Backscatter X-ray technology is an advanced form of traditional X-ray scanning. It differs from traditional dual-energy systems by providing a far more comprehensive picture, particularly of organic material. Some controversy surrounds using backscatter X-ray scanners as a security measure, both for reasons of privacy and fears of radiation exposure.
Traditional X-rays create an image by measuring the amount of X-rays absorbed by an object undergoing detection. In medical usage, the reason bones are easier to see on an X-ray than skin or organs is that the composition of bones absorbs more X-rays. Backscatter X-ray technology, on the other hand, detect the reflection of the radiation from the object being examined.
Elements low on the periodic scale, such as hydrogen or carbon, scatter X-ray photons effectively rather than absorbing them, which makes them much less visible in traditional X-rays. Most of the soft tissues in the body are made up of these low-atomic weight elements, making X-rays fairly useless for examining organic material. Backscatter machines are considered far superior to traditional X-rays for examining soft tissue, since the reflection created by tissue is far more detailed than the picture given by absorption methods. Though medical facilities primarily rely on computer tomography or magnetic resonance imaging for examination of poor X-ray areas, backscatter has gained popularity in security pursuits.
The most prominent use of backscatter X-ray machines is in commercial airports. Put in place to detect concealed weapons or explosives, these machines can create a highly detailed two-dimensional picture of anyone who passes through the scanner. The downside to this procedure is that the image created is quite clear and removes the concealment of all clothing, creating, in effect, a naked picture of the target. This has led to a considerable outburst among civil liberty activists, religious leaders, and many people uncomfortable with the idea of a naked picture being taken and viewed by others, especially as the scanners have the capability to store and save images. In November 2010, over 100 backscatter X-ray images were leaked onto the Internet.
Some people have also raised concerns about the radiation exposure caused by using backscatter X-ray machines. When receiving a traditional X-ray at a medical facility, people are usually given a lead apron to protect them from the radiation. Most experts seem to agree that backscatter scanners present little danger, even for frequent fliers. According to some medical professionals, a person would have to undergo hundreds of X-rays per week in order to be in danger from the radiation.