Advanced MR imaging of the placenta: Exploring the in utero placenta-brain connection

Effect of Mediterranean diet or mindfulness-based stress reduction during pregnancy on placental volume and perfusion: A subanalysis of the IMPACT BCN randomized clinical trial

INTRODUCTION

The IMPACT BCN trial-a parallel-group randomized clinical trial where 1221 pregnant women at high risk for small-for-gestational age (SGA) newborns were randomly allocated at 19- to 23-week gestation into three groups: Mediterranean diet, Mindfulness-based Stress reduction or non-intervention-has demonstrated a positive effect of Mediterranean diet and Stress reduction in the prevention of SGA. However, the mechanism of action of these interventions remains still unclear. The aim of this study is to investigate the effect of Mediterranean diet and Stress reduction on placental volume and perfusion.

MATERIAL AND METHODS

Participants in the Mediterranean diet group received monthly individual and group educational sessions, and free provision of extra-virgin olive oil and walnuts. Women in the Stress reduction group underwent an 8-week Stress reduction program adapted for pregnancy, consisting of weekly 2.5-h and one full-day sessions. Non-intervention group was based on usual care. Placental volume and perfusion were assessed in a subgroup of randomly selected women (n = 165) using magnetic resonance (MR) at 36-week gestation. Small placental volume was defined as MR estimated volume <10th centile. Perfusion was assessed by intravoxel incoherent motion.

RESULTS

While mean MR placental volume was similar among the study groups, both interventions were associated with a lower prevalence of small placental volume (3.9% Mediterranean diet and 5% stress reduction vs. 17% non-intervention; p = 0.03 and p = 0.04, respectively). Logistic regression showed that small placental volume was significantly associated with higher risk of SGA in both study groups (OR 7.48 [1.99-28.09] in Mediterranean diet and 20.44 [5.13-81.4] in Stress reduction). Mediation analysis showed that the effect of Mediterranean diet on SGA can be decomposed by a direct effect and an indirect effect (56.6%) mediated by a small placental volume. Similarly, the effect of Stress reduction on SGA is partially mediated (45.3%) by a small placental volume. Results on placental intravoxel incoherent motion perfusion fraction and diffusion coefficient were similar among the study groups.

CONCLUSIONS

Structured interventions during pregnancy based on Mediterranean diet or Stress reduction are associated with a lower proportion of small placentas, which is consistent with the previously observed beneficial effects of these interventions on fetal growth.

Placental volume in pregnant women with opioid use: prenatal MRI assessment

OBJECTIVE

Opioid use in pregnant women is a growing public health concern and is shown to be associated with lower infant birth weights. Placental volume changes in prior studies correlated with various maternal and fetal conditions. We aimed to identify differences between placental volumes in pregnant women with opioid use, and control pregnant women without drug use.

METHODS

We prospectively recruited 27 healthy pregnant women and 17 pregnant women with opioid use disorder who were on medication-assisted treatment (MAT). All women underwent placenta/fetal MRI at 27-39 weeks gestation on a 3 Tesla MR scanner. Placental volumes were measured in a blinded fashion using a previously validated technique. Multiple linear regression was used to identify associations of placental volume with multiple maternal and fetal clinical factors. The significance threshold was set at p < .05.

RESULTS

Placental volume was significantly associated with gestational age at MRI (p < .0001), fetal sex (p = .027), MAT with smoking (p = .0008), MAT with polysubstance use (p = .01), and maternal BMI (p = .032). Placental volume was not associated with opioid MAT alone in our cohort.

CONCLUSION

For pregnant women on medication-assisted treatment for opioid use disorder, there was no significant difference in placental volume compared to healthy pregnant women. However, concomitant smoking and polysubstance use in the setting of medication-assisted treatment may be detrimental to placental health. To our knowledge, this is the first study assessing placental volume in opioid use on prenatal MRI. These results support the benefit of medication-assisted treatment during pregnancy; however additional studies are needed to further elucidate the impact of opioid use on placental and fetal development and postnatal outcomes.

Influence of maternal psychological distress during COVID-19 pandemic on placental morphometry and texture

The Coronavirus Disease 2019 (COVID-19) pandemic has been accompanied by increased prenatal maternal distress (PMD). PMD is associated with adverse pregnancy outcomes which may be mediated by the placenta. However, the potential impact of the pandemic on in vivo placental development remains unknown. To examine the impact of the pandemic and PMD on in vivo structural placental development using advanced magnetic resonance imaging (MRI), acquired anatomic images of the placenta from 63 pregnant women without known COVID-19 exposure during the pandemic and 165 pre-pandemic controls. Measures of placental morphometry and texture were extracted. PMD was determined from validated questionnaires. Generalized estimating equations were utilized to compare differences in PMD placental features between COVID-era and pre-pandemic cohorts. Maternal stress and depression scores were significantly higher in the pandemic cohort. Placental volume, thickness, gray level kurtosis, skewness and run length non-uniformity were increased in the pandemic cohort, while placental elongation, mean gray level and long run emphasis were decreased. PMD was a mediator of the association between pandemic status and placental features. Altered in vivo placental structure during the pandemic suggests an underappreciated link between disturbances in maternal environment and perturbed placental development. The long-term impact on offspring is currently under investigation.

Sexual reproductive health service utilization and associated factors among undergraduate students of Addis Ababa University in Ethiopia

BACKGROUND

Making clinical services attractive to the younger generation has remained a challenge. Students in higher education continue to underutilize sexual and reproductive health services. This group is exposed to a very hostile environment and has a highly mobile and unprotected lifestyle, often resulting in an early sexual debut, physical and drug abuse, and sexually transmitted infections.

