The TSA uses such devices for screening in airports.
This article is from Slashdot, a popular science and technology website. In addition, the original journal article is attached.
Please notice that the article was published in the Journal of Transportation Security, which is available through University research libraries.
Some will probably question whether this information should have entered the public domain; however, that fact remains that it has already been broadcast.
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A paper by Leon Kaufman and Joseph W. Carlson in the Journal of Transportation Security asserts that x-ray backscatter machines are not very effective (PDF) even in their intended role. While carelessly placed contraband will be detected, the machines have glaring blind-spots and have difficulty distinguishing explosives from human tissue. As they write, 'It is very likely that a large (15–20 cm in diameter), irregularly-shaped, cm-thick pancake [of PETN explosive] with beveled edges, taped to the abdomen, would be invisible to this technology. ... It is also easy to see that an object such as a wire or a boxcutter blade, taped to the side of the body, or even a small gun in the same location, will be invisible.'"
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