Comparison between different software programs and post-processing techniques for the MRI quantification of liver iron concentration in thalassemia patients

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). 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 (Delta LIC) were calculated using the subset of 34 serial MRIs. After Bland-Altman analysis on baseline data, Quanta Hematology, which employs the monoexponential-plus-constant fit, produced the lowest mean difference [0.01 +/- A 0.14 log(mg/g(dw))] 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 +/- A 2.6 mg/g(dw)). Using FerriScan as reference, the value of concordant directional Delta LIC changes was the same for all programs (27/34, 85.7 %). R2* LICs are higher than R2 LICs at iron levels < 7 mg/g(dw), 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.