Purpose or Case Report: MRI can accurately quantify liver iron concentration (LIC) by using T2* sequences. Vendor based, commercially available 3D multi-echo Dixon sequences provide maps of liver T2*/R2* and allow automated, inline post-processing, avoiding conventional manual post-processing. The purpose of our study was to compare R2*/LIC estimates generated by automated 3D multi-echo Dixon sequence to values generated by GRE-based R2* relaxometry as the reference standard.
Methods & Materials: Retrospective review of patients who had undergone MRI scans for liver iron estimation with both conventional GRE based T2* relaxometry and 3D multi-echo Dixon sequences was performed. All MR studies were performed on a 1.5T scanner. Standard multi-slice multi-echo T2* based sequences were acquired and R2* values with corresponding LIC were estimated. The 3D multi-echo Dixon technique was performed using LiverLab (Siemens Healthineers). The comparison between R2* and corresponding LIC estimates obtained by the two methods was performed via the correlation coefficients and Bland-Altman difference plots.
Results: 86 patients (43M; 43F) with125 MRI scans were included in this study. 33 patients had repeat scans. The mean age of the patients at the time of scan was 15.2 years (SD: 9.6 years) and the age range of the patients was 0.1 to 59.4 years. A strong correlation was found between LIC GRE and LIC q-Dixon using ROI R2* (r = 0.88, p < 0.01), with the Bland–Altman LIC difference plot between the two methods showing a mean bias of + 1.18 mg/gm (range: -1.84 to + 4.2 mg/gm). Analysis of a smaller subset with MRI exams having LIC ≤ 6 mg/g (N=78) provided a correlation coefficient of r = 0.77, p < 0.01 between the multi echo 3-D Dixon method and in-house method (GRE) for LIC. A correlation of r=0.80 (p<0.01) was found between LIC GRE method and LIC q-Dixon estimated using Segmentation Volume R2* values. Analysis of a smaller subset with MRI exams having LIC ≤ 4 mg/g (N=56) provided a correlation coefficient of r = 0.83, p < 0.01 between the LIC q-Dixon estimated using Segmentation Volume R2* and LIC GRE.
Conclusions: 3D based multi-echo Dixon technique can accurately measure LIC in mild to moderate iron overload and has the potential to replace GRE based relaxometry methods.