New Frontiers in Placenta Tissue Imaging

Abstract

The placenta is a highly vascularised organ with unique structural and metabolic complexities. As the primary conduit of fetal support, the placenta mediates transport of oxygen, nutrients, and waste between maternal and fetal blood. Thus, normal placenta anatomy and physiology is absolutely required for maintenance of maternal and fetal health during pregnancy. Moreover, impaired placental health can negatively impact offspring growth trajectories as well as increase the risk of maternal cardiovascular disease later in life. Despite these crucial roles for the placenta, placental disorders, such as preeclampsia, intrauterine growth restriction, and preterm birth, remain incompletely understood. Effective noninvasive imaging and image analysis are needed to advance the obstetrician’s clinical reasoning toolkit and improve the utility of the placenta in interpreting maternal and fetal health trajectories. Current paradigms in placental imaging and image analysis aim to improve the traditional imaging techniques that may be time-consuming, costly, or invasive. In concert with conventional clinical approaches such as ultrasound, advanced imaging modalities can provide insightful information on the structure of placental tissues. Herein, the authors discuss such imaging modalities; their specific applications in structural, vascular, and metabolic analysis of placental health; and emerging frontiers in image analysis research in both preclinical and clinical contexts.

Impact of ectopic calcification on vascular oxygenation in placental dysfunction models: Simultaneousin vivoassessment with multi-parametric ultrasound and photoacoustic imaging

“…The placenta is a temporary organ that develops during pregnancy and serves a central role in facilitating the transportation and transfer of gas, nutrients, waste, and hormones between the maternal and fetal blood streams 1, 2 . Three critical categories of placental health can be monitored, including anatomical structure, metabolism, and vascular function.…”

“…There are several imaging modalities that are used clinically and preclinically to probe into placenta and fetal development. 2 Optical approaches such as confocal microscopy and optical coherence tomography offer high spatial resolution, however these modalities have poor penetrative depth (on the order of few microns to a few millimeters for confocal microscopy and optical coherence tomography respectively). 2, 8 The common clinical imaging techniques, along with their respective modality variants, such as magnetic resonance imaging, computed tomography, positron emission tomography, and single photon emission computed tomography, have better penetrative depth, but poor spatial resolution, and they can be ionizing or require exogenous contrast agents that can be harmful to a pregnancy.…”

“…2 Optical approaches such as confocal microscopy and optical coherence tomography offer high spatial resolution, however these modalities have poor penetrative depth (on the order of few microns to a few millimeters for confocal microscopy and optical coherence tomography respectively). 2, 8 The common clinical imaging techniques, along with their respective modality variants, such as magnetic resonance imaging, computed tomography, positron emission tomography, and single photon emission computed tomography, have better penetrative depth, but poor spatial resolution, and they can be ionizing or require exogenous contrast agents that can be harmful to a pregnancy. 2, 9 A modality that is non-ionizing, non-invasive, has decent resolution and penetration depth while being low cost and mobile is ultrasound (US) imaging and hence is ubiquitously used in evaluating placental health.…”

“…2, 8 The common clinical imaging techniques, along with their respective modality variants, such as magnetic resonance imaging, computed tomography, positron emission tomography, and single photon emission computed tomography, have better penetrative depth, but poor spatial resolution, and they can be ionizing or require exogenous contrast agents that can be harmful to a pregnancy. 2, 9 A modality that is non-ionizing, non-invasive, has decent resolution and penetration depth while being low cost and mobile is ultrasound (US) imaging and hence is ubiquitously used in evaluating placental health. Indeed, the Grannum grading system utilizes US images during routine pregnancy checkups.…”

“…13 Efforts have been made to use many different imaging modalities to investigate the placenta’s structure and function from the nano to macro scale. 2, 9, 14, 15…”