1. A system for creating an image of an object, said object containing a first chemical element having a K EDGE, FIRST CHEMICAL ELEMENT, said system comprising: an X-ray source configured to emit an X-ray beam along a first path through said object; means for moving said beam onto successive paths through said object; a first filter and a second filter, said first filter comprising a chemical element having a K EDGE greater than K EDGE, FIRST CHEMICAL ELEMENT and said second filter comprising a chemical element having a K EDGE less than K EDGE, FIRST CHEMICAL ELEMENT ; a means for successively positioning said filters on each said path to filter said beam and produce a first filtered radiation signal and a second filtered radiation signal for each said path through said object; a detector for receiving said first and second radiation signals after said signals have passed through said object and producing a first and second electrical signal for each said path, said electrical signals produced by said detector being proportional to the intensity of the radiation received by said detector; and a processor connected to said detector to generate an image signal for each said path through said object wherein said image signal is proportional to a difference between said first and second electrical signals, said processor configured to produce an image of said object from said image signals.