Functional imaging of the nonhuman primate Placenta with endogenous blood oxygen level–dependent contrast

Purpose To characterize spatial patterns of in the placenta of the rhesus macaque ( Macaca mulatta ), to correlate these patterns with placental perfusion determined using dynamic contrast‐enhanced MRI (DCE‐MRI), and to evaluate the potential for using the blood oxygen level–dependent effect to quantify placental perfusion without the use of exogenous contrast reagent. Methods MRI was performed on three pregnant rhesus macaques at gestational day 110. Multiecho spoiled gradient echo measurements were used to compute maps of . Spatial maxima in these maps were compared with foci of early enhancement determined by DCE‐MRI. Results Local maxima in maps were strongly correlated with spiral arteries identified by DCE‐MRI, with mean spatial separations ranging from 2.34 to 6.11 mm in the three animals studied. Spatial patterns of ( = 1/ ) within individual placental lobules can be quantitatively analyzed using a simple model to estimate fetal arterial oxyhemoglobin concentration and a parameter , reflecting oxygen transport to the fetus. Estimated mean values of ranged from 4.25 mM to 4.46 mM, whereas ranged from 2.80 × 10 5 cm −3 to 1.61 × 10 6 cm −3 . Conclusions Maternal spiral arteries show strong spatial correlation with foci of extended observed in the primate placenta. A simple model of oxygen transport accurately describes the spatial dependence of within placental lobules and enables assessment of placental function and oxygenation without requiring administration of an exogenous contrast reagent. Magn Reson Med 76:1551–1562, 2016.