Introduction and Technical Principles

Dual- and multi-energy CT are the latest advances in CT technology and material differentiation. Dual energy is already feasible in routine clinical practice; it is based on different absorption of X-rays at different kV, leading to better material characterization, in particular iodine. Ione maps and virtual non-contrast images can be digitally generated. Multi-energy CT (or spectral CT) is not clinically applied yet. It is based on new detector designs that have energy-sensitive photon-counting abilities. Soft-tissue characterization and selective contrast material detection are achieved by recognizing tissue- and material-specific energy distributions. In this chapter, technological and physical basis of dual- and multi-energy CT will be explained.