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The world's most popular Explosive Detection Systems (EDS). The current version, the CTX-5500DS, is a second-generation system with a number of improvements over the original. This unit is a hot item thanks to the increased security concerns following the September 11th terrorist attacks.

The "CT" in CTX stands for Computerized (Axial) Tomography, a process that uses a computerized rotating X-ray system to scan an object into a sequence of image slices. These slices can then be reassembled by the computer to form a 3D model. Objects whose shapes and densitites conform to known threats result in an alarm. An operator then makes the final decision by looking at the 3D model onscreen. Potential threats are highlighted in red, detonators in green, metal in blue, and shielding materials in yellow.

Unfortunately, the generation and analysis of a CT scan is not a speedy process compared to conventional X-ray. To process every bag on every flight this way would result in major slowdowns in air travel. The CTX-5500DS units address this problem by performing a conventional X-ray (Scan Projection) before the CT scan. The scan projection X-ray is used to determine which bags require the more intensive CT procedure. Depending on the mode used, a CTX-5500DS can scan about 384 bags per hour.

Invision has included some interesting features in these scanners. One of them is "Threat Image Projection" (TIP). The TIP system randomly inserts phony explosive devices into the bags displayed on the operators' screens. Even though the operator can be located up to 1/2 mile away from the scanner unit, I imagine this would be pretty hard on their nerves! If this feature is enabled by the management the the machine can keep statistics on the operator's success at spotting the devices.

A full installation of a CTX-5500DS unit can currently cost about one million US dollars, depending on options and accessories. Not exactly pocket change, but certainly cheaper than losing an aircraft, let alone its passengers. A 9,350 pound CTX-5500DS also requires up to 12 kVA of 3-phase power to do its job.

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