JPS60120347A - Method and device for recording and reading radiation image information - Google Patents

Abstract

PURPOSE:To prevent deterioration in picture quality due to scattered rays which are scattered to the outside of an irradiation field by stopping down the readout area of previously read image information to within the irradiation field of radiation during the image recording of an accumulative fluorescent material sheet. CONSTITUTION:X-Ray image information on an object 102 is stored and recorded in an accumulative fluorescent material sheet 103 at a photographing part 1. Accelerated phosphorescence is generated from the accumulated fluorescent material sheet 103 at a pre-reading part 3 with laser light 302 from a laser light source 1, and detected by a photodetector 308. A pre-read controller 312 limits reading by the photodetector 308 to within the irradiation field of radiation during the recording of the accumulative fluorescent material sheet 103. Then, a main reading part 4 reads the accumulative fluorescent material sheet 103 by a photodetector 410 with laser light 402 from a laser light source 401, and read information is reproduced by a reproducing and recording part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention is directed to irradiating excitation light onto a stimulable phosphor sheet that accumulates and records radiation image information. The present invention relates to a radiation image information recording and reading method and apparatus for optically reading the obtained stimulated luminescence light using a photodetector.

(Technical background and prior art) Radiographic image information of a human body, etc. is recorded on a -H storage phosphor sheet, and this phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescence light. A radiation image information recording and reproducing system is known that photoelectrically reads the obtained stimulated luminescence light to obtain an image signal, and outputs it as a visible image to a recording material such as a photographic light-sensitive material, a CRT, etc. based on this surface edge signal. (
For example, JP-A No. 55-12429, JP-A No. 56-11395
No. 55-1631172, No. 55-116340
(disclosed in the issue, etc.). Among such systems, excitation light with an energy lower than that of the excitation light that should be irradiated during a reading operation (hereinafter referred to as "single reading") to obtain a visible image for observation and interpretation is used. Prior to the actual reading, a reading operation (hereinafter referred to as "pre-reading") is performed to understand the recorded A-1:A-line image information in advance, and based on the results of this pre-reading, the reading conditions and image processing conditions for the actual reading are performed. A system that sets
No. 8-67243, etc. ) is preferable because it provides a radiation image particularly suitable for observation and interpretation.

By the way, in the X IJI photographing device,
In order to control the ray irradiation range, an irradiation field diaphragm such as a collimator is sometimes provided near the X-ray source. This irradiation field aperture not only has the humane effect of preventing X-rays from being irradiated to areas unrelated to diagnosis, but also prevents X-rays from being scattered by objects located outside the area to be diagnosed or observed. It also serves to prevent scattered X-rays from entering the region to be diagnosed or observed and being recorded on the recording material, thereby reducing the contrast and image quality of the X-ray image in this region.

Using an irradiation field diaphragm in this way prevents the above-mentioned deterioration in image quality because the X-rays are irradiated only on the area of the subject that you want to photograph, but conversely, the irradiation field is narrowed down to be narrower than the size of the recording material. In some cases, scattered X-rays scattered by objects within the irradiation field are recorded at the outer edge of the recording material outside the irradiation field, and noise is likely to be formed. Particularly when a wide latitude recording material such as a stimulable phosphor sheet is used, the noise caused by this scattered X-ray becomes more noticeable than in conventional film/screen systems.

This noise not only spoils the appearance of the periphery of the final image, but also, in the above-mentioned system that performs pre-reading before main reading, if this noise is read during pre-reading, it may cause errors in setting the conditions for main reading. Otherwise, this could lead to serious problems such as providing biased information. This problem does not occur if a stimulable phosphor sheet matching the size of the irradiation field is selected and used each time an image is taken, but such an operation is cumbersome and impractical. Especially today
- One type of relatively large stimulable phosphor sheet 1-
A system has been developed that incorporates this to image and read any body part. (See Japanese Patent Application No. 57-84436.) In such a system, the size of the stimulable phosphor sheet is not changed every time an image is taken, so the above problem had to be solved by other means. .

