Just to quickly add my 2c worth - I have had a couple of MRI sessions (to discover the cause of sudden attacks of paralysis, which were finally diagnosed as hemiplegic migraine attacks) & I must say that I felt absolutely dreadful afterwards; disoriented, nauseous; shaky - I had to really concentrate to avoid leaving the body during the session, too. I have never heard such a noise, either - I have very sensitive hearing & despite earplug & earphones I really did not enjoy the experiences. So I am not convinced of the validity of MRI for disloging negs. . .