JPH0378700A - Accumulative phosphorescent sheet, and reading method for information record of radiation image - Google Patents

Abstract

PURPOSE:To make stimulated radiation occur highly efficiently by making a phosphorescent body which radiates, when irradiated by a light of wave length lambda1, a phosphorescence of wave length lambda2 (lambda1 not equal to lambda2) that stays within a wave length region of stimulating waves of an accumulative phosphorescent body, contained in a form of layer which faces to a layer of the accumulative phosphorescent body. CONSTITUTION:An accumulative phosphorescent body sheet 10 consists of a layered binder 10B fixed on a carrier body sheet 10A and, in this binder 10B, the accumulative phosphorescent body 10C and a phosphorescent body 10D are dispersed. An output S1 of a photomultiplier 17 which shows light value of a stimulated phosphorescence 15, is fed to a read-out circuit 20 to be treated with amplifying, logarithmic conversion and so on. Also, this output S1 is treated with integration for every specific time interval, based on signals S2 synchro nized with scanning of a laser beam 13, say, treated with digitization by an A/D converter 21, for instance, and thereafter is treated with tone adjustment and then is fed to an image restoration device 23 to be used for restoration of a radiation image.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a stimulable phosphor sheet for storing and recording radiographic image information, and more particularly, the present invention relates to a stimulable phosphor sheet that stores and records radiographic image information, and more particularly, to a stimulable phosphor sheet that stores radiation image information. This invention relates to a stimulable phosphor sheet that allows use of outside light as reading light.

The present invention also relates to a method of recording radiation image information using the above-mentioned stimulable phosphor sheet and reading the recorded radiation image information.

(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. A phosphor exhibiting such properties is called a stimulable phosphor (stimulable phosphor).

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded on a sheet with a stimulable phosphor layer (hereinafter referred to as a stimulable phosphor sheet), which is then scanned with excitation light. A method has been proposed in which the stimulated luminescent light is photoelectrically read to obtain an image signal, and the image signal is processed to obtain a radiation image of the subject with good diagnostic suitability (for example, in Japanese Patent Laid-Open No. No. 55-12429, No. 55-11
No. 8340, No. 55-163472, No. 58-113
No. 95, No. 58-104845, etc.).

(Problem to be Solved by the Invention) The excitation light wavelength at which the stimulated luminescence efficiency of the stimulable phosphor is maximum (hereinafter referred to as the excitation peak wavelength) is unique to each stimulable phosphor. In order to increase the exhaustion efficiency,
It is necessary to use light with a wavelength close to this excitation peak wavelength as excitation light.

Therefore, in the past, the excitation light source was selected according to the excitation peak wavelength of the stimulable phosphor sheet used. This has caused a problem in that it cannot be used as an excitation light source.

On the other hand, even if a stimulable phosphor exists that is desirable in terms of its stimulated emission light spectrum, etc., it is not possible to obtain an appropriate excitation light source that matches its excitation peak wavelength. Another problem was that it could not be used to form phosphor sheets.

The present invention has been made in view of the above-mentioned circumstances, and provides a stimulable phosphor that can efficiently produce stimulated luminescence even when light with a wavelength deviating from the excitation peak wavelength of the stimulable phosphor is used as reading light. The purpose is to provide a phosphor sheet.

Another object of the present invention is to provide a method that can actually efficiently record and read radiation image information using such a stimulable phosphor sheet.

(Means for Solving the Problems) A first stimulable phosphor sheet according to the present invention is a stimulable phosphor sheet having a stimulable phosphor layer as described above, which receives light at a wavelength of λ. A phosphor that emits fluorescence at a wavelength λ2 (λl≠λ2) included in the excitation wavelength region of the stimulable phosphor is included in a layer facing the layer of the stimulable phosphor. .

