Use of Dual-Energy CT and Iodine Maps in Evaluation of Bowel Disease

Dual-energy computed tomography (CT) relies on material-dependent x-ray absorption behavior from concurrently acquired high- and low-kilovolt peak data and has a range of imaging applications. This article focuses on use of dual-energy CT in assessment of bowel disease. After a summary of relevant dual-energy CT image acquisition and postprocessing principles, the authors describe dual-energy techniques of greatest utility in evaluation of benign and malignant pathologic conditions in the bowel, including neoplastic, vascular, infectious, and inflammatory disorders, as well as in assessment of abdominopelvic trauma. The dual-energy postprocessing techniques of iodine-selective imaging and virtual monochromatic imaging have the broadest applicability in bowel imaging. They may be used for improved visualization of subtle differences in bowel wall enhancement or for quantitative assessment of altered enhancement for evaluation of a neoplasm or bowel ischemia. Iodine images and virtual monochromatic low-kiloelectron volt images are particularly helpful for assessment of a neoplasm, ischemia, infection, or inflammation, while iodine maps paired with virtual nonenhanced images are most helpful to differentiate iodine from other dense materials, as in gastrointestinal bleeding or trauma. In most applications, radiation doses at dual-energy CT are comparable to those at traditional CT. However, dual-energy CT may allow reduction in radiation dose by using virtual nonenhanced images that obviate an additional nonenhanced CT acquisition. Limitations of dual-energy CT are discussed, including potential challenges in acquisition, postprocessing, and interpretation.