JPH03279934A - Radiation image reader - Google Patents

Abstract

PURPOSE:To keep the effect of the adhesion of dust to the minimum by detecting the presence or absence of the dust adhering to a stimulable phosphor sheet and giving an alarm in the case of detecting the specified number or more dust. CONSTITUTION:This reader is provided with a dust detection means 40 for detecting the presence or absence of the dust adhering to the stimulable phosphor sheet 14 and an alarm means which gives the alarm in the case that the specified number or more dust is detected by the means 40. At the time of reading, the specks of dust adhering to all the surface of the sheet 14 are counted based on a monitoring signal SM. When the number of specks attains or exceeds the specified number, a buzzer sounds so as to demand an operator to perform the cleaning of the sheet 14. Thus, the sheet 14 is cleaned and used again in a state where the dust does not adhere to the sheet 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a radiation image reading device that obtains an image signal by reading a radiation image stored and recorded on a stimulable phosphor sheet. The present invention relates to a radiation image reading device having a function of detecting dust attached to a body 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. 5B-11395, No. 55-16347
No. 2, No. 5B-104645, No. 55-116340
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 radiation image into an electric signal and using this electric signal to output the radiation 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 radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. be able to.

(Problems to be Solved by the Invention) In a system using the above-mentioned stimulable phosphor sheet, if dust adheres to the surface of the stimulable phosphor sheet, not only will image information in that area be lost, but the dust You can clearly distinguish between shadows and necessary information on radiographic images.
This may lead to errors in judgment when observing images.

For example, an X-ray image of a human breast is stored and recorded on the stimulable phosphor sheet, an electrical signal representing the X-ray image is obtained, and based on the electrical signal, the X-ray image is displayed as a visible image on a CRT display device or the like. One of the criteria for reproducing and outputting images to diagnose whether or not it is breast cancer is the presence, number, density, etc. of calcification, which appears as white spots with an average diameter of about 300 μm on the X-ray image. However, if dust is attached to the stimulable phosphor sheet,
The dust shadows often appear as white spots on the reproduced visible image and are difficult to distinguish from the above-mentioned calcification, so even though calcification does not actually exist, there is a possibility of breast cancer. There is a possibility of misdiagnosis.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a radiation image reading device that can suppress the influence of dust adhering to a stimulable phosphor sheet.

(Means for Solving the Problems) A first radiation image reading device of the present invention irradiates excitation light onto a stimulable phosphor sheet on which a radiation image is accumulated and recorded, thereby emitting excitation light from the stimulable phosphor sheet. A radiation image reading device that obtains an image signal by photoelectrically reading the stimulated luminescence light carrying the radiation image, comprising: a dust detection means for detecting the presence or absence of dust attached to the stimulable phosphor sheet; The present invention is characterized by comprising an alarm means that issues an alarm when a predetermined number or more of the dust is detected by the means.

Further, the second radiation image reading device of the present invention reads the radiation image emitted from the stimulable phosphor sheet by irradiating the excitation light onto the stimulable phosphor sheet on which the radiation image is accumulated and recorded. In a radiation image reading device that photoelectrically reads carried stimulated luminescence light to obtain an image signal, a dust detection means detects the presence or absence of dust attached to the stimulable phosphor sheet and its position on the stimulable phosphor sheet. ,
The present invention is characterized by further comprising dust position display means for displaying the position of the dust on the stimulable phosphor sheet when the dust detection means detects a predetermined number or more of the dust.

Here, the dust detection means is not limited to a specific method as long as it can detect dust attached to the stimulable phosphor sheet, but for example, a method shown in the embodiment described later is used.

Further, the "predetermined number" is not limited to a specific number, and one or more arbitrary numbers can be selected.

Furthermore, the alarm in the first radiation image reading device is not limited to an alarm that emits a sound,
For example, the lighting of a lamp may be displayed on a display screen.

(Function) The stimulable phosphor sheet can be used repeatedly for recording and reading radiation images.

Here, the operator is cleaning the surface of the stimulable phosphor sheet to remove dust.
Since cleaning the stimulable phosphor sheet each time it is used is very time-consuming, an operator usually cleans the stimulable phosphor sheet periodically, for example, every morning.

