T1 weighted imaging with contrast
Everything that is bright on non-enhanced T1WI will also be bright on contrast-enhanced T1WI (CE-T1WI). The brain has a robust blood-brain-barrier (BBB) that prevents gadolinium from crossing into the parenchyma. This means that the parenchyma does not normally enhance. Injecting gadolinium contrast allows us to look for processes that cause pathological enhancement.
Why do things enhance?
If there is parenchymal enhancement it means that there is a break in the BBB from:
- direct destruction e.g. vasculitis
- leaky vessels in inflammation or subacute infarct
- immature angiogenesis as seen in tumours
How can I tell if a sequence is contrast-enhanced?
If there is no pathologically enhancing lesions there are several structures that normally enhance that you can look at to determine whether a scan has contrast or not:
- pituitary gland and infundibulum (outside of the BBB)
- arteries
- choroid plexus
- mucous membranes
- venous structures
- basivertebral veins of spine
