Sept. 28, 2001

Airport security looks to Laboratory for expertise on X-ray imaging methods

In the Engineering directorate, Harry Martz is the director of the Center for Nondestructive Characterization (CNDC), but he has found himself in the national spotlight recently as a member of the National Academy of Science (NAS) Committee on Assessment of Technology Deployed to Improve Commercial Aviation Security.

Martz has served on the committee and several of its specialty panels since 1995, contributing to its ongoing recommendations to the Federal Aviation Administration (FAA) concerning X-ray imaging methods. The CNDC uses these technologies for various industrial and stockpile stewardship missions, such as highly detailed, multi-dimensional X-ray images of weapons parts, engine parts and the molds to cast them.

It is these same nondestructive evaluations, as well as some others, that are the emerging technologies in airport screening of passengers, cargo, and checked luggage and carry-on bags.

Martz’ expertise has recently contributed to airport security articles in The Wall Street Journal, San Francisco Chronicle, The New Yorker magazine and other regional publications. Martz is also featured in an upcoming article in the science journal, Nature. Additionally, two separate television crews from TechTV network, based in San Jose, recently spent time interviewing Martz for news and feature programs.

When Martz talks to the media, he addresses the committee’s study of "new technologies in passenger, baggage and cargo scanning using thermal and X-ray scanning, industrial CT scans, and the hardware and software to help run them."

The industrial CT scans, similar to those used by the CNDC here at LLNL, take multi-dimensional X-ray radiographic images, reconstructing them and giving the operator a clearer picture of the items within a bag.

"Some items can be very difficult to detect if they are at a head-on angle to the X-ray source," said Martz. "A knife and a metal ruler could be virtually indistinguishable from the end."

One of the more promising new scanning methods Martz describes is that of X-ray backscatter, a low-energy and low-dose X-ray that penetrates the clothing, but not the body and reflects X-rays back toward the source. Once detected, it provides an image of concealed objects. This eliminates the need to have X-rays pass through the body and greatly reduces the amount of X-ray exposure.
"Amount of exposure is one concern," Martz explained, "but the primary reason we haven’t seen this technology applied in commercial airports is lack of privacy. Flight attendants and others have expressed fear that the detailed images emerging from beneath one’s clothing may be misused."

X-ray backscatter scanners are currently in use in a few U.S. prisons, where, according to Martz, they have been very useful as an alternative to the traditional pat-down search of both prisoners and visitors to the prisons.

Now that many Americans have higher airport security concerns, Martz believes that the Commercial Aviation Security Committee and the FAA may reconsider the backscatter technology, "It is very accurate," Martz said, "You really can’t hide anything under your clothes."