Figure 1.

In vitro measurements using capillary tubes filled with PBS and USPIO at concentrations of 0.36, 0.9, 1.8, 2.39, 4.48 and 8.95 mM Fe (dilutions of Molday ION™ in PBS: 1/500, 1/200, 1/100, 1/75, 1/40 and 1/20). (A), GE image showing the appearance of signal loss at 1.8 mM and susceptibility artifact originating at 4.48 mM. (B), Relative intensities from each tube as a function of Fe concentration of USPIO. (C), (ΔR2*) vs. Fe concentration of USPIO. Slope = 106×103 (±5×103) s−1M−1. The point marked by asterisk is inaccurate estimate resulting from signals approaching noise at USPIO concentration of 4.48 and above.