Hiya
I've had a brain scan but you need to check whether it is CT or MRI coz the scanner is different.
CT scan is very much like a polo mint and you dont really 'enter' the scanner whereas MRI is a confined thin tube which you slide right into. I'm not claustrophobic but you do think your nose might scrape along the top of the scanner!
They will give you earplugs coz the MRI scanner makes a very loud clicking noise - hard to explain, a bit like a pneumatic drill? And they put an alarm in your hand and if you get worried, they will come and pull you out. There is also a mirror on the ceiling so you can see everyone in the room.
My mum needed one and was very nervous and they allowed me to sit next to her and hold her hand!
Takes about 20 minutes - good luck! x