SPIO-induced susceptibility effects on quantitative liver MRI: cross-method assessment of R2*, PDFF, T1 mapping, and MRE.

OBJECTIVES

To compare hepatic and splenic transverse relaxivity (R2*) derived from two-dimensional (2D) and three-dimensional (3D) multi-echo gradient-echo (ME-GRE) acquisitions before and after superparamagnetic iron oxide (SPIO) administration and to evaluate the effects of SPIO on proton density fat fraction (PDFF), MR spectroscopy (MRS)-derived PDFF, native T1 mapping, and magnetic resonance elastography (MRE)-derived liver stiffness.

MATERIALS AND

METHODS

In this retrospective study, 48 adults underwent liver MRI at 3 T before and after SPIO administration. Hepatic and splenic R2* and PDFF were obtained from 2D and 3D ME-GRE acquisitions processed using MRQuantif and LiverLab. MRS-derived PDFF, native variable flip angle T1 mapping, and MRE-derived liver stiffness were assessed before and after SPIO administration. Agreement between methods was evaluated using Pearson correlation coefficients, intraclass correlation coefficients (ICC), and Bland-Altman analysis. Predictors of SPIO-induced changes were assessed using multivariable linear regression.

RESULTS

SPIO administration resulted in a marked increase in hepatic R2* (approximately 3.5-fold), exceeding the increase observed in the spleen (approximately 2-fold), consistent with predominant hepatic uptake. Correlation between LiverLab and MRQuantif R2* measurements remained strong; however, inter-method agreement deteriorated at higher R2* values after SPIO administration. ME-GRE-based PDFF measurements remained stable with preserved inter-method agreement. In contrast, MRS-derived PDFF demonstrated reduced reliability after SPIO administration, with apparent increases in fat fraction and weakened correlation with ME-GRE PDFF measurements. Native hepatic T1 values decreased uniformly by approximately 500 ms following SPIO administration. MRE-derived liver stiffness showed no significant change after SPIO administration.

CONCLUSION

Using SPIO as a controlled in vivo susceptibility model, this study provides an integrated evaluation of the susceptibility dependence of commonly used quantitative liver MRI biomarkers. SPIO-induced susceptibility effects substantially increase hepatic R2*, impair the reliability of MRS-based fat quantification, and markedly shorten native variable flip angle T1 measurements, while preserving the relative stability of ME-GRE-based PDFF and MRE-derived liver stiffness. These findings improve understanding of the susceptibility-related performance of quantitative liver MRI techniques and may help inform the interpretation and standardization of iron-sensitive MRI biomarkers.