The T2 relaxation time of protons in water suspensions of iron-oxide particle clusters is found to increase with the waiting time tw after the sample is inserted in the gap of the magnet with 1.41 T field, owing to field induced cluster aggregation. In order to compare the experimental results with existing theories, the measured T2 has to be extrapolated to tw = 0, for which a power-law T2 increment versus tw relation is proposed. The extrapolated T2 (0) is found to be inversely proportional to the volume fraction v of iron oxide. © 2009 Elsevier B.V. All rights reserved.
- Field induced cluster aggregation
- MRI contrast agent
- Superparamagnetic particle
- T relaxation time 2
- Waiting time dependence