Cerebral Blood Flow Measured by Phase-Contrast Magnetic Resonance Angiography in Preterm and Term Neonates

Noninvasive microvascular imaging in newborn rats using high-frequency ultrafast ultrasound

Ultrasound imaging stands as the predominant modality for neonatal health assessment, with recent advancements in ultrafast Doppler (μDoppler) technology offering significant promise in fields such as neonatal brain imaging. Combining μDoppler with high-frequency ultrasound (HF-μDoppler) presents a potential efficient avenue to enhance in vivo microvascular imaging in small animals, notably newborn rats, a crucial preclinical animal model for neonatal disease and development research. It is necessary to verify the imaging performance of HF-μDoppler in preclinical trials. This study investigates the microvascular imaging capabilities of HF-μDoppler using a 30 MHz high-frequency linear array probe in newborn rats. Results demonstrate the clarity of cerebral microvascular imaging in rats aged 1 to 7 postnatal days, extending to whole-body microvascular imaging, encompassing the central nervous system, including the brain and spinal cord. In conclusion, HF-μDoppler technology emerges as a reliable imaging tool, offering a new perspective for preclinical investigations into neonatal diseases and development.

Automated Quantification of Total Cerebral Blood Flow from Phase-Contrast MRI and Deep Learning

Knowledge of input blood to the brain, which is represented as total cerebral blood flow (tCBF), is important in evaluating brain health. Phase-contrast (PC) magnetic resonance imaging (MRI) enables blood velocity mapping, allowing for noninvasive measurements of tCBF. In the procedure, manual selection of brain-feeding arteries is an essential step, but is time-consuming and often subjective. Thus, the purpose of this work was to develop and validate a deep learning (DL)-based technique for automated tCBF quantifications. To enhance the DL segmentation performance on arterial blood vessels, in the preprocessing step magnitude and phase images of PC MRI were multiplied several times. Thereafter, a U-Net was trained on 218 images for three-class segmentation. Network performance was evaluated in terms of the Dice coefficient and the intersection-over-union (IoU) on 40 test images, and additionally, on externally acquired 20 datasets. Finally, tCBF was calculated from the DL-predicted vessel segmentation maps, and its accuracy was statistically assessed with the correlation of determination (R2), the intraclass correlation coefficient (ICC), paired t-tests, and Bland-Altman analysis, in comparison to manually derived values. Overall, the DL segmentation network provided accurate labeling of arterial blood vessels for both internal (Dice=0.92, IoU=0.86) and external (Dice=0.90, IoU=0.82) tests. Furthermore, statistical analyses for tCBF estimates revealed good agreement between automated versus manual quantifications in both internal (R2=0.85, ICC=0.91, p=0.52) and external (R2=0.88, ICC=0.93, p=0.88) test groups. The results suggest feasibility of a simple and automated protocol for quantifying tCBF from neck PC MRI and deep learning.

Developmental priming of early cerebrovascular ageing: Implications across a lifetime

INTRODUCTION

Neurological conditions such as Alzheimer's disease and stroke represent a substantial health burden to the world's ageing population. Cerebrovascular dysfunction is a key contributor to these conditions, affecting an individual's risk profile, age of onset, and severity of neurological disease. Recent data shows that early-life events, such as maternal health during pregnancy, birth weight and exposure to environmental toxins can 'prime' the vascular system for later changes. With age, blood vessels can become less flexible and more prone to damage. This can lead to reduced blood flow to the brain, which is associated with cognitive decline and an increased risk of stroke and other cerebrovascular diseases. These in turn increase the risk of vascular dementia and Alzheimer's disease.

OBJECTIVES

We aim to explore how early life factors influence cerebrovascular health, ageing and disease.

METHODS

We have reviewed recently published literature from epidemiological studies, clinical cases and basic research which explore mechanisms that contribute to cerebrovascular and blood-brain barrier dysfunction, with a particularly focus on those that assess contribution of early-life events or vascular priming to subsequent injury.

RESULTS

Perinatal events have been linked to acute cerebrovascular dysfunction and long-term structural reorganisation. Systemic disease throughout the lifetime that produce inflammatory or oxidative stress may further sensitise the cerebrovasculature to disease and contribute to neurodegeneration.

CONCLUSIONS

By identifying these early-life determinants and understanding their mechanisms, scientists aim to develop strategies for preventing or mitigating cerebrovascular ageing-related issues.

