JPH02129600A - Phosphor plate for radiation image reading - Google Patents

Abstract

PURPOSE:To evade deterioration in resolution while increasing sensitivity by forming a support plate which has holes in its thickness direction by using a material which transmit neither light for reading nor light to be excited and charging a phosphor where radiation is stored in the holes. CONSTITUTION:As phosphor 1, material obtained by mixing a binder in the powdery or resin state of phosphor crystal is used. The support plate 2 is formed of a material, such as a stainless steel, which does not transmit 1st light for reading and 2nd light excited with the light. Many small holes 3 are formed in the support plate 2 in a thickness direction and the phosphor 1 is charged therein. The holes 3 are more than picture elements required for an image and arranged uniformly or at random. The cross section of the holes 3 is, for example, a circle and the size of the holes 3 is smaller than that of one picture element. The depth of the holes 3 is about 1/4-20 times the diameter. The holes 3 may be through holes, but the flank is slanted and the flat bottom surface is increased in reflection factor to obtain the effect that 2nd light is projected from the holes 3 without spreading.

Description

[Detailed Description of the Invention] [Summary] To obtain a stimulable phosphor plate (imaging plate) in which the resolution does not deteriorate even when the phosphor layer is thickened to increase the sensitivity. By.

It has a support plate with a plurality of holes in the thickness direction, and a phosphor that stores the radiation image filled in the holes, with the aim of improving the performance of a radiation image reading device such as an X-ray image.

The support plate is formed of a material that does not transmit the first light for reading out the phosphor and the second light excited by it, and the holes have more than the number of pixels necessary for an image, and are arranged uniformly or Configure it so that it is randomly placed. Furthermore, the support plate is configured to include a portion in which a plurality of thin plates having a plurality of through holes are overlapped in the thickness direction.

[Industrial application field]

The present invention relates to a stimulable phosphor plate for reading radiographic images.

A stimulable phosphor plate temporarily accumulates a two-dimensional image of radiation such as X-rays, and then irradiates it with electromagnetic radiation such as a laser beam, thereby generating a second electromagnetic radiation according to the energy of the accumulated radiation. It is used in the device 1> which reads a two-dimensional radiation image by emitting and converting it into an electrical signal.

1) For example.

Yamada, et al., 'A revolutionary X-ray photographic system゛°; Science, (1984-1) p82-91゜In recent years, conventional silver salt photosensitizers have been used in sheet form as high-sensitivity, high-resolution XvA imaging systems. As an alternative to recording two-dimensional images of indirect or direct radiation on coated films, the use of stimulable phosphors is beginning to be utilized. When the storage phosphor used in this system receives energy from radiation such as X-rays, it leaves traces of the radiation in the form of defects in the phosphor crystal. This state is relatively stable.

It is held for a while or for a long time. When the phosphor in this state is newly irradiated with the first light, the stored energy is released as the second light.

At this time, the first light is not limited to visible light, but has a wide wavelength range from infrared to ultraviolet. However, the choice depends on the phosphor material used.

The second light also has various wavelengths from infrared to ultraviolet. The difference also depends on the phosphor material used.

When irradiated with visible or near-infrared light, storage phosphors emit visible to ultraviolet light with shorter wavelengths.
When irradiated with long-wavelength infrared rays that have a large thermal effect, short-wavelength visible to ultraviolet light may be emitted.

The former is called a photostimulable fluorophore, and the latter a thermal fluorophore.

[Conventional technology]

In order to further improve radiation image reading systems that use stimulable phosphors, it is necessary to improve the sensitivity of the phosphors to obtain greater emission intensity even for radiation that is weaker than before.

If the phosphor has high sensitivity, it is possible to reduce the amount of radiation required for exposure, and at the same time, the amount of first light required for continuous exposure can be reduced, allowing for faster scanning and the time required for reading. Processing time can also be reduced.

One way to increase the sensitivity of a phosphor to radiation is to increase its absorption of radiation. In order to absorb more radiation, it is possible to use more elements with large atomic weights in the phosphor material. Alternatively, an apparent increase in sensitivity can be achieved by increasing the thickness of the phosphor layer that receives radiation and accumulates a two-dimensional image.

[Problem to be solved by the invention]

Increasing the thickness of the phosphor layer to increase the sensitivity of the phosphor to radiation generally comes at the expense of resolution.

FIG. 7 is a diagram for explaining the problems of the conventional example, and is a cross-sectional view showing the spread of the reading light beam when it is incident on the phosphor plate.

In the figure, as the light beam penetrates in the thickness direction,
The light beam gradually spreads because it is scattered by the surfaces and grain boundaries of the crystal grains of the phosphor.

If the phosphor plate has already been irradiated and has accumulated a two-dimensional radiation image, all phosphor material irradiated by the expanded light beam will emit a second light.

The resolution of the image depends on the cross-sectional size of the narrow light beam. That is, a readout light beam is irradiated onto a small area of the phosphor plate, a second light emitted from the area is quickly detected, and the readout light beam is first moved laterally to the next part of the phosphor plate. Detecting second light from a small area of.

