By Nicholas Fox

Few areas have seen such a concentration of technology and funding -- especially in the USA.  But despite that, the challenge is a daunting one, how do you find a very small package in a world-sized haystack?  The only way to overcome the fear and threat of global terrorism is to develop much smarter and ever-more reliable technology. 

Let me try to put the problem, and the market, in perspective.  Even just taking airline security, the FAA estimate that around half a billion bags, cases and packages are scanned every year -- and the technology may have to find just one bomb in all of that!  And to make it worse, terrorists can be smart -- the simple plastic explosives tucked into a portable tape player that brought down Pan Am Flight 103 over Lockerbie, Scotland in 1988 are a thing of the past.  Today terrorists mould explosives into common shapes, and rely on the fact that the density of Semtex is close enough to other materials to make it hard to distinguish from normal packages.

On top of that there are knives, guns and all manner of devices, all of which can be dismantled and disguised.

And that’s just airports -- but as London saw not so long ago, the threat is everywhere and most places can’t afford the queues and congestion that people now accept as routine at airports.

MARKET FACTORS

Over the period from 2001 to 2010 the total U.S. annual people screening outlay is expected to grow by some 1500%.  Sales of US$3.5 billions have been predicted for 2006 and US$9.9 billions by 2010.

The accumulated U.S. investment in people screening over the period is estimated at over US$50 billion, with the U.S. people screening service business expected to grow from US$85 million in 2003 to US$1.85 billion by 2010. 

Over 80% of this will be using technologies that simply were not in existence in 2003.  The cost of screening a single person is predicted to be slashed by a factor of 10 -- from US$4-US$5 per person/per checkup to under US$0.5 for the same procedure.

The most noticeable part of screening is still probably airport luggage and the global market for carry-on baggage, mail and parcel screening X-ray systems is around 50,000 units.  The total addressable market for complementary systems is 2,000-3,000 units/year, giving an average market value around US$40-70M pa.

Growth in this area has been rapid -- before 9/11, just 5% of checked bags were screened, so the 100% of checked bags that are now run through EDS (Explosive Detection System) machines in the U.S.A. is quite an achievement in the timescale

TECHNOLOGY FACTORS

To date, technology can’t deliver the ability to screen quickly, against all threats or at a reasonable cost.  Possibly it never will be able to achieve it to the world’s satisfaction -- for every two step forwards in detection there will be at least one step in the terrorist ability.  Admittedly, the technology that’s actually available in the marketplace, as opposed to the “vapourware” of marketing promises is about to change with the advent of the multiple-threats “checkpoint of the future” with their extensive biometric and identification abilities.  This is a step in the right direction.

Almost every threat that requires screening demands a different technology (explosives, weapons, biological, chemical and nuclear/radiological).  None of these are perfect and they currently deliver high false alarm rates, slow throughput, operator dependence and high transaction costs.

Each threat is different -- so I will concentrate on my area of expertise -- the widely used X-ray systems that are prevalent in airports for baggage screening and the systems used on the streets to detect if parcels are innocuous or are dangerous. 

TECHNOLOGY ISSUES

In some ways X-ray technology seems almost perfect for detection -- it allows you to look inside sealed containers, without the danger of physical contact.  It can even be used remotely from the package.

Pre 9/11 conventional X-ray inspection systems had many limitations.  Perhaps the most serious was that they did not offer any of the depth clues that are provided by a person’s normal vision (human depth perception allows us to see in 3D).  Also the resolution was usually not good enough to detect the subtle differences that may indicate chemical or biological threats.

At the time most X-ray systems were mere “Shadow-graph” images, flat, 2D representations that gave no help as to the type of material being viewed -- just a vague feeling of density.  Also, devices were typically static and positioned in fixed locations.  This leads to difficult detection twinned with a high rate of false alarms.

Let me consider the technology now becoming available for both fixed tunnel systems, such as those used in baggage screening at airports, and the new breed of portable devices used for analysing packages on the streets.

WHAT IS X-RAY IMAGING?

In simple terms, when X-rays encounter an object in their path they may be affected in one of two ways.  They may either pass completely unhindered through the object (transmission), or they may interact with the object and are effectively absorbed.  The number of photons that are absorbed by an object will be related to the object’s density, so if you place a detector sensitive to X-rays behind an object exposed to X-rays you will see a ‘shadow’ of the object where relative densities of the object and its contents will be represented by different grey levels in the shadow.  X-ray detectors can take many forms, from the traditional film-based systems still used in many medical applications, to the increasingly common semiconductor detectors, employing an X-ray sensitive scintillator or phosphor coupled to photodiodes.  The systems we discuss here are of the semiconductor type, where the X-ray shadow is measured as an electrical signal from an array of photosensitive devices.

