It seems that some of the best thinking on these millimeter wave machines is that they are not a panacea, and require more detailed evaluations before we spend too much money on them.

The National Academies’ 2007 National Academies Press publication, Assessment of Millimeter-Wave and Terahertz Technology for Detection and Identification of Concealed Explosives and Weapons, states in the Executive Summary that

1. The technology base for millimeter-wavelength/terahertz security screening is expanding rapidly internationally, yet there is insufficient technology available to develop a system capable of identifying concealed explosives.
2. Millimeter-wavelength/terahertz technology has potential for contributing to overall aviation security, but its limitations need to be recognized. It will be most effective when used in conjunction with sensor technologies that provide detection capabilities in additional frequency regions.

They go on to summarize recommendations, including, that

The TSA should commence developmental and operational testing of millimeter-wave-based portals to assess their effectiveness and suitability.

The TSA should follow a two-pronged investment strategy:
• Focus on millimeter-wave imaging as a candidate system for evaluation and deployment in the near term, and
• Invest in research and development and track national technology developments in the terahertz region.

Given recent events, I hope the news media are talking to the authors of this report, which contains some of the best current thinking on this technology.