Plot of R2′ versus HIC. HIC was estimated by MRI (•) and by biopsy (+). Solid line represents best fit by linear regression, and dotted lines indicate 95% confidence intervals for the prediction. R2′ rises linearly with HIC at iron concentrations greater than 7 mg/g but deviates from linearity at lower iron concentrations. R value is 0.97 with respect to MRI HIC estimates and 0.96 with respect to biopsy HIC estimates. Limits of agreement of R2′ with biopsy are comparable with HIC measurements by R2^* alone (Table 1).