Purpose: In magnetic resonance imaging (MRI) relaxometry, various software programs are available to perform R2* measurements and to estimate the liver iron concentration (LIC). The main objective of our study was to compare R2* LIC values, obtained with three different software programs based on specific decay models and calibration curves, with LIC estimates provided by R2-relaxometry (FerriScan).
Methods: This retrospective study included 15 patients with 15 baseline MRIs and 34 serial examinations. R2* LIC estimates were calculated using the FuncTool, CMRtools/Thalassemia Tools and Quanta Hematology programs. Longitudinal LIC changes (ΔLIC) were calculated using the subset of 34 serial MRIs.
Results: After Bland-Altman analysis on baseline data, Quanta Hematology, which employs the monoexponential-plus-constant fit, produced the lowest mean difference [0.01 ± 0.14 log(mg/gdw)] with the closest limits of agreement. In the longitudinal setting, Quanta Hematology again gave the lowest mean difference between R2 and R2* LIC (0.1 ± 2.6 mg/gdw). Using FerriScan as reference, the value of concordant directional ΔLIC changes was the same for all programs (27/34, 85.7 %).
Conclusions: R2* LICs are higher than R2 LICs at iron levels <7 mg/gdw, while R2 LIC averages higher than R2* LIC with increasing iron load. The monoexponential-plus-constant model provided the best agreement with R2 LIC estimates.
Keywords: Biopsy; Liver iron concentration (LIC); Liver iron overload; Magnetic resonance imaging; β-Thalassemia.