The present invention has been made in view of the above facts, and the first radiation image reading device of the present invention detects dust attached to a stimulable phosphor sheet and issues an alarm when the dust exceeds a predetermined number. This allows the operator to know that more than a predetermined amount of dust has adhered after cleaning during normal work, and to perform cleaning again.
This allows the influence of dust to be minimized.

In addition, the second radiation image reading device of the present invention is equipped with a dust position display means that displays the position of dust on the stimulable phosphor sheet when a predetermined number of dust or more is detected. It is possible to know the position where dust has adhered on the body sheet, and in addition to the effects of the first radiation image reading device, it is also possible to improve the efficiency of cleaning work.

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

FIG. 1 is a schematic diagram of an example of an X-ray imaging apparatus.

X-rays 12 are emitted from the X-ray source 11 of the X-ray imaging device 10 toward the breast 13a of the human body 13, and the X-rays 12a that have passed through the human body 13 are irradiated onto the stimulable phosphor sheet 14. A transmitted X-ray image of the breast 13a is accumulated and recorded on the stimulable phosphor sheet 14.

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

The stimulable phosphor sheet 14 on which the X-ray image has been recorded is set at a predetermined position in the reading section 20. The stimulable phosphor sheet 14 set at a predetermined position is conveyed (sub-scanned) in the direction of arrow Y by a sheet conveying means 22 such as an endless belt driven by a motor 21. On the other hand, a light beam 24 emitted from a laser light source 23 is reflected and deflected by a rotating polygon mirror 26 that is driven by a motor 25 and rotates at high speed in the direction of the arrow, passes through a converging lens 27 such as an fθ lens, and then changes its optical path by a mirror 28. Instead, it enters the sheet 14 and performs main scanning in the direction of arrow X, which is substantially perpendicular to the direction of sub-scanning (direction of arrow Y). From the part of the stimulable phosphor sheet 14 irradiated with the excitation light 24, the accumulated and recorded X
Stimulated luminescence light 29 of a light amount corresponding to the line image information is emitted,
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 14. 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 luminescent light 29 that has entered the light guide 30 from the incident end surface 30a travels through the interior of the light guide 30 through repeated total reflection, and reaches the exit end surface 3.
The stimulated luminescence light 29 that is emitted from 0b is received by the photomultiplier 32 via the optical filter 31, and is converted into an electrical signal by the photomultiplier 32, which represents an X-ray image.

The analog output signal SA output from the photomultiplier 32 is logarithmically amplified by the logarithmic amplifier 33, and the A/D
The signal is digitized by a converter 34 to obtain an image signal SD 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. A keyboard 43 for the operator to input necessary instructions to the signal processing section 40. and a CRT display 44 for displaying visible images and necessary information based on the image signal s□.

The image signal SD 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 radiographic images in the form of image signals. Alternatively, the image signal So is subjected to image processing such as frequency enhancement processing, smoothing processing, contrast conversion processing, etc., and is reproduced and displayed on the CRT display 44 as a visible image.

FIG. 3 is a diagram showing an example of an X-ray image of a breast reproduced and displayed on a CRT display.

In the shadow 13a' of the breast, a spot 15, which has an average diameter of about 300 μm and is whitish compared to the surrounding area, appears. This is mainly due to calcification in the breast, and the number, density, etc. of this are the basis for diagnosis of breast cancer. However, there is a possibility that these spots are caused by dust adhering to the stimulable phosphor sheet 14, and therefore, if a large amount of dust adheres, it becomes impossible to perform a reliable diagnosis. Therefore, in order to detect this dust,
The line image reading device has a light guide 35 in its reading section 20. A second photoelectric conversion means including a photomultiplier 37 and the like is provided.

During the above reading, part of the excitation light that irradiates the stimulable phosphor sheet 14 is reflected from the sheet, and the incident end surface 35
an optical filter 3 that enters the light guide 35 from a, travels through the light guide 35 and exits from its exit end face 35b, transmits the excitation light 24 and blocks the stimulated luminescence light 29;
The light is input to the photomultiplier 37 via B.

The analog signal S^' output from the photomultiplier 37 is logarithmically amplified by the logarithmic amplifier 38, and A
/D converter 39 digitizes the monitor signal s
It is input to the image processing section 40 as M. Image processing section 40
The presence or absence of dust attached to the stimulable phosphor sheet 14 and its position are detected in the following manner.

