HK1178978B - Cargo and vehicle inspection system - Google Patents

Description

Cargo and vehicle inspection system

Technical Field

The present invention relates to X-ray inspection technology, and more particularly, to a system and method for high energy X-ray inspection of loaded vehicles (containers or cargo in general), and more particularly, to efficient screening of cargo at critical facilities, harbors, and border crossings.

Background

Many systems for radiation inspection of trucks and containers are known, most of which are generally based on the same principle, generally by X-ray radiation from an X-ray source, forming a fan-shaped X-ray beam for the vehicle using a collimator, scanning the vehicle using the fan-shaped beam, and converting the detected radiation into digital signals after the radiation has passed the vehicle, which are then processed into images for viewing by an operator. Such systems are typically designed with multiple objectives in mind.

Some X-ray inspection systems are adapted for a high degree of mobility mainly through the use of modular construction (modular construction); see, e.g., RU 2251683. Other systems address mobility issues by placing the X-ray source on one vehicle and the detector on a different vehicle. The two vehicles are then electronically coupled together so that they move in synchronism with each other, see U.S. patent No.6,937,692. Another alternative is to place the X-ray source on a vehicle with the detector on a moving or rotatable portal (portal). The portal moves along the vehicle or container being inspected, together with the vehicle in which the detector is located, see for example us patent No.5,692,028, us patent No.5,903,623, us patent No.7,517,149, us patent No.7,497,618 and FR 2808088.

Systems with a moving source and detector of X-ray radiation typically have a rather low throughput (measured in terms of number of vehicles per unit time), which is typically due to a relatively low scanning speed (typically in the range of 0.2 to 0.8 meters per second) and due to the need for the driver to leave the examination area or at least to stand sufficiently far from the radiation source (which results in a lot of time being wasted by both the operator and the driver of the examination system); in addition, a relatively large area around the scanner needs to be preserved due to possible radiation exposure. Since the radiation source is movable and mobile, the exclusion zone where a person should not be present during scanning increases accordingly. In addition, such systems suffer from reliability problems due to the presence of moving parts and require considerable maintenance work. In addition, when both the source and detector are in motion during scanning, the effects of vibration cause image blurring and lack of sharpness. It is therefore an object of the present invention to improve the quality of data collected by a checkpoint while reducing its size, footprint (footprint) and maintenance requirements.

Fixed X-ray inspection systems are also known in which vehicles are moved through a fixed (stationary) entrance on a specific conveyor type mechanism (see, e.g., U.S. patent No.5,091,924 and U.S. patent No.6,542,580). In this case, the quality problem of the image is at least partially solved, and the forbidden area around the inspection station can be reduced. However, the throughput of such scanning systems tends to be rather low due to the low scanning speed and the need for the driver of the vehicle to leave the examination zone due to the high radiation dose usage.

The throughput of the scanner can be significantly improved in a system with a fixed source and detector if the vehicle moves through the scanner under its own power and under the control of the vehicle driver. By turning on the X-ray source only after the driver has moved past the source (which may be detected, for example, by using a special tag or bar code on the vehicle, see, for example, U.S. patent No.7,308,076), the problem of radiation exposure to the driver is solved. However, for example for persons who may be in the cargo compartment of a truck (such as illegal immigrants), or for the driver himself who is still exposed to at least some scattered radiation, complete radiation safety is still not achieved in this case. It is therefore an object of the present invention to reduce the radiation dose used to scan a vehicle while maintaining image quality.

Also known are systems for detecting radioactive substances in automobiles, such as for example described in us patent No.7,239,245, which use self-contained (autonomous) devices with their own attendant and control equipment. However, a problem that has not been solved so far is to form an integrated system of monitoring control that permits monitoring and detection of radioactive materials in automobiles, X-ray scanning, and control from a single operation center.

U.S. patent publication No.2009/086907 describes a method for X-ray control of an automobile, the method comprising the steps of: generating X-ray radiation with respect to different energies by an X-ray source; using a collimator to form a fan-shaped X-ray beam pointing to a car moving by its own power; detecting the X-ray beam after it has passed through the vehicle; and converting the detected X-ray beam into a digital electrical signal, which can later be used to form an image of the car, taking into account the car speed.

