Depth-based surveillance image reconstruction

An imaging system comprising:

• an interrogating apparatus configured to transmit toward and receive from a subject in a subject position, electromagnetic radiation having one or more frequencies between about 100 MHz and about 2 THz, the interrogating apparatus producing an image signal representative of the received radiation;
• and
• a controller adapted to produce, from the received electromagnetic radiation, at least first image data representative of at least the portion of the subject based at least in part on reflectivity of the electromagnetic radiation for a plurality of depths for each of a plurality of picture elements, to select a first depth for each of the plurality of picture elements based at least in part on the reflectivity of the electromagnetic radiation at at least the first depth, to select a second depth for each of the plurality of picture elements based at least in part on the first depth of at least another one of the picture elements, and to produce at least second image data representative of at least a first image of at least the portion of the subject based at least in part on reflectivity of the electromagnetic radiation at the second depth.