Further, a second stimulable phosphor sheet according to the present invention is a stimulable phosphor sheet having a layer of stimulable phosphor in the same manner as described above, and after being photoexcited, the stimulable phosphor sheet receives light of wavelength λ1' to The wavelength λ2゛ (λ1
′≠λ2°) is contained in a layer facing the stimulable phosphor layer.

In order to include the phosphor that emits fluorescence at the wavelength λ2 or the phosphor that emits stimulated light at the wavelength λ2' in the stimulable phosphor sheet in a layer facing the stimulable phosphor layer, for example, The phosphor may be dispersed in a binder that holds the phosphor on the sheet-like support, or the phosphor layer may be formed separately in close proximity or close contact with the stimulable phosphor layer. .

On the other hand, a first radiation image information recording and reading method according to the present invention includes: irradiating the first stimulable phosphor sheet with radiation having image information; The stimulable luminescent light emitted by the stimulable phosphor is detected by a photodetector upon receiving the emitted fluorescence with the wavelength λ2 as excitation light, and an electrical image signal carrying the image information is generated. It is characterized by obtaining.

Further, a second radiation image information recording and reading method according to the present invention includes the steps of: optically exciting the second stimulable phosphor sheet described above, then irradiating the stimulable phosphor sheet with radiation having image information, and then subsequently accumulating the stimulable phosphor sheet. The stimulable phosphor sheet is irradiated with light of the wavelength λl, and the stimulated luminescence light emitted by the stimulable phosphor is detected by a photodetector upon receiving the stimulated light of the wavelength λ2' emitted at this time as excitation light. The present invention is characterized in that an electrical image signal carrying the above-mentioned image information is obtained.

(Function) As described above, in the radiation image information recording and reading method of the present invention, the light with the wavelength λ1 or λ1' is irradiated onto the stimulable phosphor sheet as the reading light, and the resulting light with the wavelength λ2 or λ2' is emitted. Since the stimulable phosphor is excited with For example, efficient stimulated luminescence is possible.

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

FIG. 1 schematically shows a stimulable phosphor sheet 10 according to the present invention. This stimulable phosphor sheet 10 is
A binder 10B is fixed in a layered manner on a sheet-like support 10A, and a stimulable phosphor 10C and a phosphor 10D are dispersed in the binder IOB.

In the first embodiment of the present invention, the stimulable phosphor 10c has the general formula % disclosed in JP-A-81-72089: (where Ml is Ll, Na, Rb, and C8. It is at least one selected alkali metal and contains at least either Rb or Cs.

Ml is Be, Mg, Ca, Sr, Ba, Zn, Cd, C
Ml is at least one divalent metal selected from u and N1, and Ml is Sc, Y, La, and Ce.

Pr, Nd, Pm, SII, Eu, Gd, Tb, Dy,
Ho, Er, Tm, Yb, Lu, Af! , Ga and I
at least one trivalent metal selected from n, x,
x' and X' are at least one kind of halogen selected from F, Cf), Br and I, and A is Tf
! , Na, Ag, and Cu. Also, a is a numerical value in the range of 0≦a≦1, and b is O
A numerical value in the range of ≦b≦0.5, and C is 0<c≦0.2
is a numerical value in the range of . ), Cs I ・0.05Ba F2 ” 0.01A
J! F3: 0.002Na phosphor is used. The photostimulated excitation spectrum and stimulated emission spectrum of this stimulable phosphor 10c are shown in FIG. 2 and 3, respectively. on the other hand,
In this example, the phosphor 10D is 7 AJF3.
:Fe'+phosphor is used. This phosphor 10
The excitation spectrum of D is shown in Figure 4, and the emission spectrum is shown in Figure 5.
As shown in the figure.

Next, recording (imaging) of radiation image information on the stimulable phosphor sheet 10 having the above configuration will be explained with reference to FIG. 6. The stimulable phosphor sheet IO is arranged to face a radiation source 5 such as an X-ray tube, and a subject 6 is arranged between them. When the radiation source 5 is driven in this state, the stimulable phosphor sheet 10 is irradiated with radiation 7 that is emitted from the source and transmitted through the subject 6 . Thereby, the energy of this radiation 7 is transferred to the stimulable phosphor 10 of the sheet 10.
C, and transmitted radiation image information of the subject 6 is recorded on the sheet 10.

