JPS61206361A - Residual image erasing device for storage fluorescent sheet - Google Patents

Abstract

PURPOSE:To eliminate useless light irradiation by using a linear light source irradiating light for residual image erasure over the entire width of a sheet, providing an energy distribution detecting means for detecting the distribution of residual radiant ray energy and controlling at least one of the linear light source and the moving means in response to the quantity of the residual radiant energy distribution to adjust the light irradiation amount to each part of the sheet. CONSTITUTION:A sheet moving means 20 for moving a storage fluorescent sheet 13 is driven by a variable speed motor 22. A picture information processing circuit 17 divides the sheet 13 into n sections of P1, P2,...Pn based on an electric signal from a photomultiplier 16 prior to the residual image erasure of the sheet 13 to obtain the maximum value of the luminescent optical energy level of each section and a motor control circuit 23 obtains the irradiation time required to obtain the erasure light irradiation quantity of each section to decide the moving speed of the sheet carrying means 20.

Description

Detailed Description of the Invention (Field of the Invention) The present invention accumulates and records radiation image information on a stimulable phosphor sheet, then irradiates it with excitation light, and performs stimulated luminescence according to the accumulated and recorded image information. It is used repeatedly in a radiation image information recording and reproducing method that detects the light that is transmitted, reads the image information, converts it into an electrical signal, and then performs signal processing and converts the read image information into a visible image and reproduces it. The present invention relates to a device for effectively erasing afterimages on a stimulable phosphor sheet.

(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, electron beams, ultraviolet rays, etc.), part of this radiation energy is absorbed by the phosphor. When the phosphor is then irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. A phosphor exhibiting such properties is called a stimulable phosphor.

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded on a sheet of stimulable phosphor, which is then scanned with excitation light to cause stimulated luminescence. A radiographic image recording and reproducing method has been proposed in which the radiographic image is read into a subject to obtain an image signal, and the image signal is processed to obtain a radiographic image of a subject that is suitable for diagnosis.
No. 29, No. 55-116340, No. 55-1'634
No. 72, No. 56-11395, No. 56-104645
number, etc.). This final image may be reproduced as a hard copy or on a CRT. In such a radiation image recording and reproducing method, a stimulable phosphor sheet (strictly speaking, it can take various forms such as a panel or a drum, but is collectively called a "sheet") is used. ) is economical to use repeatedly.

The accumulated radiation energy caused by the recorded radiographic image information should be erased if sufficient intensity of excitation light is applied during reading, but in reality, it cannot be completely erased only by the excitation light applied during reading. . Therefore, when the stimulable phosphor sheet is repeatedly used, there is a problem in that the previously recorded image remains and becomes noise during the next reading.

The above-mentioned afterimage is caused by, for example, as shown in Japanese Patent Application Laid-Open No. 11392/1983, before recording radiation image information on the sheet, the sheet is exposed to light of a wavelength including the excitation light wavelength range of the phosphor. It can be extinguished by excitation to release enough of the accumulated radiation energy. In order to more completely erase the afterimage, the amount of light irradiation (
In other words, the illuminance (x time) may be set as large as possible, but in consideration of energy saving, shortening of erasing time, and the life of the erasing light source, there is also a demand to keep the above-mentioned light illuminance 9A1m to the minimum necessary. In view of the above points, the present applicant has proposed an afterimage erasing method in which the residual energy level accumulated in the sheet is detected and the amount of erasing light irradiated is increased or decreased depending on the magnitude of this level (Unexamined Japanese Patent Publication No. Showa 5
No. 8-80633).

By performing the above-described control, it is possible to set a necessary and sufficient amount of light irradiation for each sheet, and when considered on a sheet-by-sheet basis, both of the above-mentioned contradictory requirements can now be satisfied.

However, even in a single stimulable phosphor sheet, there are parts where the accumulated radiation energy (therefore residual radiation energy) is high and there are parts where it is low, so some parts of the sheet are exposed to an unnecessarily large amount of light. Become.

