JPS6011836A - Radiation image converter - Google Patents

Abstract

PURPOSE:To execute the photographing read of a radiation image by providing a radiation energy accumulating fluorescent plate in parallel to an output window in a vacuum vessel, and providing a photoelectric surface for converting photoelectrically a bright light scanned by a read light and emitted from the rear side, on an incident window. CONSTITUTION:X-rays 51 for forming an X-ray image transmit through an incident window 52 of a vacuum vessel 50, are made incident on a radiation energy accumulating fluorescent plate 57, and accumulated. The read luminous flux emitted from a luminous flux supplying device 60 passes through an output window 55 through a lens 72 and a vibrating mirror 58, and scans the fluorescent plate 57. Emitted bright light 62 is made incident on a photoelectric surface 53 of the rear side of the incident window 52, and a generated secondary electron is detected by a photoelectron detecting element 56. In such a way, the photographing read of a radiation image is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation image conversion apparatus suitable for use, for example, in performing medical diagnosis using radiation.

[Technical background of the invention and its problems]

Conventionally, to obtain radiographic images, there has been a direct imaging method that uses an intensifying screen and a silver halide film, and an indirect method that uses an X-ray image intensifier to capture the output surface light image on a 100 mm or 35 mm silver halide film. Photography methods were used.

Recently, companies such as Kodak and Fuji Film have developed a method of forming a radiation latent image on a stimulable fluorescent surface, and then mechanically scanning the Rede beam and using a condensing device and a photomultiplier to generate an electrical image. A method has been proposed in which the signal is converted into a signal and reproduced on a television monitor or film for diagnosis (USP No. 3,859,527, JP-A-55
-15025 Publication, Video Information April 1982 issue).

However, with the above-mentioned direct imaging method, problems such as the depletion of silver resources on a global scale have been raised, and in the indirect imaging method, the shape of the X-ray incident surface of the X-ray image intensifier is curved, reeded, and There was a problem that the effective surface could not be made into a square or rectangle.

In contrast, Fu±Film Co.'s method of forming a radiation latent image on an accumulative (also called volatile) fluorescent surface and reading it with a Rede beam reduces the patient's exposure dose, has a flat Xa incident surface, and is effective. It has the advantage that the surface can be any square or rectangle, but it also has its drawbacks.

Now, with reference to Figures 1 to 3, I will explain the above-mentioned method of Fuji Film Co., Ltd. (Eizo Information, April 1982 issue, No. 4).
(See page 09). In FIG. 1, X-rays 2 emitted from an X-ray tube 1 pass through a human body 3, reach an imaging plate 4, and form an X-ray latent image. As shown in FIG. 3, this imaging plate 4 is made by coating a support 31 with rhodanide crystals, which are stimulable phosphors, in a highly packed manner.
The entire film is taken in a dark room. And X
The imaging grade 4 on which the line latent image was recorded was placed in a dark room as shown in FIG.
0X) 23 is one-dimensionally scanned by a vibrating mirror 24.

Then, blue fluorescent light is emitted from the imaging plate 4, so this light is collected at one point by the optical fiber 25 and extracted in time series by the photomultiplier 26 as a stain signal 27. The other scanning of the imaging plate 4 is performed by rotating the roller 22 of the carriage 21 at a constant speed.

The electrical signals read in this way are processed by a high-speed image processor 6, a computer 7, and a magnetic memory 8, recorded on a suitable film 10 by a high-precision image recorder 9, and processed by an automatic processor 11. A diagnostic X-ray photograph 12 is obtained.

The process of recording, reading and erasing the imaging plate 4 is shown in FIG. Figure 6) shows an unenlarged imaging plate, and Figure 6) shows a state in which an X-ray image has been recorded. When the X-ray quantum 34 is incident on the stimulable fluorescent surface 32, the energy is accumulated in the crystal, 33 indicates an unaccumulated state, and 34 indicates an accumulated state. Next, as shown in FIG. 4C, when 6330X Rade light 36 is irradiated, the X-ray energy accumulated in the stimulable fluorescent surface 32 is extracted as blue fluorescent light 37.

After the reading is completed, the entire surface of the imaging grade 4 is irradiated with light 38 again, so that the X-ray latent image is completely erased.
As shown in (,) in the same figure, it returns to the same unused state as (,).

However, the conventional system as described above has a serious drawback in that it cannot be read immediately after photographing.

[Purpose of the invention]

A fifth object of the present invention is to provide a radiation image converting device that can be read immediately upon imaging, and in which the radiation image converting section has a flat, rectangular effective surface.

