JPH0516780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a reading device for radiation image information stored and recorded on a stimulable phosphor sheet. The present invention relates to a radiation image information reading device that can avoid the effects of scattered radiation.

(Technical Background and Prior Art of the Invention) Certain phosphors are exposed to radiation (X-rays, α-rays, β-rays,
When irradiated with γ-rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor changes depending on the accumulated energy. is known to exhibit stimulated luminescence, and phosphors exhibiting this property are called stimulable phosphors.

Using this stimulable phosphor, radiation image information of a subject such as a human body can be transferred to a sheet having a layer of stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'').
Or just say "sheet". ) and record it in
This stimulable phosphor sheet is scanned with excitation light such as a laser beam to cause stimulated luminescence, and the generated stimulated luminescent light is read photoelectrically to obtain an image signal, and this image signal is processed to obtain a suitable diagnosis. A radiation image information recording and reproducing method for obtaining a radiation image of a subject has been proposed.
(For example, JP-A No. 55-12429, JP-A No. 56-11395,
(No. 55-163472, No. 56-104645, No. 55-116340, etc.) Below, an example of the radiation image information reading device used in the above-mentioned radiation image information recording and reproducing method is shown in the fourth example.
It is shown in the figure and its mechanism will be explained.

A laser beam 111a of a constant intensity emitted from a laser light source 111 as excitation light is made to enter a galvanometer mirror 112, and the galvanometer mirror 1
The laser beam is deflected and irradiated onto the sheet 113 so that the laser beam performs main scanning (scanning in a direction perpendicular to the plane of the paper) in the width direction of the sheet 113 placed below the sheet 12 . Since the sheet 113 is attracted onto, for example, an endless belt device 119 and conveyed in the direction of arrow A, the main scanning is repeated at an angle substantially perpendicular to this sub-scanning, and the entire surface of the sheet 113 is covered with a two-dimensional laser beam 111a. A target scan is performed.

As the laser beam 111a scans, the portion of the sheet irradiated with the laser beam 111a emits stimulated light according to the image information stored there, and this emitted light is emitted in parallel to the main scanning line in the vicinity of the sheet. Transparent light condenser 11 on which an incident end surface 114a is formed
The light enters the light condenser 114 from the incident end surface 114a of No. 4.
This light condenser 114 has a front end surface 114b located near the sheet 113 formed in a flat shape, and
It is formed so as to gradually become cylindrical toward the rear end side, and becomes approximately cylindrical at the rear end 114c and is connected to the photomultiplier 115 provided on the exit end surface 114d, so that the light from the entrance end surface 114a The entered stimulated luminescent light is transmitted to the rear end 11
4c and transmitted to the photomultiplier 115 via a filter (not shown) that selectively transmits the stimulated luminescent light. In the photomultiplier 115, the stimulated luminescence light is converted into an electrical signal, and the obtained electrical signal is sent to the image information reading circuit 1.
After being sent to 16 and processed, it is outputted as a visible image on a CRT, recorded on a magnetic tape, or directly recorded as a hard copy on a photosensitive material or the like.

By the way, before the stimulable phosphor sheet is sent to the above-mentioned reading device, a radiation image of the subject is accumulated and recorded in the imaging device. However, if this imaging device is placed near a reading device or incorporated into the same device, scattered rays of radiation used for imaging may have an adverse effect on the reading of image information.