(Objective of the Invention) The present invention provides an afterimage erasing device for a stimulable phosphor sheet, which eliminates unnecessary light irradiation within a single sheet as described above, and thus achieves significant energy saving effects and erasing time shortening effects. The purpose is to provide

(Structure of the Invention) The afterimage erasing device for a stimulable phosphor sheet of the present invention is characterized in that in a normal radiation image of a human body, etc., a radiation-free background 2 is located on both sides of a subject 1, as shown in FIG. , furthermore, there is a bone part 3 in the subject 1 with a small amount of transmitted radiation,
As in, the specified direction △ (in this case, the left and right direction in the figure)
This was obtained based on the knowledge that in many cases the amount of radiation energy accumulated changes during the process, and as a light source that emits erasing light, it is arranged to extend in the width direction of the sheet perpendicular to the above-mentioned predetermined direction and cover the entire width of the sheet. Using a linear light source that irradiates light for erasing the afterimage, the sheet and the linear light source are moved relative to each other in the predetermined direction by a moving means in order to irradiate the sheet with erasing light over the entire length of the sheet. move it,
An energy distribution amount detection means for detecting the distribution of residual radiation energy in the predetermined direction is provided, and a control means receiving the output of the energy distribution amount detection means controls at least one of the linear light source and the moving means. This method is characterized in that the amount of light irradiated to each portion of the sheet is controlled to be increased or decreased depending on the amount of residual radiation energy distribution in each portion in a predetermined direction.

Note that the residual radiation energy of the stimulable phosphor sheet has a correlation with the energy of stimulated luminescence light emitted from the sheet during image reading, so the residual radiation energy distribution amount can be detected from the image information reading signal. However, it is also possible to independently provide a photodetector similar to the photodetector for reading image information for detecting the residual energy distribution, and obtain the residual energy distribution from the output of the photodetector.

Furthermore, JP-A-58-67241 and JP-A No. 58-83937
In the issue, there is a reading operation (hereinafter referred to as ``pre-reading'') for grasping the accumulated recorded information of the stimulable phosphor prior to the reading operation for reproducing radiation image information (hereinafter referred to as ``main reading''). It has been proposed to set the reading gain in the main reading to an appropriate value based on the accumulated recorded information obtained by this pre-reading, or to perform appropriate signal processing on the image signal obtained by the main reading. In general, the amount of radiation energy stored and recorded in the stimulable phosphor sheet before pre-reading is proportional to the amount of residual radiation energy remaining and stored in the stimulable phosphor sheet after main reading, so the residual radiation from the read signal during pre-reading is The energy distribution may also be determined.

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

FIG. 2 shows an apparatus according to a first embodiment of the present invention.

First, image reading performed by the apparatus of this embodiment before erasing afterimages will be described.

Laser light 1 with a constant intensity is emitted from a laser light source 10 as excitation light.
1 is made incident on the galvanometer mirror 12, and by this galvanometer mirror 12, the galvanometer mirror 1
The laser beam is deflected and irradiated onto the sheet 13 so that the laser beam performs main scanning (scanning in the direction of arrow B) in the width direction of the sheet 13 placed below the sheet 13. Furthermore, since the sheet 13 is held on a conveying device 14 such as an endless belt device and conveyed in the direction of arrow C, main scanning is repeated at an angle substantially perpendicular to the sub-scanning, and the entire surface of the sheet 13 is covered with laser light. 11 is performed. Therefore, the portion of the sheet that is irradiated with the laser beam 11 as it is scanned by the laser beam 11 emits stimulated light with an intensity that corresponds to the accumulated and recorded image information, and this emitted light is transmitted to the main scanning line near the sheet 13. The light enters the light condenser 15 from the upper incident end surface 15a of the transparent light condenser 15 in which the incident end surface 15a is formed in parallel.

This light condenser 15 has a front end 15 located near the sheet 13.
b is formed into a planar shape and gradually becomes cylindrical toward the rear end side, and the rear end portion 1
Since it has a substantially cylindrical shape at 5c and is connected to the photomul 16, the stimulated luminescence light entering from the incident end face 15a is collected at the rear end 15c and transmitted to the photomul 16. In the photomultiplier 16, the stimulated luminescent light is converted into an electrical signal, and then the electrical signal is sent to the image information processing circuit 17.

The image information processing circuit 17 processes and outputs the electric signal, and although not shown in the figure, for example, a CRT
It can be outputted as a visible image, recorded on a magnetic tape, or directly recorded as a hard copy on a photosensitive material.

