JPH04155300A - Radiation image converter - Google Patents

Abstract

PURPOSE:To prevent the deterioration of resolving power due to scattering an excitation light beam by providing the opposite side to the emitting side of the excitation light with a douser of a rectangular shape, forming a stimulated phosphor by providing both inside and outside surfaces of a stimulated phosphor layer with transparent protective films. CONSTITUTION:A stimulated phosphor 1 is carried into the direction rectangular with the excitation light 2 scanned by a scanning optical system and the scanning line 5 of the beam respectively by a roller 24, and the stimulated phosphorescent emission light is converged by converging part 14 to be transduced a electric signal. The douser 6 provided with the light absorbing layer absorbing the light of wave length of the excitation light 2 in the surface is arranged in the reverse side of the stimulated phosphor 1. Therefore, it is prevented that the excitation light 2 and the generated stimulated phosphorescent emission light are emitted to the rear side also of the stimulated phosphor 1, reflected by the mechanism parts, etc. being in the reverse side, again return to the stimulated phosphor 1 to excite positions other than the scanning point and consequently the resolving power deteriorates.

Description

[Detailed description of the invention] 【overview】

Regarding a radiation image conversion device, particularly a radiation image conversion device using a photostimulable phosphor, the object of the present invention is to provide a radiation image conversion device that can use a photostimulable phosphor plate or sheet that is easy to manufacture and inexpensive. x formed into a plate or sheet shape and transmitted through the subject
Radiation vA that absorbs a part of wA energy and accumulates as a latent image, irradiates the stimulated phosphor with excitation light, converts the emitted stimulated luminescent light into an electrical signal using a photoelectric converter, and obtains image information.
In the image conversion device, the photostimulated phosphor is formed by providing transparent protective films on both the front and back surfaces of the photostimulated phosphor layer, and the length of the scanning line of the excitation light is provided on the side opposite to the side irradiated with the excitation light. It is constructed by providing a rectangular light-shielding plate having a long side approximately equal to or longer than the length of the light-shielding plate and having a light-absorbing layer formed on its surface. [Field of Industrial Application] The present invention relates to a radiation image converting device, and particularly to a radiation image converting device using a photostimulable phosphor. Radiographic images such as XwA images are often used for disease diagnosis and the like. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer, thereby producing visible light, which is then irradiated onto a film made of silver salt and developed. Photos are used. On the other hand, as a high-sensitivity, high-resolution X-ray imaging system, instead of the conventional method of recording two-dimensional images of indirect or direct radiation on a film coated with a silver salt photosensitive agent in the form of a sheet,
Methods using stimulable stimulable phosphors are beginning to be utilized. When this stimulable stimulable phosphor receives the energy of radiation such as X*, it stores a part of the energy. This state is relatively stable and is maintained for a while or a long time. When the phosphor in this state is irradiated with the first light that acts as excitation light, the stored energy is released into the second light (luminescence). It is emitted as exhaustion light). FIG. 7 shows a radiation image conversion device using such a stimulable stimulable phosphor 1, in which a laser beam 10 from an excitation light source 9 is scanned by a scanner 11 consisting of a galvano mirror 1 or a polygon mirror, and an fθ lens The photostimulated phosphor 1 is scanned through an optical component 12 for beam shape correction, a reflecting mirror 13, etc. The energy of the X-rays irradiated through the object is stored as a latent image in the stimulable phosphor 1, and the energy is extracted as stimulated luminescence light by irradiation with the excitation light 2. This stimulated luminescence light is collected by a condenser 14 such as a fiber array, and is passed through a filter layer that does not pass the excitation light 2 and only passes the stimulated luminescence light, and is passed through a photoelectric converter 15 such as a photomultiplier tube.
guided by. The amount of light received is converted into an electrical signal by the photoelectric converter 15, and after being amplified by the amplifier 16, the A/D
The signal is converted into a digital signal by the converter 17 and temporarily stored in the frame memory 18, directly stored in a magnetic disk, or stored in the optical disk memory 19. Thereafter, at any time, the image processing unit 20 performs gradation processing, etc., and displays the image on the image display unit 21 such as a CRT as an X-ray image, or uses a film writing device to perform X-ray image processing.
A radiographic image can be obtained by writing directly onto the film and developing it. On the other hand, the stimulable phosphor 1 used in the above system,
It is not transparent to the first light, that is, the excitation light 2, nor to the second light, that is, the stimulated luminescence light, and exhibits a strong scattering phenomenon, so it has a size that is the same as or smaller than one pixel. Even if the stimulable phosphor 1 is irradiated with two beams of excitation light, the two beams of excitation light will be scattered very widely.For example, two beams of excitation light with a diameter of 0.07 mm will be irradiated onto a phosphor with a thickness of 0.3 mm. When this happens, it has been observed that on the surface opposite to the irradiated surface, the particle size spreads to a diameter of 1 mm or more, and in some cases, to a diameter of 3 mm or more. Such scattering of the excitation light 2 causes stimulated fluorescence to occur in a wide range, reducing the spatial resolution of the obtained image. In addition, in order to prevent this decrease in spatial resolution, it is possible to reduce the thickness of the photostimulated phosphor 1 to suppress the spread of scattered light, but in this case, the amount of generated photostimulated fluorescence will be reduced. Therefore, the method for suppressing the decrease in spatial resolution and ensuring the amount of light of photostimulated fluorescence is usually to use photostimulated phosphor 1.
It is applied to [tau]Prior Art Conventionally, as a photostimulable phosphor 1 used in this type of radiation image conversion apparatus, those shown in FIGS. 8 and 9, for example, have been proposed. In the case shown in FIG. 8, a light reflection layer 22 made of a metal vapor deposition layer or a white powder layer is formed on the back surface of the stimulable phosphor layer 3, and two beams of excitation light are transmitted inside the stimulable phosphor layer 3. While producing stimulated fluorescent light 23 as shown by the solid line,
The stimulated fluorescence light 23' directed towards the back surface is also reflected by the light reflection layer 22 as shown by the broken line and contributes to an increase in stimulated fluorescence, and the excitation light 2 is also reflected by the light reflection layer 22 to produce reflected light. As shown by the chain line, the photostimulated fluorescent light 23
” to effectively take out the stimulated fluorescence and improve the sensitivity. In FIG. On the other hand, in the case shown in FIG. 9, a filter layer 8 is formed between the light reflection layer 22 and the stimulated phosphor layer 3, which absorbs the excitation light 2 and transmits the stimulated fluorescence. The light reflecting layer 22 reflects only the stimulated fluorescence directed toward the back surface to increase the amount of the stimulated fluorescence light 23, and suppresses the reflection of the excitation light 2 to improve the S/N ratio.

