Measurement of effective atomic number and electron density using an EMI scanner.

Computed tomography, employing an EMI scanner at two beam energies, can be used to obtain information about the electron density and the effective atomic number of materials. The theory which is discussed has been verified experimentally and then applied in the investigation of some brain tumours in vivo. It is anticipated that, as techniques improve, the ability to carry out chemical and physical analysis of pathological processes in vivo will be an important application of computed tomography.