Dual energy computerized tomography: a simplified approach

Attenuation numbers of various organic liquids were measured in a phantom at the low and high X-ray beam settings of the Mark I and CT 1010. The readings were translated into absolute units and ratios computed. There is a nonlinear relationship between this ratio and the effective atomic number of the compounds tested. A ratio of one defines a substance with energy dependence like water. Ratios below one definite anhydrous substances composed of elements with low atomic numbers. Ratios greater than one defined substances containing elements with high atomic numbers.