TECHNOLOGY ADVANCE

Resolution

Recent improvements in X-ray sources, coupled with detector advances and some very, very, clever processing tricks have eliminated the problem of low resolution, details as small as 100 microns (μm) are now easily resolvable, even on fast moving conveyors.  This is about the width of a human hair and is far greater than is needed for many security applications.

This represents a real development.  For example, when a suspect package is identified, the main decision was typically where to position the disrupter to create a controlled explosion.  With the potential risk of a ‘dirty’ device, the use of disrupters can lead to terrible consequences!  In such situations this improved discrimination is vital.

Automatic Image Processing

Automating image processing sounds a small and sterile part of baggage handling.  However, when you remember that over half a billion bags are screened every year, an operator error failure rate of even one can be catastrophic.  Although we will probably never do away with the human element (nor should we as humans are very good at pattern recognition) we are now beginning to use technology to give them as much support as possible.  Automatic detection of a wide variety of shapes, in a massive range of combinations is now becoming possible with the latest image processing techniques.  Although not readily available yet, this is set to be a significant area for future advances.

3D Imaging

A disadvantage of conventional X-ray systems is the lack of depth information.  A single X-ray image does not let you see what is on top of what.  It simply wasn’t possible, for example, to even see how a wire is routed through a bag -- and significant operator experience was required to solve these types of inspection problems.  The simple trick of taking more than one image at a time allows an operator viewing the image on a special purpose monitor to see realistic 3D images in real time.  Another problem solved!

Material Identification

During the scanning of a bag, the quantity of X-rays that reach the detector depends on the amount and type of material in the target.  A thick item will absorb many more X-rays than a thin one and will appear darker than a thin object.

However, the density of an object will also affect this, making it difficulty to distinguishing if an item is thick or dense.  A harmless thin aluminium object could easily look like a thicker block of explosives.

Fortunately different materials absorb X-rays in different ways.  Measuring X-rays at two different energies allows the computer to distinguish between colour objects that are organic (such as plastic explosives), non-organic (such as a gun) or mixed. 

The graph shows two example spectra of X-rays that were detected after penetrating different objects.  One is a 5cm thick lump of explosives (green), in this case Semtex.  The second one is a much thinner 2cm piece of aluminium (blue).  Most of the X-rays are absorbed by the objects, so they have very similar characteristics in this respect.  However, the energy distribution differs from material to material.  In this example, more lower energy X-rays penetrate the Semtex than the aluminium.  This difference in the absorption spectrum allows us to identify if an object is made out of a low (organic), medium (mixed) or high (inorganic) atomic number material.

Portable Bomb Detection Technology

Portable X-ray detectors have been around for a few years, but recent advances have made them much more effective.  Not only can they offer all of the advantages mentioned above, but there are three, seemingly simple, but absolutely vital developments.

Firstly they have become truly portable -- and by this I don’t just mean someone has simply added a handle.  Portability is particularly important when you consider the thick protective clothes that operatives (very sensibly) wear.   The portability has come about both through the improvements in X-ray sources and, perhaps more importantly, in detector technology.

Second, the detectors are now much thinner than earlier models -- in the case of the image shown just 5 cm thick.  This doesn’t sound important -- until you realise that a terrorist could totally bypass the old detectors just by leaving their bag close to a wall!

The last advance is the very simple one of wireless connection -- which means that an operator can simply drop the source and detector into place and then retire to a suitable distance to view the results!  No more wiring on-site and no more need for the heroism of standing next to a potential bomb and waiting for the system to click in!

WHERE WILL X-RAY THREAT DETECTION TECHNOLOGY GO NEXT?

There are several ways the technology could develop over the coming years.  For example, people are now working on enhancing novel two-detector and dual frequency technology, partly with the aim of offering more accurate material identification.

Another development is in backscatter technology.  This technique allows the detector to be on the same side of the package as the X-Ray source and the rays that are ‘scattered’ back from it are analyzed.  The method has been found to be particularly effective in detecting items close to the surface of a bag, an area where other technologies can have problems.  Advances in analysis techniques mean that higher quality images will now be available overcoming one of the barriers of this innovative technologies reaching mainstream baggage inspection.

Another advance may well come with increasing computer power which will enable X-ray CAT scan techniques, which are already available from companies such as ours, become far faster, becoming practical in real-world mass-use applications.  And yet another may come from extending X-ray techniques into the frequencies associated with Gamma rays and Neutron detection.

However, these methods are based purely on physics, but other advances look set to flow from the image processing side -- particularly based on quantifying human cognitive skills, particularly pattern recognition and visual perception and feeding this back into both image processing algorithms and the way the operative works.

Sadly terrorists also have significant technical knowledge about explosives and this can instill immense fear and apprehension in civilians and governments alike.

As a result, the future growth and technology potential of the market is, literally, explosive.

Nicholas Fox is CEO of Image Scan holdings and 3DX-Ray Ltd.

For more information, please send your e-mails to swm@infothe.com.

ⓒ2007 www.SecurityWorldMag.com. All rights reserved.