The effect of image enhancement functions on x-ray detection performance

State-of-the art x-ray screening systems offer a variety of so-called “image enhancement” functions (IEFs). Examples are color inversion, edge-enhancement, organic only, metal only etc. IEFs are often promoted because they would bring out detail that is obscured or highlight certain features, such as for example organic content. In this study, we investigated the usefulness of IEFs for cabin baggage screening (CBS) and hold baggage screening (HBS). For CBS, the standard image and nine IEFs have been tested with 443 x-ray screeners that completed a standardized x-ray image interpretation test using Smiths-Heimann HISCAN 6040i x-ray imagery (X-Ray CAT, Koller & Schwaninger, 2006). The results showed that the standard image provided the best detection performance. Some IEFs impaired detection performance substantially if images were displayed only with one IEF, which was also dependent on threat type (guns, knives, improvised explosive devices, other threat items). A second experiment with 83 HBS screeners using a bomb detection test, Smiths-Heimann HISCAN 10080 2i imagery, and 5 IEFs showed similar results. Together with previous work conducted with Rapiscan images (Klock, 2005), these results highlight the importance of systematically studying the usefulness of IEFs in order to optimize human-computer interaction in x-ray screening.