Source: https://patents.google.com/patent/US8503605B2/en
Timestamp: 2019-04-26 12:02:01
Document Index: 72512853

Matched Legal Cases: ['Application No. 60', 'Application No. 61', 'Application No. 60', 'Application No. 60', 'Application No. 61', 'art 2008']

US8503605B2 - Four sided imaging system and method for detection of contraband - Google Patents
Four sided imaging system and method for detection of contraband Download PDF
US8503605B2
US8503605B2 US12/834,890 US83489010A US8503605B2 US 8503605 B2 US8503605 B2 US 8503605B2 US 83489010 A US83489010 A US 83489010A US 8503605 B2 US8503605 B2 US 8503605B2
US12/834,890
US20110064192A1 (en
2003-09-12 Priority to US50249803P priority
2004-09-13 Priority to US10/939,986 priority patent/US7486768B2/en
2007-01-12 Priority to US11/622,560 priority patent/US7369643B2/en
2007-11-02 Priority to US98478607P priority
2007-12-19 Priority to US1481407P priority
2008-03-20 Priority to US12/051,910 priority patent/US7519148B2/en
2008-08-29 Priority to PCT/GB2008/002897 priority patent/WO2009027667A2/en
2008-10-31 Priority to US12/263,160 priority patent/US7783004B2/en
2008-12-19 Priority to US12/339,591 priority patent/US7963695B2/en
2009-01-07 Priority to US12/349,534 priority patent/US7720195B2/en
2009-03-02 Priority to US12/395,760 priority patent/US7876880B2/en
2009-03-03 Priority to US12/396,568 priority patent/US7817776B2/en
2009-05-22 Priority to US18047109P priority
2009-07-13 Priority to US22493809P priority
2010-04-05 Priority to US12/753,976 priority patent/US7995705B2/en
2010-05-21 Priority to US12/784,630 priority patent/US8275091B2/en
2010-07-12 Priority to US12/834,890 priority patent/US8503605B2/en
2010-07-12 Application filed by Rapiscan Systems Inc filed Critical Rapiscan Systems Inc
2011-03-17 Publication of US20110064192A1 publication Critical patent/US20110064192A1/en
2011-03-18 Assigned to RAPISCAN SYSTEMS, INC. reassignment RAPISCAN SYSTEMS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MORTON, EDWARD JAMES, KOTOWSKI, ANDREAS F
2013-08-06 Publication of US8503605B2 publication Critical patent/US8503605B2/en
The present invention provides a four-sided scanning system for vehicles that uses a combination of backscatter and transmission based X-ray imaging to achieve material discrimination. In one embodiment, the system is designed as a mobile, drive-through system, which can be folded and stowed in a truck and can be conveniently deployed at any place when required.
This application relies on U.S. Patent Provisional No. 61/224,938 filed on Jul. 13, 2009 and is hereby incorporated by reference in its entirety.
The present invention is a continuation-in-part of U.S. patent application Ser. No. 12/396,568, entitled “Single Boom Cargo Scanning System”, and filed on Mar. 3, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 11/948,814, entitled, “Single Boom Cargo Scanning System”, filed on Nov. 30, 2007, and now issued U.S. Pat. No. 7,517,149, which is a continuation of U.S. Pat. No. 7,322,745, entitled, “Single Boom Cargo Scanning System”, filed on Aug. 9, 2004, which relies on, for priority, U.S. Provisional Patent Application No. 60/493,935, filed on Aug. 8, 2003 and is a continuation-in-part of U.S. patent application Ser. No. 10/201,543, entitled “Self-Contained Portable Inspection System and Method”, filed on Jul. 23, 2002 and now U.S. Pat. No. 6,843,599. The '591 application further relies on U.S. Provisional Application No. 61/014,814, filed on Dec. 19, 2007, for priority.
The present invention is also a continuation-in-part of U.S. patent application Ser. No. 12/395,760, entitled “Single Boon Cargo Scanning System”, and filed on Mar. 2, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 12/051,910, entitled “Single Boom Cargo Scanning System”, and filed on Mar. 20, 2008, now issued U.S. Pat. No. 7,519,148, which is a continuation of U.S. Pat. No. 7,369,463, of the same title, filed on Jan. 12, 2007, which is a continuation-in-part of U.S. Pat. No. 7,322,745.
The present invention is a continuation-in-part of U.S. patent application Ser. No. 12/339,591, entitled Rotatable Boom Cargo Scanning System, filed on Dec. 19, 2008, which is a continuation-in-part of U.S. patent application Ser. No. 11/948,814, described above and also a continuation-in-part of U.S. patent application Ser. No. 12/051,910, described above.
