T 1 independent, T 2 * corrected MRI with accurate spectral modeling for quantification of fat: Validation in a fat‐water‐SPIO phantom

Purpose: To validate a T 1 ‐independent, T 2 *‐corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat‐water‐SPIO phantom over physiologically expected ranges of fat percentage and T 2 * decay in the presence of iron overload. Materials and Methods: A homogeneous gel phantom consisting of vials with known fat‐fractions and iron concentrations is described. Fat‐fraction imaging was performed using a multiecho chemical shift‐based fat‐water separation method (IDEAL), and various reconstructions were performed to determine the impact of T 2 * correction and accurate spectral modeling. Conventional two‐point Dixon (in‐phase/out‐of‐phase) imaging and MR spectroscopy were performed for comparison with known fat‐fractions. Results: The best agreement with known fat‐fractions over the full range of iron concentrations was found when T 2 * correction and accurate spectral modeling were used. Conventional two‐point Dixon imaging grossly underestimated fat‐fraction for all T 2 * values, but particularly at higher iron concentrations. Conclusion: This work demonstrates the necessity of T 2 * correction and accurate spectral modeling of fat to accurately quantify fat using MRI. J. Magn. Reson. Imaging 2009;30:1215–1222. © 2009 Wiley‐Liss, Inc.