Backscatter X-ray
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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 in which only one side is available for examination.
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[edit] History
The discovery of x-ray in 1895 by Wilhelm Röntgen allows us to view the body or substance that's concealed beneath a layer of clothing, skin...etc. (EPIC). It was then put to use in hospitals to examine patients with and it was not until recent years when the new type of x-ray, the backscatter x-ray, was developed and tested. The three-month trial "began in the Pheonix Sky Harbor International Airport on February 23, 2007" (EPIC).
[edit] The technology
The resolution of the resulting images is quite high. Some backscatter X-ray scanners are able to penetrate up to 30cm (~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, for example [1]. In comparison to x-rays from medical applications, the backscattered x-rays are considered high energy and usually scatter instead of penetrate materials (EPIC). 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 (EPIC).
[edit] Privacy concerns
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 and other items. The ACLU and the Electronic Privacy Information Center are opposed to this use of the technology, the latter organization calling it a "virtual strip search". However, it is currently in use at Phoenix Sky Harbor International Airport. It is "possible for backscatter X-raying to produce photo-quality images of what's going on beneath our clothes," thus the images have been distorted with the private parts being blurred (Layton). Further distortion is used in the Pheonix airport's trial system where photo-quality images are replaced by cartoon-like outlines (Layton). Salatan, William. "Digital Penetration", Slate.</ref>
[edit] Other concerns
While the privacy issue is the main concern, it certainly raises doubt about how effective this system is. Privacy concerns have caused private parts in the image to be blurred; however, this may allow people to carry weapons or certain explosives aboard by attaching the object or substance to their private parts (Layton). The other issue is the radiation exposure. At airports, lead vests are not used and people fear being exposed to "dangerous level of radiation if they get backscattered too often" (Layton). The Health Physics Society (HPS) reports that a person undergoing a backscatter scan receives approximately 0.005 millirems of radiation in comparison to the 0.009 millirems reported by American Science and Engineering Inc. (Layton). According to the U.S. regulatory agencies, "1mrem 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" (Layton).
[edit] References
Layton, Julia. "Do "Backscatter" X-Ray Systems Pose a Risk to Frequent Fliers?" HowStuffWorks. 27 Feb. 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.howstuffworks.com/framed.htm?parent=backscatter.htm&url=http://www.epic.org/privacy/airtravel/backscatter/>.
[edit] External links
- You are undie surveillance UK considers using backscatter X-ray machines to scan the public.
- New airport X-ray is a virtual strip search U.S. Transportation Security Administration began testing of an X-ray backscatter machine for secondary testing on volunteer passengers.
- Screening Individuals with Backscatter X-ray Systems (Discussion of x-ray dose)
- American Science and Engineering - pioneers in the field.
- University of Florida Reseach - High Resolution Scatter X-ray Imaging
- Rapiscan Systems - Manufacturer of the SECURE 1000 People Screening System
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