The present invention is also a continuation-in-part of U.S. patent application Ser. No. 12/753,976, entitled “Self-Contained Mobile Inspection System”, and filed on Apr. 5, 2010, which is a continuation-in-part of Ser. No. 12/349,534, of the same title, and filed on Jan. 7, 2009 (and now issued U.S. Pat. No. 7,720,195) which is a continuation of U.S. patent application Ser. No. 10/939,986, entitled “Self-Contained Mobile Inspection System”, and filed on Sep. 13, 2004, which is a continuation-in-part of Ser. No. 10/915,687 (issued as U.S. Pat. No. 7,322,745), which is a continuation-in-part of Ser. No. 10/201,543 (issued as U.S. Pat. No. 6,843,599) and further relies on U.S. Provisional Patent Application No. 60/502,498, filed on Sep. 12, 2003, for priority.
The present invention is also a continuation-in-part of U.S. patent application Ser. No. 12/263,160, entitled “Cargo Scanning System”, and filed on Oct. 31, 2008, which further relies on U.S. Provisional Patent Application No. 60/984,786, filed on Nov. 2, 2007, for priority, and is a continuation-in-part of U.S. Pat. No. 7,322,745.
The present invention is also a continuation-in-part of U.S. patent application Ser. No. 12/675,471, entitled “Scanning Systems”, and filed on Feb. 26, 2010, which is a National Stage Entry of PCT/GB08/02897.
The present invention is also a continuation-in-part of U.S. patent application Ser. No. 12/784,630, entitled “Compact Cargo Mobile Scanning System”, and filed on May 21, 2010, which further relies on U.S. Provisional Patent Application No. 61/180,471, of the same title, and filed on May 22, 2009, for priority.
X-ray systems are used for medical, industrial and security inspection purposes because they can cost-effectively generate images of internal spaces not visible to the human eye. Materials exposed to X-ray radiation absorb differing amounts of X-ray radiation and, therefore, attenuate an X-ray beam to varying degrees, resulting in a transmitted or backscattered level of radiation that is characteristic of the material. The attenuated or backscattered radiation can be used to generate a useful depiction of the contents of the irradiated object. A typical single energy X-ray configuration used in security inspection equipment may have a fan-shaped or scanning X-ray beam that is transmitted through or backscattered by the object inspected. The absorption or backscattering of X-rays is measured by detectors after the beam has passed through the object and an image is produced of its contents and presented to an operator.
With limited space and a need to expand, finding suitable space to accommodate additional inspection facilities along the normal process route remains difficult. Additionally, selected locations are not necessarily permanent enough for port operators to commit to the long term installation of inspection equipment. Moreover, systems incorporating high-energy X-ray sources, or linear accelerators (LINAC), require either a major investment in shielding material (generally in the form of concrete formations or buildings) or the use of exclusion zones (dead space) around the building itself. In either case, the building footprint is significant depending upon the size of cargo containers to be inspected.
Conventional relocatable inspection systems generally comprise at least two booms, wherein one boom will contain a plurality of detectors and the other boom will contain at least one X-ray source. The detectors and X-ray source work in unison to scan the cargo on the moving vehicle. In conventional single boom relocatable inspection systems, the X-ray source is located on a truck or flatbed and the detectors on a boom structure extending outward from the truck. These systems are characterized by moving-scan-engine systems wherein the source-detector system moves with respect to a stationary object to be inspected. Also, the detectors and the source of radiation are either mounted on a moveable bed, boom or a vehicle such that they are integrally bound with the vehicle. This limits the flexibility of dismantling the entire system for optimum portability and adjustable deployment to accommodate a wide array of different sized cargo, shipments, vehicles, and other containers. As a result these systems can be complicated to deploy and pose several disadvantages and constraints. Conventional systems are disadvantageous in that they suffer from a lack of rigidity, are difficult to implement, and/or have smaller fields of vision.
Accordingly, there is need for improved inspection methods and systems built into a fully self-contained, over-the-road-legal vehicle that can be brought to a site and rapidly deployed for inspection. The improved method and system can, therefore, service multiple inspection sites and set up surprise inspections to thwart contraband traffickers who typically divert smuggling operations from border crossings that have tough interdiction measures to softer crossings with lesser inspection capabilities. Moreover, there is an additional need for methods and systems that require minimal footprint to perform inspection and that use a sufficient range of radiation energy spectrum to encompass safe and effective scanning of light commercial vehicles as well as substantially loaded 20-foot or 40-foot ISO cargo containers. It is important that such scanning is performed without comprising the integrity of the cargo and should ideally be readily deployable in a variety of environments ranging from airports to ports of entry where a single-sided inspection mode needs to be used due to congested environments. Similar needs are addressed in U.S. Pat. No. 6,543,599, entitled “Self-Contained Portable Inspection System and Method”, which is herein incorporated by reference in its entirety. In addition, there is a need for improved methods and systems that can provide comprehensive cargo scanning in portable and stationary settings.