That is, as shown in FIG.
When radiation 121a emitted from a radiation source 121 is irradiated onto a subject 122 in order to record radiation image information at 0, radiation scattering (Compton scattering, Thomson scattering) occurs. Scattered radiation 121b (hereinafter referred to as
The scattered rays (simply referred to as scattered rays) travel in three-dimensional random directions, and some of them scatter outside the imaging device. For this reason, when the imaging device and the reading device are close to each other as shown in the figure, these scattered rays hit various members (not shown) outside the imaging device and are further scattered in different directions. The laser beam 11 passes through the above-mentioned light condensing body and is on the sheet 113.
Excitation is performed when the scanning position 1a is reached. When excitation is performed by the scattering 121b in addition to the laser beam 111a, the excitation energy becomes larger than when excited by only the laser beam, and the stimulated luminescence light emitted from the sheet is The luminescence intensity level is higher than that of the stimulated luminescence light emitted from the part. Furthermore, the above-mentioned light condenser is generally made of acrylic or the like, and the light condenser itself becomes a scatterer, and as shown in the figure, the scattered rays that hit the light condenser are transferred to the sheet 113 after being read. Scatter it where it doesn't exist. When these scattered rays reach the sheet 113, stimulated luminescence light is generated from the sheet 113 due to the excitation of the scattered rays, and this stimulated luminescence light enters the light condenser and becomes noise in the reproduced image, or becomes a laser beam. Since the accumulated radiation energy decreases before the reading is performed, problems such as density unevenness occur in the reproduced image occur. Therefore, if radiographic image information is being read in the vicinity of the reading device, the scattered radiation will cause various adverse effects as described above, and the overall quality of the reproduced image will deteriorate. There is a problem with putting it away.

Scattered radiation emitted from the photographing device as described above becomes a problem as the reading device is closer to the photographing device. Transport means and image recording section (photographing section) located in the circulation path
and an image reading section in the circulation path, and the image reading section in the circulation path absorbs residual radiation energy on the sheet prior to recording an image on the sheet after the image reading has been performed in the image reading section. A radiation image information recording/reading device (hereinafter referred to as a built-in type device) (hereinafter referred to as a built-in type device) (Japanese Patent Application Laid-Open No. 2002-120001) is a radiation image information recording/reading device (hereinafter referred to as a built-in type device), in which an erasing section for emitting data is incorporated into one device, and the sheet is circulated between the respective sections for repeated use. 59−
No. 192240, etc.), the reading section, which is a reading device, and the imaging section, which is a photographing device, are incorporated into the same device and are arranged close to each other.
The influence of scattered radiation on the reading of image information is particularly large.

(Object of the Invention) The present invention has been made in view of the above problems, and it is possible to reduce the influence of scattered radiation regardless of the positional relationship with the imaging device, and to accurately read radiographic image information. The object of the present invention is to provide a radiation image information reading device.

(Structure of the Invention) The radiation image information reading device of the present invention is characterized in that the surface of the above-mentioned light condenser except for the entrance end face and the exit end face is covered with a radiation shield. By covering the surface of the condenser with a radiation shield as described above, the scattered radiation that reaches the condenser is blocked and passes through the condenser to the vicinity of the scanning position of the excitation light on the sheet. Inconveniences such as when the light is scattered or hits a light condenser and reaches areas other than the scanning position on the sheet and excites these areas will no longer occur.

In addition, if the radiation shielding material has radiation shielding properties, it can achieve the extremely effective effect in practice as described above, but if the radiation shielding material has light blocking properties as well as shielding properties, More preferred.

In other words, it is difficult to block all of the scattered rays with the shielding material on the condenser, and a very small amount of the scattered rays reach the sheet without passing through the condenser, resulting in stimulated luminescence from the sheet. Sometimes light is generated. This stimulated luminescence light is emitted at a position relatively far away from the scanning position of the excitation light, and even if there is no risk of it entering the incident end face of the light collector, some of it is emitted from the circumferential surface of the light collector into the interior of the light collector. incident on . Therefore, if the radiation shielding material also has shielding properties, it is possible to prevent these stimulated luminescence lights from entering from the peripheral surface.

Furthermore, when radiation is irradiated with an imaging device, instantaneous luminescent light is emitted from the entire surface of the sheet, but even after the radiation irradiation is cut off, the instantaneous luminescent light does not disappear immediately, but fades and remains as an afterglow. It is known that it continues to emit light. Therefore, if the sheet being read by the reading device has just been photographed, the afterglow of the instantaneous light emission will be emitted from the entire surface of the sheet, and some of this afterglow will be collected from the circumferential surface of the light condenser. It enters the light body and becomes a noise component. Therefore, if the shielding material also has a light-shielding property, the influence of the afterglow of the instantaneous emitted light can be greatly reduced.

