JP2003344963A - Radiation image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image reader which can obtain a sharp image with high S/N by reducing noise due to scattered exciting light. <P>SOLUTION: The radiation image reader is equipped with an exciting light irradiating means 20 which irradiates a radiation image conversion plate 10 with exciting light P, a light converging means 30 which converges stimulating light Q emitted by the radiation image conversion plate 10, and a photoelectric converting means 40 which photoelectrically converts the converged stimulating light Q, and provided with an antireflective part which prevents exciting light P<SB>1</SB>, scattered by the radiation image conversion plate 10, from being reflected by the light converging means 30 to impinges on the radiation image conversion plate 10 again. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image reading device for reading radiation image information from a radiation image conversion plate.

[0002]

2. Description of the Related Art Radiation images represented by X-ray images are widely used in the fields of disease diagnosis and the like. As a method for obtaining this X-ray image, X-rays that have passed through the subject are irradiated to the phosphor layer (fluorescent screen), thereby generating visible light, and this visible light is irradiated to the silver halide photosensitive material,
A so-called radiographic method is widely used in which a visible silver image is obtained by developing the silver halide light-sensitive material.

However, in recent years, a new method of directly reading an image from the phosphor layer has been proposed instead of the radiographic method. As this method, the radiation that has passed through the subject is accumulated in the fluorescent substance, and when reading, the fluorescent substance is excited by light or thermal energy to cause the accumulated radiation energy to be emitted as fluorescence, and this fluorescent light is detected. There are things that can be imaged.

As an example of such a method, there is a radiation image recording / reproducing system using a stimulable phosphor disclosed in US Pat. No. 3,859,527 and JP-A-55-12144. In this radiation image recording / reproducing system, a radiation image conversion plate containing a stimulable phosphor is used, and the stimulable phosphor layer of this radiation image conversion plate is irradiated with the radiation that has passed through the subject. Radiation energy corresponding to the radiation transmission density is accumulated to record a radiation image of a subject.

Thereafter, in order to reproduce the radiation image, the stimulable phosphor is excited in time series with excitation light such as laser light in the visible to near-infrared wavelength region, and accumulated in the stimulable phosphor. The emitted radiation energy is emitted as photostimulable light, the signal due to the intensity of the emitted photostimulable light is converted into an electric signal by a photoelectric conversion element such as a photomultiplier tube, and this signal is converted into a silver halide photographic light-sensitive material. A visible image is formed on a display device such as the recording material or CRT. As the stimulable phosphor, one that is excited by excitation light having a wavelength of 400 to 900 nm and emits stimulable light having a wavelength of 300 to 500 nm is generally used.

In the above-mentioned radiographic image recording / reproducing system, since the stimulable phosphor has high sensitivity to radiation, it is possible to reduce the amount of exposure to an object and to reduce the amount of information compared to the conventional radiographic system. It has an advantage that abundant radiographic images can be obtained. Further, since the radiation energy accumulated when reading the radiation image information from the radiation image conversion plate is emitted as stimulating light, the radiation image can be accumulated again on the radiation image conversion plate after reading. That is, in this radiation image conversion system, the radiation image conversion plate can be repeatedly used, which is advantageous in terms of resource protection and economic efficiency.

In the radiation image reading apparatus for reading the radiation image of the radiation image conversion plate 100, as shown in FIG. 3, the stimulating light Q emitted by irradiating the radiation image conversion plate 100 with the excitation light P is, for example, Light is condensed from a light guide plate 101 made of an acrylic plate or the like, a reflecting mirror 106 or the like, and guided to a photoelectric conversion element such as a photomultiplier tube. The light guide plate 101 guides the photostimulable light Q incident on one end 102 thereof to the photomultiplier tube. One end 10 of the light guide plate 101
2 is the same as the width of the radiation image conversion plate 100 irradiated with the excitation light P, because it is necessary to collect the stimulated light Q uniformly over the entire width of the radiation image conversion plate 100 irradiated with the excitation light P. The width is longer than the width.

In order to allow the stimulated light Q to enter the light guide plate 101 efficiently, the reflection mirror 106 is provided on the opposite side of the one end 102 of the light guide plate 101 with respect to the excitation light P entering the radiation image conversion plate 100. Thus, the stimulated light Q is reflected and made incident on one end 102 of the light guide plate 101.

