Device could offer more accurate baggage screening

A checked baggage screening device that overcomes limitations of 2D X-ray or CT scanning systems is being developed by University College London (UCL) and 3DX-RAY.

Designed to detect threats including explosive and incendiary materials, the proof-of-principle system is being developed for a project funded under the Innovative Research Call in Explosives and Weapons Detection (2007), a programme sponsored under the Home Office’s counter-terrorism (CONTEST) strategy.

UCL, headed by Prof Robert Speller, approached Barrow-upon-Soar-based 3DX-RAY after completing a feasibility study into alternative methods of producing 3D tomographic images for baggage inspection. 3DX-RAY provided the hardware and systems expertise to integrate UCL’s new tomographic imaging software to produce a proof-of-principle system.

Checked baggage inspection is designed to eliminate false alarms from threats through a series of inspections and the first line of defence is 2D X-rays, which are prone to delivering high false-alarm rates.

CT scanning X-ray techniques are said to be more accurate but are costly and slow. UCL believes it has identified a more accurate and effective system that will lower the volume of bags that have to go for additional screening.

The research team realised it can achieve the same effect as CT scanning X-ray techniques by collecting images from multiple angles using 2D X-ray sources and detectors with an overhead visual camera and using algorithms to collate these X-ray ‘slices’ and produce 3D images.

Nick Fox, 3DX-RAY’s chief technical officer, explained to The Engineer via email that in conventional tomography an object remains stationary while an X-ray camera rotates around it, building up slices of data that eventually provide a fully reconstructed CT model.

Fox said: ‘In this instance there are multiple stationary cameras mounted around a curve in the conveyor system.

‘As the object passes down the conveyor both X-ray and optical images of the images of the object are obtained simultaneously and as the object changes its orientation… multiple views of the object are collected from each of the stationary cameras.

‘By relating the X-ray image to its respective optical image it is possible to collate the X-ray image to the physical orientation of the bag and generate a tomosynthesis X-ray image of the object containing sufficient information to identify potential threats within the bag.’

Fox added that the proposed system has no moving parts, making it a simple and low-cost system in terms of maintenance and lifetime costs.

‘A CT system requires the maintenance of [the] rotating gantry that supports high-voltage power supplies, X-ray generators, [and] a large array of detectors — all with the added complication of getting power and data on and off the gantry as it rotates,’ he said.

Airport trials of the device are expected in the next two to three years.