FIG. 4 is a diagram showing the monitor signal sM along the main scanning direction (X direction shown in FIG. 2).

The stimulable phosphor sheet 14 is irradiated with a constant amount of excitation light 24 that does not change over time, and therefore the amount of excitation light 24 that is reflected from the stimulable phosphor sheet 14 and enters the light guide 35 is also generally constant ( Ave).

If dust adheres to the surface of the stimulable phosphor sheet 14, the excitation light 24 that irradiates the stimulable phosphor sheet 14 will be scattered or absorbed by the dust, and the amount of excitation light 24 that enters the light guide 35 will decrease. Therefore, the value of the monitor signal sM decreases as shown by symbol A in FIG. Therefore, the area in which the area is lower than the predetermined threshold value AveKl is determined for each main scan.

FIG. 5 shows the X accumulated and recorded on the stimulable phosphor sheet 14.
FIG. 2 is a diagram schematically showing each pixel of a part of a line image.

As described above, it is determined for each main scan whether the monitor signal sM is greater than or equal to the threshold value Ave-, and if SM<Ave-
It is determined that the area consisting of each pixel of -Kt (the area indicated by diagonal lines in the figure) is the part to which dust has adhered.

In this way, during the above reading, the number of dust particles adhering to the entire surface of the stimulable phosphor sheet 14 is counted based on the monitor signal sM, and when this number reaches a predetermined number or more, a buzzer (not shown) sounds and the operator is instructed to The user is prompted to clean the stimulable phosphor sheet 14. As a result, the stimulable phosphor sheet 14 is cleaned and reused free of dust.

Incidentally, in the above embodiment, the number of dust particles was counted, but a buzzer may be sounded immediately if there is even one piece of dust attached.

Further, in the above embodiment, the buzzer sounds, but instead of or in addition to this, the CRT display 44 (second
(See figure) A schematic diagram of the stimulable phosphor sheet and the position of dust on the sheet 14 may be displayed. With this configuration, the operator can know not only the presence or absence of dust but also the position on the stimulable phosphor sheet 14, thereby making the cleaning work more efficient.

FIG. 6 shows another method for determining the dust-attached area on the stimulable phosphor sheet in the main scanning direction (X direction).
FIG. 3 is a diagram showing a differential value SM' of the monitor signal sM along the curve.

When differentiated along the X direction in the figure, a downward peak a1 occurs at the front end of portion A corresponding to dust, and an upward peak a2 occurs at the rear end. Therefore, these peaks ai+a2 are compared with the threshold value ±2, and the front and rear ends of the area corresponding to dust are determined.

Similar to FIG. 5, FIG. 7 is a diagram schematically representing each pixel of a part of the X-ray image accumulated and recorded on the stimulable phosphor sheet.

The front end for each main scan using the detection direction described above.

When the rear end is determined, the pixels corresponding to the front end and the rear end are, for example, the hatched pixels in FIG. 7. Therefore, it is determined that the area surrounded by each pixel corresponding to the front end and the rear end is the part to which dust has adhered.

FIG. 8 is a perspective view showing an X-ray image reading device as another embodiment of the radiation image reading device of the present invention. Second
Elements that are the same as those in the X-ray image reading device shown in the figure are given the same numbers as in FIG. 2, and their explanations will be omitted.

This X-ray image reading device is equipped with a light guide 51 that is split into two parts in the middle, and the excitation light 24 scattered on the surface of the stimulable phosphor sheet 14 is also incident along with the stimulated luminescence light from the entrance end face 51a. do. Further, a reflecting mirror 52 is arranged at a position facing the incident end face 51a across the main scanning line, and reflects the stimulated luminescence light 29 emitted toward the reflecting mirror 52 side and the excitation light 24 scattered toward the reflecting mirror 52 side. It is reflected toward the incident end surface 5La.

