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A novel method for creating "golden" 3D center-out radial MRI sampling trajectories was developed and analyzed. This method, called ELECTRO (ELECTRic potential energy Optimized), uses repulsive forces to minimize electric potential energy. An objective function [Formula: see text], the electric potential energies of all subsets of consecutive readouts in a 3D radial trajectory, and its reduced form were minimized using a multi-stage optimization strategy. A metric called normalized mean nearest neighbor angular distance (NMNA) was proposed for describing distributions of points on a sphere. ELECTRO and other relevant golden trajectories were compared in silico using NMNA and point spread function analysis. Consecutive readouts from an ELECTRO trajectory were well spread out, with consistent NMNA values across sphere sizes (σNMNA = 0.005) and between regions on the sphere (NMNA ≈ 1.49). Conversely, the supergolden trajectory had poor consistency in NMNA values (σNMNA = 0.090) and clustering (NMNA = 1.28 at the pole with 40,000 readouts) that lead to artifact in the point spread function. Multi-stage optimization was faster than single-stage and obtained lower values of [Formula: see text] (e.g., 0.87 vs. 0.91, for a sphere size of 40). In conclusion, ELECTRO trajectories are more golden than other 3D center-out radial trajectories, making them a suitable candidate for dynamic 3D MR imaging.
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Placental function plays a crucial role in fetal development, as it serves as the primary interface for delivery of nutrients and oxygen from the mother to fetus. Magnetic resonance imaging (MRI) has significantly improved our ability to visualize and understand the placenta's complex structure and function. This review provides an up-to-date examination of the most common and novel placental MRI techniques. It will also discuss the clinical applications of MRI in diagnosing and monitoring placental insufficiency, as well as its implications for fetal growth restriction (FGR) and congenital heart disease (CHD). Ongoing research using multi-parametric MRI techniques aims to develop novel biomarkers and uncover the relationships between placental parameters and pre-onset diseased states, ultimately contributing to better maternal and fetal health outcomes, which is essential to better guide clinical judgement.
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Introduction: The fetal haemodynamic response to acute episodes of hypoxaemia are well characterised. However, how these responses change when the hypoxaemia becomes more chronic in nature such as that associated with fetal growth restriction (FGR), is less well understood. Herein, we utilised a combination of clinically relevant MRI techniques to comprehensively characterize and differentiate the haemodynamic responses occurring during acute and chronic periods of fetal hypoxaemia. Methods: Prior to conception, carunclectomy surgery was performed on non-pregnant ewes to induce FGR. At 108-110 days (d) gestational age (GA), pregnant ewes bearing control (n = 12) and FGR (n = 9) fetuses underwent fetal catheterisation surgery. At 117-119 days GA, ewes underwent MRI sessions where phase-contrast (PC) and T2 oximetry were used to measure blood flow and oxygenation, respectively, throughout the fetal circulation during a normoxia and then an acute hypoxia state. Results: Fetal oxygen delivery (DO2) was lower in FGR fetuses than controls during the normoxia state but cerebral DO2 remained similar between fetal groups. Acute hypoxia reduced both overall fetal and cerebral DO2. FGR increased ductus venosus (DV) and foramen ovale (FO) blood flow during both the normoxia and acute hypoxia states. Pulmonary blood flow (PBF) was lower in FGR fetuses during the normoxia state but similar to controls during the acute hypoxia state when PBF in controls was decreased. Conclusion: Despite a prevailing level of chronic hypoxaemia, the FGR fetus upregulates the preferential streaming of oxygen-rich blood via the DV-FO pathway to maintain cerebral DO2. However, this upregulation is unable to maintain cerebral DO2 during further exposure to an acute episode of hypoxaemia. The haemodynamic alterations required at the level of the liver and lung to allow the DV-FO pathway to maintain cerebral DO2, may have lasting consequences on hepatic function and pulmonary vascular regulation after birth.
