JPH06130525A - Radiation image conversion method - Google Patents

Abstract

PURPOSE:To obtain images having improved image quality by using both side light condensing and reading in the radiation image conversion method. CONSTITUTION:X-rays 3 are projected from an X-ray source 2 of this X-ray photographing device 1 toward a subject 4 and a stimulable phosphor sheet 5 housed in a cassette 7 is irradiated with the X-rays 3 transmitted through the subject 4 and the transmitted X-ray images of the subject are accumulated and recorded on the stimulable phosphor sheet 5. The radiations 3b which are not completely absorbed by this sheet 5 are absorbed in an energy conversion body 6. This energy conversion body 6 excited by the radiations 3b emits UV rays. The sheet 5 accumulates these UV rays as well. The transmitted X-ray images of the subject are thus accumulated and recorded. The sheet 5 is taken out of the cassette 7. The sheet 5 is then irradiated with exciting light and the stimulating light rays emitted from both surfaces of the sheet 5 by irradiation with this exciting light are respectively photoelectrically read from both surfaces of the sheets 5, by which image signals are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion method using a combination of a stimulable phosphor sheet and an energy converter, and more particularly to reading a stimulable phosphor sheet in which radiation image information is stored and recorded. The present invention relates to a method for converting a radiation image in which the above is performed from both sides of the stimulable phosphor sheet.

[0002]

2. Description of the Related Art Radiation (X rays, α rays,
When irradiated with β rays, γ rays, ultraviolet rays, electron beams, etc.), a part of the energy of this radiation is accumulated in the phosphor, and when the phosphor is subsequently irradiated with excitation light such as visible light, it is accumulated. The phosphor emits stimulated emission depending on energy. A phosphor exhibiting such a property is called a stimulable phosphor (stimulable phosphor), and by using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily stored in a stimulable phosphor sheet ( (Hereinafter, referred to as a stimulable phosphor sheet) is recorded, scanned with excitation light to cause stimulated emission, and the stimulated emission light is photoelectrically read to obtain an image signal, and the image signal is processed. A method for obtaining a radiation image of a subject with good diagnostic suitability is widely known (for example, JP-A-55-12429 and JP-A-55-116340,
55-163472, 56-11395, 56-104645, etc.). This final image can be played as a hard copy or on a CRT.

As a method of reading the above-mentioned stimulated emission light, by providing photoelectric reading means for photoelectrically reading the stimulated emission light only on the side that scans the excitation light, light is emitted from one side of the stimulable phosphor sheet. There is known a method for photoelectrically reading the stimulated emission light obtained, but in addition to this method, by arranging the photoelectric reading means as described above on both sides of the stimulable phosphor sheet, the light is emitted from both sides. A double-sided condensing reading method for photoelectrically reading the generated stimulated emission light is known (for example, see JP-A-55-87970 and JP-A-56-11397).

When reading is performed from both sides of the stimulable phosphor sheet as described above, there are advantages that the light collecting efficiency as a whole is improved and the S / N ratio is improved.

In the double-sided condensing reading method described above, the excitation light scanning of the stimulable phosphor sheet is described as being performed from one side of the sheet, but such excitation light scanning is performed from one side. It is not limited and may be performed from both sides. When the excitation light scanning is performed from both sides, it is necessary to match the scanning points on both sides to perform scanning.

On the other hand, a radiation image conversion panel comprising a photostimulable phosphor that absorbs radiation and ultraviolet rays and a phosphor that emits ultraviolet rays when excited by radiation is used to utilize radiation carrying radiation image information. JP-A-2-176600 proposes to improve the sensitivity by increasing the rate. Specifically, this radiation image conversion panel has a wavelength range of 25
A stimulable phosphor that absorbs radiation less than 0 nm and ultraviolet rays having a wavelength range of 250 nm or more and 400 nm or less, accumulates the energy, and emits the energy as luminescence by receiving irradiation of visible light or infrared light. , The wavelength range is 250n
Excited by radiation less than m, wavelength range is 250nm or more
It is composed of a phosphor that emits ultraviolet rays of 400 nm or less.