[0009]

When the excitation light P enters the radiation image conversion plate 100, the excitation light P is scattered inside the radiation image conversion plate 100 to generate scattered excitation light P ₁ . When the scattered excitation light P ₁ is reflected by the reflecting mirror 106 or the holding member 107 and is incident on the radiation image conversion plate 100 again, the reflected excitation light P ₂ excites the stimulable phosphor to give a regular signal. Not give rise to stimulated emission Q ₁ . One end 10 of the light guide plate 101
The photostimulable light Q ₁ which is not a regular signal is also incident on the photomultiplier 2, and the photomultiplier tube also photoelectrically converts the photostimulable light Q _{1 which} is noise in addition to the photostimulable light Q which is a regular signal. become.
Therefore, the generation of this stimulated emission Q ₁ is due to the S / N ratio of the radiation image.
It was a cause of deterioration of the ratio. An object of the present invention is to provide a radiation image reading apparatus that can reduce noise due to scattered excitation light and can obtain a sharp image with a high S / N ratio.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 emits from excitation light irradiation means for irradiating the radiation image conversion plate with excitation light, and the radiation image conversion plate. A radiation image reading apparatus comprising: a condensing unit that condenses the stimulating light and a photoelectric conversion unit that photoelectrically converts the stimulating light condensed by the condensing unit. It is characterized in that an antireflection portion is provided for preventing the excitation light scattered by the plate from being reflected by the light condensing means and again entering the radiation image conversion plate.

According to the first aspect of the invention, the excitation light scattered when the excitation light irradiating means irradiates the radiation image conversion plate with the excitation light is reflected by the condensing means and is again reflected on the radiation image conversion plate. Since the incident light is prevented by the antireflection portion provided in the light collecting means, noise is not included in the stimulating light collected by the light collecting means, and an image read by photoelectric conversion is read as an S / N ratio. It can be sharp and high.

According to a second aspect of the present invention, in the radiation image reading apparatus according to the first aspect, the light condensing unit guides the stimulated light to the photoelectric conversion unit, and the light guide unit illuminates the light guiding unit. It is characterized in that it comprises a reflection part that reflects exhaust light and makes it enter, and the antireflection part is provided on an outer peripheral part of a reflection surface of the reflection part.

According to the second aspect of the present invention, the photostimulable light emitted from the radiation image conversion plate in each direction can be reflected by the reflection part and efficiently incident on the light guide part to be guided to the photoelectric conversion means. it can.

According to a third aspect of the present invention, in the radiation image reading apparatus according to the first or second aspect, the antireflection portion absorbs the excitation light scattered by the radiation image conversion plate and has black flocking. It is a sheet.

According to the third aspect of the present invention, the excitation light scattered by the radiation image conversion plate can be reliably absorbed in the black flocked portion of the flocked sheet.

According to a fourth aspect of the present invention, in the radiation image reading apparatus according to the first or second aspect, the antireflection portion is a black paint that absorbs the excitation light scattered by the radiation image conversion plate. It is characterized by being a layer.

According to the invention described in claim 4, the excitation light scattered by the radiation image conversion plate can be reliably absorbed in the black portion of the coating layer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray image reading apparatus, which is an embodiment of the radiation image reading apparatus of the present invention, will be described in detail below with reference to the drawings.

As shown in FIG. 1, an X-ray image reading apparatus 1
Is an excitation light irradiation means 20 for irradiating the X-ray image conversion plate 10 with the excitation light P, a condensing means 30 for condensing the stimulated light Q emitted from the X-ray image conversion plate 10, and a condensed condensate. And a photomultiplier tube 40 for photoelectrically converting the exhaust Q,
The X-ray image information recorded on the X-ray image conversion plate is read.

The X-ray image conversion plate 10 is, for example, Ba
The photocatalyst film has a stimulable phosphor sheet coated with microcrystals of a stimulable phosphor such as FBr: Eu ²⁺ , and is formed in a planar shape. When capturing an X-ray image, the X-ray image conversion plate 10 is housed in a radiation imaging cassette, and is installed, for example, in a state of being close to an imaging region of a subject. And this X
By irradiating the X-ray incident on the X-ray image conversion plate 10 through each part of the subject, X-ray energy corresponding to the X-ray transmission density of each part of the subject is accumulated in the stimulable phosphor, and the X-ray image of the subject is obtained. Information is X-ray image conversion plate 10
Recorded in.

