Cardiac MRI > Technique > Contrast Agents
Contrast Agents
MRI is sometimes performed with the use of intravenous contrast agents to enhance the signal of pathology or to better visualize the blood pool or vessels. Most MRI contrast agents are gadolinium chelates. The paramagnetic effect of gadolinium causes a shortening of T1 relaxation time, thus causing areas with gadolinium to be bright on T1-weighted images. Contrast agent is used in Cardiac MRI for evaluation of myocardial perfusion, delayed enhanced imaging (myocardial infarctions, myocarditis, infiltrative processes), differentiation of intracardiac masses (neoplasm vs. thrombus) and to opacity blood vessels in MR angiography (MRA).
A single dose of Gadolinium is 0.1 mmol/kg, which is 0.2 cc/kg for most common Gadolinium preparations (0.5 mmol/cc). A double dose is twice that: 0.2 mmol/kg or 0.4 cc/kg. Below is a table for typical doses used in cardiac MR:
Application |
Gadolinium Dose (cc/kg) |
Perfusion |
0.15 |
Delayed Enhancement |
0.3 |
MR angiography |
0.4 |
The above cine demonstrates gadolinium first pass imaging. Gadolinium contrast agent is injected into an upper extremity vein and quickly progresses sequentially through the right heart, the pulmonary arteries, pulmonary veins, left heart and aorta. After contrasted blood enters the aorta, the myocardium begins to enhance due to perfusion from the coronary arteries. This patient has a myxoma which is an intracardiac tumor represented by the dark area within the left atrium which slowly enhances after the myocardium.