[0007]

Conventionally, since radiation carrying image information is applied to one surface of the stimulable phosphor sheet, radiation image information is sufficiently stored and recorded on the back surface of the stimulable phosphor sheet. Not done. Further, since the radiation image information is also read from the surface of the sheet irradiated with the radiation, the back surface of the stimulable phosphor sheet has not been substantially utilized.

In view of the above circumstances, the present invention provides a radiation image conversion method capable of effectively utilizing the back surface of the stimulable phosphor sheet in double-sided condensing reading and capable of obtaining an image with improved image quality. The purpose is.

[0009]

According to the radiation image conversion method of the present invention, one side of a stimulable phosphor sheet made of a stimulable phosphor layer absorbs radiation and the energy of this radiation is transferred to the stimulable phosphor layer. Is arranged to form a laminated body by disposing an energy converter that converts the energy into another energy that can be accumulated, and by irradiating a radiation carrying image information of a radiation image on the side of the accumulative phosphor sheet of the laminated body, The image information is stored and recorded in a stimulable phosphor sheet, the stimulable phosphor sheet is separated from the energy converter, and the separated stimulable phosphor sheet is irradiated with excitation light, and by irradiation of this excitation light. Characterized in that the stimulated emission light emitted from both sides of the stimulable phosphor sheet is photoelectrically read from both sides of the stimulable phosphor sheet to obtain an image signal of the radiation image. Is shall.

Here, the energy converter is excited by absorbing radiation and is, for example, vacuum ultraviolet rays, ultraviolet rays, secondary X-rays, secondary electron beams, or the like, which is absorbed by the stimulable phosphor sheet. Is to be emitted. Therefore, the other energy mentioned above shows these light or radiation. Among the energy converters, vacuum ultraviolet rays and those that emit ultraviolet rays include, for example, JP-A 2-17
(Y, Sr) TaO ₄ as described in 6600:
Gd ³⁺ , BaSiO ₅ : Pb ²⁺ , Ca ₃ (PO ₄ ) ₂ :
_{Tl, (Ca, Zn) 3} (PO 4) 2: Tl, (Ba,
Examples thereof include those obtained by dispersing Zn, Mg) ₃ SiO ₂ O ₇ : Pb in a binder, and such an ultraviolet light emitting phosphor can also be used. Similarly, as the secondary X-ray emitter, for example, Gd ₂ O ₃ , CaWO ₄ , PbO
And the like are dispersed in a binder, and examples of the secondary electron beam emitting material include those in which Cu, Zn and the like are dispersed in the binder. However, the energy converter used in the present invention is not limited to these. In the radiation image conversion method of the present invention, it is essential that the energy converter is arranged on the back side of the stimulable phosphor sheet with respect to the incidence of radiation, but it is not only arranged on the back side but also on the front side. May be.

The stimulable phosphor sheet composed of the stimulable phosphor layer may be any sheet containing a stimulable phosphor layer. For example, a self-supportable stimulable phosphor layer, a support or a protective layer. The stimulable phosphor layer having the above is included, and an undercoat layer and the like can be included if necessary. Further, this stimulable phosphor layer is formed by the above-mentioned vacuum ultraviolet ray, ultraviolet ray, secondary X-ray.
Rays, secondary electron rays, and other light or radiation are absorbed and accumulated. Specific examples of absorbing ultraviolet rays are described in the above-mentioned JP-A-2-176600.

In the radiation image capturing in the radiation image converting method of the present invention, the above-mentioned stimulable phosphor sheet and the energy converting body are laminated, that is, the sheets and the converting body are arranged so that their surfaces are in close contact with each other, and this lamination is carried out. It is performed by irradiating the body with radiation carrying image information of a radiation image from the side of the stimulable phosphor sheet. After the storage and recording of the radiation image on the stimulable phosphor sheet as described above, the stimulable phosphor sheet is separated from the energy converter.

Next, a process of reading the radiation image from the stimulable phosphor sheet on which the radiation image is stored and recorded will be described. To read a radiation image, it is necessary to irradiate the stimulable phosphor sheet with excitation light. This excitation light may be irradiated from one side or both sides of the sheet. . Particularly, when the irradiation of the excitation light is performed as scanning on both sides of the sheet, it is necessary to match the scanning points on both sides to perform scanning.

In reading such a radiation image, whether the side of the stimulable phosphor sheet irradiated with radiation is the front side or the back side depends on the S / N ratio of the read image. Does not matter.

