Measurement and correction of stimulated echo contamination in T₂-based iron quantification

The purpose of this study was to characterize the effects of stimulated echo contamination on MR-based iron measurement derived from quantitative T₂ images and develop a method for retrospective correction. Two multiple spin-echo (MSE) pulse sequences were implemented with different amounts of stimulated echo contamination. Agarose-based phantoms were constructed that simulate the relaxation and susceptibility properties of tissue with different concentrations of dispersed (ferritin-like) and aggregated (hemosiderin-like) iron. Additionally, myocardial iron was assessed in nine human subjects with transfusion iron overload. These data were used to determine the influence of stimulated echoes on iron measurements made by an MR-based iron quantification model that can separately measure dispersed and aggregated iron. The study found that stimulated echo contamination caused an underestimation of dispersed (ferritin-like) iron and an overestimation of aggregated (hemosiderin-like) iron when applying this model. The relationship between the measurements made with and without stimulated echo appears to be linear. The findings suggest that while it is important to use MSE sequences with minimal stimulated echo in T₂-based iron quantification, it appears that data acquired with sub-optimal sequences can be retrospectively corrected using the methodology described here.