Abstract P226: The Analysis Of Regional Placental Hemodynamics Using Combined Photoacoustic Imaging And Contrast-enhanced Ultrasound

Abstract

Placental insufficiency is often associated with pregnancies at risk for fetal growth restriction or preeclampsia. We have previously demonstrated that three-dimensional ultrasound-guided photoacoustic imaging (PAI) is a sensitive tool for assessing regional variations in placental oxygenation in mice. However, whether changes in placental oxygenation determined by the PAI correlate with changes in placental perfusion is unknown and was tested in this study. PAI combines optical contrast of photoacoustic laser technology with a high spatial resolution of ultrasound. Placental vascular oxygen saturation (sO2) was quantified in C57Bl/6 mice by the PAI using Vevo 2100 LAZR instrument (Fujifilm, VisualSonics). 50 microliters of Vevo MicroMarker contrast agent was delivered via a bolus tail-vein injection. Placental perfusion parameters were determined at day 15 of gestation in C57Bl/6 mice. Our data demonstrated significantly greater oxygenation in the placental labyrinth versus maternal triangle area (53.01±1.7 vs. 42.7±4.2 % sO2; n=6, p<0.05). No regional differences were detected in relative blood flow in these mice (dB or a.u.). However “time-to-peak” (perfusion kinetics parameter) was greater in the labyrinth compared with maternal triangle area (2.3 times, p<0.05, n=5). Our data show that the overall blood flow is similar throughout the placenta at mid-late gestation, while the perfusion is greater in the labyrinth (fetal) side of the placenta consistent with greater vascularization of this area. Our data suggest that placental sO2 measured by the PAI is associated with coordinated changes in placental perfusion during late stages of mouse pregnancy. This approach provides a novel tool for non-invasively investigating placental environment and pregnancy outcomes particularly in pregnancies complicated by IUGR or preeclampsia.