The radiation image information accumulated and recorded on the stimulable phosphor sheet 10 as described above is read by the apparatus shown in FIG. This reading process will be explained below.

The stimulable phosphor sheet 10 is conveyed in the direction of arrow Y for sub-scanning with the reading light by a sheet conveying means 11 such as an endless belt. Further, a laser beam 13 as a reading light emitted from a laser light source 12 is deflected by an optical deflector 14 such as a galvanometer mirror, and main-scans the stimulable phosphor sheet 10 in a direction X substantially perpendicular to the sub-scanning direction Y. do. In this example, the laser light source 12 has a wavelength of λ1 m
B He-N emits a laser beam 13 of 32.8 nm
An e-laser is used.

As is clear from the above-mentioned FIG. 4, the stimulable phosphor sheet I
O's 7-AI! F3: Fe'+phosphor 10D emits laser beam 1 with the wavelength λ1 mB52.8 nm above.
3, and mainly at wavelength λz = 730
It emits fluorescence of 50 nm (see Figure 1). This wavelength λ
22-730n is the stimulable phosphor 10C shown in FIG.
This is close to the excitation peak wavelength of . Therefore, the stimulable phosphor IOC is efficiently excited by this fluorescence 50 and emits stimulated luminescence light 15 mainly having a wavelength of about 400 nm.

Stimulated luminescence light 15 is emitted from the portion of the stimulable phosphor sheet 10 irradiated with the laser beam 13 in an amount corresponding to the radiation image information stored and recorded. This stimulated luminescence light 15 is detected by a long photomultiplier tube 17, which is shown in detail in, for example, Japanese Unexamined Patent Publication No. 16668/1983. The output S1 of the photomultiplier tube 17 indicating the amount of stimulated luminescence light 15 is input to the reading circuit 20, where it is amplified and
It undergoes processing such as logarithmic transformation.

Further, this output S1 is subjected to integral processing at predetermined period intervals based on a synchronization signal S2 synchronized with the scanning of the laser beam 13,
As a result, the reading circuit 20 outputs a pixel-divided time-series analog read image signal S3. This read image signal S3 is digitized by, for example, an iD converter 2), and then subjected to signal processing (image processing) such as gradation processing and frequency processing in an image processing circuit 22 before being transferred to a CRT.
, is input to an image reproducing device 23 such as a printer, and is used to reproduce the radiation image recorded on the stimulable phosphor sheet 10.

The main body 17A of the elongated photomultiplier tube 17 has a cylindrical shape, and the inside thereof is in a vacuum state. This main body 17A
On the light-receiving surface of the stimulable phosphor sheet 10, there is a transparent adapter 17D that allows the stimulated luminescence light 15 to pass through it well, while at the same time transmitting the laser beam 13 and fluorescent light 5 reflected on the stimulable phosphor sheet 10.
0 is attached with a filter 17B for cutting, and furthermore, a light guide 17c made of glass or the like is attached on top of this filter 17B. The photomultiplier tube 17 is arranged so that the elongated outer end surface 17m of the light guide 17G is close to the laser beam scanning line (main scanning line) on the stimulable phosphor sheet 10 and extends along the scanning line. has been done.

As can be seen from FIG. 2, if the sheet 10 contains only the stimulable phosphor 10C as the phosphor, the wavelength 6
When the sheet 10 is scanned with a laser beam 13 of 32.8 nm, the stimulated luminescence efficiency becomes extremely low. On the other hand, according to the stimulable phosphor sheet 10 of this embodiment that includes the phosphor 10D, the laser beam 13 with a wavelength of 632.8 nm is produced even though the same stimulable phosphor 10C is used.
can be used as a reading light.

