ARLINGTON, VA - DECEMBER 30: A volunteer stands inside a "millimeter wave" scanner during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. "Millimeter wave" passes electromagnetic waves over the body to create three-dimensional images that look like a photo negative. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. (Photo by Chip Somodevilla/Getty Images) Foto: Getty Images

ARLINGTON, VA - DECEMBER 30: A Transportation Security Administration officer guides a person through a "millimeter wave" scanner during a demonstration at the TSA's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. "Millimeter wave" passes electromagnetic waves over the body to create three-dimensional images that look like a photo negative. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. (Photo by Chip Somodevilla/Getty Images) Foto: Getty Images

ARLINGTON, VA - DECEMBER 30: Transportation Security Administration Security Officer Nyamsi Tchapleu looks at images created by a "backscatter" scanner during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. Backscatter technology uses low level x-rays to create a two-sided image. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. The TSA will roll out 150 backscatter scanners in 2010 and has budgeted for 300 additional imaging units. (Photo by Chip Somodevilla/Getty Images)

ARLINGTON, VA - DECEMBER 30: Transportation Security Administration Security Officer Nyamsi Tchapleu looks at images created by a "backscatter" scanner during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. Backscatter technology uses low level x-rays to create a two-sided image. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. The TSA will roll out 150 backscatter scanners in 2010 and has budgeted for 300 additional imaging units. (Photo by Chip Somodevilla/Getty Images)

ARLINGTON, VA - DECEMBER 30: Images produced by a "millimeter wave" scanner are displayed during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. "Millimeter wave" passes electromagnetic waves over the body to create three-dimensional images that look like a photo negative. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. (Photo by Chip Somodevilla/Getty Images) Foto: Getty Images

ARLINGTON, VA - DECEMBER 30: Images created by a "backscatter" scanner are displayed during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. Backscatter technology uses low level x-rays to create a two-sided image. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. The TSA will roll out 150 backscatter scanners in 2010 and has budgeted for 300 additional imaging units. (Photo by Chip Somodevilla/Getty Images)