OBJECTIVE

The aim of this study was to assess sexual reproductive health services and associated factors among undergraduate students of Addis Ababa University 2022.

METHOD

An Institution-based cross-sectional study was been conducted among 419 randomly selected students and data were collected by using semi-structured and pre-tested questionnaire. Data were entered to Epi info data 7.0 and exported to SPSS version 21.0 for further analysis. Both binary and multiple logistic regression analysis was used to identify factors at P < 0.05 with 95% CI and AOR.

RESULTS

When queried, all 419 youths agreed to participate in the study, for a response rate of 100%. The mean age of the respondents was 22 years. The majority of respondents (371, 88.5%) were between the ages of 19 and 24, and 221 (52.7%) were female. More than half of those polled (273, or 65.2%) were third-year students, while 59, or 14.1%, were first-year students. About 206 (49.2%) of participants lived with their father and mother, but 138 (32.9%) had never discussed sexual and reproductive health. Finally, 205 respondents (or 48.9%) had ever used the Sexual and Reproductive Health Services. College of business (AOR (95% CI) 3.546 (1.62-7.79), respondents who live with only their mother (AOR (95% CI) 9.37 (2.78-31.51) and who live alone (AOR (95% CI) 5.75 (2.40-13.79), positive attitude toward SRHS (AOR (95% CI) 3.15 (1.71-5.80), good knowledge (AOR (95% CI) 4.16 (2.27-7.64), frequency of discussing SRHS(AOR (95% CI) 1.93 (1.12-3.346), Convenient location of youth RHs (AOR (95% CI) 8.31 (1.61-42.93), Fee of RH services (AOR (95% CI) 12.34 (6.48-23.49) and Satisfied to received RH services (AOR (95% CI) 4.59 (2.54-8.33) were independent predictors of utilized SRHS among undergraduate students.

CONCLUSION AND RECOMMENDATION

The prevalence of utilization of sexual and reproductive health services was determined to be low in this study, with identified factors increasing the likelihood of utilization being attitude, knowledge, satisfaction, discussion, fee for RH services, and location, in that order. On the other hand, poor knowledge and a negative attitude toward SRHS posed risks that contributed to reproductive health issues, so we worked on advocating for services that were available in a nearby location and raising awareness. Therefore, policymakers and health planners would be better off strengthening the urgent need to ensure adequate SRHS, knowledge, and attitude building among undergraduate students in higher education in Ethiopia.

Magnetic resonance imaging of the monkey fetal brain in utero

Non-human primates (NHPs) are the closest living relatives of the human and play a critical role in investigating the effects of maternal viral infection and consumption of medicines, drugs, and alcohol on fetal development. With the advance of contemporary fast MRI techniques with parallel imaging, fetal MRI is becoming a robust tool increasingly used in clinical practice and preclinical studies to examine congenital abnormalities including placental dysfunction, congenital heart disease (CHD), and brain abnormalities non-invasively. Because NHPs are usually scanned under anesthesia, the motion artifact is reduced substantially, allowing multi-parameter MRI techniques to be used intensively to examine the fetal development in a single scanning session or longitudinal studies. In this paper, the MRI techniques for scanning monkey fetal brains in utero in biomedical research are summarized. Also, a fast imaging protocol including T2-weighted imaging, diffusion MRI, resting-state functional MRI (rsfMRI) to examine rhesus monkey fetal brains in utero on a clinical 3T scanner is introduced.

Measuring intrauterine growth in healthy pregnancies using quantitative magnetic resonance imaging

OBJECTIVE

The aim of this study was to determine in utero fetal-placental growth patterns using in vivo three-dimensional (3D) quantitative magnetic resonance imaging (qMRI).

STUDY DESIGN

Healthy women with singleton pregnancies underwent fetal MRI to measure fetal body, placenta, and amniotic space volumes. The fetal-placental ratio (FPR) was derived using 3D fetal body and placental volumes (PV). Descriptive statistics were used to describe the association of each measurement with increasing gestational age (GA) at MRI.

RESULTS

Fifty-eight (58) women underwent fetal MRI between 16 and 38 completed weeks gestation (mean = 28.12 ± 6.33). PV and FPR varied linearly with GA at MRI (r_PV,GA = 0.83, r_FPR,GA = 0.89, p value < 0.001). Fetal volume varied non-linearly with GA (p value < 0.01).

CONCLUSIONS

We describe in-utero growth trajectories of fetal-placental volumes in healthy pregnancies using qMRI. Understanding healthy in utero development can establish normative benchmarks where departures from normal may identify early in utero placental failure prior to the onset of fetal harm.

Project SWAVE 2.0: An overview of the study design for multimodal placental image acquisition and alignment

Development of non-invasive and in utero placenta imaging techniques can potentially identify biomarkers of placental health. Correlative imaging using multiple multiscale modalities is particularly important to advance the understanding of placenta structure, function and their relationship. The objective of the project SWAVE 2.0 was to understand human placental structure and function and thereby identify quantifiable measures of placental health using a multimodal correlative approach. In this paper, we present a multimodal image acquisition protocol designed to acquire and align data from ex vivo placenta specimens derived from both healthy and complicated pregnancies. Qualitative and quantitative validation of the alignment method were performed. The qualitative analysis showed good correlation between findings in the MRI, ultrasound and histopathology images. The proposed protocol would enable future studies on comprehensive analysis of placental anatomy, function and their relationship.

● An overview of a novel multimodal placental image acquisition protocol is presented.

● A co-registration method using surface markers and external fiducials is described.

● A preliminary correlative imaging analysis for a placenta specimen is presented.