U.S. patent publication No.2009/086907 also describes an entrance for X-ray scanning of an automobile, wherein the entrance carries a collimator for forming a fan beam and also carries a detector of X-rays. The portal also carries the electronics necessary to convert the detected radiation into a digital signal. In this case the X-ray source and collimator are located on the top wall (top bulkhead) of the entrance, which adds instability to the overall construction, while the X-ray detector is buried under the road. In addition, the described system uses a relatively low energy radiation source (140 KeV), which is only useful for X-ray monitoring of cars, which typically have a metal body with a thickness of about 3 mm. On the other hand, it is not generally possible to use this system for scanning large cars, trucks, containers or container wagons, because they often have too much metal (often up to 300mm in thickness between the X-ray source and the detector) and because of the pressure exerted by heavy vehicles on the road (which can affect radiation detectors buried under the road).

Disclosure of Invention

The present invention relates to a system and method for scanning vehicles, particularly large vehicles and cargo containers.

One object of the present invention is a system and method for low dose X-ray monitoring and control of moving vehicles, including relatively large cars, trucks, containers and container transport trucks. Another object is to provide a system and method for X-ray monitoring and control of vehicles that gives nearly 100% control and monitoring of all vehicles passing through the checkpoint. Another object is to provide a system and method that uses a sufficiently low intensity radiation source that is safe for the operator of the apparatus and any person that may be located in the vehicle, regardless of where these persons are located.

Another object is to provide a system and method that can reliably detect radioactive materials transported in a vehicle being inspected.

These objects are achieved by a system comprising an X-ray source forming a fan-shaped X-ray beam by using a collimator. The fan beam scans an object (such as a moving vehicle) that is moving under its own force. Detectors on opposite sides of the moving vehicle detect the X-ray beam. The speed of the vehicle is measured. An image is formed based on the radiation detected in consideration of the speed of the vehicle. The X-ray source is a low power source that generates high energy X-rays. The width of the fan-shaped X-ray beam is comparable to the width of the detector and, in addition, the collimator slit is aligned with the direction of maximum intensity of the X-ray source and with the detector before starting the scan, based on the maximization of the output signal of the detector. The systems and methods described herein may be used on both small and large vehicles (including trucks and containers), as well as containers used in marine and air transport, and on rail vehicles.

The X-ray source preferably includes electronics that can turn the X-ray source on and off so that the entire moving vehicle can be scanned or only the cargo portion of the moving vehicle can be scanned.

If the speed of the vehicle is low, the frequency of the pulses may be reduced; or if the speed of the vehicle is high, the frequency of the pulses may be increased. If the vehicle speed is low or zero, the X-ray source may be completely off.

In addition, the output signal of the detector is normalized prior to scanning to calibrate the system.

Preferably, the pulsed X-ray radiation source generates X-rays with a maximum energy from 2.5MeV to 9MeV, preferably from 5MeV to 9MeV, which may then be additionally filtered in order to reduce the proportion of low energy photons.

When the scanned object is moving, the presence and location of a radioactive source in the vehicle is detected based on the length of the object using data from the radiation portal converted to a coordinate system on the X-ray image, taking into account data received from a speed measurement of the vehicle while the vehicle is moving through the radiation portal and a subsequent X-ray scan, which received data is then combined with the X-ray image and stored in a database.

Alternatively, the collimator slits are aligned with the direction of maximum intensity of the X-ray radiation from the source, and the collimator is moved in a direction perpendicular to the plane of the fan-beam relative to the focal spot of the source and/or rotated about an axis of rotation passing through the end of the collimator closest to the focal spot until the maximum detection signal value of the original fan-beam directly behind the collimator is reached. The output signal from the detector is then calculated, the collimator slit is aligned with the detector, the source-collimator system is moved vertically with respect to the plane of the fan-beam and/or rotated around a rotational axis passing vertically through the focal spot of the X-ray source until a maximum output signal of the detector is reached. As yet another alternative, the rotation and adjustment of the orientation of the collimator and the detector may be performed automatically by an actuator coupled to the collimator and the detector.

Preferably, the entrance is equipped with at least one optical detector that detects the presence of a vehicle in the entrance. The detector or detectors may include active components mounted on the portal and passive components mounted on the vehicle (e.g., mounted on the roof of the vehicle).