[Summary of the invention]

This invention has one or two windows that transmit either or both of radiation and light in the visible to infrared wavelength range, and at least one of the windows is formed approximately perpendicular to the incident direction of the radiation. a radiation energy accumulating phosphor plate disposed approximately perpendicularly to the incident direction of the radiation at one location on the outside or inside of the window; and a radiation energy accumulating fluorescent plate formed on the inner surface of the vacuum container. a photocathode that emits photoelectrons when excited by the light emission of the stimulable fluorescent plate; and a photoelectron that is arranged in a vacuum container to capture the photoelectrons emitted from the photocathode and converts them into an electrical signal according to the amount of captured photoelectrons. The radiation image converting device is equipped with a detection element and can read out radiation images almost simultaneously with storage, or can store radiation images for an appropriate period of time and then read them out.

[Embodiments of the invention]

The radiation image converting apparatus of the present invention is constructed as shown in FIG. The concave entrance window 52 and the flat output window 55 are arranged facing each other at a predetermined interval, and transmit radiation such as X-rays and light in the visible to infrared wavelength range, or both. It is formed substantially perpendicular to the incident direction of the image, for example, the X-ray image 51.

Inside the output window 55, a radiation energy storage fluorescent plate 2 is arranged substantially perpendicular to the direction of incidence of the X-rays 51. As shown in FIG. 5 (not shown in an enlarged scale), a stimulable phosphor 63 is provided on a thin glass substrate 64 that transmits visible to infrared light. The type of phosphor 63 will be described later.

Further, on the inner surface of the entrance window 52, the stimulable fluorescent plate is provided.
A photocathode 53 is formed that is excited by the light emission of Ll and emits photoelectrons. In order to capture photoelectrons emitted from the photocathode 53, a photoelectron detection element 56, such as a secondary electron multiplier, is disposed in the vacuum chamber 50 near the side wall 54.
is installed. This photoelectron detection element 56 converts into an electric signal according to the amount of captured photoelectrons, and is connected to the negative side of a power source 71 outside the vacuum container, and one side of this power source 7 is connected to the side wall 54. has been done. In addition, the vacuum container - [1
On the outside of the output window side, a light beam supply device 60 such as a He-Ne laser device that emits a narrow light beam such as a laser beam, a lens 72, a vibrating mirror 58, and a flash lamp 61 are arranged at predetermined positions. ing.

Furthermore, the surface of the stimulable fluorescent plate 57 (photocathode 5) shown in FIG.
3 side), as shown in FIG.
may be formed. This color selection filter (filter film 65)
It is a filter film having spectral transmission characteristics that allows the emitted light 62 of the stimulable phosphor plate L) to pass through and prevents the reading light beam 59 from passing through, and is intended to prevent the reading light from being captured as a signal.

In the above case, the stimulable phosphor 63 constituting the stimulable phosphor layer 1 is often made of halide, which is mixed with a binder and coated to a thickness of about 200 to 1000 .mu.m. Examples of halides include (Bao, ssMga, 1sCao
, 1s) FBr/Eu (10), BaFCA/Eu
(10), BaFC6/Ca (10), BaFBr
/Eu(8X10), (Bao, 9, Mgo, 1)FBr/Eu(10), =
3゛(Bao, 7, Cao, 3) FBr/Eu (3X1
0), BaFB2/Co (10), Tb (10)
Or (BaFBrO, 113, Li13r0.01
, htBr5 o, ol)/Eu (5 mol), etc. For example, BaFC4/Eu (10-') has an emission spectrum 66 with a peak wavelength of 3800X and an afterglow of several 100 μsec as shown in Figure 7. That's short.

Further, the stimulable phosphor 63 generates light emission proportional to the radiation image intensity accumulated by light having a wavelength longer than 5000X. And 5oo.

Similarly to X, a He--Ne gas laser oscillator is inexpensive and easily available as a means for obtaining a thin light beam in a long wavelength region. The wavelength 68 of the Ha-Ne gas laser is 6330X
The purpose of this invention can be fully achieved.

Further, in this invention, the emitted light 62 from the stimulable phosphor plate ν read out by the reading beam is converted into photoelectrons at the photocathode 53, and the photocathode 53 is, for example, 5b-CIl,
Spectral sensitivity characteristics 67 made of materials such as 5b-Cs-
has a peak sensitivity around 4000X, has almost no sensitivity above 50001X, and hardly emits photoelectrons with respect to the oscillation light 68 of the He-No gas radar. Therefore, the read light will not be mixed into the output electrical signal.

