JPH041630A - Device for erasing stimulable phosphor sheet and radiograph reader - Google Patents

Abstract

PURPOSE:To eliminate the waste of electric power for erasure and to increase the processing speed of this device by providing an erasure light quantity control means and adjusting the quantity of erasure light according to the kind of the stimulable phosphor sheet. CONSTITUTION:A bar code reader 52 reads the information of the bar code 51 of the stimulable phosphor sheet 14 and the kind of the stimulable phosphor sheet 14 is descriminated. A signal processing part 40 inputs a signal SA indicating a breeder voltage, and finds maximum dosage from dosage-to-breeder voltage relation and the quantity of erasing light from the maximum dosage. The signal processing part 40 sends a control signal SC to a power source 36 for an erasing light source 35, which emits the erasing light corresponding to the quantity of erasing light. Consequently, the quantity of the irradiating erasing light is controlled according to the kind of the stimulable phosphor sheet which have different erasing characteristics, so unnecessary power consumption is precluded and the processing speed per unit time is increased.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides an erasing device for erasing radiation energy remaining in a stimulable phosphor sheet after reading has been completed, and a stimulable The present invention relates to a radiation image reading device that obtains an image signal by reading stimulated luminescence light emitted from a phosphor sheet.

(Conventional technology) Radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.)
When irradiated with , some of this radiation energy is accumulated,
A stimulable phosphor (stimulable phosphor) is known that exhibits stimulated luminescence depending on the accumulated energy when it is then irradiated with excitation light such as visible light.

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded once on a sheet of stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam to be stimulable. Generate luminescent light, photoelectrically read the obtained stimulated luminescent light to obtain image data, and based on this image data, a radiation image of the subject is recorded on a recording material such as a photographic light-sensitive material, or on a CRT.
The present applicant has proposed a radiation image recording and reproducing system that outputs a visible image to
No. 429, No. 5G-11395, No. 55-16347
No. 2, No. 5G-104645, No. 55-110340
No. etc.).

This system has the practical advantage of being able to record images over a much wider range of radiation exposures than conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiographic image into an electrical signal and using this electrical signal to output the radiographic image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiographic image that is not affected by fluctuations in the amount of radiation exposure can be produced. Obtainable.

In the system using the above-mentioned stimulable phosphor sheet, radiation energy usually still remains in the stimulable phosphor sheet used on one side (herein referred to as "afterimage"), and the stimulable phosphor sheet The stimulable phosphor sheet is irradiated with erasing light, thereby emitting the remaining radiation energy (erasing the afterimage) and regenerating the stimulable phosphor sheet into a reusable state.

(Problems to be Solved by the Invention) In the above system, a system using a plurality of types of stimulable phosphor sheets having mutually different erasing properties can be considered. Here, the erasing characteristic is indicated by the amount of erasing light required to erase the afterimage when radiation with a predetermined energy is irradiated and reading is performed under the predetermined conditions. This refers to the difference in the amount of erasing light required to erase the afterimage even though the images were irradiated with radiation and reading was performed under the same conditions.

In this case, the amount of erasing light ((amount of light per unit time emitted from the erasing light source) x (irradiating the erasing light to the stimulable phosphor sheet) is adjusted according to the stimulable phosphor sheet that requires the maximum amount of erasing light. It is conceivable to set the afterimage (time)), but depending on the type of stimulable phosphor sheet, the afterimage can be completely erased with a lower amount of light, and in this case, there is a waste of power to turn on the light source. Otherwise, the cycle time when repeatedly using the stimulable phosphor sheet becomes longer.

In view of the above circumstances, it is an object of the present invention to eliminate waste of power for erasing multiple types of stimulable phosphor sheets and to shorten cycle time.

(Means for Solving the Problems) A stimulable phosphor sheet erasing device of the present invention is a stimulable phosphor sheet erasing device that erases a radiation image remaining on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet with erasing light. In the phosphor sheet erasing device, an identification means for identifying types of the stimulable phosphor sheets having mutually different erasing characteristics, and irradiation per unit area of the stimulable phosphor sheet based on the output of the identification means. The present invention is characterized by comprising an erasing light amount control means for controlling the amount of the erasing light.

The radiation image reading device of the present invention also includes a scanning means for two-dimensionally scanning a stimulable phosphor sheet on which a radiation image is stored and recorded, and a scanning means for two-dimensionally scanning a stimulable phosphor sheet with an excitation light beam; a reading means for photoelectrically reading the stimulated luminescence light and outputting an image signal carrying the 144-ray image; A radiation image reading device comprising an erasing means for erasing a radiation image remaining on a phosphor sheet, an identification means for identifying types of the stimulable phosphor sheets having mutually different erasing properties, and an identification means for identifying types of the stimulable phosphor sheets having mutually different erasing characteristics; detection means for detecting the level of radiation energy accumulated in the stimulable phosphor sheet during reading; The present invention is characterized by comprising an erasing light amount control means for controlling the amount of the emitted erasing light.