Next, a stimulable phosphor sheet according to a second embodiment of the present invention will be described. The stimulable phosphor sheet of this second embodiment has the general formula M' disclosed in JP-A-62-209187 as the stimulable phosphor 10C in the stimulable phosphor sheet 10 shown in FIG. Xea M”
' :b TJ2 (However, Ml is at least one kind of alkali metal selected from Na, Rh, and Cs, and Mll is Mg, Ca, Sr, Ba, Zn, Cd,
It is at least one kind of divalent metal selected from CU and N1, and X and X' are at least one kind of halogen selected from F, CJI, Br, and engineering. Also a
is a numerical value in the range of 0≦a≦460, and b is o<b≦0
．． It is a numerical value in the range of 2. ) is one of the stimulable phosphors shown in Rb Br ・0.5 Ba FBr : 0.001
Tf! A phosphor is used, and the same γ-A, 9F3:Fe3+ phosphor as in the first embodiment is used as the phosphor 10D. Above Rb Br ・0.5 B
The stimulated excitation spectrum and stimulated emission spectrum of the aFBr:0.0OIT1 phosphor are shown in FIG. 9 and FIG. 10, respectively.

The stimulable phosphor sheath) 10 of this second embodiment also has a wavelength λ1.
It is possible to read radiographic image information by the apparatus shown in FIG. 8, which uses a -632.8 nm laser beam 13 as a reading light. That is, in this case as well, the phosphor 10D receives the laser beam 13 and emits the wavelength λz = 7.
The stimulable phosphor 10 emits fluorescence 50 of around 30 nm, and as is clear from FIG.
C is efficiently excited.

Next, a stimulable phosphor sheet according to a third embodiment of the present invention will be explained. The stimulable phosphor sheet of this third example is:
In the stimulable phosphor sheet 10 shown in FIG. 1, 5rFBr:Eu phosphor is used as the stimulable phosphor IOC, while Na Yb (WOa
)2: Er phosphor was used. The stimulated excitation spectrum of the above Sr FBr:Eu phosphor is shown in (■) in FIG. 11, and the stimulated emission spectrum is shown in (■) in FIG. 12. In addition, the above NaYb (WOa)2
: The excitation spectrum of the Er phosphor is shown in FIG.

When reading radiation image information from the stimulable phosphor sheet 10 of the third embodiment using a device as shown in FIG.
An InP semiconductor laser that emits a laser beam 13 of nm wavelength is used. By being irradiated with the laser beam 13 of this wavelength, the NaYb(WO4)22E"phosphor 10
D mainly emits fluorescence with a wavelength of λ22-525n. 1st
As can be seen from Figure 1, the excitation peak wavelength of the SrFBr:Eu phosphor is the wavelength of the fluorescence λz −525 nm.
It is close to.

Therefore, in this case as well, when scanning the stimulable phosphor sheet 10 with the laser beam 13 having a wavelength of λ1-900 nm as a reading light, the SrFBr:Eu phosphor lOC, which cannot be excited efficiently with light in this wavelength range, is ,
Stimulated luminescence light is efficiently diverged.

Next, a stimulable phosphor sheet according to a fourth embodiment of the present invention will be described. The stimulable phosphor sheet 10 of this fourth embodiment is the stimulable phosphor sheet C of the third embodiment.
rFBr: Instead of Eu phosphor, Gd OCI
: Ce phosphor is used.

Furthermore, this Gd OCj! : The Ce phosphor has a C J /Gd ratio of 1.00 in the host crystal. The stimulated excitation spectrum of this Gd OCI:Ce phosphor is shown in (■) in FIG. 11, and the stimulated emission spectrum is shown in (■) in FIG. 12. As is clear from FIG. 11, in this case as well, when the stimulable phosphor sheet IO is scanned with a reading light having a wavelength λ1 = 900 nm, NaYb(WO
4) Z: Main wavelength λz emitted by Er phosphor 10D
=525 nm fluorescence, Gd QCf!
:Ce phosphor exhibits stimulated luminescence efficiently.

