Hepatic Iron Deposition in Liver Disease -- Which Method Works Best? Quantification of Hepatic Iron Deposition in Patients With Liver Disease: Comparison of Chemical Shift Imaging With Single-Echo T2*-Weighted Imaging

Objective: To determine if chemical shift imaging is comparable to single-echo T2*-weighted imaging in the quantification of hepatic iron, and if coexisting steatosis affects its performance. Design: Retrospective analysis. Participants/Methods: This study was comprised of 63 patients (50 men and 13 women) who had undergone MRI of the liver and concomitant histopathologic analysis within 90 days of the MRI. Histopathologic results were provided by explant analysis, core biopsy, or segmentectomy. Clinical histories included chronic hepatitis B or C, alcohol abuse, cryptogenic cirrhosis, autoimmune hepatitis, primary sclerosing cholangitis, primary hemochromatosis, abnormal liver function tests, obstructive jaundice, end-stage renal failure, and sarcoidosis. MRI examinations were performed on 1.5T systems. Routine liver protocol sequences included T2 HASTE, T2weighted fat-suppressed 2D chemical shift, and fat-suppressed 3D T1-weighted imaging before and during dynamic contrast administration. Of the 63 patients, 49 also had a 2D single-echo T2*-weighted sequence. Images were reviewed by 2 observers. Regions of interest were drawn to measure hepatic signal intensity, avoiding any focal lesions and vessels. Paraspinal muscle signal intensity was used as an internal reference while avoiding any areas of macroscopic fat and signal loss on out-of-phase images. The spleen was not used due to possible iron deposition. An iron index was calculated for the chemical shift sequence and for the T2*weighted sequence. Two histopathologists quantified the degree of iron deposition and hepatic steatosis. Iron deposition was graded as follows: grade 0, iron granules absent or barely visible at 400x magnification; grade 1, granules barely visible at 250x magnification; grade 2, granules resolved at 100x magnification; grade 3, granules visible at 25x magnification; and grade 4, granules visible at 10x magnification or to the naked eye. Results: 47 of 63 patients had hepatic iron deposition. Cirrhosis was more prevalent among patients with a histopathologic iron deposition grade of 2 or greater. No significant correlation was found between iron grade and degree of inflammation or stage of fibrosis in patients with chronic viral hepatitis. With increasing iron deposition, there was an increase in the chemical shift iron index and a decrease in the T2* iron index. The accuracy of both chemical shift and T2* sequences in detecting hepatic iron deposition was decreased in the presence of steatosis. Reviewer's Comments: The results of this study demonstrate that both chemical shift imaging and singleecho T2*-weighted imaging are comparable in the detection of significant hepatic iron deposition. However, one must keep in mind that the concomitant presence of steatosis decreases the accuracy of both sequences. One of the limitations reported in this study was that the use of core biopsy in some patients can lead to potential sampling error and, consequently, an imperfect reference standard. (Reviewer-John C. Sabatino, MD).