Gantry scanner systems

A gantry scanner system includes a radiation source, a plurality of detectors and a support frame supporting the detectors. The support frame includes an elongate support member arranged to support the detectors, cable support means arranged to support power cables or signal cables connected to the detectors, and cover means arranged to cover the support member, the cable support means and the detectors.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage application of PCT/GB2009/001277, filed on May 20, 2009, which further relies on Great Britain Patent Application Number 0809110.0, filed on May 20, 2008, for priority.

FIELD OF THE INVENTION

The present invention relates to scanners and in particular to gantry scanner systems. It has particular application in cargo scanners, but can be used with scanners in other fields.

BACKGROUND

There is a requirement to screen cargo items for the detection of illicit materials and devices. Today, the use of X-ray imaging for cargo inspection is becoming more widespread. Such systems are typically made from large welded steel fabrications and are complex and time consuming to install.

SUMMARY OF THE INVENTION

The present invention provides a gantry scanner system comprising a radiation source, detection means which may comprise a plurality of detectors and a support frame supporting the detection means. The support frame may include an elongate support member arranged to support the detection means. The support frame may comprise cable support means arranged to support power cables or signal cables connected to the detectors. The support frame may comprise cover means arranged to cover the support member, the cable support means and the detectors.

The support frame may comprise a plurality of said support members connected together. The support frame may preferably comprise two of said support members connected together at right angles to each other to form a vertical side and a horizontal top of the frame, and a further vertical section connecting one of the support members to a radiation source module. The radiation source module and one of the support members may be movably supported by support means and guide means may be provided to guide the gantry to move along a pre-determined path.

The support member may be of a constant H-shaped cross-section along its length and may comprise a central web and two side sections. The detectors are preferably mounted within a cavity formed by the central web and the two side sections and radiation absorbing means are preferably mounted on an opposite side of the central web to the detectors.

Cable support means may be located on the outer side of at least one of the side sections of the elongate support members and may comprise a cable support tube or conduit mounted on the support section by means of a plurality of tube support brackets. Cover means may comprise a plurality of removable cover sections which can each be removed to allow access to the detectors. A control system and power storage means may be arranged to be connectable to a power supply so that it can be recharged.

The present invention further provides a gantry scanning system comprising a gantry, a radiation source, radiation detectors, a control system and rechargeable power storage means mounted on the gantry, wherein the power storage means is arranged to be connectable to a power supply so that it can be recharged. The system may further comprise guide means defining a path along which the gantry can move, wherein the power storage means are arranged to be connectable to the power supply only when it is in one or more recharging positions on the path. Recharging means are preferably provided at each end of the path so that the power storage means can be recharged in each of two recharging positions.

The control system is also preferably arranged to transmit scan data, obtained by the scanner, wirelessly to a remote station for analysis. The remote station may include display means arranged to display an image generated from the scan data. Further, the control system may be arranged to receive control instructions wirelessly from a remote control station.

DETAILED DESCRIPTION OF THE INVENTION

In the following embodiment of the present invention, a low cost X-ray imaging system is provided which is simple to install and rapid to commission.

A plurality of elongate support members are connected together to form a gantry system as shown inFIG. 1. The gantry1comprises two vertical elongate support members A and C which are connected at their top ends at right angles to a horizontal elongate support member B to form an arch. The bottom end of each of the vertical members A and C is connected to and supported on a bogey E, D. One of the vertical support members A supports a multiplicity of individual X-ray detection elements. In a preferred embodiment, the horizontal member B also contains a multiplicity of individual X-ray detection elements. The other vertical support member C provides a structural function, and the bogey D on which it is supported contains the X-ray source, its associated power supplies and control system. The bogeys D and E enable motion of the gantry. The motion of the two bogeys E and D is controlled, such that the bogeys E and D move simultaneously at the same speed and in the same direction to move members A, B and C along rails5.

