JPH06175243A - Radiograph reader - Google Patents

Abstract

PURPOSE:To enable residual radioactive energy after radiograph information accumulated and recorded on a stimulable phosphor is read to be efficiently erased by controlling the irradiating quantity of erasing light according to a reading dynamic range. CONSTITUTION:Halogen lamps 27a-27c and a motor driving circuit 25 are controlled by a CPU 28 controlling the action of a recording and reading device 3. Besides, the set information of the reading dynamic range is given to the CPU 28 from a controller 29 controlling a whole system by communication. By the CPU 28, the turning-on frequency of the lamps 27a-27c and the carrying speed (erasing speed) thereof in a sub-scanning direction at an erasing time are set based on the information of the reading dynamic range from the controller 29. According to this set, the turning-on of the respective lamps 27a-27c is individually controlled and the rotation of a sub-scanning motor is controlled through the driving circuit 25. By such a way, an after image erasing means is constituted of the CPU 28 and the halogen lamps 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image reading apparatus, and more particularly to a technique for efficiently erasing an afterimage after reading a radiation image.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are often used for diagnosing diseases, etc. In order to obtain this X-ray image, X-rays transmitted through a subject are displayed on a fluorescent screen (phosphor layer). Irradiation is performed to generate visible light according to the transmitted dose, and this visible light is applied to a film using a silver salt as in ordinary photography to develop the film. ing.

However, in recent years, a method for directly reading image information from a phosphor layer has been devised without using a film coated with silver salt. As such a method, the radiation transmitted through the subject is absorbed by the stimulable phosphor, and then the stimulable phosphor is excited by, for example, light or thermal energy to absorb the stimulable phosphor. There is a method in which the accumulated radiation energy (radiation image information) is stimulated to emit fluorescence as fluorescence, and the stimulated emission is photoelectrically converted to obtain an image signal.

Specifically, for example, US Pat. No. 3,859,527 and JP-A-55-12144 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light. ing. This method uses a radiation image conversion panel having a stimulable phosphor layer formed on a support.
The radiation that has passed through the subject is applied to the photostimulable phosphor layer of this radiation image conversion panel, and the radiation energy corresponding to the radiation transmittance of each part of the subject is accumulated to form a latent image. By scanning the body layer with stimulated excitation light, the radiation energy accumulated in the stimulable phosphor layer is converted into light and emitted, and the stimulated emission is photoelectrically converted to obtain a radiation image signal. Is.

[0005]

By the way, when the excitation light having a sufficient intensity is irradiated at the time of reading by scanning the excitation light, the accumulated radiation energy should disappear, but in reality, the reading is performed. Complete erasure cannot be performed only with the excitation light that is sometimes irradiated. Therefore, conventionally, before the radiation image information is recorded (after the reading is completed), the radiation image conversion panel is scanned with the erasing light to sufficiently release the remaining radiation energy so that the afterimage is erased. (JP-A-56-11
(See Japanese Patent No. 392).

In the afterimage erasing, if the irradiation amount of the erasing light (light amount of the erasing light source × time) is set as large as possible, complete afterimage erasing can be achieved, but in this case, unnecessary irradiation is performed, There are problems such as increased energy consumption, redundant erase time, and reduced life of the erase light source. Therefore, in order to suppress the irradiation amount of the erasing light, it is possible to detect the residual radiation energy amount and control the light amount of the erasing light and the erasing scanning speed according to the residual energy amount.
It is proposed in Japanese Patent Publication No. 206361.

However, in such an erasure control system, although the residual radiation energy amount is detected, it is a condition that the residual radiation energy should be completely released, or the presence of residual radiation energy to some extent is allowed. Since it is not distinguished whether it is a condition or not, an excessive erase operation is to be performed when the presence of a small amount of residual radiation energy is allowed.

That is, in the radiation image reading apparatus as described above, the reading dynamic range may be changed as necessary. Here, when reading with a low dynamic range, a slight residual radiation energy is allowed, so the minimum required amount of erasing light irradiation is lower than when reading with a high dynamic range.

However, in the conventional erasing control based on the detection result of the residual radiation energy amount, the erasing light irradiation amount is determined irrespective of the reading dynamic range. It is necessary to set the irradiation amount of the erasing light high enough to release the residual energy. Therefore, when the read dynamic range is low, although complete emission of residual energy is not required, complete emission is performed with an excessive irradiation amount of erasing light.

The present invention has been made in view of the above problems, and in the erasing control for erasing residual image energy by erasing residual radiation energy, it is possible to perform a minimum residual image erasure that does not affect reading. The purpose is to suppress the irradiation amount of erasing light.

[0011]

Therefore, the radiation image reading apparatus according to the present invention is constructed as shown in FIG. In FIG. 1, a radiation image conversion panel is for accumulating and recording radiation image information by absorbing radiation from a radiation source that has passed through a subject into a stimulable phosphor, and a reading means is used for this radiation image conversion. By scanning the panel with excitation light, the radiation image information stored and recorded in the stimulable phosphor is stimulated to emit light, and the stimulated emission is photoelectrically read to obtain radiation image information.

The read dynamic range control means variably sets the dynamic range of the read means. Further, the afterimage erasing unit scans the radiation image conversion panel with the erasing light after the reading by the reading unit to erase the afterimage due to the residual radiation energy. Then, the erasing control means controls at least one of the amount of erasing light and the scanning speed of the erasing light in the afterimage erasing means according to the reading dynamic range controlled by the reading dynamic range control means.

[0013]

According to this structure, in the radiation image reading device in which the dynamic range when the radiation image conversion panel is scanned with the excitation light to read the radiation image information is variably set, the panel is scanned with the erasing light after reading. When erasing the afterimage, at least one of the erasing light amount and the scanning speed in the erasing light scanning is controlled according to the reading dynamic range.

That is, the allowable residual radiation energy amount varies depending on the read dynamic range, and it is useless to irradiate the erasing light so as to emit up to the allowable residual radiation energy. By controlling the light irradiation amount, it is possible to control the irradiation amount to the minimum level at which the residual radiation energy can be emitted to a level that does not affect reading.

[0015]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a block diagram showing a basic hardware configuration of an embodiment of a radiographic image reading apparatus according to the present invention, and in the present embodiment, it is applied to chest radiography of a human body for medical use.

Here, the radiation source 1 is controlled by the radiation controller 2 and irradiates the subject (human chest or the like) M with radiation (generally X-rays). The recording / reading device 3 is provided with a radiation image conversion panel 4 on a surface facing the radiation source 1 with the subject M interposed therebetween, and the radiation image conversion panel 4 emits radiation of the subject M with respect to the radiation dose from the radiation source 1. Energy according to the transmittance distribution is accumulated in the photostimulable phosphor layer provided therein, and a latent image of the subject M is formed on the photostimulable phosphor layer.

The radiation image conversion panel 4 is provided with a stimulable phosphor layer on a support by vapor deposition of the stimulable phosphor or coating of the stimulable phosphor. The phosphor layer is shielded or covered by a protective member in order to prevent adverse effects and damages caused by the environment. Examples of the material for the stimulable phosphor layer include, for example, JP-A-61-720.
The material disclosed in Japanese Patent Laid-Open No. 91 or Japanese Patent Laid-Open No. 59-75200 is used.

A laser beam generator (gas laser, solid-state laser, semiconductor laser, etc.) 5 generates a laser beam (excitation light) whose emission intensity is controlled, and the laser beam passes through various optical systems to be a scanner. The light beam reaches the (polygon mirror) 6, is deflected there, and is further deflected by the reflection mirror 7 to be guided to the radiation image conversion panel 4 as scanning light for excitation (excitation light).

The condenser 8 is scanned by the laser beam as the excitation light as described above, and the radiation image conversion panel 4 is scanned.
A condensing end made of an optical fiber is located in close proximity to and receives the stimulated emission of the emission intensity proportional to the latent image energy from the radiation image conversion panel 4 scanned by the laser beam. Reference numeral 9 denotes a filter that allows only light in the wavelength region of stimulated emission from the light introduced from the light collector 8 to pass through. The light that has passed through the filter 9 is incident on the photomultiplier 10 and the incident light ( It is photoelectrically converted into a current signal corresponding to (transmission dose).

The output current from the photomultiplier 10 is converted into a voltage signal by the current / voltage converter 11, amplified by the amplifier 12, and then converted into a digital image signal by the A / D converter 13. Therefore, the laser beam generator 5, the scanner 6, the reflecting mirror 7, the condenser 8, the filter 9, and the photomultiplier 10 constitute the reading means in this embodiment. Then, the digital image signal is sequentially output to the image processing circuit 14, where after various image processing such as gradation processing is performed,
The image is stored in the image storage device 15 as it is, or a CRT.
A hard copy can be obtained by being visualized by the display device 16 and further outputted to a printer (not shown).

Reference numeral 17 is a read dynamic range adjusting circuit (read dynamic range control means). By the read dynamic range adjusting circuit 17, the laser beam intensity of the laser beam generator 5 and the power supply voltage of the high voltage power supply 18 for photomultiplier are adjusted. Photomul 10 gain adjustment, current /
Gain / offset adjustment between voltage converter 11 and amplifier 12,
And the input dynamic range of the A / D converter 13 is adjusted, and the read dynamic range of the radiation image signal is adjusted comprehensively.

FIG. 3 is a diagram showing the detailed construction of the reading unit section in the recording and reading apparatus 3. In FIG. 3, the laser beam generator 5 (not shown), the scanner 6, the reflecting mirror 7 (consisting of three reflecting mirrors 7a to 7c), the condenser 8, the filter 9, and the photomultiplier 10. Integrally configure the sub-scanning unit 21, and the sub-scanning unit 21
Moves up and down in the figure while being guided by the guide shaft 23 according to the rotation of the ball screw 22.

The ball screw 22 is rotationally driven by a sub-scanning motor 24, and the sub-scanning motor 24 is controlled by a motor drive circuit 25. The motor drive circuit 25 is provided with various synchronization signals from the scanner (polygon mirror) 6,
Further, an origin position detection signal from the photo sensor 26 for detecting the origin position of the sub-scan is input, and the origin position of the sub-scan (in FIG. 3 is synchronized with the main scanning by the scanner 6). The sub-scanning unit 21 is moved from the upper side) in the sub-scanning direction (downward in FIG. 3) at a predetermined speed.

Further, the sub-scanning unit 21 is provided with a halogen lamp 27 for emitting residual radiation energy in the panel 4 after scanning / reading with a laser beam to erase an afterimage, and a halogen lamp 27 in the sub-scanning direction. It is integrally provided on the front side of the No. 8. The halogen lamp 27 is a linear erasing light source extending in the scanning direction of the scanner 6, that is, the main scanning direction. In the present embodiment, three halogen lamps 27a to 27c are provided in the sub-scanning direction. They are arranged side by side in parallel.

Here, in the present embodiment, in the afterimage erasing, the residual radiation energy is not emitted with a fixed irradiation amount, but the three halogen lamps 27a to 27 are used.
The amount of erasing light (light emission amount × scanning time) is controlled by at least one of controlling the erasing light amount by selectively lighting c and controlling the moving speed (erasing speed) of the sub scanning unit 21 in the sub scanning direction during erasing. ) Can be made variable.

That is, as shown in FIG. 4, the halogen lamps 27a to 27c and the motor drive circuit 25 are controlled by a CPU 28 which controls the operation of the recording / reading device 3, and further, the CPU 28 is controlled by the CPU 28. The read dynamic range setting information is provided by communication from a controller 29 that controls the entire system. Then, the CPU 28 sets the number of halogen lamps 27 to be turned on and the carrying speed (erasing speed) in the sub-scanning direction at the time of erasing based on the information of the read dynamic range from the controller 29, and each is set according to the setting. Halogen lamp 27a-27c
Is individually controlled, and the rotation of the sub-scanning motor 24 is controlled via the motor drive circuit 25. Therefore, in this embodiment, the CPU 28 and the halogen lamp 27 constitute an afterimage erasing means, and the CPU 28 has a function as an erasing control means.

The read dynamic range is arbitrarily set by the operator in response to a photographing request, and the read dynamic range adjustment circuit 17 actually sets the gain / offset in each circuit of the read system according to the setting. Adjust to obtain the set read dynamic range. Here, when the reading dynamic range is set high, the residual radiation energy greatly affects the read image as noise, and thus it is desirable to completely discharge the residual radiation energy, but when the reading dynamic range is set low. The influence of the residual radiation energy is relatively small.

That is, when the read dynamic range is low, even if the residual radiation energy is not completely emitted, it does not adversely affect the next photographing and a slight residual energy is allowed. It is useless to set the same level as when the read dynamic range is set high.

[0029]

[Table 1]

Therefore, in this embodiment, as shown in Table 1, the reading dynamics are preliminarily set so that the minimum irradiation amount of the erasing light can be obtained according to the reading dynamic range within a range that does not adversely affect the next photographing. A table storing the erasing speed (mm / S) and the number of lit halogen lamps 27 is provided for each rank of the range.
The number of halogen lamps turned on during erasing and the erasing speed are determined by referring to the table.

As is clear from Table 1, assuming that the erasing speed is fixed and the shooting / reading cycle is constant, the number of halogen lamps 27 to be turned on can be reduced in accordance with the decrease in the reading dynamic range. , 1/3 the power consumption compared to reading with a high dynamic range
Alternatively, it can be halved. Further, when a certain lamp is no longer lit, if the erasing speed is slowed down instead of using the non-lightable lamp, if at least one lamp can be lit, the time required for erasing becomes long, You will be able to continue normal shooting.

On the contrary, when the number of halogen lamps to be lit is fixed, the erasing speed (conveying speed of the reading unit 21 at the time of erasing) during reading in the low dynamic range.
Can be raised to accelerate the cycle time. In the above embodiment, when the three halogen lamps 27 are turned on, it is preferable that the halogen lamps 27 be turned on one by one at the start of erasing so that the rush current does not flow at all.

Further, as in this embodiment, the halogen lamp 27
In the case where the plural halogen lamps 27 are arranged side by side in the sub-scanning direction, it is not necessary to start the erasing scan from the position where all the halogen lamps 27 are off the panel 4, and as shown in FIG. Halogen lamp 27c located on the panel 4
If the position opposite to is set as the erase scanning start point, the required movement range of the sub-scanning unit 21 can be suppressed to a small size, and the device can be downsized.

Here, at the end of the panel 4 on the side of the sub-scanning starting point, when erasing is performed by three lamps, one or two lamps are used.
Only the erasing light scanning by the book is performed, but in the stopped state, the lamps 27c located on the rear side in the sub-scanning direction are lit one by one, and after all are lit, the conveyance in the sub-scanning direction is performed. By starting the irradiation, the required irradiation amount can be secured depending on the irradiation time in the stopped state. Further, lighting of the lamp may be started during acceleration, and the required irradiation amount can be secured by changing the acceleration according to the speed in the constant velocity state and the number of irradiation lamps. Of course, lighting the lamp in the stopped state and lighting the lamp during acceleration may be combined. When the lamp 27c is turned on, the entire panel can be illuminated by the lamp 27c, so the lamp 27c can be turned on immediately before the carrying operation.
By turning on the lamp 27c, the acceleration can be increased and the cycle time can be shortened. However, when the lamp 27c is no longer turned on, the irradiation amount can be secured by shifting the stop position to the upper side in FIG.

On the end side of the erasing scan, the halogen lamps 27, which are removed from the panel 4, are sequentially turned off,
It is possible to avoid unnecessary lighting of the halogen lamp 27. In the above embodiment, the erasing light amount is increased / decreased depending on the number of halogen lamps 27 provided, but the light emitting amount of one light source may be increased / decreased. The erasing light source may be a light source that emits spot light instead of the linear light source, and further, the linear light source may be provided so as to extend in the sub-scanning direction and scan in the main scanning direction. .

Further, as disclosed in JP-A-61-206361, the erasing light irradiation amount (light emitting amount and erasing speed) determined based on the detection result of residual radiation energy is read dynamically. The configuration may be such that the correction is set according to the range. Further, the panel after the radiation image information is read by the excitation light may be conveyed to an individually provided erasing device to erase the afterimage.

[0037]

As described above, according to the radiation image reading apparatus of the present invention, at the time of erasing the afterimage after reading the radiation image, at least one of the erasing light amount and the scanning speed of the erasing light is controlled according to the reading dynamic range. Therefore, when the reading is performed in a high dynamic range, the afterimage at the time of the previous photographing is completely erased, high-quality radiation image information can be obtained, and complete emission of residual energy is not required. When the dynamic range is read, the irradiation amount of the erasing light can be suppressed to be low, and the energy consumption and the lengthening of the cycle time accompanying the erasing operation can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a radiation image reading apparatus according to the present invention.

FIG. 2 is a system block diagram showing an embodiment of a radiation image reading apparatus according to the present invention.

FIG. 3 is a system schematic diagram showing a reading unit section in the embodiment.

FIG. 4 is a block diagram showing an erase control portion in the embodiment.

FIG. 5 is a diagram for explaining characteristics of an erase operation in the same embodiment.

[Explanation of symbols]

 1 Radiation Source 3 Recording / Reading Device 4 Radiation Image Conversion Panel 5 Laser Beam Generation Unit 6 Scanner 7 Reflector 8 Condenser 9 Filter 10 Photomul 11 Current / Voltage Converter 12 Amplifier 13 A / D Converter 17 Reading Dynamic Range Adjustment circuit 18 High voltage power supply for Photomul 21 Sub-scanning unit 24 Sub-scanning motor 25 Motor drive circuit 27 Halogen lamp 28 CPU 29 Controller

Claims (1)

[Claims] 1. A radiation image conversion panel that accumulates and records radiation image information by absorbing radiation from a radiation generation source that has passed through an object into a stimulable phosphor, and scans the radiation image conversion panel with excitation light. By this means, the radiation image information accumulated and recorded in the stimulable phosphor is stimulated to emit light, and the reading means for photoelectrically reading the stimulated emission to obtain the radiation image information, and the dynamic range in the reading means are variably set. Read dynamic range control means, afterimage reading means that scans the radiation image conversion panel with erasing light after reading by the reading means, and erases an afterimage due to residual radiation energy; and the read dynamic range control means. The amount of erasing light and the scanning speed of the erasing light in the afterimage erasing means according to the reading dynamic range. An erasing control means for controlling at least one of the following: and a radiographic image reading device.