(Function) Since the stimulable phosphor sheet erasing device and radiation image reading device of the present invention are equipped with the erasing light amount control means as described above, the amount of erasing light is adjusted according to the type of stimulable phosphor sheet. Therefore, it is possible to eliminate wasted power for erasing or to improve the processing speed of this device.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a perspective view showing an X-ray image reading device which is an embodiment of the present invention.

XI;I imaging is performed by an X-ray imaging device (not shown), and thereby an X49 image is accumulated and recorded on the storage phosphor sheet. Thereafter, the stimulable phosphor sheet 14 on which the X-ray image has been stored and recorded is moved in the direction of arrow Z shown in the figure and set at a predetermined position in the reading section 20. This reading section 20 includes a barcode 51 attached to the stimulable phosphor sheet 14.
A barcode reader 52 is provided to read the information on the barcode 51 before setting the stimulable phosphor sheet 14 to a predetermined position in the reading section 20, thereby identifying the type of stimulable phosphor sheet 14. is determined. The phosphor sheet I4 set in this predetermined position is
The sheet is transported (sub-scanning) in the direction of arrow Y by a sheet transporting means 22 (not shown). On the other hand, the excitation light beam 24 emitted from the laser light source 23 is reflected and deflected by the rotating polygon M2B that is driven by the motor 25 and rotates at high speed in the direction of the arrow, and after passing through the focusing lens 27 such as an fθ lens, the optical path is changed by the mirror 28. The light then enters the stimulable phosphor sheet 14 and is main-scanned in the direction of arrow X, which is substantially perpendicular to the sub-scanning direction (direction of arrow Y). From the part of the stimulable phosphor sheet 14 irradiated with the excitation light beam 24, the accumulated and recorded X
Stimulated luminescence light 29 is emitted in an amount corresponding to the line image information,
This stimulated luminescent light 29 is passed through the light guide 30 to the exit end surface 3.
guided towards 0b. The light guide 30 is made by molding a light guide material such as an acrylic plate, and its entrance end surface 30a is formed in a straight line so as to extend along the main scanning line on the stimulable phosphor sheet J4. The injection end surface 30b is formed in an annular shape. Injection end surface 30
The light receiving surface of a photomultiplier 32 is coupled to the photomultiplier 32 through an optical filter 31 that transmits the stimulated luminescence light 29 and blocks the excitation light 24.

The stimulated luminescence light 29 that has entered the light guide 30 from the input end surface 30a travels inside the light guide 30 by undergoing total internal reflection, exits from the exit end surface 30b, passes through the optical filter 31, and enters the photomultiplier. The photomultiplier 32 converts the stimulated luminescence light 29, which is received by the photomultiplier 32 and represents an X-ray image, into an electrical signal. Also, when reading this,
The bleeder voltage of the photomultiplier 32 is monitored, and a signal S^ representing this voltage is also input to the signal processing section 40.

The analog output signal S^ outputted from the photomultiplier 32 is logarithmically amplified by the logarithmic amplifier 33, and the A/D
The signal is digitized by a converter 34, and an image signal So is obtained as an electrical signal.

The obtained image signal So is input to the signal processing section 40. This signal processing section 40 includes a main body section 41. A drive section 42 into which a floppy disk as auxiliary memory is inserted and driven. It is comprised of a keyboard 43.degree. for an operator to input instructions necessary for the X-ray image reading device, and a CRT display 44 for displaying visible images and necessary information based on the image signal SD.

The image signal So input to the signal processing unit 40 is subjected to, for example, data compression processing as necessary, and sent to an image filing device (not shown) that stores radiation images in the form of image signals. Alternatively, the image signal SD is subjected to image processing such as frequency emphasis processing, smoothing processing, contrast conversion processing, etc., and is reproduced and displayed on the CRT display 44 as a visible image.

On the downstream side of the transport of the stimulable phosphor sheet [4], an erasing light source 35 is provided for erasing LMX-ray energy (afterimage) that cannot be emitted even by irradiation with the excitation light beam 24. A power source 36 is connected to the erasing light source 35, which changes the lighting voltage of the erasing light source (the amount of emitted light of the erasing light) according to a command from the signal processing section 40.

Control of this lighting voltage is performed as follows.

Figure 1A shows the bleeder voltage of the photomultiplier,
Figure 1B is a diagram showing the relationship between the dose of X-rays irradiated to the stimulable phosphor sheet during X-ray photography and the relationship between the dose of X-rays irradiated to the stimulable phosphor sheet during X-ray photography and the relationship between FIG. 7 is a diagram showing the relationship between the amount of erasing light required to erase an afterimage after reading under certain conditions;

The relationship between the dose and the bleeder voltage and the relationship between the dose and the amount of erasing light are determined in advance for each of the plurality of types A and B of stimulable phosphor sheets, and are stored in the signal processing section 4.

The greater the amount of X-rays irradiated to the stimulable phosphor sheet during imaging, the greater the amount of stimulated luminescence light that is emitted and enters the photomultiplier 32, resulting in a further decrease in the bleeder voltage. .