Ex-Vivo MRI of the Normal Human Placenta: Structural-Functional Interplay and the Association With Birth Weight

BACKGROUND

Advanced magnetic resonance imaging (MRI) methods are increasingly being used to assess the human placenta. Yet, the structure-function interplay in normal placentas and their associations with pregnancy risks are not fully understood.

PURPOSE

To characterize the normal human placental structure (volume and umbilical cord centricity index (CI)) and function (perfusion) ex-vivo using MRI, to assess their association with birth weight (BW), and identify imaging-markers for placentas at risk for dysfunction.

STUDY TYPE

Prospective.

POPULATION

Twenty normal term ex-vivo placentas.

FIELD STRENGTH/SEQUENCE

3 T/ T₁ and T₂ weighted (T₁ W, T₂ W) turbo spin-echo, three-dimensional susceptibility-weighted image, and time-resolved angiography with interleaved stochastic trajectories (TWIST), during passage of a contrast agent using MRI compatible perfusion system that mimics placental flow.

ASSESSMENT

Placental volume and CI were manually extracted from the T₁ W images by a fetal-placental MRI scientist (D.L., 7 years of experience). Perfusion maps including bolus arrival-time and full-width at half maximum were calculated from the TWIST data. Mean values, entropy, and asymmetries were calculated from each perfusion map, relating to both the whole placenta and volumes of interest (VOIs) within the umbilical cord and its daughter blood vessels.

STATISTICAL TESTS

Pearson correlations with correction for multiple comparisons using false discovery rate were performed between structural and functional parameters, and with BW, with P < 0.05 considered significant.

RESULTS

All placentas were successfully perfused and scanned. Significant correlations were found between whole placenta and VOIs perfusion parameters (mean R = 0.76 ± 0.06, range = 0.67-0.89), which were also significantly correlated with CI (mean R = 0.72 ± 0.05, range = 0.65-0.79). BW was correlated with placental volume (R = 0.62), but not with CI (P = 0.40). BW was also correlated with local perfusion asymmetry (R = -0.71).

DATA CONCLUSION

Results demonstrate a gradient of placental function, associated with CI and suggest several ex-vivo imaging-markers that might indicate an increased risk for placental dysfunction.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Neurologic Sequelae Associated with Hypertensive Disorders of Pregnancy

Hypertensive disorders of pregnancy (HDP) contribute to adverse gene-environment interactions prior to conception and continue throughout pregnancy. Embryonic/fetal brain disorders occur from interactions between genetic susceptibilities interacting with acquired diseases or conditions affecting the maternal/placental fetal (MPF) triad. Trimester-specific pathophysiological mechanisms, such as maternal immune activation and ischemic placental syndrome, contribute to adverse peripartum, neonatal and childhood outcomes. Two diagnostic approaches provide timelier diagnoses over the first 1000 days from conception until two years of age. Horizontal analyses assess the maturation of the triad, neonate and child. Vertical analyses consider systems-biology from genetic, molecular, cellular, tissue through organ networks during each developmental niche. Disease expressions associated with HDP have cumulative adverse effects across the lifespan when subjected to subsequent adverse events. Critical/sensitive periods of developmental neuroplasticity over the first 1000 days are more likely to result in permanent sequelae. Novel diagnostic approaches, beginning during pre-conception, will facilitate the development of effective preventive, rescue and reparative neurotherapeutic strategies in response to HDP-related trimester-specific disease pathways. Public health policies require the inclusion of women's health advocacy during and beyond their reproductive years to reduce sequelae experienced by mothers and their offspring. A lower global burden of neurologic disease from HDP will benefit future generations.

Emerging placental biomarkers of health and disease through advanced magnetic resonance imaging (MRI)

Placental dysfunction is a major cause of fetal demise, fetal growth restriction, and preterm birth, as well as significant maternal morbidity and mortality. Infant survivors of placental dysfunction are at elevatedrisk for lifelong neuropsychiatric morbidity. However, despite the significant consequences of placental disease, there are no clinical tools to directly and non-invasively assess and measure placental function in pregnancy. In this work, we will review advanced MRI techniques applied to the study of the in vivo human placenta in order to better detail placental structure, architecture, and function. We will discuss the potential of these measures to serve as optimal biomarkers of placental dysfunction and review the evidence of these tools in the discrimination of health and disease in pregnancy. Efforts to advance our understanding of in vivo placental development are necessary if we are to optimize healthy pregnancy outcomes and prevent brain injury in successive generations. Current management of many high-risk pregnancies cannot address placental maldevelopment or injury, given the standard tools available to clinicians. Once accurate biomarkers of placental development and function are constructed, the subsequent steps will be to introduce maternal and fetal therapeutics targeting at optimizing placental function. Applying these biomarkers in future studies will allow for real-time assessments of safety and efficacy of novel interventions aimed at improving maternal-fetal well-being.

Placental contribution to neonatal encephalopathy

Placental assessment, although currently underused, can inform our understanding of the etiology and timing of Neonatal Encephalopathy (NE). We review our current understanding of the links between placental dysfunction and NE and how this information may inform clinical decisions, now and in the future, emphasizing the four major placental lesions associated with NE. In addition, we discuss maternal and fetal factors that are hypothesized to contribute to specific placental pathologies, especially innate or acquired thrombophilias. We outline the importance of assessing placenta across trimesters and after delivery. As this field continues to evolve, currently available placental histopathological examination methods may need to be combined with advanced prenatal molecular and imaging assessments of placenta and be applied in well-designed studies in large representative populations to better define the links between placental dysfunction and NE.

