Abstract
The object of the present invention is an cascaded ionizing radiation converter, comprising the first conversion stage, transforming ionizing radiation into non-ionizing electromagnetic radiation, the second conversion stage transforming non-ionizing electromagnetic radiation into an electrical charge, and the third conversion stage transforming the generated electric charge into the change of potential controlling the liquid crystal cell, wherein the first conversion stage is a radioluminescent layer, preferably Lu.sub.2O.sub.3:Eu layer, the second conversion stage is a photoconductive material layer, preferably amorphous selenium or poly (3-hexyl-thiophene) layer, and the non-ionizing electromagnetic radiation emission spectrum of the first conversion stage corresponds with the non-ionizing electromagnetic radiation absorption spectrum of the second conversion stage; And an imaging diagnostic apparatus using cascaded ionizing radiation converter.
Claims
1. The cascaded ionizing radiation converter, comprising the first conversion stage (1) transforming ionizing radiation into non-ionizing electromagnetic radiation, the second conversion stage (2) transforming non-ionizing electromagnetic radiation into an electrical charge, and the third conversion stage (3) transforming the generated electric charge into the change of potential controlling the liquid crystal cell, characterized in that the first conversion stage (1) is a radioluminescent layer, preferably Lu.sub.2O.sub.3:Eu layer, the second conversion stage (2) is a photoconductive material layer, preferably amorphous selenium or poly (3-hexylthiophene) layer, wherein the non-ionizing electromagnetic radiation emission spectrum of the first conversion stage (1) corresponds with the non-ionizing electromagnetic radiation absorption spectrum of the second conversion stage (2).
2. Cascaded ionizing radiation converter of claim 1, characterized in that the non-ionizing electromagnetic radiation emission spectrum of the first conversion stage (1) comprises visible radiation.
3. Cascaded ionizing radiation converter of claim 1, characterized in that the radioluminescent layer thickness of the first conversion stage (1) is within 100-200 m.
4. Cascaded ionizing radiation converter of claim 1, characterized in that the thickness of the photoconductive material layer of the second stage (2) is within 100-200 nm range.
5. An imaging diagnostic apparatus using ionizing radiation, having hybrid structure comprising the upper transparent layer (4) made of a polymer, then the upper electrode layer (5), and, in sequence, the first conversion stage (1) converting the ionizing radiation into non-ionizing electromagnetic radiation, the second conversion stage (2) transforming nonionizing electromagnetic radiation into an electrical charge, and the third conversion stage (3) transforming the generated electric charge into the change of potential controlling the liquid crystal cell, then a polyimide layer (6), the lower electrode layer (7), and the lower transparent layer (8) made of a polymer or of glass, characterized in that the first conversion stage (1) is a radioluminescent layer, preferably Lu.sub.2O.sub.3:Eu layer, the second conversion stage (2) is a photoconductive material layer, preferably amorphous selenium or poly (3-hexylthiophene) layer, wherein the non-ionizing electromagnetic radiation emission spectrum of the first conversion stage (1) corresponds with the non-ionizing electromagnetic radiation absorption spectrum of the second conversion stage (2).
6. Imaging diagnostic apparatus of claim 5, characterized in that the non-ionizing electromagnetic radiation emission spectrum of the first conversion stage (1) comprises visible radiation.
7. Imaging diagnostic apparatus of claim 5, characterized in that the radioluminescent layer thickness of the first conversion stage (1) is within 100-200 m.
8. Imaging diagnostic apparatus of claim 5, characterized in that the thickness of the photoconductive material layer of the second conversion stage (2) is within 100-200 nm range.
9. Imaging diagnostic apparatus of claim 5, characterized in that the upper electrode layer (5) and the lower electrode layer (7) are made of indium-tin oxide (ITO).
Description
[0011] Exemplary embodiments of the invention have been presented in the drawings, wherein
[0012] FIG. 1 is a schematic diagram of the cascaded ionizing radiation converter according to the present invention,
[0013] FIG. 2 is a schematic diagram of the imaging diagnostic apparatus according to the invention, while
[0014] FIG. 3 represents the chart illustrating of the intensity variation of the light transmitted by the ionizing radiation converter as the result of cascaded conversion.
