JPS5824791B2 - Radiographic imaging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation image creation method using electrostatic transfer.

Traditionally, radiography, or X-ray photography, produces image-like blackening by irradiating a silver halide emulsion film (hereinafter simply referred to as a silver salt film) with X-rays that have passed through the subject to reduce the silver in the silver halide emulsion. It forms the density and visualizes the image.

However, although X-ray photography using silver halide film as described above has high X-ray sensitivity, it is generally expensive because it consumes silver, and the development process is complicated and takes a long time. However, there are drawbacks such as the need for careful attention.

To overcome these drawbacks, various methods have been developed that utilize electrophotographic processes to obtain X-ray photographs without using silver salt films.

For example, xerography methods that utilize the sensitivity of a photoconductor to X-rays, ionography methods that utilize the ionization of air or rare gases by X-rays, and electroradiography methods are already known.

Unlike those using conventional silver halide films, all of these methods form images based on electrostatic latent images. It has the advantage of being able to obtain images with a large amount of information on soft tissues such as muscles, keys, stomach, intestines, etc., which have little information, and can eliminate the drawbacks of the silver halide film described above.

However, the photoconductor used in xeroradiography is not necessarily highly sensitive to radiation, and the ionography and electroradiography methods require low pressure in a chamber consisting of opposing electrodes. Alternatively, since -1 is required unless high-pressure gas is sealed in the chamber, there are disadvantages in that it is difficult to select a material for the chamber and the structure is complicated.

Furthermore, in conventional radiographic image creation methods using silver halide films or non-silver halide films, it is common that only one image can be obtained in one imaging session, that is, in one X-ray irradiation.

νHowever, considering recent medical developments, it may be effective to create multiple radiographs at the same time and distribute them to different specialists for diagnosis.

The present invention has been made in view of the above circumstances, and is a radiation therapy system that can easily create high-sensitivity, high-resolution radiographic images, and can also create multiple images at the same time with one X-ray irradiation, if necessary. It provides an image creation method.

This will be explained in detail below using the drawings.

As shown in the drawings, the present invention provides an electrode 1 with high radiation transparency.
and a film 2 that is conductive in the thickness direction and insulating in the lateral direction are placed facing each other with a gap therebetween, and a radiation absorbing liquid 3 is sealed in the gap using a spacer 4 to form a chamber 5. Then, one or more insulating sheets 6 and a conductive support electrode 7 are stacked on the film 2 of the chamber 5 configured in this way, and a voltage is applied between both electrodes 1 and 7. X to the object 8 installed on the 1 side
This is a radiation image creation method in which an electrostatic latent image is formed on an insulating film 6 by irradiating X-rays from a radiation source 9.

The electrode 1 having high radiation transparency is made of, for example, Al.

A thin plate made of metal such as Mg and Be or carbon such as carbon fiber board is suitable, and the electrode thickness is 0.
, 5 or more, and the thickness should be within a range where the absorption of X-rays is not too large.

In addition, the film 2, which is conductive in the thickness direction and insulating in the lateral direction, that is, exhibits conductive anisotropy, is preferably a sheet in which metal particles are uniformly dispersed in a silicone-based synthetic polymer material. 1 at any point in the thickness direction of
Continuity of Ω or less is obtained, and high insulation of 10 9 Ω or more is exhibited between adjacent contacts.

Examples of the radiation absorbing liquid 3 sealed in the chamber 5 include insulating liquids with a large radiation absorption coefficient, such as halogen element liquids, halogenated carbon liquids, or compounds thereof.

Carbon tetrachloride solution (iodine solution), chloroform,
Trichloroethane, tetrachloroethane.

Pentachloroethane, trichlorethylene, tetrachlorethylene, methyl bromide, ethyl bromide, ethylene bromide, tetrabromoethane, chlorobromomethane, chlorobenzene, trichlorobenzene, bromobenzene, cyfuromebenzene, fluorodi, chloromethane, Examples include cyclodifluoromethane, fluorotrichloromethane, and trifluoromonobromomethane, but are not necessarily limited thereto, and mixtures of these compounds can also be used.

