Critical examination of Fe8 as a contrast agent for magnetic resonance imaging

Abstract

The compound Fe8 (C36H120O 23N18Fe8Br8) was examined for its potential as a contrast agent for magnetic resonance imaging. The compound was prepared, isolated, and shown to exhibit superparamagnetism (S = 10). The structure of Fe8 in aqueous solution was probed by several NMR techniques. Relaxivity of aqueous solutions of Fe8 as well as that of comparison compounds FeCl3, FeCl3(tacn) (tacn = 1,4,7-triazacyclononane), and Gd(DTPA) (DTPA = diethylenetriamine pentaacetic acid) were determined by T1 and T2 inversion recovery and CPMG sequences. In contrast to a previous report, the relaxivity of Fe 8 solutions was found to be weak compared to Gd(DTPA). However, an interesting dependence upon pH was observed. The influence of environmental factors on relaxivity is of interest in the burgeoning field of molecular imaging. Show more