Critical Care Registered Nurse (CCRN) Practice Exam

What substance is used as a contrast medium in MRA to highlight arteries?

1. Iodine

2. Gadolinium

3. Saline

4. Acetylcholine

The correct answer is: Gadolinium

Gadolinium is the substance commonly used as a contrast medium in Magnetic Resonance Angiography (MRA) to enhance the visibility of blood vessels, particularly arteries. This paramagnetic metal ion has unique properties that improve the quality and detail of the images obtained from MRI scans. When gadolinium is injected into the bloodstream, it alters the magnetic properties of nearby water molecules, allowing for a clearer distinction between blood vessels and surrounding tissues. This helps in diagnosing various conditions related to vascular health, such as blockages, aneurysms, or other abnormalities. Other substances listed, like iodine, are typically used in CT scans as a contrast agent, and saline is utilized mainly for intravenous fluid administration or as a diluent. Acetylcholine, primarily a neurotransmitter, does not serve as a contrast agent. Therefore, the efficacy of gadolinium in providing high-resolution images of arteries makes it the correct choice for use in MRA.