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BACKGROUND: Cardiac MRI feature tracking (FT) allows objective assessment of segmental left ventricular (LV) function following a myocardial infarction (MI), but its utilization in sheep, where interventions can be tested, is lacking. PURPOSE: To apply and validate FT in a sheep model of MI and describe post-MI LV remodeling. STUDY TYPE: Animal model, longitudinal. ANIMAL MODEL: Eighteen lambs (6 months, male, n = 14; female, n = 4; 25.2 ± 4.5 kg). FIELD STRENGTH/SEQUENCE: Two-dimensional balanced steady-state free precession (bSSFP) and 3D inversion recovery fast low angle shot (IR-FLASH) sequences at 3 T. ASSESSMENT: Seven lambs underwent test-retest imaging to assess FT interstudy reproducibility. MI was induced in the remaining 11 by coronary ligation with MRI being undertaken before and 15 days post-MI. Injury size was measured by late gadolinium enhancement (LGE) and LV volumes, LV mass, ejection fraction (LVEF), and wall thickness (LVWT) were measured, with FT measures of global and segmental radial, circumferential, and longitudinal strain. STATISTICAL TESTS: Sampling variability, inter-study, intra and interobserver reproducibility were assessed using Pearson's correlation, Bland-Altman analyses, and intra-class correlation coefficients (ICC). Diagnostic performance of segmental strain to predict LGE was assessed using receiver operating characteristic curve analysis. Significant differences were considered P < 0.05. RESULTS: Inter-study reproducibility of FT was overall good to excellent, with global strain being more reproducible than segmental strain (ICC = 0.89-0.98 vs. 0.77-0.96). MI (4.0 ± 3.7% LV mass) led to LV remodeling, as evident by significantly increased LV volumes and LV mass, and significantly decreased LVWT in injured regions, while LVEF was preserved (54.9 ± 6.9% vs. 55.6 ± 5.7%; P = 0.778). Segmental circumferential strain (CS) correlated most strongly with LGE. Basal and mid- CS increased significantly, while apical CS significantly decreased post-MI. DATA CONCLUSION: FT is reproducible and compensation by hyperkinetic remote myocardium may manifest as overall preserved global LV function. EVIDENCE LEVEL: N/A TECHNICAL EFFICACY: Stage 2.
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Increasing placental perfusion (PP) could improve outcomes of growth-restricted fetuses. One way of increasing PP may be by using phosphodiesterase (PDE)-5 inhibitors, which induce vasodilatation of vascular beds. We used a combination of clinically relevant magnetic resonance imaging (MRI) techniques to characterize the impact that tadalafil infusion has on maternal, placental and fetal circulations. At 116-117 days' gestational age (dGA; term, 150 days), pregnant ewes (n = 6) underwent fetal catheterization surgery. At 120-123 dGA ewes were anaesthetized and MRI scans were performed during three acquisition windows: a basal state and then â¼15-75 min (TAD 1) and â¼75-135 min (TAD 2) post maternal administration (24 mg; intravenous bolus) of tadalafil. Phase contrast MRI and T2 oximetry were used to measure blood flow and oxygen delivery. Placental diffusion and PP were assessed using the Diffusion-Relaxation Combined Imaging for Detailed Placental Evaluation-'DECIDE' technique. Uterine artery (UtA) blood flow when normalized to maternal left ventricular cardiac output (LVCO) was reduced in both TAD periods. DECIDE imaging found no impact of tadalafil on placental diffusivity or fetoplacental blood volume fraction. Maternal-placental blood volume fraction was increased in the TAD 2 period. Fetal D O 2 ${D_{{{\mathrm{O}}_2}}}$ and V Ì O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ were not affected by maternal tadalafil administration. Maternal tadalafil administration did not increase UtA blood flow and thus may not be an effective vasodilator at the level of the UtAs. The increased maternal-placental blood volume fraction may indicate local vasodilatation of the maternal intervillous space, which may have compensated for the reduced proportion of UtA D O 2 ${D_{{{\mathrm{O}}_2}}}$ .
