Portland, Ore. Since the British police foiled the plot to smuggle liquid explosives onto U.S.-bound commercial aircraft in carry-on baggage, the Transportation Security Administration (TSA) has been scrambling to develop technologies that could spot such items. Luckily, the best bet for identifying liquid explosives, according to its developer, is already in beta testing at Boston's Logan International Airport. Dubbed Cobra by developer Analogic Corp. (Peabody, Mass.), the scanner can detect objects of any shape that are massive enough to be a threat including liquid explosives. If it passes certification by the TSA, Cobra could be deployed in airports nationwide by mid-2007.
"Our electrical engineers have taught Cobra's computer to not only recognize the shape of threatening objects, such as guns and knives, but also to measure the density of objects so as to recognize when an unidentified mass--including liquids--is of sufficient volume to be a potential threat," said developer John W. Wood Jr., president and CEO of Analogic.
Both Cobra and a larger version called Exact, which has already been installed in more than half of the major airports in the United States, draw on Analogic's expertise in making medical scanners. By the late 1990s, Analogic was already adapting what was then called the "CAT" scanner--today called computed tomography (CT)--for use by airport security.
After Sept. 11, the TSA mandated that all checked baggage be scanned, and Analogic's Exact was available to meet the need. The company quickly sold 525 Exact scanners, for sales of $525 million. The system, standing more than 7 feet tall and weighing 6,700 pounds, screens checked baggage automatically in an airport's private back room, diverting any suspicious bags to a side conveyer, where they are hand-checked with trace detectors.
Cobra scales down Exact to a size and cost that makes it economical for use in screening carry-on bags.
"The threats have evolved from pistols and knives to box cutters and suicidal terrorists willing to blow up the plane they are traveling in and use it as a weapon to fly into buildings," said Wood. "So we have adapted our software to look for these new threats--from butane lighters and liquid binary explosives to flammables and all sorts of things." The underlying technology has been integrated into third-generation devices that check carry-on bags for new threats.
Cobra scanners will sell for $350,000 to $450,000, compared with $40,000 to $70,000 for a standard X-ray machine. However, Analogic claims the scanners will pay for themselves in a couple of years, because their automated 400-bag-per-minute speed will eliminate the need for two human screeners at each checkpoint.
"There are currently 42,000 screeners that cost approximately $2 billion annually, but by using our Cobra at passenger checkpoints, we could reduce the number of screeners required," said Wood. "You also get much smoother passenger flow, because Cobra doesn't require a passenger to remove, for instance, a laptop from their briefcase. And our threat recognition software means that screeners only need to inspect bags that contain a possible threat item." Wood, who has twice testified before Congress on airport security screening, predicts that the TSA will finish Cobra certification by early next year, permitting U.S. airports to begin screening carry-on baggage by mid-2007.
The disadvantage of conventional X-ray machines, according to Analogic, is that they are two-dimensional. Thus, an X-ray can see a gun or knife only when it is lying flat. In addition, there is no intelligence in the machine--no automated threat evaluation to assist the screener. The quality of the screening process depends entirely on the diligence of the personnel watching every single bag.
In contrast, Analogic's CT scanners use a single emitter of a fan-shaped X-ray beam on a rotating gantry that encircles the bags passing through. By virtue of thousands of detectors on the other side of the gantry, intelligent software can recreate a 3-D image of the bags and all their contents. The image can then be rotated to any angle for quick viewing.
The detectors first convert incident X-rays into visible light that is then directed at integrated photodetectors, which send the data, via brushes on the gantry, to a computer workstation. The software also performs automatic object recognition, puts a red square on possible threats, then presents the results to the screener, who uses a touchscreen to rotate the image to any orientation.
"We don't use fuzzy logic or neural networks," said Wood. "What we can do, and do very well, is recognize the difference between ordinary objects and unusual ones massive enough to be a threat." Suspicious objects can be hand-checked with a trace detector.
The images are also transmitted over a network to a server for subsequent viewing. Thus, if an aircraft goes down, the images of the bags that were on it can be studied after the fact. The third-generation CT technology uses dual power settings that measure the density of objects and are represented to screeners as different colors.
"We adapted the technique that was first developed to measure . . . bone density," said Wood. "Cobra uses the same method to measure density, enabling us to accurately assess whether objects we see in bags are massive enough to be a threat."
As new threats are identified, Analogic updates its recognition software to identify them without having to change the hardware in Exact or Cobra. However, Wood warns that successful airport security will always depend on layers of protection--layers that include people trained to recognize possible threats.
Screeners rotate 3-D views of luggage to identify threats like a knife (barely visible in left image) and C4 explosive (shown in red).