R2∗ relaxometry for the quantification of hepatic iron overload: Biopsy-based calibration and comparison with the literature

Abstract

Purpose: We compared the calibration of hepatic iron based on R2∗ relaxometry and liver biopsy with similar studies that have already been published to investigate the transferability of published calibration curves. Materials and Methods: 17 patients with clinically suspected hepatic iron overload (HIO) were enrolled. All patients underwent liver biopsy and MRI of the liver using a multi-echo gradient echo sequence (TR = 200 ms; TE-initial 0.99 ms; Delta-TE 1.41 ms; 12 echos; flip-angle: 20 °). R2∗ parameter maps were analyzed using manually placed regions of interest and R2∗ values were correlated with liver iron concentration (LIC) obtained from liver biopsy. In addition, the results of our study were compared with 6 similar, already published studies. Results: A linear relationship between R2∗ and LIC was found. Regression analysis yielded a correlation coefficient of 0.926, a slope of 0.024 (s mg/g) [95 % CI 0.013 - 0.024] and an intercept of 0.277 (mg/g) [95 % CI -0.328 - 2.49]. We found a significant correlation between the calibration curves obtained from our study in comparison to 3/6 similar studies. The other 3 studies used a different reference standard or sequence parameters which lead to a significant difference for slope, intercept or both in comparison to our data. Conclusion: Calibration curves from published studies that are based on a correlation of liver biopsy and R2∗ can be used for the estimation of liver iron concentration, although different scanning parameters and post-processing protocols were used. Low initial TEs might be a prerequisite for pooling data for liver iron quantification. Key Points: • Calibration curves from different studies can be used for liver iron quantification • For that purpose calibration curves from published studies should be based on liver biopsy • Low initial TEs might be a prerequisite for pooling data for liver iron quantification Citation Format: • Henninger B., Zoller H., Rauch S. et al. R2∗ Relaxometry for the Quantification of Hepatic Iron Overload: Biopsy-Based Calibration and Comparison with the Literature. Fortschr Röntgenstr 2015; 187: 472 - 479.