JPH02308238A - Image reading system for digital x-ray image pickup device - Google Patents

Abstract

PURPOSE:To prevent spatial resolution from being deteriorated and to obtain the distinct image of an object by using a stimulable phosphor sheet where a stimulable phosphor is buried in a fine area which is formed to be the fine area where exciting light is not transmitted. CONSTITUTION:In the digital X-ray device where the latent image of an object is formed on the stimulable phosphor sheet 105 as an energy distribution pattern by using X-ray energy and the latent image is read by using the exciting light, the stimulable phosphor sheet where the stimulable phosphor is buried in a hole formed part 2 obtained by working an exciting light non-transmitting substrate is used in the case of forming the latent image of the object. In order to read out the energy distribution pattern, scanning is performed by a scanning device 10 and stimulated fluorescence radiated from the stimulable phosphor is received by a light receiving device 12 and reproduced by a reproducing device 14. Since the object pattern is accumulated in the stimulable phosphor in the fine hole every image element as the X-ray energy distribution pattern, the deterioration of the spatial resolution caused by the scattering of the exciting light into the stimulable phosphor layer is completely prevented and the image of the object is distinctly read.

Description

[Detailed Description of the Invention] [Summary] In order to form a latent image of a subject, a stimulable phosphor plate that can prevent optical interference between each pixel and other pixels is used to form and reproduce an image of the subject. Regarding the image reading method of the digital X-ray imaging device used, after irradiating the stimulable phosphor with radiation, when the stimulable phosphor is irradiated with excitation light and the stimulated luminescence light is received, the excitation light is scattered in the stimulable phosphor layer. The aim is to completely prevent deterioration of spatial resolution and read the subject image clearly by using X-ray energy to form a latent image of the subject as an energy distribution pattern on a phosphor plate In a digital X-ray device that reads images using excitation light, when forming a latent image of the subject, micro holes are formed that have the same size and are processed to be at least opaque to the excitation light, and in which a photostimulated phosphor is embedded. Each pixel of the subject image is formed in a corresponding integer number of microholes of one or more in a photostimulated phosphor plate formed at each intersection position in the intersecting direction, and the integer number of microholes of one or more are formed. Each of the pixels stored in the memory is read out and reproduced.

[Industrial application field]

The present invention is directed to a digital X-ray imaging device that uses a stimulable phosphor plate that can prevent optical interference between each pixel and other pixels in order to form a latent image of the object. Regarding image reading methods.

Radiographic images such as X-ray images are often used for disease diagnosis. In order to obtain this XIIA image, X-rays that have passed through the subject are irradiated onto a phosphor layer (phosphor screen), which generates visible light, which is then irradiated onto a film made of silver salt and developed. However, as a system to replace the conventional X-ray imaging device that records two-dimensional images of radiation indirectly or directly on a film coated with a silver salt photosensitive agent in the form of a sheet, a high-performance system is being used. Sensitive, high resolution X-ray imaging systems have been developed.

[Prior Art] The high sensitivity, high resolution X-ray imaging device is a system that uses a stimulable phosphor. The basic approach for such a system is detailed in US Pat. No. 3,859,527. When the phosphors used in this system receive energy from radiation such as X-rays, they store some of that energy. This state is relatively stable and is maintained for a while or for 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 as second light. At this time, the first light is not limited to visible light,
Light with a wide wavelength range from infrared to ultraviolet is used. However, the choice depends on the phosphor material used. There are various types of secondary light, ranging from infrared to ultraviolet light. The difference also depends on the phosphor material used. This second electromagnetic wave is received, converted into an electric signal by a photoelectric converter, and then converted into a digital signal to obtain digital image information.

[Problem to be solved by the invention]

As described above, a system is known in which the second electromagnetic wave is received, converted into an electric signal by a photoelectric converter, and then converted into a digital signal to obtain digital image information. The stimulated phosphor layer used in that system is not completely transparent to either the first light, excitation light, or the second light, stimulated emission light, and exhibits strong scattering phenomena. It shows.

