How to render a radial field in OpenGL?

Is it possible to increase the ratio of spin up states to spin down states of polarizable nuclei in a magnetic field, beyond the thermal average, without changing the temperature? If so, how?

• Boltzmann statistics (http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution) give us a specific ratio of spins in the up state to spins in the down state, which is directly proportional to the magnetic field and has a known dependence on the temperature. If we change the temperature, we can manipulate the ratio, but if it's to image a human or animal, we can't change the temperature much. We can change the magnetic field, but it becomes unfeasible to use fields beyond say 10T, especially for human applications ... Is there any trickery that can be done even in theory to manipulate the situation, maybe something akin to using some type of energy to introduce a third state to render a population inversion possible, as occurs in lasers? You can get creative and speculate as long as you provide some rationale for the answer. There is no known solution out there (or else people would have used it).

• Answer:

  Whether this will work is pure speculation on my part, but here's the best I could think of. You could periodically switch the direction of the magnetic field at a timescale which is long enough to allow the system you're considering to attain equilibrium but short enough to be negligible at the timescales at which you'll be operating the machine you have in mind. By adjusting the fraction of the time the magnetic field spends in a certain direction, you can tune the (time-averaged) ratio of the number of up spins to that of down spins to any number between the Boltzmann ratio and its inverse.