In one embodiment, the first set of detectors is disposed on at least two of the same sides of the portal as the second set of detectors. In one embodiment, the first set of detectors comprises a first detector and a second detector adapted to measure an energy component of X-rays transmitted through the vehicle in a range of 0 keV to 50 keV and 20 keV to 200 keV, respectively, and a third detector to measure an energy component of X-rays transmitted through the vehicle in a range of 100 keV to 2 MeV. In one embodiment, the three detectors are in a stacked configuration. In one embodiment, a difference between an output of the third detector and a sum of outputs of the first and second detectors is used to achieve material discrimination.
In one embodiment, the system further comprises a sensor to measure a speed of the vehicle as it passes through the portal. In one embodiment, the system further comprises a controller wherein said controller is in data communication with the sensor and receives the speed of vehicle and wherein said controller is adapted to modulate a pulse rate of the X-ray source to attain a substantially constant dose per unit length of the vehicle under inspection based on the speed.
FIG. 1 is a schematic representation of the four-sided X-ray imaging system of the present invention;
FIG. 2 illustrates an orthogonal view of the four-sided X-ray imaging system of the present invention;
FIG. 3 a is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a first configuration;
FIG. 3 b illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system in a first configuration, as shown in FIG. 3 a;
FIG. 3 c is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a second configuration;
FIG. 3 d illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system in a second configuration, as shown in FIG. 3 c;
FIG. 3 e is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a third configuration;
FIG. 3 f illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system in a third configuration, as shown in FIG. 3 e;
FIG. 4 is an illustration of one embodiment of a triple-stacked detector element;
FIG. 5 is an integrator circuit diagram of signal processing as signals from each detector element are passed to the integrator circuits;
FIG. 6 a is a graphical representation of analyzed digital sensor values;
FIG. 6 b is another graphical representation of analyzed digital sensor values;
FIG. 7 is an illustration of one embodiment of a sensor that is capable of collecting backscattered radiation information and generating a backscatter image of a region;
FIG. 8 is a representative cross-section of one embodiment of an X-ray source that may be used with the present invention;
FIG. 9 is an illustration of the X-ray beam as it comes into contact with the object under inspection and the subsequent backscatter;
FIG. 10 a is an illustration of one embodiment of the present invention in which a pencil-like rotating collimator is replaced with a slot-like rotating collimator;
FIG. 10 b is a graphical representation of the time at which a pulsed X-ray source can be fired to create a corresponding line of an X-ray transmission image with no interference from the backscatter detector;
FIG. 11 a is an illustration of another embodiment of the present invention in which the scanning assembly may optionally be integrated with a transport trailer, in a first configuration;
FIG. 11 b is an illustration of another embodiment of the present invention in which the scanning assembly may optionally be integrated with a transport trailer, in a second configuration;
FIG. 11 c is an illustration of another embodiment of the present invention in which the scanning assembly may optionally be integrated with a transport trailer, in a third configuration;
FIG. 11 d is an illustration of another embodiment of the present invention in which the scanning assembly may optionally be integrated with a transport trailer, in a fourth configuration;
FIG. 12 depicts another embodiment of the present invention in which a four-sided backscatter detector is mounted around the periphery of the scanning volume/tunnel;
FIG. 13 a depicts another embodiment of the X-ray system of the present invention with an alternate transmission X-ray imaging geometry;
FIG. 13 b depicts another embodiment of the X-ray system of the present invention with an alternate transmission X-ray imaging geometry;
FIG. 13 c depicts another embodiment of the X-ray system of the present invention with an alternate transmission X-ray imaging geometry;
FIG. 14 is an illustration on another embodiment of the present invention where the system further includes vehicle detect sensors;
FIG. 15 is a composite image which overlays a backscatter signal with an optical image; and
FIG. 16 depicts an exemplary mechanism by which the optical image can be generated by taking an image signal from a mirror.
FIG. 1 is a schematic representation of one embodiment of a four-sided X-ray imaging system 100. As shown in FIG. 1, vehicle 105 drives over a ramp 110 and underneath an archway 115, which defines an inspection portal. Specifically, the portal is defined by a first (left) side 106, a second (right) side 107, a top side 108 and a bottom platform 109, which is a portion of the ramp. In one embodiment, ramp 110 comprises a base, a first angled surface leading upward to a flat transition point defining the highest part of the ramp, which also functions as the bottom platform 109, and a second angled surface leading back down to the ground. The highest part of the ramp is typically between 50 and 150 mm in height. In one embodiment, archway 115 houses multiple X-ray transmission detectors 117 and at least one X-ray source 119, housed within an enclosure, shown as 220 in FIG. 2.
