The measurement of effective photon energy and "linearity" in computerized tomography.

Two liquid systems have been developed for the measurement of effective photon energy (Eeff) and "linearity" in computerized tomography (CT). A group of sixteen "keV liquids" enables an Eeff to be rapidly determined, by comparing the CT numbers of the specially formulated organic liquid mixtures with similar data for water. The "linearity" of the CT scanner, relating CT nubers to linear attenuation coefficients, may be investigated using 14 selected organic "linearity liquids". Details of these systems, together with some typical results, are presented.