Table 1.

Essential elements to consider for MRI cell tracking studies

Elements	Brief description
Labeling agent	Physicochemical and magnetic properties
Cell information	Cell source, cell type, activation status, culture condition, antigen loading, etc.
Labeling condition	Medium, cell density/number, labeling agent concentration and incubation time
Cell labeling evaluation
Labeling efficiency	% of labeled cells in total and Fe/cell
Intracellular localization	Lysosomes, cytoplasm, nuclei, etc.
In vitro characterization
Label retention	Especially in dividing or long-lived cells
Detection limit	Cells/voxel at a given field strength
Cytotoxicity	Mainly the adverse effect on cell function,
In vivo analysis
Cell implantation	Cell number, route, and control
Monitorable period	Period from implantation to the time undetectable
Label clearance	Clearance of label from both living and dead cells
Imaging protocol	Detail imaging parameters
Outcome evaluation
Functional outcome	Influence on cell function in vivo
Side effects	Acute and long-term effect on host
Validation	e.g. histology, flow cytometry on biopsy samples