JPH03100644A - Radiation image converting panel - Google Patents

Abstract

PURPOSE:To enhance sharpness and durability by providing a stimulable phosphor layer on a base and shielding this layer with a protective layer body having >= 0.05mmPb lead equiv. CONSTITUTION:The stimulable phosphor layer 1 is provided on the base 3 and is shielded with the protective layer body 2 having >= 0.05mmPb lead equiv.. The protective layer body 2 which has >= 0.05mmPb led equiv. in X-ray absorptivity, good light transmittability and substantially zero moisture permeability and can be molded to a sheet shape is used and sheet glass contg. heavy metals, such as Pb, Ba, Ag, Au, Pt, and W and contg. Pb in particular is more preferable. The moisture-proofness and durability of the converting panel are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a radiation image conversion panel having a photometric phosphor layer, and more particularly to a high sharpness, moisture-proof radiation image conversion panel.

[Conventional technology]

In place of conventional silver halide photosensitive materials for obtaining X-ray images used in disease diagnosis, an X-ray image conversion method has been devised to directly extract an image from a phosphor layer.

This method uses a radiation image conversion panel (hereinafter referred to as conversion panel) that has a photometric phosphor layer (hereinafter referred to as photostimulation layer), and the radiation transmitted through the subject passes through the photostimulation layer of this conversion panel. to accumulate radiation energy corresponding to the radiation transmittance of each part of the subject to form a latent image, and then scan this photostimulation layer with photostimulation excitation light to emit the accumulated radiation energy of each part. This is converted into light, and an image is obtained using an optical signal based on the intensity of this light.

This final image may be reproduced as a hard copy or on a CRT.

The conversion panel used in this radiation image conversion method stores radiation image information and then releases the stored energy by scanning the stimulated excitation light, so it can store radiation images again after scanning, and can be used repeatedly. It is possible.

Therefore, it is desirable that the conversion panel has the ability to withstand repeated use for a long period of time or many times without deteriorating the quality of the obtained radiographic image. For this purpose, the stimulable layer of the conversion panel needs to be sufficiently protected from external physical or chemical stimulation.

In conventional conversion panels, in order to solve the above problems, a protective layer is provided to cover the photostimulable layer surface on the support of the conversion panel, and the periphery of the conversion panel is sealed to protect the photostimulable layer. I've been exposed to it.

In order to further increase moisture resistance, we used a protective layer that is thicker than conventional protective layers and has a greater moisture-proofing effect, and a spacer was bonded and sandwiched between the support and the protective layer to surround the stimulable layer, resulting in a sealed shell. A type conversion panel (Japanese Patent Application No. 141522/1983) was proposed, and a method was further developed to increase the moisture-proofing effect by filling the outside of the spacer with a filler that also served as a moisture-proofing material (Japanese Patent Application No. 1983-141522).
-141523) is presented.

As the convenience of the above-mentioned photoelectric conversion panel method for X-ray images has been recognized, among the three components of the X-ray generation device, the subject, and the panel processing device, the panel processing device group in particular has become Devices have been developed for irradiation, photostimulated luminescence, photostimulated reading, and erasure of photostimulated residual energy in preparation for repeated use, or turbidity processing. It is a compact and small photostimulation image reading device in which the devices included in the device are connected to each other by a control mechanism, and has been assembled into a built-in type that handles the entire process from radiation image formation to photostimulation image readout using a panel that is still set in the device. ing.

Furthermore, instead of the method of irradiating the image radiation onto the photostimulable layer from the protective layer side and then reading the photoelectrically converted image from the protective layer side, the photoelectric conversion reading of the radiation image is performed using a conversion panel attached to the photostim image device. A radiation image of the object is incident on the support side and transferred to the photostimulable layer, and then without removing the attached conversion panel, it is directly stimulated and excited from the protective layer side, which is constructed with sufficient optical consideration. A continuous and unidirectional incidence-readout method of photostimulation imaging apparatus has been developed for reading out the photochromic image. According to this method, it is possible to shorten operation time, consolidate the equipment, and downsize the equipment.

However, it has become clear that when using the compact and convenient built-in photostimulation imaging device as described above, there is an unexpected problem due to scattered X-rays.

In other words, the scattered X-rays emitted by the subject are removed by the grid, but the X-rays that form the subject image on the panel are further scattered as backscattered X-rays or secondary It creates lines that re-enter the panel and cause disturbances to the image, ie, deterioration of sharpness, contrast, resolution, etc.

