Which procedure involves injecting radiopaque material to visualize blood vessels?

The procedure that involves injecting radiopaque material to visualize blood vessels is angiography. This imaging technique uses a contrast dye that is opaque to X-rays, allowing healthcare professionals to see the outline of blood vessels clearly on the images produced. Angiography is particularly useful for diagnosing conditions related to blood vessels, such as blockages, aneurysms, or malformations.

In angiography, the injected contrast agent highlights the vascular structures, which can then be evaluated using fluoroscopy or X-ray imaging. This method is crucial in understanding vascular anatomy and pathology, enabling procedures like stenting or angioplasty when necessary.

While the other options like ultrasound, CT scans, and MRIs are valuable imaging techniques, they function differently. Ultrasound uses sound waves to create images and does not typically rely on radiopaque materials. CT scans can utilize contrast material, but can also be used without it, and they primarily provide cross-sectional images of structures inside the body rather than focusing solely on blood vessels. MRIs use magnetic fields and radio waves to generate images, and they do not utilize radiopaque materials for visualization.