How is math used in MRI? - Answers

Inside the 'donut' of the MRI machine are a huge number of RF (radio frequency) sources and RF detectors. After the sources shoot a short, powerful pulse of RF into you, the sources shut off, and the tissues throughout your body "ring", in response to the RF they've absorbed, combined with the powerful field of the giant permanent magnet that's also all around you inside the donut. The detectors listen to the 'ringing' of your body's tissues from a huge number of different directions, all around the ring. Each detector hears a ring of a slightly different level, and hears it fade out after a slightly different time. The signals that are heard by all of the detectors are compared and combined to give a picture of what's inside you. The basic concept of forming the image is the same as in other forms of "tomography" ... the CT scan, using X-rays instead of RF, and the PET scan, using positron emission from a radioactive substance. The math is incredibly complex in each case. On a completely irrelevant note, but one which I can't bring my self to conclude without mentioning ... probably my only claim to fame is the fact that my brother-in-law is one of the names on the original patent granted to GE for the computed tomography process, and his sister was involved in some good-science early MRI research when we met in the late 70s. Those facts and several nickels have bought me many cups of coffee through the years ever since.