Fig. 5.

Gradient-echo T2-weighted MR images of the phantoms with different cell numbers (i.e., 312, 625, 1,250, 2,500, 5,000 and 10,000 cells/µl). MR scans were performed at different time points with (A) the control, the MION-47 treated cells and the MION-47+PLL treated cells, (B) the ferumoxides treated cells and the ferumoxides with PLL treated cells, and (C) the CLIO-NH₂ treated cells, the CLIO-NH₂ with PLL treated cells and the tat-CLIO treated cells. In the absence of PLL, the phantoms with more than 1,250 cells/µl of the tat-CLIO-labeled cells show a decreased signal on the T2-weighted MR images. For the ferumoxides treated cells and the CLIO-NH₂ treated cells, the phantoms with more than 2,500 cells/µl show a visibly decreased signal without PLL. With PLL, a decreased signal is found in the phantoms with the ferumoxides treated cells, in the phantoms with the MION-47 treated cells and in the phantoms with the CLIO-NH₂ treated cells, with 625-1,250 cells/µl respectively. 'Control' represents the MR image of the phantom with the non-labeled control cells.