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 illustrates an overall view of a device;

FIG. 2 shows another overall view of a preferred embodiment of the apparatus;

FIG. 3 shows a plan view of the inlet of FIG. 2;

figure 4 shows an X-ray source as used in the portal of figures 1 to 3, wherein figure 4A shows an isometric view, figure 4B shows a top view and figure 4C shows a cross-sectional view along a-a;

FIG. 5 shows a circuit diagram of the apparatus;

FIG. 6 is a schematic view showing a vehicle moving through an entrance;

FIG. 7 illustrates how fluctuations in radiation intensity are corrected pulse by using the monitor/detector of the main fan beam; and

fig. 8 illustrates an example of images received from an inspection of a loaded vehicle and an inspection of the loaded vehicle along with a driver's cabin.

Fig. 9 shows the effect of the filter on X-rays.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

An apparatus for X-ray scanning of a vehicle according to a preferred embodiment is shown in fig. 1, 2 and 3 and comprises an entrance 1 with a source of X-ray radiation 2 mounted on one side of the entrance 1. The X-ray source 2 comprises a collimator 3 for forming a fan-shaped X-ray beam 4. A detector 5 is arranged opposite the source 2 for receiving radiation passing through the vehicle and for converting the received radiation into a digital electrical signal. In the example shown, the vehicle through which the radiation passes is indicated with 6. In this example, the detectors 5 are located on the longitudinal beams (vertical beams) 7 and the top cross beam 8 of the portal 1. A speed measuring device 9 is also optionally included for measuring the speed of the vehicle 1. In the example shown, the speed measuring device 9 is located in front of the entrance 1 (relative to the movement of the vehicle) at a distance no less than the length of the vehicle. The sensor 10 is located directly in front of the entrance for detecting the presence of a car.

The scanning portal 1 shown in fig. 2 and 3 additionally comprises: means for detecting the radiation source, which means usually take the form of a radiation entrance 11 and a second sensor 12 of the vehicle speed, the radiation entrance 11 being located at a distance at least equal (or greater) to the length of the vehicle being measured in front of the entrance 1 (relative to the direction of movement of the vehicle), the second sensor 12 being located directly behind the entrance 1 (relative to the direction of movement of the vehicle).

The X-ray source 2 is designed to emit X-ray radiation at a low intensity but at a high energy of photons and is located on a first alignment stage 13 (see fig. 4), which first alignment stage 13 is movable in a vertical direction with respect to the plane of the fan-beam 4 and is rotatable about an axis passing perpendicularly through a focal spot 14 of the X-ray source 2. The platform 13 is also provided with a motor 15 for moving the platform 13.

The collimator 3 is designed such that, in the plane of the detector 5, the fan-shaped beam 4 has a cross-section comparable to the width of the detector 5 (which is approximately 5mm in the exemplary embodiment). A monitor 16 for monitoring the main beam, which is the radiation emitted from the collimator slits towards the detector, is located directly behind the collimator 3. The collimator 3 is located on a second alignment stage 17 so that it can be moved in a perpendicular direction with respect to the plane of the beam 4 and so that it can be rotated about an axis passing through the end of the collimator 3 closest to the focal spot 14 of the X-ray source. The platform 17 is provided with a motor 18 which enables it to move. In a preferred embodiment, a filter 19 is arranged between the X-ray source 2 and the collimator 3 for reducing the proportion of low-energy X-ray photons. In an exemplary embodiment, the monitor 16 includes 32 sensors, the same sensors being used in the main detector 5.

As schematically shown in fig. 5, the image forming block 20 comprises a controller (control block) 21, the controller 21 comprising an interrogation (interrogation) unit 22 for scanning the detector 5, the N-1 inputs of the interrogation unit 22 being connected to the output of the detector 5 and the nth input being connected to the output of the monitor 16. In the exemplary embodiment, the interrogation unit 22 for the detector is a separate unit, however, it may be part of the control block 21. In order to synchronize the detector output with the X-ray source pulse, a synchronization input of the interrogation unit 22 is connected to the output of a power supply (not shown in the drawing) of the X-ray source 2. The output of the interrogation unit 22 is connected to a first signal input of a control block 21 and through the control block 21 to the image forming block 20. A second signal input of the block 21 is connected to an output of a sensor 10, which sensor 10 indicates the presence of a vehicle. A third signal input of the control block 21 is connected to a speed measuring device 9, which speed measuring device 9 is also connected to the power supply of the X-ray source 2 via a pulse frequency controller 23. A third input of the control block 21 is connected to the vehicle presence sensor 10 and a fourth input of the control block 21 is connected to the radiation inlet. The first and second outputs of the control block 21 are connected to the motors 15 and 18, respectively, and the third output of the control block 21 is connected to the power supply of the X-ray source 2 to enable it to be switched on and off.

The output of the image forming block 20 is connected to a display 24 to enable the display of an X-ray scanned image 25.

The optical sensor 10 includes a fixed active component portion and a set of passive portions that can be attached by service personnel on the vehicle, for example, on the top or side of the vehicle facing the fixed active portion of the sensor 10, for example, in front of and behind the top or side of the vehicle.

The proposed method for scanning a vehicle is implemented as follows.

Prior to scanning, an alignment operation is performed. The X-ray source 2 generates a beam of X-rays using a collimator 3, said beam being in the form of a fan-shaped X-ray beam 4, the cross-sectional dimension of which fan-shaped X-ray beam 4 in the plane of the detector 5 corresponds approximately to the width of the detector 5.

Preferably, the collimator 3 slits are initially aligned with the direction of maximum intensity of the radiation from the source. To achieve this alignment, the output signal from the monitor 16 is fed into a control block 21, and the output of the control block 21 is provided to a motor 18 for moving the alignment stage 17, thereby moving the collimator 3 relative to the focal point 14 of the source 12 and perpendicular to the plane of the fan-beam 4, and/or rotating the collimator 3 about its axis of rotation, which passes perpendicularly through the end of the collimator 5 closest to the focal point 3, to achieve a maximum output value of the signal from the monitor 16.

The output signal from the detector 5 is sent to the control block 21 via an interrogation unit 22. The output of the control block 21 is sent to the motor 18, which motor 18 moves the alignment platform 13 together with the X-ray source 2 mounted thereon in a direction perpendicular to the plane of the fan-beam 4 and/or rotates it around an axis of rotation passing through the focal spot 14 until the output signal of the detector 5 reaches a maximum.

As is known, the exposure dose is proportional to the area being irradiated. Thus, by reducing the width of the fan beam, a reduced radiation dose received by the object being scanned, and also a reduced amount of scattered radiation, results due to the use of a narrower collimator. Us patent No.7,539,284 describes the use of a narrow slit (rather than a wide beam) collimator in order to reduce the amount of radiation received by the patient during a medical procedure. However, in that patent, both the source and detector are mounted on relatively small rigidly mounted fixtures, as compared to the usual dimensions in the field of point-of-use.

Such small dimensions are clearly impractical for scanning of large objects such as trucks and other vehicles. In order to scan such a vehicle, the size of the scanning entrance needs to be larger than the size of the vehicle. For example, the height of the scanning portal needs to be at least approximately 5 meters and the width should be at least 8 meters. To achieve a low dose fan-shaped X-ray radiation beam, the width of the beam is comparable to the width of the detector. However, in this case, aligning the beam with the detector and maintaining the beam alignment over time is a difficult problem to solve given the overall size of the scan entrance. This is achieved using the procedure described above.

The scanning process is schematically illustrated in fig. 6A to 6D. When using the scanning portal shown in fig. 1, the object being scanned, in this case the cargo vehicle 6, is brought to a stop before it reaches the portal 1, at a distance at least equal to the length of the vehicle. It is noted that the vehicle may be any number of vehicles, such as trucks, cars, container wagons, trailers, sea containers, air containers, rail vehicles, and the like. Service personnel attach the passive elements or beacons (beacons) of the tag to the sides or top of the vehicle, typically at the front and rear of the vehicle. These passive elements or beacons may be, for example, polarized reflectors or bar code symbols for recognition by the laser scanner of the sensor 10 for sensing the presence of the vehicle in order to identify where the vehicle starts and ends.

The driver receives permission to move forward at a preferred speed (e.g., 5-10km per hour). When the vehicle 6 approaches the entrance 1 (see fig. 6A), its approach is monitored by using the sensor 10. Once the label passes the point at which the (cross) scan starts (as detected by the sensor 10), the control block 21 sends a signal to the X-ray source 2 to start operation, wherein the X-ray source 2 forms a fan-beam 4 for the detector 5 at any given moment (see fig. 6B to 6C).