In a system in which the panel is housed in a cassette, these backscattered or secondary X-rays can be absorbed by providing an X-ray absorbing plate on the back side of the panel, as in the conventional cassette for silver halide X-ray film. However, in a non-cassette type built-in photostimulation imaging device, an
It becomes necessary to further provide a mechanism for removing the absorbing plate which obstructs the reading of the photostimulated image, impairing the function and efficiency of the photostimulating image device.
It also increases costs.

(Object of the Invention) An object of the present invention is to provide a radiation image conversion panel with high sharpness and good durability.

In particular, the present invention provides a high sharpness conversion panel for the unidirectional incidence/readout method.

(Structure and Effects of the Invention) The object of the present invention is achieved by a radiation image conversion panel in which a support is provided with a photometric phosphor layer and covered with a protective layer having a lead equivalent of 0.05n+Pb or more. .

Note that the lead equivalent is the value of the X-ray attenuation ability converted to the thickness of the lead plate. Further, in the present invention, a protective layer having a lead equivalent amaPb is one whose absorption rate of 80 KeV X-rays is equal to that of a lead plate having a thickness of atm.

Next, the present invention will be described in detail. First, one embodiment of the shell conversion panel of the present invention is shown as a sectional view in FIG.

In FIG. 1, l is a photostimulable layer, 2 is a protective layer according to the present invention, 3 is a support, 4 is a low refractive index layer, and 5 is a spacer.

A conversion panel according to the present invention is designated as 4 in the photostimulator block diagram shown in FIG.
It is set with the support side facing the subject M1, that is, the outside of the apparatus, and the protective layer side facing inward.

Note that the numerical symbols in FIGS. 1 and 2 are assigned completely independently.

Block diagram illustrating the photostimulation apparatus according to the present invention, second
In the figure, a radiation source 1 is controlled by a radiation control device 2 to irradiate a subject M (such as a human chest) with radiation. The photosensitivity imaging device 3 includes the above-described panel 4 on the surface facing the radiation source 1 with the subject M in between,
The panel 4 forms a latent image of the subject M therein by accumulating energy in the photostimulable layer according to the radiation transmittance distribution of the subject M with respect to the radiation dose irradiated from the radiation source 1.

A light beam generator (gas laser, solid-state laser, semiconductor laser, etc.) 5 generates a light beam with controlled output intensity,
The light beam reaches the scanner 6 via the optical system, where it is deflected, and the optical path is further changed by the reflector 7, and the excitation scanning beam is sent to the panel 4 while being set at the position where it received the image radiation. guided as.

The condensing body 8 has a condensing end made of an optical fiber located close to the panel 4 scanned by the excitation light, and emits an emitted light whose intensity is approximately proportional to the latent image energy from the panel 4 scanned by the light beam. Read out the bright light.

9 is a filter that allows only the light in the stimulated emission wavelength region to pass through from the light introduced into the condenser 8; the light that has passed through it enters the photomultiplier 1O, and is converted into a current signal corresponding to the incident light. converted. The excitation mechanism and the light collection mechanism move along the surface of the panel 4 as an excitation/readout unit.

7 The output current from the automaton 10 is the current/voltage converter 1
After being converted into a voltage signal in step 1 and amplified in amplifier 12,
The A/D converter 13 converts the data into digital data. Then, this digital data is sequentially recorded in the image memory 14. 15 is a CPU, which performs various image processing (for example, gradation processing, frequency processing, movement, rotation, statistical processing, etc.) on the image information stored in the memory 14, and the image information as a result of the processing is , are displayed on the image display device 16. Reference numeral 17 denotes an interface for transmitting image information in the memory 14 to the outside or for receiving similar information from the outside. Reference numeral 18 denotes a reading gain adjustment circuit, and this circuit adjusts the light beam intensity of the light beam generator 5, adjusts the gain of the photomultiplier by adjusting the power supply voltage of the high voltage power supply 19 for the photomultiplier, and the current/voltage converter 11 and the amplifier 12. gain adjustment and input dynamic range adjustment of the A/D converter 13 are performed, and the readout gain of radiation image information is comprehensively adjusted.

The protective layer used in the present invention has good translucency and has an X-ray absorption rate of lead equivalent of 0.05 mn+Pb or more.
The material used has virtually no moisture permeability and can be formed into a sheet.

Such materials include, for example, Pb, Ba, Ag,
Au.

Plate glasses containing heavy metals such as pt and w, particularly those containing PB, are preferred. The wt% as PbO is 5~
70 wt% is suitable, and 30 to 60 wt% is preferred.

Moreover, the heavy metal contained may be one type or a plurality of types.

Furthermore, it is preferable to provide an anti-reflection layer such as MgF2 on the surface of the protective layer, since it allows stimulated excitation light and stimulated luminescence to pass through efficiently and reduces the decrease in sharpness.