Therefore, even if a photostimulated phosphor layer is irradiated with an excitation light beam of the same size or smaller than one pixel, the excitation light beam will be scattered very widely.For example, if a phosphor layer with a thickness of 0.3 mm is It has been observed that when a 1 m excitation light beam is irradiated, the beam spreads to a diameter of 1 mm or more on the opposite surface to the irradiated surface, and in some cases to a diameter of more than 3 mm (see (A) in Figure 2). )reference).

As a result of such scattering of excitation light, in the above example, if the size of one pixel is 0.1 m + n angle, when reading one pixel, the adjacent 100 ~
Since partial information of 900 pixels is also taken in, the spatial resolution of the resulting image is significantly degraded and the image becomes extremely unsharp.

Several technical improvement measures have already been proposed to improve the low spatial resolution caused by the excitation light scattering phenomenon of the stimulable phosphor layer used in the system.

For example, JP-A No. 55-146447, JP-A No. 58-58
The method of dispersing white fine particles in a phosphor layer shown in Japanese Patent No. 500, or Japanese Patent Application Laid-Open No. 170740/1986
A method of adding a coloring agent that absorbs excitation light as shown in Japanese Patent Publication No. 62-211600, or a method of adding a coloring agent or white fine particles to a supporting substrate of a stimulable phosphor as shown in Japanese Patent Application Laid-open No. 62-211600. There are many ways to form . Although such a method is a method for improving sharpness, which has been used for conventional X-ray film intensifying screens, it is clear that it is not a method for completely eliminating excitation light scattering. In addition, methods such as forming vertical cracks in the layer of stimulable phosphor, forming a honeycomb structure, or forming uneven patterns or mosaic patterns on the surface of the substrate, as shown in Japanese Patent Application Laid-open No. 60-171500, etc. There are also attempts to prevent scattering by forming However, these methods not only do not completely prevent scattering of excitation light, but also create the possibility of forming a moiré pattern in the obtained image.

The present invention was created in view of such problems, and after irradiating the photostimulated phosphor with radiation, when the excitation light is irradiated and the stimulated luminescence light is received, the excitation light is removed from the stimulated phosphor. It is an object of the present invention to provide an image reading system for a digital X-ray imaging device that can completely prevent deterioration of spatial resolution due to scattering into layers and clearly read a subject image.

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention.

As shown in this figure, the present invention is a digital When forming a latent image of the object, micro holes 2 having the same size and in which a stimulable phosphor is embedded in hole forming portions 2 processed in at least an excitation light-opaque substrate are placed at each intersection position in the intersecting direction. Each pixel of the subject image is formed in a corresponding integer number of microholes of one or more, and the pixels accumulated in the integer number of microholes of one or more are formed. It is configured so that each of them is read out and presented for reproduction.

In FIG. 1, 10 is a scanning device, 12 is a light receiving device, and 14 is a reproducing device.

[For production]

The X-rays irradiated onto the subject are transmitted through the X-rays, and the subject pattern is accumulated in the stimulable phosphor in the microhole for each pixel as the X-ray energy distribution pattern.

Since the stimulable phosphor is contained in the hole-formed part 2 that is not transparent to excitation light, the excitation light scanned by the scanning device 10 for reading out the energy distribution pattern is transmitted to the other hole-formed part 2. It does not scatter inward. Furthermore, since each pixel is used in such a manner that it does not share a microhole with other pixels, the light receiving device 12 receives the stimulated fluorescent light emitted from the stimulated phosphor upon irradiation with the scanned excitation light. and playback device 1
Therefore, it is possible to completely prevent deterioration of the spatial resolution of the image reproduced in 4.

[Example] Thickness: 0.04 mm, size: 360 mm x 440++
Micro holes (see 20 in FIG. 3) having a diameter of 0.040 mm and a vertical and horizontal pitch of 0.044 mm were formed by etching on the entire surface of the stainless steel. A solution prepared by dissolving thermosetting epoxy resin in an organic solvent and dispersing graphite powder is applied by screen printing to both sides (hole walls) (see 22 in Figure 3), excluding the microholes.

After drying, stack four of these stainless steel plates with a stainless steel plate coated with resin on one side, then place a 0.2 mm thick stainless steel plate with no holes on one side, put a weight on it, and press it. It was cured and bonded with 'c.

A stainless steel plate is preferable because it reflects excitation light and exhaust emission light. Therefore, scattering to other microholes can be completely prevented (see (A) in FIG. 2). On the other hand, phosphor powder consisting of BaClBr:EU with a particle size of 5 μm or less was dispersed in an organic solvent solution containing an epoxy resin as a binder, poured over the stainless steel plate under reduced pressure, embedded in the hole, and dried. . Repeat this operation three times to confirm that the stimulable phosphor has been embedded to the surface of the hole, then wipe off the mixture of stimulable phosphor and epoxy resin on the surface.
It was cured at 0°C, and then a transparent polyester sheet was adhered to the surface as a protective layer to obtain a stimulable phosphor plate (third
(see figure).

The stimulable phosphor plate produced as described above is used in a digital X-ray imaging device as follows.

A latent image of the subject is formed by irradiating the subject with X-rays on a photostimulable phosphor plate set in the digital X-ray imaging device, and the latent image is an energy distribution pattern.

The latent image of the energy distribution pattern can be read out from the stimulated phosphor plate as the intensity distribution of stimulated luminescence light by irradiation with excitation light in the following manner.

As shown in FIG. 4, a laser beam from an excitation light source 101 is scanned by a scanner 102 consisting of a galvano mirror or a polygon mirror.

The scanned laser beam is connected to an optical component 103 for beam shape correction such as an fθ lens and a reflecting mirror 104.
etc., the photostimulated phosphor plate 105 is irradiated with light and the photostimulated phosphor plate 105 is scanned.

101, 102, 1.03, 104 correspond to the scanning device IO in FIG.

The laser beam diameter on the surface of the stimulable phosphor plate was 170 μm in the sub-scanning direction and 40 μm in the main scanning direction. The size of the laser beam diameter is -i, the sub-scanning direction is 1
It needs to be smaller than the length of the pixel in the sub-scanning direction, and its extent is determined by the degree of wobble. The length in the main scanning direction is preferably smaller than the length of one pixel in the main scanning direction.

Stimulated fluorescent light emitted from the stimulated phosphor plate 105 by being scanned by a laser beam having the laser beam diameter is focused by a condenser such as a fiber array 107.

One standard pixel on which the light is focused is 176 μm square, and there are 16 holes (see (■) in FIG. 5) within this one pixel. When one pixel is 132 μm square, there are nine holes in one pixel (see (■) in FIG. 5), and the laser beam diameter in the sub-scanning direction is 125 μm. 1 pixel to 8
In the case of 8 μm square, there are four holes in one pixel (see (III) in FIG. 5), and the laser beam diameter in the sub-scanning direction is 83 μm. When one pixel is 44 μm square, there is one hole in the pixel (see (IV) in Figure 5), and the laser beam diameter in the sub-scanning direction is 39 μm and in the main scanning direction is 20 μm. . The integer is between 1 and 400. If it is 400, the purpose of the present invention is achieved, but if it is 40
It may be 0 or more. The reason why an integer number of microholes is used in one pixel is that if two pixels share a part of the microhole, the spatial resolution increases by that much. This is because it decreases.

Further, the shape of one pixel can be a square or a rectangle.

This shape is determined by the reading area or shape and the number of memories to be used.

Due to the difference in beam diameter for each scanning direction as described above, 44
, 88, 132, and four types of pixel sizes of 176 μm square can be selected, and any number of pixels each having a size of 176 μm square or more can be selected at intervals of 44 μm. However, if pixels of other sizes are required, it is necessary to change the size of the microholes.