[0015]

In the radiation image conversion method of the present invention, the energy conversion body is arranged on one side of the stimulable phosphor sheet, and the radiation carrying the image information of the radiation image is irradiated from the stimulable phosphor sheet side. Radiation that the fluorescent phosphor sheet has not absorbed is absorbed by the energy conversion panel, and the energy converter excited by this radiation emits light or radiation accumulated by the stimulable phosphor sheet. Since the stimulable phosphor sheet can also store energy by this light or radiation, the stimulable phosphor can store the energy of the radiation that could not be directly absorbed through the energy converter. it can. Therefore, the utilization factor of radiation can be improved and the sensitivity can be improved. Furthermore, since the stimulable phosphor sheet on which the radiation image is stored and recorded can be separated from the energy converter for double-sided condensing reading, a radiation image with a further improved S / N ratio can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings.

FIG. 1 is a schematic diagram showing an example of an X-ray imaging apparatus used in the radiation image converting method of the present invention.

In this X-ray imaging apparatus 1, an X-ray source 2, a stimulable phosphor sheet 5 and a cassette 7 containing an energy converter 6 are arranged opposite to each other with a subject 4 in between.
At this time, the stimulable phosphor sheet 5 and the energy converter 6
Although they are not adhered to each other and can be separated from each other, they are closely fixed in the cassette 7.
This energy converter 6 may be attached to the cassette 7 or may simply be housed. Here, the X-ray 3 is emitted from the X-ray source 2 toward the subject 4, and the X-ray 3a transmitted through the subject 4 is emitted to the stimulable phosphor sheet 5 housed in the cassette 7, thereby Transmission X-ray image shows stimulable phosphor sheet 5
It is stored and recorded in. At the same time, the radiation 3b that the stimulable phosphor sheet 5 has not completely absorbed is absorbed by the energy converter 6.
The energy converter 6 that is absorbed by and is excited by the radiation 3b emits, for example, ultraviolet rays. in this way,
The stimulable phosphor sheet 5 also accumulates this ultraviolet ray, and the transmitted X-ray image of the subject is accumulated and recorded. Therefore, the utilization factor of radiation is good, and the stimulable phosphor sheet 5 has improved sensitivity.

After the X-ray photography, the stimulable phosphor sheet 5 is separated from the energy converter 6, taken out from the cassette 7 and used for reading an X-ray image by an X-ray image reading device.

In the above embodiment, the stimulable phosphor sheet and the energy converter are laminated in the cassette to form a laminate, but the laminate obtained by the radiation image conversion method of the present invention is accommodated in the cassette. It is not limited to things. An embodiment in which the cassette is not used includes an X-ray imaging apparatus having an energy converter fixed thereto. For example, in a so-called built-in type X-ray image recording / reading apparatus, a stimulable phosphor sheet is conveyed to a position where X-rays are irradiated, but energy conversion is performed behind the position where the sheet is conveyed with respect to the X-ray source. An example is one in which the body is fixed and arranged so as to be in close contact with the stimulable phosphor sheet. That is, such a stimulable phosphor sheet and an energy converter that are in a laminated state at the moment of being irradiated with X-rays are also referred to as a laminated body in the present invention.

FIG. 2 is a schematic view showing an example of an X-ray image reading apparatus for reading the X-ray image from the stimulable phosphor sheet 5 on which the X-ray image is stored and recorded as described above.

The stimulable phosphor sheet 5 is endless belts 19a, 19 rotated by a motor (not shown).
It is located above b. Above the sheet 5, a laser light source 11 that emits excitation light, a rotary polygon mirror 13 that reflects and deflects the laser light to perform main scanning of the sheet 5, and a motor 12 that rotates the rotary polygon mirror 13 are arranged. Has been done. Furthermore, above the position where the laser light is scanned, a light guide 15a for concentrating the stimulated emission light emitted by the scanning of the laser light from above is arranged closely, and below the position, A light guide 15 which collects the stimulated emission light from below.
b is arranged perpendicular to the sheet 5. Each light guide
Photomultipliers (photomultiplier tubes) 16a and 16b for photoelectrically detecting stimulated emission light are connected to 15a and 15b, respectively. The photomultipliers 16a and 16b are connected to logarithmic amplifiers 17a and 17b, and the logarithmic amplifiers 17a and 17b are connected to a storage device 18.