In order to increase the resolution of the successive images, it is necessary to be able to independently separate the second light from a region as small as possible.

In the present invention, even if the phosphor layer is made thicker than before to increase sensitivity,
The purpose is to obtain a stimulable phosphor plate with no deterioration in resolution.

[Means to solve the problem]

The solution to the above problem is to have a support plate having a plurality of holes in the thickness direction, and a phosphor filled in the holes for accumulating a radiation image, and the support plate has a phosphor for reading out the phosphor. formed of a material that does not transmit the first light and the second light excited thereby;
A phosphor plate for reading a radiographic image, in which the number of holes is equal to or greater than the number of pixels necessary for an image, and the holes are arranged uniformly or randomly.

The support plate described above is achieved by a phosphor plate for reading radiographic images, which includes a portion in which a plurality of thin plates having a plurality of through holes are stacked together in the thickness direction.

FIG. 1 is a diagram showing the principle of the present invention, and is a sectional view of a phosphor plate.

The figure shows a state in which a hole 3 made in a support plate 2 is filled with a phosphor 1.

Next, each component will be explained.

(2) Fluorescent material 1: The fluorescent material 1 may be in the form of a fluorescent crystal powder, or may be in the form of a binder such as a resin mixed therein. or.

- It may be filled with a binder and then the binder removed.

(2) Support plate 2: The support plate 2 is made of a material that does not transmit the light of the reading brush 1 and the second light excited thereby.

Therefore, it may be transparent to light of other wavelengths.

A large number of small holes 3 are formed in the support plate 2 in the thickness direction,
A phosphor 1 is filled in this.

The number and arrangement of holes (cells) are greater than the number of pixels required for an image, and are arranged uniformly or randomly.

The material of the support plate 2 is metal such as stainless steel, ceramics such as alumina, carbon material, plastic with dispersed pigment or dye that absorbs the first and second light, or transparent material such as glass or plastic. However, the surface (the side surface of the phosphor surface, the bottom surface) may be coated with a reflective or absorptive substance (such as a plastic layer containing pigment or dye). Alternatively, it may be a composite thereof.

■ Hole 3: The cross-sectional shape of the hole 3 may be circular, rectangular, or irregular, but is preferably circular or polygonal. Generally, it is desirable that the size (diameter or side) of the hole is less than or equal to the size (diameter or side) of one pixel. The depth of the hole is suitably 174 or more and less than 20 times the diameter or an equivalent dimension.

Is the cross section of the hole approximately -shaped in the thickness direction?

Alternatively, the sides may be sloping, the bottom may be small and the entrance may be large.

Also, the hole does not necessarily have to be penetrating. especially.

If the side surfaces are inclined and the bottom surface is flat, and both the side and bottom surfaces have high reflectance for the first and second lights, then when the second light exits from the hole, the direction is It has the great effect of not spreading. FIG. 2 is a sectional view showing an example in which the hole does not penetrate.

FIG. 3 is a perspective view of the phosphor plate seen from above in FIGS. 1 and 2. FIG.

[Effect]

The present invention improves the apparent sensitivity of a stimulable phosphor, thereby making it possible to scan a 1'1 reading light beam at a higher speed with a smaller amount of radiation exposure.

The present invention can be used in the same manner as conventional stimulable phosphor plates.

The phosphors filled in the multiple holes accumulate a two-dimensional radiographic image. When a first light beam is applied to read it out, the first light beam that penetrates the filled holes in the phosphor does not penetrate into the opaque material that supports the phosphor. Alternatively, if there are nine reflective layers, the light is reflected there, so even if it is scattered by the phosphor, it will not spread.

Here, the size of the cross section of the first light beam on the surface of the phosphor plate is smaller than the required size of one pixel, or one
The area is smaller than the area covering cells placed in an area larger than the area corresponding to pixels.

Also, the second light emitted by the first light beam cannot penetrate into the material of the plate supporting the phosphor.

Therefore, the resolution of the two-dimensional image in such a case depends on the area of the hole filled with the phosphor, and the size in the thickness direction,
That is, it does not depend on the thickness of the phosphor layer.

Therefore, it was previously considered impossible to reduce the area of the hole and increase the thickness of the phosphor layer. High sensitivity can be achieved while maintaining the resolution of the phosphor plate.

Furthermore, the present invention makes it possible to increase the density of pixels by laminating thin plates with through-holes formed therein using lithographic and etching techniques, which are capable of microfabrication, to form the holes as a support plate. That is.

〔Example〕

FIG. 4 is a perspective view of a phosphor support plate illustrating an embodiment of the present invention.

A stainless steel thin plate (201 to 210) with a thickness of 50 μm and a size of 352 mm x 352 mm has a diameter of 50 μm.
Holes 3 having a diameter of 70 μm were formed in the entire center at a pitch of 70 μm in length and width.

No holes are made at the edge of the thin plate to maintain the strength of the frame.

Hole 3 was formed using conventional gluing and etching techniques.

