Element specific imaging in computer assisted tomography using a tube source of x-rays and a low resolution detector

摘要

A new technique for element specific imaging inudcomputerised tomography has been developed. The techniqueudallows two or more elements to be imaged independently ofudthe matrix in which they are contained. The technique usesuda filtered tube source of x-rays and low energy resolutionuddetector.ududFractional transmittance measurements were recorded atuda number of tube potentials along each of the beam pathsudrequired for standard CT reconstruction. This data wasudused to obtain monochromatic information about theudabsorber. K-edge differential absorptiometry was then usedudto obtain the equivalent thickness of each element ofudinterest. Using the algebraic reconstruction techniqueud(ART), element specific images were generated. Theudtechnique was successfully used to separately image iodineudand barium distributed in a water matrix.ududIn a refinement of the technique, a single channeludanalyser was used to increase the percentage of counts inudthe fractional transmittance measurement providingudinformation about the elements of interest. Using thisudapproach, cadmium and indium, elements with a K-edgeudseparation of 1.23keV, were separately imaged. Theudtechnique was also tested for matrix independence andudlinearity using homogeneous samples.ududUsing computer simulations the optimum operatingudconditions and characteristics of the technique wereudexamined.ududFinally, future developments of the technique areuddiscussed along with a possible application.