Fuji Photo Film Company, Limited

Takao Komaki

Seiji Matsumoto

Masanori Teraoka

Kazuo Horikawa

Masamitsu Ishida

Nobuyoshi Nakajima

Hisatoyo Kato

Satoru Honjo

Eiichi Asai

Hirosi Tanaka

Isoji Takahashi

Tomotaka Kozeki

Kozi Shimanuki

Yuma Adachi

In a radiation image recording system wherein a stimulable phosphor carrying a radiation image stored therein is scanned by stimulating rays to emit light in proportion to the radiation energy stored, and the emitted light is converted to an electric signal which is processed and used to reproduce a visible image in a light-sensitive material, a value within the range of 0.2 to 0.5 and two values at least 0.5 different from each other within the range of 0.4 to 2.6 are selected as the reference optical density values of the reproduced image. An image is once recorded in the light-sensitive material by using reference signals representing the reference values, and the optical densities at the image portions corresponding to the reference values are measured. Differences between the measured values and values on a reference gradation curve are corrected so that the sensitivity is equal to the sensitivity on the reference curve at the portion corresponding to the value selected within the range of 0.2 to 0.5, and the gradient is equal to the gradient on the reference curve with respect to the density value range of 0.4 to 2.6.

Gradation correcting method for light-sensitive material

Two or more stimulable phosphor sheets are exposed to a radiation passing through an object under conditions different from one another, and radiation images of the object at least partially different from one another are recorded on the stimulable phosphor sheets. The stimulable phosphor sheets are then scanned with stimulating rays to convert the radiation images into light, which is photoelectrically read out and converted into digital image signals. The digital image signals are subjected to a subtraction processing with respect to the corresponding picture elements of the images, thereby to obtain a signal for forming an image of a specific structure of the object.

Subtraction processing method for radiation images

A stack of many stimulable phosphor sheets and an X-ray tube are positioned with an object intervening therebetween, and moved with respect to each other around a tomographic plane in the object so as to satisfy the linear rule and the geometric rule in the course of exposure of the object to X-rays, thereby storing images of many tomographic planes in the stimulable phosphor sheets in a single recording step. The respective stimulable phosphor sheets are then exposed to a stimulating ray to cause them to emit light, the emitted light is photoelectrically read out, and the obtained electric signals are reproduced as visible tomographic images usable in diagnosis with high efficiency and accuracy. The electric signals may be superposed one upon another and reproduced as an X-ray image of any slice thickness, particularly a slice thickness of 5 mm or more, which is free from interfering shadows.

Method of recording X-ray image

A radiation image recording system having a built-in light source for erasing the fog developing in a stimulable phosphor used in a radiation image recording and reproducing method in which a radiation image is once recorded on a stimulable phosphor sheet and then read out and reproduced into a visible radiation image. The light source is positioned between a section for feeding the stimulable phosphor sheet and a section where a radiation image is recorded on the sheet. The system is also provided with a unit for sending the stimulable phosphor sheet from the radiation image recording section to a sheet receiver or a radiation image information read out and reproducing system.

Radiation image recording system

In a radiation image recording and reproducing method in which a radiation image is once recorded in a stimulable phosphor and then read out and reproduced into a visible image, noise developing in the visible image due to repeated use of the stimulable phosphor is effectively erased by the combined use of first and second erasing steps. The first erasing is conducted to erase the radiation image previously stored in the phosphor, which requires a long period to erase, at an appropriate point of time after the phosphor is once used. The second erasing is carried out quickly to erase the fog, which develops in the phosphor after the first erasing, immediately before the phosphor is to be used for the next radiographic operation.

Noise erasing method in a radiation image recording and reproducing

An apparatus for erasing the fog developing in a stimulable phosphor sheet used for a radiation image recording and reproducing system in which a radiation image is once recorded in the stimulable phosphor sheet and then read out and reproduced on a recording material. The apparatus is arranged so that stimulable phosphor sheets are taken up one at a time out of their reservoir and each is loaded into a cassette used for the recording of a radiation image. It comprises a light source for erasing the fog, which is provided between the aperture of the reservoir from which the stimulable phosphor sheets are taken up and the section at which the sheets are loaded into the cassettes.

Noise erasing apparatus for stimulable phosphor sheet

In radiography, a plurality of radiographic films are used for recording radiographic images of an object viewed from the same direction. For instance, a stack of radiographic films stacked together with intensifying screens is exposed to X-rays passing through an object to record the images on the films simultaneously. Alternatively, the plurality of radiographic films are exposed to X-rays passing through the object one by one with the object held still at a position. The images on the plurality of radiographic films are superposed together by electrical signal processing means to obtain an image having averaged density. Then, the gradient of the gradation of the averaged image is enhanced. The radiographic films may be stacked together with self-supporting intensifying screens to reduce the thickness of the stack of the films and intensifying screens when recording the radiographic images. Further, double-side coated intensifying screens may be used together with the stack of the films to reduce the thickness of the stack of the films and intensifying screens when recording the radiographic images.

Method of processing radiographic image

In a radiographic image recording system in which a stimulable phosphor plate is exposed to X-rays to record a radiographic latent image therein, the stimulable phosphor plate is exposed to stimulating rays thereafter to emit light according to the stored energy of X-rays, and the emitted light is detected by a photodetector and converted to an image signal to be used for finally recording a visible image on a photosensitive film or the like, a plurality of stimulable phosphor plates are used for recording radiographic images of an object viewed from the same direction. The image signals read out from the plurality of stimulable phosphor plates are superposed to obtain an averaged image signal. The averaged image signal is then subjected to a gradation process for enhancing the contrast of the image.

In Reiss chamber method or ionography, or in a method of modification or combination of these methods wherein an electrostatic latent image of an object irradiated with radiations such as X-rays is formed on an insulating image recording layer, a photoconductive material is used as the image recording layer. The charge carried on the photoconductive image recording layer is partly neutralized by the radiations received thereby. In an embodiment, a fluorescent layer is attached to the photoconductive image recording layer to accelerate the neutralization of the charge when the recording layer is exposed to the radiations. In another embodiment, the photoconductive material has a property that the photoconductivity increases as the strength of an electric field applied thereacross increases, and the image recording layer made of such a photoconductive material is uniformly exposed to light simultaneously with or after the irradiation of the radiations.

Method of recording radiographic images

Disclosed is an electrostatic recording method for forming an electrostatic latent image on a dielectric electrostatic recording layer provided on a conductive support. The relationship between the thickness d[.mu.m] and the specific dielectric constant .epsilon..sub.s of the electrostatic recording layer is such that the ratio of d[.mu.m] to .epsilon..sub.s, i.e. d/.epsilon..sub.s [.mu.m], is not larger than 1.65[.mu.m] when the image recorded is of reflection type and not larger than 1.5[.mu.m] when it is of transmission type. The latent image formed on the recording layer is developed by use of electrophotographic liquid developer. Also disclosed is an ionizing radiation image recording method wherein ionizing radiation carrying image information is directed onto a material which generates photoelectrons or a gas which is dissociated upon receipt of the ionizing radiation to an extent corresponding to the intensity of the radiation. In this method, the ratio of the thickness of the electrostatic recording layer to the specific dielectric constant is selected to be not larger than 1.5[.mu.m] when the image is of reflection type and not larger than 1.0[.mu.m] when it is of transmission type.

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Kanagawa, Japan

Takao Komaki