Seung Soo Lee MD, Presenter: Nothing to Disclose

Youngjoo Lee MS, Abstract Co-Author: Nothing to Disclose

Namkug Kim PhD, Abstract Co-Author: Nothing to Disclose

Eun Sil Yu MD, Abstract Co-Author: Nothing to Disclose

Seong Ho Park MD, Abstract Co-Author: Research Consultant, INFINITT Healthcare Co, Ltd

Moon-Gyu Lee MD, Abstract Co-Author: Nothing to Disclose

Jae Ho Byun MD, Abstract Co-Author: Research Consultant, Bayer AG

Cheol Mog Hwang MD, Abstract Co-Author: Nothing to Disclose

To evaluate the effect of iron deposition on the fat quantification using chemical shift gradient-echo MR imaging (CS-MRI) and the efficacy of T2*-correction algorithms for minimizing the confounding effect of iron.

CS-MRI with six opposed- and in-phase acquisitions and MR spectroscopy (MRS) with five-echo acquisitions were performed at 1.5T for the phantoms with varying fat fractions (FFs) (0-50%), the 10% fat phantoms with varying iron concentrations (0-14.0μg/ml), and 18 patients with chronic liver disease. For CS-MRI, FFs were estimated with the dual-echo method, with the two T2*-correction algorithms (triple-echo and multi-echo methods), and with multi-interference method incorporating both T2*-correction and fat-fat signal interference. For MRS, T2-corrected FF was calculated using an exponential least-squares fitting algorithm. The 95% Bland-Altman limits-of-agreement (LOA) were calculated for each CS-MRI method with the true FFs of the phantoms and MRS FFs as reference standards for the phantom experiments and for the patient study, respectively.

In the phantoms with varying FF, MRS provided the most accurate estimation of FF (95%-LOA, -0.2%±1.2), followed by multi-interference (0.4%±1.6), multi-echo (-1.1%±2.2), triple-echo (-1.0%±4.0), and dual-echo CS-MRI methods (-5.5%±2.9%). In the phantoms with varying iron concentration, dual-echo method underestimated FFs in proportion to the iron concentration (the absolute error range, -11% to 5%), whereas the other three CS-MRI methods accurately estimated FF (the absolute error range, -0.8% to 0.3%), regardless of iron concentration. In 18 patients with chronic liver disease, the FFs estimated with triple-echo (95% LOA, 0.6%±1.8), multi-echo (-0.5%±1,4), and multi-interference CS-MRI (0.3%±1.6) had closer agreements with the MRS FFs, compared with dual-echo CS-MRI (-3.9%±6.9).

Hepatic iron deposition causes a significant bias in fat quantification using dual-echo CS-MRI, while triple-echo, multi-echo, and multi-interference CS-MRI methods are effective in minimizing the confounding effect of iron and thus enable accurate fat quantification throughout the physiologic range of iron deposition.

CS-MRI with T2*-correction algorithms may be a useful clinical tool for noninvasive evaluation of hepatic fat in patients with chronic liver disease or those with hepatic iron overload.

Lee, S, Lee, Y, Kim, N, Yu, E, Park, S, Lee, M, Byun, J, Hwang, C, Minimizing the Confounding Effect of Iron Deposition on the Fat Quantification Using Chemical Shift Gradient-echo MR Imaging: The Validation of T2*-Correction Algorithms with the Phantom Experiments and the Patient Study.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9003722.html