(Object of the Invention) The object of the present invention is to solve the above-mentioned drawbacks of the conventional technology and to provide an excellent method and apparatus for recording and reading radiation image information that is not affected by noise caused by scattered radiation scattered in the irradiation field. be.

(Structure of the Invention) The radiation image information recording and reading method according to the present invention is characterized in that the reading area of image information in pre-reading is narrowed down to the irradiation field at the time of recording, and the radiation image information recording and reading apparatus according to the invention It is characterized by having a means for narrowing down the irradiation field.

(Effects of the Invention) According to the radiation image information recording and reading method and apparatus of the present invention, image information is transferred to the stimulable phosphor sheet 1 using an irradiation field aperture.
When recording in ..., the read area in pre-reading is narrowed down to the irradiation field, so noise components due to scattered rays recorded outside the irradiation field of the stimulable phosphor sheet are not read (therefore, the presence or absence of scattered rays is not detected). Regardless of the actual reading conditions or image processing conditions, it becomes possible to set appropriate main reading conditions or image processing conditions, and it becomes possible to obtain an excellent final image.In addition, by narrowing down the reading area, the reading time in pre-reading can be shortened or the reading It is possible to increase the density.Furthermore, because these effects are achieved, the troublesome operation of selecting a stimulable phosphor sheet according to the size of Horimanno every time it is photographed is unnecessary.Therefore, In particular, a significant improvement in image quality can be achieved in a system in which one kind of relatively large stimulable phosphor sheet is incorporated into the device for photographing and reading.

(Embodiment) Hereinafter, the present invention will be described in detail based on the drawings.

The drawing is a schematic diagram showing a radiation image information recording/reproducing system including a radiation image information recording/reading device according to a preferred embodiment of the present invention.

In the drawings, 1 is a photographing section, 3 is a pre-reading reading section, 4 is a main reading reading section, 5 is a reproduction/recording section, and 6 is an overall control section.

In the imaging unit 1, the X-rays irradiated from the X-ray source 101 to the subject 102 with the same number of beams are transmitted through an irradiation field aperture such as a collimator.
The irradiation field is narrowed down by 110, and after passing through the subject 102, it is absorbed by the stimulable phosphor sheet 103, and X-ray image information of the subject is accumulated and recorded in the stimulable phosphor sheet 103. The field aperture 110 is adjusted by a field aperture control device 115, and the stimulable phosphor sheet
An irradiation field 103A indicated by diagonal lines is formed on 103. Further, the irradiation field aperture control device 115 is an irradiation field aperture control device 11.
0 aperture size d, irradiation field aperture from the X-ray source 101 1
10 and the stimulable phosphor sheet 103, and when irradiating X-rays obliquely, the angle θ formed by the stimulable phosphor sheet 103 of the X-ray source 101 (more specifically, Angle formed by a line descending vertically from the focal point of the radiation source 101 and the line connecting the focal point and the center of the aperture of the irradiation field diaphragm)
Each piece of information is output to the overall control device 604. Here, the "size" of the aperture of the irradiation field diaphragm 110 is:
If the diaphragm aperture is circular, it represents the diameter, and if it is rectangular, it represents the length of the side or diagonal. Overall control device 604
calculates the size of the irradiation field 103A based on the information output from the irradiation field aperture control device 115. Here, the size D of the irradiation field is LD=- when taking images without tilting the X-ray source 101 with respect to the phosphor sheet 103.
When X-rays are irradiated obliquely, it is determined by .

Further, the calculation of the size D of the irradiation field 103A may be performed in the irradiation field aperture control device 115, and the result 8- may be outputted to the overall control device 6041\.

