Millimeter wave scanner
A millimeter wave scanner is a whole-body imaging device used for detecting objects concealed underneath a person’s clothing using a form of electromagnetic radiation. Typical uses for this technology include detection of items for commercial loss prevention, smuggling and screening at government buildings and airport security checkpoints. Several countries employ the scanners for security screening.
It is one of the common technologies of full body scanner used for body imaging; a competing technology is backscatter X-ray. Millimeter wave scanners themselves come in two varieties: active and passive. Active scanners direct millimeter wave energy at the subject and then interpret the reflected energy. Passive systems create images using only ambient radiation and radiation emitted from the human body or objects.
Recent studies have called the safety of this technology into question. A team led by Los Alamos National Laboratory found that although the forces these waves exert on double-stranded DNA are tiny, in certain circumstances resonant effects can unzip the DNA strands, tearing them apart. This creates bubbles in the strands that can significantly interfere with processes such as gene expression and DNA replication, which can create highly mutagenic states predisposing to neoplastic (i.e., cancerous) growths.
Clothing and many other materials are translucent in some EHF (millimeter wave) radio frequency bands. This frequency range is just below the (related) sub-millimeter terahertz radiation (or "T-ray") range.
With active scanners, the millimeter wave is transmitted from two antennas simultaneously as they rotate around the body. The wave energy reflected back from the body or other objects on the body is used to construct a three-dimensional image, which is displayed on a remote monitor for analysis.[dead link][non-primary source needed]
Historically, privacy advocates were concerned about the use of full body scanning technology because it used to display a detailed image of the surface of the skin under clothing, prosthetics including breast prostheses, and other medical equipment normally hidden, such as colostomy bags. These privacy advocates called the images "virtual strip searches". However, in 2013 the U.S. Congress prohibited the display of detailed images and required the display of metal and other objects on a generic body outline instead of the person's actual skin. One technology for displaying such generic body outlines is called Automatic Target Recognition (ATR) software. As of June 1, 2013, all full body scanners in use at U.S. airports have used ATR.
While the radiation itself cannot distinguish between private and non-private areas, software imaging technology can mask specific body parts. Proposed remedies for privacy concerns include scanning only people who are independently detected to be carrying contraband, or developing technology to mask genitals and other private parts. In some locations, travelers have the choice between the body scan or a traditional "patdown". In locations such as the UK and Australia, the scans are mandatory.
In the United States, the Transportation Security Administration (TSA) claimed to have taken steps to address privacy objections. TSA claimed that the images captured by the machines were not stored. On the other hand, the U.S. Marshals Service admitted that it had saved thousands of images captured from a Florida checkpoint. The officer sitting at the machine does not see the image; rather that screen shows only whether the viewing officer has confirmed that the passenger has cleared. Conversely, the officer who views the image does not see the person being scanned by the device. In some locations, updated software has removed the necessity of a separate officer in a remote location. These units now generate a generic image of a person, with specific areas of suspicion highlighted by boxes. If no suspicious items are detected by the machine, a green screen instead appears indicating the passenger is cleared.
Concerns remain about alternative ways to capture and disseminate the image. Additionally, the protective steps often do not entirely address the underlying privacy concerns. Subjects may object to anyone viewing them in a state of effective undress, even if it is not the agent next to the machine, or even if the image is not retrievable.
Claims that images are immediately destroyed were questioned after Indian film star Shahrukh Khan said that his image was circulated by airport staff at Heathrow in London. This comment appears to be a joke according to one UK media outlet, but reports of full-body scanner images being improperly and perhaps illegally saved and disseminated continue to emerge.
Possible health effects
The evidence regarding health concerns is mixed. While some research has attempted to dismiss fears based on the fact that active scanners emit millimeter wavelength radiation which is non-ionizing and thereby putatively less harmful, others have repudiated these claims to safety based on laboratory studies indicating clear mechanisms for decreased cellular lifespan and impaired genetic fidelity after exposure to millimeter wavelength radiation.
Recent studies have identified mechanisms for the effects of millimeter wavelength radiation on survival and lifespan associated with changes in the cellular membrane, gene expression, and signaling pathways controlling these features.
Another 2014 study found that millimeter waves can influence gene expression and consequently could affect the cell phenotypic properties.
Experiments using in vitro cell cultures, tissue models, as well as recent in vivo studies have demonstrated that these pulses can elicit cellular and molecular changes in exposed cells and tissues in the absence of thermal effects. A 2014 study demonstrated that intense, picosecond THz pulses induce phosphorylation of H2AX, indicative of DNA damage, and at the same time activate DNA damage response in human skin tissues, and intense THz pulses have a profound impact on global gene expression in human skin. Many of the affected genes have important functions in epidermal differentiation and have been implicated in skin cancer and inflammatory skin conditions.