Lead foil is an example of a shielding material that also has a light-blocking property, and when lead foil is used, it is desirable to interpose a sponge or the like in order to prevent damage to the light collector. Furthermore, in the present invention, covering the light condensing body with a shielding object is intended to substantially prevent scattered radiation from reaching the light condensing body itself and reduce the influence on reading. This includes cases where a small portion of the surface of the condenser is not covered with a shield, or there is a slight gap between the condenser and the shield, to the extent that this does not reduce the Needless to say.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the outline of a built-in type radiographic image information recording/reading device equipped with a radiographic image information reading device according to an embodiment of the present invention. Note that since the reading device according to this embodiment is built into a recording/reading device, it will be hereinafter referred to as a recording section for convenience.

As shown in the figure, the recording/reading apparatus has an L-shaped circulation path 1, and the stimulable phosphor sheet 13 is circulated through this circulation path 1 by a circulation conveyance means 3 such as a conveyance roller or a conveyance belt.

Above the circulation path 1 is an image recording section (photographing section) 2.
0, an image reading section 10, and an erasing section 30 are sequentially arranged in the sheet traveling direction (direction of arrow A).

In the photographing section 20, the radiation 21a emitted from the radiation source 21 passes through the subject 22 and enters the sheet 13 from the back side of the sheet 13, so that radiation image information of the subject is accumulated and recorded on the sheet 13. In the illustrated apparatus, the position of the photographing section 20 can be adjusted up and down.

The photographed sheet is conveyed along the circulation path in the direction of arrow A by a circulation conveyance means 3 such as a drive roller or a conveyance belt, and enters the image reading section 10 .

The image reading unit 10 includes an excitation light source 11 that emits excitation light 11a such as a laser beam that scans the sheet 13, and an optical deflector 12 such as a galvanometer mirror that reflects and deflects the excitation light 11a onto the sheet 13. scans the sheet 13 conveyed in the direction of arrow A two-dimensionally. The excitation light 11
Stimulated luminescence light corresponding to the image information accumulated and recorded there is generated from the irradiated part of the sheet a.
This stimulated luminescence light enters the light condenser 14 made of acrylic from its entrance end surface 14a. The condenser 14 transmits the stimulated luminescent light incident from the incident end face 14a to the exit end face 14d, and the stimulated luminescent light is transmitted to the photomultiplier 1 connected to the exit end face 14d.
5 and is read out photoelectrically to obtain an electrical image signal based on the stimulated luminescent light.

The sheet that has been read in the reading section 10 is sent to the erasing section 30 by the circulating conveyance means 3.

The erasing section 30 is provided with a large number of erasing light sources 31 such as fluorescent lamps, and the sheet 13 is irradiated with visible light from the erasing light sources 31 from the front side to emit residual radiation energy on the sheet.

The erased sheet is sent to the photographing section 20 again by the circulating conveyance means 3.

In this way, on the circulation path 1, there are an imaging section, a reading section,
In an apparatus that is provided with an erasing section and in which sheets are circulated between sections and used repeatedly, it is common to circulate a plurality of sheets at the same time to proceed with photographing, reading, etc. at the same time. Therefore, while the image information is being read in the reading unit,
When radiation is irradiated in the imaging section, since the reading section and the imaging section are close to each other, it is conceivable that the scattered rays of the radiation will adversely affect the reading. Therefore, in order to reduce the influence of this scattered radiation, in the present invention, the light condensing body 14 is
Surface 14 excluding the entrance end surface 14a and the exit end surface 14d
e is covered by a radiation shield with lead foil. The structure and function of this radiation shield will be explained with reference to FIGS. 2 and 3.