The insulating sheet 6 for receiving latent images may be one based on a dielectric film, or one based on paper with a dielectric layer provided thereon. In this case, it is possible to record as is, but when recording a large number of sheets at the same time, a surfactant is added to the back side of the film to prevent peeling discharge when separating stacked sheets into single sheets and frictional charging during sheet handling. It is effective to apply something like this to provide some conductivity.

; Now, the principle of electrostatic latent image formation according to the present invention will be explained.

The X-rays emitted from the X-ray source 9 are modulated by the subject 8 according to the absorption capacity, and then pass through the electrode 1 with high X-ray transparency as X-rays with image information, and the X-rays are transmitted to the interior of the chamber 5. The absorption liquid 3 is reached.

The arriving X-rays are absorbed by the X-ray absorbing liquid 3 and are converted into electron-cation or anion-cation pairs (
charge carriers).

The generated charge carriers move toward the electrode corresponding to each charge without recombining due to the action of the electric field.

That is, the X-ray absorbing liquid 3 becomes imagewise conductive.

Therefore, an image-like electric field intensity distribution is obtained between the conductive anisotropic film 2 and the electrode 7.

By the way, when the applied voltage exceeds a certain threshold value depending on the thickness of the insulating layer, there is a charge transfer from the electrodes to multiple sheets of insulating film sandwiched between two electrodes, and the charge is It is known that a homocharge that has the same charge as the electrode it is in contact with moves a charge proportional to the voltage that exceeds the threshold.

Therefore, when not irradiating X-rays, if the voltage between the film 2 and the electrode 7 is set to be below a threshold value corresponding to the material and thickness of the insulating film 6 sandwiched between them, then when X-rays are irradiated, By making the absorbing liquid 3 conductive, the film 2 and the electrode 7
The voltage between the insulating films 6 and 6 is high.
, 62...6n, an electrostatic latent image is formed.

At this time, since the film 2 is a film made of metal particles uniformly dispersed in a synthetic polymer material, the metal particles make the film conductive in the film thickness direction, and the resolution (in other words, the film 2 to the insulating film 6) is determined, the metal particles can be made smaller and the resolution can be improved.

In this way, each insulating film 60, 6□...
- When the insulating film 6 is peeled off one by one in order to develop the electrostatic latent image formed on the 6n, the latent image is often disturbed by peeling discharge and cannot be put to practical use.

In order to prevent this, it is effective to apply something such as a surfactant to the back surface of the insulating film 6 to give it some conductivity.

In addition, if the electric field passing through the insulating film 6, which has been stacked in large numbers, loses its straightness, problems will arise in terms of resolution, so the insulating film 6 must have sufficient conductivity to allow the electric field to pass through uniformly without being blocked. It is necessary that the surface resistance is 1010~10
A range of 12Ω is desirable.

The electrostatic latent image on the peeled insulating film can be visualized by applying various conventionally well-known electrophotographic development methods, such as powder cloud, cascade, magnetic brush, and liquid development. Be visualized.

As described above, according to the present invention, it is possible to easily obtain high-sensitivity, high-resolution radiographic images, and if necessary, multiple X-ray images can be obtained simultaneously with one X-ray irradiation. Images with good tonal reproducibility can be obtained.

[Brief explanation of the drawing]

The drawings are schematic configuration diagrams showing embodiments of the present invention. 1 is a radiation transparent electrode, 2 is a conductive anisotropic film, 3 is a radiation absorbing liquid, 4 is a spacer, 5 is a chamber, 6
7 is an insulating film, 7 is a supporting electrode, 8 is a subject, and 9 is a radiation source.

Claims (1)

[Claims] 1 An electrode 1 with high radiation transparency and a film 2 made of metal particles uniformly dispersed in a synthetic polymer material and which is conductive in the film thickness direction and insulating in the lateral direction are opposed with a gap between them. A radiation absorbing liquid 3 is sealed in the gap to form a chamber 5, one or more insulating sheets 6 and a conductive support electrode 7 are stacked on the film 2, and then both electrodes are placed at 1°7. A radiation image creation method characterized by irradiating a subject 8 placed on the electrode 1 side of a chamber 5 with X-rays while applying a voltage between them to form an electrostatic latent image on an insulating film 6.