- Lumbar intrathecal injection of In111 DTPA
- Basal cisterns at 1 hour
- Frontal poles and sylvian fissues by 6 hours
- Cerebral convexity bu 12 hours
- Saggital sinus by 24 hours
- Does not normally enter verntricular system and is suggestive of normal pressure hydrocephalus if persistant at 24hrs. Study helps differentiate from brain atrophy.