In this embodiment, the relative positional relationship between the X-ray source 101 and the stimulable phosphor sheet 103 is, for example,
Since the center of the stimulable phosphor sheet is fixed on the line passing through the center of 1, the irradiation field 1
Once the size of 03A is determined, the position of the irradiation field 103A on the stimulable phosphor sheet can be uniquely determined (that is, the size information includes position information). . On the other hand, if the relative positional relationship between the X-ray source 101 and the stimulable phosphor sheet is not constant, this positional relationship is detected in the imaging unit and the information is output to the pre-read control unit 312 via the overall control unit 604. Just shift it so that

This photographing section may be separate from the pre-reading section and the main reading section, or may be configured integrally with them.

In the pre-reading reading unit 3, a laser beam 302 emitted from a laser light source 301 passes through a filter 303 that cuts the wavelength range of stimulated luminescence light emitted from a stimulable phosphor sheet 103 by excitation of this laser beam 302. Thereafter, the light is one-dimensionally deflected and incident on the stimulable phosphor sheet 103 via a plane reflecting mirror 305 by a light deflector 304 such as a galvanometer mirror. On the other hand, the phosphor sheet 103 is conveyed in the direction of arrow 306 and sub-scanned.

The following operations are performed. That is, the look-ahead control device 31
2 is an irradiation field 103A inputted from the overall control device 604
The next signal determined based on the size information including the position information or the position and size information, that is, the on-off signal that drives the optical deflector driver 311 only while the irradiation field 103A is on the main scanning line, and the main The optical deflector driver 31 sends an amplitude signal that limits the scanning amplitude to the length in the width direction of the irradiation field.
Send to 1. When the irradiation field 103A is not on the main scanning line, the optical deflector is stopped at a position where it reflects the laser beam in a direction that does not hit the stimulable phosphor sheet, but when the drive ON signal is input, , scans the stimulable phosphor sheet 1- with the amplitude commanded by the amplitude signal, and terminates the scanning according to the drive off signal.

By doing so, only the inside of the irradiation field 103A is irradiated with the laser light. Note that in the above, the drive of the optical deflector driver 311 is controlled to narrow down the reading area in the sub-scanning direction to the irradiation field 103Δ, but instead of this, a shutter is provided in the optical path of the laser beam to narrow down the irradiation field. 103A
The shutter may be opened only while the image is on the main scanning line.

Power of laser light source 301 for pre-reading, laser light 302
The beam diameter of the laser beam 302, the scanning speed of the laser beam 302, and the transport speed of the phosphor sheet 103 are selected so that the energy of the laser beam 302 for pre-reading is smaller than that for main reading.

In the present invention, the energy of excitation light refers to the effective energy of excitation light received per unit area of the stimulable phosphor sheet.

In the present invention, the energy of the excitation light to be applied to the stimulable phosphor sheet during pre-reading is lower than the energy of the excitation light during main reading, as long as it is 11-. If the ratio between the excitation light energy of the pre-reading and that of the main reading is close to 1, the amount of radiation energy remaining and accumulated at the time of the near-excitation reading will be small; however, if this ratio is less than 1, the value of the reading gain should be It has been found that radiographic images suitable for observation and interpretation can be obtained by appropriately setting W4. However, in order to obtain radiographic images that are highly suitable for observation and interpretation, the stored radiographic image information stored in the stimulable phosphor by pre-reading must be used to select reading conditions or optimal image processing conditions. In other words, as long as the stimulated luminescence light emitted from the stimulable phosphor can be sufficiently detected in the above sense, the ratio of the energy of the excitation light in the pre-reading and the main reading is small. more desirably, 50% or less, preferably 10% or less,
More preferably, it is 3% or less. The lower limit of this ratio is determined by the accuracy of the pre-read stimulated luminescence light detection system.

Methods of making the energy smaller than the actual energy include reducing the output of the laser light source, increasing the beam diameter of the laser beam, increasing the scanning speed of the laser beam, and accumulative fireflies. Known methods such as increasing the transport speed of the light sheet can be used.

