Today I watched the first video lectures of the third week for Statistical Inference class, which is about Statistical Power. Better to visualize the concept by two side-by-side Gaussian distributions.
(Nishimura p.51) T2 relaxation: The pertinent frequency components of the fluctuating z fields are those near zero. These components contribute only to the T2 relaxation process and not to T1. Therefore T2 is largely independent of field strength.
In solids, the presence of relatively slow fluctuations creates a large resonant frequency broadening effect and thus extremely rapid T2 decay. In biological tissue, spins bound to lumbering macromolecules also experience rapid T2 decay while relatively mobile spins (e.g. those in water) exhibit much slower decay. However, because of rapid exchange of protons between these two types of environments, the effective T2 is some average of the two relaxation rates.
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