However, as the photocathode 53, for example, Sb-Cs-
When -Na or the like is used, since it has sensitivity to red wavelengths, a method is used in which the color selection filter film 65 is used to block the reading light.

The color selection filter film 65 is made of a blue inorganic coloring material, t
Hacopardo blue, cerulean blue, chromium oxide, T
Examples include iO2-ZnO-Coo-NiO pigments. Moreover, when the glass substrate 64 and the color selection filter film 65 are to be used together, a B-370 color glass filter manufactured by Hoya Glass Co., Ltd. may be used.

The entrance window 52 is made of borosilicate glass, helium, aluminum, titanium, or Ni.

Cr, Co, Fe, Mo1T'aXW, Pd, Zr, A
g.

It is made of at least one thin plate selected from Au or an alloy plate containing Au as a main component.

Now, in the radiation image conversion apparatus of the present invention as described above, during operation, an incident radiation image, for example, an X-ray image 51
is accumulated on a stimulable phosphor plate 57 disposed within the vacuum vessel LA through the entrance window 52, the vacuum vessel side wall 54, and the output window 55 that transmits visible to infrared light. Thereafter, after an arbitrary period of time has elapsed, a luminous flux supply device 60 such as a He-Ne laser device that emits a narrow light beam such as Rede light, for example.
When the reading light beam 59 sent from the oscillating mirror 58 scans the surface of the stimulable phosphor plate 57, accumulated light is detected from a part of the stimulable phosphor plate 57 that is irradiated with the scanned light beam 59. Emitted light 6 whose intensity is proportional to the radiation image intensity
Releases 2. The emitted luminescent light 62 is captured by a photocathode 53 formed on the inner surface of the entrance window 52, and photoelectrons proportional to the intensity of the incident luminescent light 62 are emitted.

The luminescent light 62 emitted at one point is emitted at a wide angle according to Land-Ritt's law, but because the photocathode 53 for capturing is formed over a wide area, it is converted into photoelectrons very efficiently. be done. The emitted photoelectrons are formed on the inner side wall 54 of the vacuum container, and are captured by the photoelectron detection element 56, which has a higher potential than the photocathode 53, and outputs an electrical signal with a strength proportional to the amount of captured photoelectrons. . The incident radiation image 51 is accumulated on the stimulable phosphor plate 57, and the radiation image accumulated on the stimulable phosphor plate 57 is sequentially read out by the scanned light beam 59 for the purpose of reading, and the photocathode 53 is converted into an electrical signal by Then, the accumulated radiographic image is divided into 1/2 by, for example, 525 scanning lines.
If one image is displayed at a rate of once every 30 seconds, it becomes possible to view radiation images continuously on a television using the current standard television system.

Furthermore, if the purpose is to perform digital image processing on an incident radiation image, the signal-to-noise ratio of the electrical signal output of the radiation image conversion device of the present invention is influenced by quantum noise that depends on the quantum number of the incident radiation image. Ru. tb quantum noise causes a reduction in the signal-to-noise ratio. Therefore, in the radiation image conversion apparatus of the present invention, an incident X-ray image is converted into a stimulable fluorescent plate for a certain period of time.
57 and read out after increasing the quantum number, it is possible to reduce quantum noise and obtain an electrical signal with an excellent signal-to-noise ratio. Electrical signals with excellent signal-to-noise ratios are converted into digital signals in multiple stages with high probability. Therefore, minute changes in the radiation image are accurately converted into digital signals. Radiation images with slight density differences can be identified.

Furthermore, when reading out after sufficient accumulation, a high reading speed is not required, making it possible to increase the number of scanning lines and obtain an image with high resolution.

Conventional X-ray TV systems using an X-ray image intensifier and a stimulable image pickup tube cannot achieve a wide dynamic range because the stimulable image pickup tube is saturated with a signal current of a few microamperes due to high signal light. However, since the radiation image conversion apparatus of the present invention does not use a thin photoconductive film, it does not saturate even if a signal of four orders of magnitude or more is obtained relative to the noise level. Therefore,
Images with a wide dynamic range not available with conventional XmTv systems are obtained. Also, accumulative! When the stimulable phosphor 63 forming the light plate 63 is unable to completely read the accumulated radiation image with the light and accumulates minute energy, the stimulable phosphor 63 is installed at a position opposite to the top of the stimulable phosphor. The remaining energy is erased by the flash-emitting lamp 61. This residual energy can also be thermally eliminated.

[Modified example of the invention]

Figures 8 to 14 show various variables of this invention.

This is an example, and the same effect as the above embodiment can be obtained.

