Strokes are the third leading cause of death in the United States, according to the American Stroke Association. Strokes occur when blood stops flowing to one part of the brain, according to Medline Plus. They are life-threatening conditions that require immediate medical care. Diagnosing a stroke can be difficult. Doctors use magnetic resonance imaging, or MRI, to scan the brain and help evaluate the damage caused to its internal structures by a stroke.
Definition
Another medical term for stroke is cerebral vascular accident, or CVA. At its simplest, a CVA is bleeding in the brain. Two types of stroke can occur: ischemic or hemorrhagic. An ischemic stroke occurs when a blood clot obstructs blood flow to the brain. A hemorrhagic stroke describes a CVA caused by the rupture of a blood vessel, disrupting blood flow in the brain. An MRI is effective for imaging both of these types of strokes, whereas other brain scans, such as computed tomography scans or CTs, may miss certain ischemic strokes.
Diagnosis
Doctors order an MRI when they suspect that a patient is having or has had a stroke. Symptoms of a CVA may include confusion, inability to speak, weakness or drooping on one side of the face or body.
Function
An MRI uses a magnetic field and radio waves to create an image of the brain. An MRI machine is basically a long magnetic tube in which a patient lies. When a technician applies the magnetic field, it temporarily causes all of the hydrogen atoms in a patient's body to line up. The technician then bounces radio waves against these atoms to emit faint signals. Different types of tissue send back different types of signals.
In stroke patients, the MRI machine uses these signals to create three-dimensional images of the brain that may be sliced to allow a physician to see inside an organ. The images may also be rotated to allow visualization of an organ from all angles, according to the Mayo Clinic. One MRI can produce thousands of images, and a single image is called a slice.
Use
A stroke is a medical emergency in which every minute counts, because the damage caused by stroke is largely dependent on how long the bleeding continues in the brain. Physicians may therefore decide to use other tests, such as a CT scan, in addition to MRI to make an initial diagnosis. CT scans are usually completed more rapidly, giving the physician quick results to help her treat a patient, but CT scans may not be as accurate as MRI, states the Merck Manual for Healthcare Professionals.
Benefits
Researchers have found no evidence of adverse effects of MRI scans in the human body, according to Emergency Medicine News. An MRI helps physicians identify the presence, location, size and level of brain damage that results from a stroke.
