Fetal cerebral blood oxygenation status could be an important physiological parameter in identifying fetuses at risk of brain injury. Moreover, this allows the understanding of oxygen metabolism in the developing fetal brain in healthy homeostatic conditions. Quantitative susceptibility mapping (QSM) uses both the intra- and extravascular phase to estimate the magnetic susceptibility on a pixel-by-pixel basis. QSM is also independent of the orientation and the shape/size of the structure of interest. Although QSM has been used to measure blood oxygenation non-invasively in the cerebral veins and detect hemorrhages or micro-bleeds, it has not yet been translated to fetal imaging.
PRB researchers studied the feasibility of performing QSM in the human fetus to evaluate the oxygenation of cerebral venous blood in-vivo. Twenty-one healthy women in the second and third trimesters were examined, and susceptibility maps were generated from the susceptibility weighted imaging (SWI)-phase images using a modified QSM processing pipeline, optimized for fetal applications. The processing pipeline performed manual creation of a fetal brain mask that included the superior sagittal sinus. The team discovered that QSM is feasible in the human fetus for measuring magnetic susceptibility and oxygenation of venous blood in-vivo. Moreover, blood magnetic susceptibility values from MR susceptometry and QSM agreed with each other in the human fetus.