Patent ID: 7092485

Claim:
A system for screening an interrogation volume within a baggage item for the presence of at least one contraband substance, the system comprising: a. an x-ray source adapted to emit penetrating, polychromatic radiation; b. a primary beam collimator adapted to limit the radiation emanating from said x-ray source to a primary fan beam that opens at a fan angle, circumscribes a primary beam direction, and is incident on said interrogation volume; c. a dual-energy detection system, comprising at least a low-energy x-ray detector and a high-energy x-ray detector, each detector being positioned to intercept and detect radiation in said primary fan beam transmitted through said baggage item; d. an energy-resolved x-ray detector for detecting radiation coherently scattered from said primary fan beam at a plurality of scattering angles by material within said interrogation volume, material in each portion of said interrogation volume producing scattered radiation detected at each of said plurality of scattering angles; e. computer means operably associated with said dual-energy detection system and said energy-resolved x-ray detector, said computer means being adapted to: i. determine an energy-dependent absorption correction from the output of said dual-energy detection system; ii. produce an energy-resolved scattering spectrum for each of said scattering angles from the output of said energy-resolved x-ray detector; iii. correct each of said energy-resolved scattering spectra using said energy-dependent absorption correction to produce a corrected spectrum for each of said scattering angles; iv. combine said corrected spectra to produce a diffraction scattering pattern; and v. compare said diffraction scattering pattern with the reference diffraction scattering pattern of at least one known contraband substance stored in said computer means to detect a match indicative of the presence of said known contraband substance in said interrogation volume; and f. a signal means associated with said computer means, said signal means being activated in response to the detection of said match.