While FIG. 1 depicts the X-ray source 119 as being on the left side 106 of the portal, one of ordinary skill in the art would appreciate that it could be on the right side 107, with an appropriate reconfiguration of the detectors 117. In one embodiment, the first side 106 has a height 106 a in a range of 2 meters to 5 meters and a width 106 b in a range of 2 meters to 4 meters; the second side 107 has a height 107 a in a range of 2 meters to 5 meters and a width 107 b in a range of 2 meters to 4 meters; the top side 108 has a length 108 a in a range of 2 meters to 5 meters and a width 108 b in a range of 2 meters to 4 meters; and the bottom platform 109 has a length 109 a in a range of 2 meters to 5 meters and a width 109 b in a range of 2 meters to 4 meters, where the width depends upon the location of the main aperture. Further, bottom platform 109 has a height in a range of 0.2 meter to 0.4 meter, depending upon the width; in one embodiment, a bottom platform 109 having a width of 2 meters has a height of 0.2 meter. Accordingly, the four sides, each having an interior face directed toward in the inspection region and an exterior face directed away from the inspection region, define an inspection portal having an inspection area of a minimum of 2 m2 to a maximum of 20 m2.
In one embodiment, a slit or opening 121 is provided on first side 106, through which X-rays are emitted. Slit or opening 121 extends substantially up first side 106 to approximately 100% of the height. In one embodiment, slit or opening 121 is covered with a thin coating that is easily transparent to an X-ray. In one embodiment, the thin coating is comprises of a material such as aluminium or plastic and further provides an environmental shield.
In one embodiment, with a dual-view system, an enclosure housing an X-ray source can be provided on both the first side 106 and second side 107.
FIG. 2 illustrates an orthogonal view of the system 200, showing both inlet ramp 210 a and exit ramp 210 b, as well as the X-ray source enclosure 220, containing X-ray source 219.
A transmission system in a “side-shooter” configuration, where the source enclosure is positioned on the first side or second side and emit X-rays toward one side of the vehicle, provides clear inspection of the doors, seats, engine compartment, luggage compartment and roof of the vehicle under inspection. However, such an image provides poor inspection of the floor plan of the vehicle. A “down-shooter” configuration, where the source enclosure is positioned the bottom portion of the first side or second side and emit X-rays from this bottom, lower position in an upward direction, provides a limited inspection capability for the roof of the vehicle since the X-ray signal for this region is superimposed over the complex and more attenuating X-ray signal of the floor (and passengers), thus resulting in an image of marginal value.
In order to provide good penetration of the denser, more highly attenuating objects within the vehicle, such as the engine and luggage compartments, it is advantageous to use a high energy X-ray source, even if tuned to a low output intensity. A suitable high voltage source has an energy ranging from 100 kVp to 2 MV. In one embodiment, at lower energies, a standard X-ray tube source is employed. In another embodiment, at higher energies, a pulse linear accelerator source is employed. In one embodiment of the present invention, standard operating energies are 200 kVp for the lower energy and 1 MV for the higher energy.
Referring back to FIG. 1, in order to provide a high level of inspection capability, ramp 110, over which the vehicle drives is equipped with, and contains therein, a backscatter X-ray unit which comprises a low energy X-ray source, typically having an energy ranging from 60 kVp to 250 kVp, and a plurality of detectors. It should be appreciated that the backscatter unit can be integrated into any floor structure which is movable and deployable to different locations and over which a car can drive. The backscatter signal from the floor of the vehicle is influenced strongly by regions of low atomic number material. Most regions of the vehicle floor are fabricated from high atomic number structural materials such as steel and therefore provide a small backscatter signal. The floor of a car is typically fabricated from relatively thin stamped steel, which typically has a thickness in the range of 1-2 mm. Typically, an X-ray beam can penetrate through this floor and into the objects just above. If low atomic number materials are positioned just above the floor, then these will be visible to X-ray backscatter detectors while they would be invisible to standard visual inspection.
Because it is highly advantageous to be able to rapidly and non-invasively deploy an X-ray system for security screening at a site in order to provide an element of surprise in the screening activity, in one embodiment, the present invention is a rapidly collapsible X-ray system that can be loaded onto a truck for transport between sites.
FIGS. 3 a, 3 b, 3 c, 3 d, 3 e, and 3 f depict one embodiment of a rapidly collapsible X-ray imaging system in several configurations. FIG. 3 a is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a first configuration, wherein the system is in a fully deployed position. Rapidly collapsible X-ray imaging system 300 comprises horizontal X-ray sensor section 305, a vertical boom section 310, a drive-over backscatter section 315 and a vertical boom support and collimator section 320 through which the transmission beam propagates from source 319. Further, X-ray imaging system 300 comprises ramp 325 (inlet and outlet) which allows a vehicle to drive over the X-ray backscatter unit seamlessly. FIG. 3 b illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system as shown in FIG. 3 a. FIG. 3 b illustrates source 319, vertical support and collimator section 320, horizontal X-ray sensor section 305, and ramp 325.