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Oxigênio , Placenta , Circulação Placentária , Tadalafila , Artéria Uterina , Animais , Feminino , Tadalafila/farmacologia , Tadalafila/administração & dosagem , Gravidez , Ovinos , Artéria Uterina/efeitos dos fármacos , Placenta/efeitos dos fármacos , Placenta/irrigação sanguínea , Circulação Placentária/efeitos dos fármacos , Oxigênio/sangue , Fluxo Sanguíneo Regional/efeitos dos fármacos , Inibidores da Fosfodiesterase 5/farmacologia , Inibidores da Fosfodiesterase 5/administração & dosagem , Imageamento por Ressonância Magnética , Feto/irrigação sanguínea , Feto/efeitos dos fármacosRESUMO
BACKGROUND: Fetuses with cyanotic congenital heart disease (CHD) exhibit profound fetal circulatory disturbances that may affect early outcomes. OBJECTIVES: This study sought to investigate the relationship between fetal hemodynamics and early survival and neurodevelopmental (ND) outcomes in patients with cyanotic CHD. METHODS: In this longitudinal observational study, fetuses with cyanotic CHD underwent late gestational fetal cardiovascular magnetic resonance (CMR) to measure vessel blood flow and oxygen content. Superior vena cava (SVC) flow was used as a proxy for cerebral blood flow. Primary outcomes were 18-month mortality and Bayley Scales of Infant Development-III assessment. RESULTS: A total of 144 fetuses with cyanotic CHD were assessed. By 18 months, 18 patients (12.5%) died. Early mortality was associated with reduced combined ventricular output (P = 0.01), descending aortic flow (P = 0.04), and umbilical vein flow (P = 0.03). Of the surviving patients, 71 had ND outcomes assessed. Cerebral oxygen delivery was the fetal hemodynamic variable most strongly associated with cognitive, language, and motor outcomes (P < 0.05). Fetal SVC flow was also associated with cognitive, language, and motor outcomes (P < 0.01), and it remained an independent predictor of cognitive (P = 0.002) and language (P = 0.04) outcomes after adjusting for diagnosis. Diminished SVC flow also performed better than other fetal CMR and echocardiographic predictors of cognitive ND delay (receiver-operating characteristic curve area: 0.85; SE 0.05). CONCLUSIONS: Among fetuses with cyanotic CHD, diminished fetal combined ventricular output is associated with mortality, whereas cerebral blood flow and oxygen delivery are associated with early cognitive, language, and motor development at 18 months of age. These results support the inclusion of fetal CMR to help identify patients at risk of adverse ND outcomes.
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Cardiopatias Congênitas , Veia Cava Superior , Gravidez , Lactente , Feminino , Criança , Humanos , Veia Cava Superior/diagnóstico por imagem , Cardiopatias Congênitas/complicações , Cardiopatias Congênitas/diagnóstico , Hemodinâmica/fisiologia , Feto , OxigênioRESUMO
BACKGROUND: Non-Cartesian magnetic resonance imaging trajectories at golden angle increments have the advantage of allowing motion correction and gating using intermediate real-time reconstructions. However, when the acquired data are cardiac binned for cine imaging, trajectories can cluster together at certain heart rates (HR) causing image artifacts. Here, we demonstrate an approach to reduce clustering by inserting additional angular increments within the trajectory, and optimizing them while still allowing for intermediate reconstructions. METHODS: Three acquisition models were simulated under constant and variable HR: golden angle (Mtrd), random additional angles (Mrnd), and optimized additional angles (Mopt). The standard deviations of trajectory angular differences (STAD) were compared through their interquartile ranges (IQR) and the Kolmogorov-Smirnov test (significance level: p = 0.05). Agreement between an image reconstructed with uniform sampling and images from Mtrd, Mrnd, and Mopt was analyzed using the structural similarity index measure (SSIM). Mtrd and Mopt were compared in three adults at high, low, and no HR variability. RESULTS: STADs from Mtrd were significantly different (p < 0.05) from Mopt and Mrnd. STAD (IQR × 10-2 rad) showed that Mopt (0.5) and Mrnd (0.5) reduced clustering relative to Mtrd (1.9) at constant HR. For variable HR, Mopt (0.5) and Mrnd (0.5) outperformed Mtrd (0.9). The SSIM (IQR) showed that Mopt (0.011) produced the best image quality, followed by Mrnd (0.014), and Mtrd (0.030). Mopt outperformed Mtrd at reduced HR variability in in-vivo studies. At high HR variability, both models performed well. CONCLUSION: This approach reduces clustering in k-space and improves image quality.
