• Ante Zhu, Scott B Reeder, Kevin M Johnson, Sydney M Nguyen, Thaddeus G Golos, Ann Shimakawa, Matthias R Muehler, Christopher J Francois, Ian M Bird, Sean B Fain, Dinesh M Shah, Oliver Wieben, and Diego Hernando.
• Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA.
• J Magn Reson Imaging. 2020 Feb 1; 51 (2): 580-592.

Background3D chemical shift-encoded (CSE)-MRI techniques enable assessment of ferumoxytol concentration but are unreliable in the presence of motion.PurposeTo evaluate a motion-robust 2D-sequential CSE-MRI for R2* and B0 mapping in ferumoxytol-enhanced MRI of the placenta.Study TypeProspective.Animal ModelPregnant rhesus macaques.Field Strength/Sequence3.0T/CSE-MRI.Assessment2D-sequential CSE-MRI was compared with 3D respiratory-gated CSE-MRI in placental imaging of 11 anesthetized animals at multiple timepoints before and after ferumoxytol administration, and in ferumoxytol phantoms (0 μg/mL-440 μg/mL). Motion artifacts of CSE-MRI in 10 pregnant women without ferumoxytol administration were assessed retrospectively by three blinded readers (4-point Likert scale). The repeatability of CSE-MRI in seven pregnant women was also prospectively studied.Statistical TestsPlacental R2* and boundary B0 field measurements (ΔB0) were compared between 2D-sequential and 3D respiratory-gated CSE-MRI using linear regression and Bland-Altman analysis.ResultsIn phantoms, a slope of 0.94 (r2 = 0.99, concordance correlation coefficient ρ = 0.99), and bias of -4.8 s-1 (limit of agreement [LOA], -41.4 s-1 , +31.8 s-1 ) in R2*, and a slope of 1.07 (r2 = 1.00, ρ = 0.99) and bias of 11.4 Hz (LOA -12.0 Hz, +34.8 Hz) in ΔB0 were obtained in 2D CSE-MRI compared with 3D CSE-MRI for reference R2* ≤390 s-1 . In animals, a slope of 0.92 (r2 = 0.97, ρ = 0.98) and bias of -2.2 s-1 (LOA -55.6 s-1 , +51.3 s-1 ) in R2*, and a slope of 1.05 (r2 = 0.95, ρ = 0.97) and bias of 0.4 Hz (LOA -9.0 Hz, +9.7 Hz) in ΔB0 were obtained. In humans, motion-impaired R2* maps in 3D CSE-MRI (Reader 1: 1.8 ± 0.6, Reader 2: 1.3 ± 0.7, Reader 3: 1.9 ± 0.6), while 2D CSE-MRI was motion-free (Reader 1: 2.9 ± 0.3, Reader 2: 3.0 ± 0, Reader 3: 3.0 ± 0). A mean difference of 0.66 s-1 and coefficient of repeatability of 9.48 s-1 for placental R2* were observed in the repeated 2D CSE-MRI.Data Conclusion2D-sequential CSE-MRI provides accurate R2* and B0 measurements in ferumoxytol-enhanced placental MRI of animals in the presence of respiratory motion, and motion-robustness in human placental imaging.Level Of Evidence1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:580-592.© 2019 International Society for Magnetic Resonance in Medicine.

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