Marilyn J. Siegel MD, Presenter: Research Consultant, Siemens AG Speakers Bureau, Siemens AG

1) Discuss the general principles of dual-energy CT. 2) Describe radiation dose aspects of dual energy CT. 3) Unstand clinical applications of dual-energy CT in clincial patient care.

Dual energy CT; (DECT) refers to the acquisition of CT datasets at two different energy spectra (80/140,100/140, or 70/150).; The acquisition of CT data at different photon energies enables differences in material composition to be detected based on differences in photon absorption at the two kVp settings. There are two basic approaches to DECT: rapid voltage switching and dual source CT, the latter;allowing simultaneous acquisition of data from two X-ray tubes operating at different tube potentials in a single CT acquisition. This presentation will focus on the dual source DECT approach. The images acquired can be viewed as low and/or high, kVp images and as a mixed or blended dataset which integrates two kVp acquistions in a single imagefor immediate clinical evaluation.; Image blending can be linear or nonlinear. Linear blending is a continuous function with equal weighting of the noise characteristics of the high-energy scan and the contrast characteristics of the low-energy scan. Nonlinear blending is based on modified sigmoid blending and operates in a voxel-by-voxel fashion. In addition, virtual unenhanced CT images, iodine maps, color-coded images superimposing iodine distribution on the virtual nonenhanced data, bone-subtraction images for CT angiographic studies, and renal stone content analytic images can be generated using dual-energy post-processing software. Monoenergetic images, in which the density for each voxel is extrapolated to a certain energy (range 50-190 keV) from the two density values at the acquired photon energies, can be performed. Clinical applications are;CT angiography, assessment of lung perfusion and ventilation,;characterization of renal stones, liver, pancreatic,;adrenal, and renal masses, assessment of myocardial perfusion. The monoenergetic application allows removal of metal artifacts at higher keVs. The radiation dose from DECT is comparable to that with single energy CT.

Siegel, M, ASRT@RSNA 2014: Dual Energy Computed Tomography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14000940.html