Cargo container tomography scanning system

[0001] The present application claims priority from U.S. Provisional Patent Application Ser. No. 60/432,348 filed on Dec. 10, 2002, which is assigned to the assignee of the present application and incorporated herein by reference.

[0002] The present disclosure relates generally to X-ray scanning systems and, more particularly, to an X-ray baggage scanning system. Even more particularly, the present disclosure relates to an X-ray computed tomography scanning system adapted to scan air cargo containers or other larger containers for detection of explosives, drugs, and other contraband.

[0003] The U.S. Department of Homeland Security and the Transportation Security Administration and other similar agencies throughout the world have the daunting task of identifying dangerous devices and/or contraband within passenger baggage and within a time-frame that will not generally impede passenger travel time. Many X-ray baggage scanning systems in use today are of the “line scanner” type and include a stationary X-ray source, a stationary linear detector array, and a conveyor belt for transporting baggage between the source and detector array as the baggage passes through the scanner. The X-ray source generates a stationary X-ray beam that passes through and is partially attenuated by the baggage, as the baggage is moved into and positioned within the beam, before being received by the detector array. During each measuring interval, each detector of the detector array generates data representative of the integral of the density of the planar segment of the baggage through which the detected portion of the X-ray beam passes. The data acquired by the detector array during each measuring interval is used to form one or more raster lines of a two dimensional image. As the conveyor belt transports the baggage past the stationary source and detector array, the scanner generates a two dimensional image representative of the density of the baggage, as viewed by the stationary detector array. The density image is typically displayed for analysis by a human operator.

[0004] It has been suggested to use X-ray computed tomography (CT) as a part of a baggage scanner to identify objects within baggage positioned in the scanner. At least one of these designs, described in U.S. Pat. No. 5,182,764 (Peschmann et al.) and U.S. Pat. No. 5,367,552 (Peschmann et al.) (hereinafter the '764 and '552 patents), for example, has been commercially developed and are referred hereinafter as the “In Vision Machine”. The In Vision Machine includes a CT scanner of the third generation type. Third generation type CT scanners are particularly useful in the medical arts and are often used for imaging sections of the human body. Third generation scanners typically include an X-ray source and an X-ray detector system secured respectively to diametrically opposite sides of an annular-shaped gantry platform or disk. The gantry disk is rotatably mounted within a gantry support so that in operation the disk continuously rotates about a rotation axis while X-rays pass from the source through an object positioned within the opening of the disk to the detector system. During a scanning procedure, baggage passes along the rotation axis through the rotating gantry disk.

[0005] The EXACT™ AN6000, which is available from International Security Systems Corporation, which is a subsidiary of the assignee of the present disclosure, Analogic Corporation, is an advanced CT system for the detection of explosives, drugs, and other contraband in carry-on baggage. The EXACT™ AN6000 generates 3-D image data of all objects in a bag, gathers all data in one pass, allows automatic analysis of entire contents of bag, and can handle up to 600 bags per hour. Analogic's EXACT™ AN6000 is a dual energy, helical-cone-beam, multi-slice CT system that provides a complete set of CT images of an entire three-dimensional object as it passes along the baggage conveyor. The system includes a high efficiency, wide dynamic range, solid-state X-ray detector array consisting of 6048 detectors. Rotating at 90 RPM, this system takes up to 720 sets of 6048 measurements per rotation every two-thirds of a second. The system presents both projection and axial images of this moving object for analysis by the operator. The EXACT™ AN6000 CT system is covered by at least the following U.S. patents which are owned by Analogic Corporation: U.S. Pat. Nos. 5,661,774; 5,796,802; 5,818,897; 6,185,272; 6,188,745; and 6,418,189.

[0006] The EXACT™ AN6000 is the heart of the eXaminer 3DX™ 6000 Explosive Detection System (EDS), the first single-unit, second-generation CT system certified by the U.S. Federal Aviation Administration and developed in cooperation with L-3 Communications. The EXACT™ AN6000 is also the system of choice for detection of drugs and other contraband. Equipped by ISS with our own workstation and custom drug algorithms, the EXACT™ AN6000 has been successfully demonstrated to the U.S. Customs Service, detecting small quantities of contraband. Sophisticated software automatically isolates bag contents unambiguously and analyzes them, evaluating them against the known characteristics of explosives or narcotics. If a match is found, the system alerts the operator, highlights the area of concern for further analysis, and provides a full rotating 3-D image of the potential threat.

[0007] What is still desired is a system for detecting explosives, drugs, and other contraband in objects larger than a typical piece of carry-on luggage, such as an air cargo container containing a plurality of pieces of luggage. Preferably, the system will be an X-ray computed tomography scanning system adapted to scan air cargo containers or other larger containers for detection of explosives, drugs, and other contraband.

