The business of installing explosive-detection systems at airports in the United
States has been captured, for the most part, by two companies that traditionally
have focused on military and defense programs.
L-3 Communications and InVision Technologies have developed screening devices
designed to more accurately recognize chemical and physical properties of scanned
objects—something the current X-ray equipment fails to do, according to
The U.S. Transportation and Security Administration, last year, awarded InVision
Technologies and L-3 Communications initial contracts of $512.9 million and
$355 million, respectively, to deliver two types of explosive detection systems—the
625 CTX and the 425 eXaminer 3DXTM.
These two explosive detectors are the only ones that have been certified for
further testing, out of 19 others currently in prototype development stages.
The InVision systems sold to TSA include the CTX 5500 DS—at $1 million
each—and the CTX 9000 Dsi, a more advanced system that costs $1.5 million.
L-3’s detector runs about $800,000 per unit.
At the core of the CTX and eXaminer systems is a commonly used medical technology
called computerized tomography (CT), which scans the interior of a person’s
body. CT uses two- and three-dimensional images to create virtual cross-sectioned
slices, or tomographs, of specific areas.
“Simple X-ray analysis is no longer enough to make the kinds of timely,
decisive conclusions necessary to achieve the safety and efficiency demands
of today’s airline industry,” said David M. Pillor, InVision’s
senior vice president. “The challenge, in meeting FAA requirements, was
to create a single system with a high degree of speed and accuracy, capable
of minimizing false alarm frequency while simultaneously maximizing detection
Using standard electromagnetic imaging, the CTX and eXaminer systems present
three-dimensional properties of explosives in cluttered passenger bags. In a
full 360-degree rotation, images are taken from all angles as streams of light
intersect throughout the bag.
With CTX, the density, mass and volume of materials are obtained and analyzed
using computations that match findings against a database with already known
“The most difficult task confronting an EDS system is distinguishing
potential explosives from harmless objects” that may have similar traits,
said Joe Paresi, president of L-3 Security and Detection Systems Division.
“Not only do certain electronic items have parts that look suspiciously
like bomb parts, but they are often hidden under layers of other items. The
result is a complex, two-dimensional image that requires computer analysis to
CTX technology examines the unique density signatures produced when electromagnetic
radiation passes through different substances. The medium-frequency light waves
(X-rays) react differently depending on the material’s density.
A cross-section, or CT slice, of an item can then be constructed, using mathematical
algorithms that are pre-programmed into system software.
“Three-dimensional, cross-sectional analysis turns suspicion into near
certainty,” Pillor noted. “With a virtual reconstruction of an object’s
internal structure, fewer false leads are encountered, allowing passengers to
pass more quickly.”
CTX hardware comprises a conveyor gantry, X-ray tube chamber, CT scan chamber
and an operator control station. Once through the X-ray chamber, baggage moves
into the CT chamber, where processors use the X-ray data to compute findings
into CT slices.
CT scanning reveals specific object densities and volumes that enable computation
of item mass. Concealed items do not affect processing since only the objects
with specific X-ray signatures are selected for further analysis.
After entering the CT chamber, a bag is divided virtually into three-dimensional
units called “voxels.” Based on their similarities, certain voxels
are grouped together as volumes of the same objects within a bag, so that the
density of the scanned object can be determined.
Based on density and volume, CTX and eXaminer software automatically correlate
the mass characteristics of luggage contents to those of potential explosives.
If the system finds a match, it alerts the operator, by highlighting suspect
areas within the CT slice.
“Like most detection technologies, CT scanning only provides an operator
with a positive or negative assessment,” stated Paresi. “The ultimate
decision as to whether an object needs further examination remains the operator’s
At average weights between 7,000 and 11,000 pounds and a size of about 6 feet
long by 5 feet high, the CTX and eXaminer systems can be integrated with existing
airport X-ray equipment or can be used as stand-alone systems. Both technologies
are able to process an average of 300-500 bags per hour depending on the number
of positive identifications.
According to Pillor, the systems are supposed to eliminate the false alarms
that happen with X-ray scanning, which can take about three to five minutes
L-3 has projected EDS sales for 2003 at approximately $175 million, a portion
of which will come from an order with Singapore for airport security systems
and EDS products. Meanwhile, InVision projects EDS 2003 revenues from sales
and services to reach $400 million. That number also includes current product
orders with Spain and Israel.