Contrast material, or contrast dye, is a substance used to make
specific organs, blood vessels, or types of tissue (such as tumors) more
visible on X-rays. Contrast material may also be used during a CT scan, an
ultrasound, or an MRI scan.
Common contrast material substances include iodine, barium, and
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Howard Schaff, MD - Diagnostic Radiology