If you ever get an MRI, the test is done in this tubular contraption
which is much like a cave or culvert. You are strapped in to a table top like slab and it slides in to the enclosure. They have newer
machines which do not surround you entirely, allowing light and air to enter, which makes many patients much more comfortable with the procedure..that and they also offer tranquilizers. It is quite common to find people who have problems with being in enclosed spaces. At least one in ten as i recall. (magnetic Resonance imaging is also a procedure that has noises and vibrations which may be unsettling to some patients.)