Photoacoustic imaging could be a viable tool for detecting preeclampsia before it becomes a life-threatening condition for mother and baby, according to a Tulane University study. Preeclampsia — maternal hypertension and proteinuria — is caused by placental ischemia resulting from reduced uteroplacental perfusion. Spectral photoacoustic imaging distinguishes between oxygenated and deoxygenated perfused tissues by estimating the wavelength-dependent absorption of the tissue. Researchers from the Tulane School of Medicine and the Tulane School of Public Health and Tropical Medicine used spectral photoacoustic imaging to monitor longitudinal changes in placental oxygenation levels in an in vivo animal model of preeclampsia. Using a linear least-squares spectral unmixing algorithm, they fit the intensity of the resulting photoacoustic signal to characterize the absorption of oxyhemoglobin and deoxyhemoglobin. From this information, they calculated the relative oxygen saturation in the imaged area and determined that the placenta in the reduced uterine perfusion pressure (RUPP) rat model was hypoxic, and that this hypoxia was maintained through late gestation. Dylan Lawrence, left, a graduate student in biomedical engineering, is part of assistant professor Carolyn Bayer’s research team. Courtesy of Sally Asher. The researchers believe this procedure could be used to detect placental ischemia prior to the onset of symptoms such as high blood pressure, headache, and dizziness. “Spectral photoacoustic imaging is a powerful preclinical tool that has many promising applications in the understanding and treatment of pregnancy-related diseases,” professor Carolyn Bayer said. “It provides new imaging techniques to look at the progression of the disease through gestation, which might be a better way to understand which patients need interventions to treat the preeclampsia.” Because it is a noninvasive procedure, photoacoustic imaging poses little to no risk to the fetus, compared to cordocentesis, a fetal blood sampling procedure. In the future, the researchers plan to use spectral photoacoustic imaging to investigate the effect of therapeutic intervention on placental oxygen levels in vivo. Preeclampsia is a hypertensive disorder that accounts for 14 percent of global maternal deaths annually and affects 5 to 8 percent of all pregnancies. The research was published in Scientific Reports (https://doi.org/10.1038/s41598-018-37310-2).