[0008] The present disclosure provides a new and improved X-ray computed tomography scanning system adapted to scan air cargo containers or other larger containers for detection of explosives, drugs, and other contraband. The system includes a table that rotates about an axis of rotation for supporting a cargo container, a first platform supporting an X-ray source thereon and movable parallel to the rotation axis of the table, and a second platform supporting an X-ray detector thereon and movable parallel to the rotation axis of the table.

[0009] During a scanning procedure, the table rotates the cargo container about the axis of rotation, while the first and the second platforms move parallel to the rotation axis of the table, and the X-ray source sends an X-ray beam through the cargo container to the X-ray detector. The container is completely scanned when the X-ray beam clears an end of the container, at which time the X-ray source shuts off. The scanned cargo container is then removed from the table, another cargo container is positioned on the table and the table is rotated. The first and the second platforms then move in an opposite direction parallel to the rotation axis of the table and the X-ray source and the X-ray detector are operated to scan the container.

[0010] Other features and advantages of the presently disclosed disclosure will become apparent by reference to the following description taken in connection with the accompanying drawings.

[0013] Like reference characters designate identical or corresponding components and units throughout the several views.

[0014] FIGS. 1 and 2 are perspective views of an exemplary embodiment of an X-ray computed tomography (CT) scanning system 10 constructed in accordance with the present disclosure and adapted to scan air cargo containers 100 or other large containers for detection of explosives, drugs, and other contraband. In FIGS. 1 and 2 a first cargo container 100 is shown being scanned, a second cargo container 100′ is shown prior to being scanned, and a person 102 is shown standing next to the system 10 to provide a size comparison. In addition, a top X-ray containment wall is shown removed. In FIG. 2, the scanning system 10 is shown with a front X-ray containment wall removed.

[0015] The system 10 of the present disclosure generally scans for the same items and provides the same results as the EXACT™ AN6000 CT system, which is available from International Security Systems Corporation, which is a subsidiary of the assignee of the present disclosure, Analogic Corporation. The system 10 of the present disclosure, however, is adapted to scan air cargo containers 100 or other large containers instead of just smaller carry-on baggage.

[0016] Like the EXACT™ AN6000, the system 10 of the present disclosure generates 3-D image data of all objects in a scanned container 100, gathers all data in one pass, and allows automatic analysis of entire contents of the container. The system 10 includes an X-ray source 12 and an X-ray detector 14. In one exemplary embodiment, the X-ray source 12 is a dual energy, helical-cone-beam, multi-slice CT system that provides a complete set of CT images of an entire three-dimensional object as it is scanned, and the X-ray detector 14 is a high efficiency, wide dynamic range, solid-state, two dimensional X-ray detector array.

[0017] The scanning system 10 also includes a rotating table 16 disposed within an X-ray containment enclosure 18. The table 16 is for supporting a cargo container 100 and rotates about a rotation axis 20. The table 16 is driven about the rotation axis 20 by a suitable drive assembly (not shown). A suitable drive assembly may comprise, for example, a pulley secured to the table 16, a drive belt connected to the pulley, and a motor for causing the drive belt to rotate the pulley and the table 16.

[0018] The X-ray source 12 and the detector array 14 are disposed on diametrically opposite sides of the table 16. A first platform 22 supports the X-ray source 12 and is movable parallel to the rotation axis 20 of the table 16. A second platform 24 supports the X-ray detector 14 and is also movable parallel to the rotation axis 20 of the table 16. In the exemplary embodiment shown, the rotation axis 20 of the table 16 extends in a vertical direction, and the first and the second platforms 22, 24 also move in vertical directions, i.e., up and down.

[0019] The first and the second platforms 22, 24 are controlled such that they move in a synchronized manner, with each other. Suitable drive mechanisms are used to raise and lower the first and the second platforms 22, 24. The drive mechanisms may, for example, comprise rotary motors driving vertically extending screws threaded through bearings secured to the platforms 22, 24, such that the motors turning the screws causes the platforms to be raise or lowered. In accordance with one exemplary embodiment, the first and the second platforms 22, 24 are controlled such that they move in a synchronized manner with each other and in synchronized manner with the rotating table 16. For example, the first and the second platforms 22, 24 are raised and lowered only when the table 16 is rotating.

[0020] During a scanning procedure, the table 16 rotates the cargo container 100 about the axis 20 of rotation, while the first and the second platforms 22, 24 move parallel to the rotation axis 20 of the table 16, and the X-ray source 12 sends an X-ray beam through the cargo container 100 to the X-ray detector 14 (i.e., perpendicular to the rotation axis 20 of the table 16 as shown in the exemplary embodiment of FIGS. 1 and 2). The X-ray beam starts passing through the cargo container 100 at a bottom end of the container 100, and the container 100 is completely scanned when the X-ray beam clears a top end of the container 100, at which time the X-ray source 12 shuts off.

