Spectral photoacoustic imaging to estimate in vivo placental oxygenation during preeclampsia

Abstract

Preeclampsia is a pregnancy-related hypertensive disorder accounting for 14% of global maternal deaths annually. Preeclampsia — maternal hypertension and proteinuria — is promoted by placental ischemia resulting from reduced uteroplacental perfusion. Here, we assess longitudinal changes in placental oxygenation during preeclampsia using spectral photoacoustic imaging. Spectral photoacoustic images were acquired of the placenta of normal pregnant (NP) and preeclamptic reduced uterine perfusion pressure (RUPP) Sprague Dawley rats on gestational days (GD) 14, 16, and 18, corresponding to mid- to late gestation (n = 10 per cohort). Two days after implementation of the RUPP surgical model, placental oxygen saturation decreased 12% in comparison with NP. Proteinuria was determined from a 24-hour urine collection prior to imaging on GD18. Blood pressure measurements were obtained on GD18 after imaging. Placental hypoxia in the RUPP was confirmed with histological staining for hypoxia-inducible factor (HIF)-1α, a cellular transcription regulator which responds to local oxygen levels. Using in vivo, longitudinal imaging methods we determined that the placenta in the reduced uterine perfusion pressure rat model of preeclampsia is hypoxic, and that this hypoxia is maintained through late gestation. Future work will utilize these methods to assess the impact of novel therapeutics on placental ischemia and the progression of preeclampsia.

Non-invasive determination of murine placental and foetal functional parameters with multispectral optoacoustic tomography

“…The change in the blood oxygenation parameters (HbO, HbR and SO 2 ) while changing the oxygen exposure from 100% to 20% also depicts the nature of their alterations, substantiating the standard rule of change in blood-oxygenation parameters. Considering the established correlation between the OA response to blood oxygenation and Doppler flow 34 , our functional responses are in good agreement with the previously reported data, substantiating the efficacy of the ROAT imaging instrumentation for non-invasive studies with an unprecedented spatio-temporal resolution and field of view. We can therefore state that ROAT is a potentially viable imaging paradigm to monitor changes in the functional attributes of foetal and placental regions, which may help to overcome complications during gestation periods.…”

A review of clinical photoacoustic imaging: Current and future trends

“…With breast cancer topping the list with CE marked Imagio™ and MSOT Acuity in markets for diagnosis, several novel clinical applications of PAI can be expected in the coming years with the advent of new custom proprietary PAI systems designed for clinical use. One such transpiring clinical application is in gynecology whereby multispectral PAI has been employed in pre-clinical studies to examine placental, fetal and maternal sO 2 levels in normal and pathologic pregnancies in relation to pregnancy-related diseases [[127], [128], [129], [130]]. Recently, translation to the clinical stage was realized with a transvaginal fast-scanning photoacoustic endoscopy configuration which enabled high-resolution imaging of the microvasculature in the cervix down to capillary-size resolutions [131].…”

Estimating blood oxygenation from photoacoustic images: can a simple linear spectroscopic inversion ever work?

“…[16][17][18][19][20][21][22][23] Despite this, an increasing number of publications are appearing that do not take spectral coloring into account, and yet assume that the estimates of sO 2 that are obtained are trustworthy. It is particularly concerning that articles are appearing in which these questionable estimates of sO 2 are being used to make judgments in preclinical [24][25][26][27][28][29][30][31][32][33][34][35][36] and even clinical studies. [37][38][39][40][41] This trend has been exacerbated by the appearance of commercially available photoacoustic imaging platforms that appear to provide accurate estimates of sO 2 , even though the justification for these claims and experimental validation is weak at best.…”