T1 and T2 are relaxation times . By distinguishing between the relaxation times of different tissues, computers can determine the type of tissue and thus produce an image. T1 images are produced by rapidly turning the radio pulse on and off. As a result T1 tissue continuosly energise and relax, while T2 are too slow. T2 weighted images are produced by slowly turning the radio pulse on and off. This is so that watery tissue would have time to relax and inturn emit the pusle back for imaging. In this case watery tissues appeear bright.
decent explanataion thx homijoe just curious as well... has there been any question in trial or past hsc on T1 and T2, beacuse i can't really find any as well, so that i can just practice to get the juist of it and all
I think T1 is the time it takes for the nuclei to transfer the energy to the surrounding molecules, and T2 is the time it takes for the nuclei to revert to out-of-phase precession through the exchange of energy.
Watery tissue takes longer in both, as they move faster than large molecules and it's hard for them to exchange energy. So since T1 weighted images measure bright spots as short T1 and T2 weighted images measure bright spots as a long T2, water is dark in T1 and bright in T2, fat the other way around.
The whole MRI is the most confusing thing in this topic...