Next, the manner in which the X-ray image reading apparatus 10 reads an X-ray image from a stimulable phosphor sheet will be described with reference to FIG. In the X-ray imaging apparatus 1 shown in FIG.
An X-ray image of the subject is accumulated and recorded on the stimulable phosphor sheet 5. Storage phosphor sheet 5 on which this X-ray image is recorded
On the endless belts 19a and 19b. The stimulable phosphor sheet 5 set at this predetermined position is conveyed (sub-scanned) in the arrow Y direction by the endless belts 19a 1 and 19b 2. On the other hand, the light beam emitted from the laser light source 11 is reflected and deflected by the rotary polygon mirror 13 which is driven by a motor 12 and rotates at a high speed in the arrow direction, and the sheet 5
X which is incident on and is substantially perpendicular to the sub-scanning direction (arrow Y direction).
Main scan in the direction. Sheet 5 irradiated with this light beam
From the point, the stimulated emission lights 14a and 14b (here, the stimulated emission light 14a and 14b) having a light amount corresponding to the accumulated and recorded X-ray image information are recorded.
a and 14b respectively indicate those emitted from above and below the seat 5). This stimulated emission light 14a is guided by a light guide 15a and photoelectrically detected by a photomultiplier (photomultiplier tube) 16a. The light guide 15a is formed by molding a light guide material such as an acrylic plate, and is arranged so that the linear incident end face extends along the main scanning line on the stimulable phosphor sheet 5. , The photomultiplier on the emission end face formed in a ring shape.
The light receiving surface of 16a is bonded. The stimulated emission light 14a that has entered the light guide 15a from the incident end face is the light guide 15a.
The photomultiplier 16a receives the photomultiplier 16a, which is emitted from the exit end face by repeating total internal reflection in a.
It is converted into an electric signal by 16a. Similarly, the stimulated emission light 14b is guided by a light guide 15b and photoelectrically detected by a photomultiplier (photomultiplier tube) 16b.

The analog output signal S1 output from the photomultiplier 16a is logarithmically amplified by the logarithmic amplifier 17a and input to the storage device 18. Here, the included A
The image signal Sp1 is obtained by being digitized by the / D converter. Here, similarly, the analog output signal S2 output from the photomultiplier 16b is logarithmically amplified by the logarithmic amplifier 17b and input to the storage device 18. Here, the image signal Sp2 is obtained by being digitized by the included A / D converter. These image signals Sp1 and Sp2 are added by the arithmetic unit of the storage device 18 to obtain a final image signal. The signal level of this final image is proportional to the logarithm of the amount of stimulated emission light emitted from each pixel of the sheet 5. In this way, the stimulated emission light emitted by the irradiation of the excitation light is collected from both sides, so that the light collection efficiency is increased and the S / N ratio of the obtained image is improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an X-ray imaging apparatus used in a radiation image conversion method of the present invention.

FIG. 2 is a schematic diagram showing an example of an X-ray image reading apparatus.

[Explanation of symbols]

 1 X-ray photographing device 2 X-ray source 3 X-ray 4 Subject 5 Accumulable phosphor sheet 6 Energy converter 7 Cassette 10 X-ray image reading device 14 Photostimulated luminescence light 15 Light guide 16 Photomultiplier 17 Logarithmic converter 18 Memory Device 19 Endless belt

Claims (1)

[Claims] 1. An energy converter that absorbs radiation on one surface of a stimulable phosphor sheet composed of a stimulable phosphor layer and converts the energy of this radiation into another energy that can be accumulated by the stimulable phosphor layer. Is arranged to form a laminate, and the image information is accumulated and recorded in the stimulable phosphor sheet by irradiating the stimulable phosphor sheet side of the laminate with radiation carrying image information of a radiation image. The stimulable phosphor sheet is separated from the energy converter, the separated stimulable phosphor sheet is irradiated with excitation light, and the luminescence emitted from both sides of the stimulable phosphor sheet by the irradiation of the excitation light. A radiation image conversion method comprising photoelectrically reading exhausted light from both sides of the stimulable phosphor sheet to obtain an image signal of the radiation image.