APPLAUSE: Automatic Prediction of PLAcental health via U-net Segmentation and statistical Evaluation

PURPOSE

Artificial-intelligence population-based automated quantification of placental maturation and health from a rapid functional Magnetic Resonance scan. The placenta plays a crucial role for any successful human pregnancy. Deviations from the normal dynamic maturation throughout gestation are closely linked to major pregnancy complications. Antenatal assessment in-vivo using T2* relaxometry has shown great promise to inform management and possible interventions but clinical translation is hampered by time consuming manual segmentation and analysis techniques based on comparison against normative curves over gestation.

METHODS

This study proposes a fully automatic pipeline to predict the biological age and health of the placenta based on a free-breathing rapid (sub-30 second) T2* scan in two steps: Automatic segmentation using a U-Net and a Gaussian process regression model to characterize placental maturation and health. These are trained and evaluated on 108 3T MRI placental data sets, the evaluation included 20 high-risk pregnancies diagnosed with pre-eclampsia and/or fetal growth restriction. An independent cohort imaged at 1.5 T is used to assess the generalization of the training and evaluation pipeline.

RESULTS

Across low- and high-risk groups, automatic segmentation performs worse than inter-rater performance (mean Dice coefficients of 0.58 and 0.68, respectively) but is sufficient for estimating placental mean T2* (0.986 Pearson Correlation Coefficient). The placental health prediction achieves an excellent ability to differentiate cases of placental insufficiency between 27 and 33 weeks. High abnormality scores correlate with low birth weight, premature birth and histopathological findings. Retrospective application on a different cohort imaged at 1.5 T illustrates the ability for direct clinical translation.

CONCLUSION

The presented automatic pipeline facilitates a fast, robust and reliable prediction of placental maturation. It yields human-interpretable and verifiable intermediate results and quantifies uncertainties on the cohort-level and for individual predictions. The proposed machine-learning pipeline runs in close to real-time and, deployed in clinical settings, has the potential to become a cornerstone of diagnosis and intervention of placental insufficiency. APPLAUSE generalizes to an independent cohort imaged at 1.5 T, demonstrating robustness to different operational and clinical environments.

Normative placental structure in pregnancy using quantitative Magnetic Resonance Imaging

INTRODUCTION

To characterize normative morphometric, textural and microstructural placental development by applying advanced and quantitative magnetic resonance imaging (qMRI) techniques to the in-vivo placenta.

METHODS

We enrolled 195 women with uncomplicated, healthy singleton pregnancies in a prospective observational study. Women underwent MRI between 16- and 40-weeks' gestation. Morphometric and textural metrics of placental growth were calculated from T2-weighted (T2W) images, while measures of microstructural development were calculated from diffusion-weighted images (DWI). Normative tables and reference curves were constructed for each measured index across gestation and according to fetal sex.

RESULTS

Data from 269 MRI studies from 169 pregnant women were included in the analyses. During the study period, placentas undergo significant increases in morphometric measures of volume, thickness, and elongation. Placental texture reveals increasing variability with advancing gestation as measured by grey level non uniformity, run length non uniformity and long run high grey level emphasis. Placental microstructure did not vary with gestational age. Placental elongation was the only metric that differed significantly between male and female fetuses.

DISCUSSION

We report quantitative metrics of placental morphometry, texture and microstructure in a large cohort of healthy controls during the second and third trimesters of pregnancy. These measures can serve as normative references of in-vivo placental development to better understand placental function in high-risk conditions and allow for the early detection of placental mal-development.

Magnetic resonance imaging of placentome development in the pregnant Ewe

INTRODUCTION

Novel imaging measurements of placental development are difficult to validate due to the invasive nature of gold-standard procedures. Animal studies have been important in validation of magnetic resonance imaging (MRI) measurements in invasive preclinical studies, as they allow for controlled experiments and analysis of multiple time-points during pregnancy. This study characterises the longitudinal diffusion and perfusion properties of sheep placentomes using MRI, measurements that are required for future validation studies.

METHODS

Pregnant ewes were anaesthetised for a MRI session on a 3T scanner. Placental MRI was used to classify placentomes morphologically into three types based on their shape and size at two gestational ages. To validate classification accuracy, placentome type derived from MRI data were compared with placentome categorisation results after delivery. Diffusion-Weighted MRI and T2-relaxometry were used to measure a broad range of biophysical properties of the placentomes.

RESULTS

MRI morphological classification results showed consistent gestational age changes in placentome shape, as supported by post-delivery gold standard data. The mean apparent diffusion coefficient was significantly higher at 110 days gestation than at late gestation (~140 days; term, 150 days). Mean T2 was higher at mid gestation (152.2 ± 58.1 ms) compared to late gestation (127.8 ms ± 52.0). Significantly higher perfusion fraction was measured in late gestation placentomes that also had a significantly higher fractional anisotropy when compared to the earlier gestational age.

DISCUSSION

We report baseline measurements of techniques common in placental MRI for the sheep placenta. These measurements are essential to support future validation measurements of placental MRI techniques.

Youth friendly sexual and reproductive health service utilization among high and preparatory school students in Debre Tabor town, Northwest Ethiopia: A cross sectional study

BACKGROUND

Youth continue to fall victim to sexual and reproductive health problems. Despite, reproductive health needs of youth had been supported by different organizations, utilization of those services is low. All efforts have not been felt across the Ethiopian learning institutions as is evidenced by persistent reproductive health problems. Therefore, this study aimed to assess the magnitude of youth friendly sexual and reproductive health service utilization and associated factors among high and preparatory school youths in Debre Tabor town, Northwest Ethiopia.

