JP2811245B2 - X-ray image reading method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reading an X-ray image recorded on an X-ray photosensitive material.

[0002]

2. Description of the Related Art In radiographic diagnosis, (1) the exposure dose is as small as possible, (2) the image has a high contrast to facilitate identification of the subject, and (3) various parts of the subject. It is usually required that the allowable width of the X-ray exposure is large so as to cover the problem. This X
In radiographic diagnosis, an X-ray image is recorded directly or indirectly on an X-ray photosensitive material such as an X-ray film, and diagnosis is made by observing the image recorded on the X-ray photosensitive material.

Further, in recent years, X-ray films have been used not only as observation materials for visual observation but also as detection materials for obtaining image signals by optically detecting them.
It is also used for diagnosis. That is, there is known an X-ray image reading method in which a film on which an image is recorded is irradiated with reading light, reflected light or transmitted light from the film is photoelectrically read, and the image is converted into a digital image signal. I have. In this film image reading method, a film digitizer is used as an apparatus for performing the reading.
In this method, a light beam such as a laser beam is scanned on a film, and reflected or transmitted light from the film is detected by a photodetector to obtain a time-series image signal. And irradiate the CC
There are various types such as a one-dimensional sensor such as a D-line sensor that sequentially reads light from a film. In any case, the digital image signal read from the film can be subjected to image processing by a computer or the like, thereby performing various processes such as gradation processing and frequency processing,
A desired image can be observed by displaying the processed image signal on a display unit.

Therefore, for the purpose of diagnosis, the X-ray image information of the object is once recorded on an intermediate medium such that the average γ (the ratio of the change ΔD in the image density to the small change ΔE in the exposure amount) becomes 0.3 to 1.5. An X-ray processing method for processing and reproducing image information recorded on the intermediate medium has been proposed by the present applicant (JP-B-61-5193). This X-ray photographic processing method uses the above-described X-ray image reading method, and as a feature, in the above-described configuration, the allowable width of X-ray exposure is increased by using a soft-tone photographic film having a low average γ as an intermediate medium, It makes it easy to record a wide range of data. The recorded image information is subjected to image processing such as gradation processing for converting γ and edge enhancement processing for converting the density near the boundary so as to easily identify the boundary (edge) of each part and increasing the contrast. Thus, it is possible to reproduce an image having desired characteristics.

[0005]

However, producing an X-ray photosensitive material having a wide dynamic range as used in the above method involves a practically difficult problem.
Further, even if an X-ray photosensitive material having a wide dynamic range is produced, the grains constituting the emulsion layer are poor in graininess because large grains having high sensitivity and small grains having low sensitivity are mixed.

An object of the present invention is to provide an X-ray image reading method capable of reading X-ray image information having a wide dynamic range.

[0007]

The X-ray image reading method of the present invention comprises at least a support and a plurality of layers including two or more emulsion layers having different sensitivities and different colors. In the method of reading an X-ray image recorded on an X-ray sensitive material, the X-ray sensitive material is scanned with a plurality of reading lights having wavelengths that are absorbed by respective colors of the two or more emulsion layers. By detecting light from the X-ray photosensitive material when scanning with the reading light, two or more digital image signals indicating X-ray image information for each emulsion layer are obtained, and from these two or more digital image signals, It is characterized by constructing an image signal having a wider dynamic range than each image signal.

As a material for the support, a plastic film such as polyethylene terephthalate can be used. 2
Each or more of the emulsion layers comprises a binder such as gelatin which contains and supports silver halide in a dispersed state. Further, a protective film made of gelatin or the like may be provided in order to physically and chemically hold the emulsion layer.

The following methods can be used to change the sensitivity of each emulsion layer. One method is to vary the grain size of the silver halide contained in the emulsion layers for each emulsion layer. Thereby, the dynamic range of the image can be widened. Another method is to color the low-sensitivity layer with a colorant that absorbs light emitted from the intensifying screen when an intensifying screen is used. At this time, the low-sensitivity layer must be on the side far from the surface of the light-sensitive material, that is, on the side in contact with the support. Another method is to change the content of the sensitizer contained in each emulsion layer when the emulsion layer contains a sensitizer. X is a sensitizer.
There are a chemical sensitizer that increases sensitivity in a region of intrinsic sensitivity without particularly changing the photosensitive wavelength region of the radiation-sensitive material, and a spectral sensitizer that newly generates sensitivity in a spectral region other than the intrinsic sensitivity.

Each emulsion layer is not particularly limited as long as it has a known color such as yellow, magenta or cyan.

The intensifying screen used in combination with the X-ray sensitive material as described above basically comprises a support and a phosphor layer provided thereon. Examples of the body material include a plastic film such as polyethylene terephthalate. The phosphor layer is made of various polymers that contain and support the phosphor particles in a dispersed state. As the phosphor, various phosphors known as phosphors for intensifying screens can be used. Further, a transparent protective film for physically and chemically protecting the phosphor layer may be provided on the surface of the phosphor layer opposite to the side in contact with the support.

The reading of the X-ray image information recorded on the X-ray sensitive material by X-ray photography is carried out for each of the two or more types of emulsion layers which have developed different colors from each other. Is performed using the reading light. For example, yellow, magenta and cyan colored emulsion layers can be read with blue, green and red light, respectively.

