Hong Rui, Cima Michael J, Weissleder Ralph, Josephson Lee
Center for Molecular Imaging Research, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Magn Reson Med. 2008 Mar;59(3):515-20. doi: 10.1002/mrm.21526.
Micron-sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of MR imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time-dependent increases and decreases in the spin-spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation and exhibited time-independent values of T2. The rate of T2 change associated with magnetic microparticle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma.
微米级磁性颗粒置于均匀磁场（如磁共振成像仪和弛豫仪产生的磁场）中时会发生聚集，而从磁场中移除后又会自发恢复到分散状态。随着磁性颗粒的聚集和分散，水的自旋 - 自旋弛豫时间（T2）会随时间增加和减少。每个颗粒磁矩小得多的磁性纳米颗粒不会发生磁感应聚集，并且T2值与时间无关。利用与磁性微粒聚集相关的T2变化率来测定液体样品的粘度，提供了一种对于测定少量潜在生物危害性血液或血浆样品粘度可能具有特别优势的方法。
