoelectric reading means.

(Function) When the above correction is performed, the emission of O
The component due to the line width variation of the A-ray source is removed, and this image signal correctly represents the radiation image of the subject.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a radiation image information recording/reading apparatus according to an embodiment of the present invention. Dare as illustrated! ) Inside the 1-line image information recording/reading device, there is an endless belt 1.2.
．． 3.4.5.6.7.8.9.10, guide rollers 11.12.13.14 that rotate following the endless belt 1.6.7.10, and guide plate 15.16.1.
7.18.19.20.21 and nip roller 22.2
Circulation passage 26 for sheet conveyance consisting of 3.24.25
A plurality of (in this example, five) stimulable phosphor sheets 30 are arranged at appropriate intervals in this circulation passage 26, and these stimulable phosphor sheets 30 The endless belts 1 to 10 as conveyance means and the nip rollers 22, 23, 24, and 25 circulate and convey the material in the direction of the arrow in the figure.

The endless belts 2.3 are configured to hold the stimulable phosphor sheet 30 vertically between them, and a photographing stage 41 is provided on the side of the endless belts 2.3 (left side in the figure). A radiation source 42, such as an X-ray tube, is provided at a position facing the endless belt 2.3 with the photographing table 41 in between. A recording section 40 is configured. In this example, the radiation source 42 is supported movably along a guide 44 so that the distance from the imaging table 41 can be changed, and is moved in this direction by a drive device 45. . Subject (subject)
43, the sheet 30 used for irradiation is held between the endless belts 2.3 as shown in the figure, and the radiation source is placed with the subject 43 positioned on the curved surface of the transport stage 41. 42 is activated. As a result, the transmitted radiation image of the subject 43 is projected onto the sheet 30, and the radiation image information of the subject 43 is stored and recorded on the sheet 30.

f] At the bottom right end position in the middle of the figure of the oil ring passage 26, there is an image reading unit 5.
0 is set. In this image reading section 50, a laser light source 51 is installed above the endless belt 8 that constitutes a part of the reading section 50, and output laser light 52 is directed onto the sheet 30 on the endless belt 8 in the width direction thereof. A mirror 53 and a galvanometer mirror 54 are provided for scanning.

By this reciprocating movement of the galvanometer mirror 54, the laser beam 52 is main-scanned over the sheet 30 on which the radiation image has been accumulated and recorded. Note that after a radiation image is recorded on the sheet 30 in the image recording section 40, the sheet circulation conveyance means is driven to convey this image to the reading section 50. At the scanning position of the laser beam 52 on the sheet 30, there is a condensing reflective mirror 55 and a condensing optical element 5 along the main scanning line.
6 is placed. Sheet 3 irradiated with laser light 52
The stimulated luminescence light emitted from the sheet 30 and directly proceeding to the condensing optical element 56 and the stimulated luminescence light emitted from the sheet 30 and reflected by the condensing reflecting mirror 55 are transmitted to the incident end surface 56A of the condensing optical element 56. The light enters the condensing optical element 56 and is guided through the condensing optical element 56 by total reflection to the exit end face 5 of the element 56.
The stimulated luminescence light is received by a photomultiplier 57 connected to 6B and read out photoelectrically. At the same time as the main scanning of the laser beam 52 is performed as described above, the sheet 30 is conveyed by the endless belt 8 in the direction of arrow A in the figure (V, that is, a direction substantially perpendicular to the main scanning direction) and is sub-scanned. The stored radiation image information is read two-dimensionally from the sheet 30. The image signal S read by the photomultiplier 57 is amplified by a log amplifier 60 and digitized by an A/D converter 61. The digital read image signal Sd obtained in this way is
The signal is sent to an image processing circuit 63 through a switch 69 and a correction circuit 62, which will be described later, where it undergoes processing such as gradation processing and frequency processing, and then is sent to a necessary reproducing device 64. As mentioned above, this playback device 64 may be a display such as a CRT, a recording device that performs optical scanning recording on a photosensitive film, or a device that is temporarily replaced with a storage device such as a magnetic tape for that purpose. It's okay.

The sheet 30 whose image has been read is conveyed along the guide plate 18 by the endless belt 9.10, and sent to the erasing section 70 through the nip roller 22, the kite plate 19, and the nip roller 23. The erasing unit 7o consists of a box 71 and a large number of erasing light sources 72 such as fluorescent lamps arranged inside the box 71. After the shutter 73 is opened, the sheet 30 is moved into the box by the nip roller 23. body 71
transported inside. When the sheet 30 is sent into the box 71, the shutter 73 is closed.

The erasing light source 72 inside the box 71 mainly emits light in the excitation wavelength range of the stimulable phosphor of the sheet 30, and the radiation energy remaining in the sheet 30 after reading the image e is transferred to the sheet 30. When such light is irradiated, it is emitted from the sheet 30. Note that since the shutter 73 is closed at this time, the erasing light does not leak and enter the image reading section 50 and generate noise in the read signal.

The sheet 30, on which the image (afterimage) has been erased to such an extent that the image information can be recorded again, is discharged from the erasing section 70 by rotating the nip roller 24. The discharged sheet 30 passes through the guide plate 20 and passes through the nip roller 2.
5, and then sent to the endless belt 1 along the guide plate 21 by the nip roller 25, and then sent to the image recording section 40 in the same manner as described above to be used for radiography.

Next, the correction of the image signal Sd by the correction circuit 62 will be explained. Radiation 47 irradiated from radiation source 42
There is the above-mentioned dose variation, and the dose distribution varies depending on the individual radiation source 42, and even in the same radiation source 42, it changes when its position is changed. This dose variation causes shading as described above, and as a result, the image of the subject 43 is incorrectly reproduced. The correction circuit 62 is provided to eliminate such problems.

Before recording and reading radiation image information as described above, one stimulable phosphor sheet 30 is placed in the recording section 40.
The sheet 30 is then irradiated with radiation 47 while the patient 43 is not positioned on the irradiation table 41. The stimulable phosphor sheet 30 subjected to so-called solid exposure in this way is
It is subjected to image reading in the same way as inscription. The stimulable phosphor sheet 30 scanned by the laser beam 52 emits stimulated luminescent light with an intensity corresponding to the dose variation of the radiation 47, and this stimulated luminescent light is photomultiplied via the condensing optical element 56. Detected by pliers 57. At this time, the reference output signal BS is output from the photomultiplier 57. is amplified by the log amplifier 60 and digitized by the A/D converter 61 in the same manner as described above. The digitized reference output signal Sdo is input to the correction value calculation circuit 65 via the switched switch 69. This correction value calculation circuit 65 operates on the condensing optical element 5
The difference between the reference output signals Sdo in the main scanning direction along the incident end surface 56A of No. 6 (this is caused by the shading and indicates the shading characteristics) is determined for each pixel.

That is, as shown in FIG.
r, Xz, Let it be the representative signal value Rn of the column. And correction value calculation circuit 6
5 is all the representative signal values R1, R2... in the column 1~
... Find the difference Un=Rn Ro between the average value Ro of Rj and each representative No. 13 value R0, and calculate these values Llt, Uz
N... Uj is sequentially stored in the memory 66 as a correction value.

In this example, "chest/overview imaging" [head gIS
The shooting condition QS such as /enlarged dynamic image J is inputted from the human power unit 67 to the device control circuit 68, and the device control circuit 68 generates a drive control signal according to the input shooting condition Q. D is output to drive the drive 8 position 45, and the radiation source 42 is set at the optimal position (for example, one of several positions) for each imaging condition. The calculation and storage of the above-mentioned correction values Ul, U2, . is stored in the memory 66.