The excitation light irradiation means 20 comprises an excitation light emitting section 2
1, collimating lens 22, cylindrical lens 2
3, a polygon mirror 24, an fθ lens 25, a cylindrical mirror 26, a scanning motor (not shown), and the like.

The excitation light emitting section 21 is composed of a semiconductor laser or the like and emits the excitation light P. The wavelength of the excitation light P is 40
It is light in the visible or near infrared region in the range of 0 to 900 nm. By irradiating the stimulable phosphor with excitation light in this wavelength range, the stimulable phosphor is excited to release the accumulated X-ray energy as stimulable light in the wavelength range of 300 to 500 m.

Excitation light P emitted from the excitation light emitting section 21
First enters the collimator lens 22. The collimator lens 22 is a plano-convex lens having a function of collimating light, and emits the incident excitation light P as parallel light. The excitation light P that has passed through the collimator lens 22 then passes through the cylindrical lens 23. Cylindrical lens 2
Reference numeral 3 denotes a convex lens formed in a semi-cylindrical shape with a cylinder cut out, and focuses the excitation light P that has become parallel light in the thickness direction of the X-ray image conversion plate 10.

The excitation light P that has passed through the cylindrical lens 23 then enters the polygon mirror 24. The polygon mirror 24 is in the shape of a hexagonal prism and has a side surface 24a.
A mirror is attached to. Also, the polygon mirror 24
A scanning motor is connected to and is rotatable by the operation of the scanning motor. Therefore, the excitation light P incident on the polygon mirror 24 due to the operation of the scanning motor is reflected by the mirror of the side surface portion 24a and incident on the fθ lens while changing the angle little by little.

The fθ lens 25 focuses the excitation light P reflected by the polygon mirror 24 in the width direction of the X-ray image conversion plate 10 (direction of arrow C). Further, the cylindrical mirror 26 reflects the excitation light P focused by the fθ lens 25 to the X-ray image conversion plate side to reach the X-ray image conversion plate 10. At this time, the rotation of the polygon mirror 24 changes the angle of incidence on the fθ lens, so that the excitation light P moves from one side A of the X-ray image conversion plate 10 toward the other side B opposite to the one side A and the arrow C. When the X-ray image conversion plate 10 is irradiated with the excitation light P
Scanned by.

The condensing means 30 guides the stimulated light Q to the photomultiplier tube 40 (light guide portion), and a reflecting mirror 36 (reflects the stimulated light Q to the light guide plate 31 to make it incident. (Reflector)
And a holding member 37 for holding the reflecting mirror 36.

The light guide plate 31 has a substantially plate-like shape in which one end 32 has a width substantially the same as the width of the X-ray image conversion plate 10 (the length in the direction of arrow C shown in FIG. 1) or longer than the width. Present. The excitation light P is directed to the X-ray image conversion plate 10 by an arrow C.
The photostimulable light Q incident from the one end 32 is guided to the photomultiplier tube 40 provided at the other end 33 as it is irradiated in the direction shown in FIG.

Further, inside the light guide plate 31, there is provided a filter that allows light having a wavelength corresponding to the wavelength of the stimulated light Q to pass therethrough and blocks light having other wavelengths. As described above, since the wavelengths of the stimulated emission light Q and the excitation light P are different, the light guide plate 3
Even if the excitation light P is incident on the end 32 of 1 together with the stimulated emission light Q, the excitation light P is blocked by the filter.

The reflecting mirror 36 is formed in a substantially plate shape whose reflecting surface 36a has the same width as the one end 32 of the light guide plate 31. The reflecting mirror 36 is held by a holding member 37,
The reflection surface 36a is arranged so as to be located on the opposite side of the one end surface 32a of the light guide plate 31 with the excitation light P incident on the X-ray image conversion plate therebetween, and the reflection surface 36a.
Is reflected by the stimulating light Q and the one end face 3 of the light guide plate 31
It is adjusted so as to be incident on 2a.

