JPS6163155A - Reader of x-ray picture information - Google Patents

Abstract

PURPOSE:To read properly a highly clear picture by providing a light absorbing board for inhibiting the light except a main scan line at the incident end surface of a condensing body and installing a highly directional grid for transmitting only the light on the scan line. CONSTITUTION:A laser scan light 1b as excited light is mainly scanned in the direction of an arrow A along a scan line 3a on a sheet 3, and an accelerated phosphorescence light 1c is parabolically emitted from the scan position on the sheet 3 on which the laser scan light 1b is made incident. The light 1c is made incident on an incident end surface 4a through a highly directional grid 5, which is provided on the incident end surface 4a. Since the grid 5 has plural light absorbing boards 5a for absorbing incident light, only the light for passing through a light transmitting layer 5b between the boards 5a is led to a light condensing body 4. Since the residual light of the accelerated phosphorescence light from a part 3A before scanning on the sheet 3 and a part 3B after the scanning is made incident on the grid at the angle different from the light emitted from the scan line, the greater amount of the residual light is absorbed by the board 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a reading device for radiation image information accumulated and recorded on a stimulable phosphor sheet, and more particularly, to a device for reading radiation image information accumulated and recorded on a stimulable phosphor sheet, and more particularly, to a device that emits light according to the image information accumulated and recorded. The present invention relates to a radiation image information reading device that can accurately read stimulated luminescence light.

(Technical Background and Prior Art of the Invention) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, etc.), part of this radiation energy is absorbed into the phosphor. It is known that when this phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. The body is called a storage fluorophore.

By using this stimulable phosphor, radiation image information of a subject such as a human body can be collected on a sheet containing a stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'' or simply ``sheet J''). ), this stimulable phosphor sheet is scanned with excitation light such as a laser beam to cause it to emit light, and the resulting stimulated emitted light is read in a charged manner to obtain an image signal. A radiographic image information recording and reproducing method has been proposed in which a radiographic image of a subject with good diagnostic suitability is obtained by processing signals.

(For example, JP-A-55-12429, JP-A-56-1139)
No. 5, No. 55-163472, No. 56-104645
(No. 55-116340R, etc.) An example of a radiation image information reading device used in the above radiation image information recording and reproducing method is shown in FIG. 3, and its structure will be explained below.

Laser light 101a with a constant intensity is made to enter the galvanometer mirror 102 from the laser light source 101 as excitation light, and the galvanometer mirror 102 causes the laser light to main scan (in the direction of the arrow) in the width direction of the sheet 103 placed below the galvanometer mirror 102. direction scanning),
The laser beam is deflected and irradiated onto the sheet 103. sheet 1
03 is attracted onto the endless belt device 109 and conveyed in the direction of arrow B, so that the main scanning is repeated at an angle substantially perpendicular to the sub-scanning, and the laser beam 101b covers the whole of the sheet 1.03. A dimensional scan is performed.

The laser beam 101b follows the scanning by the laser beam 101b.
The irradiated area of the sheet emits stimulated light according to the image information accumulated and recorded there, and this emitted light is collected by a transparent condensing light beam having an incident end surface 104a parallel to the main scanning line near the sheet. From the incident end surface 104a of the body 104 to the light condenser 1
Enter 04.

The light condenser 104 has a front end 104b located near the sheet 103 that is flat and gradually becomes cylindrical toward the rear end.
04c, it has a substantially cylindrical shape and is connected to the photomultiple 105 provided on the exit end surface, so that the entrance end surface 1
The stimulated luminescence light entering from 04a is collected at the rear end portion 104c and transmitted to the photomultiplex 105 via a filter (not shown) that selectively transmits the stimulated luminescence light. In the photomultiplier 105, the stimulated luminescence light is converted into an electrical signal, and the obtained electrical signal is sent to the image information reading circuit 106 for processing, and then outputted as a visible image to the CRT 107, for example, or to a magnetic chip. 7108, or directly recorded as a hard copy on a photographic material or the like.

During the above reading, the light condensing body 104
Since a is parallel to the main scanning line and has a width that spans almost the entire width of the sheet 103, all light from a location where the incident end surface 104a can be seen is read, and stimulated luminescence from the location where the laser beam 101b is incident is detected. Not just light
All light from other locations on the sheet 103 that can see the incident end surface 104a is also read. The afterglow emitted by the sheet 103 poses a problem as light other than the stimulated luminescent light that enters the incident end surface 104a and is read. This afterglow includes instantaneous luminescence afterglow and stimulated luminescence afterglow.