In addition to the above-mentioned γ-A, jF3:Fe3'''' phosphors and NaYb(WOa)2:Er phosphors, there are also phosphors that can be used by quantum counting or multistage energy transfer, such as certain rare earth phosphors. Accordingly, there are known phosphors that absorb light at a certain wavelength λ1 and emit fluorescence at a different wavelength λ2. They can be appropriately selected and used depending on the wavelength.

Next, a stimulable phosphor sheet according to a fifth embodiment of the present invention will be described. FIG. 14 schematically shows a stimulable phosphor sheet 10' of this fifth embodiment.

Note that in FIG. 14, elements that are equivalent to those in FIG. 1 are given the same numbers, and explanations thereof will be omitted.

In this stimulable phosphor sheet 10', instead of the phosphor 10D in FIG.
The phosphor 10E emits photostimulated light 60 with a wavelength λ2° included in the excitation wavelength range of the stimulable phosphor IOC when it receives light from the stimulable phosphor IOC.
It is included. As such a phosphor 10E, for example, SrS:Eu:SlI+phosphor is used. This SrS:Eu:Sm phosphor 10E exhibits green excitation mainly at a wavelength λ2° = 533 nm by infrared irradiation at a wavelength λ1° = 1000 nm after photoexcitation. - As the force storage phosphor 10C, a 5rFBr:Eu phosphor whose excitation peak wavelength is close to the wavelength λ2' is used.

When recording (photographing) radiation image information on the stimulable phosphor sheet 10' having the above structure, first, as shown in FIG. Light 3 of 400 nm is uniformly irradiated to 10° of the sheet. Next, on this stimulable phosphor sheet 10',
Radiographic image information is accumulated and recorded as shown in FIG. 7(a). This recording is performed in the same manner as the recording on the stimulable phosphor sheet 10 described above with reference to FIG. 6.

The stimulable phosphor sheet 10' on which transmitted radiation image information of the subject 6 has been stored and recorded as described above is subjected to a radiation image information reading device as shown in FIG. 8 to read the recorded information. As the laser light source 12, for example, a YAG laser that emits a laser beam 13 having a wavelength of λ1'-1064 nm is used. By being irradiated with the laser beam 13 having this wavelength, the phosphor 10E mainly emits photostimulated light 60 (see FIG. 14) having a wavelength λz = 533 nm. Therefore, the stimulable phosphor LOC uses this photostimulant 6
0 and emits stimulated luminescence light 15.

When light with a wavelength λ1' is irradiated after being photoexcited, the wavelength λ
The above-mentioned Sr
In addition to S:Eu:Sm phosphors, for example, infrared irradiation with a wavelength of around 11,000n produces an orange color (mainly wavelength λ2' -590n).
1m) SrS:Se showing photosensitivity.

SII phosphor or the like can also be used. This SrS;S
e, when using SIM phosphor 10E, stimulable phosphor 1
For 0C, the excitation peak wavelength is the above wavelength λ22-590
A BaFBr:Eu phosphor or the like close to n may be used.

In addition to dispersing the stimulable phosphor 10C and the phosphor 10E in a mixed state in a common binder ICIB, as shown in FIG.
The layers may be formed in close contact with each other, or may be formed separately with a slight separation. This occurs when a phosphor 10D that does not require optical excitation is used instead of the phosphor 10E (
The same applies to the first to fourth embodiments.