In one embodiment, the imaging system is stationary and is operated as a portal. In this case there is no requirement to drive the imaging system backwards and forwards. In the embodiment shown, the imaging system is able to scan backwards and forwards under computer control around a stationary load under inspection. In another embodiment, the control system44in Section D is arranged to receive instructions from a remote station, thereby making the gantry1entirely wirelessly operated.

In the embodiment shown inFIG. 1, wheels6enable motion of the gantry and runners (not shown) located on the underside of bogeys D and E engage with rails5and allow movement of the gantry to keep the motion of the gantry uniform along the path defined by the rails5.

In an alternative embodiment, as shown inFIG. 2, small pneumatic wheels7are fitted to the underside of bogeys D and E that run on a level concrete floor. Mechanical guidance is achieved by a metal or plastic guide rail8which are fixed to the ground. In this example, a controlling system9receives feedback signals from a mechanical sensing arm4which is pivotally connected at one end to the bogey E and is engaged with the guide rail8at the other end so that it follows the guide rail8. The control system processes the feedback signals which are indicative of the angle of the sensing arm and outputs instructions to a motor speed control circuit which controls the speed of the wheels6to prevent “crabbing” of the system whereby the unit goes off track. Here, the leftmost actuator is out of line, indicating a crabbing possibility.

In another embodiment, guide means defining a path along which the gantry can move are provided in the form of painted lines on the ground which are tracked by a video camera mounted on the bogey. Alternatively, magnetic strips are used which are tracked by a magnetic sensor mounted on the bogey. In yet another embodiment, wheels on bogey Sections E and D engage with rails. Alternative drive schemes may also be appropriate and will be apparent to a person skilled in the art.

As shown inFIGS. 3 and 3a, the elongate support members A, B and C are fabricated from a metal girder10with an H-shaped cross-section, which comprises a central web10aand two side sections10b,10c. The girder10is intrinsically strong and of light weight and may be made of steel or aluminium. Alternatively a rigid composite material such as carbon fibre can be used. To provide further stiffness, an improved aerodynamic profile and weatherproofing, the girder10is enclosed by a skin12, which is moulded carbon fibre composite, moulded glass fibre composite or pressed steel sheet which is welded or glued in place. As can be seen fromFIG. 3, the skin surrounds part of the girder to form a generally rounded symmetric shape with one parallel section and two rounded ends. A long aperture13is formed in the outer skin12along the length of the support member to provide access to the detectors34.

Referring toFIG. 4, X-ray detectors34are fitted within a cavity formed between the side sections10b,10cextending from a side of the central web10aof the girder. A moulding31that would typically be formed separately to the outer skin12is affixed within the cavity on the side of the girder that is not covered by the outer skin. One or more detectors34are pre-assembled into each metal or moulded plastic trays30which are then mounted onto the moulding31by fixing to pre-installed threaded inserts32. It is advantageous to leave a gap36of uniform cross-section between the underside of the tray30and the moulding31filled with air in order to provide good thermal insulation of the detector components. It is also desirable to insert water absorbing materials, such as silica gel, into these spaces to provide longevity of the detectors34. Radiation absorbing means28, which may comprise a lead beam-stop, are mounted on the opposite side of the central web10ato the detectors34between the side sections10a,10b.

The elongate support members A, B, C include support for cables. Prior to attachment of the outer skin12, a series of thin steel support brackets14are welded to the girder10. As shown inFIG. 5, each support bracket is semi-circular shaped and is affixed to the sides of sections10band10cof the girder10. The brackets14are perforated with holes16that have metal or plastic cable support tubes18or conduits inserted through them. The tubes18extend the full length of the elongate support members and each provide support for either power or signal cables, but not a mixture of power and signal cables. Typically two or three cable tubes18may be fitted per bracket14.

With reference toFIG. 6, an end plate23is fitted to the end of the girder of each of the support members A, B and C. A series of joining plates20are welded at right angles directly to the girder10at the end of Sections A, B and C to provide bolted joining points. Advantageously the joining plates20include alignment fixings21to ensure accurate assembly of the system prior to tightening up of the main bolts.

