Review articleImaging in airport security: Past, present, future, and the link to forensic and clinical radiology
Introduction
The concept that societies seek to protect their key assets has not changed in the course of the centuries. However, the nature of these assets, as well as the means employed for protection against enemies, evolved dramatically. One piece of critical infrastructure in our modern society is personal transportation, the most effective one being transportation by air. It is therefore not surprising that our society devised a protection scheme for air transportation that employs the best and newest technology available.
In the era before 1972, Security Officers (SOs) at airports performed hand searches for baggage that was to be taken on board of airplanes. As air traffic increased, this proved more and more difficult, especially at peak times, considering that a thorough hand search of one piece of cabin baggage might take several minutes. In order to increase both the security level and the processing capacity of the security control, Peil constructed an “Apparatus for baggage inspection” that included “an x-ray and fluoroscopic examination unit”, which was patented in 1972 [1]. This patent marked the beginning of a new era in security control at airports, in which imaging was to play a key role. At first, security professionals applied this technology without much knowledge of what x-ray image interpretation requires from the human operators at airports. In 1990, however, the United States decided that aviation security should be improved through the optimization of human factors elements [2], because it had become clear that the best possible imaging device only fulfills its purpose in combination with proficient screeners that are able to interpret the images correctly and efficiently. This marks the starting point for the development of a substantial body of research in human factors in x-ray screening in airport security. It further prepared the grounds to the later development of sophisticated training and certification methods for x-ray screeners who work at airport security control checkpoints.
Section snippets
Screening of baggage
European law requires that all passengers as well as all their cabin baggage and hold baggage items undergo screening [3]. Most European airports have dual-energy x-ray systems in place in order to screen cabin baggage. These are either single or dual-view systems that provide the operator with one or two views (from different angles) of the baggage in pseudo-colors. The pseudo-colors should facilitate differentiation of materials, i.e., different colors represent different classes of
Imaging in airport security tomorrow
In the future, multi-view x-ray and CT technology for imaging in airport security will be developed further as the standards (i.e., minimum requirements), set by legislation for the devices used at airports, increase continually. Scanning times might become faster, resolution higher, and the costs of the devices lower. The trend also goes towards automated detection. Whereas for hold baggage, an automated first level of screening for explosives is already standard today, it can be expected
Interdisciplinary topics
The technology employed, the way of working, as well as the challenges encountered in imaging in airport security share similarities to forensic and clinical radiology. Vogel's pioneering work explains and illustrates different uses of imaging in security as seen from a radiologist's background [38], [39], [40], [41]. In order to more closely investigate interdisciplinary topics and links between these disciplines, the author performed a literature search in mid May 2013. The database PubMed
Conclusion
After an introduction on the beginnings of x-ray screening of baggage, this review article has given an overview of the state-of-the-art in imaging in security at airports as well as an outlook onto future developments in this area. It becomes evident that the two disciplines of imaging in airport security and forensic/clinical imaging can learn from each other. Apart from using the same technologies for imaging, research interests and initiatives converge in human factors aspects that are
Acknowledgements
The author cordially thanks Prof. Dr. Michael Thali, University of Zurich, for his kind support.
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