Patent Application
20100277312
Embodiments of the invention relate generally to contraband detection systems and, more particularly, to a method and apparatus for detecting contraband using combined imaging technologies.
In recent years, the detection of contraband, such as explosives, being transported in luggage and taken onto various means of transportation has become increasingly important. To meet the increased need for such detection, advanced Explosives Detection Systems (EDSs) have been developed that can not only detect suspicious articles being carried in the luggage but can also determine whether or not the articles contain explosive materials.
These detection systems, at a minimum, include computed tomography (CT) machines that are capable of acquiring mass and density information (as well as materials specific information, such as an effective atomic number) on items within luggage. Although object density is an important quantity, surrogates such as “CT number” or “CT value” which represent a linear transformation of the density data may be used as the quantity indicative of a threat. Although density is described in the embodiments below, all quantities are applicable and can be used interchangeably. Moreover, the features such as mass, density, and effective atomic number embody derived quantities such as statistical moments, texture, etc. of such quantities. To acquire more detailed and highly selective information on luggage being scanned, explosives detection devices based on other technologies such as quadrupole resonance (QR), trace detection, or x-ray diffraction (XRD) can be employed in combination with the CT system. These devices provide complementary information relative to the data from the CT system, thereby improving the overall detection performance of the EDS. That is, the complementary information gained from the systems and detection techniques ancillary to CT can provide higher detection sensitivity with reduced false alarms as compared to CT data alone, thus resulting in less manual or follow-on inspection needed to clear the alarms and preventing inspection system backup. Collectively, multiple technologies are required to satisfy (at the very least) minimum detection requirements for the whole range of explosives as specified by the Transportation Security Administration (TSA). Typically, the explosives detection devices are manufactured as stand-alone units, which are connected by the baggage handling system within an airport; the information provided by each system may or may not be combined optimally for overall threat assessment.
While existing EDSs that combine various scanning and detection technologies have been adequate to date, challenging requirements exist for future generations of explosives detection systems for baggage. Increases in the number of traveling passengers, increasing variance in explosive materials, and possible modifications to the concept of operations due to emerging threats will increase the demand for EDSs with improved throughput to accommodate the increased volume of baggage and require more sensitive/specific means for explosives detection. Moreover, next generation explosives detection systems will be required to meet threat detection standards commensurate with the Transportation Security Administration's current and future requirements (e.g., the TSA 2010 requirements), which may include, for example, single digit false alarm rates, throughput of at least 1000 bags per hour, ease of integration of new systems into the baggage handling system, and 99.5% availability.
To meet future TSA mandated detections standards, EDSs will require improved imaging performance and the combination of data from multiple sensors. The combination of presently employed third-generation CT scanners with technologies such as XRD, for example, can meet such standards; however, existing combinations of these technologies cannot meet the increased throughput rates that will be required. That is, typically, the CT system and the XRD system are stand-alone systems, which limits combined throughput capability of baggage scanning. Since the XRD system is typically located separate from the CT system, the XRD system requires an integrated pre-screener to acquire radiographic data that facilitates registration of a particular baggage item to previously acquired CT data. Registration of the baggage item with respect to previously acquired CT data allows for proper identification of suspected threat positions (i.e., regions of interest (ROIs)) in the baggage item, which is needed for XRD interrogation. Once the baggage item has been registered and the ROIs identified, the baggage item is moved into the XRD system and the x-ray source and collimator/detector arrangement in the system are mechanically positioned to direct x-rays that traverse the ROIs. While the above procedure allows for increased accuracy in XRD scanning, such registration and identification of the suspected threat position, along with the mechanical positioning of the x-ray source and collimator/detector arrangement in the XRD system, can lead to increased scanning time and greatly reduce baggage scanning rates.
Therefore, it would be desirable to design an apparatus and method for increasing throughput in an EDS while maintaining explosives detection at high sensitivity and simultaneously at low false alarm rates. It would also be desirable to have increased efficiency in identifying regions of interest in the baggage via CT data that represent a small fraction of the total baggage area and to control a follow-up imaging system where this ROI can be interrogated by highly selective follow-up imaging techniques with minimum adjustments or maintenance thereto.
Embodiments of the invention are directed to a method and apparatus for contraband detection that overcome the aforementioned challenges. A contraband detection system is disclosed that includes a first contraband detection apparatus positioned in-line with a second contraband detection apparatus and integrated therewith to increase scanning throughput capability for baggage or other objects of interest. Regions of interest (ROIs) in the baggage are identified by the first contraband detection apparatus and information on the ROIs is sent to the second contraband detection apparatus to facilitate subsequent scanning instructions thereto. The ROIs may be comprised of specific points in the baggage item or include the entire baggage item.