Instantaneous light emission afterglow is a phenomenon in which the instantaneous light emitted from a sheet when radiation is irradiated to record image information on the sheet does not disappear and continues to emit light while attenuating even after the radiation irradiation is stopped. say. The characteristics of this instantaneous light emission afterglow vary depending on the type of stimulable phosphor used in the sheet, but are generally as shown in FIG. 4. FIG. 4 is a graph showing luminescence intensity on the vertical axis and time (1) on the horizontal axis, and shows radiation irradiation at time 1. When the irradiation is stopped after Δt2 hours from t2 to t2, the intensity of the instantaneous emitted light with emission intensity "A" does not immediately reach O, but increases along an exponential function with a gradually increasing time constant. The instantaneous luminescence afterglow is shown to decrease.

Specifically, the attenuation of the luminescence intensity of this instantaneous luminescence afterglow is, for example, approximately 180 seconds after radiation irradiation 0=J (i.e., (j3
At the time 11 i 3Jl (jz>=180 seconds)
The luminescence intensity "B" of the instantaneous luminescence afterglow is approximately 1 of the intensity of the stimulated luminescence light generated by excitation light scanning.
It will be about 04 times.

For this reason, after recording image information by irradiating radiation through a subject onto a sheet, if a predetermined amount of time elapses before this image information is read, the intensity of the instantaneous light emission afterglow will drop sufficiently and the afterglow will become negligible. Become. However, when reading radiation image information immediately after recording, the image information reading section is integrated into a radiation image information recording device, such as that disclosed in Japanese Patent Application No. 1983-66730, which was previously filed by the present applicant. When recording and reading are performed continuously, at high speed, and in large quantities using a device built into a radiographic image information recording device (Zunawara, radiographic image information recording device), instantaneous afterglow is used as well as stimulated luminescence. Reading occurs before the intensity has sufficiently attenuated, and the influence of instantaneous light emission afterglow on the read image information increases.

In addition, stimulated luminescence light is emitted from a very small area where the excitation light is incident, whereas instantaneous luminescence afterglow is emitted from IJJ.
Since the light is emitted from the entire surface irradiated with the line, from the incident end surface 104a of the condenser 104 shown in FIG. are captured at the same time and sent to the photomultiple 105. In this case, compared to the area of the area of the sheet 103 where the laser beam is irradiated, the area of the area where the incident end surface 104a of the light condenser 104 can be seen is extremely large! Therefore, as mentioned above, even if the intensity of the instantaneous afterglow becomes negligible compared to the intensity of the stimulated emitted light after a predetermined period of time has elapsed after radiation irradiation, the light transmitted to the photomultiplier 105 In this case, the amount of instantaneous light emission afterglow cannot be ignored.

On the other hand, stimulated luminescence afterglow refers to irradiation of excitation light (e.g., laser light) in order to read the radiographic image stored and recorded on the sheet to cause stimulated luminescence. This refers to a phenomenon in which emitted light does not disappear at the same time as it is interrupted, but continues to emit light even though it is attenuated. The characteristics of this stimulated luminescence afterglow vary depending on the type of stimulable phosphor used in the sheet, but are generally as shown in FIG. FIG. 5 is a graph in which the vertical axis shows emission intensity and the horizontal axis shows time (1), and the excitation light is measured from time t to 1. When irradiated for △1° and then cut off, the stimulated luminescence light with an emission intensity of "CI+" does not change straight to O, but changes along an exponential function with a gradually increasing time constant. The intensity decreases (that is, the intensity decreases rapidly at first, and then the rate of decrease gradually decreases). is about 1 microsecond.In other words, the time for the emission intensity to become 1/e (D/C=1/e) (
1:6 'I's) is about 1 microsecond. By the way, generally speaking, the speed at which the excitation light is scanned (main scanning) on the stimulable phosphor sheet by a galvanometer mirror is:
Since it is about 50 Hz, it takes about 20.0 Hz for one scan.
It takes 00 microseconds. Therefore, the intensity of the stimulated luminescence afterglow, which decays along an exponential function with an initial time constant of 1 microsecond, is an order of magnitude smaller than the intensity of the stimulated luminescence light, and the stimulated luminescence afterglow at each point is The strength is almost negligible.

