JPS609542B2 - Radiographic image conversion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for converting a radiation image, and more particularly to a method for converting a radiation image using a photostimulable crab photoreceptor.

Traditionally, so-called radiography, which uses silver salts, has been used to obtain radiographic images, but in recent years, due to problems such as the depletion of silver resources on a global scale, radiographic images have been developed without using silver salts. A method has become desirable.

As an alternative to the radiographic method described above, the radiation transmitted through the object is absorbed by a crab photoreceptor, and then this photoreceptor is excited with some kind of energy to transfer the accumulated radiation energy to the crab photoreceptor. A method is being considered in which the crab light is emitted as light, and this crab light is detected and imaged.

As a specific method, a method has been proposed in which a radiation image is converted by using a thermophotogenic crab light body as a light body and using thermal energy as excitation energy (UK Patent No. 1462).
769 and Tokusekki Sho 51-2988 needle number). This conversion method uses a panel in which a thermally reflective grooved light layer is formed on a support, and the thermally reflective grooved light layer of this panel absorbs the radiation that has passed through the subject, responding to the intensity of the radiation. Radiation energy is accumulated, and then the accumulated radiation energy is extracted as a light signal by heating the thermophotonic backlight layer, and an image is obtained based on the intensity of this light. However, since this method heats the accumulated radiation energy when converting it into a light signal, it is absolutely necessary that the panel be heat resistant and not deformed or altered by heat. There are major restrictions on the materials of the photochromic layer and the support.
As described above, the radiation image conversion method using a thermal crab photon as the crab photon and thermal energy as the excitation energy has major drawbacks in terms of application. On the other hand, radiation image conversion methods using electromagnetic waves selected from visible light and infrared rays as excitation energy are also known (US Pat. No. 38
No. 59527).

Unlike the above-mentioned method, this method does not require heating when converting the accumulated radiation energy into a light signal, so the panel does not need to be heat resistant, and from this point of view it is a more preferred radiation image conversion method. I can say it. However, only a few cerium- and samarium-activated strontium sulfide photons (SrS) are used in this method.
Ce, Sm), / europium and samarium activated strontium sulfide phosphor (SrS:Eu,Sm), europium and samarium activated lanthanum sulfide phosphor (E↓Sm), manganese and halogen activated sulfide Zinc, cadmium halo [(Zn,Cd)S:Mn,X
, However, X is a halogen. ing.

In the present invention, the radiation that has passed through the object is absorbed by the crab light body, and then this crab light body is excited with electromagnetic waves selected from visible light and infrared rays, and the radiation energy accumulated in the crab light body is absorbed into the crab light body. The object of the present invention is to provide a practical radiation image conversion method with extremely high sensitivity in a radiation image conversion method for detecting this crab light.

In order to achieve the above object, the present inventors have been searching for crab photons that can be used in the above method.

As a result, {a' steel and lead-activated zinc sulfide phosphor (ZnS:
Cu, Pb), and other europium-activated barium aluminate shark photons represented by the general formula: Ba0.AI2Q:Eu,
and [c' general formula: MOO・xSi02:A (however, M
OO is Ca0, S, Zn0 or mother ○, A is C8, Tb
, Eu. At least one of Pb, Mh, 0.5×
Use at least one phosphor selected from the alkali metal silicate phosphors represented by 32.5);
It has been discovered that the above-mentioned method provides extremely high sensitivity, and the present invention has been completed. The content of activator in these crab photons (for crab photons where the activator is composed of two or more elements, the total amount of those activating elements) is 10 to 1 mole of the crab photon matrix. -6 to 5 x 10-3 gram atoms. The radiation image conversion method of the present invention converts the radiation transmitted through the object into the Zn
S; Cu, Sb crab photon, Bao.N203:Eu crab photon and MOO. , to excite this nectary body with electromagnetic waves selected from long-wavelength visible light of 50 skin meters or longer and infrared rays, to emit the radiation energy accumulated in this nectary body as full-body light, and to detect this crab light. It is characterized by

The radiation image conversion method of the present invention will be specifically explained using schematic diagrams.

In FIG. 1, 11 is a radiation generating device, 12 is a subject, 13 is a radiation image conversion panel having a visible or infrared exhaustible nectar layer, and 14 is a radiation image conversion panel for emitting a radiation latent image as crab light. A light source as an excitation source for, 1
5 is a photoelectric conversion device that detects the crab light emitted from the radiation image conversion panel; 16 is a device that reproduces the photoelectric conversion signal detected by 15 as an image; 17 is a device that displays the reproduced image; and 18 is a light source. This is a filter for cutting the reflected light from the radiation image conversion panel 14 and transmitting only the light emitted from the radiation image conversion panel 13. The 15th display may be of any type as long as it can reproduce the optical information from 13 as an image in some form, and is not limited to the above.