METHODS

An institution based cross- sectional study was conducted from March 1 to 28, 2016. The data were collected using a pre-tested and structured self-administered questionnaire. Multistage cluster sampling method was used to select the study participants. The data were entered into Epi-data version 4.2.0.0 and analyzed using SPSS version 20. Binary logistics regression was used for analysis. Odds ratio along with 95%CI was estimated to measure the strength of the association. Level of statistical significance was declared at p value ≤0.05.

RESULTS

Overall utilization of reproductive health service was 28.8%. Being male (AOR = 1.54, 95% CI: 1.05, 2.25), prior discussion on reproductive health issues (AOR = 6.33, 95% CI: 4.22, 9.51), and previous sexual intercourse within the past one year (AOR = 1.95, 95% CI: 1.10, 3.44) were significantly associated with youth friendly health service utilization.

CONCLUSIONS

Youth friendly health service utilization among high school and preparatory students in Debre Tabor town was low. Ensuring gender empowerment and advocating sexual and reproductive service discussion among themselves and with others might be important in improving reproductive health utilization and health. Future researcher should address segment of population who does not enter school.

Probing the ballistic microcirculation in placenta using flow-compensated and non-compensated intravoxel incoherent motion imaging

PURPOSE

Intravoxel incoherent motion (IVIM) imaging is widely used to evaluate microcirculatory flow, which consists of diffusive and ballistic flow components. We proposed a joint use of flow-compensated (FC) and non-compensated (NC) diffusion gradients to probe the fraction and velocity of ballistic flow in the placenta.

METHODS

Forty pregnant women were included in this study and scanned on a 1.5T clinical scanner. FC and NC diffusion MRI (dMRI) sequences were achieved using a pair of identical or mirrored bipolar gradients. A joint FC-NC model was established to estimate the fraction (f_b ) and velocity (v_b ) of the ballistic flow. Conventional IVIM parameters (f, D, and D*) were obtained from the FC and NC data, separately. The v_b and f·D*, as placental flow velocity measurements, were correlated with the umbilical-artery Doppler ultrasound indices and gestational ages.

RESULTS

The ballistic flow component can be observed from the difference between the FC and NC dMRI signal decay curves. v_b fitted from the FC-NC model showed strong correlations with umbilical-artery impedance indices, the systolic-to-diastolic (SD) ratio and pulsatility index (PI), with correlation coefficients of 0.65 and 0.62. The f·D* estimated from the NC data positively correlated with SD and PI, while the FC-based f·D* values showed weak negative correlations. Significant gestational-age dependence was also found in the flow velocity measurements.

CONCLUSION

Our results demonstrated the feasibility of using FC and NC dMRI to noninvasively measure ballistic flow velocity in the placenta, which may be used as a new marker to evaluate placenta microcirculation.

Improved fetal blood oxygenation and placental estimated measurements of diffusion-weighted MRI using data-driven Bayesian modeling

PURPOSE

Motion correction in placental DW-MRI is challenging due to maternal breathing motion, maternal movements, and rapid intensity changes. Parameter estimates are usually obtained using least-squares methods for voxel-wise fitting; however, they typically give noisy estimates due to low signal-to-noise ratio. We introduce a model-driven registration (MDR) technique which incorporates a placenta-specific signal model into the registration process, and we present a Bayesian approach for Diffusion-rElaxation Combined Imaging for Detailed placental Evaluation model to obtain individual and population trends in estimated parameters.

METHODS

MDR exploits the fact that a placenta signal model is available and thus we incorporate it into the registration to generate a series of target images. The proposed registration method is compared to a pre-existing method used for DCE-MRI data making use of principal components analysis. The Bayesian shrinkage prior (BSP) method has no user-defined parameters and therefore measures of parameter variation in a region of interest are determined by the data alone. The MDR method and the Bayesian approach were evaluated on 10 control 4D DW-MRI singleton placental data.

RESULTS

MDR method improves the alignment of placenta data compared to the pre-existing method. It also shows a further reduction of the residual error between the data and the fit. BSP approach showed higher precision leading to more clearly apparent spatial features in the parameter maps. Placental fetal oxygen saturation (FO₂ ) showed a negative linear correlation with gestational age.

CONCLUSIONS

The proposed pipeline provides a robust framework for registering DW-MRI data and analyzing longitudinal changes of placental function.

Apparent Diffusion Coefficient of the Placenta and Fetal Organs in Intrauterine Growth Restriction

PURPOSE

This study aimed to assess apparent diffusion coefficient (ADC) of the placenta and fetal organs in intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

A prospective study of 30 consecutive pregnant women (aged 21-38 years with mean age of 31.5 years and a mean gestational week of 35 ± 2.3) with IUGR and 15 age-matched pregnant women was conducted. All patients and controls underwent diffusion-weighted magnetic resonance imaging. The ADCs of the placenta and fetal brain, kidney, and lung were calculated and correlated with neonates needing intensive care unit (ICU) admission.

RESULTS

There was a significant difference in ADC of the placenta and fetal brain, lung, and kidney (P = 0.001, 0.001, 0.04, and 0.04, respectively) between the patients and the controls. The cutoff ADCs of the placenta and fetal brain, lung, and kidney used to detect IUGR were 1.45, 1.15, 1.80, and 1.40 × 10 mm/s, respectively, with areas under the curve (AUCs) of 0.865, 0.858, 0.812, and 0.650, respectively, and accuracy values of 75%, 72.5%, 72.5%, and 70%, respectively. Combined ADC of the placenta and fetal organs used to detect IUGR revealed an AUC of 1.00 and an accuracy of 100%. There was a significant difference in ADC of the placenta and fetal brain, lung, and kidney between neonates needing admission and those not needing ICU admission (P = 0.001, 0.001, 0.002, and 0.002, respectively). The cutoff ADCs of the placenta and fetal brain, lung, and kidney used to define neonates needing ICU were 1.35, 1.25, 1.95, and 1.15 × 10 mm/s with AUCs of 0.955, 0.880, 0.884, and 0.793, respectively, and accuracy values of 86.7%, 46.7%, 76.7%, and 70%, respectively. Combined placental and fetal brain ADC used to define neonates needing ICU revealed an AUC of 0.968 and an accuracy of 93.3%.

