Features of X-ray CT Imaging

X-ray computed tomography (CT), initially developed for medical diagnostics, is now also being used extensively in airports, worldwide, to find hidden explosives in checked airHne luggage. The population of CT systems deployed at US airports as ofjanuary, 2008, numbers more than 1700. 

CT images provide a large amount of detailed information about each individual object packed in articles of luggage. This information is not available in images produced by conventional X-ray scanners. 

This chapter discusses the features of CT imaging and outlines how the images are formed. Several different technical approaches are described along with examples. Finally, issues to be considered in designing luggage scanners are presented. 

CT is an X-ray imaging technique that has unique capabilities in security apphcations. Presently, its main use in the security arena is to locate hidden explosives in airline luggage. It can also be used for finding other contraband material. 

In locating contraband the CT approach has two major advantages over conventional X-ray imaging. First, and most importantly, it can measure and record, unambiguously, the material property of individual objects packed in a bag. The quantity is the X-ray attenuation coefficient, which is proportional to a material s 

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