Hepatic iron overload: diagnosis and quantification with MR imaging

The aim of this study was to assess the sensitivity of MR imaging in the diagnosis of liver hemochromatosis and its ability to quantify hepatic iron concentration (HIC). MR images were prospectively obtained in 58 patients suspected to have hemochromatosis. We used a scanner with a 0.5-T magnet and two sequences: gradient-echo T1-weighted (400/12 [TR/TE], 90 degrees flip angle) and gradient-echo T2*-weighted (700/30, 30 degrees flip angle) sequences. Measurement of the liver-to-muscle signal-intensity ratio was compared with the HIC value measured at biopsy for each patient. Both MR sequences showed significant correlation between decreased signal-intensity ratios and increased HIC (r = -.87 for T1-weighted sequences and r = -.74 for T2*-weighted sequences). The sensitivity and specificity of the T2*-weighted sequence (signal-intensity ratio < 0.8) to detect iron overload (HIC > 36 mumol/g) were 91% and 88%, respectively. The best correlation was obtained with T2*-weighted sequences, when patients had an HIC less than 100 mumol/g (r = -.71); with T1-weighted sequences, the best correlation was obtained when patients had an HIC of 100-324 mumol/g (r = -.67). We found a significant correlation between the HIC revealed on MR images, calculated from both sequences, and that measured at biopsy when patients had an HIC of less than 300 mumol/g (r = -.93, p < .01). MR imaging shows promise in differentiating normal from abnormal hepatic iron concentration and in grossly quantifying moderate degrees of hepatic iron overload.