As shown in FIG. 1, when a subject 12 is placed between the radiation generator 11 and the radiation image conversion panel 13 and irradiated with radiation, the radiation passes through each part of the subject 12 according to changes in radiation transmittance. A transmitted image (that is, an image of the intensity of radiation) enters the radiation image conversion panel 13 .

This incident transmitted image is absorbed by the crab phosphor layer of the radiation image conversion panel 13, and a number of electrons or holes are generated in proportion to the amount of radiation absorbed in the phosphor layer. Accumulated at the Tratsub level. That is, an accumulated radiographic image (a kind of latent image) is formed. This latent image is then excited with light energy to become visible. i.e. 50
Electromagnetic waves selected from long-wavelength visible light and infrared rays, which are longer than those of the enemy, are irradiated onto the crab light layer to create electrons or holes accumulated at the trap level, and the accumulated image is emitted as crab light. The strength of this emitted light is proportional to the number of accumulated electrons or holes, that is, the strength of the radiation energy absorbed by the light body layer of the radiation image conversion panel 13, and this optical signal is converted into, for example, a photoelectron. Photoelectric conversion device 1 such as an intensifying tube
5, it is converted into an electrical signal, reproduced as an image by an image reproduction device 16, and this image is displayed by an image display device 17. Next, the radiation image conversion panel used in the radiation image conversion method of the present invention and the excitation light source for emitting the accumulated image as crab light will be described in detail.

The structure of the radiation image converter/channel consists of a support 21 and a phosphor layer 22 formed on one side of the support 21, as shown in FIG. 2-a.

This crab phosphor layer 22 is made of the above-mentioned Z hawk: Cu, Pb phosphor, Ba
0・Mountain 203: Eu crab light body and MOO・xSi02:
It is formed from one or more types of crab photons selected from A-type photons. Next, an example of a method for manufacturing a radiation image conversion panel will be shown below.

First, 8 parts by weight of crab phosphatide and 1 part by weight of nitrification wire are mixed using a solvent (mixture of acetone, ethyl acetate, and butyl acetate) to prepare a coating solution having a viscosity of about 50 centistokes. Next, this coating solution is uniformly applied onto a horizontally placed polyethylene terephthalate film (support), and left to dry naturally for a day and night to form a total of about 300 light beams, which is used as a radiation image conversion panel. . As the support, for example, a transparent glass plate or a thin metal plate made of aluminum or the like may be used. Note that the radiation image conversion panel consists of two transparent substrates 2 such as glass plates as shown in FIG. 2-b.
It is also possible to have a structure in which a crab light layer 22 is sandwiched between 3 and 24 to form a crab light layer 22 of an arbitrary thickness, and the periphery of the crab light layer 22 is sealed.

In the radiation image conversion method of the present invention, the light source for the light energy that excites the photoluminescent layer of the radiation image conversion panel described above has a band spectrum in one or both of the long wavelength visible region and the infrared region. In addition to light sources that emit light with a distribution, He-Ne laser light (63 m), Y
AG laser light (1064mm), ruby laser light (
A light source is used that emits light of a single wavelength, such as 694 nm).

Particularly when using laser light, high excitation energy can be obtained. Among the laser lights, especially He-Ne
More preferably, laser light is used. FIG. 3 shows a tube voltage of 80 KV applied to the ZnS:Cu,Pb crab light body used in the crab light body layer of the radiation image conversion panel of the radiation image conversion method of the present invention.
This shows the change in the intensity of the total light emitted when light energy of different wavelengths is applied after irradiation with p X-rays (so-called excitation spectrum).As is clear from Fig. 3, ZnS:Cu, In the case of Pb light, the wavelength range that can be excited is in the range of 500 to 150 meters, but using excitation light around 75 meters is preferable because the intensity of the emitted light is strong, and for the purpose of the present invention. It turns out that this is good for improving certain sensitivity.
That is, in the case of the ZnS:Cu,Pb crystal, the optimum excitation wavelength is found to be between 600 and 95 m. Table 1 shows the effective excitation wavelengths of the various photons used in the radiation image conversion method of the present invention, and these photons have two bands in their excitation spectrum ranging from 500 to 150 nm. , the peak intensity of the excitation band on the shorter wavelength side is especially strong. For this reason, it is more preferable that the light energy used for excitation is 100 m or less. Table 1, Figure 4 shows a tube voltage of 80 KVp for the ZnS:Cu, Pb light body.
The graph shows the relative change in the amount of light emitted when a photoluminescent sample irradiated with X-rays is divided and excited with excitation light of 75 m and 130 m at regular intervals from immediately after irradiation. Curve a is for excitation at 130 m, and curve b is for excitation at 75 m.

