MRI

[nickglyn]

Hey. So just quickly, I'm getting confused between the antiparallel alignment of protons to the parallel alignments. I know that the antiparallel protons have more energy (for some quantum effects we aren't taught in hsc), and that for a given magnetic field, the hydrogen atoms precess at the Lamour frequency. But what i don't get is, when the doctors shine beams of radio waves over the patient exact to the Lamour frequency, do just the antiparallel protons absorb this energy and release it, or do both parallel and anti parallel absorb and release it? Thanks!

[jamonwindeyer]

Hey. So just quickly, I'm getting confused between the antiparallel alignment of protons to the parallel alignments. I know that the antiparallel protons have more energy (for some quantum effects we aren't taught in hsc), and that for a given magnetic field, the hydrogen atoms precess at the Lamour frequency. But what i don't get is, when the doctors shine beams of radio waves over the patient exact to the Lamour frequency, do just the antiparallel protons absorb this energy and release it, or do both parallel and anti parallel absorb and release it? Thanks!

Hey! I think it is actually a little more complicated than what HSC Physics teaches, but for us, parallel aligned protons are where the energy is absorbed, thus flipping them into anti-parallel alignments

[nickglyn]

okay awesome. So they are the absorbers and when the radio signal is turned off, they release the energy and go back to parallel? (and the rate at which the radio signal is turned off determines the relaxation time?)

[jamonwindeyer]

okay awesome. So they are the absorbers and when the radio signal is turned off, they release the energy and go back to parallel? (and the rate at which the radio signal is turned off determines the relaxation time?)

Spot on