Travelers, be aware: Your full-blown image — private parts and all — could soon be visible to a security officer, on-screen, at an airport near you.

Miami International Airport is one of a dozen airports nationwide that have begun pilot-testing whole-body imaging machines, which reveal weapons and explosives concealed under layers of clothing.

"It allows us to detect threat objects that are not metallic and that cannot be detected by metal detectors, and items that are sometimes missed even in a physical pat-down, in a nonintrusive manner," said Mark Hatfield, federal security director for the Transportation Security Administration at MIA

As passengers step inside the machine, they extend their arms and legs for several seconds, as millimeter wave technology creates an image. About 25 feet away, in a covered booth, a security officer in radio contact, views the ghostly silhouette -- with the face blurred -- on a screen. The officer determines if a concealed weapon, such as a ceramic knife, or explosive detonation cord, exists, Hatfield said.

''The image projected is more humanoid than human,'' he said. "What's important is providing a clear view of a threat object. And the person going through the machine will never see the operator.''

'RANDOM SELECTION'

So far, the technology has been used for five days at two MIA checkpoints, at Concourses G and J, replacing the machines that emitted puffs of air. At least two more body-imaging machines will be deployed in the next few months, one at J and one at an interim checkpoint at C/D, Hatfield said. Each machine costs $170,000. To date, no explosives have been detected, he said.

At least for now, the TSA is using ''continuous, random selection'' to choose passengers for the machines, and it is optional. Travelers who decline will be physically patted down. All passengers must still go through metal detectors.

''For our travelers, through this airport, this machine adds even an additional layer of security,'' said Miami-Dade Aviation spokesman Marc Henderson.

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