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Artefatos , Frequência Cardíaca , Interpretação de Imagem Assistida por Computador , Imagem Cinética por Ressonância Magnética , Valor Preditivo dos Testes , Humanos , Reprodutibilidade dos Testes , Adulto , Masculino , Feminino , Técnicas de Imagem de Sincronização CardíacaRESUMO
While microplastics have been recently detected in human blood and the placenta, their impact on human health is not well understood. Using a mouse model of environmental exposure during pregnancy, our group has previously reported that exposure to polystyrene micro- and nanoplastics throughout gestation results in fetal growth restriction. While polystyrene is environmentally relevant, polyethylene is the most widely produced plastic and amongst the most commonly detected microplastic in drinking water and human blood. In this study, we investigated the effect of maternal exposure to polyethylene micro- and nanoplastics on fetal growth and placental function. Healthy, pregnant CD-1 dams were divided into three groups: 106 ng/L of 740-4990 nm polyethylene with surfactant in drinking water (n = 12), surfactant alone in drinking water (n = 12) or regular filtered drinking water (n = 11). At embryonic day 17.5, high-frequency ultrasound was used to investigate the placental and fetal hemodynamic responses following exposure. While maternal exposure to polyethylene did not impact fetal growth, there was a significant effect on placental function with a 43% increase in umbilical artery blood flow in the polyethylene group compared to controls (p < 0.01). These results suggest polyethylene has the potential to cause adverse pregnancy outcomes through abnormal placental function.
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Água Potável , Placenta , Humanos , Gravidez , Feminino , Placenta/irrigação sanguínea , Microplásticos , Plásticos , Exposição Materna/efeitos adversos , Polietileno/toxicidade , Poliestirenos , Desenvolvimento Fetal , Resultado da Gravidez , Hemodinâmica , Retardo do Crescimento Fetal , TensoativosRESUMO
BACKGROUND: Cardiovascular disease (CVD) is excessively prevalent and premature in bipolar disorder (BD), even after controlling for traditional cardiovascular risk factors. The increased risk of CVD in BD may be subserved by microvascular dysfunction. We examined coronary microvascular function in relation to youth BD. METHODS: Participants were 86 youth, ages 13-20 years (n = 39 BD, n = 47 controls). Coronary microvascular reactivity (CMVR) was assessed using quantitative T2 magnetic resonance imaging during a validated breathing-paradigm. Quantitative T2 maps were acquired at baseline, following 60-s of hyperventilation, and every 10-s thereafter during a 40-s breath-hold. Left ventricular structure and function were evaluated based on 12-15 short- and long-axis cardiac-gated cine images. A linear mixed-effects model that controlled for age, sex, and body mass index assessed for between-group differences in CMVR (time-by-group interaction). RESULTS: The breathing-paradigm induced a significant time-related increase in T2 relaxation time for all participants (i.e. CMVR; ß = 0.36, p < 0.001). CMVR was significantly lower in BD v. controls (ß = -0.11, p = 0.002). Post-hoc analyses found lower T2 relaxation time in BD youth after 20-, 30-, and 40 s of breath-holding (d = 0.48, d = 0.72, d = 0.91, respectively; all pFDR < 0.01). Gross left ventricular structure and function (e.g. mass, ejection fraction) were within normal ranges and did not differ between groups. CONCLUSION: Youth with BD showed evidence of subclinically impaired coronary microvascular function, despite normal gross cardiac structure and function. These results converge with prior findings in adults with major depressive disorder and post-traumatic stress disorder. Future studies integrating larger samples, prospective follow-up, and blood-based biomarkers are warranted.
