Full Body Scanners: New detection technologies
Full body scanners are now the norm at many US airports. Working alongside metal detectors and baggage scanners, the giant machines help make air travel safer and more efficient.
Unlike traditional metal detectors where the machines only detect metal objects such as guns and knives, these full body scanners are able to detect anything that could be a potential threat. These machines are able to detect bombs made from organic matter and illegal drugs that passengers may be carrying (Mahesh).
The full body scanners use two main systems, backscatter x-ray technology and millimeter wave detection. Both of these systems use radiation to penetrate clothing to get an image of the body. In a baggage x-ray system, the device works like that of a medical x-ray. Strong radiation is given off by the machine that is connected to a screen which the agent then inspects. Backscatter x-rays however, use far less radiation and only measure the x-rays that are bounced back from your body or objects on the person (Mehta and Smith-Bendelman). Concealed items such as liquid bombs, ceramic knives or drugs would go undetected a typical metal detector but would show up in a backscatter machine. Millimeter wave detection works on a similar principle with rays transmitted out to your body and bounced back. The machine then makes a radar image of the body without the scary x-ray technology (Moulder).
Backscatter technology exposes the passenger to very minimal amounts of radiation. In comparison, a passenger would have to pass through the backscatter system 1000 to 2000 times before experiencing the same exposure as a chest x-ray. The TSA agents operating the machines face about 100 uSv of radiation per year which is far less than the safe health limit of 50,000 uSv per year (Zanetti-Fregonara).
Millimeter wave detection, on the other hand does not expose passengers to ionizing radiation but uses a form of electromagnetic radiation called millimeter waves. These waves lie in the spectral region between radio waves and infrared to obtain images. These advanced scanners beam low powered millimeter waves over the surface of the body using two rotating antennas. The energy reflected back from the machine is analyzed to create body images and located any questionable items (Hindie).
This new technology is considered as a more efficient security measure where they are being more commonly used in US airports. They are able to quickly view a passenger’s person with barely any harmful effects.
Figure 1: Backscatter image of passenger at an airport screening
Figure 2: Shows the comparison of backscatter radiation and millimeter wave detection to common radiation exposure
References
Mahesh, 2010 M. Mahesh Use of full body scanners at airports British Medical Journal (2010), p. 340 http://dx.doi.org/10.1136/bmj.c993 c993
Mehta and Smith-Bindman, 2011 P. Mehta, R. Smith-Bindman Airport full-body screening: what is the risk? Archives of Internal Medicine, 171 (12) (2011), pp. 1112–1115 http://dx.doi.org/10.1001/archinternmed.2011.105
Moulder, 2012 J.E. Moulder Risks of exposure to ionizing and millimeter-wave radiation from airport whole-body scanners
Radiation Research, 177 (6) (2012), pp. 723–726
Zanotti-Fregonara Zanotti-Fregonara Radiation risk from airport X-ray backscatter scanners: should we fear the microsievert?
E. Hindie Journal of Radiology, 261 (1) (2011), pp. 330–331 http://dx.doi.org/10.1148/radiol.11110983 author reply 331–332
