I'm not much help on the claustrophobia as I don't feel claustrophobic in the tube (although don't put me in a cave!). Having the ends open and having only my head in the "doughnut" makes me feel like I'm not "enclosed" in anything. But that's just me. They put a head thing on me that has a mirror so that all I can see is the room reflected in the mirror, which I'm sure would help with claustrophobia.

As far as the contrast, it is a tiny amount injected through a tiny needle and you barely feel it. Also, no side effects.

Like aarcyn said, I find the noises amusing as well. I play a game with myself trying to think of a song that has the same beat as the different sequences as they go through them.