What causes the loud banging noises during MRI’s?
ANSWER PERSON RESPONDS: Most hospital web sites just tell you to expect the noises during the procedure and to wear earplugs or listen to music. AP calls this leap of faith the “banging happens” explanation.
One lab says “the imaging process involves the stimulation of molecules with sound waves. The banging noises that you will hear are the sound waves that are emitted by the machine.” http://www.babradiology.com/mri.html#6 This tautologous statement is technically true (sound waves make you hear sounds). But what’s *causing* the sound waves?
Another web site says, “The noise is caused by the magnets moving.” http://www.healthtouch.com/bin/EContent_HT/cnoteShowLfts.asp?fname=02601&title=MAGNETIC+RESONANCE+IMAGING+&cid=HTHLTH Apparently true, but still pretty lame, huh?
As usual, an .edu web site (at Cornell) provides the most thorough explanation, yet still in layman’s terms, summarized by “The clicking and banging sounds you hear are the various coils [of the electromagnet] being turned on and off.”
http://www.ccmr.cornell.edu/education/ask/?quid=41 There’s a lot more detail about hydrogen atoms, the energy causing the magnets to move, etc., on this web page.