Purpose: To characterize spatial patterns of T* 2 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 T* 2. Spatial maxima in these maps were compared with foci of early enhancement determined by DCE-MRI. Results: Local maxima in T* 2 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 T* 2 (= 1/ T* 2) within individual placental lobules can be quantitatively analyzed using a simple model to estimate fetal arterial oxyhemoglobin concentration [Hbo, f] and a parameter viPS/ɸ, reflecting oxygen transport to the fetus. Estimated mean values of [Hbo, f] ranged from 4.25 mM to 4.46 mM, whereas viPS/ɸ ranged from 2.80 × 105 cm−3 to 1.61 × 106 cm−3. Conclusions: Maternal spiral arteries show strong spatial correlation with foci of extended T* 2 observed in the primate placenta. A simple model of oxygen transport accurately describes the spatial dependence of R* 2 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.
- BOLD MRI
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging