Dual Energy Computed Tomography: How Does It Work and What Can It Do?

In CT imaging, materials having different chemical compositions can be represented by the same, or very similar, CT numbers, making the differentiation and classification of different types of tissues extremely challenging. A classical example is the difficulty in differentiating between calcified plaques and iodine-containing blood. Although these materials differ in atomic number considerably, depending on the respective mass density or iodine concentration, the bone and iodinated blood may appear identical. In addition to the difficulty in differentiating and classifying tissue types, the accuracy with which material concentration can be measured is degraded by the presence of multiple tissue types. For example, when measuring the amount of iodine enhancement of a soft tissue lesion, the measured mean CT number over the lesion reflects not only the enhancement due to iodine, but also the CT number of the underlying tissue.