Better Cargo Inspection Standards at Border Crossings

An x-ray image showing a standard test object (upper left) held aloft by support apparatus and a forklift. In this case, the test object is a wedge of steel with steps of various thicknesses. Though NIST's intention in this study was to evaluate the test objects and not to inspect vehicles, the x ray of the forklift gives a viewer a sense of the system's imaging capabilities. Note the circular object at right, the gas tank, which is half full.

As part of an Interagency Agreement between NIST and the Department of Homeland Security (DHS), PML's Radiation Physics Division recently completed a series of image quality measurements of a high-energy x-ray vehicle-screening system at a newly constructed port-of-entry near El Paso, TX.

The four step wedges used as test objects in the study.

In their study, researchers compared the performance of two image quality standards – ANSI N42.46 and IEC 62523* – for cargo and vehicle screening systems. The purpose of the work was to provide feedback on the practical use of the two standards and recommend possible improvements, with a goal towards harmonization.

Key findings from the image quality tests were summarized in an interagency report to DHS. Recommendations included a design change to objects used in the IEC test, the addition of a material discrimination test method for the ANSI standard, and a provision to include blind testing to improve the objectivity in both standards.

*These standards are recommendations by the American National Standards Institute (ANSI) and the International Electrotechnical Commission (IEC).

-- Reported and written by Jennifer Lauren Lee

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