EXAMPLE 1
[0015] FIG. 1 shows the schematic representation of the cascaded ionizing radiation converter being the first embodiment of the present invention. The radiation cascaded converter consists of three conversion stages constituting separate layers in contact with each other. The first conversion stage 1 is used for converting the ionizing radiation into non-ionizing electromagnetic radiation. In the present embodiment, the first conversion stage 1 is a radioluminescent layer made of Lu.sub.2O.sub.3:Eu material 100 m thick. The ionizing radiation in the form of x-rays with 5 keV to 350 keV energy is absorbed upon reaching the first conversion stage, and, as the result, non-ionizing electromagnetic radiation of 610 nm wavelength is generated. The electromagnetic radiation generated at the first conversion stage 1 is then cast upon the second conversion stage 2 that assumes the form of the photoconductive layeramorphous selenium, 150 nm thick. The electromagnetic radiation from the first conversion stage 1 is absorbed by the amorphous selenium layer, which results in generation of electron-hole pairs influencing the change in electric field applied to the Converter. The electric field generated on the second conversion stage 2 is applied to the third conversion stage 3 that represents the screen of the cascaded ionizing radiation converter, assuming the form of liquid crystal cells of the twisted nematic (TN) type. Applying electric voltage to a liquid crystal cell results in twisting the crystals, which results in the liquid crystal cell transmission change from fully transparent to fully impermeable for electromagnetic radiation of the visible spectrum. Due to the implementation of multistage conversion, the cascaded ionizing radiation converter presented in the present embodiment of the invention is characterized with increased resolution as compared to the currently used solutions with a-Se layer only. Furthermore, using two thin layers on the first conversion stage 1 and on the second conversion stage 2 did not influence the reduction of transmittance of the whole system. Using only three layers, on the other hand, determines the necessity to use production technologies of lower requirements, thus reducing the production time and cost of such converter. Furthermore, the converter according to the present embodiment requires lower x-ray radiation energy for successful imaging. The above advantages are confirmed by research results presented in FIG. 3, where the chart illustrating the intensity variation of the light transmitted by the ionizing radiation converter as the result of cascaded conversion is presented. Three-stage conversion of ionizing radiation causes change of the threshold voltage from U1 to U2, which results in darkening the given liquid crystal cell due to liquid crystals twisting.
EXAMPLE 2
[0016] FIG. 2 represents a schematic diagram of the imaging diagnostic apparatus using ionizing radiation, being the second embodiment of the present invention. The imaging diagnostic apparatus is of hybrid structure, i.e. asymmetric, and is characterized with layered structure. The first layer is the upper transparent layer 4 made of PVK (polyvinylcarbazole) polymer 100 m thick. The polymer is transparent for x-rays. Under the upper transparent layer 4, is the upper electrode layer 5, made of indium-tin oxide (ITO) from 50 to 100 nm thick, which is commonly known in the art. Then there is a three-layer cascaded ionizing radiation converter, equivalent to the one presented in the first embodiment of the invention. The radiation cascaded converter consists of three conversion stages constituting separate layers in contact with each other. The first conversion stage 1 is used for converting the ionizing radiation into non-ionizing electromagnetic radiation. In the present embodiment, the first conversion stage 1 is a radioluminescent layer made of Lu.sub.2O.sub.3:Eu material 100 nm thick. The ionizing radiation in the form of x-rays projected onto the first conversion stage 1 is absorbed in the layer, and, as the result, non-ionizing electromagnetic radiation of 610 nm wavelength is generated. The electromagnetic radiation generated at the first conversion stage 1 is then cast upon the second conversion stage 2 which assumes the form of a photoconductive layer of poly(3-hexylthiophen) 200 nm thick. The electromagnetic radiation from the first conversion stage 1 is absorbed by the poly(3-hexylthiophen) layer, which results in generation of electron-hole pairs constituting the electric field. The next layer is the third conversion stage 3 that represents the screen of the cascaded ionizing radiation converter, assuming the form of liquid crystal cells of the twisted nematic (TN) type. Below, there is a polyimide layer 50-100 nm thick, whose task is to orient the output layer comprising liquid crystal cells. The next layer is the lower electrode layer also made of indium-tin oxide (ITO) from 50 to 100 nm thick. The last layer is the lower transparent layer made of glass, being the mechanical protection. So created hetero-structure is duplicated and manufactured in the form of a two-dimensional matrix, which allows for x-ray imaging of objects. The electron-hole pairs generated on the second conversion stage 2 are separated in the result of application of fixed voltage between the upper electrode layer 5 and the lower electrode layer 7, which causes control voltage increase. As the result, the liquid crystals on the third conversion stage 3 are twisted and the single cell goes dark. The embodiments of the imaging diagnostic apparatus presented in this example are characterized with simple structure and uncomplicated manufacturing process. The application of a polymer and ITO based electrodes enabled, apart from the possibility to control the liquid crystal cell orientation, minimization of ionizing radiation absorption on these layers. The thickness of the first conversion stage 1 and the second conversion stage 2 layers influence the increase of the diagnostic apparatus sensitivity. Furthermore, the apparatus according to the present embodiment requires lower x-ray radiation energy for successful imaging.