A join between, for example, Sections A and B and between Sections B and C is weatherproofed as shown inFIG. 7. Here, the outer skin12at each end of the elongate support member is moulded such that it extends around the joining plate20and presents a large area flat face22which contacts with the equivalent end face of the other elongate support member when the system is assembled. One of the connecting faces is coated with a suitable adhesive, such as a silicone elastomer, prior to sealing with the other face. As shown inFIG. 8, a removable hatch24is provided in each elongate support section over the joint to allow access to the fixings21in the joining plates20and to allow routing of cables from the support brackets14in one of the support member A, B or C to those in the other. The removable hatch24is moulded to fit the curvature of the skin12. The moulded hatch24and the skin12into which it fits is of a re-entrant design to prevent water ingress. Waterproofing is achieved by using a compressed elastic plastic foam which provides the final seal between the hatch24and skin12. It is advantageous to use quick release fittings to fix the hatch24to the elongate support member to minimise repair and installation time. It is also advantageous to fill each of the sections between the outer skin12and the internal metal work with an expanded polyurethane foam or other suitable foam material in order to provide thermal insulation between the outer skin12and the components within the respective elongate support members A, B and C.

Weatherproof and light proof covers are required to protect the detectors34following installation. A re-entrant cover26, shown inFIG. 9a, is appropriate for this purpose. As shown inFIG. 9b, channels27are formed in the skin12of the support members at the edge of the aperture13. Fixtures25are located within the channels27and are arranged to receive the corresponding fixing29which projects down from the top surface26aof the cover, as shown inFIG. 9a. Quick release fixings are used to allow rapid access for installation and service.

It is advantageous to use several small covers which overlap, as shown inFIG. 10, to allow rapid removal of the covers when access is required for installation or service purposes because it is easier for service personnel to manoeuvre small covers. Each cover has a substantially flat top surface26awhich is exposed when fitted, and a substantially flat lower surface26b, spaced from the top surface by a vertical section26c. A rim26eprojects downwards from one end of the top surface at right angles and a rim26dprojects upwards from the lower surface at right angles to form a trough along one end of the cover. An elastic plastic foam38is mounted on the underside the rim of the cover which is compressed when the covers are fitted to prevent environmental ingress. To retain strength, the covers have an arcuate form as shown inFIG. 11. In another embodiment, the cover is hinged along its long edge from fixings that are located on the outside of the outer skin.

Referring toFIG. 12, bogey D is a cabinet that contains an X-ray linear accelerator40, an X-ray power supply42and control system44. The cabinet is manufactured using a welded steel framework46suitable for supporting the weight of the various components to be installed, and is fitted with weatherproof doors which can be locked shut using keys.

A drawback of many conventional gantry systems is that power and data is typically handled using cables passed through a cable management system such as a caterpillar track system or a cateenery (suspended cable) system. In a preferred embodiment, the power supply42includes an uninterruptible power supply50(UPS). The control system44controls and manages the UPS50. The UPS50is configured to receive mains power from docking stations48that are located at either end of the scanning region or guide path as shown inFIG. 12. While the gantry is adjacent to a docking station48at each of the two recharging positions, the control system is arranged to establish a connection between the UPS50and the docking station48, in order to allow the power storage means42to recharge via the UPS50. The gantry1is self powered while a scan is in progress and works successfully when the time that the system is scanning is less that the time that the system is charging. This is typically the case when individual cargo loads need to be positioned within the imaging zone prior to scanning. The UPS50operates to receive power to be recharged only when the power supply42is in one or more recharging positions on the path along which the gantry1moves.

The control system44stores and manages all imaging data relating to each scan and converts the imaging data associated with each scan to an Ethernet packet for transmission wirelessly to a local network access point or to a remote station for analysis. An image generated from the scan data is displayed on a monitor for inspection at the remote station.