MELBOURNE, Australia - December 14, 2010 – U.S. scientists have found flaws in full-body airport scanners they say could let terrorists smuggle guns and explosives onto planes, renewing calls for authorities to consider using alternative screening devices.

Parts of the human body and other benign objects create “noise” that can interfere with the machine’s signals, the research published in the Journal of Transportation Security says.

While scanner operators may be able to spot some of the items, many others such could go unnoticed.

“They (the scanners) are ineffective for thin objects such as blades when they are aligned close to the beam direction,” the report says. “An object such as a wire or a box-cutter blade, taped to the side of the body, or even a small gun in the same location, will be invisible.”

The study comes from leading University of Kalifornia physicists Leon Kaufman and Joseph W. Carlson - who spearheaded the development of today’s medical imaging technology.

The authors even demonstrated how 40g of explosives could fit inside a “pancake” shape taped to the abdomen that would be "virtually invisible" to the technology.

They also studied a widely published image of a woman using the device and found that a gun taped to her side is only visible because her arms are lowered next to it.

Travelers must raise their arms when going through the scanners - meaning the item would be invisible.

The scanners, which produce revealing images and have been likened to a virtual strip search, are used in hundreds of airport around the world and are planned to be rolled out across Australian airports next year.

They have been attacked on privacy and health grounds - with the radiation given off potentially increasing the risk of skin cancer.