A study featured in the Journal of Quantum Electronics in 2014 identified DNA damage to human blood leukocytes caused by terahertz radiation.
A team led by Los Alamos National Laboratory found that although the forces that terahertz waves exert on double-stranded DNA are tiny, in certain circumstances resonant effects can unzip the DNA strands, tearing them apart. This creates bubbles in the strands that can significantly interfere with processes such as gene expression and DNA replication.
The same increase also occurs in chronically-stressed animals not exposed to radiation. One study has found that exposure to millimeter wave radiation reduces metastasis of tumor cells, but this study used waves of a different frequency (42.2 GHz) than that used in millimeter wave scanners .
The efficacy of millimeter wave scanners in detecting threatening objects has been questioned. Formal studies demonstrated the relative inability of these scanners in detecting objects—dangerous or not—on the person being scanned. Additionally, some studies suggested that the cost–benefit ratios of these scanners is poor. As of January 2011, there had been no report of a terrorist capture as a result of a body scanner. In a series of repeated tests, the body scanners were unable to detect a handgun hidden in an undercover agent's undergarments.
Millimeter wave scanners also have problems reading through sweat, in addition to yielding false positives from buttons and folds in clothing. Some countries, such as Germany, have reported a false-positive rate of 54%.
While airport security may be the most visible and public use of body scanners, companies have opted to deploy passive employee screening to help reduce inventory shrink from key distribution centers.
As of April 2009, the U.S. Transportation Security Administration began deploying scanners at airports, e.g., at the Los Angeles International Airport (LAX). These machines have also been deployed in the Jersey City PATH train system. They have also been deployed at San Francisco International airport (SFO), as well as Salt Lake International Airport (SLC), Indianapolis International Airport (IND), Detroit-Wayne County Metropolitan Airport (DTW), Minneapolis-St. Paul International Airport (MSP), and Las Vegas International Airport (LAS).
Three security scanners using millimeter waves were put into use at Schiphol Airport in Amsterdam on 15 May 2007, with more expected to be installed later. The passenger's head is masked from the view of the security personnel.
The federal courthouse in Orlando, Florida employs passive screening devices capable of recording and storing images.
Kelowna International Airport in Kelowna, British Columbia hosted the first such device in a Canadian airport. It was pulled from service in 2008 for undisclosed reasons, but may have simply been a test unit on loan.
Scanners are currently in use at Pearson Airport in Toronto, Ontario (YYZ), Montréal – Pierre Elliott Trudeau International Airport, Quebec (YUL), Calgary International Airport, Alberta (YYC), Vancouver International Airport, British Columbia (YVR), Halifax Stanfield International Airport, Nova Scotia (YHZ), and the Winnipeg James Armstrong Richardson International Airport (YWG).
The Canadian Air Transport Security Authority held a trial of the scanners at Kelowna International Airport in 2008. Before the trial, the Office of the Privacy Commissioner of Canada (OPCC) reviewed a preliminary Privacy Impact Assessment and CATSA accepted recommendations from the OPCC. In October 2009, an Assistant Privacy Commissioner, Chantal Bernier, announced that the OPCC had tested the scanning procedure, and the privacy safeguards that CATSA had agreed to would “meet the test for the proper reconciliation of public safety and privacy”. In January 2010, Transport Canada confirmed that 44 scanners had been ordered, to be used in secondary screening at eight Canadian airports. The announcement resulted in controversies over privacy, effectiveness and whether the exemption for those under 18 would be too large a loophole.
The Ninoy Aquino International Airport in Manila installed body scanners from Smiths in all four airport terminals in 2015.  The scanners are not yet in use, and are controversial among some airport security screeners. 
Scanners can be used for 3D physical measurement of body shape for applications such as apparel design, prosthetic devices design, ergonomics, entertainment and gaming.
- Backscatter X-ray (in security scanning applications)
- Explosives trace-detection portal machine (puffer machine)
- Full body scanner
- Security theater
- Electromagnetic radiation
- Extremely high frequency
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Remember Homeland Security told the public the scanners aren’t capable of storing images? Someone forgot to tell the scanner at the federal courthouse in Orlando…
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But two of Europe's largest countries, France and Germany, have decided to forgo the millimeter-wave scanners because of false alarms triggered by folds in clothing, buttons and even sweat.
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In Germany, the false positive rate was 54 percent, meaning that every other person who went through the scanner had to undergo at least a limited pat-down that found nothing. Jan Korte, a German parliament member who focuses on homeland security, called the millimeter-wave scanner "a defective product."
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