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Transtorno Bipolar , Doenças Cardiovasculares , Transtorno Depressivo Maior , Adulto , Humanos , Adolescente , Transtorno Bipolar/diagnóstico por imagem , Estudos Prospectivos , Imageamento por Ressonância MagnéticaRESUMO
Maternal exposure to microplastics and nanoplastics has been shown to result in fetal growth restriction in mice. In this study, we investigated the placental and fetal hemodynamic responses to plastics exposure in mice using high-frequency ultrasound. Healthy, pregnant CD-1 dams were given either 106 ng/L of 5 µm polystyrene microplastics or 106 ng/L of 50 nm polystyrene nanoplastics in drinking water throughout gestation and were compared with controls. Maternal exposure to both microplastics and nanoplastics resulted in evidence of placental dysfunction that was highly dependent on the particle size. The umbilical artery blood flow increased by 48% in the microplastic-exposed group and decreased by 25% in the nanoplastic-exposed group compared to controls (p < 0.05). The microplastic- and nanoplastic-exposed fetuses showed a significant decrease in the middle cerebral artery pulsatility index of 10% and 13%, respectively, compared to controls (p < 0.05), indicating vasodilation of the cerebral circulation, a fetal adaptation that is part of the brain sparing response to preserve oxygen delivery. Hemodynamic markers of placental dysfunction and fetal hypoxia were more pronounced in the group exposed to polystyrene nanoplastics, suggesting nanoplastic exposure during human pregnancy has the potential to disrupt fetal brain development, which in turn may cause suboptimal neurodevelopmental outcomes.
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Microplásticos , Plásticos , Gravidez , Feminino , Humanos , Animais , Camundongos , Poliestirenos/toxicidade , Placenta/irrigação sanguínea , Desenvolvimento FetalRESUMO
Babies born with fetal growth restriction (FGR) are at higher risk of developing cardiometabolic diseases across the life course. The reduction in substrate supply to the developing fetus that causes FGR not only alters cardiac growth and structure but may have deleterious effects on metabolism and function. Using a sheep model of placental restriction to induce FGR, we investigated key cardiac metabolic and functional markers that may be altered in FGR. We also employed phase-contrast magnetic resonance imaging MRI to assess left ventricular cardiac output (LVCO) as a measure of cardiac function. We hypothesized that signalling molecules involved in cardiac fatty acid utilisation and contractility would be impaired by FGR and that this would have a negative impact on LVCO in the late gestation fetus. Key glucose (GLUT4 protein) and fatty acid (FATP, CD36 gene expression) substrate transporters were significantly reduced in the hearts of FGR fetuses. We also found reduced mitochondrial numbers as well as abundance of electron transport chain complexes (complexes II and IV). These data suggest that FGR diminishes metabolic and mitochondrial capacity in the fetal heart; however, alterations were not correlated with fetal LVCO. Overall, these data show that FGR alters fetal cardiac metabolism in late gestation. If sustained ex utero, this altered metabolic profile may contribute to poor cardiac outcomes in FGR-born individuals after birth. KEY POINTS: Around the time of birth, substrate utilisation in the fetal heart switches from carbohydrates to fatty acids. However, the effect of fetal growth restriction (FGR) on this switch, and thus the ability of the fetal heart to effectively metabolise fatty acids, is not fully understood. Using a sheep model of early onset FGR, we observed significant downregulation in mRNA expression of fatty acid receptors CD36 and FABP in the fetal heart. FGR fetuses also had significantly lower cardiac mitochondrial abundance than controls. There was a reduction in abundance of complexes II and IV within the electron transport chain of the FGR fetal heart, suggesting altered ATP production. This indicates reduced fatty acid metabolism and mitochondrial function in the heart of the FGR fetus, which may have detrimental long-term implications and contribute to increased risk of cardiovascular disease later in life.
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INTRODUCTION: Plastics used in everyday materials accumulate as waste in the environment and degrade over time. The impacts of the resulting particulate micro- and nanoplastics on human health remain largely unknown. In pregnant mice, we recently demonstrated that exposure to nanoplastics throughout gestation and during lactation resulted in changes in brain structure detected on MRI. One possible explanation for this abnormal postnatal brain development is altered fetal brain metabolism. OBJECTIVES: To determine the effect of maternal exposure to nanoplastics on fetal brain metabolism. METHODS: Healthy pregnant CD-1 mice were exposed to 50 nm polystyrene nanoplastics at a concentration of 106 ng/L through drinking water during gestation. Fetal brain samples were collected at embryonic day 17.5 (n = 18-21 per group per sex) and snap-frozen in liquid nitrogen. Magic angle spinning nuclear magnetic resonance was used to determine metabolite profiles and their relative concentrations in the fetal brain. RESULTS: The relative concentrations of gamma-aminobutyric acid (GABA), creatine and glucose were found to decrease by 40%, 21% and 30% respectively following maternal nanoplastic exposure when compared to the controls (p < 0.05). The change in relative concentration of asparagine with nanoplastic exposure was dependent on fetal sex (p < 0.005). CONCLUSION: Maternal exposure to polystyrene nanoplastics caused abnormal fetal brain metabolism in mice. The present study demonstrates the potential impacts of nanoplastic exposure during fetal development and motivates further studies to evaluate the risk to human pregnancies.
