Non-Subscriber Extract
Multiview x-ray has wider vision
By Barry Cross
19 February 2008
The Transportation Security Administration (TSA) in the United States and the UK's Department for Transport (DfT) seem set to adopt multiview x-ray machines as standard equipment for screening hand baggage in the very near future.
Not only will these be able to offer multiple views of objects within each bag but they will also automatically detect the presence of improvised explosive devices (IEDs) in hand luggage. At least one official at a multiview machine maker expects them to replace existing single-view x-ray equipment because of the latter's technological limitations.
While dual-energy, single-view x-ray systems have already been developed and are capable of undertaking material discrimination, they are unable to automatically detect explosives with accuracy. The logical next step among manufacturers was therefore to shrink hold baggage-screening equipment - which does have this automated facility - to make it suitable for use at airside checkpoints.
Smiths Detection and Rapiscan Systems have entered the multiview x-ray machine market with their respective HI-SCAN 6040aTiX and MVXi models, which can cost up to twice the price of single-view machines. However, both incorporate an array of x-ray generators and sensor lines that enable bags to be scanned from several angles.
In a single-view machine, it is impossible to differentiate visually between a bottle of soft drink and liquid explosive, while foodstuffs such as apples, oranges and chocolate can also be mistaken for high-density explosives. However, by scanning an object with high-level and low-level x-rays and then comparing the results, it is possible to calculate that object's atomic number and thereby work out whether any threat is present.
The various angles also help to prevent classification errors - many of which are due to the superimposition of various objects and materials in cluttered bags - and additionally to determine the volume of an object, which is another important element in the overall calculation.
Airports in the UK are openly embracing this new technology. Smiths Detection is to supply 35 HI-SCAN 6040aTiX units to London Heathrow's new Terminal 5 (T5), for example. These advanced, threat-identification x-ray machines will undertake all cabin baggage screening at the new terminal; of the 35 checkpoints where the aTiX systems will be deployed in T5, 22 are purely passenger checkpoints while the other 13 will be used for staff screening.
However, T5 should not be seen in isolation, since BAA is engaged in a deployment programme to replace all checkpoint x-ray machines at its seven UK airports with aTiX systems. This activity is expected to be fully implemented over the next three to four months. At the time of writing, all checkpoints at London Heathrow - including Terminals 1 to 4 - are already equipped with fully operational aTiX machines.