Moreover, the thickness of the protective layer is 50 μm to 5 mm, and preferably 100 μm to 3 mm in order to obtain good moisture resistance.

After forming the stimulable layer on the support or the protective layer, a spacer is provided between the support and the protective layer to surround the stimulable layer. There is no particular restriction on the material as long as it can be held in a state where it is shielded from the air, and glass, ceramics, metal, plastic, etc. can be used.

In addition, the spacer has a moisture permeability of 30g/m"・24h
The thickness of the spacer, which is preferably less than It is determined in relation to the moisture resistance (moisture permeability) of the part, and is preferably 1 to 30 mm.

Note that the moisture permeability of the portion in close contact between the spacer, the support, and the protective layer is preferably 30 g/m''·24 hr or less.

Here, an adhesive or the like is used, for example, to bring the spacer into close contact with the support and the protective layer, but it is preferable that the adhesive has moisture-proof properties. Specifically, epoxy resins, phenolic resins, cyanoacrylate resins, vinyl acetate resins, vinyl chloride resins, urethane resins,
Organic polymer adhesives such as acrylic resin, ethylene vinyl acetate resin, olefin resin, chloroprene rubber, nitrile rubber, silicone adhesive, alumina,
Examples include inorganic adhesives containing silica or the like as a main component.

Among these, epoxy resins and silicone resins used for sealing semiconductors and electronic components are preferred because they have excellent moisture resistance, and epoxy adhesives are particularly preferred because they have low moisture permeability.

In the conversion panel of the present invention, it is preferable to have a low refractive index layer between the photostimulable layer and the protective layer because deterioration in sharpness due to the protective layer is suppressed.

This low refractive index layer exists in a state where it is shielded from the external atmosphere by a spacer, and by providing the low refractive index layer in this way, the thickness of the protective layer can be substantially increased. , the moisture resistance and durability of the conversion panel can be further improved.

Examples of such a low refractive index layer include a layer made of an inert gas such as air, nitrogen, and argon, and a layer having a refractive index of substantially 1, such as a vacuum layer; ethanol (refractive index 1.36);
Methanol (refractive index 1.33) and diethyl ether (
It can also be a layer made of a liquid with a refractive index of 1.35) or the like. In addition to these, the low refractive index layer may also be made of, for example, CaFz (
(Refractive index 1-23 to 1.26), NazAIFs (Refractive index 1.35), ugF, (Refractive index 1.38), 5i02
(refractive index: 1.46) or the like.

As the low refractive index layer of the conversion panel manufactured according to the present invention, a gas layer or a vacuum layer is preferable because it is highly effective in preventing deterioration of sharpness.

The practical thickness of the low refractive index layer is 0.05 μm to 3IIIfi.

The stimulable phosphor used in the present invention is irradiated with first light or high-energy radiation, and then stimulated (stimulated excitation) thermally, mechanically, chemically, or electrically. It is a phosphor that exhibits stimulated luminescence corresponding to the amount of initial light or high-energy radiation irradiation, but from a practical standpoint, it is preferably a phosphor that exhibits stimulated luminescence by excitation light of 500 nm or more. As such a photostimulable phosphor, for example, B described in JP-A-48-80487 is used.
aSO42AX.

SrSO4 described in JP-A-48-80489
:AX% Li1B of JP-A-53-39277=07:
Cu, Ag, etc., LtzO of JP-A-54-47883
・(B202)x: Cu and Li, 0・(B, 01)
x: Cu, Ag et al., SrS of US Pat. No. 3,859.527: Ce, SI+.

SrS:Eu, Sm%La, O! S: Eu, S+s
and (Zn, Cd) S :Mn.

In addition, Zn described in JP-A No. 55-12142
S: Cu, Pb phosphor, general formula BaO x A12z
03: Barium aluminate phosphor represented by Eu and general formula M O xsi
Examples include alkaline earth metal silicate phosphors represented by O=:A. Furthermore, an alkaline earth fluorohalide phosphor with the general formula % formula % described in JP-A No. 55-12143, and a general formula % formula % described in JP-A-55-12144 : A phosphor represented by the general formula % formula % described in JP-A No. 55-12145: A phosphor represented by the general formula % formula % described in JP-A-55-84389. A rare earth element-activated divalent metal fluorohalide phosphor described in JP-A No. 55-160078, a rare earth element-activated divalent metal fluorohalide phosphor with the general formula ZnS:A, CdS:A, (Zn ,
Cd) S:A, S:A, ZnS:A, X and CdS:A
, Examples include phosphors represented by any of the following general formulas %: and alkali halide phosphors represented by the following general formula %: described in JP-A No. 61-72087. In particular, alkali halide phosphors are preferred because they facilitate the formation of a stimulable layer by methods such as vapor deposition and sputtering.

