PA Anatomy: Imaging Overview- MR

Since MR imaging is based on differences in magnetic properties of tissues, rather than density, Iodine and Barium are not useful as contrast agents in MR. Most MR contrast agents contain the element Gadolinium bound to complex chemicals. Gadolinium acts to alter T1, so is only used in T1-weighted imaging. It is usually injected into a vein and used to show blood vessels or organs with high blood flow, like the liver, kidneys, brain and spleen.

These images are both in the axial plane. The ventricles (fluid filled spaces in the brain, indicated by V) are dark or low signal on both, so they are both T1-weighted images. If you look in the circled areas in Image B, there are many high signal (white) areas that are not seen on Image A. These are blood vessels, and are visible because IV contrast was given. Gadolinium makes vessels and very vascular organs or tumors show up as high signal (white) areas on T1-weighted images.