"Thermal physics may also help us to understand the power density spectrum as a function of frequency. Thermal emission and absorption by the human head (or the mineral oil phantom) which resulted in a blackbody-like power density spectrum in the microwave and radiofrequency region could explain the reduced RF power findings at 8 T. Assuming that a thermal process is involved, application of Wein's Law of Displacement would yield an "apparent temperature" of less than 1K for the human head. This result is incongruent with actual temperature measurements and would most likely occur due to the inappropriate application of Wein's law to samples that are primarily, or strictly, liquids. Clearly, Planck's blackbody radiation curve, Stephan's Law of emission and Wein's Law of displacement are applicable only to a solid. Unlike a solid, the lattice in a liquid is not rigidly confined. This may distort both the shape and the position of the thermal curve. In addition, electrostatic interactions in liquids and the presence of hydrated ions and the like may distort the curve from being truly blackbody. In any case, it is clear that the application of Planck's, Stephan's and Wien's laws to phases other than a known solid would constitute a serious misapplication of these laws. Interestingly however, it is relatively certain that if NMR could be performed on a solid at infrared frequencies, that the power density spectrum would be strictly dominated by Planck's blackbody radiation curve. Under these circumstances, application of Wien's Law should yield a reasonable temperature. In any case, it is very likely that RF power, ISNR, and RF penetration in MRI are all seriously affected by the thermal nature of this experiment and are not simply a manifestation of EM theory. Since heat exchange is involved, experimental circumstances that modulate the relative importance of conduction, convection and thermal radiation are likely to shed additional light on these critical parameters. As such, it appears that NMR may provide scientist with a unique tool, not only to continue advancing the frontiers of human medicine, but also to answer fundamental questions relative to thermal physics."
P.-M. L. Robitaille, Proc. Phys. Phenon. High Magnetic Fields-III.