Furthermore, alkaline earth fluorohalide phosphors and alkali halide phosphors are particularly susceptible to significant deterioration due to moisture, and therefore the present invention is particularly effective.

However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphors, but can be any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with stimulable excitation light. It may also be a phosphor.

In the method of the present invention, the layer of the stimulable phosphor is formed on the support or the protective layer using a coating method, a vapor deposition method, or the like.

Such a stimulable layer may be a stimulable layer group consisting of one or more stimulable layers containing at least one kind of the above-mentioned stimulable phosphors. The stimulable phosphors contained in the stimulable layer may be the same or different.

The layer thickness of the stimulable layer of the conversion panel varies depending on the radiation sensitivity of the intended conversion panel, the type of stimulable phosphor, etc., but in the case of not containing a binder, it is 10/J m to '10.
00pta range, preferably 20pra to 800μ
m, and 20p if it contains a binder.
ts to 1000 μm, preferably 50 μI11 to
It is selected from a range of 500 μm.

Supports used in the present invention include various polymeric materials, glasses, ceramics, metals, and the like.

Examples of the polymeric material include films such as cellulose acetate film, polyester film, polyethylene terephthalate, polyamide, polyimide, triacetate, and polycarbonate. As a metal,
Examples include metal sheets or metal plates of aluminum, iron, copper, chromium, etc., or metal sheets or metal plates having a coating layer of the metal oxide. Examples of the glass include chemically strengthened glass and crystallized glass. Examples of ceramics include sintered plates of alumina and zirconia.

In addition, the layer thickness of these supports varies depending on the material of the support used, but is generally 80μ■ to 5a+m,
From the viewpoint of ease of handling and obtaining good moisture resistance, the range is preferably 200//1 to 3+n+o.

The surfaces of these supports may be smooth or matte for the purpose of improving adhesion to the photometric phosphor layer. Further, the surface of the support may be an uneven surface, or may have a surface structure in which individual micro tile-like plates are closely arranged.

Furthermore, on these supports, a subbing layer may be provided on the side where the photostimulable layer is provided for the purpose of improving adhesion with the photostimulable layer, and if necessary, a light reflective layer, a light absorbing layer, etc. A layer etc. may be provided.

〔Example〕

Next, the effects of the present invention will be illustrated by examples.

Example 1 A lead glass plate (PbO 56 vt%) of the example with a lead equivalent of 0.45 mPb and a thickness of 2.0 am was used, and a borosilicate glass plate (PbO; 1.7 mm thick with a lead equivalent of 0.02 + mmPb) as a comparative example. i wt% or less) as a protective layer.

On the protective layer side of the two conversion panels, an Aff section for backscattering generation in which an Aρ block with a thickness of 20a+m is placed as a backscattering generation member and a blank section in which no AI2 block is placed are arranged side by side, and X-rays of 80 KeVp are emitted. Irradiation was performed from the support side, the intensity of photostimulated light generation was read, and the increase (%) in the AI2 section relative to the blank section was determined.

In the example, the increase was only 1.5%, and in the comparative example, it increased to 9%.

That is, according to the present invention, the disturbance caused by backscattering could be controlled to I/6.

Example 2 Lead equivalent: 0. Using In+a+Pb, a 2.0 mm thick lead glass plate (PbO; 15%) as a protective layer, the increment of the AI1 section relative to the blank section was determined in the same manner as in Example 1, and the increment due to backscattering was 4.6. %, and we were able to reduce the number of disabilities by about half.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the radiation image conversion panel of the present invention. l...Photostimulation layer 2...Protective layer 3...Support 4...Low refractive index layer 5...Spacer FIG. 2 shows the structure of a photostimulation image device according to an embodiment of the present invention. FIG. l... Radiation source 2... Radiation control device 3.
...Radiation image information recording/reading device 4...Radiation image conversion panel 5...Light beam generating section 6...Scanner '7...
Reflector 8... Concentrator 9... Filter 10.
...Photomaru 11...Current/voltage converter 12.
...Amplifier 14...Image memory 17...Interface 19...High voltage power supply 13...A/D converter 15...CPU Ace 18...Gay 16...Display adjustment circuit

Claims (1)

[Claims] A photometric phosphor layer is provided on the support, and the lead equivalent is 0.05 mm.
A radiation image conversion panel covered with a protective layer made of Pb or more.