The rapidly deployable system of the present invention can be made ready for operation in a period of only a few minutes from arrival at the inspection site. In one embodiment, in order to stow the system ready for transportation, and referring back to FIG. 3 a, a set of hydraulic rams or other suitable mechanisms are used to collapse vertical boom sections 310 and 320 inward using hinges 321 and 322, respectively. Hinges 321 and 322 are positioned, in one embodiment, mid-way up the height of vertical boom sections 310 and 320, respectively. When vertical boom sections 310 and 320 are collapsed inward using hinges 321 and 322, horizontal boom section 305 is “lowered” such that it rests on top of collapsed vertical boom sections 310, 320.
FIG. 3 c is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a second configuration, wherein vertical boom sections 310 and 320 are folded inwards and collapsed at hinges 321, 322. FIG. 3 d illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system in a second configuration, as shown in FIG. 3 c, further showing ramp 325 and source 319.
FIG. 3 e is a schematic representation of one embodiment of a readily collapsible X-ray imaging system in a third configuration, wherein ramp sections 325 are folded upward using hydraulic rams or other suitable mechanisms. FIG. 3 f illustrates an orthogonal view of one embodiment of a readily collapsible X-ray imaging system in a third configuration, as shown in FIG. 3 e, illustrating ramp 325 which has been folded upwards at both the inlet and outlet. At this point, the system is ready for transport. It should be appreciated that the angled ramp outlet and inlet are hinged to the base platform and capable of moving up such that the tip 327 is directed upward, for achieving system mobility, and moving downward to form the completed ramp. The base platform preferably houses the above-described backscatter system.
In one embodiment, the X-ray imaging system of the present invention is capable of providing an image inspector with information relating to the types of material that are present in the object under inspection. In a large aperture inspection system of this type, a high energy X-ray beam is needed in order to penetrate through the object under inspection. This X-ray beam contains a broad spectrum of X-ray energies ranging from very low energies (typically less than 10 keV) up to the highest energy as determined by the tube or linear accelerator operating voltage (typically in the range of 100 keV to 2 MeV). Due to the unique composition of each material in the object under inspection, the materials each demonstrate specific attenuation of the X-ray beam, wherein this attenuation also comprises an energy dependent component.
FIG. 4 is a depiction of a triple-stacked detector. As shown in FIG. 4, incident X-ray beam 401 passes through two low energy detectors, LE1 405 and LE2 410, prior to passing through a high energy detector HE 415. Each detector may be formed from a range of X-ray detection materials such as a scintillator (which converts X-ray energy to optical radiation), a semiconductor (which converts X-ray energy to conduction band electrons) or a gas ionization detector (which converts X-ray energy to electron-ion pairs). In one embodiment, the detector configuration described with respect to FIG. 4 is employed with a 1 to 2 MeV system, where the beam energy is above 450 kVp. In one embodiment, first detector LE1 405 is capable of measuring an energy component of X-rays transmitted through the object in the range of 0 to 50 keV. In one embodiment, second detector LE2 410 is capable of measuring an energy component of X-rays transmitted through the object in the range of 20 to 200 keV. In one embodiment, third detector HE 415, is capable of measuring an energy component of X-rays transmitted through the object in the range of 100 keV to 2 MeV.
In each case, signals from each detector element are passed to integrator circuits, as shown in FIG. 5. In this embodiment, but not limited to such embodiment, a scintillation detector is employed in which an electrical signal generated in a photodiode is converted to a digital value which is directly proportional to the detected X-ray intensity. Independent scintillator/photodiode/integrator circuits are used for each of the three detector elements 405, 410, and 415, shown in FIG. 4.
Referring back to FIG. 5, in operation, integrator 500 is set with switches 505, 510, and 515 in an open position. Just prior to X-ray exposure, switch 505 is closed and integration starts. At the end of the exposure, switch 505 is opened and the stored charge is held on the capacitor. When the analog to digital converter (ADC) is available, switch 515 is closed, and the stored signal is converted to a digital value. At the end of conversion, switch 515 is opened again and switch 510 is closed. This resets the integrator 500 so that it is ready for the next acquisition cycle.
The obtained digital sensor values may then be analyzed, using the above described processor, as shown in FIGS. 6 a and 6 b. In FIG. 6 a, the difference 605 between the two low energy sensors LE1 and LE2, is analyzed as a function of transmitted X-ray beam intensity 610. At both significantly low and significantly high attenuation regions, where there is either no information or where the object is thick and there is no transmission, respectively, the difference between the two sensors is small, but at intermediate intensities, the difference increases to yield material-specific dependence. Two or more thresholds as a function of intensity can be derived to allow materials to be segmented, for example, into organic (Low-Z) and inorganic (High-Z) types, 615 and 620, respectively. Since this method relies on differential absorption of X-rays through the photoelectric effect, the technique does not provide a significant discrimination result at attenuation equivalent to a steel thickness of more than about 20 mm for an energy of about 180 keV or 40 mm for an energy of about 1 MeV.