In the case of FIG. 8, a stimulable phosphor plate is formed on the inner surface of the exit window consisting of an optical fiber plate 66 which constitutes a part of the vacuum vessel. In this case, the optical fiber 7' rate 66 is irradiated with the reading light beam 59 from outside the output side of the vacuum container, and the optical fiber 7' rate 66 is
The light guide effect of the fiber grating 66 causes the light beam 59 to reach the storage phosphor surface. Then, the accumulated image is emitted and converted into photoelectrons at the photocathode 53, the photoelectrons are captured by the photoelectron detection element 56, and the radiation image 51 is taken out as an electrical signal. In addition, the remaining accumulated energy that has not been released is radiated by a seven-light emitting lamp 61 provided within the vacuum container.

In the case of FIG. 9, a stimulable fluorescent plate is formed on the inner surface of a radiation entrance window 52 forming a part of the vacuum container. This embodiment allows different information to be read out from both sides of the stimulable phosphor plate.

In the case of FIG. 10, when the number of photoelectrons emitted from the photocathode 53 is small, the photoelectrons are multiplied by providing a secondary electron multiplier surface 67 before the photoelectron detection element 56. This is a device that made it possible to obtain

In the case of FIG. 11, the reading light beam 59 in the modified example shown in FIG. 9 is incident from the front direction of the XIfil entrance window 52, and the X-ray entrance window material used in this modified example is must be able to transmit not only X-rays but also visible to infrared light.

For example, borosilicate glass may be used.

In the case of FIG. 12, a stimulable fluorescent plate 57 is formed outside the output window 55. Therefore, it is possible to prevent the reading light beam 59 from being scattered by the output window 55 and deteriorating the image quality.

In the case of FIG. 13, the stimulable fluorescent plate 57 is
is formed on the outer front surface of the In this case, the X-ray entrance window 62 only needs to transmit visible to infrared light, and does not need to transmit X-rays.

In this modification, the reading light beam 59 is free from the influence of forward X-ray scattering at the X-ray entrance window 52.
Since this method does not require transparent glass or ceramic, the influence of light scattering is eliminated and high image quality can be obtained. Furthermore, since the X-rays are directly incident on the stimulable phosphor plate, it is also possible to use low-energy X-rays. It is also possible to alternately use several types of stimulable fluorescent plates.

In the case of FIG. 14, a flying spot scanner 69 is used as the reading moonlight beam 59 without using a laser beam or the like. This flying spot scanner 6
9 is optically coupled to the stimulable fluorescent plate 57 by an optical fiber grating 68. And the phosphor 7 used in the flying spot scanner 69
For 0, use one whose emission spectrum has a long wavelength. For example, ZnO/Zn, (Zn, Cd) S/
Ags Ni, ca 2028/'rb 1La2
o□S/'rb% (YXGd)02S/Tb
%Y3At501□/CL etc. are available, Y3At501
The peak wavelength of the emission spectrum of □7ct is 5300X, and the afterglow is several hundred nanoseconds. This can be used for multiple purposes as a reading light.

In the case of FIG. 15, it is a triangular vacuum vessel in which the entrance window 52 is inclined with respect to the direction of incidence of the Xa image 51.

〔Effect of the invention〕

According to this invention, the following excellent effects can be obtained.

■ Can be read immediately after shooting.

(2) The radiation image conversion section is flat and has a rectangular effective surface.

■ Accumulative fluorophores are highly sensitive and require less radiation exposure to patients.

■ Since the accumulation time can be selected, it is possible to reduce quantum noise.

(2) Since the device of the present invention has a simple structure, it is easy and inexpensive to manufacture.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventionally used radiographic imaging device, Fig. 2 is a perspective view showing the structure of an image reader used in the device shown in Fig. 1, and Fig. 3 is the device shown in Fig. 1. FIG. 4 is a cross-sectional view showing a radiation image conversion device according to an embodiment of the present invention, and FIG. 6 is a cross-sectional view showing a modified example of the stimulable phosphor used in the device; FIG. 7 is a sectional view showing the relative luminance of the stimulable phosphor and the photocathode in the device of FIG. Characteristic curve diagrams showing relative sensitivity, and FIGS. 8 to 15 are cross-sectional views showing modifications of the present invention. 50... Vacuum container, 5... X-ray image (radiation image),
52...Incidence window, 53...Photocathode, 54...Side wall, 55...Output window, 56...Photoelectron detection element, E.
... Accumulative fluorescent plate, 58... Vibrating mirror, 59...
Reading light beam, 60... Luminous flux supply device, 61...
・Fludge - Luminous lamp, 63... Accumulative phosphor, 6
4...Glass substrate, 65...Color selection filter membrane. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2-191 Figure 3 Figure 4 Ram Figure 5 Figure 6 Figure 7 Figure 8 Figure 12 Figure 14 Figure 15

