I don't think MRI technicians do that bondage thing here in the USA. I've had MRIs done for the last three years at five different centers and while they put little blocks next to my head, that's it. Plus a real popular option here in USA is the new open tube MRI plus MRI where you can stand up.
It was only for my radiation treatments that they used a mask and bolted me to the table. Never for a CT, a MRI or a PETscan.
We'll see what other posters have to say
Keep the faith
Charm