When the laser beam 302 is irradiated in this way, the stimulable phosphor sheet 103 emits stimulated luminescent light with an amount proportional to the accumulated and recorded X-ray energy, and this emitted light is transmitted to the pre-reading light guiding sheet. 307. The light guide sheet 307 has a linear incident surface and is placed adjacent to and opposite to the scanning line on the stimulable phosphor sheet 103, and has an annular exit surface and a photomultiplier or the like. It is brought into close contact with the light receiving surface of the photodetector 308. This light guiding sheet 307 is made by processing a transparent thermoplastic resin sheet such as acrylic resin, and is configured so that the light incident from the incident surface is transmitted to the exit surface while being totally reflected inside. The stimulated luminescent light from the stimulable phosphor sheet 103 is guided through the light guide sheet 307, exits from the exit surface, and is received by the photodetector 308. The preferred shape, material, etc. of the light guide sheet are disclosed in Japanese Patent Application Laid-open No. 55-87970.
No. 56-11397, etc.

A filter is attached to the light-receiving surface of the photodetector 308, which transmits only light in the wavelength range of stimulated luminescence light and cuts light in the wavelength range of excitation light, and detects only stimulated luminescence light. It's getting wet. The output of the photodetector 308 is sent to the amplifier 309
The signal is amplified and input to the control circuit 414 of the reading section 4 for main reading. The control circuit 414 sets the amplification factor setting value 81 recording scale factor setting value b according to the obtained accumulated recording information.
1 Output the playback image processing condition setting value C. The stimulable phosphor sheet 103 that has undergone pre-reading is transferred to the reading section 4 for main reading.

In the main reading reading unit 4, a main reading laser light source 40
The laser beam 402 emitted from 1 is this laser beam 402
After passing through a filter 403 that cuts the wavelength region of the stimulated luminescent light emitted from the stimulable phosphor sheet 103 by excitation of The light is deflected onto the stimulable phosphor sheet 103 by the light deflector 405 via the plane reflecting mirror 40G, and then enters the stimulable phosphor sheet 103. An fθ lens 4 is provided between the optical deflector 405 and the plane reflecting mirror 406.
07 is arranged, and a laser beam 40 passes over the phosphor sheet 103.
2 is configured to always have a uniform beam diameter even when the beam is scanned.

On the other hand, the phosphor sheet 103 is moved in the direction of arrow 408 to perform sub-scanning, and as a result, the phosphor sheet 1
Laser light is irradiated over the entire surface of 103. When the laser beam 402 is irradiated in this manner, the stimulable phosphor sheet 103 emits stimulated luminescent light with an amount proportional to the accumulated and recorded X-ray energy, and this emitted light is transmitted to the light guide sheet for main reading. 409. The main reading light guide sheet 409 has the same material and structure as the preread light guide sheet 1-307. Light guide sheet for book reading 4
The stimulated luminescence light guided through the photodetector 410 while repeating total reflection is emitted from the exit surface and is received by the photodetector 410. A filter that selectively transmits only the wavelength range of the stimulated luminescence light is attached to the light receiving surface of the photodetector 410, so that the photodetector 410 detects only the stimulated luminescence light. .

15 Single reading may be performed over the entire surface of the stimulable phosphor sheet, but preferably only the inside of the irradiation field is set as the reading area by the same method and means as the pre-reading described above, or by using a signal from the overall control unit 604. Information regarding the irradiation field (that is, information on the size of the irradiation field including position information, or information on the position and size of the irradiation field) is output to the processing circuit 413, and based on this information, signal processing is performed on image data only within the irradiation field. do. By taking these measures, it is possible to shorten the reading time for main reading, the image processing time, or both, and if the former method is adopted, the time required for actual reading can be reduced depending on the characteristics of the image recorded within the irradiation field. By increasing the reading density,
An image signal that can achieve better image quality can be obtained in the same or shorter time than scanning the entire sheet.