Claims (1)

[Claims] 0) It has one or two windows that transmit either or both of radiation and light in the visible to infrared wavelength range, and at least one of the windows faces the direction of incidence of the radiation. a radiation energy accumulating phosphor plate disposed on either the outside or the inside of the window facing the direction of incidence of the radiation; a photocathode that emits photoelectrons when excited by the light emission of the stimulable fluorescent plate; and a photoelectron that is arranged in a vacuum container to capture the photoelectrons emitted from the photocathode and converts them into an electrical signal according to the amount of captured photoelectrons. 1. A radiation image conversion device, comprising: a detection element, and converts a radiation image into an electrical signal. C2) The radiation image conversion device according to claim 1, wherein the stimulable phosphor plate is formed inside a window that transmits radiation. (3) The radiation conversion device according to claim 1, wherein the stimulable phosphor plate is formed inside the window that transmits visible to infrared light. (4) The radiation image conversion device according to claim 1, wherein the stimulable phosphor plate is formed outside the window that transmits visible to infrared light. (5) The radiation image conversion device according to claim 1, wherein the stimulable phosphor plate is formed outside the window that transmits the radiation and visible to infrared light. (6) The radiation image conversion device according to claim 1, further comprising a scannable light beam supply device for reading the radiation image accumulated on the stimulable phosphor plate outside the vacuum container. (7) The above-mentioned stimulable fluorescent plate is not made of rhodanide crystals, and its wavelength is shorter than the spectrum of the light beam that can be scanned to read the radiation image in which the maximum value of the fluorescent light is accumulated. A radiation image conversion device according to claim 1. (8) The radiation image conversion device according to claim 1, wherein the spectrum of the scannable light beam for reading the radiation image accumulated on the stimulable phosphor plate is in a longer wavelength region than 5000X. (9) The radiation image conversion apparatus according to claim 1, wherein the photoelectron detection element is a secondary electron multiplier. 00) The window that transmits the radiation is made of borosilicate glass, beryllium, aluminum, titanium, NlXC.
r, Co, Mo, W, Zr1 PdsAg, Ta,
The radiation image conversion device according to claim 1, which is formed of at least one type of plate selected from Au or an alloy metal plate containing Au as a main component. α Force The radiation image conversion device according to claim 1, wherein a color selective optical filter film is interposed between the stimulable phosphor plate and the photocathode. (6) The radiation image converting device according to claim 11, wherein the color selective optical filter film has a property of transmitting almost all of the fluorescent light from the stimulable phosphor plate and hardly transmitting reading light. 13. The radiation image conversion apparatus according to claim 12, wherein the color selective optical filter film has a property of cutting off a spectrum having an intensity of 5 degrees or more on the short wavelength side of the emission spectrum of the reading light. α→ The radiation image conversion device according to claim 1, wherein the photocathode is disposed at a position facing the stimulable fluorescent plate. (g) The radiation image conversion device according to claim 1, wherein the stimulable fluorescent plate is formed on one surface of a light-transmitting substrate. a. The radiation image conversion device according to claim 1, wherein the window that transmits visible to infrared light is formed of an onotic fiber plate. (b) Claim 1, wherein the stimulable phosphor plate is formed inside the onotic fiber grate.
The radiation image conversion device according to item 6. α-barrel The radiation image conversion device according to claim 1, wherein the spectral sensitivity of the photocathode hardly matches the emission spectrum of the read light. (to) The radiation image converting device according to claim 18, wherein the spectral sensitivity of the photocathode has a characteristic of cutting off a spectrum having an intensity of 5 or more on the short wavelength side of the emission spectrum of the reading light. A radiation image converting device according to claims 2 and 5, wherein a metal light reflecting layer is formed on the opposite side of the scanning surface for reading the radiation image accumulated by the stimulable phosphor plate. el ゝThe radiation image conversion device according to claim 6, wherein the light beam supply device is a Raded device. (2) The radiation image conversion device according to claim 21, wherein the laser device is a He-No radar device. 7) The radiation image converting device according to claim 6, wherein the light beam supplying device is a flying spot scanning device. (c) The radiation image conversion apparatus according to claim 1, further comprising a seven-lash light emitting lamp for erasing the radiation image accumulated on the stimulable fluorescent plate. (c) The radiation image converting apparatus according to claim 24, wherein the flood-emitting lamp has an emission spectrum in a longer wavelength region than 50,001.