Table 3.

MRI intensity differences after 21-hour USPIO incubation.

USPIO dose	1 × 106 cells	5 × 105 cells	2.5 × 105 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.