Evaluation of a motion‐robust 2D chemical shift‐encoded technique for R2* and field map quantification in ferumoxytol‐enhanced MRI of the placenta in pregnant rhesus macaques

BACKGROUND: 3D chemical shift-encoded (CSE)-MRI techniques enable assessment of ferumoxytol concentration but are unreliable in the presence of motion. PURPOSE: To evaluate a motion-robust 2D-sequential CSE-MRI for R2* and B0 mapping in ferumoxytol-enhanced MRI of the placenta. STUDY TYPE: Prospective. ANIMAL MODEL: Pregnant rhesus macaques. FIELD STRENGTH/SEQUENCE: 3.0T/CSE-MRI. ASSESSMENT: 2D-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 mug/mL-440 mug/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 TESTS: Placental R2* and boundary B0 field measurements (DeltaB0) were compared between 2D-sequential and 3D respiratory-gated CSE-MRI using linear regression and Bland-Altman analysis. RESULTS: In phantoms, a slope of 0.94 (r(2) = 0.99, concordance correlation coefficient rho = 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 (r(2) = 1.00, rho = 0.99) and bias of 11.4 Hz (LOA -12.0 Hz, +34.8 Hz) in DeltaB0 were obtained in 2D CSE-MRI compared with 3D CSE-MRI for reference R2*