[0013]

[Operation and Effect] In the X-ray photosensitive material having the above structure,
A relatively low sensitivity emulsion layer is exposed by a relatively large exposure amount, and a relatively high sensitivity emulsion layer is exposed by a relatively small exposure amount. Line image information is recorded. After exposure, each emulsion layer develops a different color by development. By reading out each of the emulsion layers having different colors from each other with reading light having a wavelength absorbed by the color of the emulsion layer, the plurality of pieces of X-ray image information can be separately detected. As a result, the following effects can be obtained.

I) Even if there are portions where the X-ray transmittances are significantly different, X-ray image information of these portions can be obtained by one X-ray photographing. Therefore, the X-ray exposure dose of the subject is reduced.

Ii) Since the allowable width is wide, no problem occurs even if the exposure amount deviates from an appropriate value.

Iii) In the high exposure region, since an image is formed only from relatively fine silver particles, the graininess is improved (when the sensitivity of the emulsion layer is changed by the particle size).

IV) Since different X-ray image information can be obtained for each exposure area, threshold processing can be easily performed.

V) Since an image signal having a wider dynamic range than each image signal is constructed from digital image signals for each emulsion layer, which indicate different X-ray image information for each exposure area, extremely dynamic X-ray image information with a wide range can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows an example of an X-ray photosensitive material used in the X-ray image reading method of the present invention.

This X-ray light-sensitive material has a support 1 as a central layer, and is provided on both sides of the support 1 from the side close to the support.
An emulsion layer 2 composed of relatively small grain silver halide, an emulsion layer 3 composed of medium grain silver halide, and an emulsion layer 4 composed of relatively large grain silver halide are laminated in this order. is there. Each of the emulsion layers is configured to develop a different color after the phenomenon. In this embodiment, the emulsion layers 2, 3, and 4 are configured to emit cyan, magenta, and yellow, respectively.

A plurality of pieces of X-ray image information which differ depending on the sensitivity of each emulsion layer are recorded on the X-ray sensitive material by X-ray photography. FIG. 2 shows a characteristic curve for each emulsion layer, and the horizontal axis is a logarithm of a relative exposure amount based on the transmittance of the subject.
The vertical axis indicates the image density. I is a characteristic curve of the emulsion layer 4 which has sensitivity in a range where the exposure amount is relatively small, that is, contains a large grain silver halide having high sensitivity. Similarly, II and III are characteristic curves of the emulsion layers 3 and 2, respectively. As is clear from FIG.
Different X-ray image information is recorded in 3 and 4, respectively, and X-ray image information with a wide dynamic range can be recorded.

In the X-ray photosensitive material on which the X-ray image information is recorded, after development, each of the emulsion layers 2, 3, and 4 develops cyan, magenta, and yellow, respectively. Conventionally, an X-ray sensitive material is both a detection material and a display / observation material. However, since the X-ray sensitive material is used only as a detection material in the method of the present invention, there is a problem even if the color development of each emulsion layer is different. Not be.

The recorded X-ray image information is read as follows. The layer that developed cyan was irradiated with red light, the layer that developed magenta with green light, and the layer that developed yellow with blue light, and the light obtained from the X-ray photosensitive material by these irradiations. Is photoelectrically detected.
Thereby, three types of different X-ray image information can be finally obtained, that is, X-ray images having a wide dynamic range can be obtained.
Line image information can be obtained. This X-ray image information
Since different information is obtained for each density range of the image, threshold processing and the like can be easily performed. Further, after performing other appropriate image processing, it can be displayed on a CRT or the like as a reproduced image.

In the above embodiment, the sensitivity of each emulsion layer is changed by using silver halide having a different grain size. The sensitivity may be changed by other methods.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an X-ray photosensitive material used in the present invention.

FIG. 2 is a graph showing a characteristic curve of the X-ray photosensitive material used in the present invention.

[Explanation of symbols]

 1 support 2,3,4 emulsion layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03C 5/16 G03B 42/02 G03C 1/00

Claims (4)

(57) [Claims] An X-ray recording material recorded on an X-ray photosensitive material comprising at least a support and a plurality of layers including two or more emulsion layers having different sensitivities and different colors.
In the method of reading a line image, the X-ray sensitive material is scanned with a plurality of reading lights having wavelengths absorbed by respective colors of the two or more emulsion layers, and the X-ray photosensitive material is scanned by each reading light. By detecting light from the material, two or more kinds of digital image signals indicating X-ray image information for each emulsion layer are obtained. From these two or more kinds of digital image signals, an image having a wider dynamic range than each image signal is obtained. An X-ray image reading method comprising constructing a signal. 2. The X-ray image reading method according to claim 1, wherein said two or more types of emulsion layers have different silver halide grain sizes. 3. The method according to claim 1, wherein the emulsion layer in contact with the support among the two or more emulsion layers is colored with a colorant absorbing light emitted from an intensifying screen. Line image reading method. 4. An X-ray image reading apparatus according to claim 1, wherein said two or more kinds of emulsion layers contain a sensitizer, and the contents of said sensitizers are different from each other. Method.