Ioannis Vlahos, MD

X-ray matter interactions in the diagnostic imaging energy range are dominated by photoelectric and Compton effects. Both interactions increase in proportion to electron density, which is proportional to physical density. In conventional CT imaging at 120 kVp to 140 kVp, the Compton effect predominates, and hence image quality is primarily governed by physical density.

Conventional single-energy CT imaging results in an anatomic depiction of the imaged area based on depiction of differences in physical density. Dual-energy CT imaging differentiates structures of a similar density with different elemental compositions based on differing attenuations at different photon energies. Hence, dual-energy imaging moves away from imaging density toward imaging elemental, or possibly even chemical, composition (see accompanying article).