CONCLUSION

Combined ADC of the placenta and fetal organs can detect IUGR, and combined ADC of the placenta and fetal brain can define fetuses needing ICU.

MRI evaluation of the placenta from normal variants to abnormalities of implantation and malignancies

Even though the placenta has been known for millennia, it is still considered one of the most complex and least understood human organs. Imaging of the placenta is gaining attention due to its impact on fetal and maternal outcomes. MRI plays a vital role in evaluation of inconclusive cases by ultrasonography. It enables precise mapping of placental abnormalities for proper multidisciplinary planning and management. In this article we provide a comprehensive in-depth review of the role of antenatal MR in evaluating "The Placenta." We will describe the protocols and techniques used for MRI of the placenta, review anatomy of the placenta, describe MRI features of major placental abnormalities including those related to position, depth of implantation, hemorrhage, gestational trophoblastic neoplasia, and retained products of conception and discuss the added value of MRI in the management and preoperative planning of such abnormalities. Level of Evidence: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:1702-1717.

Exploring early human brain development with structural and physiological neuroimaging

Early brain development, from the embryonic period to infancy, is characterized by rapid structural and functional changes. These changes can be studied using structural and physiological neuroimaging methods. In order to optimally acquire and accurately interpret this data, concepts from adult neuroimaging cannot be directly transferred. Instead, one must have a basic understanding of fetal and neonatal structural and physiological brain development, and the important modulators of this process. Here, we first review the major developmental milestones of transient cerebral structures and structural connectivity (axonal connectivity) followed by a summary of the contributions from ex vivo and in vivo MRI. Next, we discuss the basic biology of neuronal circuitry development (synaptic connectivity, i.e. ensemble of direct chemical and electrical connections between neurons), physiology of neurovascular coupling, baseline metabolic needs of the fetus and the infant, and functional connectivity (defined as statistical dependence of low-frequency spontaneous fluctuations seen with functional magnetic resonance imaging (fMRI)). The complementary roles of magnetic resonance imaging (MRI), electroencephalography (EEG), magnetoencephalography (MEG), and near-infrared spectroscopy (NIRS) are discussed. We include a section on modulators of brain development where we focus on the placenta and emerging placental MRI approaches. In each section we discuss key technical limitations of the imaging modalities and some of the limitations arising due to the biology of the system. Although neuroimaging approaches have contributed significantly to our understanding of early brain development, there is much yet to be done and a dire need for technical innovations and scientific discoveries to realize the future potential of early fetal and infant interventions to avert long term disease.

Multi-modal functional MRI to explore placental function over gestation

PURPOSE

To investigate, visualize and quantify the physiology of the human placenta in several dimensions - functional, temporal over gestation, and spatial over the whole organ.

METHODS

Bespoke MRI techniques, combining a rich diffusion protocol, anatomical data and T2* mapping together with a multi-modal pipeline including motion correction and extracted quantitative features were developed and employed on pregnant women between 22 and 38 weeks gestational age including two pregnancies diagnosed with pre-eclampsia.

RESULTS

A multi-faceted assessment was demonstrated showing trends of increasing lacunarity, and decreasing T2* and diffusivity over gestation.

CONCLUSIONS

The obtained multi-modal acquisition and quantification shows promising opportunities for studying evolution, adaptation and compensation processes.

Fetal neurology: Principles and practice with a life-course perspective

Clinical service, educational, and research components of a fetal/neonatal neurology program are anchored by the disciplines of developmental origins of health and disease and life-course science as programmatic principles. Prenatal participation provides perspectives on maternal, fetal, and placental contributions to health or disease for fetal and subsequent neonatal neurology consultations. This program also provides an early-life diagnostic perspective for neurologic specialties concerned with brain health and disease throughout childhood and adulthood. Animal models and birth cohort studies have demonstrated how the science of epigenetics helps to understand gene-environment interactions to better predict brain health or disease. Fetal neurology consultations provide important diagnostic contributions during critical or sensitive periods of brain development when future neurotherapeutic interventions will maximize adaptive neuroplasticity. Age-specific normative neuroinformatics databases that employ computer-based strategies to integrate clinical/demographic, neuroimaging, neurophysiologic, and genetic datasets will more accurately identify either symptomatic patients or those at risk for brain disorders who would benefit from preventive, rescue, or reparative treatment choices throughout the life span.

What is the most suitable MR signal index for quantitative evaluation of placental function using Half-Fourier acquisition single-shot turbo spin-echo compared with T2-relaxation time?

