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These small regions of high intensity are observed on T2 weighted MRI images (typically created using 3D FLAIR) within cerebral white matter (white matter lesions, white matter hyperintensities or WMH) [1] [2] or subcortical gray matter (gray matter hyperintensities or GMH). The volume and frequency is strongly associated with increasing age. [2]
T 2 *-weighted GRE sequences can detect microhemorrhages as seen in most vestibular schwannomas, thereby differentiating them from meningiomas. [2] The T 2 *-weighted GRE sequence can detect a "middle cerebral artery susceptibility sign", which is a dark linear filling defect that is wider than the corresponding artery on the contralateral side ...
Middle: ARIA-H with multiple microbleeds (T2* weighted) Right: ARIA-H with superficial siderosis (T2* weighted) Two non-exclusive mechanisms have been postulated. Firstly, in the context of aging and neurodegeneration, the integrity of the blood-brain barrier (BBB) can become compromised, resulting in increased permeability.
Fluid-attenuated inversion recovery (FLAIR) [2] is an inversion-recovery pulse sequence used to nullify the signal from fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid so as to bring out periventricular hyperintense lesions, such as multiple sclerosis plaques.
One strictly lobar haemorrhagic lesion on T2*-weighted MRI: intracerebral haemorrhage, cerebral microbleeds, or foci of cortical superficial siderosis or convexity subarachnoid haemorrhage; OR One white matter feature (severe visible perivascular spaces in the centrum semiovale or white matter hyperintensities in a multispot pattern)†
In the case of CSF suppression, one aims for T 1-weighted images, which prioritize the signal of fat over that of water. Therefore, if the long TI (inversion time) is adjusted to a zero crossing point for water (none of its signal is visible), the signal of the CSF is theoretically being "erased," from the derived image.
Central pontine myelinolysis; Other names: Osmotic demyelination syndrome, central pontine demyelination: Axial fat-saturated T2-weighted image showing hyperintensity in the pons with sparing of the peripheral fibers, the patient was an alcoholic admitted with a serum Na of 101 treated with hypertonic saline, he was left with quadriparesis, dysarthria, and altered mental status
T2-weighted images also displaying cerebrospinal fluid and rarefied/cystic white matter. To view the remaining tissue, and get perspective on the damage done (also helpful in determining the rate of deterioration) (T1-weighted), proton density, and FLAIR images are ideal as they show radiating stripe patterns in the degenerating white matter.