JP2003215065A - Radiation imaging apparatus - Google Patents

Abstract

(57) Abstract: Provided is a radiation imaging apparatus capable of reducing a load on an X-ray tube apparatus and effectively using emitted X-rays to image a subject on a belt conveyor. A surveillance camera detects that a subject is placed on a conveyance belt of a conveyance device and moves, and a signal is sent to a control device. After the time calculated from the moving speed, the subject 4
When is located in the field of view, the X-ray tube apparatus 2 limits the irradiation field by the collimator 3 and emits pulsed X-rays.
An X-ray transmission image of the subject 4 is detected by the flat panel detector 1 and displayed on the image display device 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation imaging apparatus used in the field of nondestructive inspection of foods.

[0002]

2. Description of the Related Art In the field of non-destructive inspection, inspecting items on a belt conveyor is used to check whether foreign substances are mixed in food or the like, and whether dangerous items are included in baggage at airport baggage inspection. Flow between the X-ray tube device and the linear array detector, and from the transmission image or data, the presence or absence of foreign matter,
The presence or absence of dangerous goods is judged. The linear array detector is
A plurality of radiation detecting elements are arranged one-dimensionally, and a two-dimensional transmission image is obtained by scanning an object with this linear array detector. FIG. 5 shows a system of a conventional radiation imaging apparatus. X-ray tube device 2, collimator 1
0, the slit 10a, the carrier device 5, the linear array detector 9 and the like are housed in an inspection box (not shown), and the inspection box is an entire body in order to prevent a leak dose such as scattered radiation from affecting the human body. Is an X-ray protection box, and an X-ray shielding goodwill made of lead rubber is provided at the entrance and exit of the opening. Turn on the power to the operation panel (not shown) of the carrier device 5.
When N, the drive unit of the belt conveyor operates and the loop belt moves in the direction of the arrow along each pulley. Subject 4
When is placed on a belt conveyor that moves from the entrance of the opening, it is transported into the inspection box. An X-ray tube device 2 is provided on the upper part, and a high voltage generator (not shown) is provided by the control device 8.
Is applied to the X-ray tube device 2 to generate X-rays.
The generated X-rays are narrowed down by a collimator 10 and elongated slits 10 provided at right angles to the belt moving direction.
The object 4 that has passed through a and is sent on the loop belt at the center of the belt conveyor of the transport device 5 is transmitted. Then, the transmitted X-rays are detected by the linear array detector 9 provided at the lower part and connected to the control device 8. The signal detected by the linear array detector 9 is sent to a data processing device (not shown), the processed signal is displayed on the image display device 6, and an X-ray image of the subject 4 in which a foreign substance or a dangerous substance is present. Is checked on the image display device 6 and on the data, and is discharged from the conveyor or marked on the actual product in response to a signal from the control device 8 to be extracted. The result is output to the data printer and the video printer.
The linear array detector 9 is a one-dimensional line sensor including a plurality of elements provided below the belt conveyor, and includes a scintillator and a MOS type image sensor. The scintillator provided on the front surface is an X-ray conversion film that converts into visible light by exciting X-rays, and is a general sensitizing film used for X-ray photography, Gd ₂ O ₂ S: T.
b is used, and a MOS type image sensor is fixed to the back of the b. The MOS image sensor includes a p-type semiconductor and an n-type semiconductor, which are semiconductors of an optical sensor, and an electronic circuit for transferring the optical signal to the outside is formed for each element.

[0003]

Although the conventional radiation imaging apparatus is constructed as described above, in the linear array detector 9, the X-ray is focused by the collimator 10 and provided in the direction perpendicular to the belt moving direction. There is a problem that most of the generated X-rays are not effectively used because the subject 4 is irradiated with the narrow slit 10a. Further, since the linear array detector 9 is one-dimensional, in order to form a two-dimensional transmission image of the subject 4, it is necessary to continuously irradiate X-rays while scanning the subject 4. However, there is a problem that an excessive load is applied to the X-ray tube device 2.

The present invention has been made in view of the above circumstances, and reduces the load on the X-ray tube device and effectively uses the emitted X-rays to image the subject on the belt conveyor. It is an object of the present invention to provide a radiation imaging apparatus that can do the above.

[0005]

In order to achieve the above-mentioned object, the radiation imaging apparatus of the present invention has a radiation generating means, a radiation detecting means, and an object which is continuously arranged between the radiation generating means and the radiation detecting means. In a radiation imaging apparatus for imaging a transported subject, the flat panel radiation detector including a plurality of radiation detecting elements arranged two-dimensionally is used as the radiation detecting means. It is configured by.

Further, the radiation imaging apparatus of the present invention is the apparatus according to claim 1, wherein when the radiation generating means conveys an object to an imaging position between the radiation generating means and the radiation detecting means, it is intermittent. It is designed to emit radiation and image.

Further, in the radiation imaging apparatus of the present invention, in the apparatus according to claim 1, the radiation generating means tilts the radiation to the left side of the object conveyed to the imaging position between the radiation generating means and the radiation detecting means. And at least 2 diagonally to the right
It radiates twice and images.

The radiation image pickup apparatus of the present invention is constructed as described above, and a radiation generating means, a flat panel radiation detector comprising a plurality of radiation detecting elements arranged two-dimensionally, and the radiation generating means thereof. And a radiation detector for continuously carrying the object between the radiation detector and the radiation detector, and when the object is carried to the imaging position, the radiation is emitted intermittently (in a pulsed manner) to the flat panel radiation at a time. The image is picked up by a detector. Instead of the conventional linear array detector, a flat panel detector is used for imaging by pulsed X-ray radiation, which reduces the load on the X-ray tube device and effectively uses the emitted X-rays. To be done. Radiation is emitted to the subject conveyed to the imaging position at least twice from diagonally to the left and diagonally to the right, and is picked up and imaged in parallel on a monitor for stereoscopic viewing. A stereoscopic transmission image can be obtained by observing with the observation device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the radiation imaging apparatus of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram showing an X-ray imaging state by carrying a belt conveyor provided in an inspection box (not shown) of the radiation imaging apparatus of the present invention. The radiation imaging apparatus includes an X-ray tube device 2, a collimator 3 that limits an X-ray irradiation field, a transport device 5 that transports a subject 4 on a belt conveyor, and a monitoring camera that detects the position of the subject 4 on the belt conveyor. 7 and the X-ray of the subject 4 which is provided below the belt conveyor so as to face the X-ray tube device 2.
It is composed of a flat panel detector 1 for detecting a line transmission image, an image display device 6 for displaying the detected image, and a control device 8 for controlling each part.

In the X-ray tube device 2, the voltage applied to the X-ray tube differs depending on the subject 4, and there is a device having a current of about 5 to 160 kV and a current of about 0 to 500 mA. Further, those having different X-ray tube focal points are selected depending on the size of foreign matter and the resolution required for shape determination. And intermittently for a short time (usually 5 ms
The inspection is performed by irradiating X-rays of pulse irradiation of up to 500 ms). Therefore, the temperature rise of the X-ray tube device 2 is much lower than that of the conventional continuous X-ray radiation, and the device itself can be made compact. The collimator 3 limits the irradiation field of X-rays in the XY direction with a blade such as lead. The collimator 3 is set according to the size of the subject 4, and the maximum detector field of view of the flat panel detector 1 provided at the bottom. Can be up to. The transport device 5 continuously transports the subject 4 between the X-ray tube device 2 and the flat panel detector 1,
The X-ray emitted from the X-ray tube device 2 is applied to the subject 4 through the collimator 3 and is composed of a belt conveyor controlled by an operation panel (not shown). When the operation panel is operated and the switch of the transport section is turned on, the drive section rotates and the loop belt moves on the pulley at the set speed. The monitoring camera 7 monitors the moving subject 4 on the belt conveyor of the transport device 5. When the subject 4 comes directly under the monitoring camera 7, the position is detected and the signal is sent to the control device 8. The control device 8 controls the X-ray tube device 2, the surveillance camera 7, and the flat panel detector 1, and in particular,
The time required for the subject 4 to move to the X-ray irradiation field between the X-ray tube device 2 and the flat panel detector 1 in response to the signal from the surveillance camera 7 is calculated from a preset moving speed,
After that time, a signal is sent to the X-ray tube device 2, and X-rays are radiated in a pulse shape for a short time. The image display device 6 receives the signal of the X-ray transmission image of the subject 4 detected by the flat panel detector 1 via an image processing device (not shown), and displays the X-ray image on the monitor. it can.

Next, the flat panel detector 1 is shown in FIG.
Will be described with reference to. FIG. 2 shows the radiation detection surface 101.
2 shows a control circuit for the sensor pixels 11 to 55 arranged two-dimensionally. The radiation detection surface 101 includes 25 sensor pixels 11, 12, ..., 55 arranged in a 5 × 5 matrix, and gate lines 71, 7 input commonly to each row.
2, ..., 75 and output signal lines 61, 6 common to each column
2, ..., 65 are wired. Here, the number of pixels is set to 5 × 5 for convenience of description, but in reality, it is 4096 ×
Those having about 4096 pixels are used. Gate line 71,
72, ..., 75 are sequentially and selectively driven by the gate driver circuit 102. The output from the sensor belonging to the driven row is output signal lines 61, 62, ...
The signal is output through 65 and input to the amplifier circuit 103.
The control circuit 104 is provided to integrally control the operations of the gate driver circuit 102 and the read amplifier circuit 103, and sequentially drives the gate lines 71, 72, 73, ... Collect the output data of
Finally, a two-dimensional image is constructed. FIG. 3 shows a sectional structure of one sensor pixel 12. The sensor pixel 12 has a common electrode 108 for applying a bias voltage, an X-ray conversion layer 109 for converting an X-ray into a charge signal, a pixel electrode 121 for collecting a charge signal generated in the X-ray conversion layer 109, and a collection electrode. And a transistor switch 123 (generally called a TFT) for introducing the charges accumulated in the accumulation capacitor 122 into an external circuit. The X-rays that have entered the X-ray conversion film 109 are converted into charge signals within the X-ray conversion film 109 and driven by the applied internal electric field to reach the pixel electrodes 121, where they are stored in the storage capacitors 122 as charge signals. Can be stored.

Next, the operation of the radiation imaging apparatus will be described. First, the subject 4 is carried by the carrying device 5 from the right direction to the left direction in FIG. 1 at a predetermined speed. Subject 4
However, X-rays have not yet been emitted at the time of being at the right end of the carrier device 5. When the transported subject 4 moves from the right end of the transport device 5 and passes under the surveillance camera 7, the image of the subject 4 captured by the surveillance camera 7 is sent to the control device 8. Therefore, the arrival time required to reach the position directly below the X-ray tube device 2 is calculated from the preset moving speed of the transport device 5. When the arrival time has elapsed, the control device 8 causes the X-ray tube device 2 to move to the X-ray tube device 2 for a short time (5 ms to 500 ms).
ms) pulse irradiation is instructed, and a transmission image of the subject 4 is captured by the flat panel detector 1. At this time, the collimator 3 has a function of narrowing down the X-ray irradiation area and is adjusted according to the imaging area of the flat panel detector 1. The captured image is sent to the monitor of the image display device 6 and displayed. In the conventional device, as shown in FIG.
The linear array detector 9 of a line sensor is used as a line detector, and X-rays are continuously emitted from the elongated slit 10a. The load of the X-ray tube device 2 is large, and the emitted X-rays are effectively used. Although not done, this device uses the two-dimensional flat panel detector 1 for a short time (5 ms to 500 m).
X-rays are emitted by the pulse irradiation of s), and the load on the X-ray tube device 2 is reduced and the X-rays are effectively used.

Next, another embodiment of the radiation imaging apparatus of the present invention will be described with reference to FIG. FIG. 4 shows the subject 4.
FIG. 6 is a diagram showing a state in which X-rays are radiated onto the subject 4 at least twice from diagonally left and diagonally right when the image is transported to the imaging position between the X-ray tube device 2 and the flat panel detector 1 and imaged. Although the configuration of the radiation imaging apparatus is the same as that in FIG. 1, X-ray pulse irradiation is performed twice during the period in which the subject 4 is being conveyed, and the subject 4a is pulse-irradiated from the diagonal left direction and then imaged. , The subject 4b is imaged by irradiating the subject 4b with pulses from the diagonally right direction, displayed in parallel on the monitor of the image display device 6, and observed using a stereoscopic viewing device (not shown). It is possible to obtain a stereoscopic transmission image of. For example, in order to easily view stereoscopically, by placing a vertical stand at the center of the images displayed on the monitors in parallel, the left eye observes the left image, and the right eye observes the right image. You can observe three stereoscopic images. Also, using a color display monitor, the left image is displayed with a red signal and the right image is displayed with a blue signal on one monitor, and the parallax (shift due to the captured angle) is shifted and combined and displayed at the same location. A stereoscopic image can be observed by observing with special glasses having red and blue color filters on the left and right.

[0014]

The radiation image pickup apparatus of the present invention is configured as described above, and is provided with an X-ray tube apparatus, a flat panel radiation detector, and a belt conveyor that continuously conveys an object between them. When a subject is conveyed to the imaging position, pulse X-rays are emitted and the subject is imaged at once with a flat panel radiation detector. Unlike imaging with a detector, irradiation time is short and utilization efficiency is high, so the load on the X-ray tube device is small. As a result, the cooling mechanism of the X-ray tube device can be simplified and the device can be downsized. Then, the power consumption can be reduced and the leakage dose of the device can also be reduced. Further, X-rays are radiated in a pulsed manner at least twice from diagonally to the left and diagonally to the right to the subject conveyed to the imaging position, the images are displayed in parallel on a monitor, and this is displayed for stereoscopic viewing. By observing with a observing device and seeing a stereoscopic transmission image of the subject, it is possible to improve the ability to detect foreign substances and dangerous substances.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a radiation imaging apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a flat panel detector.

FIG. 3 is a diagram showing the structure of one pixel of a flat panel detector.

FIG. 4 is a diagram showing another embodiment of the radiation imaging apparatus of the present invention.

FIG. 5 is a diagram showing a conventional radiation imaging apparatus.

[Explanation of symbols]

1 ... Flat panel detector 2 ... X-ray tube device 3, 10 ... Collimator 4, 4a, 4b ... Subject 5 ... Conveyor 6 ... Image display device 7 ... Surveillance camera 8 ... Control device 9 ... Linear array detector 10a ... slit 11-55 ... Sensor pixel 61-65 ... Output signal lines 71 to 75 ... Gate line 101 ... Radiation detection surface 102 ... Gate driver circuit 103 ... Amplifying circuit 104 ... Control circuit 108 ... Common electrode 109 ... X-ray conversion film 121 ... Pixel electrode 122 ... storage capacity 123 ... Transistor switch

Claims (3)

[Claims] Claim: What is claimed is: 1. Radiation that includes radiation generating means, radiation detecting means, and transporting means for continuously transporting a subject between the radiation generating means and the radiation detecting means, and imaging the transported subject. In the image pickup apparatus, a flat panel radiation detector including a plurality of radiation detection elements arranged two-dimensionally is used as the radiation detection unit. 2. The radiation generating means intermittently emits radiation and images when a subject is conveyed to an imaging position between the radiation generating means and the radiation detecting means. Radiation imaging device. 3. The radiation generating means is characterized by radiating radiation to a subject conveyed to an imaging position between the radiation generating means and the radiation detecting means at least twice from diagonally leftward and diagonally rightward to image the subject. The radiation imaging apparatus according to claim 1.