Figure 1

(a) Transmission electron microscope (TEM) image of 12.9 nm of carboxylic coated SPIONs. (b) TEM image of ferumoxytol. (c) Magnetization as a function of applied field for ferumoxytol, 15.7 nm Fe3O4 SPIONS, and Gd-BOPTA with vertical bars to show field regions corresponding to 64 mT (low-field MRI) and 3 T (standard clinical field). (d) Expanded region of magnetization versus applied field showing low-field regime.