"According to TSA’s threat assessment, terrorists have various techniques for concealing explosives on their persons, as was evident in Mr. Abdulmutallab’s attempted attack on December 25, when he concealed an explosive in his underwear," Lord said. "While TSA officials stated that the laboratory and operational testing of the AIT included placing explosive material in different locations on the body, it remains unclear whether the AIT would have been able to detect the weapon Mr. Abdulmutallab used in his attempted attack based on the preliminary TSA information we have received."
Kaufman and Carlson, however, didn't evaluate whether backscatter technology, which uses low-level X-rays to create a two-sided image of a passenger, poses any health risks. The TSA stresses emphatically (here and here) that backscatter technology poses no radiation risks to the traveling public and provides links to independent studies confirming this.
♦ Photo of backscatter image by Department of Homeland Security/WikiMediaCommons