The noise can be mildly unsettling but it doesn’t last long. I kept my eyes shut and had earphones (that the staff provided) that played Mozart (there was a huge selection of music.
Deep breathing helps any tendency towards claustrophobia. In some areas there are MRI tubes that are open at both the foot and head ends. Ask your doctor what’s available at your hospital.
My bro-ion-law was allowed in during my sister’s MRI; he held one of her feet and that was helpful. Personally, i would not have liked that.
I also reminded myself that the modern technology that allows people to see my insides in detail is really phenomenal.