I reported some past dizziness and fainting to our general practitioner the last time we were in for a checkup. “Just to be sure,” he ordered an MRI test for me. The procedure will be tomorrow morning.
Clickable image: Siemens MRI 1.5 Tesla that I expect to see in the radiology unit tomorrow morning
I had an MRI way back in 1994 after a serious throat abscess and remember it was an unpleasant experience being sent up a narrow tunnel into a clattering, clanking, claustrophobic contraption which caused me to threaten the technician’s well being should he ever send me up there again.
I am still anxious about the matter, so I did some on-line research and am pleased to learn that the state of the art over the past 22 years has improved. The apparatus depicted above is a far cry from the monstrous “tunnel of doom” that I recall from that previous encounter.
I found some helpful information about MRI scanning from Caltech: How does an MRI work, and why is it so noisy?
An MRI is noisy because its magnetic field is created by running electrical current through a coiled wire—an electromagnet. When the current is switched on, there is an outward force all along the coil. And because the magnetic field is so strong, the force on the coil is very large.
When the current is switched on, the force on the coil goes from zero to huge in just milliseconds, causing the coil to expand slightly, which makes a loud “click.” When the MRI is making an image, the current is switched on and off rapidly. The result is a rapid-fire clicking noise, which is amplified by the enclosed space in which the patient lies.
Read [more] about how MRI works. This is the best simple description I found on MRI and how it works.