Stimulated luminescence light 29 and scattered excitation light 2 that entered the light guide 51
4 travels through the light guide 51, splits into two, and exits from the first exit end surface 51b and the second exit end surface 51c. The first exit end surface 51b is coupled to a photomultiplier 32 through an optical filter 31 that transmits the stimulated luminescence light 29 and blocks the excitation light 24. Therefore, the photomultiplier 32 causes the stimulated luminescence light 29
only that is photoelectrically converted. Further, the second injection end surface 51c is
The excitation light 24 passes through an optical filter 36 that blocks the stimulated luminescence light 29, and then passes through a photomultiplier 37.
and therefore the photomultiplier 3
7, only the scattered excitation light is photoelectrically converted. The analog signal output from the photomultiplier 37 is logarithmically amplified by a logarithmic amplifier 38, and further amplified by an A/D converter 39.
A/D conversion is performed at , thereby generating a monitor signal SM'. This monitor signal SM' is a signal that carries the amount of scattered excitation light, so normally its value is almost constant, but if dust adheres to the surface of the stimulable phosphor unit 14, the excitation light It is scattered or absorbed by dust, and therefore the presence of dust lowers the value of the monitor signal SM'.

The signal processing section 40 detects the presence or absence of dust attached to the stimulable phosphor sheet 14 and its position based on the monitor signal SM'.

Incidentally, although each of the above embodiments has described an X-ray image of a human breast, the subject is not limited to a human breast.
Furthermore, the present invention is not limited to X-ray images, but can also be applied to, for example, an electron microscope system that stores and records images by electron beams on a stimulable phosphor sheet.

(Effects of the Invention) As described above in detail, the first radiation image reading device of the present invention includes a dust detection means for detecting the presence or absence of dust attached to a stimulable phosphor sheet, and a dust detection means for detecting dust. Equipped with an alarm means that issues an alarm when more than a predetermined amount of dust is detected, this alarm lets you know that a predetermined number of dust has adhered to the stimulable phosphor sheet, minimizing the effects of dust adhesion. It can be held down.

Further, the second radiation image reading device of the present invention includes a dust detection means for detecting the presence or absence of dust attached to a stimulable phosphor sheet and its position on the stimulable phosphor sheet, and a dust detection means for detecting a predetermined number of dust particles. Since it is equipped with a dust position display means that displays the position of the dust on the stimulable phosphor sheet when the dust is detected, in addition to the same effect as the first radiation image reading device, It is also possible to know where the dust has adhered, and to improve the efficiency of cleaning work.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of an X-ray imaging device, FIG. 2 is a perspective view of an X-ray image reading device that is an embodiment of the radiation image reading device of the present invention, and FIG. 3 is a CRT FIG. 4 is a diagram showing an example of a breast X-ray image reproduced and displayed on the display, and FIG. 5 is a diagram showing the monitor signal and sM along the main scanning direction (X direction shown in FIG. The figure schematically shows each pixel of a part of the X-ray image accumulated and recorded on the stimulable phosphor sheet 14, and FIG. 6 shows the area on the stimulable phosphor sheet to which dust has adhered. In order to show another method, FIG. 7 shows the differential value SM' of the monitor signal sM along the main scanning direction (X direction). FIG. 8 is a diagram schematically representing each pixel of a part of a recorded X-ray image, and FIG. 8 is a perspective view showing an X-ray image reading device as another embodiment of the radiation image reading device of the present invention. be. IO... X-ray imaging device 14... stimulable phosphor sheet 20... reading section 24...
...excitation light 26...rotating polygon mirror 30,
35.51... Light guides 31, 38... Optical filters 32, 37... Photo multiplier 40... Signal processing section - 11, 11

Claims (2)

[Claims] (1) By irradiating a stimulable phosphor sheet on which a radiation image has been stored and recorded with excitation light, the stimulated luminescence light carrying the radiation image emitted from the stimulable phosphor sheet is read photoelectrically to form an image. In a radiation image reading device for obtaining a signal, a dust detection means detects the presence or absence of dust attached to the stimulable phosphor sheet, and an alarm means generates an alarm when a predetermined number or more of the dust is detected by the dust detection means. A radiation image reading device comprising: (2) By irradiating excitation light onto a stimulable phosphor sheet on which a radiation image has been stored and recorded, the stimulated luminescent light carrying the radiation image emitted from the stimulable phosphor sheet is photoelectrically read to form an image. In a radiation image reading device for obtaining a signal, a dust detection means detects the presence or absence of dust attached to the stimulable phosphor sheet and the position on the stimulable phosphor sheet;
and a radiation image reading device comprising a dust position display means for displaying the position of the dust on the stimulable phosphor sheet when a predetermined number or more of the dust is detected by the dust detection means.