A method for analyzing dual-energy computed tomograms is presented. The method requires three calibration values at each energy: air, water, and a KI solution. The first two values are used to convert the CT numbers to the ideal Hounsfield scale. The KI value is used to calculate quality factor Q that describes the effective x-ray spectrum. By using the Q-values, the Compton and photoelectric coefficients of any tissue or material may be easily obtained. One can further calculate the electron density and effective atomic number, if desired, and perform chemical identification.