Waiting time dependence of T2 of protons in water suspensions of iron-oxide nanoparticles: Measurements and simulations

摘要

The transverse relaxation time T_2 of protons in water suspensions of iron-oxide particles increases with the waiting time t_w after the sample is inserted in the gap of the spectrometer magnet. Such a T_2 increase becomes significant if the particles are aggregated into large clusters, for which field-induced formation of cluster-chains will occur and T_2 should increase with increasing the length of chains. T_2 increases with t_w even for small particles, for which no chain formation may be induced, and for large clusters when t_w is too small to form long enough chains. The T_2 increase is accompanied by a significant echo-time dependence. All this is experimentally and theoretically studied.