The stimulable phosphor sheet 1.3, on which the radiation image has been read as described above, is sent via a conveying means 18 such as an O-ra to a sheet moving means 20 comprising, for example, an endless belt device. At this time, stimulable phosphor sheet 1
3, the sheet is sent to the sheet moving means 20 in a direction in which the direction in which the accumulated radiation energy level changes (predetermined direction A) is parallel to the direction of movement by the sheet moving means 20, as explained in FIG. . This seat moving means 20
At a position close to and facing the upper stimulable phosphor sheet 13,
A linear light source 21 is arranged at right angles to the movement direction. This linear light source 21 is, for example, JP-A-56-11
As shown in No. 392, the excitation light wavelength range of the stimulable phosphor sheet 13 emits light of a constant intensity including light in the wavelength range: After reading, the stimulable phosphor sheet 1
The radiation energy remaining in 3 is released and the afterimage is erased. The total length of the linear light source 21 is set longer than the total width of the stimulable phosphor sheet 13, and the stimulable phosphor sheet 13 is moved by the sheet moving means 20 and passes in front of the linear light source 21 over its entire length. Therefore, the afterimage on the entire surface of the sheet 13 is erased.

The sheet moving means 20 for moving the stimulable phosphor sheet 13 as described above is driven by a variable speed motor 22,
The variable speed motor 22 is configured to have its rotation speed controlled by a motor control circuit 23. The image information processing circuit 17 also serves as energy distribution matrix detection means for detecting the distribution ω of residual radiation energy in the stimulable phosphor sheet 13. The image information processing circuit 17, as shown in FIG. It is divided into n sections of Pl, P2, .

As described above, this stimulated emission light energy level has a correlation with the residual radiation energy level after image reading (that is, after stimulated emission). Therefore, based on this correlation, the image information processing circuit 17 calculates the maximum residual radiation energy level from the maximum stimulated emission light energy level of each section, and controls the signal S1 indicating the maximum residual radiation energy level of each section by motor control. Output to the circuit 23. Upon receiving this signal S1, the motor control circuit 23 determines the erasing light irradiation amount (illuminance x time) required to almost completely emit the maximum residual radiation energy for each section. Here, since the illumination intensity of the linear light source 21 is given as constant, the motor control circuit 23 calculates the irradiation time necessary to obtain the above erasing light irradiation amount in each section, and from this required irradiation time, the sheet moving means 20 Find the moving speed of.

The fact that the front end of the stimulable phosphor sheet 13 has reached near the front of the linear light source 21 is detected by, for example, a photoelectric position sensor 24, and a position signal S2 is input from the sensor 24 to the motor control circuit 23. The variable speed motor 22 is rotated at a constant speed until it receives the position signal S2, but
When the position signal S2 is input to the motor control circuit 23, it receives the rotation speed sub-part signal S3 from the motor control circuit 23, and the rotation speed is increased to tlJm. This rotational speed control signal S3 is applied to each section P1 obtained by the motor control circuit 23 as described above.
, P2, . . . Pn, the moving speed of the sheet moving means 20 is set so as to obtain the required irradiation time for each of Pn.

Therefore, the stimulable phosphor sheet 13 is divided into sections P1 and P2.
,...The moving speed is controlled for each Pn, and each section P1, P
2, . . . pn receive sufficient erasing light irradiation so that their maximum residual radiation energy is almost completely released.

When all the sections P1, P2, .

If the sheet movement speed is changed for each section P1, P2,...Pn in one stimulable phosphor sheet 13 as described above, the parts with a low residual radiation energy level will be exposed to unnecessary long erasing light irradiation. There is no longer any linear light a
The power consumption of the i21 can be suppressed to the necessary minimum, and the time required to erase the afterimage can also be shortened.

In addition to the straight tube-shaped light source, the linear light source 21 may include a plurality of point light sources 30 arranged in a row like a linear light source 32 shown in FIG. A device formed to emit light may also be used. Further, the stimulable phosphor sheet 13 is left standing and the linear light 11121
The moving speed of the linear light source 21 may be controlled.

Furthermore, in the embodiment described above, the image information processing circuit 1
7 serves as an energy distribution amount detection means for detecting the distribution amount of residual radiation energy in six directions of the sheet 13, but the motor control circuit 23 may also serve as the energy distribution amount detection means, or image information Processing circuit 17
The energy distribution detection means may be provided separately and independently from the motor control circuit 23 (in these cases, the electrical signal obtained by reading is transmitted directly from the photomultiple 16 or through the image information processing circuit 17). (via the motor control circuit 23 or energy distribution detection means). Furthermore, for example, the image information processing circuit 17 determines the maximum value of the stimulated luminescence light energy level of each section,
The image information processing circuit 17 and the motor control circuit 23 may each share the function of the energy distribution detection means, such that the motor control circuit 23 determines the maximum value of the residual radiation energy level of each section based on this.