According to an aspect of the invention, a contraband detection system includes a first contraband detection apparatus to perform a first scan on an object and a second contraband detection apparatus positioned in-line with the first contraband detection apparatus to receive the object after passing through the first contraband detection apparatus and perform a second scan on the object. The contraband detection system also includes a computer connected to the first and second detection apparatuses programmed to cause the first contraband detection apparatus to perform the first scan, acquire object data from the first scan, and identify one or more regions of interest (ROI) in the object based on the object data, the one or more ROIs comprising one of a portion of the object or the entire object. The computer is further programmed to cause the second contraband detection apparatus to perform the second scan on the one or more identified ROIs, and acquire object data from the second scan.
According to another aspect of the invention, a method for detecting contraband includes the steps of performing a first scan on an object in a first scanning system to acquire a first set of data and identifying at least one region of interest (ROI) in the object based on the acquired first set of data, the at least one ROI comprising one of a portion of the object or the entire object. The method also includes the steps of passing the object to a second scanning system positioned in-line with the first scanning system and performing a second scan on the object to acquire a second set of complementary data, the second scan comprising the at least one ROI.
According to yet another aspect of the invention, an integrated imaging system for detecting contraband includes a first scanning system designed to convey and scan a baggage item to acquire scan data and a second scanning system positioned in-line with the first scanning system to receive the baggage item therefrom and designed to scan the baggage item to acquire complementary scan data. The integrated imaging system for detecting contraband also includes a processing unit connected to the first and second scanning systems programmed to cause the first scanning system to scan the baggage item to acquire the scan data, identify one or more regions of interest (ROI) in the baggage item based on the received scan data, and generate a desired scanning pattern for the second scanning system for the one or more identified ROIs. The processing unit is further programmed to cause the second scanning system to scan the baggage item using the desired scanning pattern to acquire the complementary scan data.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
Referring to
A conveyor system 22 is also provided and includes a conveyor belt 24 supported by a structure 26 to automatically and continuously pass packages or baggage pieces 20 through passageways extending through both the first and second scanner systems 16, 18 such that a throughput of baggage items 20 for scanning in first scanner system 16 and second scanner system 18 is provided. Baggage items 20 are fed through first and second scanner systems 16, 18 by conveyor belt 24 while imaging data is acquired, and the conveyor belt 24 moves the baggage items 20 through the scanners 16, 18 in a controlled and continuous manner. As a result, postal inspectors, baggage handlers, and other security personnel may non-invasively inspect the contents of baggage 20 for explosives, knives, guns, narcotics, contraband, etc. Conveyor belt 24 passes baggage items 20 in a manner that preserves the relative position of baggage item 20 and contents therein, such that second scanner system 18 examines locations within baggage items 20 at a coordinate location identified/flagged by first scanner system 16, as explained in detail below.
Referring still to
In one embodiment, and as shown and described in detail herebelow, first scanner system of EDS 10 can comprise a CT scanner 16 and second scanner system of EDS 10 can comprise an XRD scanner 18; however, it is envisioned that other embodiments of EDS 10 may incorporate additional types of contraband/explosives detection apparatuses, such as a quadrupole resonance scanner, trace detection system, or other contraband scanner. Additionally, while CT scanner 16 of the EDS 10 is described here below as a “third generation” CT system, it will be appreciated by those skilled in the art that the embodiments of the invention are equally applicable with other CT systems, such as those that may incorporate stationary and/or distributed x-ray sources.
Referring now to
During a scan to acquire x-ray projection data, gantry 34 and the components mounted thereon rotate about a center of rotation 46. The projection data corresponds to processed x-ray intensity measurements to represent line integrals of linear attenuation coefficient within the scanned items 20, which is well-known in the art. Rotation of gantry 34 and the operation of x-ray source 36 are governed by a control mechanism 48 of CT system 16. Control mechanism 48 includes an x-ray controller 50 that provides power and timing signals to an x-ray source 36 and a gantry motor controller 52 that controls the rotational speed and position of gantry 34. An image reconstructor 54 receives sampled and digitized x-ray data from DAS 44 and performs high-speed reconstruction thereon to output “CT data.” The CT data, in the form of reconstructed images, is applied as an input to a computer 56, which stores the images in a mass storage device 58.