The vehicle 6 passes through the fan beam 4 and the detector 5 receives the X-rays that have passed through the vehicle 6. The detector 5 converts the received X-ray radiation into a digital signal, which is read from the detector by the interrogation unit 22 of the detector 6 at a frequency corresponding to the frequency of the pulses of radiation generated by the X-ray source 2. In an exemplary embodiment, where the typical pulse frequency is 200Hz and 400Hz, the energy per pulse is an adjustable parameter that can be varied widely (e.g., from 1 μ Gy to 1mGy per pulse). The pulse frequency of 400Hz is set as a default value for a vehicle speed of 5km/h, but may be adjusted as required. The automatic adjustment of the pulse frequency is based on a linear relationship between the pulse frequency from a reference point and the vehicle speed (400 Hz, 5 km/h). Once the tag at the tail end of the vehicle passes the sensor 10, the X-ray source 2 is turned off, the scanning process is stopped, and the X-ray source 2 returns to passive mode without emitting any radiation. Alternatively, sensors may be used to determine the start and end of the vehicle. For example, sensors such as IR barriers may be used to automatically determine where the vehicle starts/ends. The use of such sensors allows slow manual attachment of the bar code or reflector to be avoided in the case of routine scanning of the entire vehicle, including the driver's cabin.

Thus, the vehicles 6 being inspected, whether the containers are large or small, can follow each other at intervals approximately equal in length to the vehicles themselves. In addition, even for large vehicles such as trucks and container transport trucks, a relatively high throughput of scanning portals is maintained.

Depending on the decision of the portal operator, only the cargo portion of the vehicle may be scanned, or the entire vehicle may be scanned. In the latter case, to ensure that the cabin where the driver is located is also scanned, a polarizing reflector or bar code may be attached to the front of the cabin.

If the speed of the vehicle is increased or decreased according to the speed measuring device 9, the pulse frequency controller 23 increases or decreases the frequency of the pulses accordingly, thereby maintaining the spatial resolution, exposure dose and scattered radiation parameters. The automatic adjustment of the pulse frequency may be based on a linear relationship between the pulse frequency starting from a preset reference point and the vehicle speed (e.g. 200Hz for 5 km/h). When the vehicle speed V measured by the speed measuring device 9 becomes greater than or less than a reference speed (e.g., 5 km/h), a new pulse frequency value F is calculated by the pulse frequency adjuster_new=F_ref/V_refV, wherein, F_refReference frequency (200 Hz), V_ref-reference speed (5 km/h). The pulse frequency controller will update the new value F_newTo the accelerator power supply unit, and then changes the acceleration parameter to allow the accelerator to be driven fromThe next radiation pulse starts with a new frequency value. In addition, the control block 21 may generate a signal that the X-ray source 2 is to be switched off if the output signal from the speed measuring device 9 approaches a predetermined minimum threshold or disappears completely. Thus, if the vehicle stops by itself or moves too slowly, the scanning of the vehicle will stop. Typically, in such a case, the scanning process would need to be restarted. This also achieves maximum radiation safety for involved or potentially involved persons, such as illegal immigrants and/or vehicle drivers.

Preferably, the X-ray radiation is filtered to reduce the proportion of low energy photons. The use of such filters is generally known and is often used to reduce the dose of radiation received by a patient in a medical X-ray system. Similar methods for reducing the radiation dose received by a vehicle and for reducing the amount of scattered radiation can also be applied to inspection systems that X-ray scan cargo by using X-ray radiation having a relatively high energy (e.g., 3-9 MeV), see, for example, U.S. patent No.6,459,761. Such filters are preferably made of a high atomic number material (e.g., lead or tungsten), although other materials like steel may also be used. Photons with low energy (e.g., below 0.5 MeV) attenuate more than photons with higher energy, and therefore, the filtered beam contains fewer photons of low energy. Since low energy photons contribute to the dose to the object, but cannot pass through a dense object to the detector, beam filtering significantly reduces the dose to the object with a very small reduction in the detector signal. For example, for a 5MeV source and an object with an equivalent thickness of 100mm steel, a 60% dose reduction can be achieved by using a 5mm lead filter, while the detector signal is reduced by only 30%. In an exemplary embodiment, the cross-section of the beam is gaussian. The beam width being substantially equal to the width of the detector means that the HWHM of gaussian type is substantially the same as the detector pixel height (5 mm).