As shown in FIG. 6 b, using the processor to determine the ratio of Compton to photoelectric signals provides materials discrimination over a wider range of object attenuations and is suited to operation at larger material thicknesses. Thus in FIG. 6 b, the difference 635 between the high energy sensor HE and the sum of the two low energy sensors LE1 and LE2 [i.e, HE−(LE1+LE2) is analyzed as a function of transmitted X-ray beam intensity 640. Combining the two effects provides a significant improvement over using just two low energy sensors (LE1 and LE2) or a single low energy (LE1 or LE2) and a single high energy (HE) sensor.
Using the separately obtained X-ray backscattering signals, an alternate materials analysis can be performed. Here, the Compton interaction of an X-ray with an electron results in incoherent scattering in which the scattered X-ray has less energy than the incident X-ray. The ability of a material to scatter is dominated by its atomic number (which is roughly proportional to density for solid materials)—the higher the density or atomic number the better it is at scattering. However, dense materials are also very good at absorbing X-rays compared to low density materials. For this reason, low density materials tend to result in a stronger backscattering signal than high density materials. Such a backscatter signal can be used advantageously in a security inspection process.
FIG. 7 is an illustration of one embodiment of a sensor that is capable of collecting backscattered radiation information and generating a backscatter image of a region. X-ray source 705 generates a thin pencil beam of radiation which, from within the base platform, sweeps rapidly from left to right over the two detector regions 710. The X-ray beam sweeps across the field of view of the object to be inspected typically in a time period of much less than a second and generally ranging from 5 ms to 100 ms. As the beam sweeps across the object under inspection the X-ray backscatter detectors 710 receive scattered signal from the adjacent interaction point of the primary X-ray beam with the object under inspection. The strength of the backscattered signal is dependent on the density at that region of the object. By temporal synchronisation readout of the detector element with the position of the primary beam location, a one-dimensional backscatter image can be obtained. Knowing the speed at which the vehicle moves past the sensor allows a two-dimensional image to be recreated from the set of one-dimensional image sections.
In one embodiment, the detectors are advantageously formed using a large area scintillation detector where the X-ray generated light is reflected into a large area photo-sensor such as a photomultiplier tube. An alternative embodiment may comprise a gas ionization chamber with a drift field to speed up collection of ion and electron signal currents.
FIG. 8 is a representative cross-section of an X-ray source that may be used with the present invention. Radiation source 800, with an extended anode 805, is shown whereby anode 805 operates at ground potential with a cathode 810 at a negative high voltage. It will be apparent to one skilled in the art that alternative configurations with a grounded cathode and differential systems with a cathode at negative potential and anode at positive potential are also possible. The X-ray source is shielded by suitable materials, such as tungsten and lead, to prevent unwanted radiation from the X-ray tube from reaching the object under inspection.
An electric motor 815 and a gearbox 820 drive a collimator 825 which comprises a solid block of tungsten or a combined tungsten/lead/steel assembly forming one or more predetermined voids, spaces, or holes 830 which allow radiation to be emitted in a pencil-beam fashion in a direction perpendicular to the axis of rotation of the collimator 825. Two such collimator holes 830 are shown diametrically opposed in FIG. 8. A high voltage connection 840 provides a point for electrical connection to the X-ray tube such that the high voltage power supply can be mounted remotely away from the X-ray inspection area.
While in operation, the axis of rotation of the collimator is in the direction of motion of the object under inspection such that the primary X-ray beam sweeps in a direction perpendicular to the motion of the object under inspection. As shown in FIG. 9, the X-ray beam 905 emerges from the source assembly 906 in a first direction and, at the point of intersection 907 of the primary beam 905 with the object to be inspected 910, generates backscattered radiation 912, which interacts with the adjacent X-ray detector 915.
As described above, the intensity of the primary beam averaged over an area is dependent upon the distance of that measurement point from the source origin. For this reason, the signal received at the periphery of the scanning zone will be less intense than that received nearer to the center of the inspection zone for an identical scattering surface. To address this issue, as shown in FIG. 10 a, in one embodiment of the present invention, the pencil-like rotating collimator section is replaced with a slot-like rotating collimator section 1005. A second collimation aperture 1010 is then placed adjacent to the rotating collimator and parallel to the inspection surface. The secondary collimator 1010 is narrow at the center of the inspection area 1015 (directly above the rotating slot collimator 1005) and widens out at distance from the rotating slot collimator. This provides a small irradiation area 1020 in the centre of the inspection region where the primary beam intensity is high and a larger irradiation at the periphery of the inspection region where the primary beam intensity is lower. This preserves the dynamic range of the signal and makes it easier to both collect the data with good signal to noise ratio and to reconstruct the individual scan line object density.
