Ten Things That I Learned Today

	Bright	Dark
T1	- contrast - fat/cholesterol (lipoma, teratoma, dermoid, lipomatous ependymoma, cholesteatoma) to differentiate fat from other T1-bright lesions, look for chemical shift artifact (dark band at edge of fat on one side, light band at the other) - melanin - early subacute blood (intracellular metHb 3-7 days) and late subacute blood (extraceullar metHb, 1-4 weeks) - subacute thrombus (i.e. venous sinus) - protein-rich fluid (colloid, rathke’s cleft, ectopic posterior pituitary, craniopharyngioma – also cholesterol and blood) - minerals (microcalcifcations, iron, manganese – hepatic encephalopathy, copper) - laminar necrosis (from global hypoxemia or immunosuppression – appears 2 weeks after insult) – may appear as cortical ribbon - slowly flowing fluid**	- CSF - Edema - flow voids - calcium (bone) – although microcalcifications often appear as bright on T2 due to their interaction of water molecules
T2	- Edema (from tumor, infection, inflammation, ischemia, vasculitis, radiation-induced, chemo-induced, migraines, etc) - late subacute blood (extracellular metHb) - CSF (virchow robin spaces) - Demyelination - Myelinolysis - Degeneration	- contrast - acute blood (deoxy Hb)/early subactue blood (intracellular metHb), chronic blood (hemosiderin) - melanin - mucous/protein (i.e. colloid/rathke cyst - hypercellular tumors (high nucleus to cytoplasm ratio – medullo, lymphoma, highest grade parts of high grade gliomas) - tends to be dark but not black - minerality (iron, copper, calcium) - flow voids/turbulent flow – of blood and CSF (jets can appear dark) - air - fibrous tissue/bone**
Diffusion	- T2 shine through - acute ischemia (<2-3 weeks) - highly cellular tumors (lymphoma, medullo/PNET, meningioma, chordoma, germinoma, hemangiopericytoma, pinealblastoma, cortical part of high-grade gliomas – cyst part typically does not restrict in gliomas) - abscess (cystic part restricts 2/2 pus) - mucinous metastasis like breast or colon adenocarcinoma (mucus restricts) - epidermoid - prion disease (CJD, kuru – cortical ribboning) - toxic (carbon monoxide, methanol, Wernicke, maple syrup urine, gluteric aciduria, methyl malonic aciduria other inborn errors of metabolism diseases) - adrenoleukodystrophy	- old stroke (> 3 weeks) - necrosis (i.e. core of GBM/mets)
GRE/SWI		Blooming - air - blood of any age - mineralization - inflammation