As is clear from Fig. 4, the case of excitation with 130 melons (curve a) is better than the case of excitation with 75 dishes of blood (curve b).
More degenerative (fading). This is because the trap in the region emitted by infrared rays is shallow and the fading phenomenon is significant, so the information storage period is short and it is not very desirable in practice. For example, when obtaining an image, it is often done to scan and excite the crab phosphor layer of the panel with infrared rays, and to electrically process the emitted light. Since it takes a certain amount of time, there is a risk that there will be a difference between the initial and final proposed values even if the same radiation dose is irradiated. For these reasons, it is more desirable for the crab photogen used in the radiation image conversion method of the present invention to have deep traps and be efficiently excited by high-energy light, that is, light with a wavelength as short as possible. As shown, the preferable excitation wavelength range of each of the photons used in the method of the present invention is in the region of 100 m or less, and therefore, there is less fading and the storage capacity of the radiation latent image accumulated in the photon layer is high. It is something. In the present invention, it is necessary to detect the honey light emitted from the crab light body layer as a result of being excited by light energy, but in this case, it is necessary to separate the emitted crab light and the reflected light of the excitation light. This is necessary to improve the S/N ratio.

By the way, a photoelectric converter that receives the crab light emitted from the crab phosphor layer generally has a high sensitivity to light energy with a short wavelength of 60 meters or less. It is desirable to have a spectral distribution in the short wavelength region as much as possible. All of the crab photons used in the present invention have such characteristics. In other words, all of the crab photophores used in the present invention emit light with a main peak at 50 m or less, so they can be easily separated from the excitation light and match well with the spectral sensitivity of the photoreceiver, so they can be efficiently emitted. As a result of being able to receive light, it becomes possible to increase the sensitivity of the image receiving system. Figure 5 shows BaO・Si02:C used in the present invention.
e After irradiating the crab light body with X-rays with a tube voltage of 80 KVp, H
The emission spectrum when excited with e-Ne laser light is shown as an example. As is clear from Figure 5, Europe 0 Si
The peak of the emission spectrum of 02:Ce is 425 nm. Table 2 shows the sensitivity of an example of the radiation image conversion method of the present invention in comparison with the sensitivity of a conventionally known method using SrS:Eu,Sm fluorescent material. In Table 2, the sensitivity is determined by irradiating the radiation image conversion panel with X-rays at a tube voltage of 8 Vp, then exciting it with He-Ne laser light, and collecting the crab light emitted from the phosphor layer. It is expressed as the luminous intensity when received by a photoreceiver (photomultiplier tube with spectral sensitivity S-5), and is expressed as a relative value with the conventionally known method using SrS:Eu,Sm crab photoreceptor set as 1. There is. Table 2 As is clear from the above Table 2, the radiation image conversion methods (No. 2 to Rudder. 25) of the present invention have higher sensitivity than the conventionally known radiation image conversion method (No. 1).

As explained above, the present invention provides a radiation image conversion method with extremely high sensitivity, and has great industrial utility value as a method that replaces conventional radiography.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the radiation image conversion method of the present invention, and FIG.
Figures a and b are cross-sectional views of the radiation image conversion panel used in the radiation image conversion method of the present invention, and Figure 3 shows the excitation spectrum of the ZnS:Cu,Pb crab photoreceptor used in the radiation image conversion method of the present invention. 4 is a graph showing the degeneration property of the ZnS:Cu,Pb crab photon used in the radiation image conversion method of the present invention, and FIG. 5 is a graph showing the degeneration property of the crab photon used in the radiation image conversion method of the invention It is a graph showing an emission spectrum. 11...Radiation generator, 12...Subject, 13...Radiation image conversion panel, 14...
...Light source, 15...Photoelectric conversion device, 16.
... Image reproduction device, 17 ... Image display device, 18 ... Filter, 21 ... Support, 22 ... Backlight layer , 23, 24...
...Transparent support plate. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Radiation transmitted through an object is transmitted through (a) copper and lead activated zinc sulfide phosphor (ZnS:Cu,Pb), (b) general formula:
BaO.Al_2O_3: europium-activated barium aluminate phosphor represented by Eu, and (c) general formula M
IIO・xSiO_2:A (However, MII is CaO, SrO
, ZnO or BaO, A is Ce, Tb, Eu, Pb, M
an alkaline earth metal silicate-based phosphor represented by at least one of n, 0.5≦x≦2.5 (provided that
), (b) and (c) The content of the activator in the phosphors is 10^-^6 to 5 x 10^-^ per mole of the base material.
3 gram atoms), and then this phosphor is excited with electromagnetic waves selected from long-wavelength visible light of 500 nm or more and infrared rays, so that the phosphor accumulates. 1. A radiation image conversion method characterized by emitting radiation energy as fluorescence and detecting this fluorescence. 2. The radiation image conversion method according to claim 1, wherein the wavelength of the electromagnetic wave is 1000 nm or less. 3. The radiation image conversion method according to claim 1 or 2, wherein the electromagnetic wave is a laser beam. 4. The radiation image conversion method according to claim 3, wherein the laser beam is a He-Ne laser.