My Dr is sending me for a brain MRI and is asking for the great vessels and circle of Willis to be included, has anyone been through this?

What happens during a brain MRI? I've had other kinds, cervical etc.

Having awful cognitive problems and possible seizures, just want to know why I'm having these "spells", loss of time, I go in to a dream like state for a few minutes, go in to very familiar places but don't recognize them for a minute or two and my arms and fingers feel like electricity and shake.

Hope everyone is doing well today.