[Imaging of magnetically labeled single-cell by 7.0 T MR]

To detect magnetically labeled single cells in vitro by using 7.0T MRI system and to optimize the parameters used for labeled cell imaging.

The endothelial cells ECV-304 were incubated with self-synthesized Fe2O3-PLL Prussian blue stain was employed for identifying intracellular irons. Agarose phantoms of dispersed labeled cells were made with an cell concentration of 2 x 10(3)/ml. 3D-FLASH sequence was employed for the detection of single cells and the cell concentration calculated by counting the number of dark points in MR images; The investigators compared the effects of gradient echo sequence (2D-FLASH) and spin echo sequence (MSME) upon the imaging of magnetically labeled single cells; Also the effects of different echo times (Es) and resolutions of magnetic nanoparticle relaxation upon the imaging of cells were analyzed.

The endothelial cells ECV-304 were labeled successfully and the labeling efficiency reached almost 100%. Prussian blue staining of Fe2O3-PLL labeled cells revealed the cytoplasmic presence of iron. Single cells were detected as isolated dark points and the cell concentration corresponded with the actual data. The 2D-FLASH sequence had a much stronger T2* effect than MSME sequence in single cell detection. The T2* effect increased with the prolongation of TE. The signal loss fell significantly as the resolution decreased. And it reached almost zero when the voxel size reached 200 microm3.

7.0T MR system is able to detect magnetically labeled single cells. The optimization of imaging sequences enhances the sensitivity of magnetically labeled single cells. Thus it provides a better method for in vivo detection of single cells.