Hardened plaque located in the carotid arteries can cause stroke or transient ischemic attack (TIA). This type of plaque is linked to unstable free-floating thrombi (FFT). FFT are blood clots that form in a blood vessel, and are at the highest risk for travelling within the bloodstream and causing strokes. Physicians are able to see this type of plaque with computed tomographic angiography (CTA) but FFT look very similar to stable types of plaque that do not require urgent treatment.