In the present invention, the S/N is that the wavelength range of the excitation light for pre-reading and main reading does not overlap with the wavelength range of the stimulated luminescence light.
It is preferable to select the excitation light source and the stimulable fluorophore to satisfy such a relationship. Specifically, as disclosed in JP-A No. 551242.9, it is preferable that the excitation light wavelength is 600 to 700 nm and the stimulated emission light wavelength is 300 to 500 nm. .

In this way, it emits stimulated luminescence light of 300 to 500 nm,
Examples of stimulable phosphors that can be preferably used in the present invention include rare earth element-activated alkaline earth metal fluorohalide phosphors (specifically, JP-A No. 55-12143
(Bat -xy.

MOx, Cay) FX: aEu” (where X is at least one of ci and Br, and X and y are Q<
x+y≦0.6×y≠0, and a is 10-6≦a
≦5 X 1'0" (there is a problem), JP-A-55-1214
It is described in Publication No. 5 (Ba 1-x, M” x
)FX:yA (However, MTl is M(1, Ca, Sr
, Zn and Cd, X is C
at least one of I, Br and I, A is ELI
.

Tb4Ce, Tm, Dy, Pr, No, Nd1Y [at least one of I and Er, × is 0≦×≦0.6
, y is 0≦y≦0.2), etc.]; JP-A-55-12
ZnS:Cu described in Japanese Patent No. 142.

Pb, Ba O・X Ajl! , 203: EU
(However, 0.8≦X≦1.0) and MTiO x Si
02:A (However, Mゝ is Mg, Ca5SrXZn,
Cd or Ba, A is Ce, Tb, EL
I, Ti1l% Pb, TL, Bi or M
r+ and X is 0.5≦x≦2.5); and LnOX described in JP-A-55-12144
:xA (where 1-11 is at least one of La, Y, Gd and lu, X is at least one of CL and Br, A is at least one of Ce and Tb, x is Q <x<0.1); and the like. Among these, rare earth element-activated alkaline earth metal fluorohalide phosphors are preferred, and among these, barium fluorohalides shown as specific examples are particularly preferred because of their excellent stimulable luminescence.

Furthermore, barium fluorohalide phosphor was developed in Japanese Unexamined Patent Publication No. 56
-2385 Publication, 56-2386 Publication to which metal fluoride is added, or Japanese Patent Application No. 1984-
The addition of at least one of a metal chloride, a metal bromide, and a metal iodide as disclosed in No. 150873 is preferable because the stimulated luminescence is further improved.

Further, as disclosed in Japanese Patent Application Laid-Open No. 55-163500, when the phosphor layer of a stimulable phosphor plate prepared using the above-mentioned stimulable phosphor is colored with a pigment or dye,
This is preferable because the sharpness of the finally obtained image is improved.

By this reading, the stimulated luminescence light detected by the photodetector 410 is converted into an electrical signal, and after being amplified to an electrical signal of an appropriate level by the amplifier 411 whose sensitivity is set by the amplification factor setting value a, the A/D It is input to converter 412 . The A/D converter 412 converts the digital signal into a digital signal with a scale factor suitable for the signal fluctuation width according to the recording scale factor setting value, and inputs the digital signal to the signal processing circuit 413. In the signal processing circuit, signal processing is performed based on the reproduction image processing condition setting value C so as to obtain an X-ray image excellent in suitability for observation and interpretation, and the signal is transmitted to the reproduction recording section and input to the optical modulator 501.

19- In the reproducing/recording section 5, a laser beam 503 from a recording laser light source 502 is modulated by an optical modulator 501 based on an image signal, and scanned by a scanning mirror 504 on a photosensitive material 505 such as a photographic film. . At this time, since the photosensitive material 505 is transported in a direction perpendicular to the scanning direction (arrow 506) in synchronization with scanning, the photosensitive material 505
An X-ray image is output on 05.

Here, a light modulator control device 507 is provided, and image information is provided to form an image recording area 505A on the photosensitive material 505 corresponding to the irradiation field 103A in the phosphor sheet 103 calculated by the overall control device 604. By outputting and displaying only the image inside the irradiation field, a clearer final image can be obtained.

