I just had an MRI for my back, and you know... that's what it must feel like to be buried alive. In a word: torture. I'm a large man (6'4", 230lbs) and so the experience was not unlike being shoved head-first into a toilet paper tube. Not the cardboard thing -- but the smaller cylindrical roller that actually goes inside the cardboard tube and holds the toilet paper. And then the whole deal is dropped inside of a jackhammer.
UPDATE: Wow. I fractured my T11 vertebra. My first serious cycling injury.