An exemplary experiment using the proposed apparatus 1 shows: when high energy X-rays (2.5 to 9MEV, preferably approximately 5MEV, or 4.5 to 5.5 MEV) from a low power pulsed X-ray source (up to 20 roentgens per hour) are used, both the vehicle driver and any person located in the cargo area receive a radiation dose of no more than 1 μ SV. Because the width of the fan beam 4 is relatively low and the beam is aligned with the detector, the typical radiation dose received by the driver is typically no more than 0.02 μ SV. By way of comparison, ICCR 2007 established annual radiation doses no greater than 1,000 μ SV from non-medical sources. Thus, the goal of reducing the radiation dose received by a person in the scan portal has been successfully achieved. Fig. 9 shows the effect of adding a filter 19 (5 mm of Pb) which eliminates about 50% of all photons from the original spectrum (with a maximum at 5 MeV), leaving only high energy photons with energies above 200KeV, while the number of photons between 200 and 500KeV is significantly reduced.

The third input of the control block 21 is also supplied with an output signal from the speed measuring device 9, which output signal is sent from the control block 21 to the image forming block 20, which image forming block 20 in turn is able to reduce various geometrical distortions due to uneven movement of the vehicle 6. The algorithm for correcting geometric distortion may be the same as or similar to the algorithm described in U.S. patent No.7,453,614 for reducing image spatial resolution non-uniformity due to variations in the distance between the detector and the object. The difference here is that: unlike the distance difference described in U.S. patent No.7,453,614, it is a change in the moving speed of the vehicle (object) being adjusted. Preferably, the base scan length of the vehicle between successive radiation pulses is calculated based on the corresponding speed of the vehicle and the known radiation pulse frequency for each radiation pulse. Next, each image line (imageline) is interpolated by using any known interpolation algorithm, such as linear or cubic interpolation, and a new image signal is calculated line by line for a new pixel group for which the basic scan length of the vehicle is the same for any consecutive pixels in a line, wherein the basic scan length corresponds to a preset reference vehicle speed (preferably 5 km/h).

The pulses from the X-ray source 2 have an amplitude which varies randomly or pseudo-randomly as a function of time, which also results in the same variation of the output signal from the detector 5 (see fig. 7A). This results in reduced accuracy and reliability during scanning. To eliminate this effect, the main beam 16 is also pulsed from the X-ray source 2, the main beam 16 being in the form of one of the parts of the detector element similar to the part converting the X-ray signal into an electrical signal. During the scanning process, the output signals from the monitor 16 are provided to the N signal inputs of the interrogation unit 22. In the control block 21, these signals are averaged and the average value is used to normalize the output of the detector by dividing the signal of the detector sensor for each radiation pulse by the averaged monitor 16 signal for the same pulse and multiplying the result by some integer constant. This eliminates feedback effects due to amplitude variations of the X-ray pulses (see fig. 7B), which also results in a further improvement of the image quality.

Based on the X-ray radiation data received by the detector 5 and the output of the vehicle speed sensor 9, an image is formed and provided to a display, for example, as shown in fig. 8. The displayed image can be analyzed by an operator for smuggled goods, contraband, concealed compartments, etc. Depending on the results, the operator may permit the driver to proceed or guide the vehicle into the isolation zone for closer inspection.

When using the scanning portal shown in fig. 2, the vehicle 6 is stopped in front of the radiation portal 11. Service personnel attach passive tags or beacons (such as barcodes, polarized reflectors, etc.) to the sides of the vehicle to detect them by a laser or barcode scanning system that is part of the sensor 10. This is done to identify the points at which scanning should begin and end.

The driver is then permitted to proceed at a speed of approximately 5-10 kilometers per hour. The speed of the vehicle is monitored by the speed measurement device 12 and the presence of radioactive material in the vehicle is directly detected by the radiation portal. The output signal of the speed measuring device 12 is supplied to the radiation portal 11, the radiation portal 11 generating an output signal taking into account the vehicle speed. The output signal from the inlet 11 is supplied to a control block 21.

An X-ray scan of the vehicle is performed as discussed above.

Based on the received X-ray data, the measured speed of the vehicle, the position of the vehicle, etc., the control block 21 converts the received electrical signals into a coordinate system. The data is combined and may be stored in a database. The proposed system and method thus provide reliable inspection and control of the transport of hazardous and radioactive materials, while maintaining all the advantages described above.