The outer peripheral portion 36b of the reflecting surface 36a of the reflecting mirror 36 and the surface of the holding member 37 on the X-ray image conversion plate 10 side absorb the scattered excitation light P ₁ scattered by the X-ray image conversion plate 10. The black flocked sheet 50 is attached along the width direction (direction of arrow C) of the X-ray image conversion plate 10. As the black flocked sheet 50 that absorbs such scattered excitation light P ₁ , for example, Ron Sade series manufactured by Bell Sade can be cited. That is, in the black flocked sheet 50, the scattered excitation light P ₁ is reflected by the reflecting mirror 3.
6 and the holding member 37 to function as an antireflection portion that prevents the light from being reflected and incident on the X-ray image conversion plate 10 again.

Further, instead of the black flocked sheet 50, the outer peripheral portion 36b of the reflecting mirror 36 and the X of the holding member 37.
A black paint layer formed by applying a black paint may be provided on the surface of the line image conversion plate 10 side. Examples of such black paints include antireflection paints such as GT series manufactured by Logimol.

The photomultiplier tube 40 detects the photostimulable light Q emitted from the X-ray image conversion plate 10, and the photostimulable light Q emitted according to the X-ray energy accumulated by the photostimulable phosphor.
The electric signal corresponding to the strength of is generated as a current signal. That is, the photomultiplier tube 40 functions as a photoelectric conversion unit that photoelectrically converts the collected photostimulable light Q.

The current signal generated by the photomultiplier tube 40 is reproduced as a visible image on a recording material such as a silver halide photographic light-sensitive material or a display device such as a CRT to convert an X-ray image. An X-ray image of the subject recorded on the plate 10 can be obtained.

According to the present embodiment, the excitation light irradiation means 2
0 to irradiate the X-ray image conversion plate 10 with the excitation light P.
Scattering excitation scattered by the X-ray image conversion plate 10 when moving
Light P ₁Is the outer peripheral portion 36 b of the reflecting mirror 36 and the holding member 37.
Black plant attached to the surface of the X-ray image conversion plate 10 side
It is surely absorbed by the flocked part of the hair sheet 50 and the X-ray image is changed.
It is prevented from re-entering the replacement plate 10.
Therefore, the stimulable fluorescence of a part other than the part irradiated with the excitation light P
X-rays do not generate stimulated light that causes noise when the body is excited.
The X-ray image read by the image reading device 1 has a high S / N ratio.
Can be sharp.

Further, as described above, the outer peripheral portion 3 of the reflecting mirror 36 is
The scattered light P ₁ can be obtained by simply sticking the black flocked sheet 50 on the X-ray image conversion plate 10 side surfaces of 6b and the holding member 37.
Since it can be prevented from re-incident on the X-ray image conversion plate, it is possible to very easily prevent the generation of stimulating light that becomes noise.

Further, in this embodiment, the reflecting mirror 3
Although the black flocked sheet 50 is attached to the outer peripheral portion 36b of 6 and the surface of the holding member 37 on the X-ray image conversion plate 10 side, the present invention is not limited to this, and the reflecting mirror 3 is not limited thereto.
The black flocked sheet 50 may be attached only to the outer peripheral portion 36b of 6, or the black flocked sheet 50 may be formed on the surface 31a of the light guide plate 31 on the X-ray image conversion plate 10 side.
May be attached. The antireflection portion is not limited to the black flocked sheet 50 and the black paint layer, and the reflectance of 4 at an incident angle of 70 degrees with respect to the excitation light.
% Or less, preferably 1% or less.

Further, in addition to constituting a member for absorbing the scattered excitation light P ₁ as an anti-reflection portion, when the scattered excitation light P ₁ is incident on the focusing means 30, the scattered excitation light P ₁ X-ray image The scattered excitation light P ₁ may be prevented from reentering the X-ray image conversion plate 10 by being configured of a member that reflects light in a direction that deviates from the conversion plate 10.

In the above embodiment, the subject is irradiated with X-rays, but the subject is not limited to X-rays. For example, α rays, β rays, γ rays, neutron rays, electron beams, Any radiation such as ultraviolet rays may be used.

