Dual-energy CT systems: technical aspects and selected clinical applications

Dual-energy CT (DECT) has been available for clinical use since 2006. Since its clinical debut, multiple different dual-energy systems have been developed including sequential acquisition, rapid-switching, dual-source, and twin-beam, in addition to spectral imaging techniques such as dual-layer and photon counting CT. While the specifics of these techniques vary, the underlying principles remain the same; by acquiring at least 2 datasets, material-specific information in each image voxel can be determined. Most commonly used to evaluate for the presence or absence of iodine, DECT has found clinical applications in the assessment of gastrointestinal bleeding, bone marrow oedema, the characterization of renal stones, and the accurate evaluation of vascular stenosis, among other uses. This review aims to familiarize the radiologist with the theoretical basis underlying DECT, describe the different types of DECT including the relative strengths and weaknesses of each, and highlight specific clinical applications for which DECT may be valuable.