[Problem to be solved by the invention]

However, in the above-mentioned conventional example, the stimulable phosphor 1 has the disadvantage that it is expensive due to its complicated structure, although it is easily damaged due to deterioration due to absorption of moisture. Met. The present invention has been made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a radiation image conversion device that is easy to manufacture and can utilize an inexpensive stimulable phosphor.

[Means to solve the problem]

According to the present invention, the above object is achieved by using a χ
Radiation image conversion to obtain image information by irradiating excitation light 2 onto the photostimulated phosphor 1, which absorbs a portion of the linear energy and accumulates it as a latent image, and converts the emitted stimulated luminescent light into an electrical signal using a photoelectric converter to obtain image information. In the apparatus, the stimulable phosphor 1 is formed by providing a transparent protective film 4 on both the front and back surfaces of the stimulable phosphor layer 3, and the excitation light 2 is applied to the side opposite to the side irradiated with the excitation light 2. Provided is a radiation image conversion device characterized in that a rectangular light shielding plate 6 having a long side approximately equal to or longer than the length of a scanning line 5 and having a light absorption layer formed on its surface is provided. This is achieved by Further, as shown in FIG. 3, the light shielding plate 6 may be a rectangular light reflecting plate 7 having a light reflecting layer formed on its surface.Furthermore, as shown in FIG. It is also possible to form the plate 7 with a light-reflecting layer and a filter layer 8 that absorbs the excitation light 2 and transmits the stimulated emission light. As shown, it is also possible to form the light reflecting plate 7 with a cylindrical mirror having a curvature in a direction substantially perpendicular to the scanning line 5 of the excitation light 2.

[Effect]

The stimulated phosphor used in the present invention is formed by providing a transparent protective film 4 on both sides of the stimulated phosphor layer 3, and the excitation light 2 and the stimulated fluorescent light 23 are opposite to the irradiation side of the excitation light 2. Transparent to the side. In the present invention, the stimulated fluorescent light 2 transmitted to the opposite surface
3 and the like are absorbed or reflected by a light shielding plate 6 or a light reflecting plate 7 provided in the device. As a result, the stimulable phosphor l, which is a consumable item, can be configured simply by providing the light shielding plate 6 and the like at only one place in the device, resulting in a reduction in costs as a whole.

【Example】

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. An embodiment of the invention is shown in FIGS. 1 and 2. FIG. As shown in FIG. 2, the stimulable phosphor layer 3
It has a layered structure in which a protective film 4 of transparent plastic or glass is formed on both the front and back sides. The thickness and length of the stimulable phosphor layer 3 vary depending on the sensitivity of the stimulable phosphor used, but are approximately 0.2 mm. Also,
The thickness of the protective film 4 is also influenced by its protective ability, mechanical strength, optical properties, etc., but is approximately 0.
．． The thickness is approximately 0.1 mm to 1 mm. Such a stimulable phosphor 1 can be produced by applying a stimulable phosphor mixed with an organic resin binder onto plastic or glass, and then forming a protective film 4 by applying plastic ink on top of the stimulable phosphor. It can be easily manufactured, and the flexibility, hardness, etc. of the photostimulable phosphor 1 can be freely selected depending on the material used, and it can also be formed into a plate shape in addition to a sheet shape. . The stimulable phosphor 1 formed as described above is transported in a direction perpendicular to the scanning [5] of two beams of excitation light that are scanned by a scanning optical system (not shown) by a roller 24, and generated from the stimulable phosphor 1. The stimulated luminescent light is collected by the condenser 14 and converted into an electrical signal by the procedure shown in FIG. The above-mentioned stimulable phosphor 1 is transparent on both sides, and the excitation light 2 and the generated stimulable luminescent light are also emitted from the back surface of the stimulable phosphor 1 and are reflected by mechanical parts on the back side, so that they shine again. In order to prevent the deterioration of resolution due to the excitation returning to the phosphor 1 and excitation in areas other than the scanning point, light at the wavelength of the excitation light 2 is placed on the back side of the phosphor 1. A light shielding plate 6 provided with a light absorption layer is arranged. This light shielding plate 6 has a rectangular shape whose long side has a length longer than the scanning line 5, and is arranged at a position where its center coincides with the scanning line 5. In addition, the length of the short side in this example is 1 to 2.
The length of the long side and short side is determined by the light scattering characteristics and thickness of the stimulable phosphor 1 used, and the length of the long side and short side is determined by the thickness of the stimulable phosphor 1. Any size that can be used is sufficient. FIG. 3 shows a second embodiment of the present invention, in which the above-mentioned light shielding plate 6
Instead, a light reflecting plate 7 having the same shape and having a mirror on its surface that reflects the wavelengths of the excitation light 2 and stimulated emission light is arranged. As already explained with reference to FIG. 8, in this embodiment, the excitation light 2 is reflected on the light reflection plate 7 and passes through the stimulated phosphor 1 twice, producing approximately twice as much stimulated luminescence light. At the same time, the stimulated luminescence light passing through the back surface of the photostimulable phosphor 1 is also reflected, so that the sensitivity is improved. In this case, the light reflecting plate 7 is formed by, for example, depositing a TL% thin film layer, and has wavelength selectivity such that the wavelength of the two excitation light beams is transmitted, but the wavelength of the stimulated luminescence light is reflected. By using a mirror, it is possible to prevent deterioration in resolution due to scattering of the two excitation light beams and to improve sensitivity. A similar effect can also be obtained by installing a so-called colored glass filter layer on the top surface of the reflector that absorbs the wavelength of the excitation light 2 and transmits the wavelength of the stimulated luminescence light, as shown in Figure 4. You can also get FIG. 5 shows a third embodiment of the present invention, in which a cylindrical mirror having a curvature parallel to the sub-scanning direction is used in place of the rectangular light reflecting plate 7 described above, and the center of curvature is , substantially coincide with the scanning line 5 on the surface of the photostimulable phosphor 1. According to this embodiment, the excitation light 2 or the stimulated luminescence light transmitted through the photostimulated phosphor 1 and scattered is reflected by the cylindrical mirror and focused on the scanning g5, so that the reflected excitation light 2 Deterioration of resolution due to scattering is prevented. In addition, when using a wavelength-selective mirror as a cylindrical mirror that transmits the wavelength of the two excitation light beams but reflects the wavelength of the stimulated emission light, deterioration of resolution due to scattering of the two excitation light beams can be prevented. As shown in FIG. A similar effect can be obtained by installing a so-called glass filter layer 8 that transmits light.

