NMR and MRI -- questions! I'm currently doing an experiment on nuclear magnetic resonance for an undergrad physics lab. Our experiment was based around determining the effects of proton concentration on spin-lattice and spin-spin relaxation times. We used two separate sets of ionic solutions (cupric sulfate solutions and ferric nitrate solutions.) To analyze the results I'll be looking at T1 and T2 vs. concentration level as well as the supposed 1/T1 1/T2 relaxivity vs concentration. My problem is I can find little to no theory whatsoever that describes to me in detail the importance of relaxivity. I'm aware that relaxivity affects contrast in MRI images and to what extent it can do so, however I'm not sure about what makes a substance good for T2 imaging versus good for T1 imaging? I guess in short, other than that main question at the end, I'm looking for sources about MRI relaxivity theory. Any help would be greatly appreciated. EDIT: Sorry about posting this in the main forum. Since I was just looking for sources on MRI theory, I thought it'd be just as fine to post in the general forum.