Further, the reflected light of the excitation light from the wall surface was collected by a fiber array other than the fiber array 107 for collecting the light, received by the CCD, and synchronized to obtain the timing of the pulsed laser output.

This synchronization is for each microhole I11! Therefore, it can be used to determine the read signal for each pixel or to control the pulse output in the case of pulsed light excitation. In the process of excitation light scanning, each pixel receives strong reflections of the excitation light one or more times, and how to achieve synchronization is determined by the relationship between the hole and pixel sizes. The light receiving system that collects and receives the reflected light of the excitation light for synchronization and the light receiving system that collects and receives the stimulated luminescence light need to be separate systems.

That is, the light receiving system for synchronization is provided with a filter that absorbs or reflects the stimulated luminescence light, and the light receiving system for the stimulated luminescent light is provided with a filter that absorbs or reflects the excitation light. It will be done.

The collected light is guided to a photoelectric converter 108 such as a photomultiplier tube through a filter that does not pass excitation light from a fiber array or the like 107 but allows only stimulated emission light to pass through. The amount of received light is converted into an electrical signal in the photoelectric converter 108, and the amplifier 1
After being amplified by 09, it is converted into a digital signal by an A/D converter 110. 107,108,10
9 and 110 correspond to the light receiving device 12 in FIG. The digital signal is temporarily stored in the frame memory III, or is stored in the optical desk memory 112 without passing through the frame memory. Thereafter, the image processing unit 113 performs processing such as gradation processing at any time to display the image on the image display unit 11 such as a CRT.
4, or can be directly written on an X-ray film using a film writing device and developed to obtain an X-ray photographed image. 111,112
, 113 and 114 correspond to the playback device 14 in FIG.

When displaying an image via temporary storage in the frame memory 111, a standard dose of X-rays is irradiated, the standard output of each pixel is inputted into the memory, and the amount of stimulated luminescence is corrected over time. A normal image was obtained by correcting variations in shape and the like between each pixel. To correct this, techniques such as measuring the degree of variation for each pixel after the pixel size has been determined, or finding correction coefficients corresponding to several representative pixel sizes in advance, can be used. use

In addition, the microholes in the above embodiments may be formed in circular or square shapes each having a diameter smaller than one side of the area in the subdivided areas in a direction perpendicular to the surface of the thin metal plate or plastic sheet. good. However, the shape of the hole is not limited to circular or square, but may be oval or rectangular. Further, the shape of the hole may be straight, or the upper and lower sizes may be different. The material for forming the hole may be any material as long as it has a certain degree of mechanical strength after the hole is formed. The method for forming the hole is not limited to any means. The results vary depending on the type of material and the means of forming the hole.

For example, a stainless steel plate with a thickness of 0.1 mm and a diameter of 0.0 mm.
If a 0.8 mm hole is formed by etching with a vertical and horizontal pitch of 0.1, the shape of the hole will not be completely straight. If etched from both sides, the center may be constricted, or it may have a different shape depending on how the holes in the mask are formed. Or, when forming a hole by electrical discharge machining, the shape is relatively straight.
Although various shapes can be taken, it is possible to implement the present invention regardless of the shape.

In addition, the hole wall or its wall surface must be opaque to excitation light or excitation light and stimulated fluorescence light as described above, but if the material of the hole wall itself is transparent to excitation light. It is possible to prevent the excitation light from passing through by coating or vapor depositing a material that does not transmit the excitation light. The wall surface preferably reflects excitation light or excitation light and stimulated luminescence light.

By doing so, the excitation light can work efficiently, and the stimulated luminescence light can be used efficiently. If the wall surface of the hole does not have surface precision in an optical sense, it is effective to smooth it by coating with resin and then form a layer with high reflectance such as metal on top of it.

