Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is a neuroimaging technique that uses strong magnetic fields, magnetic field gradients, and radio waves to generate anatomical images. MRI is particularly useful at looking for white matter and subcortical changes.

Advantages
  • MRI has a clear advantage of no ionizing radiation. It also has an advantage over CT in that it can detect blood flow, occult/cryptic vascular malformations, and demyelinating diseases like multiple sclerosis. There are also no beam-hardening artifacts as seen in CT, and the posterior fossa is more easily visualized on MRI than CT.
Disadvantages

The Fazekas scale is used to quantify white matter T2 hyperintense lesions due to chronic small vessel ischemia (though not all such lesions are due to this).[1] In routine clinical practice, the Fazekas scale is generally not used. General clinical descriptor such as “mild”, “moderate” and “severe” are typically used.

Fazekas scale for white matter lesions

Fazekas, Franz, et al. MR signal abnormalities at 1.5 T in Alzheimer's dementia and normal aging. American journal of roentgenology 149.2 (1987): 351-356.
Score → 0 1 2 3
Periventricular white matter (PVWM) Absent “Caps” or pencil-thin lining Smooth “halo” Irregular periventricular signal extending into the deep white matter
Deep white matter (DWM) Absent Punctate foci Beginning confluence Large confluent areas
  • Note that FLAIR will miss strokes in the basal ganglia.
  • Pacemakers and implanted defibrillators are generally not compatible with MRI, though newer devices are now compatible with MRI.
  • Sometimes, perivascular spaces can look like ”mini strokes”, but they are not.
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