As image reconstructor 54 and computer 56 are incrementally reconstructing “slices” of CT data by any of a number of mathematical algorithms and techniques (e.g., conventional filtered back-projection techniques), 2-D segmentation is also being performed on each of the reconstructed slices by computer 56. A 2-D image segmentation technique, such as edge detection, watershed segmentation, level sets, or another known segmentation method, is applied to each reconstructed image slice to identify regions in the slice that may be indicative of the presence of an explosive material. That is, each image slice reconstructed from the CT data represents the mass and density characteristics of that “slice” of the baggage item 20. Regions of interest (ROI) 59 (shown in
Computer 56 also receives commands and scanning parameters from an operator via console 60 that has some form of operator interface, such as a keyboard, mouse, voice activated controller, or any other suitable input apparatus. An associated display 62 allows the operator to observe the reconstructed image and other data from computer 56. The operator-supplied commands and parameters are used by computer 56 to provide control signals and information to DAS 44, x-ray controller 50 and gantry motor controller 52. In addition, computer 56 can operate a conveyor belt motor controller 63 which controls conveyor belt 24 to position and pass baggage items 20 in and through gantry 34. As set forth above, computer 56 can be specific to CT system 16 or can be embodied as computer subsystem 14 of the EDS 10 shown in
It is also envisioned that CT scanner 16 may comprise an energy sensitive (ES), multi-energy (ME), and/or dual-energy (DE) CT imaging system. An ESCT imaging system, by providing energy-sensitive detection of x-rays, acquires sufficient information to determine material specific properties of items within baggage 20 by way of a determination of the effective atomic number of materials present in the baggage. In one embodiment, detectors 42 are designed to directly convert x-ray energy to electrical signals containing energy discriminatory or photon count data. That is, detectors 42 detect each x-ray photon reaching each detector 42, and DAS 44 records the photon energy according to energy deposition in the detector. The detectors 42 are therefore composed of a material capable of the direct conversion of x-ray energy, such as Cadmium Zinc Telluride (CZT) or another suitable material, to provide such energy discrimination capability.
In another embodiment of an ESCT imaging system, x-ray controller 50 functions to vary the operating voltage of x-ray source 36 to provide energy discriminating capability to CT system 16. That is, x-ray controller 50 is configured to control a generator (not shown) to apply different peak kilovoltage (kVp) levels to x-ray source 36, which changes the peak energy and spectrum of the incident photons comprising the emitted x-ray beams 38. Thus, CT system 16 may acquire projections sequentially at varying energy levels. The detected signals from the two energy levels, generally characterized as high and low, provide sufficient information to determine the material specific properties of items within baggage item 20 by way of the determination of the effective atomic number of those items. Although two specific embodiments of energy sensitive CT systems are provided, any suitable method for acquired energy sensitive projection data and subsequent identification of the effective atomic number distribution within baggage item 20 are suitable substitutes.
It is envisioned that additional aspects of CT system 16 can be modified within the scope of the invention to accommodate increased throughput rates of baggage 20 through the scanner. For example, detectors 42 can be modified to increase the number of rows of detector elements/pixels in each detector, thus increasing the coverage per gantry rotation for each baggage scan. Additionally, the rotational speed of gantry 34 can be varied (i.e., increased) to allow for a higher throughput of baggage items 20 through CT system 16.
Referring now to
To control operation of distributed x-ray source 66 and detector 68, the XRD system 18 includes a radiation source controller 70 and a data acquisition controller 72, which may both function under the direction of a computer 74. As set forth above, computer 74 can be specific to XRD system 18 or can be embodied as computer subsystem 14 of the EDS 10 shown in
The x-rays 76 sent from the distributed x-ray source 66 pass through one or more ROIs 59 in baggage item 20, are diffracted by the specific material present in the ROI 59, and are directed onto the detector 68, which measures the coherent scatter spectra of the x-rays after passing through the ROI 59 to acquire “XRD data.” The coherent scatter spectra of the x-rays may then be processed and compared to a library of known reference spectra for various dangerous substances (i.e., explosives) that can be stored on computer 74. As such, a signature for the molecular structure of a material in the ROI 59 can be analyzed and a determination made to discern if that structure corresponds to a known explosive material. Many such measurements may be collected in an examination sequence, and data acquisition controller 72, which is coupled to detector 68, receives signals from the detector 68 and processes the signals, thus acquiring the XRD data.
Computer 74 generally regulates the operation of the radiation source controller 70 and the data acquisition controller 72. The computer 74 may thus cause radiation source controller 70 to trigger emission of x-ray radiation 76, as well as to coordinate such emissions during imaging sequences defined by the computer 74. The computer 74 also receives data acquired by data acquisition controller 72 and coordinates storage and processing of the data. An operator interface 81 may be integral with the computer 74 and will generally include an operator workstation for initiating imaging sequences, controlling such sequences, and manipulating data acquired during imaging sequences, which can be stored in a memory device 83. Operator interface 81 of XRD system 18 may be combined with the operator console of the CT system 16 (
Referring now to
A number of configurations for emitters 80 and/or distributed sources 66 are envisioned. In one embodiment, for example, distributed x-ray source 66 comprises a cold cathode field emitter array that is positioned apart from a stationary anode. As shown in
Referring still to
In one embodiment, detectors 68 are also configured for energy resolution less than 3% at an x-ray photon energy of 60 keV and can be energy sensitive detectors comprised of high-purity germanium, CZT, or other suitable energy sensitive detector technology. Collimators 96 provide the coding of the constant angle diffraction signal resulting from the interaction of the x-ray beam with the baggage 20, allowing measurement of a diffraction signal from a particular region of interest.