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Microplásticos , Poliestirenos , Gravidez , Humanos , Feminino , Animais , Camundongos , Exposição Materna/efeitos adversos , Metabolômica , EncéfaloRESUMO
Late gestational supine positioning reduces maternal cardiac output due to inferior vena caval (IVC) compression, despite increased collateral venous return. However, little is known about the impact of maternal position on oxygen (O2 ) delivery and consumption of the gravid uterus, fetus, placenta and lower limbs. We studied the effects of maternal positioning on these parameters in 20 healthy pregnant subjects at 36 ± 2 weeks using magnetic resonance imaging (MRI); a follow-up MRI was performed 6-months postpartum (n = 16/20). MRI techniques included phase-contrast and T1/T2 relaxometry for blood flow and oximetry imaging, respectively. O2 transport was measured in the following vessels (bilateral where appropriate): maternal abdominal descending aorta (DAoabdo ), IVC, ovarian, paraspinal veins (PSV), uterine artery (UtA) and external iliacs, and umbilical. Maternal cardiac output was measured by summing DAothoracic and superior vena cava flows. Supine mothers (n = 6) had lower cardiac output and O2 delivery in the DAoabdo , UtA and external iliac arteries, and higher PSV flow than those in either the left (n = 8) or right (n = 6) lateral positions during MRI. However, O2 consumption in the gravid uterus, fetus, placenta and lower limbs was unaffected by maternal positioning. The ratio of IVC/PSV flow decreased in supine mothers while ovarian venous flow and O2 saturation were unaltered, suggesting a major route of pelvic venous return unaffected by maternal position. Placental-fetal O2 transport and consumption were similar between left and right lateral maternal positions. In comparison to non-pregnant findings, DAoabdo and UtA O2 delivery and pelvic O2 consumption increased, while lower-limb consumption remained constant , despite reduced external iliac artery O2 delivery in late gestation. KEY POINTS: Though sleeping supine during the third trimester is associated with an increased risk of antepartum stillbirth, the underlying biological mechanisms are not fully understood. Maternal cardiac output and uteroplacental flow are reduced in supine mothers due to inferior vena caval compression from the weight of the gravid uterus. This MRI study provides a comprehensive circulatory assessment, demonstrating reduced maternal cardiac output and O2 delivery (uteroplacental, lower body) in supine compared to lateral positioning; however, O2 consumption (gravid uterus, fetus, placenta, lower limbs) was preserved. Unlike other mammalian species, the ovarian veins conduct substantial venous return from the human pregnant uterus that is unaffected by maternal positioning. Lumbar paraspinal venous flow increased in supine mothers. These observations may have important considerations during major pelvic surgery in pregnancy (i.e. placenta percreta). Future studies should address the importance of maternal positioning as a potential tool to deliver improved perinatal outcomes in pregnancies with compromised uteroplacental O2 delivery.
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Placenta , Veia Cava Superior , Feminino , Humanos , Gravidez , Estudos de Viabilidade , Feto/diagnóstico por imagem , Feto/irrigação sanguínea , Imageamento por Ressonância Magnética , Oxigênio , Consumo de Oxigênio , Placenta/diagnóstico por imagemRESUMO
Babies born growth restricted are at an increased risk of both poor short-and long-term outcomes. Current interventions to improve fetal growth are ineffective and do not lower the lifetime risk of poor health status. Maternal resveratrol (RSV) treatment increases uterine artery blood flow, fetal oxygenation, and fetal weight. However, studies suggest that diets high in polyphenols such as RSV may impair fetal hemodynamics. We aimed to characterize the effect of RSV on fetal hemodynamics to further assess its safety as an intervention strategy. Pregnant ewes underwent magnetic resonance imaging (MRI) scans to measure blood flow and oxygenation within the fetal circulation using phase contrast-MRI and T2 oximetry. Blood flow and oxygenation measures were performed in a basal state and then repeated while the fetus was exposed to RSV. Fetal blood pressure and heart rate were not different between states. RSV did not impact fetal oxygen delivery (DO2 ) or consumption (VO2 ). Blood flow and oxygen delivery throughout the major vessels of the fetal circulation were not different between basal and RSV states. As such, acute exposure of the fetus to RSV does not directly impact fetal hemodynamics. This strengthens the rationale for the use of RSV as an intervention strategy against fetal growth restriction.
