Fig. 4

T2-weighted MR images and in vivo cell tracking. Magnetized cells can be detected as hypointense signals (dots): e is FeNdB magnets (8 mm × 2 mm) with a magnetic field of 0.5 T. a–d the SPIONs-MSCs + magnetic field group, MR images were taken at 0 h (a), 24 h (b), 48 h (c), and 7 d (d) after cell transplantation, the MRI image in (b) confirms that labeled stem cells (low signal distribution) entered into the trauma center within the first 24 h. e–h SPIONs-MSCs group without magnetic field, MR images were taken at 0 h (e), 24 h (f), 48 h (g), and 7 d (h) after cell transplantation, the 24-h and 48-h MRI images in this group do not demonstrate a low signal area, corresponding to the skin surrounding the wound