A method and apparatus for identifying a material in an object. An image of the object generated from energy passing through the object is obtained by a computer system. The computer system estimates attenuations for pixels in a sensor system from the image of the object to form estimated attenuations. The estimated attenuations represent a loss of the energy that occurs from the energy passing through the object. The computer system also identifies the material in the object using the estimated attenuations and known attenuation information for identifying the material in the object.
GOVERNMENT LICENSE RIGHTS
 This invention was made with United States Government support under Contract No. DE-AC04-94AL85000 between Sandia Corporation and the United States Department of Energy. The United States Government has certain rights in this invention.