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Feto , Hemodinâmica , Gravidez , Ovinos , Animais , Feminino , Resveratrol/farmacologia , Desenvolvimento Fetal , OxigênioRESUMO
Fetal cardiac MRI is challenging due to fetal and maternal movements as well as the need for a reliable cardiac gating signal and high spatiotemporal resolution. Ongoing research and recent technical developments to address these challenges show the potential of MRI as an adjunct to ultrasound for the assessment of the fetal heart and great vessels. MRI measurements of blood flow have enabled the assessment of normal fetal circulation as well as conditions with disrupted circulations, such as congenital heart disease, along with associated organ underdevelopment and hemodynamic instability. This review provides details of the techniques used in fetal cardiovascular blood flow MRI, including single slice and volumetric imaging sequences, post-processing and analysis, along with a summary of applications in human studies and animal models.
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Cardiopatias Congênitas , Imageamento por Ressonância Magnética , Animais , Gravidez , Humanos , Feminino , Imageamento por Ressonância Magnética/métodos , Hemodinâmica , Coração Fetal/diagnóstico por imagemRESUMO
INTRODUCTION: The rapid growth in the worldwide use of plastics has resulted in a vast accumulation of microplastics in the air, soil and water. The impact of these microplastics on pregnancy and fetal development remains largely unknown. In pregnant mice, we recently demonstrated that exposure to micro- and nanoplastics throughout gestation resulted in significant fetal growth restriction. One possible explanation for reduced fetal growth is abnormal placental metabolism. OBJECTIVES: To evaluate the effect of maternal exposure to microplastics on placental metabolism. METHODS: In the present study, CD-1 pregnant mice were exposed to 5 µm polystyrene microplastics in filtered drinking water at one of four concentrations (0 ng/L (controls), 102 ng/L, 104 ng/L, 106 ng/L) throughout gestation (n = 7-11/group). At embryonic day 17.5, placental tissue samples were collected (n = 28-44/group). Metabolite profiles were determined using 1 H high-resolution magic angle spinning magnetic resonance spectroscopy. RESULTS: The relative concentration of lysine (p = 0.003) and glucose (p < 0.0001) in the placenta were found to decrease with increasing microplastic concentrations, with a significant reduction at the highest exposure concentration. Multivariate analysis identified shifts in the metabolic profile with MP exposure and pathway analysis identified perturbations in the biotin metabolism, lysine degradation, and glycolysis/gluconeogenesis pathways. CONCLUSION: Maternal exposure to microplastics resulted in significant alterations in placental metabolism. This study highlights the potential impact of microplastic exposure on pregnancy outcomes and that efforts should be made to minimize exposure to plastics, particularly during pregnancy.
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Microplásticos , Placenta , Humanos , Gravidez , Feminino , Animais , Camundongos , Placenta/metabolismo , Microplásticos/metabolismo , Poliestirenos/metabolismo , Plásticos/metabolismo , Exposição Materna/efeitos adversos , Lisina/metabolismo , MetabolômicaRESUMO
INTRODUCTION: Newborns exposed to sildenafil citrate (SC) in utero have increased rates of persistent pulmonary hypertension. The mechanism behind this has not yet been fully elucidated. We aimed to utilize a combination of clinically relevant MRI techniques to comprehensively characterize the haemodynamics of the fetal sheep whilst under the influence of SC. We hypothesized that these MRI techniques would detect SC-induced increases in pulmonary blood flow and oxygen delivery prior to birth. METHODS: At 116-117 days gestational age (term, 150 days), pregnant Merino ewes (n = 9) underwent fetal catheterization surgery. MRI scans were performed during a basal state and then repeated during a constant umbilical vein infusion of SC to measure blood flow and oxygenation within the major vessels of the fetal circulation using phase-contrast-MRI and T2 oximetry. RESULTS: Right and left ventricular cardiac outputs were not different between states. Pulmonary blood flow increased during the SC state resulting in elevated pulmonary oxygen delivery. Right to left heart shunting through the foramen ovale was reduced without reducing cerebral oxygen delivery. CONCLUSION: SC induces alterations to pulmonary haemodynamics in utero; a characteristic that if maintained may underlie or act as a precursor towards the elevated rates of poor pulmonary outcomes after birth. These MRI techniques are the first to comprehensively characterize sildenafil's direct impact on the pulmonary vasculature and its indirect detriment to the flow of oxygen-rich blood through the foramen ovale.