However, stimulated luminescence light is emitted from a very small area where the excitation light is incident, whereas stimulated luminescence afterglow is emitted from all areas scanned by the excitation light. From the incident end surface 104 a of the light body 104 , stimulated luminescence light and stimulated luminescence afterglow from all locations where the incident end surface 104 a can be seen are simultaneously taken in and sent to the photomultiple 105 . In this case sheet 103
Compared to the area of the area where excitation light enters and stimulates luminescence,
The area where stimulated luminescence afterglow occurs due to scanning of excitation light is extremely large, as in the case of instantaneous luminescence afterglow, so as mentioned above, the intensity of stimulated luminescence afterglow is smaller than the intensity of stimulated luminescence afterglow. Even if the amount of light transmitted to the photomultiplier 105 is negligible compared to the amount of light transmitted to the photomultiple 105, the optical manifestation of stimulated luminescence afterglow cannot be ignored.

The afterglow that is read at the same time as the stimulated luminescence light becomes a noise component in the image signal of the radiographic image, making it difficult to read accurate radiation image information.

In particular, instantaneous luminescence afterglow is a problem when reading radiation image information immediately after recording it on a stimulable phosphor sheet, and stimulated luminescence afterglow occurs when radiation image information is excited on a stimulable phosphor sheet on which a radiographic image has been recorded. This becomes a particular problem as the speed at which light scans becomes faster.

Next, Figures 6A and 6B show the influence of afterglow on image information.
This will be explained in detail using figures. Figure 6A is sheet 103
For example, Fig. 6A shows recorded radiation image information of a human head, and Fig. 6B shows excitation light (laser light) along line a.
The light ♀ transmitted to the photomultiple via the condenser when scanned by is shown with the position corresponding to the scanning of line a on the horizontal axis. In Fig. 6B, the preset that is actually transmitted to the photomultiple is shown by a broken line 9J1, and the afterglow (the sum of the instantaneous afterglow and the stimulated afterglow) out of the amount of light shown by the broken line 9J1 is shown by the dashed line 9J1. The dashed line 9,3 indicates the amount of stimulated luminescence, and the solid line 9
．． Indicated by z. That is, afterglow port 9J3 and stimulated luminescence ffi
9. The sum of z is the light m9Jl transmitted to the photomultiplier. This signal λ1 is converted into an electrical signal by a photomultiplier and then logarithmically transformed (LOG), and a reproduced image is obtained from this logarithmically transformed signal. In this case, the value is different when the light ♀9,1 transmitted to the photomultiplier is converted into an electric signal and logarithmically converted, and when only the stimulated luminescence 9z2 is converted into an electric signal and this is logarithmically converted, and the value is different, If an image is reproduced using the value of perfect λ5, the reproduced image will be different from the actual image.

That is, the reproduction (i! ii face is inaccurate bt, < becomes unclear and is a serious problem in terms of diagnosis 11/i suitability 4).

In addition to the above-mentioned afterglow problem, a part of the laser beam 101b is reflected on the surface of the sheet 103, and this reflected light is further reflected on the incident end surface 104a of the condensing VK 104, and the laser beam 101b is reflected on the surface of the sheet 103.
In some cases, the phosphor returns to an unspecified surface and excites the 815-minute phosphor, causing stimulated luminescence. When the stimulated luminescence light generated from outside the scanned area is read, ii!
ii@ It becomes a noise component of the signal and reduces the sharpness of the image.

(Purpose of the Invention) The present invention has been made in view of the above-mentioned problems, and is aimed at preventing instantaneous luminescence afterglow, stimulated luminescence afterglow, and stimulated luminescence light generated from outside the scanned area from reaching the condenser. The object of the present invention is to provide a radiation image information reading device that can prevent the radiation from entering, reduce the shadow effect on the above-mentioned light reading, and produce accurate and highly sharp images. .

(Structure of the Invention) The radiation image information reading device of the present invention allows a light beam from above a scanning line during main scanning to pass through an incident end face of a condenser, and a large number of light absorption plates This system is characterized by the provision of a highly directional grid that absorbs and prevents passage.

Here, the highly directional grid refers to a grid that is arranged substantially radially with small gaps oriented toward the scanning line, and extends in the main scanning line direction, and includes a large number of light absorption plates. (The light-absorbing plate does not necessarily have to be in the form of a plate; for example, it may be a light-absorbing layer formed in a transparent material such as plastic, but for convenience, this is collectively referred to as a light-absorbing plate. ) Due to this grid, light emitted from above the scanning line passes between the light absorption plates and enters the condenser without entering the light absorption plate, but light emitted from positions other than the scanning line is emitted from above the scanning line. Since the light is incident on the grid at a different angle, most of the light is absorbed by the light absorption plate and is prevented from entering the light collector.

