I have undergone an MRI twice about eighteen years apart. The first was of the brain and the heart system. It was a two part procedure for scanning. The first of the brain and heart system. Then I was removed a dye was used through an intravenous (IV) line and they did another imaging of the heart system. The second was the brain only.
I once wrote a hub about the last one since deleted. I may go back and uncover it and publish again. It was definitely interesting. Both events leading up to those MRI's were different circumstances. The first I discovered myself on the floor with a puddle of blood because I apparently had conked out, fell to the ground, and broke my nose :-( Long story leading up to finally discovering myself on the floor. I lived alone then too.
The second event I awoke on the floor too. Different circumstances still unclear today. Again I was alone when it occurred. Another long story, of which there is still no resolve today.
The experience with the MRI itself for me is the only real challenge is you have to remain still as Susan pointed out. Both experiences my head was placed in cage. I guess they wanted to keep that mouse in its place LOL. There were times when they had me take a breath, hold it while remaining still, and then the imaging occurs.
For me the noise was definitely loud. A few of the scannings were somewhat longer than other ones. I put into effect meditation practices to remain still and calm. So, really my mind was not there kinda' except when they would ask me to hold my breath. Then I was within a different sense of awareness.
I just pretended I was being transported to another planet or somewhere in space. The contraption kinda' gives one that Start Trek feeling in a way of being in the transporter room. I pretended the voice I heard was Scotty LOL . . . Overall both experiences were not unpleasant.
I never heard or was explained anything of the first MRI, so I figured no news is good news. The second I received a copy of the summary report. That was comforting or of least better than not knowing the results. However, both times there was not really a complete experience of closure as to why I awoke on the floor. I am stumped still today :-) Oh well . . .