Explosive material detection apparatus and method using dual energy information of a scan

A method of detecting an object in a region having a longitudinal axis, said object having at least a first physical characteristic and a second physical characteristic, said method comprising:

• A. scanning said region to generate scan data representative of said region, said scanning comprising:
• i. providing a radiation source alternately radiating at least at a first energy level and at a second energy level, and an array of detectors on opposed sides of said region;
• ii. rotating at least said radiation source about said longitudinal axis while said radiation source emits radiation toward said array of detectors;
• and,
• iii. with said array of detectors, receiving radiation from said region to generate said scan data at said first energy level and said second energy level for said region;
• B. defining at least one image data slice, each data slice corresponding to a position along said longitudinal axis of said region, each of said image data slices defining a plurality of scan data projections obtained from a respective plurality of view angles during the scanning step, each scan data projection containing scan data at its respective view angle;
• C. generating a CT image from said scan data at said first energy level, and using the CT image to select at least one clear-path scan data projection from said image data slice, corresponding to one of said view angles, wherein said clear-path projection includes at least said object, and selecting a first set of scan data at said first energy level and a second set of scan data at said second energy level, each set of data corresponding to said clear-path projection;
• D. generating, from said first set of scan data and said second set of scan data, corresponding to said clear-path scan data projection, a first value representative of said first physical characteristic and a second value representative of said second physical characteristic, and recognizing and identifying said object as a function of said first value and said second value.