What is the utility of precontrast imaging when performing CTA or MRA of the aorta?
Subacute hemorrhage has higher attenuation than flowing blood on noncontrast CT and high signal intensity on precontrast T1-weighted MRI. These findings can be easily obscured in the presence of an intravenous contrast material. Precontrast imaging is mandatory to detect the presence of intramural hematoma. Noncontrast CT images are also useful to detect the presence, location, and amount of atherosclerotic calcification. Calcification is generally difficult to visualize on MR images.
