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BACKGROUND: Quantitative T2* MRI is the standard of care for the assessment of iron overload. However, patient motion corrupts T2* estimates. PURPOSE: To develop and evaluate a motion robust, simultaneous cardiac and liver T2* imaging approach using non-Cartesian, rosette sampling and a model-based reconstruction as compared to clinical-standard, Cartesian MRI. STUDY TYPE: Prospective PHANTOM/POPULATION: Six ferumoxytol containing phantoms (26 −288 μg/mL). Eight healthy subjects and 18 patients referred for clinically indicated iron overload assessment. FIELD STRENGTH/SEQUENCE: 1.5T, 2D Cartesian and rosette gradient echo (GRE) ASSESSMENT: GRE T2* values were validated in ferumoxytol phantoms. In healthy subjects, test-retest and spatial coefficient of variation (CoV) analysis was performed during three breathing conditions. Cartesian and rosette T2* were compared using correlation and Bland Altman analysis. Images were rated by 3 experienced radiologists on a 5-point scale. STATISTICAL TEST: Linear regression, ANOVA and paired student t-testing were used to compare reproducibility and variability metrics in Cartesian and rosette scans. Wilcoxon rank test was used to assess reader score comparisons and reader reliability was measured using intraclass correlation analysis. RESULTS: Rosette R2* (1/T2*) was linearly correlated to ferumoxytol concentration (r(2) =1.00) and not significantly different than Cartesian values (p=0.16). During breath-holding, ungated rosette liver and heart T2* had lower spatial CoV (liver: 18.4 ± 9.3% Cartesian, 8.8 ± 3.4% rosette, p=0.02, heart: 37.7 ± 14.3% Cartesian, 13.4 ± 1.7% rosette, p=0.001) and higher quality scores (liver: 3.3 [3.0–3.6] Cartesian, 4.7 [4.1–4.9] rosette, p=0.005, heart: 3.0 [2.3–3] Cartesian, 4.5 [3.8–5.0] rosette, p=0.005) compared to Cartesian values. During free-breathing and failed breath-holding, Cartesian images had very poor to average image quality with significant artifacts whereas rosette remained very good, with minimal artifacts (p =0.001). DATA CONCLUSION: Rosette k-sampling with a model-based reconstruction offers a clinically useful motion robust T2* mapping approach for iron quantification. |
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