As shown in FIG. 3, the radiation shield 16 is made by covering both sides of a lead foil 16a with a sponge 17.The lead foil 16a has shielding and light shielding properties, so it can shield scattered radiation and It blocks light to prevent scattered radiation and the like from adversely affecting reading. The sponge 17 is provided to prevent lead foil from damaging the light collector, and foamed polyethylene or the like may be used instead of the sponge.

By providing the radiation shield 16 as described above, as shown in FIG. 2, the scattered rays 21b that reach the condenser are blocked and are prevented from passing through the condenser or hitting the condenser. This prevents the particles from being scattered on the sheet. Therefore, in the reading section, unspecified portions on the sheet are hardly excited by scattered radiation, and highly accurate reading can be achieved only by excitation of the excitation light 12. In addition, in this embodiment, the radiation shield 16 is shielded by lead foil, and since the lead foil has both shielding and light shielding properties, the light concentrator 14 has
Light is also prevented from entering from surfaces 14e other than the incident end surface 14a. That is, in the recording/reading apparatus shown in FIG. 1, the sheet irradiated with radiation in the imaging section 20 is immediately conveyed to the reading section and read, so that the above-mentioned instantaneous light emission afterglow 18a is visible from the entire surface of the sheet. often occurs. Further, a part of the scattered radiation 21b is transmitted to the light condenser 14.
However, these afterglow 18a and stimulated luminescence light 18b are blocked by the radiation shield 16, Concentrator surface 1
4e is prevented from entering the condenser. Therefore, if a reproduced image is obtained based on the image information read by the reading section, a reproduced image of good quality without noise or unevenness can be obtained.

It should be noted that the shielding material used as a radiation shield is not limited to the lead foil used in this embodiment, and the sheet to be read must be one that has been read for a predetermined period of time or more after the photographing and is free of instantaneous light emission afterglow. In cases where there is little influence, the light-shielding property of the shielding material is not necessarily required. Furthermore, the reading device of the present invention has a built-in type recording/reading device that circulates sheets as described above.
Needless to say, the present invention is not limited to one that is incorporated together with an imaging device, but can be used as any reading device in which there is a concern about the influence of scattered radiation from the imaging device.

(Effects of the Invention) As explained in detail above, according to the radiation image information reading device of the present invention, since the surface of the condenser is covered with a radiation shielding material, scattering occurs even when placed close to the imaging device. It becomes possible to perform highly accurate reading with less influence of lines. Therefore, even if the imaging device and the reading device are installed in the same device in close proximity, such as in a built-in type recording/reading device, accurate reading with almost no influence of scattered radiation within the reading device can be achieved. As a result, reproduced images of high quality without density unevenness or noise can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a radiation image information recording/reading device equipped with a radiation image information reading device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a portion near the condenser in the reading device, and FIG. The figure is a sectional view showing the configuration of a radiation shield, and FIG. 4 is a side view showing an outline of a conventional reading device. 11...Excitation light source, 11a...Excitation light, 14...
...Concentrator, 14a...Incidence end face, 14d...Emission end face, 14e...Surface, 16...Radiation shield,
16a...Lead foil, 21b...Scattered radiation.

Claims (1)

[Scope of Claims] 1. Main scanning means for main-scanning a stimulable phosphor sheet on which a radiation image of a subject is stored and recorded using excitation light to generate stimulated luminescence light from the sheet; a sub-scanning means that performs sub-scanning by relatively moving in a direction substantially perpendicular to the main-scanning direction; an entrance end surface disposed close to the sheet and extending in that direction along the main scanning line; an exit end face for emitting the stimulated luminescent light, and a light collector for guiding the stimulated luminescent light incident from the input end face to the exit end face; and a photodetector connected to the exit end face of the light collector. A radiation image information reading device comprising: a surface of the light condensing body other than the incident end face and the exit end face is covered with a radiation shielding material. 2. The radiation image information reading device according to claim 1, wherein the radiation shield is lead foil covered with sponge on both sides.