The Transportation Security Administration put the body-scanning machines into use at airports in Los Angeles, Albuquerque, Denver, Baltimore, Las Vegas, Dallas, Detroit, Miami, New York and the Reagan National Airport in Washington, D.C., last month.

The scanners, which are meant as an alternative to the traditional pat-down as a secondary screening for randomly selected passengers, use military wave imaging technology to detect weapons, explosives and other threatening objects hidden beneath layers of clothing.

The travelers enter one-by-one into 9-by-6-foot glass booths that close around them.

A three-dimensional image of their bodies – beneath their clothing – is then taken by two antennas that simultaneously rotate around them.

According to the TSA’s Web site, electromagnetic waves are used to "generate an image based on the energy reflected from the body.

Active millimeter wave technology passes harmless electromagnetic waves over the human body to create a robotic image."

A TSA security official views this image in black-and-white on a viewing station in a nearby room. The screener looks for objects in the image that are shaded differently from the rest of the body. If he or she finds something suspicious, a fellow officer at the checkpoint is radioed.

The TSA says it has applied a security algorithm to the images to blur the face of the passenger; the screener will, therefore, be unable to ascertain the identity of the person whose body image he or she is viewing.

The images will also be deleted immediately after being viewed, according to TSA spokespersons, and the officer conducting the screening will never see the computer image. However, the scans are detailed, and the images of the almost-naked bodies display intimate body parts and clearly reveal the person’s gender.

Civil rights advocacy groups such as the Council on American-Islamic Relations and the American Civil Liberties Union have issued statements warning of the graphic nature of these images.

The ACLU refers to the scans as a "virtual strip search," and does not think that blurring the passengers’ faces in the images redeems their loss of privacy.

"It’s the equivalent of making passengers parade through a room naked with a bag over their heads which is not something that people would agree to do," said ACLU staff attorney Peter Bibring. "The fact that the faces are blurred does not completely resolve all the privacy and dignity concerns."

Bibring also said he believes there may be a strong temptation to reveal a person’s identity or preserve an image in cases of passengers of public importance or of passengers with distinguishing physical features.

"We want American Muslims and others who care about their privacy to be aware of the detailed images these scanners provide and know that travelers have the option of requesting a private pat-down by a security officer of the same gender instead of going through the machine," said Ameena Qazi, a staff attorney with the Council on American-Islamic Relations - Greater Los Angeles Area.

Female and male TSA officers who view the images from the scanning machines in a separate room are not just assigned to images of their respective gender.

Dr. Saba Chughtai, a psychiatrist in Mason, Ohio, said she does not believe that modesty is an issue with these body scanners.

"I think it’s pretty impersonal," Chughtai said. "The security officials are looking at someone’s anatomy, but it’s not in [a suggestive] sense. They’re really looking for any hidden objects to make people more secure."

She says she would be more concerned with whether officers were not going to delete certain images and discriminate against people with certain identifiable physical features.

In addition to their concerns about the images themselves, the civil liberties organizations question whether the passenger is being given enough information to make a qualified decision to be subject to a scan by the machines.

"We have started to receive reports that passengers may not fully be informed about the nature of images these scanners produce," Qazi said, "We’ve also been informed that the authorities may not be in a position to quickly accommodate travelers’ request for a pat-down by a security officer of their gender, if they so request."

Qazi said CAIR is in the process of requesting a meeting with appropriate government agencies regarding the scanners.

At the Baltimore/Washington International Airport, magazine-sized posters explain the scanners to people standing in line. But TSA spokesman Sterling Payne told USA Today that the agency was trying to get "more creative" about informing passengers about the machines.

While CAIR and ACLU are joining other organizations in calling on the TSA to execute programs to fully inform passengers of the privacy implications associated with the scanners, some ACLU officials doubt the effectiveness of this new security measure in the first place.

"To the extent that these scanners are only now in the busiest airports, they’re unlikely to deter any terrorists," Bibring said. "I mean, if you say that what you’re looking for is someone who is determined to smuggle something dangerous onto a plane in order to wreak havoc, they’re simply going to go to an airport that doesn’t have these [machines] in place. And by installing them at the nation’s busiest airports, you’re not really increasing security; you’re just targeting a large number of lawful passengers."

CAIR is requesting community members, who have been through the body scanners, to report any concerns about the procedure or to get more information on the issue.