To compare automated six-point-Dixon(6-p-Dixon) with dual-echo GRE chemical shift imaging(CSI) for quantification of hepatic fat fraction(FF) with CT. In a phantom study, various FF vials were performed to validate the accuracy. In clinical study, fifty-nine patients were examined both 3.0T MRI and CT. Quantitative measurements were calculated SI-index of CSI and imaging-FF of 3D-6-p-Dixon. In phantom study, linear regression between FF and imaging-FF/SI-index showed good agreement(imaging-FF R2=0.992:0-100%FF;SI-index R2=0.978:0-34.7%FF). In clinical study, linear regression between imaging-FF and SI-index showed good agreement(R2=0.890). CT attenuation value was strongly correlated with imaging-FF(R2=0.852) and SI-index(R2=0.812). Imaging-FF of 6-p-Dixon has potential for automated hepatic fat quantification.
Among the magnetic resonance (MR) imaging methods to date, chemical shift-based multipoint water-fat separation methods have been most widely used, the two-point Dixon methods utilizing only magnitude data are insensitive to phase errors, but they are limited in water-fat ambiguity and lack of T2* relaxation correction.1, 2 Recently, a 3D T1-weighted gradient-echo (GRE) acquisition with six-point Dixon (6-p Dixon) is developed with automatically reconstruction of fat-only, water-only, % fat fraction (FF), R2* and T2*images at one breath-hold.3 The main idea behind this 6-p Dixon technique thereby is to have a fast liver classification method which can be used to quickly screen for hepatic iron overload or fatty liver disease. In some of the previous studies, a significant correlation between proton density fat fraction (PDFF) MR imaging and MRS determined hepatic fat fraction was observed.4-6 However in these previous studies, the reference technique for quantification of liver fat was MRS or biopsy, and the correlation of PDFF techniques with liver CT attenuation value was not well evaluated .7-10 The purpose of this study was to evaluate the automated 6-p Dixon fat quantification method screening for the detection of hepatic FF on a 3.0-T MR imaging. We compared this method with conventional dual-echo GRE chemical shift imaging (CSI) methods in a phantom validation study and in clinical study with CT as the reference technique.
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