(Effects of the Invention) As described in detail above, according to the present invention, even if light with a wavelength deviating from the excitation peak wavelength of the stimulable phosphor constituting the stimulable phosphor sheet is used as reading light, It becomes possible to efficiently diffuse stimulated luminescence light. Therefore, according to the present invention, in a radiation image information recording and reproducing system using a stimulable phosphor sheet, the degree of freedom in selecting a stimulable phosphor and a reading light source is significantly higher than in the past. It is possible to achieve faster reading processing by using a low-cost reading light source, to reduce the cost of the reading device by using a low-cost reading light source, and to downsize the reading device by using a small reading light source.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the stimulable phosphor sheet of the present invention, and FIGS. 2 and 3 are respectively Cs I IIo, 058a F2 "0.0IAJ that can be used in the present invention.
Graphs showing the stimulated excitation spectrum and stimulated emission spectrum of the F3:0.002 Na phosphor, FIGS. The graph showing the excitation spectrum and emission spectrum, Figure 6, is
An explanatory diagram showing the state of radiographic image information recording in the first radiation image information recording and reading method of the present invention. FIG. 7 shows the state of radiographic image information recording in the second radiographic image information recording and reading method of the present invention. An explanatory diagram, FIG. 8 is a perspective view showing an example of a radiation image information reading device implementing the radiation image information recording and reading method of the present invention, and FIGS. 9 and 10 respectively show Rb Br that can be used in the present invention.・0.5 Ba FBr: 0,001
TJ! A graph showing the stimulated excitation spectrum and stimulated emission spectrum of the phosphor, FIG. 11, shows 5rFBr that can be used in the present invention:
A graph showing the photostimulation excitation spectra of the Eu phosphor and the Gd0C1:CC phosphor, FIG.
0CJ: A graph showing the stimulated emission spectrum of CC phosphor, FIG.
Graph showing the excitation spectrum of O, ) 2 :Er phosphor. FIGS. 14 and 15 are schematic diagrams each showing another example of the stimulable phosphor sheet of the present invention. 10, 10'...Stormable phosphor sheet 10A...
Support 10B... Binder 10C... Storable phosphor 10D, IOE... Phosphor 11...
Sub-scanning means 12... Laser light source 13... Laser beam (reading light) 14... Optical deflector 15... Stimulated luminescence light 1
7... Photomultiplier tube 50... Fluorescence 60...
Photostimulation-6・ 4 Figure 5 Skin length (nm) Figure 00 00 500 600 5i Flea (n m) 00 00 Figure Figure Figure 0 Figure 0 Figure length (n m) Figure 11 Figure 2

Claims (4)

[Claims] (1) In a stimulable phosphor sheet having a layer of stimulable phosphor that exhibits stimulated luminescence when irradiated with excitation light after accumulating radiation energy, the stimulable phosphor sheet receives light of wavelength λ_1 and the stimulable phosphor A stimulable phosphor sheet, comprising a phosphor that emits fluorescence at a wavelength λ_2 (λ_1≠λ_2) included in the excitation wavelength region of 1, in a layer facing the stimulable phosphor layer. (2) In a stimulable phosphor sheet having a layer of stimulable phosphor that exhibits stimulated luminescence when irradiated with excitation light after accumulating radiation energy, the stimulable phosphor sheet is photoexcited and then irradiated with light of wavelength λ_1'. , wavelength λ_2' (λ
A stimulable phosphor sheet comprising a phosphor that emits photostimulated light of _1'≠λ_2') in a layer facing the stimulable phosphor layer. (3) The stimulable phosphor sheet according to claim 1 is irradiated with radiation having image information, and then the stimulable phosphor sheet is irradiated with light of the wavelength λ_1, and the wavelength λ_2 emitted at this time is radiation image information recording, characterized in that stimulated luminescence light emitted by the stimulable phosphor is detected by a photodetector upon receiving the fluorescence of the stimulable phosphor as excitation light to obtain an electrical image signal carrying the image information Reading method. (4) The stimulable phosphor sheet according to claim 2 is excited with light, and then the stimulable phosphor sheet is irradiated with radiation having image information, and then the stimulable phosphor sheet is exposed to the light of the wavelength λ_1'. The stimulable luminescence light emitted by the stimulable phosphor is detected by a photodetector upon receiving the stimulated light of the wavelength λ_2' emitted at this time as excitation light, and carries the image information. A radiation image information recording and reading method characterized by obtaining an electrical image signal.