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Ultrasound is widely used as the initial diagnostic imaging modality during pregnancy with both high spatial and temporal resolution. Although MRI in pregnancy has long focused on the fetus, its use in placental imaging has greatly increased over recent years. In addition to the possibilities of evaluating function, MRI with a wide field of view and high contrast resolution allows characterization of placental anatomy, particularly in situations that are difficult to specify with ultrasound, especially for suspected placenta accreta. MRI also appears to be a particularly useful examination for the anatomical evaluation of the placenta independent of maternal body habitus or fetal position. Indeed, surprisingly little attention is paid to the placenta in MRI when the indication for the examination is fetal. Thus, some aspects of the placenta seem to us to be important to be recognized by the radiologist and to be described on the MRI report. In this review, we will describe MRI sequences used for, and common features seen in, imaging of i) the normal placenta, ii) abnormal aspects of the placenta that should be identified on MRI performed for fetal reason, and iii) placental anomalies for which placental MRI may be indicated. [ABSTRACT FROM AUTHOR]

It is important to develop a better understanding of placental insufficiency given its role in common maternofetal complications such as preeclampsia and fetal growth restriction. Functional magnetic resonance imaging offers unprecedented techniques for exploring the placenta under both normal and pathological physiological conditions. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) is an established and very robust method to investigate the microcirculatory parameters of an organ and more specifically its perfusion. It is currently a gold standard in the physiological and circulatory evaluation of an organ. Its application to the human placenta could enable to access many microcirculatory parameters relevant to the placental function such as organ blood flow, fractional blood volume, and permeability surface area, by the acquisition of serial images, before, during, and after administration of an intravenous contrast agent. Widely used in animal models with gadolinium-based contrast agents, its application to the human placenta could be possible if the safety of contrast agents in pregnancy is established or they are confirmed to not cross the placenta. [ABSTRACT FROM AUTHOR]

Introduction: Exploration of placental perfusion is essential in screening for dysfunctions impairing fetal growth. The objective of this study was to assess the potential value of contrast-enhanced ultrasonography (CEUS) and magnetic resonance imaging (MRI) for examining placental perfusion in a murine model of intrauterine growth restriction (IUGR). We also studied the reproducibility of perfusion quantification by CEUS.Methods: Pregnant Sprague Dawley rat models of IUGR were studied during the third trimester. Unilateral uterine artery ligation induced IUGR. Placental perfusion was evaluated by CEUS and perfusion MRI with gadolinium for both ligated and control fetoplacental units. The kinetic parameters of the two imaging modalities were then compared.Results: The analysis included 20 rats. The study showed good reproducibility of the CEUS indicators. The CEUS perfusion index approximated the blood flow rate and was halved in the ligation group (27.9 [u.a] (±14.8)) versus 61 [u.a] (±22.3) on the control side (P = 0.0003). MRI with gadolinium injection showed a clear reduction in the blood flow rate to 51.2 mL/min/100 mL (IQR 34.9-54.9) in the ligated horn, compared with 90.9 mL/min/100 mL (IQR 85.1-95.7) for the control side (P < 0.0001). The semiquantitative indicators obtained from the kinetic curves for both CEUS and MRI showed similar trends. Nonetheless, values were more widely dispersed with CEUS than MRI.Discussion: The similar results for the quantification of placental perfusion by MRI and CEUS reinforce the likelihood that CEUS can be used to identify IUGR in a murine model induced by uterine vessel ligation. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To monitor and quantify uteroplacental perfusion in rat pregnancies by Doppler ultrasound (DUS) and contrast-enhanced ultrasound (CEUS). Methods: Fourteen rats were randomized in two groups (the CEUS group and the control group). On days 8, 11, 14, 17, 19 and 20 of gestation, we used DUS to measure the resistance index (RI), pulsatility index and blood velocity in the uterine, arcuate and umbilical arteries in both groups. On days 14, 17 and 20, one group was also examined by CEUS. Quantitative perfusion parameters were calculated in 4 compartments (mesometrial triangle, placenta, umbilical cord and fetus) and compared. Results: The DUS measurement showed that the RI of the uterine and arcuate arteries decreased (p < 0.01) from day 14 to day 17, while velocity increased each of these arteries (p < 0.01 and p < 0.05, respectively). Quantification of uteroplacental perfusion by CEUS in bolus mode revealed that blood volume and local blood flow increased from day 14 to day 20 in the mesometrial triangle (p < 0.01) and the placenta (p < 0.05). In the CEUS destruction-replenishment mode, the perfusion parameters showed trends similar to those observed in bolus mode. No microbubbles were detected in the umbilical vein or fetal compartments. The weights of pups in the two groups did not differ significantly. Conclusions: CEUS estimates of placental perfusion complement the data provided by DUS. [Copyright &y& Elsevier]