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

In this example, the S / N improvement effect of the read X-ray image was measured by the lead disk method using the X-ray image reading apparatus 1 described above. As the black flocked sheet 50 attached to the reflecting mirror 36 and the holding member 37,
Of the Ron Sade series manufactured by Bell Sade, those having a reflectance of about 0.2% at an incident angle of the excitation light P of 70 degrees were used.

As a result, the value of the glare content when the black flocked sheet was not attached was 1.0% for the lead disk having a diameter of 20 mm, whereas it was 0.3% for this embodiment. Was improved. This is read by attaching the black flocked sheet 50 to the outer peripheral portion 36b of the reflecting mirror 36 and the holding member 37 that holds the reflecting mirror 36.
This shows that the noise component has become about 1/3 in the line image. Also, in the actual phantom image, a clear contrast improvement was visually observed near the hip joint on the side of the lumbar spine. That is, by providing the antireflection unit 50 for the scattered excitation light P ₁ on the X-ray image conversion plate 10 side of the light condensing unit 30, it was possible to obtain a sharp image with little noise and a high S / N ratio.

[0042]

According to the first aspect of the invention, it is provided in the light collecting means that the excitation light scattered by the radiation image converting plate is reflected by the light collecting means and re-enters the radiation image converting plate. Since it is prevented by the reflecting member, noise is not included in the concentrated photostimulated light, and the image read by photoelectric conversion can be made sharp with a high S / N ratio.

According to the invention of claim 2, claim 1
The same effect as in the above can be obtained, and the stimulating light emitted from the radiation image conversion plate is reflected by the reflecting portion and is incident on the light guide portion, so that the stimulating light can be efficiently collected. .

According to the invention of claim 3, claim 1
Alternatively, the same effect as in claim 2 can be obtained, and the excitation light scattered by the radiation image conversion plate can be reliably absorbed by the black flocked portion of the flocked sheet.

According to the invention described in claim 4, it goes without saying that the same effect as that of claim 1 or 2 can be obtained.
Excitation light scattered by the radiation image conversion plate can be reliably absorbed by the black portion of the paint layer.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part configuration of a radiation image reading apparatus according to an example of the present invention.

FIG. 2 is a side sectional view showing a main configuration of a radiation image reading apparatus according to an example of the present invention.

FIG. 3 is a side sectional view showing a main configuration of a conventional radiation image reading apparatus.

[Explanation of symbols]

1 Radiation image reading device (X-ray image reading device) 10 Radiation image conversion plate (X-ray image conversion plate) 20 Excitation light irradiation means 30 Condensing means 31 Light guide part (light guide plate) 36 Reflecting mirror (reflection part) 36a Reflection Surface 36b Outer peripheral portion 40 Photoelectric conversion means (photomultiplier tube) 50 Antireflection portion, black flocked sheet P Excitation light P ₁ Excitation light scattered by radiation image conversion plate (scattering excitation light) Q Extinction light

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Claims (4)

[Claims] 1. An excitation light irradiating means for irradiating a radiation image conversion plate with excitation light, a condensing means for condensing stimulated light emitted from the radiation image conversion plate, and a condensing means for condensing the stimulating light. In a radiographic image reading device comprising photoelectric conversion means for photoelectrically converting stimulated light, in the condensing means, the excitation light scattered by the radiographic image conversion plate is reflected by the condensing means, and the radiographic image conversion plate is again provided. A radiation image reading apparatus comprising an antireflection portion for preventing the light from entering the radiation image reading apparatus. 2. The radiation image reading device according to claim 1, wherein the light condensing unit guides the stimulated light to the photoelectric conversion unit, and the light guide unit reflects the stimulated light to enter. A radiation image reading apparatus, comprising: a reflection section that causes the reflection prevention section to be provided on an outer peripheral portion of a reflection surface of the reflection section. 3. The radiation image reading device according to claim 1, wherein the antireflection portion is a black flocked sheet that absorbs the excitation light scattered by the radiation image conversion plate. Radiation image reading device. 4. The radiation image reading apparatus according to claim 1, wherein the antireflection portion is a black paint layer that absorbs excitation light scattered by the radiation image conversion plate. Radiation image reading device.