In contrast to the traditional X-ray machine, which detects hard and soft materials by the variation in transmission through the target, backscatter X-ray is a newer imaging system which detects the radiation which comes back from the target. It has potential applications in almost every situation in which non-destructive examination is required, but only one side is available for examination. One application currently under exploration is to perform a security scan of airline passengers.
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The technology
The resolution of the resulting images is quite high. Some backscatter X-ray scanners are able to penetrate up to 30 cm (~12") of solid steel. As such, the technology is in use to search containers and trucks much more quickly than performing a physical search, and potentially allow a larger percentage of shipping to be checked for smuggled items or weapons. According to Farren Technology, the technology exists to scan areas as far as 50 meters away from the device, producing 3D images of people's bodies and the weapons they might be hiding. In comparison to x-rays from medical applications, the backscattered x-rays are considered high energy and usually scatter instead of penetrate materials. A "high energy x-ray beam" moves rapidly over the person's form and a high resolution image of the person's nude body is constructed when the scattered x-ray "from a known position" is detected.
Concerns
Privacy
The technology has been proposed as an alternative to personal searches at airport and other security checkpoints, since it can easily penetrate clothing and reveal concealed weapons; however, it raises privacy concerns in that it appears to screeners essentially as a nude picture of the subject, and may allow screeners to gain access to otherwise confidential medical information, such as the fact a passenger uses a colostomy bag.
The ACLU and the Electronic Privacy Information Center are opposed to this use of the technology, currently in use in the U.S. at 18 airports, 4 court houses, and a correctional facility.[1] The ACLU refers to backscatter x-rays as a "virtual strip search". Within an 10/11/07 TSA press release, the TSA announced that to date 79 percent of the public has opted to try backscatter over the traditional pat-down in secondary screening. TSA began using backscatter in February 2007.[2]
It is "possible for backscatter X-raying to produce photo-quality images of what's going on beneath our clothes", thus, according to the TSA, the images have been distorted with the private parts being blurred (Layton). According to the TSA further distortion is used in the Phoenix airport's trial system where photo-quality images are replaced by chalk outlines.[3][4] The TSA has also commented[citation needed] that setting up screening procedures such as having the screener viewing the image located far away from the person being screened could be a possibility.
In light of this, some journalists have however expressed concern that this blurring may allow people to carry weapons or certain explosives aboard by attaching the object or substance to their private parts.[5][6]
Health effects
Some people are concerned with exposure to radiation emitted by backscatter X-rays. At airports, lead vests are not used and people fear being exposed to "dangerous level of radiation if they get backscattered too often."[5]
The Health Physics Society (HPS) reports that a person undergoing a backscatter scan receives approximately 0.005 millirems of radiation; American Science and Engineering Inc. reports 0.009 mrems. [5] According to U.S. regulatory agencies, "1 mrem per year is a negligible dose of radiation, and 25 mrem per year from a single source is the upper limit of safe radiation exposure."[5].
See also
References
- ^ TSA: Millimeter Wave
- ^ TSA: TSA Tests Second Passenger Imaging Technology at Phoenix Sky Harbor Airport
- ^ TSA privacy FAQ
- ^ Salatan, William. "Digital Penetration". Slate. http://www.slate.com/id/2160977/.
- ^ a b c d Layton, Julia. "Do "Backscatter" X-Ray Systems Pose a Risk to Frequent Fliers?" HowStuffWorks. 27 February 2007. 18 Mar. 2007 <http://travel.howstuffworks.com/backscatter.htm>. "Backscatter" X-Ray Screening Technology." HowStuffWorks.
- ^ Electronic Privacy Information Center. 18 Mar. 2007 <http://www.epic.org/privacy/airtravel/backscatter/>.
External links
- You are undie surveillance UK considers using backscatter X-ray machines to scan the public.
- American Science and Engineering - pioneers in the field.
- University of Florida Research - High Resolution Scatter X-ray Imaging
- Rapiscan Systems - Manufacturer of the SECURE 1000 People Screening System
- Backscatter X-ray technology and risks
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