JPS6051099B2 - Radiation image information reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reading device that reads radiation image information recorded on a stimulable phosphor by irradiating the stimulable phosphor and measuring the emitted light. .

When a storage phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, etc.), a portion of the energy of this radiation is stored.

When this stimulable phosphor is irradiated with excitation light, it emits light according to the accumulated energy. Using this stimulable phosphor, X-ray images of the human body, etc. are recorded once on a sheet-like stimulable phosphor plate, which is then scanned with a laser beam, etc., and the emitted light is detected using a photodetector. An X-ray image forming apparatus is known that records an X-ray image on a recording medium such as photographic film by modulating a light beam with the read image information (U.S. Pat. No. 3,859,527). ).

In this device, a large half mirror inclined at 450 is placed at a considerable distance from the stimulable phosphor plate. The excitation light passes through this half mirror and enters the stimulable phosphor. The emitted light is reflected laterally by a half mirror, collected by a condenser lens, and enters a photodetector. The light emitted from this stimulable phosphor plate is non-directional and is itself weak light, so it is necessary to increase the light-receiving solid angle as much as possible to collect as much light as possible to increase light collection efficiency.

If this light collection efficiency is low, the S/N ratio decreases, and in the worst case, it becomes impossible to even detect a signal. However, the above-mentioned device has the drawback that the light-receiving solid angle of the photodetector cannot be made sufficiently large due to its configuration, and the light collection efficiency is poor.

SUMMARY OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a radiation image information reading device that can increase light collection efficiency and improve the S/N ratio.

The present invention is a radiation image information reading device that scans a stimulable phosphor plate with excitation light to read radiation image information recorded thereon, in which light emitted by the stimulable phosphor plate is detected. a photodetector, and a light transmission means disposed between the photodetector and the stimulable phosphor plate, the light transmission means comprising a light-guiding sheet material (hereinafter simply referred to as one sheet); One end thereof is provided adjacent to the scanning line on the stimulable phosphor plate, and the other end is formed to match the shape of the light receiving surface of the photodetector and is provided adjacent to the light receiving surface. It is.

The light transmission means should be made of a material that is transparent to the wavelength of the light to be focused, and should be as homogeneous as possible so that there is no loss of the light to be focused within the material; It is necessary to use a material that causes so-called total reflection on the surface of the material (at the interface with air).

It is also necessary that the surface be finished sufficiently smooth. As mentioned above, the general shape of this light transmitting means is that one end is in a straight line or an arc shape because it is necessary to be provided adjacent to the scanning line on the stimulable phosphor plate, and the other end is in the shape of a straight line or an arc for receiving light from the photodetector. It is deformed or formed to match the shape of the surface (for example, circular).

What is important here is that the light transmission means itself needs to be made of a material shaped so that when rolled, it becomes a single sheet with approximately uniform thickness and width. be. This increases the probability of total reflection inside the light transmission means, making it possible to prevent light loss. The shape of the light transmission means must be such that the incident light is transmitted while repeating total reflection.For example, even if the bending itself is gentle, the light transmitted through it must be completely reflected. It is undesirable to have dimensions that result in non-reflection.

This makes it possible to transmit the light to be focused from the light focusing surface to the light receiving surface of the photodetector with almost no loss. The thickness of the light transmission means is 1 considering the light emitting point on the light converging surface.
The solid angle of light collection will be determined. From the point of view of increasing light collection efficiency, it is necessary to increase the solid angle of light collection, and for this purpose, it is advantageous to move the light collection surface closer to the light emitting point or to increase the thickness of the light transmission means. However, increasing the thickness of the light transmission means leads to an increase in the light-receiving area on the light-receiving surface of the photodetector at the other end, which has a certain limit, and may also be subject to restrictions due to deformation processing of the light transmission means. .

Regarding other dimensions of the light transmission means, the following can be said.

Of course, the width depends on the length of the scanning line on the stimulable phosphor plate that you want to receive light, and if this is very large, multiple light transmission means may be used to share the light transmission. can. In addition, the length of the light transmission means is better from the point of view of making the deformation gradual as described above and minimizing the loss of light due to deformation, and vice versa. From the point of view of reducing absorption in the transmission means, the shorter the length, the better; from a practical point of view, the appropriate length to width ratio is 0.5 to 5, preferably 1 to 3. Laser light with good directivity is used as excitation light for reading out the radiation image accumulated on the stimulable phosphor plate, and the stimulable phosphor plate is scanned with this laser light.

In general, there are two methods of scanning: one is to perform main scanning and sub-scanning simultaneously using either a stimulable phosphor plate or a laser beam, and the other is to combine the movements of both for two-dimensional scanning. In the apparatus of the invention, since the light transmitting means is provided adjacent to the scanning line of the laser beam on the stimulable phosphor plate, there is a structural advantage that only the sub-scanning need be performed mechanically. In this case, the sub-scanning is performed by moving the phosphor plate itself, or by moving the light transmitting means and the main scanning by a laser beam together on the phosphor plate. below,
Preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view of an image information reading device using a photodetector having a circular light-receiving surface, and shows an embodiment using a holder 10 capable of linear movement on a plane.