【Effect of the invention】

As is clear from the above description, according to the radiation image conversion device of the present invention, the light absorption layer, etc. that were conventionally formed inside the stimulable phosphor, which is a consumable item, has been replaced with a simple structure. Therefore, manufacturing is easy and inexpensive.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, (a) is a perspective view, (b) is a view taken in the direction of arrow A in (a), and Fig. 2 shows a stimulable phosphor used in the present invention. 3 shows a second embodiment of the present invention, FIG. 4 shows a modification of FIG. 3, FIG. 5 shows a third embodiment of the invention, and FIG. FIG. 7 is a diagram showing a modification of FIG. 5; FIG. 7 is a diagram showing a radiation image conversion device; FIG. 8 is a diagram showing a conventional photostimulable phosphor; FIG. 9 is a diagram showing another photostimulable phosphor. be. In the figure, 1... Stimulated phosphor, 2... Excitation light, 3... Stimulated phosphor layer, 4... Protective film, 5... Scanning line, 6... Shade plate, 7... Light reflecting plate, 8... Filter layer. No. IWJ Fist bone af4+ to discuss l exhaustion fluorescent cup 8 moves 1ω army 2 Zumoto Gi 1 River's oni real belly 4? ll! , Imo j mouth Figure 3 I 3 inside strange +? I walk '+1 show 1st eye 4th figure stay J 茫 [371 o three guests protection Igari Σ1su figure 1 m5 figure - 45 figure・'s $ f'z tp+IΣho TG4 6th figure release *J* elephant image I rectangle・Show the information at T-gate

Claims (1)

[Scope of Claims] [1] Excitation light (2) is applied to the photostimulable phosphor (1), which is formed in a plate or sheet shape and absorbs a portion of the X-ray energy that has passed through the subject and is accumulated as a latent image. In a radiation image conversion device that obtains image information by converting stimulated luminescence light emitted by irradiation into an electric signal by a photoelectric converter, the photostimulated phosphor 1 is transparently applied to both the front and back surfaces of the photostimulated phosphor layer (3). A protective film (4) is provided and formed, and the excitation light (
The side opposite to the irradiation side of 2) has a long side that is approximately equal to or longer than the length of the scanning line (5) of the excitation light (2), and a light absorption layer is formed on the surface. A rectangular light-shielding plate (
6) A radiation image conversion device characterized by comprising: [2] The stimulable phosphor (1), which is formed in a plate or sheet shape and absorbs a portion of the X-ray energy that has passed through the subject and accumulates as a latent image, is emitted by irradiating the excitation light (2). In a radiation image conversion device that converts the stimulated luminescent light into an electric signal using a photoelectric converter to obtain image information, the photostimulated phosphor (1) is coated with a transparent protective film ( 4), and on the side opposite to the irradiation side of the excitation light (2), a length approximately equal to or longer than the length of the scanning line (5) of the excitation light (2) is provided. A radiation image conversion device characterized in that a rectangular light reflecting plate (7) having sides and having a light reflecting layer formed on its surface is provided. [3] The radiation image conversion according to claim 2, wherein the light reflecting plate (7) has a light reflecting layer and a filter layer (8) that absorbs the excitation light 2 and transmits the stimulated luminescence light. Device. [4] The light reflecting plate (7) is arranged so that the scanning line (
5) The radiation image conversion apparatus according to claim 2 or 3, wherein the radiation image conversion apparatus is a cylindrical mirror having a curvature in a direction substantially perpendicular to 5).