Backscatter X-ray

Backscatter X-ray 

is an advanced X-ray imaging technology. Traditional X-ray machines detect hard and soft materials by the variation in transmission through the target. In contrast, backscatter X-ray detects the radiation that reflects from the target. It has potential applications where less-destructive examination is required, and can be used if only one side of the target is available for examination.
The technology is one of two types of whole body imaging technologies that have been used to perform full-body scans of airline passengers to detect hidden weapons, tools, liquids, narcotics, currency, and other contraband. A competing technology is millimeter wave scanner. An airport security machine of this type is also referred to as "body scanner", "whole body imager (WBI)", "security scanner", and "naked scanner"

Deployments at airports

In the United States, the FAA Modernization and Reform Act of 2012 required that all full-body scanners operated in airports by the Transportation Security Administration use "Automated Target Recognition" software, which replaces the picture of a nude body with the cartoon-like representation. As a result of this law, all backscatter X-ray machines formerly in use by the Transportation Security Administration were removed from airports by May 2013, since the agency said the vendor (Rapiscan) did not meet their contractual deadline to implement the software.
In the European Union, backscatter X-ray screening of airline passengers was banned in 2012 to protect passenger safety, and the deployment at Manchester Airport was removed.

 

Technology

Backscatter technology is based on the X-ray Compton scattering effect of X-rays, a form of ionizing radiation. Unlike a traditional X-ray machine which relies on the transmission of X-rays through the object, backscatter X-ray detects the radiation that reflects from the object and forms an image. The backscatter pattern is dependent on the material property, and is good for imaging organic material.
In contrast to millimeter wave scanners which create a 3D image, backscatter X-ray scanners will typically only create a 2D image. For airport screening, images are taken from both sides of the human body.
Backscatter X-ray was first applied in a commercial low dose personnel scanning system by Dr. Steven W. Smith. Dr. Smith developed the Secure 1000 whole body scanner in 1992 and then sold the device and associated patents to Rapiscan Systems who now manufactures and distributes the device.