T2* weighted MRI images of mice bearing 4T1 before, 5 min and 24 h after i.v. injection of MNP-VEGF (A,B,C), MNP-IgG (D,E,F) and MNP (G,H,I). Contrast-to-noise ratio of regions that accumulated MNP 24 h after i.v. injection (J). * – difference is significant (t-test, p<0.05), ** – difference is insignificant (t-test, p>0.05).