MRI of the Head/Brain
MRI has essentially replaced CT for evaluation of all non-acute, non-traumatic brain imaging. This is because of MRI's superior soft tissue contrast. CT is still used as initial imaging in the work up of acute stroke and trauma, particularly to evaluate for the presence of blood. In the evaluation of a stroke, MRI frequently follows because of its ability to detect hyper-acute stroke, not possible with CT.
MRI has long been the modality of choice for almost all non-traumatic brain imaging. This includes imaging of congenital abnormalities, cancer (including evaluation for metastatic disease), white matter disease, vascular malformations, and infectious disease (cerebritis and encephalitis as well as meningitis, though mainly for complications of meningitis). Regarding contrast use, the same rules apply to CT and MRI. Contrast is most useful when evaluating for a possible mass or vascular malformation and in evaluating for an inflammatory condition (meningitis, encephalitis, cerebritis).