Background Half-Fourier acquisition single-shot turbo spin-echo (HASTE) imaging is now widely used for placental and fetal imaging because of its rapidity and low sensitivity to fetal movement. If placental dysfunction is also predicted by quantitative value obtained from HASTE image, then it might be beneficial for evaluating placental wellbeing. Purpose To ascertain the most suitable magnetic resonance (MR) signal indexes reflecting placental function using HASTE imaging. Material and Methods This retrospective study included 37 consequent patients who had given informed consent to MR imaging (MRI) examinations. All had undergone MRI examinations between February 2014 and June 2015. First, the correlation between T2-relaxation time of normal placenta and gestational age (GA) was examined. Second, correlation between signal intensity ratios (SIRs) using HASTE imaging and placental T2-relaxation time were assessed. The SIRs were calculated using placental signal intensity (SI) relative to the SI of the amniotic fluid, fetal ocular globes, gastric fluid, bladder, maternal psoas major muscles, and abdominal subcutaneous adipose tissue. Results Among the 37 patients, the correlation between T2-relaxation time of the 25 normal placentas and GA showed a moderately strong correlation (Spearman rho = -0.447, P = 0.0250). The most significant correlation with placental T2-relaxation time was observed with the placental SIR relative to the maternal psoas major muscles (SIR_{pl./psoas muscle}) (Spearman rho = -0.531, P = 0.0007). Conclusion This study revealed that SIR_{pl./psoas muscle} showed the best correlation to placental T2-relaxation time. Results show that SIR_{pl./psoas muscle} might be optimal as a clinically available quantitative index of placental function.

Apparent Diffusion Coefficient of the Placenta in Twin versus Singleton Pregnancies

Previous studies in singleton pregnancies reported conflicting trends in apparent diffusion coefficient (ADC) values with gestational age (GA) and stable relative ADC (rADC; ADC placenta divided by ADC globe) throughout pregnancy. The purpose of our study was to compare the ADC and rADC of placentas of twin and singleton pregnancies.

MATERIALS AND METHODS

Fetal MRI of 11 twin and 23 singleton pregnancies were retrospectively analyzed. Each group was further divided by GA (≤24 and >24 weeks). On ADC, 3 regions of interest were selected in the placenta and 1 in the globe. ADC and rADC measurements were compared between different GA and between singleton and twin placentas.

RESULTS

No significant difference was shown between ADC and rADC values of singleton and twin placentas as well as between ADC and rADC values of singleton and twin placentas at different GA. No significant difference was shown when accounting for both GA and number of fetuses.

CONCLUSION

The diffusion characteristics of twin placentas are similar to those of singleton placentas. ADC and rADC remain stable throughout pregnancy in twin and singleton placentas, reflecting stable extracellular water diffusion, despite changes associated with placental maturation.

Novel Detection of Placental Insufficiency by Magnetic Resonance Imaging in the Nonhuman Primate

The placenta is a vital organ necessary for healthy fetal development. Placental insufficiency creates an in utero environment where the fetus is at risk of insufficient oxygen or nutrient exchange. This is primarily caused by impairment of either maternal or fetal circulation or vascular thrombosis such as placental infarction. As a result of placental dysfunction, affected fetuses may be growth restricted, neurologically impaired, and at risk of increased morbidity and mortality. In a cohort of 4 pregnant Rhesus macaques, we describe antenatal detection of naturally occurring intrauterine growth restriction (IUGR) and aberrant fetal neurodevelopment in 1 animal. Abnormal growth parameters were detected by Doppler ultrasound, and vascular insufficiency in the intervillous space was characterized by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Furthermore, placental oxygen reserve was shown to be reduced compared to control animals by measurements of placental water T2*. To characterize the effects of IUGR on fetal brain development, T2 and diffusion anisotropy images of the fetal brain were acquired in utero. Reduced brain volume and cerebral cortical surface area were apparent macroscopically. Microstructural abnormalities within the developing white matter and cerebral cortex were also observed through analysis of water diffusion anisotropy. After delivery by cesarean section, pathological examination confirmed placental insufficiency with hypoxia. These findings exemplify how DCE-MRI and T2*-based measurements of blood oxygenation within the placenta can provide noninvasive imaging methods for assessing in vivo placental health to potentially identify pregnancies affected by placental insufficiency and abnormal fetal neurodevelopment prior to the onset of fetal and neonatal distress.

In vivo assessment of the placental anatomy and perfusion in a mouse model of intrauterine inflammation

BACKGROUND

Magnetic resonance imaging (MRI) provides useful markers to examine placental function. MRI features of placental injury due to intrauterine inflammation-a common risk during pregnancy, are not well known.

PURPOSE

To investigate the capability of structural MRI and intravoxel incoherent motion (IVIM) imaging in examining acute placental injury in a mouse model of intrauterine inflammation, as well as gestation-dependent placental changes.

STUDY TYPE

Prospective study.

ANIMAL MODEL

Pregnant CD1 mice were scanned on embryonic day 15 (E15, n = 40 placentas from six dams) and E17. On E17, mice were subjected to intrauterine injury by exposure to lipopolysaccharide (LPS, n = 25 placentas from three dams) or sham injury (n = 25 placentas from three dams).

FIELD STRENGTH/SEQUENCE

In vivo MRI was performed on an 11.7T Bruker scanner, using a fast spin-echo sequence and a diffusion-weighted echo-planar imaging (EPI) sequence.

ASSESSMENT

T₂ -weighted MRI was acquired to evaluate placental volume. IVIM imaging was performed in a restricted field-of-view using 15 b-values from 10-800 s/mm² , based on which, the pseudodiffusion fraction (f), pseudodiffusion coefficient (D*), and tissue water coefficient (D) were estimated with a two-step fitting procedure.

STATISTICAL TESTS

Two-way analysis of variance (ANOVA) was used to evaluate the group differences.

RESULTS

The placental volume increased by ∼21% from E15 to E17 (P < 0.01), and a 15% volume loss was observed at 6 hours after LPS exposure (P < 0.01). IVIM parameters (f, D*, and f·D*) were similar between the E15 and E17 sham groups (P > 0.05), which was significantly reduced in the LPS-exposed placentas compared to the shams (P < 0.001). D values decreased from E15 to E17 (P < 0.05), which were further reduced after LPS exposure (P < 0.05). Changes in placental area and vascular density were histologically identified in the LPS-exposed group, along with gestation-dependent changes.

