Abstract 131: Quantification of in vivo Placental Oxygenation Using Ultrasound-guided Spectral Photoacoustic Imaging

Abstract

Preeclampsia, linked to abnormal placental development and ischemia, is a major cause of fetal and maternal death. Currently, the only cure is high-risk preterm delivery. Although clinical therapies to regulate the symptoms of preeclampsia—mean arterial pressure and proteinuria—it is unknown whether these therapeutics restore placental blood flow and reduce ischemia. We are developing ultrasound-guided spectral photoacoustic imaging to quantify placental ischemia and characterize therapeutic response. Ultrasound imaging is the preferred imaging modality to monitor pregnancy due to its safety, low cost, and mobility. Similar to ultrasound, photoacoustic imaging can provide co-registered images of tissue function. In these studies, pregnant SWV mice were imaged longitudinally from E12.5 to 18.5 using a Vevo LAZR small animal imaging system. Algorithms were developed to correlate the spectral photoacoustic data to a hemoglobin oxygenation (%sO 2 ) calibration standard—a phantom containing blood at varying partial pressures of oxygen. The phantom calibration standard deviation was 7.9% (n=3). The resulting ultrasound images were used to segment the placenta (Figure 1). An overlay of the %sO 2 on the ultrasound image maps placental variation in %sO 2 during longitudinal development. We demonstrate that our imaging method is capable of quantifying %sO2 and monitoring placental function in vivo . Future work will use our preclinical %sO2 quantification methods to characterize placental function during treatment for preeclampsia.