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Oxigênio , Ovinos , Animais , Feminino , Citrato de Sildenafila/farmacologiaRESUMO
Magnetic resonance imaging (MRI) assessment of fetal blood oxygen saturation (SO2 ) can transform the clinical management of high-risk pregnancies affected by fetal growth restriction (FGR). Here, a novel MRI method assesses the feasibility of identifying normally grown and FGR fetuses in sheep and is then applied to humans. MRI scans are performed in pregnant ewes at 110 and 140 days (term = 150d) gestation and in pregnant women at 28+3 ± 2+5 weeks to measure feto-placental SO2 . Birth weight is collected and, in sheep, fetal blood SO2 is measured with a blood gas analyzer (BGA). Fetal arterial SO2 measured by BGA predicts fetal birth weight in sheep and distinguishes between fetuses that are normally grown, small for gestational age, and FGR. MRI feto-placental SO2 in late gestation is related to fetal blood SO2 measured by BGA and body weight. In sheep, MRI feto-placental SO2 in mid-gestation is related to fetal SO2 later in gestation. MRI feto-placental SO2 distinguishes between normally grown and FGR fetuses, as well as distinguishing FGR fetuses with and without normal Doppler in humans. Thus, a multi-compartment placental MRI model detects low placental SO2 and distinguishes between small hypoxemic fetuses and normally grown fetuses.
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Retardo do Crescimento Fetal , Placenta , Feminino , Animais , Humanos , Gravidez , Ovinos , Placenta/diagnóstico por imagem , Placenta/patologia , Peso ao Nascer , Retardo do Crescimento Fetal/diagnóstico por imagem , Imageamento por Ressonância Magnética , Feto/diagnóstico por imagem , Feto/patologiaRESUMO
Fetal development relies on a complex circulatory network. Accurate assessment of flow distribution is important for understanding pathologies and potential therapies. In this paper, we demonstrate a method for volumetric imaging of fetal flow with magnetic resonance imaging (MRI). Fetal MRI faces challenges: small vascular structures, unpredictable motion, and inadequate traditional cardiac gating methods. Here, orthogonal multislice stacks are acquired with accelerated multidimensional radial phase contrast (PC) MRI. Slices are reconstructed into flow sensitive time-series images with motion correction and image-based cardiac gating. They are then combined into a dynamic volume using slice-to-volume reconstruction (SVR) while resolving interslice spatiotemporal coregistration. Compared to prior methods, this approach achieves higher spatiotemporal resolution ( 1×1×1 mm3, ~30 ms) with reduced scan time - important features for the quantification of flow through small fetal structures. Validation is demonstrated in adults by comparing SVR with 4D radial PCMRI (flow bias and limits of agreement: -1.1 ml/s and [-11.8 9.6] ml/s). Feasibility is demonstrated in late gestation fetuses by comparing SVR with 2D Cartesian PCMRI (flow bias and limits of agreement: -0.9 ml/min/kg and [-39.7 37.8] ml/min/kg). With SVR, we demonstrate complex flow pathways (such as parallel flow streams in the proximal inferior vena cava, preferential shunting of blood from the ductus venosus into the left atrium, and blood from the brain leaving the heart through the main pulmonary artery) for the first time in human fetal circulation. This method allows for comprehensive evaluation of the fetal circulation and enables future studies of fetal physiology.