Invited Lecture 3.5

Abstract

Dual-energy CT (DECT) is an innovative technology that utilizes the changes in differential absorption of X-rays within different tissues at two different X-ray energies. Attenuation measurements at different X-ray energies, together with the use of the known changes in attenuation between the two energies, enable the differentiation and classification of materials that the X-ray beam is traversing. The differences are more pronounced for materials with a higher atomic number, because the photoelectric effect becomes dominant at lower energies and higher atomic number materials, resulting in a larger change in differential absorption. Different vendors have embraced different technologies to achieve sufficient energy separation between the high and low energy spectra. These include: two consecutive scans at different energy levels as the most straightforward approach; two X-ray sources running at different voltages, with two corresponding sets of detectors, offset within the gantry at a known angle; beam filtration with two different filters to split a single X-ray beam into two beams of different energies; rapid tube potential switching between the high and low energy setting on a view-by-view basis during one scan; or using advanced dual-layer detector technology to achieve the energy separation, where each layer preferentially absorbs either higher or lower energies, and images are reconstructed from each layer of the detectors. DECT is being increasingly implemented in daily clinical practice and offers greater diagnostic performance compared to single energy CT.