On the surface of the holder 10 is a rectangular stimulable phosphor plate 1.
1 is installed. X-ray image information is recorded on this stimulable phosphor plate 11 by ordinary X-ray photography. The stimulable phosphor plate 11 used is a 20C71 square one, in which a BaFCl:Eu phosphor with an average particle size of 10p is coated on a cellulose triacetate support using nitrocellulose, and then dried into a film. The thickness is 200p.

In addition to BaFCl:Eu, storage fluorophores include
Japanese Patent Application No. 53-84740 (Japanese Unexamined Patent Publication No. 55-12142), No. 8474? (Unexamined Japanese Patent Publication No. 55-12143), No. 8
No. 4743 (Japanese Unexamined Patent Publication No. 12144/1984), No. 8474
4 (Japanese Unexamined Patent Publication No. 55-12145) described in each specification can be suitably used.

The light transmitting means 12 is arranged so that the condensing surface 12a faces the stimulable phosphor plate 11 as close as possible, and the light transmitting surface 12b of the light transmitting means 12 has a photodetector in close contact therewith. 13 are arranged.

The photodetector 13 should have as large a light receiving area as possible, and since it measures weak light emission, S
A material with a good /N ratio is desirable.

Examples of such a photodetector 13 include a head-on type photomultiplier tube in which a light-receiving surface is formed on the end face, a channel plate for photoelectron amplification, and the like. Details of the light transmission means 12 are shown in FIG. One end surface 12a is linear, and the other end surface 12b, which is in close contact with the photodetector 13, is wound in a circular shape to match the shape of the light-receiving surface of the photodetector. It's summery. When the light-receiving surface of the photodetector is square in shape, the light-transmitting surface of the light-transmitting means can be folded into a rectangular shape as shown in FIG.

As the excitation laser light, one in the range of infrared light, near-infrared light, and visible light can be used. In this embodiment, a laser light source 15 that emits red light is used as a light source. The laser light from the laser light source 15 is vibrated by the optical deflector 14 in a direction substantially parallel to one edge of the stimulable phosphor plate 11, and scans the stimulable phosphor plate 11 in the said direction. It becomes a beam.

Next, the operation of the embodiment having the above configuration will be explained.

A red laser beam having a wavelength of 600 to 700 nm emitted from the laser light source 15 is turned into a scanning beam by the optical deflector 14 and is incident on the stimulable phosphor plate 11 stored in the holder 10 to generate stimulable fluorescent light. Excite body layers.

This light excitation causes the stimulable phosphor layer to emit light.

This luminescence corresponds to the energy accumulated by X-ray irradiation. Therefore, the emitted light from each point carries the X-ray image information at that point. By the laser scanning beam and the movement of the stimulable phosphor plate 11 in a direction perpendicular thereto, the stimulable phosphor plate 11 is two-dimensionally scanned, and each point on the stimulable phosphor plate 11 emits light.

The emitted light enters the light transmitting means 12 from the condensing surface 12a of the light transmitting means 12, is transmitted inside the light transmitting means 12, enters the light receiving surface of the photodetector 13 via the other end surface, and is sent as an electrical signal. is converted to The read X-ray image information controls the laser light modulator of the photographic film exposure device. Using this laser light whose intensity is controlled, an X-ray image is reproduced on a recording medium such as photographic film. In addition to silver halide photographic film, diazo film, electrophotographic materials, etc. can be used as recording media.

Also, instead of printing on film, it may be displayed on a CRT or the like. The light transmission means 12 used in this example is a polymethyl methacrylate resin plate (5W0n thick).
The above-mentioned shape is obtained by heating and deforming an acrylic plate (hereinafter referred to as 1 acrylic plate), but in addition to the above-mentioned acrylic plate, transparent vinyl chloride resin, polycarbonate resin, and polyester resin can also be used as materials for the light transmission means. , synthetic resin such as epoxy resin, glass, etc. can be used.

Further, as for the processing method, in addition to heating and softening the sheet and processing it into a predetermined shape as described above, various types of pressing, casting, etc. can also be used.

In the case of processing from a sheet, dividing the sheet into strips from the middle has the advantage of reducing the amount of deformation as a whole (this example is shown in FIG. 4). The excitation light is transmitted to the photodetector 13
Since the S/N ratio decreases when the excitation light and the emitted light are measured by being incident on the excitation light, it is necessary to measure only the emitted light by using different wavelengths of the excitation light and the emitted light. For example, the excitation light is red (600-70
A laser beam of 0r1m) is used, and a blue light (30
0 to 500r1m) is used. When the excitation light and the emission light have different wavelengths, a stimulable phosphor that emits light of a predetermined wavelength is used.

If the emission wavelength of a stimulable fluorophore covers a wide range, it is possible to measure only a specific wavelength by using a filter or by selecting the spectral sensitivity of the photodetector. There is a need to. In the case of the present invention, a filter layer as described above may be provided on the light collecting surface 12a of the light transmitting means 12, or this filter layer may be provided on the light receiving surface of the photodetector 13.

