The panel concluded that the images produced by these technologies are of sufficiently high quality to make them effective for screening passengers. However, when the perceived level of threat is low, passengers, crews, and others passing through screening checkpoints are likely to object to having images of their bodies displayed. There are also likely to be concerns about the use and storage of the data used to generate images. Procedures, such as having operators of the same sex view the images or moving operators away from the screening checkpoints, could allay concerns. However, for financial and logistical reasons, these procedures are likely to make imaging technologies extremely unattractive for use as primary screening systems at all checkpoints. Quantifying the level of threat at which people are likely to accept this kind of invasion of privacy is difficult but necessary prior to mandating the use of any imaging technology for screening passengers at airports.3

The resolution of privacy issues in other countries is not likely to be relevant to the resolution of these issues in the United States because local attitudes and perceptions determine the issues of privacy to be addressed. In practice to date, many of these issues are solved via the operational protocols adopted by various countries. For example, only male operators screen males, and females screen females. The person screening is remote and does not see the subject, and vice versa. Also, software allows for various measures of privacy and automatic target detection. Finally, imaging allows for “directed search,” which means that in place of a full pat-down, the person has to explain or show only what is in a specific area, typically a pocket.

Decisions on such issues will have to be made prior to a deployment of these imaging technologies. For this report, the committee limited its review to the technical issues that would move these technologies closer to implementation, without considering the public’s acceptance of the deployed technology.

A field trial to gauge both feasibility and public acceptance of such technology was conducted by QinetiQ at Gatwick Airport and summarized as follows: “The results of this trial indicated that public reaction to the possible introduction of this technology into UK airports has been favorable, and that the performance of this imager in detecting specific threat items concealed on passengers, such as metal or ceramic weapons has been very encouraging.”4

Cost Issues

In the past decade, the cost reductions and performance improvements of devices to generate, control, and detect radiation in the spectral region millimeter-wavelength/ terahertz made detection systems viable for checking baggage and scanning people. However, a reasonable and affordable initial cost is only part of the total life-cycle cost of a deployed operating system. There are other recurring and nonrecurring costs over the lifetime of the system that will likely exceed the initial purchase price. The following are


National Research Council. 1996. Airline Passenger Security Screening: New Technologies and Implementation Issues. National Academy Press, Washington, D.C.


H. Oman, ed. 2003. Conference Report: 36th International Canahan Conference on Security Technology. IEEE AESS Systems Magazine 18(4): 28-40.

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