The material of the stimulated phosphor may be opaque so as to cause scattering of excitation light, or transparent to excitation light or stimulated emission light, and its composition is not limited.

As an example of the relationship between the size of the pixel used and the size of the microhole, for example, the standard size of one pixel is 0.4 square, and the inside of the phosphor plate is 400 mm. When dividing the area into equal areas, the size of one sub-divided area is 0.02 mm square. Its 0.02rr
A hole with a diameter of 0.02 mm or less is formed in the rm square.

The smallest pixel size that can be used at this time is 0.02 Peng angle a O,02InI! The size of a pixel that can be larger than one square is an integral multiple of 0.02 mm square.

Although there is no need to limit the upper limit, the number of microholes is usually one sieve size or less in view of the spatial resolution required for X-ray photography.

The thin flat plate material forming the microholes may be one that transmits stimulated luminescence light, or vice versa, depending on how it is used, that is, the direction of irradiation of excitation light and the direction of convergence of stimulated luminescence. It is possible depending on your choice. It is also effective to form the cover, which functions as a selection mirror, on both sides by adhesive or the like. The type of cover is not particularly limited, but in order to prevent backscattered X-rays, it is also effective to use, for example, lead glass, which allows excitation light and stimulated emission light to pass through but absorbs X-rays.

Alternatively, pasting a lead plate is also effective.

As for the scanning method of the stimulable phosphor plate, the excitation light scanning system and the condensing light receiving system are fixed, and whether the stimulable phosphor plate is moved or vice versa, the stimulable phosphor plate and the secondary The angle with respect to the scanning direction is uniquely determined in relation to the efficiency of excitation light scanning and the size of one pixel. In other words, the positions of the starting point and ending point on one line are the size of one pixel multiplied by the scanning efficiency, and the stimulable phosphor plate is moved in the sub-scanning direction so that a shift corresponding to that amount occurs between the starting point and the ending point. must be tilted against. Since this angle is at most one pixel, at least there will be no area problem such as the desired photographing section protruding. Although it is rare to change the size of one pixel frequently, it is easy to set it automatically.

[Effects of the Invention] As described above, according to the present invention, there is provided a stimulable phosphor plate having a structure in which a micro region that is opaque to excitation light is formed and a stimulable phosphor is embedded within the micro region; By using a method that does not share the minute area with other pixels, it is possible to completely prevent deterioration of spatial resolution and obtain a clear image of the subject.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of excitation light scattering in a stimulable phosphor, Fig. 3 is a diagram showing a stimulable phosphor plate with circular microholes, and Fig. 4 is a digital X FIG. 5, a block diagram of the line reading device, is a diagram showing the pixel formation type and the number of microholes therein. In FIGS. 1, 3 to 5, -2 is a hole forming part, 105 is a stimulable phosphor plate, 10 is a scanning device, 12 is a light receiving device, and 14 is a reproduction device. Ohe day J, z Takufu” o/7 “Time 1 Figure 1 (A) v-it○ pigeon (B) loose (fake money full x green scolding super good morbidity-no cedar 1) (Figure 4 of the circle (A) So-open side Kuko old) 1 Gate #1''Wayamamu Iv? 、Kotaguchi、B℃U、Higuno Medium・Imon・Tojimibu(Rin~2t・I ``Gro Figure 5

Claims (1)

[Claims] (1) In a digital X-ray device that forms a latent image of a subject as an energy distribution pattern on a photostimulated phosphor plate (105) using X-ray energy and reads the latent image using excitation light, the latent image of the subject is Hole forming portions (2) that have the same size and are processed to be at least opaque to excitation light during image formation
One pixel of the subject image is inserted into a corresponding integer of one or more microholes of a photostimulable phosphor plate, which is formed by forming microholes (2) in which a photostimulable phosphor is embedded at each intersection position in the intersecting direction. 1. An image reading method for a digital X-ray apparatus, characterized in that each pixel stored in an integer number of one or more microholes is read out and reproduced.