DATA CONCLUSION

Our results suggested structural MRI and IVIM measurements are potential markers for detecting acute placental injury after intrauterine inflammation.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1260-1267.

Neurodevelopmental Abnormalities and Congenital Heart Disease: Insights Into Altered Brain Maturation

In the past 2 decades, it has become evident that individuals born with congenital heart disease (CHD) are at risk of developing life-long neurological deficits. Multifactorial risk factors contributing to neurodevelopmental abnormalities associated with CHD have been identified; however, the underlying causes remain largely unknown, and efforts to address this issue have only recently begun. There has been a dramatic shift in focus from newly acquired brain injuries associated with corrective and palliative heart surgery to antenatal and preoperative factors governing altered brain maturation in CHD. In this review, we describe key time windows of development during which the immature brain is vulnerable to injury. Special emphasis is placed on the dynamic nature of cellular events and how CHD may adversely impact the cellular units and networks necessary for proper cognitive and motor function. In addition, we describe current gaps in knowledge and offer perspectives about what can be done to improve our understanding of neurological deficits in CHD. Ultimately, a multidisciplinary approach will be essential to prevent or improve adverse neurodevelopmental outcomes in individuals surviving CHD.

Provocative ideas on human placental biology: A prerequisite for prevention and treatment of neonatal health challenges

A 2-day invite-only meeting on generating "Provocative Ideas on human placental research" was organized on 1-2 December 2015 at the Translational Health Science and Technology Institute, Faridabad. This meeting was sponsored by Department of Biotechnology, Ministry of Science and Technology, Govt. of India. The objectives of this meeting were the critical evaluation of placental physiology and its development. Special emphasis was placed on understanding the consequences and implications of placental development in sustenance of pregnancy and in pregnancy-associated complications such as preeclampsia, intrauterine growth restriction, and preterm birth. This meeting brought together experienced as well as novice clinicians and biologists who have a keen interest in the field of placental biology, including development of new technologies and methods for evaluating the role of placenta in predicting pregnancy outcomes. The meeting primarily focused on (i) high-throughput "-omics" approaches, (ii) maternal nutrition and placental function, (iii) placental infection and inflammation, (iv) real-time evaluation of placental development: tools for placental research, and (v) epidemiologic relevance of placental-based research. Unanimous consensus emerged among the participants to carry out additional work focused on these areas. In this article, we summarize the talks and review the published literature on the above-mentioned niches. As a direct outcome of this meeting, a request for applications has been announced by the Department of Biotechnology, Government of India, for pursuing research in this vital but understudied domain.

Robust preprocessing for stimulus-based functional MRI of the moving fetus

Fetal motion manifests as signal degradation and image artifact in the acquired time series of blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) studies. We present a robust preprocessing pipeline to specifically address fetal and placental motion-induced artifacts in stimulus-based fMRI with slowly cycled block design in the living fetus. In the proposed pipeline, motion correction is optimized to the experimental paradigm, and it is performed separately in each phase as well as in each region of interest (ROI), recognizing that each phase and organ experiences different types of motion. To obtain the averaged BOLD signals for each ROI, both misaligned volumes and noisy voxels are automatically detected and excluded, and the missing data are then imputed by statistical estimation based on local polynomial smoothing. Our experimental results demonstrate that the proposed pipeline was effective in mitigating the motion-induced artifacts in stimulus-based fMRI data of the fetal brain and placenta.

Hyperpolarized [1-(13) C]pyruvate MRI for noninvasive examination of placental metabolism and nutrient transport: A feasibility study in pregnant guinea pigs

PURPOSE

To test the feasibility of hyperpolarized [1-(13) C]pyruvate magnetic resonance imaging (MRI) for noninvasive examination of guinea pig fetoplacental metabolism and nutrient transport.

MATERIALS AND METHODS

Seven pregnant guinea pigs with a total of 30 placentae and fetuses were anesthetized and scanned at 3T. T1 -weighted (1) H images were obtained from the maternal abdomen. An 80 mM solution of hyperpolarized [1-(13) C]pyruvate (hereafter referred to as pyruvate) was injected into a vein in the maternal foot. Time-resolved 3D (13) C images were acquired starting 10 seconds after the beginning of bolus injection and every 10 seconds after to 50 seconds. The pregnant guinea pigs were recovered after imaging. Regions of interest (ROIs) were drawn around the maternal heart and each placenta and fetal liver in all slices in the (1) H images. These ROIs were copied to the (13) C images and were used to calculate the sum of the pyruvate and lactate signal intensities for each organ. The signal intensities were normalized by the volume of the organ and the maximum signal in the maternal heart.

RESULTS

No adverse events were observed in the pregnant guinea pigs and natural pupping occurred at term (∼68 days). Pyruvate signal was observed in all 30 placentae, and lactate, a by-product of pyruvate metabolism, was also observed in all placentae. The maximum pyruvate and lactate signals in placentae occurred at 20 seconds. In addition to the observation of pyruvate and lactate signals in the placentae, both pyruvate and lactate signals were observed in all fetal livers. The maximum pyruvate and lactate signals in the fetal livers occurred at 10 seconds and 20 seconds, respectively.

CONCLUSION

This work demonstrates the feasibility of using hyperpolarized [1-(13) C]pyruvate MRI to noninvasively examine fetoplacental metabolism and transport of pyruvate in guinea pigs. Hyperpolarized (13) C MRI may provide a novel method for longitudinal studies of fetoplacental abnormalities.