Abstract P300: Fetal Status Evaluation Using Photoacoustics and 3D Power Doppler Ultrasound

Abstract

Pregnancy complications can seriously impact fetal well-being. However the tools used for the evaluation of fetal oxygenation in clinic are limited to the monitoring of fetal heart rate or invasive techniques (fetal scalp pH and PO 2 ). Therefore, the development of methods enabling accurate, non-invasive and in real-time assessment of fetal status throughout pregnancy is warranted. In this study we tested the combination of photoacoustic imaging (PAI) and 3D power Doppler for the assessment of fetal distress. PAI combines optical contrast of photoacoustic laser technology with high spatial resolution of ultrasound. Power Doppler is a sensitive technique for the detection of blood flow. We hypothesize that a combination of PAI with 3D power Doppler can non-invasively and in real time establish fetal oxygenation, volume, and tissue vascularity. Pregnant C57Bl/6 mice were infused with nitric oxide synthase inhibitor, L-NAME via osmotic minipumps (50 mg/kg/day; days 11 to 14 of gestation) to induce the hypertensive phenotype. At day 14 of gestation, systolic blood pressures were higher in L-NAME-treated vs. untreated C57Bl/6 mice although these values did not reach hypertensive levels (90.8±3.1 vs. 104.4±3.7 mmHg, p<0.05, n=4-5). Fetal weights were lower in the L-NAME-infused mice versus controls (0.12±0.01 vs. 0.17±0.01 g fetal weight per cm tibia length, p<0.05, n=5-6). Fetal liver sO2 was lower in L-NAME-infused mice (47.5±2.1 vs. 56.1±1.6 %, n=4, p<0.05), while no differences were found in fetal brain sO2. Total fetal volume was lower in L-NAME-treated mice (213.8±26.5 vs. 399±45.1 %, n=5, p<0.05) and positively correlated with fetal body weights obtained postmortem in study groups. Fetal tissue vascularity was also lower in L-NAME-infused mice possibly due to limited vascular branching or blood flow (40.8±1.5 vs. 47.7±1.8%, p<0.05). These changes were associated with a compensatory increase in fetal heart rate in L-NAME-treated mice (170.7±9.1 vs. 135.8±5.7 %, p<0.05). We conclude that a combination of PAI with 3D power Doppler provides valuable information about fetal oxygenation and growth in association with tissue vascularity thus permitting non-invasive, in real-time analysis of fetal well-being.