CT and MRI brain imaging, including CT angiography and CT perfusion
Choose the modality by the question
| CT | MRI | |
|---|---|---|
| Speed | Seconds | 20-45 min |
| Acute haemorrhage | Excellent | Good (SWI/GRE) |
| Acute ischaemia <6 h | Poor | Excellent (DWI) |
| Posterior fossa | Poor - beam-hardening artefact | Excellent |
| Bone, fracture, calcification | Excellent | Poor |
| White matter, demyelination | Poor | Excellent |
| Availability, unstable patient | Any hour, monitored | Limited, contraindications |
| Radiation | ~2 mSv | None |
- The commonest imaging error in neurology is a CT used to exclude something only MRI can see - posterior fossa stroke, early ischaemia, cord lesions, small tumours, encephalitis
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