Accordingly, As shown in FIG. 10 b, it is preferred to activate a pulsed X-ray source at time T1-N 1030 to generate a corresponding line of the transmission X-ray image when the collimator is not emitting a backscatter beam onto the object, shown as times T′1-N 1040, thereby avoiding interference with the backscatter detector. In one embodiment, for an X-ray source pulsing at 100 Hz, the backscatter imaging collimator needs to operate at 50 revolutions per second or 300 RPM. By placing a phase lock loop or equivalent feedback circuit between the collimator motor controller and the X-ray transmission source controller, it is possible to adjust the frequency of the collimator and X-ray source to take into account variation in speed of the object under inspection as it passes through the X-ray imaging system.
As shown in FIGS. 11 a, 11 b, 11 c, and 11 d, in another embodiment of the present invention, the mechanical scanning assembly may optionally be integrated with a trailer to permit towing of the equipment behind a vehicle. FIG. 11 a shows system 1105 a in a first configuration, deployed and ready for use where the transport trailer 1110 a is folded up at the side of the inspection system and vehicle ramps 1115 a are in an open and ready to be drive-over position. When it is time to stow the equipment, the detector arrays are folded down and the vehicle ramps 1115 b are folded up, as shown in FIG. 11 b such that the system is in a second configuration. As shown in FIG. 11 c, in a third configuration, the trailer 1110 c is lowered, lifting up one end of the imaging equipment 1120 c. As shown in FIG. 11 d, a winch or other mechanism is then used to pull the X-ray system 1105 d onto the trailer ready for transport, in a fourth configuration. To deploy the system, the above described process is implemented in reverse. Advantageously, the vehicle which is used to tow the trailer is provided with image inspection computers, which one or more operators can use to analyze images and so divert and stop vehicles for further search as required and which comprises the aforementioned memory and processors used to process incoming backscatter and transmission data signals.
FIG. 12 depicts another embodiment of the present invention in which a four-sided backscatter detector 1205 is mounted around the periphery of the scanning tunnel. Each panel of the detector is similar to the sensor described with reference to FIGS. 7, 8, 9, and 10 a, but now a four-sided backscatter image may also be generated. Advantageously, the backscatter detectors are mounted to the same frame as the transmission X-ray system such that simultaneous transmission and backscatter image data can be acquired. This allows overlay of backscatter and transmission X-ray images by suitable image manipulation. In this embodiment, backscatter detectors, and not a backscatter X-ray source, are integrated into one or more of the first side 106, second side 107, and top side 108. Alternatively, backscatter detectors, and not a backscatter X-ray source, may be integrated into all three of the first side 106, second side 107, and top side 108. Alternatively, backscatter detectors with a backscatter X-ray source may be integrated into one or more of the first side 106, second side 107, and top side 108.
FIGS. 13 a, 13 b, and 13 c depict other embodiments of the X-ray system of the present invention with alternate transmission X-ray imaging geometries. FIG. 13 a shows the X-ray source 1305 a in a “down-shooter” configuration, while FIG. 13 b shows a combination or dual-view system that includes both “down-shooter” 1305 b and “side-shooter” 1310 b. FIG. 13 c shows a dual-view system, with both down-shooter 1305 c and side-shooter 1310 c, further comprising a four-sided backscatter system, with a backscatter source and backscatter detectors integrated into the base of the system 1320 c and backscatter detectors, together with transmission detectors, integrated into each of the remaining three sides 1325 c. It should be evident to those of ordinary skill in the art that other configurations can be derived based on this disclosure.
FIG. 14 is an illustration of one embodiment of the present invention where the system further comprises at least one, and preferably a combination of two, vehicle presence detection sensors 1405 and 1410, to the right and left, respectively, of the main gantry 1401. Sensor 1405 is used to turn the X-ray beam on when the vehicle approaches. This is the right-most sensor when the vehicle approaches from the right as shown in the diagram. Sensor 1410 (the left most sensor in the diagram) is used to turn the X-ray beam off once the vehicle has passed through the imaging plane. In one embodiment, an additional sensor may be used to measure the speed of the vehicle as it passes through the sensor. Vehicle speed may be used to modulate the speed of collimator rotation and source pulse rate to ensure that good image quality is maintained independent of vehicle speed. This also allows a constant dose per unit length of the vehicle under inspection to be delivered which helps to ensure a known and safe dose to the driver and other occupants of the vehicle during X-ray screening.
