1. STIR sequence: 

- T1, but looks like T2

- Suppresses signal from fat, but highlights fluid

- Allows you to differentiate true edema from fat (i.e. suppresses marrow fat signal in spine vertebral body, allows detection of edema in bone that may reflect osteomyelitis). 

- Also allows easy detection of ligamentous injury in the spine

- In the brain, STIR highlights the contrast between grey and white, and can show hippocampal edema which may indicate epilepsy

2. Most common structural causes of epilepsy, from {radiologyassistant.nl} - 

3. FLAIR sequence

- T1, but looks like T2

- Suppresses CSF, detects edema. 

- Useful in the evaluation of tumors and MS plaques 

4. 100% supplemental O2 causes artifactual hyperintensity on FLAIR imaging! 

Normal volunteer breathing room air: 

 Same volunteer breathing 100% O2:

{image source}

Note increased hyperintense signal in quadrigeminal/ambient cisterns, suprasellar cistern, cerebral sulci, sylvian fissures, etc. 

- The paper in AJNR (linked above under image source) found that the artifact went away at 50% oxygenation, and was unaffected by the type of anesthesia. 

5. Schizencephaly: 

- Cleft between ventricle and cortical surface, often lined with polymicrogyria. 

6. Interpreting blood on MRI- helpful hints: 

- Intracellular stuff= dark on T2, extracellular stuff= bright on T2

- Methemoglobin = bright on T1 

Age	Contents	T1	T2
Hyperacute	Intracellular oxyHb	Isointense	Isointense to bright
Acute  (hrs-days)	Intracellular deoxyHb	Isointense	Dark
Early subactue (days-weeks)	Intracellular metHb	Bright	Dark
Late subacute	Extracellular metHb	Bright	Bright
Remote/Chronic	Ferritin Hemosiderin	Dark	Dark

7. Tumor hemorrhage: 

- 14% of mets and <5% of primary tumors are hemorrhagic 

- Often heterogenous and complex in appearance 

- Mets that bleed: chorio, thyroid, renal cell, melanoma, breast, lung

- Often have hypointense T2 rim 

8. Venous bleeds: 

- can look like tumor bleeds (heterogenous) 

- temporal/thalamic 

- can be at grey-white border

9. Arterial bleeds: 

- Follow single vessel arterial distribution

- Often on the convexity  

10. Other bleeds: 

- Amyloid: peripheral, parietoccipital, does not affect basal ganglia, generally age>75 (younger than 75- think of another etiology) 

- Contusion: bone-dural interface

- DAI: punctate, dorsal upper brainstem, corpus callosum