• Brijesh Kumar Yadav, Sagar Buch, Uday Krishnamurthy, Pavan Jella, Edgar Hernandez-Andrade, Anabela Trifan, Lami Yeo, Sonia S Hassan, Mark HaackeEEDepartment of Radiology, Wayne State University School of Medicine, Detroit, MI, USA.Department of Biomedical Engineering, Wayne State University College of Engineering, Detroit, MI, USA., Roberto Romero, and Jaladhar Neelavalli.
• Department of Radiology, Wayne State University School of Medicine, Detroit, MI, USA.
• Eur Radiol. 2019 Apr 1; 29 (4): 2017-2026.

ObjectivesTo present the feasibility of performing quantitative susceptibility mapping (QSM) in the human fetus to evaluate the oxygenation (SvO2) of cerebral venous blood in vivo.MethodsSusceptibility weighted imaging (SWI) data were acquired from healthy pregnant subjects (n = 21, median = 31.3 weeks, interquartile range = 8.8 weeks). The susceptibility maps were generated from the SWI-phase images using a modified QSM processing pipeline, optimised for fetal applications. The processing pipeline is as follows: (1) mild high-pass filtering followed by quadratic fitting of the phase images to eliminate background phase variations; (2) manual creation of a fetal brain mask that includes the superior sagittal sinus (SSS); (3) inverse filtering of the resultant masked phase images using a truncated k-space approach with geometric constraint. Further, the magnetic susceptibility, ∆χv and corresponding putative SvO2 of the SSS were quantified from the generated susceptibility maps. Systematic error in the measured SvO2 due to the modified pipeline was also studied through simulations.ResultsSimulations showed that the systematic error in SvO2 when using a mask that includes a minimum of 5 voxels around the SSS and five slices remains < 3% for different orientations of the vessel relative to the main magnetic field. The average ∆χv in the SSS quantified across all gestations was 0.42 ± 0.03 ppm. Based on ∆χv, the average putative SvO2 in the SSS across all fetuses was 67% ± 7%, which is in good agreement with published studies.ConclusionsThis in vivo study demonstrates the feasibility of using QSM in the human fetal brain to estimate ∆χv and SvO2.Key Points• A modified quantitative susceptibility mapping (QSM) processing pipeline is tested and presented for the human fetus. • QSM is feasible in the human fetus for measuring magnetic susceptibility and oxygenation of venous blood in vivo. • Blood magnetic susceptibility values from MR susceptometry and QSM agree with each other in the human fetus.

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