FIG. 15 shows a composite image which overlays the X-ray backscatter signal 1505 from the underside of the vehicle under inspection to be correlated with an optical image 1510 of the same vehicle that is acquired using a suitable optical system at the same time the X-ray image is acquired.
FIG. 16 shows an exemplary mechanism by which the optical image can be generated by taking an image signal from a mirror 1605 which rotates with the X-ray collimator through one or more optical filters 1610 to one or more photo detectors 1615. This configuration ensures the optical image is captured at a known time relative to the generation of a transmission image.
a second X-ray source disposed within the ramp of said portal for generating an X-ray beam towards the underside of the vehicle;
a second set of detectors disposed within the ramp of said portal for receiving X-rays that are backscattered from the vehicle; and
a controller, wherein said controller is adapted to activate the first X-ray source only when the second X-ray source is inactive.
4. The system of claim 1, wherein said system is collapsible.
5. The system of claim 4, wherein said ramp comprises a base platform hinged to a first angled surface and a second angled surface and wherein, when said system is collapsed, the first angled surface and second angled surface are rotated upward.
6. The system of claim 1, wherein said top horizontal side is connected to said first vertical side at a first end and to said second vertical side at a second end and wherein the first X-ray source is disposed at a point mid way between said first end and said second end.
7. The system of claim 1 further comprising backscatter detectors in at least one of said first vertical side, said second vertical side, and said top horizontal side.
8. The system of claim 7 wherein a backscatter X-ray source is not disposed with said backscatter detectors in at least one of said first vertical side, said second vertical side, and said top horizontal side.
9. A scanning system for the inspection of cargo, comprising:
a second set of detectors disposed within the ramp of said portal for receiving X-rays that are backscattered from the vehicle;
a primary rotating collimator placed adjacent to said first X-ray source, and
a secondary static collimator placed adjacent to said rotating collimator and parallel to the inspection surface, wherein said secondary collimator is adapted to generate a first irradiation area in the center of the inspection area and a second irradiation area at a periphery of the inspection area and wherein said second irradiation area is larger than the first irradiation area.
10. A method for inspecting a vehicle, comprising:
irradiating a vehicle with X-rays from a first source disposed on one side of the portal,
detecting the X-rays transmitted through the vehicle, using transmission detectors disposed within the portal, to produce a first output signal representative of the vehicle and contents thereof,
irradiating the underside of the vehicle with X-rays from a second source disposed within the ramp,
detecting X-rays scattered back from the vehicle, using backscatter detectors disposed within the ramp, to produce a second output signal representative of the vehicle and contents thereof, and
11. The method of claim 10, wherein said first X-ray source is a high energy source having an energy ranging from 100 kVp to 2 MV.
12. The method of claim 10, wherein said second X-ray source is a low energy source having an energy ranging from 60 kVp to 250 kVp.
13. The method of claim 10, wherein said first X-ray source is operated when said second X-ray source is inactive.
14. A scanning system for inspecting a vehicle, comprising:
15. The system of claim 14, wherein said first set of detectors is disposed on at least two of the same sides of the portal as the second set of detectors.
16. The system of claim 14, wherein said first set of detectors comprises a first detector and a second detector adapted to measure an energy component of X-rays transmitted through the vehicle in a range of 0 keV to 50 keV and 20 keV to 200 keV, respectively, and a third detector to measure an energy component of X-rays transmitted through the vehicle in a range of 100 keV to 2 MeV.
17. The system of claim 16, wherein said three detectors are in a stacked configuration.
18. The system of claim 16, wherein a difference between an output of the third detector and a sum of outputs of the first and second detectors is used to achieve material discrimination.
19. The system of claim 14 further comprising a sensor to measure a speed of the vehicle as it passes through the portal.
20. The system of claim 19, further comprising a controller wherein said controller is in data communication with the sensor and receives the speed of vehicle and wherein said controller is adapted to modulate a pulse rate of the X-ray source to attain a substantially constant dose per unit length of the vehicle under inspection based on the speed.
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PCT/GB2008/002897 WO2009027667A2 (en) 2007-08-31 2008-08-29 Scanning systems for security and medical scanners having means to control the radiation source
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US12/395,760 US7876880B2 (en) 2002-07-23 2009-03-02 Single boom cargo scanning system
US12/753,976 US7995705B2 (en) 2002-07-23 2010-04-05 Self-contained mobile inspection system and method
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PCT/GB2008/002897 Continuation-In-Part WO2009027667A2 (en) 2007-08-31 2008-08-29 Scanning systems for security and medical scanners having means to control the radiation source
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US20110064192A1 US20110064192A1 (en) 2011-03-17
US8503605B2 true US8503605B2 (en) 2013-08-06
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MORTON, EDWARD JAMES;KOTOWSKI, ANDREAS F;SIGNING DATES FROM 20101007 TO 20110310;REEL/FRAME:025985/0718