As described above, cathode modules 79, and corresponding emitters 80, within distributed x-ray source 66 are independently and individually addressable so that radiation can be triggered from each of the source locations 78 at points in time as needed. The triggering of a particular cathode module 79 and its emitters 80 is determined by the one or more ROIs 59 identified in the baggage item 20 via the CT scanner 16. As set forth above, the ROIs 59 are identified by way of an analysis of the CT data (e.g., 2D segmentation or limited 3D segmentation of reconstructed data) and the mass, density, and/or effective atomic number characteristics in the CT data that may be indicative of an explosive material. These identified ROI(s) 59 within the baggage item 20 is/are then mapped to determine where the ROI 59 lie within the field-of-view 93 of the CT system 16 and XRD system 18.
In selecting activation of a desired emitter 80 at a source location 78 in distributed x-ray source 66, data related to the location of the ROI 59 within the field-of-view 93 are sent to computer 74 (shown in
While described above as being individually or sequentially activated, in other configurations, the emitters 80 are addressable in logical groups. For example, pairs or triplets of emitters 80 may be logically “wired” together. Where desired, and as determined by the identified ROI 59, more than one such group of emitters 80 may be triggered concurrently at any instant in time.
Based on the acquired CT data (mass, density, and/or effective atomic number) and XRD data (spectral signature indicative of the molecular structure, noted as “molecular signature), a “Threat Status” for one or more ROI 59 in a particular piece of baggage 20 can be generated. That is, a determination can be made of the probability and/or likelihood of an explosive material being present in the baggage item 20. Toward this end, computer subsystem 14 (shown in
In combining the mass, density, effective atomic number, and molecular signature characteristics obtained in the CT data and XRD data for an identified ROI, a Bayesian Data Fusion Protocol, employing Bayes' law, can be implemented. That is, the risk calculus and determination of a probability/likelihood of contraband/explosives may be characterized by Bayesian probability theory wherein the initial risk values are probabilities of the presence of each type of contraband based on a first type of scan. The probabilities are modified using Bayes' rule, with the initial risk values of the first scan being applied to and combined with risk values ascertained from scanning results of a second type of scan, to output a final risk value that is the combination of probabilities for the given types of contraband/explosives based on the combination of scans. The combination of probabilities, and corresponding final risk value, are output as the Threat Status. Although not described herein, statistical techniques other than those based on Bayesian statistics are contemplated as being useful for combining the data from multiple scanning devices.
Referring now to
The conveyor belt 24 then moves the baggage item 20 into the XRD scanner 18, which scans any ROI in the baggage item 20, as described in detail above. As illustrated in
The computer 30 reads the final threat state 106 and, if the total probability of any type of contraband being in the baggage item 20 is above the critical probability for any particular threat category, the computer 30 triggers an alarm to alert an operator of the EDS 10 of the likely presence of contraband/explosives. The alarm could be one of a visual alarm displayed on computer 30, an audio alarm, or a means for extracting the suspect baggage item from the normal stream of baggage.
While the above contraband detection system is described as being comprised of first and second contraband detection apparatuses, it is further contemplated that additional scanning devices can be included in the contraband detection system. That is, one or more additional scanning devices can be positioned in-line with the first and second contraband detection apparatuses, and complementary data therefrom can be further combined with the data acquired by the first and second contraband detection apparatuses and integrated therewith. Referring now to
The object data acquired by first, second, and third detection apparatuses 112, 114, 116 (and any additional scanning devices integrated into EDS 110) is assessed/combined by computer 118, as set forth in detail above with respect to
A technical contribution for the disclosed method and apparatus is that it provides for a computer implemented method and apparatus that increases throughput scanning capability for baggage or other objects of interest by identifying regions of interest in the baggage and providing scanning instructions to a stationary x-ray diffraction system.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Furthermore, while explosives detection techniques are discussed above, the invention encompasses other types of contraband, such as concealed weapons and narcotics. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
The present application is a non-provisional of, and claims priority to, U.S. Provisional Application Ser. No. 60/891,145, filed Feb. 22, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60891145 | Feb 2007 | US |