Therefore, by monitoring the bleeder voltage during reading, the irradiation dose (xl accumulated on the stimulable phosphor sheet)
energy) can be detected (Japanese Patent Laid-Open No. 1983
(Refer to Publication No.-260035). Here, even if the type A stimulable phosphor sheet and the type B stimulable phosphor sheet are irradiated with the same dose of X41 and irradiated with the same amount of excitation light beam 24, the stimulable phosphor sheet The amounts of stimulated luminescence light emitted from the sheets are different, and therefore the bleeder voltages are different for the same dose X, as shown in FIG. 1A.

Here, it is assumed that the bleeder voltage drops to the maximum V^ while reading the type A stimulable phosphor sheet.

At this time, since the type of stimulable phosphor sheet is already known from the information of the barcode 51, the signal processing section 40 inputs the signal sA representing the bleeder voltage, thereby generating the already stored FIG. 1A. The maximum line tlXl is determined by referring to the relationship between the dose and the bleeder voltage as shown in FIG.

Next, the relationship between the dose and the amount of erasing light as shown in FIG. 1B is considered, and the amount of erasing light LA is determined from the maximum dose X1. The signal processing unit 40 issues a control signal Sc to the erasing light source power supply 36, and the erasing light source emits erasing light corresponding to the erasing light mLA.

The same is true for type B stimulable phosphor sheets, and when the bleeder voltage drops to vB during reading, the X-ray irradiation dose reaches its maximum! 91 fn

Although the explanation has been made here assuming that the transport speed of the stimulable phosphor sheet 14 is constant and the amount of erasing light emitted from the erasing light source 35 changes, the transport speed of the stimulable phosphor sheet 14 may be changed. Of course.

Furthermore, instead of erasing the stimulable phosphor sheet while it is being conveyed, erasing light is simultaneously irradiated onto the entire surface of the stimulable phosphor sheet after reading is completed, and the amount of light or irradiation time of this erasing light is controlled. Good too.

Furthermore, in the above embodiment, the amount of erasing light is controlled in accordance with the accumulated X-ray energy by considering the accumulated X-ray energy for each of the different types of stimulable phosphor sheets. Depending on the type of stimulable phosphor sheet, the amount of erasing light that can normally be used for sufficient erasing is determined empirically and experimentally, and only the type of stimulable phosphor sheet is used without considering the X-ray energy accumulated in the stimulable phosphor sheet. The amount of erasing light may be controlled depending on the amount of light.

In this case, the erasing device may be provided independently of the radiation image reading device.

Further, in each of the above embodiments, the type of stimulable phosphor sheet was determined based on the information on the barcode 51, but the barcode is only an example.
The type of stimulable phosphor sheet may be input from 3, or the type of stimulable phosphor sheet may be determined by any other means.

(Effects of the Invention) As described above in detail, the stimulable phosphor sheet erasing device and radiation image reading device of the present invention can erase stimulable phosphor sheets according to the types of stimulable phosphor sheets that have different erasing characteristics. Since the erasing light amount control means is provided to control the amount of erasing light irradiated per unit area of the body sheet, wasteful power consumption is prevented and processing speed per unit time is improved.

[Brief explanation of the drawing]

Figure 1A shows the bleeder voltage of the photomultiplier,
Figure 1B is a diagram showing the relationship between the dose of X-rays irradiated to the stimulable phosphor sheet during X-ray photography and the relationship between the dose of X-rays irradiated to the stimulable phosphor sheet during X-ray photography and the predetermined conditions. FIG. 2 is a perspective view showing an X-ray image reading device according to an embodiment of the present invention. 14...Stormable phosphor sheet 20...Reading section 24.
...Excitation light 2B...Rotating polygon mirror 30.
...Light guide 31...Optical filter 32
...Photomultiplier 40...Signal processing section Fig. 1A I Tosara (mR)

Claims (2)

[Claims] (1) In a stimulable phosphor sheet erasing device that erases a radiation image remaining on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet with erasing light, the stimulable phosphor sheets have mutually different erasing characteristics. and an erasing light amount control means for controlling the amount of the erasing light irradiated per unit area of the stimulable phosphor sheet based on the output of the identifying means. A device for erasing stimulable phosphor sheets. (2) a scanning means for two-dimensionally scanning a stimulable phosphor sheet on which a radiation image has been stored and recorded; a reading means for outputting an image signal carrying the radiation image; and a reading means for outputting an image signal carrying the radiation image, and a radiation image remaining on the stimulable phosphor sheet by irradiating erasing light onto a portion of the stimulable phosphor sheet where reading has been completed. A radiation image reading device comprising an erasing means for erasing, an identification means for identifying the types of the stimulable phosphor sheets having mutually different erasing characteristics, and an identification means for identifying the types of the stimulable phosphor sheets that have different erasing characteristics; a detection means for detecting the level of radiation energy accumulated in the sheet; and controlling the amount of the erasing light irradiated per unit area of the stimulable phosphor sheet based on the output of the identification means and the output of the detection means. What is claimed is: 1. A radiation image reading device comprising: erasing light amount control means.