Ten of these thin plates (201 to 210) were prepared, and the supporting plate 2 was obtained by stacking and fixing the holes at the same positions.

FIG. 5 is a sectional view illustrating an embodiment of a phosphor plate using the above support plate 2.

In the figure, a support plate 2 is placed on a glass plate 6, a separately prepared mixed solution of phosphor and organic binder is dropped onto the support plate 2, and the surface is smoothed with a Teflon rod to remove excess phosphor. was removed and all holes were filled with Phosphor 1.

Barium chloride bromide (BaCIBr:Eu) activated with europium was used as the phosphor l, and epoxy resin was used as the binder.

Further, a support plate 2 filled with fluorescent material was adhered onto the glass plate 6 with an epoxy adhesive, and a protective film 4 on the opposite surface of the support plate 2 was adhered with a polyethylene terephthalate film using the same adhesive.

The phosphor plate thus produced was placed into a cassette insertion section of a medical chest X-ray diagnostic device.

After exposure to X-rays, the surface of the phosphor was sequentially scanned with a semiconductor laser beam while kept in a dark place, and the emitted light was received by a photomultiplier tube for photoelectric conversion.

Here, the wavelength of the semiconductor laser is 780 nm, and the scanning speed is 50 m/sec.

When the photoelectrically converted signals were displayed on a high-resolution cathode ray tube with 256 levels of gradation, a clear chest image was obtained.

The amount of X-ray exposure at this time was sufficient to be 1710 or less, which is the case when photographing with a normal silver halide film.

FIG. 6 is a sectional view illustrating another embodiment of a phosphor plate using the support plate 2 described above.

In this example, only one side of a support plate 2, each filled with a phosphor 1, is adhered to a sheet 5 of polyethylene terephthalate.

In addition, as another example, when stacking thin plates with holes, 2
One side was a thin plate without holes (corresponding to Figure 2). In this case, since there was no leakage when the phosphor was filled into the hole, we conducted a radiation image reading experiment without attaching the 2 protective film.

Similar to the phosphor plate shown in FIG. 6, good X-ray images could be read out.

In the above embodiments, the support plate was formed using a thin plate by forming holes using lithography and overlapping the thin plates, but the support plate was formed using a drill or electric discharge machining to form a plate of the desired thickness.
This may be performed using ultrasonic processing or the like.

The present invention is applicable to any phosphor filled in the holes, as long as it is a stimulable phosphor or a thermal phosphor.

For example, in addition to the examples.

TA such as Li, Na, K, Rh, Cs, Fr, etc.
Group alkali metals and.

With alkaline earth metals such as Be, Mg, Ca, Sr, Ba, and Ra.

Halogen elements such as F, CI, Br, 1 or O, S
, Se, and other chalcogen elements as a matrix, and La, Ce, Pr+ Nd, Pm, Sm, E
u+ Gd, Tb, Dy+ H.

A lanthanide element such as Er+ Tm, yb, or Lu, a transition metal element such as Mo, or a phosphor containing a luminescent center such as TI or Bi can be used.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a stimulable phosphor plate in which the resolution does not deteriorate even if the thickness of the phosphor layer is made thicker than before to increase the sensitivity.

Therefore, clear two-dimensional images of radiation such as X-rays can be obtained with a small amount of radiation exposure.

It can contribute to improving the performance of radiation image reading devices.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, and FIG. 2 is a sectional view of a phosphor plate. FIG. 2 is a sectional view showing an example in which the holes in the support plate do not penetrate. FIG. 3 is a perspective view of the phosphor plate seen from above in FIGS. 1 and 2. FIG. 4 is a perspective view of a support plate for a phosphor illustrating an embodiment of the present invention. FIG. 5 is a sectional view illustrating an embodiment of a phosphor plate using the above support plate. FIG. 6 is a sectional view illustrating another embodiment of a phosphor plate using the above support plate. FIG. 7 is a diagram for explaining the problems of the conventional example, and is a cross-sectional view showing the spread of the reading light beam when it is incident on the phosphor plate. In fig. ■ is a fluorescent material. 2 is a support plate. Reference numerals 201 to 210 denote thin plates of stainless steel mesh constituting the support plate 2. 3 is a hole. 4 is a protective film, which is a polyethylene terephthalate film. Figure 1 Figure 4 Figure 2 Figure 5 Figure 6 Perspective view of the phosphor plate in Figures 1 and 2 Figure 3 Figure 7vIJ

Claims (2)

[Claims] (1) It has a support plate having a plurality of holes in the thickness direction, and a phosphor filling the holes and accumulating a radiation image, and the support plate has a first hole for reading out the phosphor. A radiographic image reading device made of a material that does not transmit light and second light excited by the light, and characterized in that the holes have more than the number of pixels necessary for an image and are arranged uniformly or randomly. Fluorescent plate. (2) A phosphor plate for reading radiographic images, wherein the support plate according to claim 1 includes a portion in which a plurality of thin plates having a plurality of through holes are overlapped in the thickness direction with the through holes aligned.