Having thus described the preferred embodiments, it should be apparent to those skilled in the art that certain advantages of the described methods and apparatus may be realized. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. The invention is further defined by the appended claims.

Claims (22)

1. An apparatus for X-ray scanning of a vehicle, the apparatus comprising:

a pulsed X-ray source that generates X-rays;

a collimator that forms a fan-shaped beam from the X-rays;

a detector that detects the fan-shaped beam after the fan-shaped beam passes through the vehicle;

a speed sensor that measures a speed of the vehicle passing the apparatus and provides an electrical output corresponding to the speed;

an image forming module that converts an output of the detector into an image of the vehicle based on a measured speed of the vehicle;

wherein a cross-sectional dimension of the fan beam is comparable to a width of the detector;

wherein greater than 50% of the X-rays comprise photons having a maximum energy between 5MeV and 9 MeV; and

wherein, prior to the scanning, the fan-beam is aligned with the detector by moving the collimator relative to a focal spot of the pulsed X-ray source in a direction perpendicular to a plane of the fan-beam to maximize an electrical output of the detector.

2. The apparatus of claim 1, further comprising a filter adjacent to the collimator for filtering out low energy X-ray photons.

3. The apparatus of claim 1, further comprising a vehicle presence sensor, wherein an output of the vehicle presence sensor is used to turn the X-ray source on and off.

4. The apparatus of claim 1, further comprising an alignment stage for aligning the fan-shaped beam with the detector.

5. The apparatus of claim 1, wherein a frequency of the pulses is adjusted based on a speed of the vehicle.

6. The apparatus of claim 1, wherein the X-ray source is turned off if the speed of the vehicle is below a predetermined threshold.

7. The apparatus of claim 1, wherein the output of the detector is normalized based on an average reading of the main beam.

8. The apparatus of claim 1, wherein the alignment is performed by aligning slits of the collimator with a direction of maximum X-ray beam intensity from the X-ray source.

9. The apparatus of claim 4, wherein said alignment is performed by movement of said alignment stage in a perpendicular direction relative to the plane of said fan-beam.

10. The apparatus of claim 1, wherein the alignment is performed by rotation of the fan-shaped beam about an axis passing through an end of the collimator closest to a focal spot of the X-ray source.

11. The apparatus of claim 1, wherein the apparatus detects radioactive objects in the vehicle.

12. The apparatus of claim 1, wherein the X-rays comprise primarily photons with maximum energy between 5MeV and 5.5 MeV.

13. A method of scanning a vehicle, the method comprising the steps of:

generating X-rays from a pulsed X-ray source;

forming a fan-shaped beam from the X-rays;

aligning the fan-beam by moving a collimator relative to a focal spot of the pulsed X-ray source in a direction perpendicular to a plane of the fan-beam to maximize an electrical output of a detector that detects the fan-beam;

measuring a speed of the scanned vehicle and providing an electrical output corresponding to the speed;

forming an image of the vehicle by converting an output of the detector into an image of the vehicle based on the electrical output corresponding to the measured speed of the vehicle;

keeping the cross-sectional dimension of the fan beam comparable to the width of the detector,

wherein the X-rays consist essentially of photons having a maximum energy between 5MeV and 9 MeV.

14. The method of claim 13, further comprising filtering out low energy X-ray photons.

15. The method of claim 13, further comprising turning the X-ray source on and off based on a signal from a vehicle presence sensor.

16. The method of claim 13, further comprising aligning the fan-shaped beam with the detector.

17. The method of claim 13, further comprising adjusting a frequency of the pulses based on a speed of the vehicle.

18. The method of claim 13, further comprising aligning slits of the collimator with a direction of maximum X-ray beam intensity from the X-ray source to facilitate aligning the fan-beam.

19. The method of claim 13, further comprising moving an alignment stage in a perpendicular direction relative to a plane of the fan-beam.

20. The method of claim 13, further comprising rotating the fan-shaped beam about an axis passing through an end of the collimator closest to a focal spot of the X-ray source to align the fan-shaped beam.

21. The method of claim 13, further comprising detecting radioactive material in the vehicle and generating an output signal based on a speed of the vehicle.

22. The method of claim 13, wherein the X-rays comprise primarily photons with a maximum energy between 5MeV and 5.5 MeV.