In the actual mode described above, the amount of erasing light irradiation on each part of the sheet is set to the necessary and sufficient amount by changing the erasing light irradiation time. The relative moving speed between the sheet and the linear light source may be constant, and the erasing light illuminance may be controlled. FIG. 4 shows a second embodiment of the invention so formed.
1 shows an embodiment device. In the apparatus of this embodiment, the sheet moving means 20 is rotated at a constant speed to move the stimulable phosphor sheet 13 at a constant speed. A signal S1 indicating the maximum residual radiation energy level of each section from the image information reading circuit 17 and a position signal S2 output from the position sensor 24 are input to the light source control circuit 40. This light source control circuit 40 operates in the same way as the motor control circuit 23 described above for each section P1, P2, .
... Find the necessary and sufficient amount of erasing light irradiation (illuminance x time) for pn. In this case, since the irradiation time is given by the moving speed (constant) of the stimulable phosphor sheet 13, the required illuminance can be determined. Illuminance control signal S representing this required illuminance
4 is input to a light source drive circuit 41, and the linear light source 21 is controlled to be lit at a light emission intensity that provides the above-mentioned required illuminance. Also in this second embodiment, the power consumption of the linear light source 21 is suppressed to the necessary minimum.

Note that the illuminance control of the linear light source 21 in the second embodiment and the movement speed control (irradiation time control) of the stimulable phosphor sheet 13 or the linear light source 21 as shown in the first embodiment are stepless. Alternatively, it may be determined where the residual radiation energy level in each section P1, P2, ...pn of the stimulable phosphor sheet 13 falls within a preset rank, and the linear light source 2
The light emission intensity or irradiation time of step 1 may be changed stepwise.

Further, the residual radiation energy level of the stimulable phosphor sheet 13 is detected using the read image signal as in the first and second embodiments, as well as using the same image reading apparatus as shown in FIGS. A device may be provided exclusively for detecting the residual radiation energy level, and detection may be performed from the stimulable phosphor sheet 13 after image reading. Furthermore, when the above-mentioned "pre-reading" is performed, the residual radiation energy level can also be determined from the read image signal during this "pre-reading".

(Effects of the Invention) As explained in detail above, according to the afterimage erasing device for a stimulable phosphor sheet of the present invention, the erasing light is finely tuned in response to local changes in the residual radiation energy level in one stimulable phosphor sheet. Since the irradiation amount can be changed, the power consumption of the erasing light source can be significantly reduced, and when the relative movement speed between the stimulable phosphor sheet and the erasing light source is controlled, the time required for erasing the afterimage can be significantly shortened.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a radiation image recorded on a stimulable phosphor sheet according to the present invention, Fig. 2 is a schematic diagram showing a first actual ms-like device of the present invention, and Fig. 3 is a schematic diagram showing the above embodiment device. FIG. 4 is a perspective view showing another example of a linear light source that can be used for. FIG. 4 is a schematic diagram showing a second embodiment of the device of the present invention. 10... Laser light source 11... Laser light 12.
... Galvanometer mirror 13 ... Stimulative phosphor sheet 15 ... Concentrator 16 ... Photomultiple 17
. . . Image information reading circuit 20 . . . Sheet moving means 21 . . . Linear light source 22 .
...Variable speed motor 23...Motor control circuit 32.
... Linear light source 40 ... Light source control circuit 41 ...
・Light source drive circuit

Claims (1)

[Claims] In a stimulable phosphor sheet afterimage erasing device that erases afterimages caused by residual radiation energy by irradiating light onto a stimulable phosphor sheet that can repeatedly record and read radiation image information after reading radiation image information, energy distribution amount detection means for detecting the distribution amount of the residual radiation energy amount changing and distributed in the predetermined direction; a linear light source that irradiates light for erasing; a moving means that relatively moves the linear light source and the sheet in the predetermined direction to irradiate the light over the entire length of the sheet; and the amount of energy distribution. In response to the output of the detection means, at least one of the linear light source and the moving means is controlled to increase or decrease the amount of light irradiated to each part of the sheet according to the magnitude of the residual radiation energy distribution in each part of the sheet in a predetermined direction. An afterimage erasing device for a stimulable phosphor sheet, comprising a control means for erasing an afterimage of a stimulable phosphor sheet.