Scatter for cover

Airport luggage screeners may soon have a tool at their disposal that combines 3D imagery with the ability to highlight any dangerous substances being carried on to a flight.

The tool, the world’s first scatter-enhanced 3D X-ray scanner, is being developed by researchers from Cranfield and Nottingham Trent Universities. The Home Office scientific development branch and the US Department of Homeland Security are also involved.

The team intends to combine scattered X-ray signals with high-resolution 3D X-ray images to give baggage screeners previously unseen information regarding luggage size, shape and chemical composition of the contents contained therein.

To bring the idea to fruition, new compound semiconductor sensors will have to be developed that are capable of directly detecting X-rays. The signal contributions from the sensors will then combine to provide images to the luggage screener.



Material analysis

Scattered X-ray imaging can provide scientists with precise information about a material’s composition. The crystal lattice structure of a material scatters the X-ray as it passes through and this scattering tells scientists exactly what the material is made up of.

‘If you take a picture of a suitcase to see the contents, one of the difficulties is seeing what the materials are,’ said Prof Keith Rogers of Cranfield University. ‘To get that final jigsaw piece that definitively defines the material you need to go to the scattered information.’

He added: ‘Scattering is a well used forensic tool used for testing many things, from the authenticity of paintings to fundamental studies of bone material.’

The two X-ray techniques have not been combined for a single use before. Previously, efforts have concentrated on separating one form of X-ray from the other to give a clearer picture or X-ray analysis.

For the project to be successful, the strength of scattered radiation signals need to be increased.

‘We have a brand new concept which increases the signal,’ said Prof Paul Evans of Nottingham Trent University.

‘New imaging geometry is driving it and we will be able to produce new types of 3D screening to identify and discriminate materials. It will replace the current technique of colouring groups of elements which is, scientifically, wholly inaccurate.’

Improved imaging geometry is made possible by the configuration and arrangement of sensors containing compound semiconductors in single crystal form. Combined correctly, they will collect far more signals than previously possible.

Evans believes the stronger signal will speed up security checks at airports, allowing luggage to be screened in about five seconds.

This will be particularly welcomed at airports such as Heathrow International, which processes 68 million passengers each year.

Similarly, the technology could be employed in any industry where high-volume inspection is required. Evans believes that applications for the technology could go even further.

‘This system might also be able to compete with CAT scans, giving 3D X-rays, but without the rotating and spinning masses which make them very expensive to make and maintain,’ he said.

Rogers added: ‘It will have a huge impact not just on security but on medicine and engineering. The potential is really enormous.

‘Some of the work we have done has shown that the scattered information does provide very valuable markers for cancer. With this we have got a very good chance of making a good diagnosis.

‘It could also be used for a lot of non-destructive testing for engineering.’