When reading radiation image information stored and recorded on the stimulable phosphor sheet 30, the device control circuit 68 sends the imaging conditions Q regarding the stimulable phosphor sheet 30 to the correction circuit 62,
The correction circuit 62 corrects the correction value U1. corresponding to the photographing condition Q. Uz...Uj is read from the memory 66, and the correction values U1, Uz... are read from the read image signal Sd.
...Perform an operation to reduce Uj. At this time, the correction circuit 6
2 correction value (JI N Llz N...U
The timing of reading j is determined by the galvanometer mirror 54.
The correction value Un is controlled to be subtracted from the read image signal Sd for the pixel in the n-th column using a synchronization signal synchronized with the operation.

If the read image signal Sd is corrected by subtracting the correction value UO, the output change of the photomultiplier 57 due to the shading described above is compensated, and according to the corrected image signal Sd', the IW4 phosphor The radiation image information stored and recorded on the sheet 30 can be correctly reproduced. Note that in order to reduce the number of correction values stored in the memory 66, only correction values for discrete pixel columns (for example, odd-numbered pixel columns, etc.) are stored in one pixel column from X1 to Xj. Calculate and store in memory 66
5, and the correction values for the pixel rows between them are stored in the memory 6.
The correction value read from 6 may be interpolated to obtain the correction value.

Further, correction values Ul, Uz... are obtained from the reference output signal So.
...When calculating lJn, if it is difficult to calculate these correction values with high precision due to the influence of noise, etc., the correction value U is calculated from a signal obtained by smoothing the reference output signal S0.
1, Uz...lJn may be calculated.

Above, an example was explained in which the influence of radiation dose variation exists mainly in the main scanning direction of the excitation light. If such a correction value exists, it is sufficient to obtain the aforementioned correction value two-dimensionally for all pixels in each column and each row (or intermittently as described above), and to independently correct the image signal Sd for all pixels.

Furthermore, if the position of the radiation source 42 is fixed, the correction value U+
, (Jz...Uj need only be found for one set.

(Effects of the Invention) As explained above in detail, the radiation image information recording/reading device of the present invention eliminates the influence of shading due to dose variation of the radiation source, and improves the image quality of the subject recorded on the stimulable phosphor sheet. ! ) It becomes possible to read J-ray image information correctly, and it becomes possible to reproduce radiographic images with excellent diagnostic performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a radiation image information recording/reading apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining shading correction according to the present invention. 1-10...Endless belt 11-14...Guide roller 15-21...Guide plate 22-25...Nip roller 26...Circulation passage 30...Storable phosphor sheet i.40. ...Image recording section 42...Radiation source 44
... Guide 45 ... Drive device 47 ...
・Radiation 50... Image reading unit 62...
Correction circuit 65...Correction value calculation circuit 66...
・Memory 67...RF menu input section 68...Device control circuit 70...Erasing section 3d.
・Reading image signal

Claims (2)

[Claims] (1) Circulating transport means for transporting a plurality of stimulable phosphor sheets capable of accumulating and recording radiographic image information along a predetermined circulation path; in the circulation path, the sheets are irradiated with radiation from a radiation source through a subject; an image recording section that accumulates and records radiation image information of the subject on the sheet; and an excitation light source in the circulation path that irradiates excitation light onto the sheet on which the radiographic image information is accumulated and recorded in the image recording section. and a photoelectric reading means for reading the stimulated luminescence light emitted from the sheet by the excitation light irradiation to obtain an image signal, and in the circulation passage, the image reading unit performs image reading. In a radiation image information recording/reading device comprising an erasing section that releases radiation energy remaining on the sheet prior to image recording on the sheet after image recording, the characteristics of shading due to dose variations of the radiation source are A storage means for storing the characteristics, and a correction means for receiving a signal indicating the characteristic from the storage means and correcting the image signal so as to eliminate a change in the output of the photoelectric reading means due to the shading. Radiographic image information recording/reading device. (2) The storage means stores a plurality of the characteristics for each position of the radiation source that can be changed according to the imaging conditions, and the correction means receives the input of the imaging conditions and adjusts the input imaging conditions. 2. The radiation image information recording/reading apparatus according to claim 1, wherein the radiation image information recording/reading apparatus is configured to select the characteristic corresponding to the characteristic and perform the correction based on this characteristic.