Expanding CT Application to Myocardial Tissue Characterization.

C omputed tomography (CT) has evolved into a powerful diagnostic tool, and since the advent of 64-detector row scanners, it has been demonstrated as a promising noninvasive method for coronary artery stenosis imaging (1). Although the basic physical principle of CT is unidimensional, a function of x-ray attenuation detected from multiple orientations around the imaged object, exciting new technical developments have opened the avenue for novel research applications such as myocardial infarct imaging with late post-contrast CT (2), assessment of cardiac function and volume changes (3), and even hemodynamic assessment of coronary stenosis significance with CT-derived fractional flow reserve using computational fluid dynamic principles (4). One such technical advance is dual-energy CT, which uses the photoelectric effect of CT to exploit the energy-dependent attenuation of tissues when exposed to 2 different photon energy levels. This technique allows the characterization of tissues on the basis of attenuation profiles of 3 known materials, such as iodine (in CT contrast), soft tissue, and fat at 2 levels of energy (e.g., 100 kV and 140 kV) (5). One recently introduced cardiac application uses the ability of dual-energy CT to map regional myocardial iodine distribution as a quantitative marker of blood volume, which is a surrogate for myocardial perfusion and can be used to detect ischemia (6).