[0021] The scanned cargo container 100 is then removed from the table 16, another cargo container 100′ is positioned on the table 16 and the table 16 is rotated. The first and the second platforms 22, 24 then move in an opposite direction (i.e., downward in the exemplary embodiment of FIGS. 1 and 2), parallel to the rotation axis 20 of the table 16 and the X-ray source 12 and the X-ray detector 14 are operated to scan the next container 100′. The system 10, therefore, is operated to scan the largest number of cargo containers in the shortest period of time in order to obtain a high throughput of cargo.

[0022] The system 10 also includes a conveyor for conveying cargo containers 100 onto and off the table 16. In the exemplary embodiment shown, the conveyer includes a plurality of individual conveyor sections including a motorized entrance conveyor 26, a motorized interim entrance conveyor 28, a motorized interim exit conveyor 30, and a motorized exit conveyor 32. In addition, the table 16 includes a motorized conveyor. The table 16 also includes locks, which are preferably automatically activated and deactivated, for securing the containers 100 thereon during scanning (the following U.S. patents show examples of latches for securing cargo containers in place: U.S. Pat. Nos. 3,810,534; 3,986,460; 4,089,275; 4,349,302; and 5,433,564).

[0023] The system 10 further includes a six-sided X-ray containment shield 18 (the top wall is shown removed in FIGS. 1 and 2, while a front wall is shown removed in FIG. 2) for preventing radiation from propagating beyond the shield. The shield 18 includes two sliding doors 34 for allowing passage of a cargo container into and out of the shield. Although not shown, the doors 34 can include motors for automatically opening and closing the doors 34 in synchronization with the first and the second platforms 22, 24, the table 16, the motorized conveyors 26, 28, 30, 32, and the cargo container locks. The X-ray containment shield 18 is configured to occupy as little area and volume as possible in order to reduce the foot print of the X-ray containment space.

[0024] Although not shown, the system 10 further includes a data acquisition system for receiving and processing signals generated by the detector array 14, and an X-ray tube control system for supplying power to, and otherwise controlling the operation of, the X-ray source 12. The X-ray tube control system can be, for example, a dual energy X-ray tube control system. The CT scanning system 10 is also preferably provided with a computer for processing the output of the data acquisition system and for generating the necessary signals for operating and controlling the system. The computer can include a CPU and a monitor, and may also include a processing center for respectively processing and displaying information including generated CT images.

[0025] In operation, the X-ray source 12 generates from its focal spot a pyramidically shaped beam, often referred to as a “cone” beam X-ray (shown in FIG. 1) that passes through a three dimensional imaging field, through which the cargo container 100 is positioned by the conveyor. After passing through the scanned section of the cargo container 100, the cone beam is received by the detector array 14, which in turn generates signals representative of physical attributes of portions of the cargo container 100 between the focal spot and the respective detector during the measuring interval. By way of example, one physical attribute can be the representative densities of portions of the cargo container 100 as determined as a function of the integral of the attenuation of the radiation beam passing through the container and any object therein. Where a dual energy power supply is utilized, the specific molecular weight of objects such as plastic explosives can be detected. Other physical attributes which may be detected will be evident to those skilled in the art. Thus, the scanning system 10 is not only useful for detecting plastic explosives, but the system can be used to detect other targeted objects, such as firearms and the like.

[0026] As the table 16 rotates the cargo container 100 between the X-ray source 12 and the X-ray detector 14, and the first and the second platforms 22, 24 are raised and lowered parallel to the axis 20 of rotation, a plurality of projections are generated at a corresponding plurality of projection angles with each 360° rotation of the table 16. In a well known manner, signals from the detector array 14 can be initially acquired by a data acquisition system, and subsequently processed by a computer.

[0027] The central processing unit that controls the X-ray source 12 and the X-ray detector 14 can also be used to control the motor of the table 16, and the motors of the first and the second platforms 22, 24, the motorized conveyors 26, 28, 30, 32, the motors of the doors 34 and the cargo container locks, and synchronize operation of the first and the second platforms 22, 24, the table 16, and the X-ray source 12 and the X-ray detector 14, the motorized conveyors 26, 28, 30, 32, the doors 34 and the cargo container locks.

[0028] It should be understood that the embodiments of the present disclosure described herein are merely exemplary and that a person skilled in the art may make variations and modifications to the embodiments described without departing from the spirit and scope of the present disclosures. Because certain changes may be made to the above-described apparatus 10 without departing from the spirit and scope of the present disclosure, all matter contained in the above description or shown in the accompanying drawings shall be interpreted in an illustrative and not a limiting sense. All such equivalent variations and modifications are intended to be included within the scope of this disclosure as defined by the appended claims.