In Part 4 of our weeklong series examining the use of backscatter x-ray machines in airport security, Leslie Shapiro doesn't pull any punches. Her Shift takes on the new technology in detail — and spells out exactly what we should be worried about. For the previous installments, look in this spot, this other location, and right over here.

In February 2007, the Transportation Security Administration (TSA) started using backscatter x-ray technology at Phoenix's Sky Harbor Airport, with LAX and JFK coming soon. SmartCheck, an x-ray backscatter system, uses a low-intensity beam that quickly scans a person, revealing any items hidden on his or her body. It works by detecting the reflection of the beam versus what is absorbed. The amount of radiation is negligible — according to the TSA — equivalent to the exposure you would get standing outdoors for approximately 15 minutes. Backscatters can detect metal weapons and explosives as well as nonmetallic items like concealed liquids, which typical airport metal detectors ignore. Sounds great, right? Well, sort of.

The technology, in addition to revealing items on the body, also reveals explicit details of the body. This is the x-ray machine every teenage boy fantasizes of — instead of showing just a skeleton, x-ray backscatter technology sees through clothing, revealing a realistically vivid image of the virtually naked body, with every lump, bump, bulge and ripple exposed.

The output of the backscatter scanner is quite detailed, and graphically so. There's no doubt that a man is a man. You could probably determine his religion. The director of the TSA's security lab volunteered to have her image scanned, and you can tell what type of underwear she's wearing, just from where it pinches her belly. The world has enough problems with visible panty lines, but invisible panty lines?

Don't get me wrong. Most people are disturbed when at 35,000 feet, the guy in 37D pulls out a Glock. It's going to be a bumpy ride. That's far more disturbing than, for example, the guy's love handles. But, at some point, you must choose between an acceptable risk and an invasion of privacy. Especially when they're your love handles.

In an effort to appease the public, AS&E, Inc., the company that developed and sells the SmartCheck scanners to the TSA, has added an optional privacy filter algorithm that it claims will protect the identity of screened passengers by blurring the outline of the body. The image resembles a police chalk outline, or as AS&E says, the image a child would produce by tracing their hand (though I don't think most kids include butt cheeks in their refrigerator art).

To provide "privacy," the agent viewing the image will be located in a separate isolated location, so they won't be able to match your face with your body. Personally, I don't think most people will give a damn if the screeners know what their face looks like — they just don't want them counting dudes' testicles, let alone knowing what type underwear they're wearing. Or not wearing.

But wait, there's another layer of protection: authorities claim that the SmartCheck systems will not store, print, or transmit images, so there's no fear of your image, or Britney Spears' image, appearing on the Internet. Well, their system doesn't store images, but who's to say that an enterprising TSA agent won't snap a shot with their cell phone? So what if they can't see that it's Britney — they will see that it's a hottie in a thong, close enough. On the other hand, the Rapiscan Secure 1000, used in London's Heathrow Airport does not have the privacy filter, and it can store images to hard disk or a floppy, for "training purposes." Uh-huh.

What's the difference between a latex glove strip search, and a backscatter virtual strip search of your body? Even if you're an extrovert, this is going a bit too far. What about more conservative folks? Will the Amish have problems? Religious orthodox? Sure, at the moment, a traditional pat-down is still an option, but in the future, who knows? Security is one thing, but how far should it go when it strips away personal dignity and privacy?

This technology is ideal for use in prisons, where certain rights to privacy have been surrendered after being convicted of a crime, but what crime did the average citizen commit? Too many doughnuts? Too much silicon? Would a well-endowed woman be singled out for extra screening? Rooms full of federal agents staring at images of naked passengers conjures up thoughts that are just downright scary. But, is it scarier than the threat of terrorism? The question is, what are you willing to give up to improve your own safety? Personally, I just want to keep my clothes on — real and virtually. — L.S.

An audio engineer based in Atlanta, Leslie Shapiro has been covering consumer electronics for almost a decade. Her work has appeared in many publications, including Sound & Vision, Crutchfield Advisor, and How Stuff Works as well as AOL. A longtime consultant and legal advisor for the electronics industry, she has a penchant for Bianchi and Colnago Italian bikes, and her favorite word is "synchronicity."