It goes without saying that stroke is a serious problem. It is responsible for the deaths of about 133,000 people in the United States annually, ranking as the fifth leading cause of death in this country . In addition, in those who survive it, stroke often causes long-term disability, thus putting serious financial burden on them and the health care system.
There are two kinds of strokes: ischemic and hemorrhagic. Hemorrhagic stroke is characterized by the rupture of an artery in the brain, thus making it fairly easy to visualize via CT (Computed Tomography) scans . On the other hand, about 80% of strokes can be classified as ischemic, or caused by a blood clot in an artery in the brain . When well visualized, they typically manifest on non-contrast CT scans as dark spots, meaning that the corresponding tissue in the brain is hypodense due to cell death . However, visualization of these spots is often difficult due to the relatively low resolution of non-contrast CT.
As mentioned earlier, in order to accurately diagnose stroke and determine appropriate treatment, doctors must rely on various imaging technologies, particularly CT and MRI (Magnetic Resonance Imaging) scans. MRI scans have better resolution and contrast between soft tissues, and thus makes visualization of ischemic strokes in the brain easier, as shown below:
 Benjamin, EJ, et al. “Heart Disease and Stroke Statistics – 2017 Update.” Circulation 135.10 (2017): American Heart Association, 25 Jan. 2017. Web. <https://www.heart.org/idc/groups/ahamah-public/@wcm/@sop/@smd/documents/downloadable/ucm_491265.pdf>.
 Velayudhan, Vinodkumar. “Stroke Imaging.” Medscape. 22 Sept. 2016. Web.<http://emedicine.medscape.com/article/338385-overview>.