The overall control unit 6 includes the overall control device 604 and the console 6.
03, and as described above, not only can the size or both the size and position of the irradiation field 103Δ in the phosphor sheet 103 including the position information be calculated, but also the pre-reading density, speed, etc. can be set.

201 It goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made.

For example, as described in Japanese Patent Application Laid-Open No. 58-89244, a desensitizing section may be provided between the photographing section and the pre-reading section.

Alternatively, as in JP-A No. 58-67243, the pre-reading and main reading may use a common reading unit, and a single reading device may be used to perform the pre-reading and main reading by changing the scanning conditions of the excitation light, etc. .

Furthermore, the laser light source serving as the excitation light source in the pre-reading reading section and the main reading reading section can be replaced with an LED array having a wavelength range different from that of the stimulated emission light, thereby omitting the optical deflector.

Further, the photodetector is not limited to a single one with a light-guiding sheet, but may be one in which a plurality of photomultiples or phototransistors are arranged in a straight line in the main scanning direction, for example.

The recording method in the recording unit 5 is not limited to the direct recording method using a laser light source, but also a method of displaying on a CRT, video printer, etc., for example, can be used.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a schematic diagram of an X-ray image information recording system including an X-ray image information reading device that is an embodiment of the present invention. 1...... Photography Department 101...
・X-ray source 102...Subject +03...Stormative phosphor sheet 103△...
Radiation irradiation field 110...Irradiation field aperture 115.
... Irradiation field aperture control i device 3 ... Read-ahead reading section 301 ... Laser light source for look-ahead 302 ...
...Laser light 303...Filter 304.
.....Light deflector 305 .....Flat reflecting mirror 3
0G... Transfer direction 307... Light guiding sheet for pre-reading 308...
...Photodetector 309...Amplifier 311
...... Optical deflector driver 312 for prereading...
...Pre-reading control device 4...Reading section 401 for main reading...Laser light source 402 for main reading...
...Laser light 403...Filter 404...
...Beam expander 405...Light deflector 406...Flat reflecting mirror 407...
・・fθ lens 408・・Transfer direction 409・
...Light guide sheet for book reading 410...Photodetector 411...Amplifier 412...
A/D converter 413...Signal processing circuit 414
......Control circuit 5......Reproduction recording section 501...
Light modulator 502...Recording laser light source 503...Laser light 504...Scanning mirror 505...Photosensitive material 505△...Image recording area 507 ...... Optical modulator control device 6 ...... Overall control section 603 ...
Console 604...Overall system @device

Claims (1)

[Claims] 1) Radiation image information is accumulated and recorded on a stimulable phosphor sheet by applying an irradiation field aperture, and the stimulable phosphor sheet is irradiated with excitation light. Prior to actual reading, the radiation image information stored and recorded in the excitation light is stimulated to emit light, and the resulting stimulated light is optically read to obtain image information for observation and interpretation. In a radiation image information recording and reading method that performs pre-reading of reading image information stored and recorded on the stimulable phosphor sheet using excitation light of the stimulable phosphor sheet, the image information reading area in the pre-reading is A radiation image information recording and reading method characterized by focusing on a radiation irradiation field during image recording. 2) A radiographic image emitted from the sheet by irradiating excitation light onto an imaging unit having an irradiation field aperture and the stimulable phosphor sheets 1 to 1 for accumulating and recording radiation image information on the stimulable phosphor sheet. In a radiation image information recording/reading device that has a reading section that photoelectrically reads stimulated luminescence light carrying information to obtain an image signal, prior to the actual reading, excitation light with an energy lower than that of the excitation light for the actual reading is used. It has a means for pre-reading, and means for narrowing down the reading area in the pre-reading to within the irradiation field based on information regarding the radiation irradiation field at the time of image recording on the stimulable phosphor sheet in the imaging section. A radiation image information recording/reading device characterized by: