CN104502944A - Method for lowering detecting dose of radiation imaging system - Google Patents
Method for lowering detecting dose of radiation imaging system Download PDFInfo
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- CN104502944A CN104502944A CN201410818725.1A CN201410818725A CN104502944A CN 104502944 A CN104502944 A CN 104502944A CN 201410818725 A CN201410818725 A CN 201410818725A CN 104502944 A CN104502944 A CN 104502944A
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Abstract
The invention discloses a method for lowering detecting dose of a radiation imaging system. The system comprises a ray source, a front collimator and an array detector, wherein a detecting channel for passing through a to-be-detected object is formed between the front collimator and the array detector; the front collimator is used for collimating rays emitted by the ray source into a sheet fan-shaped beam; the sheet fan-shaped beam penetrates through the detecting channel and then is received and imaged through the array detector; the width of a complete shadow area of the sheet fan-shaped beam, when the sheet fan-shaped beam reaches an incident window of each detector in the corresponding array detector, is matched with the width of the ray incident window of the detector. The width of the incident window area of the sheet fan-shaped beam is matched with the width of the ray incident window of the detector through the front collimator, so that not only can the rays of the complete shadow area be effectively utilized to scan and image, reduce useless rays entering the detector and guarantee the image quality, but also the quantity of rays radiated on the detected object can be reduced as much as possible to lower the detecting dose.
Description
Technical field
The invention belongs to Application of Nuclear Technology field, be specifically related to a kind of method that transmission-type radiation image-forming system reducing the goods, lorry, container etc. being widely used in customs, airport, harbour, station, road gate etc. at present detects dosage.
Background technology
For customs, airport, harbour, the goods at station, lorry, the radiation image-forming detecting system of container etc. is usually by radiographic source, front collimating apparatus, rear collimating apparatus, detector is formed, after the ray that radiographic source sends premenstrual collimating device collimation slabbing fladellum, received and imaging by detector array through after the examining object in sense channel, for ensureing detector reliable reception ray, the thickness of sheet fladellum is often much larger than the width of detector incidence window, for this reason, also need to arrange rear collimating apparatus before detector and sheet beam is collimated into thickness further and detector incidence window matches, to stop that useless transmitted ray and scattered ray enter detector, interference search gear outputs signal, reduce picture quality.
Because the thickness of the sheet ray through sense channel is larger, cause detection dosage larger, thus during this detection system work, passengers inside the car must get off and to pass through from sense channel, vehicle is pulled through sense channel by haulage gear or actuator, or vehicle is motionless, detect door frame across on vehicle, inswept tested vehicle, detection speed is generally 6 ~ 18m/min, i.e. 0.36 ~ 1.08km/h, percent of pass about 10 ~ 30 car/h, detection efficiency is lower, and needs actuator or door frame guide rail, and equipment is complicated.Meanwhile, also need to arrange special rear collimating apparatus, and the radiation safety control zone area of door frame both sides is comparatively large, need increase radiological safety protection structure, further increase complexity and the processing cost of equipment.
Summary of the invention
For prior art Problems existing, the object of the invention is to provide a kind of transmission-type radiation image-forming system reducing existing goods, lorry, container etc. to detect the method for dosage.Adopt the method, under the prerequisite ensureing image quality, both reduced detection dosage, and also reduced the area of radiation safety control zone, decrease safeguard structure.
For achieving the above object, the technology of the present invention solution is as follows:
A kind of method reducing radiation image-forming system detection dosage, described system comprises radiographic source, front collimating apparatus, detector array, sense channel for passing through for examining object between front collimating apparatus and detector array, the ray that radiographic source sends by front collimating apparatus is collimated into sheet fladellum, this sheet fladellum is received and imaging by detector array through after sense channel, and complete shadow width when described sheet fladellum arrives each detector entrance window in corresponding detector array matches with the width of this detector ray entrance window.
Further, the envelope angle that the subtended angle of described sheet fladellum complete shadow surrounds with described detector array and described radiographic source matches.
Further, the subtended angle of described sheet fladellum complete shadow equals or slightly larger than the envelope angle surrounded by detector array and radiographic source.
Further, complete shadow width when described sheet fladellum arrives each detector entrance window in corresponding described detector array equals or slightly larger than the width of this detector ray entrance window.
Further, the Collimation Ratio of described front collimating apparatus is 100 ~ 200.
Further, the entrance window width of described detector is 5 ~ 30mm.
Further, described radiographic source is cobalt-60 radioactive source of activity 0.8 ~ 30 Curie, or the x-ray source of 225 ~ 450keV.
Further, the outer contour shape of the ray exit portal of described front collimating apparatus is the similar shape corresponding with the spread geometry of detector in described detector array.
The present invention makes sheet fladellum complete shadow width and detector ray entrance window width match by front collimating apparatus, both effectively make use of complete shadow ray and carry out scanning imagery, decrease the useless ray entering detector, ensure that picture quality, decrease again the amount of radiation be irradiated on tested object as far as possible, reduce the radiation dose that tested object is subject to, thus reduce detection dosage.
Employing Collimation Ratio is the front collimating apparatus of 100 ~ 200, further reduces sheet fan-ray beam penumbra region width, thus reduces detection dosage further.
Adopt activity be the cobalt-60 of 0.8 ~ 30 Curie or low intensive X-ray machine as radiographic source, also reduce further radiation dose.
Along with the reduction of radiation dose, apply radiation image-forming detecting system of the present invention when for detecting vehicle, vehicle is without the need to stopping, driver on car and occupant are without the need to getting off, low vehicle speeds passes through sense channel, both can obtain the full rung comprising occupant and penetrate scan image, the radiation safety of passengers inside the car can have been ensured again simultaneously.The speed of the tested vehicle passing detection passage of this system is generally such as 6 ~ 20km/h, when speed is lower than 6km/h, passengers inside the car's radioactive dose can higher than relevant human body safety check dose limit standard, when speed is higher than 20km/h, poor image quality, can not meet testing requirement.When detecting with this speed, vehicle percent of pass can reach 500 car/h, can meet the vehicle pass-through rate requirement of busy highway safety check bayonet socket, customs's clearance passage etc., can not cause traffic congestion.
Accompanying drawing explanation
Fig. 1 is transmission-type radiation image-forming detecting system structural representation;
Fig. 2 is the principle schematic that ray forms complete shadow and penumbra region after front collimating device collimation.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be described.
Fig. 1 is the radiation image-forming detecting system for detecting vehicle.As shown in Figure 1, this detection system comprises frame, radiographic source, front collimating apparatus, detector array.Frame is rigid frame structure, is formed by connecting by entablature 1, right column 2, sill 3, left column 4.Radiographic source 5, front collimating apparatus 6 are fixed on entablature 1, and with entablature 1 centering.Detector array is made up of several detectors 8, can comprise several detector cells and also only can comprise a detector cells in each detector 8; These detectors 8 are closely arranged along left column 4, sill 3, right column 2, make the detector array overall U-shaped of composition; Each detector 8 is arranged in the cavity in left column 4, sill 3, right column 2 respectively.
Certainly radiographic source 5 also can be adopted to be positioned at the middle part of sill 3, closely arrangement is in inverted U-shaped version in left column 4, entablature 1, right column 2 for detector 8, and now ray is from bottom to top in fan-shaped, and what can obtain tested vehicle looks up scanning radiation image.Can also adopt and divide radiographic source 5 and detector array the left and right sides being listed in sense channel, radiographic source 5 is positioned at one of them column lower end, and detector array is laid in another column and entablature, overall in inverted L-shaped, adopts horizontal projection imaging mode.
As shown in Figure 2, because radiographic source 5 sends the region of ray, the active region of such as radioactive source or the focal spot of X-ray tube, all have certain spatial form and yardstick, can form complete shadow 9 and penumbra region 10 after the premenstrual collimating apparatus 6 of X or g ray that thus radiographic source 5 sends collimates, wherein the transmitted intensity of complete shadow 9 is even, it is full strength ray, and the transmitted intensity of penumbra region 10 is uneven, and lower the closer to edge, be the ray of partial intensities.Utilize detector 8 to penetrate the ray after checking matter to detect complete shadow ray, good picture quality can be obtained.Although the transmitted ray of penumbra region and all scattered ray are not all contributed imaging, even affect picture quality, but these rays can be irradiated on tested object equally, also will be irradiated to it the driver and conductor in tested vehicle, unnecessarily add radiation dose.For this reason, to utilize front collimating apparatus 6 ray that radiographic source 5 sends to be collimated into the complete shadow width of corresponding each detector 8 identical or slightly wide with the ray entrance window width of this detector 8 in the present invention.Equally, also complete shadow and penumbra region is there is in this fladellum subtended angle direction, the present invention utilizes front collimating apparatus 6 to be collimated into by ray the subtended angle of fladellum complete shadow is equaled or slightly larger than the envelope angle surrounded by detector array and radiographic source, can while guarantee picture quality, effective reduction detects dosage, reduces the area in defense controls district, door frame both sides.
In X or g x radiation x imaging field, radiographic source is enclosed in shielded metal container usually, only there are a flat fan passage or tapered channel for ray outgoing, and be close to exit portal front collimating apparatus is set, then be close to front collimating apparatus and shutter (the two also can switch) is set, wherein shutter is used for switch ray, and front collimating apparatus is used for collimated rays.The collimating slit length of front collimating apparatus is called Collimation Ratio with the ratio of width.As seen from Figure 2, Collimation Ratio is larger, and penumbra region 10 is less.In the present invention, in order to reduce penumbra region as far as possible, reducing further and detecting dosage, employing Collimation Ratio is the front collimating apparatus of 100 ~ 200.Collimation Ratio is too little, and penumbra region area increases; Collimation Ratio is too large, and front collimating apparatus is just oversize too heavy, both uneconomical, unsightly, too increase the complicacy of portal-framed structure.
Because detector array overall arrangement in door frame takes the shape of the letter U or L shape, in order to make the even width arriving the fan-ray beam of detector array ray entrance window after collimation consistent, and match with the ray entrance window width of each detector 8, the outer contour shape of front collimating apparatus 6 ray exit portal is the similar U-shaped corresponding with the spread geometry of detector array or L shape.
To equal by making the complete shadow width of sheet fan-ray beam or slightly larger than the ray entrance window width of detector 8, and the subtended angle of sheet fladellum complete shadow is equaled or slightly larger than the envelope angle surrounded by detector array and radiographic source, both ensure that image quality, decrease again the quantity of the ray through sense channel as far as possible, thus reduce detection dosage.
In order to reduce detection dosage further, the present invention also adopts low-intensity radiographic source, as cobalt-60 radioactive source of activity 0.8 ~ 30 Curie, or 225 ~ 450keV, 1 ~ 5mA X-ray machine.
Above-mentioned vehicle radiating imaging detection system is when carrying out testing, personnel can be low to moderate 0.1mSv from its sense channel through the exposure dose suffered by one-time detection, only be equivalent to the cosmic rays dosage that by air, by plane 1 minute human body accepts, or 1/100 of a dental x mating plate dosage, meet the safety standard requirement of human body safety check dosage ￡ 0.25mSv in Unite States Standard (USS) ANSI N43.17 the most harsh in the world.
In above-described embodiment, radiographic source 5 is positioned on the entablature above sense channel, and detector array is arranged in sense channel two heel post and sill, overall U-shaped, adopts and overlooks imaging mode.In practical application, radiographic source 5 also can be arranged on the sill below sense channel, and is arranged on by detector array in sense channel two heel post and entablature, overall in inverted U-shaped, adopts and looks up imaging mode.Certainly, also can divide radiographic source 5 and detector array the left and right sides being listed in sense channel, radiographic source 5 is positioned at one of them column lower end, and detector array is laid in another column and entablature, overall in inverted L-shaped, adopts horizontal projection imaging mode.
The detection system of the inventive method is adopted not only to detect dosage low, and due to the subtended angle of fladellum ray and width all considered critical, drip catcher 7 can also be set at the two heel post back sides, to absorb the ray through detector and door frame, the radiation safety control zone area of further reduction door frame both sides, and portal-framed structure is simple, floor area is little, and the high pass rate vehicle being applicable to the places such as ordinary road bayonet socket, security check, customs corridor and important place vehicle in and out port fast and safely checks.
Claims (8)
1. one kind is reduced the method that radiation image-forming system detects dosage, described system comprises radiographic source, front collimating apparatus, detector array, sense channel for passing through for examining object between front collimating apparatus and detector array, the ray that radiographic source sends by front collimating apparatus is collimated into sheet fladellum, this sheet fladellum is received and imaging by detector array through after sense channel, it is characterized in that, complete shadow width when described sheet fladellum arrives each detector entrance window in corresponding detector array matches with the width of this detector ray entrance window.
2. the method for claim 1, is characterized in that, the envelope angle that the subtended angle of described sheet fladellum complete shadow surrounds with described detector array and described radiographic source matches.
3. method as claimed in claim 2, is characterized in that, the subtended angle of described sheet fladellum complete shadow equals or slightly larger than the envelope angle surrounded by detector array and radiographic source.
4. the method for claim 1, is characterized in that, complete shadow width when described sheet fladellum arrives each detector entrance window in corresponding described detector array equals or slightly larger than the width of this detector ray entrance window.
5. the method for claim 1, is characterized in that, the Collimation Ratio of described front collimating apparatus is 100 ~ 200.
6. the method for claim 1, is characterized in that, the entrance window width of described detector is 5 ~ 30mm.
7. the method for claim 1, is characterized in that, described radiographic source is cobalt-60 radioactive source of activity 0.8 ~ 8 Curie, or the x-ray source of 225 ~ 450keV.
8. the method for claim 1, is characterized in that, the outer contour shape of the ray exit portal in described front collimating apparatus is the similar shape corresponding with the spread geometry of detector in described detector array.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201410818725.1A CN104502944A (en) | 2014-12-25 | 2014-12-25 | Method for lowering detecting dose of radiation imaging system |
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| CN201410818725.1A CN104502944A (en) | 2014-12-25 | 2014-12-25 | Method for lowering detecting dose of radiation imaging system |
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Cited By (4)
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| CN107764847A (en) * | 2016-08-18 | 2018-03-06 | 株式会社理学 | X-ray diffraction device |
| CN109507713A (en) * | 2018-11-09 | 2019-03-22 | 清华大学 | Handheld gamma radiation imaging apparatus and method |
| CN111856605A (en) * | 2020-07-31 | 2020-10-30 | 李国军 | Multi-view vertical base-illumination X-ray security inspection machine |
| CN111884143A (en) * | 2020-08-04 | 2020-11-03 | 广州狸园科技有限公司 | Be used for big data modularization network wiring device |
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| CN1242519A (en) * | 1999-07-23 | 2000-01-26 | 清华大学 | Digital radiation image forming type apparatus for investigating lorge guest materials |
| EP1635169A1 (en) * | 2004-09-13 | 2006-03-15 | Rapiscan Security Products Inc. | Self contained mobile x-ray inspection system and method |
| CN101051029A (en) * | 2007-05-11 | 2007-10-10 | 清华大学 | Mobile sedan radiation image detecting system |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107764847A (en) * | 2016-08-18 | 2018-03-06 | 株式会社理学 | X-ray diffraction device |
| CN109507713A (en) * | 2018-11-09 | 2019-03-22 | 清华大学 | Handheld gamma radiation imaging apparatus and method |
| CN111856605A (en) * | 2020-07-31 | 2020-10-30 | 李国军 | Multi-view vertical base-illumination X-ray security inspection machine |
| CN111884143A (en) * | 2020-08-04 | 2020-11-03 | 广州狸园科技有限公司 | Be used for big data modularization network wiring device |
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Application publication date: 20150408 |