Methods for spectral CT imaging

From the earliest days of X-ray computed tomography (CT), it was realized that measurements made with different X-ray spectra could be used to differentiate materials having different atomic numbers. Successful implementation of this technique, often referred to as dual-energy CT, has occurred over the last decade (circa 2009–2019), bringing with it new clinical capabilities. Dual-energy data can be acquired using a number of different techniques, some of which use only a single tube potential and some of which use two tube potential settings. Additionally, while some techniques can be performed without changes in acquisition hardware, others require the use of novel detectors, X-ray beam filters, or even a second source-detector system. Further, after acquisition, a number of different types of images can be formed, including the low- and high-energy spectral images, mixed images that combine these two data sets, material-specific images, and energy-specific images.