The sensitivity of magnetic particle imaging and fluorine-19 magnetic resonance imaging for cell tracking.

Magnetic particle imaging (MPI) and fluorine-19 (F) MRI produce images which allow for quantification of labeled cells. MPI is an emerging instrument for cell tracking, which is expected to have superior sensitivity compared to F MRI. Our objective is to assess the cellular sensitivity of MPI and F MRI for detection of mesenchymal stem cells (MSC) and breast cancer cells. Cells were labeled with ferucarbotran or perfluoropolyether, for imaging on a preclinical MPI system or 3 Tesla clinical MRI, respectively. Using the same imaging time, as few as 4000 MSC (76 ng iron) and 8000 breast cancer cells (74 ng iron) were reliably detected with MPI, and 256,000 MSC (9.01 × 10F atoms) were detected with F MRI, with SNR > 5. MPI has the potential to be more sensitive than F MRI for cell tracking. In vivo sensitivity with MPI and F MRI was evaluated by imaging MSC that were administered by different routes. In vivo imaging revealed reduced sensitivity compared to ex vivo cell pellets of the same cell number. We attribute reduced MPI and F MRI cell detection in vivo to the effect of cell dispersion among other factors, which are described.