Alternatively, the light transmitting means 12 itself may be colored to serve as a filter. The filter layer can also be provided as a vapor deposited film. As the photodetector 13, one that is sensitive only to emitted light and not to excitation light is used. Alternatively, a filter may be attached in front of the photodetector 13 to allow only emitted light to pass through. FIG. 5 shows an embodiment in which emitted light is measured from both sides of a stimulable phosphor plate.

When the stimulable phosphor plate 20 is transparent, the emitted light is also emitted from the back side. Therefore, using a transparent holder 21,
A stimulable phosphor plate 20 is attached to this, and photodetection systems 22 and 23 are arranged at the upper and lower parts of the holder 21. Upper photodetection system (combination of light transmission means and photodetector)
A laser beam scanning system (a combination of a laser light source and an optical deflector) is placed close to the laser beam. In this embodiment, since the transmitted light is also collected, the light collection efficiency is improved and the S/N ratio is further improved.

As mentioned above, the light receiving section in the device of the present invention is arranged along the main scanning direction of the scanning beam, so the mechanical scanning for reading image information is performed by scanning the width of the scanning beam. Only the direction is sufficient. This is because the main scanning direction can be extracted by time-dividing the output of the photodetector. In this embodiment, the stimulable phosphor plate is handled in a flat state, but the present invention is not limited to this, and the stimulable phosphor plate may be wound around a drum, or may be transported while being partially wound around the drum.

Further, in each of the above-mentioned embodiments, one light transmission means was provided on one side of the stimulable phosphor plate, but the sixth embodiment
It goes without saying that if two light transmitting means are placed adjacent to the scanning line, sandwiching the scanning line (with an interval sufficient for the scanning beam to pass through) as shown in the figure, the light collection efficiency will be further increased.

In this case, the other end surfaces of the two light transmission means may be connected to one (common) photodetector, or they may be connected to separate photodetectors, converted into electrical signals, and then added together. It's okay. Experiments were conducted using the apparatus shown in FIG.

The configuration of each part is as follows. As the stimulable phosphor plate 11, the aforementioned 20Cfn square BaFCl:Eu phosphor plate was used.

The laser light source 15 has an output of 10 mw (7) He-N.
An e-laser was used.

The wavelength of the excitation light is 633 nm. As a photodetector, a 3-inch head-on photomultiplier tube with S-11 type spectral sensitivity distribution was used, and a 633nn photomultiplier tube was used in front of it.
The transmittance is 0.1% for light with a wavelength of 400r.
A filter with a transmittance of 80% was placed for a wavelength of 1 m.

The width of the light transmission means 12 is 20cm, the thickness is 5TWt1, and the length is 30C77! It was hot.

With this configuration, approximately 80% of the light emitted in front of the stimulable phosphor plate 11 could be collected, and approximately 90% of the light could be incident on the photodetector.

This means that the S/N ratio has more than doubled compared to the conventional device. The present invention having the above configuration efficiently condenses the weak light emitted from the stimulable phosphor plate by the scanning beam and makes it efficiently enter the photodetector using the light transmission means made of the light guide sheet. As a result, the light collection efficiency is significantly improved compared to conventional devices, and the S/N ratio can thereby be significantly improved, and the cost is significantly lower than that of conventional devices. It has major features in this respect.

The present invention scans light in a linear manner, and the reflected light or transmitted light (
In particular, it provides a means to efficiently condense light (scattered light).
Needless to say, it can be widely applied to all such purposes.

In addition, if there is a difference in light collection efficiency in the width direction of the light transmission means, for example, 0 Journal of the SM
PTE (JOumalOftheS.M.P.T.E.)
As described in Vol. 87, pages 209-213 (197 details), the one-difference difference is stored in a storage means, and the one-difference difference is subtracted from each output signal to cancel the one-difference difference. Technology is available to

[Brief explanation of the drawing]

Fig. 1 is a side view showing an embodiment of the present invention, Fig. 2 is a perspective view showing the main part of the light transmission means, and Figs. 3 and 4 show other examples of the light transmission means. The perspective view and FIGS. 5 and 6 are side views showing other embodiments of the present invention. 11, 20... Accumulative phosphor plate, 12...
・Light transmission means, 12a... Condensing surface, 13...
...Photodetector, 14...Light deflector, 15...
... Loser light source, 22, 23... Light detection system.

Claims (1)

[Claims] 1. In a radiation image information reading device that scans a stimulable phosphor plate with excitation light to read radiation image information recorded therein, A photodetector for detecting light, and a light transmission means disposed between the photodetector and the stimulable phosphor plate, the light transmission means being made of a light-guiding sheet-like material, one end of which is Radiation image information, characterized in that the radiation image information is provided next to the scanning line on the stimulable phosphor plate, and the other end is formed to match the shape of the light receiving surface of the photodetector and is provided next to the light receiving surface. reading device. 2. Claim 1, characterized in that the light transmission means are opposed to each other across a scanning line on a stimulable phosphor plate.
The radiographic image information reading device described in 2.