Infarction: focal hypodense area, in cortical, subcortical, or deep gray or white matter, following vascular territory, or watershed distribution. Early subtle findings include obscuration of gray/white matter contrast and effacement of sulci, or "insular ribbon."

Hemorrhage: hyperdense image in white or deep gray matter, with or without involvement of cortical surface (40 to 90 HU). Petechial refers to scattered hyperdense points, coalescing to form irregularly hyperdense areas with hypodense interruptions. Hematoma refers to a solid, homogeneously hyperdense image.

    Hyperdense image in major intracranial artery: suggestive of vascular embolic material.

    Calcification: hyperdense image within or attached to vessel wall (>120 HU).

    Incidental: silent infarct, subdural collection, tumor, giant aneurysm, arteriovenous malformation.

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In just a few decades, the use of magnetic resonance imaging (MRI) scanners has grown tremendously. Doctors may order MRI scans to help diagnose multiple sclerosis, brain tumors, torn ligaments, tendonitis, cancer and strokes, to name just a few.

Magnetic resonance imaging (MRI) is a noninvasive way to take pictures of the body.An MRI scan is the best way to see inside the human body without cutting it open.

Unlike x-rays and computed tomographic (CT) scans, which use radiation, MRI uses powerful magnets and radio waves. The MRI scanner contains the magnet. The magnetic field produced by an MRI is about 10 thousand times greater than the earth's.

The magnetic field forces hydrogen atoms in the body to line up in a certain way (similar to how the needle on a compass moves when you hold it near a magnet). When radio waves are sent toward the lined-up hydrogen atoms, they bounce back, and a computer records the signal. Different types of tissues send back different signals.

Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images.

You may not be able to have an MRI if you have any of the following metallic objects in your body:
    Brain aneurysm clips
    Certain artificial heart valves
    Inner ear (cochlear) implants
    Recently placed artificial joints
    Some older types of vascular stents