Optimal Labeling Dose, Labeling Time, and Magnetic Resonance Imaging Detection Limits of Ultrasmall Superparamagnetic Iron-Oxide Nanoparticle Labeled Mesenchymal Stromal Cells

Table 3

MRI intensity differences after 21-hour USPIO incubation.

USPIO dose	1×10^6 cells	5×10^5 cells	2.5×10^5 cells
Full	249±102	135±91	100±64
Half	134±82	91±76	45±92
Unlabeled	46±58	25±47	8±53
Multiple comparisons	𝑃<0.001	𝑃=0.007	𝑃=0.008
Full versus unlabeled	𝑃<0.001	𝑃=0.006	𝑃=0.006
Full versus half	𝑃=0.034	ns	ns
Half versus unlabeled	ns	ns	ns

The MRI intensities are mean pixel intensities (values between 0 and 4095) of a 20 mm² region of interest in the center area of each phantom, supplied by the imaging software. Values are shown ± SD.
USPIO: ultrasmall super-paramagnetic iron-oxide. USPIO dose—full = 10 𝜇g per 10⁵ cells. half = 5 𝜇g per 10⁵ cells, ns: non-significant.