title: R2* relaxometry for the quantification of hepatic iron overload: biopsy-based calibration and comparison with the literature.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  • 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.
authors: Radiology, Medical University of Innsbruck, Austria.
authors: B
authors: B
authors: Henninger
authors: Internal Medicine, Medical University of Innsbruck, Austria.
authors: H
authors: H
authors: Zoller
authors: Radiology, Medical University of Innsbruck, Austria.
authors: S
authors: S
authors: Rauch
authors: Internal Medicine, Medical University of Innsbruck, Austria.
authors: A
authors: A
authors: Finkenstedt
authors: Radiology, Medical University of Innsbruck, Austria.
authors: M
authors: M
authors: Schocke
authors: Radiology, Medical University of Innsbruck, Austria.
authors: W
authors: W
authors: Jaschke
authors: Radiology, Medical University of Innsbruck, Austria.
authors: C
authors: C
authors: Kremser
mesh_terms: D000328:Adult; D000368:Aged; D001317:Austria; D001706:Biopsy; D002138:Calibration; D005260:Female; D006801:Humans; D019190:Iron Overload / Q000473:pathology*; D008107:Liver Diseases / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity