The first sheet from Rapiscan's patent 7,796,733, entitled "Personnel security screening system with enhanced privacy" is shown. According to the patent document, the invention "relates to image processing techniques that employ maximum threat detection performance and minimal information loss. More particularly, the invention relates to the field of radiant energy imaging systems and methods and to image processing techniques for detecting concealed objects carried on the body or clothing of a person without compromising the privacy of the person." A further explanation delves into how contraband can be detected by X-rays: "Non-metallic objects are commonly composed of low atomic number elements similar to those of human tissue, i.e. hydrogen, carbon, nitrogen, and oxygen. Soft human tissue scatters a significant amount of X-rays due to the relatively low atomic number of hydrogen, carbon, and oxygen in relatively high concentration. Due to the high atomic number of calcium, bones near the surface of the body, comprised mainly of calcium, produce much less scatter. Concealed objects, especially metals, can be easily visualized in the images due to their significant difference in atomic composition from the background of human tissue."
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