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

FIG. 1 is a perspective view showing a structure near a scanning section of a reading device according to an embodiment of the present invention, and FIG. 2 is a sectional view thereof.

The stimulable phosphor sheet 3 is moved in the direction of arrow B for MI constant scanning. Rade scanning light 1b as excitation light is main-scanned on the sheet 3 in the direction of the arrow along the scanning line 3a, and the scanning position U on the sheet 3 irradiated with the laser scanning light 1b is
Stimulated luminescence light 1C is radially emitted from the. This stimulated luminescence light 1C enters the incident end surface 4a of the condenser 4 provided along the scanning line, but a highly directional grid 5 is provided on this incident end surface 4a, and the The exhaustion light 1C passes through this highly directional grid 5 and enters the incident end face 4a.

The highly directional grid 5 is radially inclined toward the main scanning line 3a during scanning, and has a large number of light absorption plates 5a'x extending in the direction of the main scanning line and arranged at appropriate intervals to absorb incident light. The light transmission fM5 between the light absorption plates 5a
Only the light that has passed through b is guided to the Ott condenser 4. This light transmitting IJ 5 b may be a transparent body such as glass or plastic, or may be a space.

As mentioned above, since the light absorption plate 5a is oriented radially toward the main scanning line, the light emitted from above the main scanning line 85 and its immediate vicinity and spread radially is absorbed by the light absorption plate 5a. Instead, the light passes through the light transmitting IM 5b and reaches the light condenser 4.

On the other hand, an afterglow 1A of instantaneous light emission during storage recording occurs from a portion 3A before scanning on the sheet 3, and an afterglow 1B from the exhaustion occurs from a portion 3B immediately after scanning.

These afterglows are generated at a different angle from the light emitted from the scanning line.
Since the light is incident on the highly directional grid 5, most of it is incident on the light absorption plate and absorbed, as shown by the broken line in FIG. Therefore, most of the afterglow does not reach the light condenser 4, and the influence of the afterglow on reading can be greatly reduced.

Further, even if a part of the reflected light generated by the laser scanning light b being reflected on the sheet 3 is reflected by the incident end surface 4a of the condenser, most of the reflected light is reflected on the light absorbing plate 5a before returning onto the sheet 3. Therefore, there is a very small possibility that the reflected light that is reflected by the input QJ and returns to the sheet will excite parts of the sheet other than the scanning position. Furthermore, even if the reflected light hits other surrounding members and excites parts other than the scanning position to produce stimulated luminescence light, the Iζ light emitted from other than the scanning position will be absorbed as in the case of afterglow. Plate 5a
Since the light is absorbed by the light, the adverse effect of reflected light on reading can be greatly reduced.

(Effects of the Invention) As explained above, according to the radiation image information reading device of the present invention, the light condenser is a person! l) By providing a highly directional grid on one end surface, almost no light other than that emitted from the scanning line enters the condenser, which greatly reduces the influence of afterglow on reading.
The influence of reflected light caused by part of the laser scanning light being reflected on the sheet surface can also be reduced, making it possible to obtain accurate and highly sharp images.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure near the scanning unit of a reading device according to an embodiment of the present invention, FIG. A schematic diagram showing an example of a radiation image information reading device. Fig. 4 is a graph showing the temporal characteristics of instantaneous emission afterglow. Fig. 5 is a graph showing the temporal characteristics of exhaustive emission afterglow. Fig. 6A is a graph showing the temporal characteristics of instantaneous emission afterglow. Fig. 6B shows the intensity of the emitted light transmitted to the photomultiplier via the condenser when the excitation light scans the sheet on which the radiographic image information of Fig. 6A is recorded. It is a graph. 1b...Laser scanning light 1C...Ti exhaust light 4...Concentrator 4a...Incidence end face 5.
...Product orientation grid 5a...Light absorption plate 5b...
・Light'fi passing H Figure 1 Figure 2

Claims (1)

[Claims] a 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 moving in a direction substantially perpendicular to the sheet; the sub-scanning means has an entrance end face disposed close to the sheet and extends in the main scanning direction, and transmits light incident from the entrance end face to an exit end face; In a radiation image information reading device consisting of a guiding light condenser and a photodetector connected to an exit end face of the light condenser, the incident end face of the light condenser is exposed to light from other than the scanning line during main scanning. A radiation image information reading device comprising a highly directional grid that has a large number of light absorbing plates that prevent light from passing through, and that allows only light from above the scanning line to pass through.