Hemodynamic performance evaluation of neonatal ECMO double lumen cannula using fluid-structure interaction

Extra corporeal membrane oxygenation (ECMO) is an artificial oxygenation facility, employed in situations of cardio-pulmonary failure. Some diseases i.e., acute respiratory distress syndrome, pulmonary hypertension, corona virus disease (COVID-19) etc. affect oxygenation performance of the lungs thus requiring the need of artificial oxygenation. Critical care teams used ECMO technique during the COVID-19 pandemic to support the heart and lungs of COVID-19 patients who had an acute respiratory or cardiac failure. Double Lumen Cannula (DLC) is one of the most critical components of ECMO as it resides inside the patient and, connects patient with external oxygenation circuit. DLC facilitates delivery and drainage of blood from the patient's body. DLC is characterized by delicate balance of internal and external flows inside a limited space of the right atrium (RA). An optimal performance of the DLC necessitates structural stability under biological and hemodynamic loads, a fact that has been overlooked by previously published studies. In the past, many researchers experimentally and computationally investigated the hemodynamic performance of DLC by employing Eulerian approach, which evaluate instantaneous blood damage without considering blood shear exposure history (qualitative assessment only). The present study is an attempt to address the aforementioned limitations of the previous studies by employing Lagrangian (quantitative assessment) and incorporating the effect of fluid-structure interaction (FSI) to study the hemodynamic performance of neonatal DLC. The study was performed by solving three-dimensional continuity, momentum, and structural mechanics equation(s) by numerical methods for the blood flow through neonatal DLC. A two-way coupled FSI analysis was performed to analyze the effect of DLC structural deformation on its hemodynamic performance. Results show that the return lumen was the most critical section with maximum pressure drop, velocity, shear stresses, and blood damage. Recirculation and residence time of blood in the right atrium (RA) increases with increasing blood flow rates. Considering the structural deformation has led to higher blood damage inside the DLC-atrium system. Maximum Von-Mises stress was present on the side edges of the return lumen that showed direct proportionality with the blood flow rate.

Intraventricular hemorrhage prediction in premature neonates in the era of hemodynamics monitoring: a prospective cohort study

Unstable hemodynamics and prematurity are the main players in intraventricular hemorrhage (IVH) development. Our objective was to study 8 the use of superior vena cava flow (SVCF), left ventricular output (LVO), and right ventricular output (RVO), and anterior cerebral artery (ACA) Doppler measures in prediction of IVH in the first week of life in preterm infant ≤ 32 weeks and birth weight ≤ 1500 g. This prospective cohort study was conducted in 55NICU of Alexandria University maternity hospital. Of 147 enrolled patients, 132 infants born ≤ 32 weeks GA and birth weight ≤ 1500 g were eligible for- the study. One hundred twenty-seven infants completed the study. Infants were scanned for ACA-RI using transfontanellar ultrasound, and SVCF, LVO, and RVO using functional echocardiography in the first 24 h after birth. Patients had another two scans on DOL3 and 7 to detect IVH development. Low SVCF and high ACA-RI significantly increased the risk of IVH using logistic regression models with OR, 3.16; 95%CI, 1.19-8.39; P = 0.02 and OR, 1.64; 95%Cl, 1.10-2.44; P = 0.02, respectively. Low SVCF and high ACA-RI significantly increased risk of catastrophic IVH P = 0.025 and 0.023, respectively. Combined use of low SVCF < 55 ml/kg/min and ACA-RI > 0.75 is predictor of IVH with sensitivity 40.8% and 82.1% specificity.

CONCLUSIONS

There are strong relations between both low SVCF and high ACA-RI, and IVH development in premature neonates ≤ 32 weeks and birth weight ≤ 1500 g, with more significance towards catastrophic IVH. Admission RSS and LVO are the strongest factors affecting SVCF. Maternal anemia, patent ductus arteriosus size (mm/kg), and capillary refill time were significantly associated with high ACA-RI. These findings help in more understanding of pathophysiological factors affecting central perfusion that might affect the longer term neurodeveopmental outcome.

TRIAL REGISTRATION

This work was registered in clinical trial.gv no NCT05050032.

WHAT IS KNOWN

•Whether SVCF and RI-ACA can predict IVH in preterm neonates is still debatable.

WHAT IS NEW

•Low SVC flow and high ACA-RI significantly increased risk of IVH, confirming the role of hypoperfusion-reperfusion cycle in IVH development. The most striking result that combined metrics using the cut-off value of < 41 ml/kg/min for SVCF and > 0.85 for ACA-RI "in the first day of life" can correctly reject the presence of IVH in 98% of patients "during the first week of life."

Evaluation of static ulcer on lower extremities using wireless wearable near-infrared spectroscopy device: Effect of deep venous thrombosis on TRiggered Angiography Non-Contrast-Enhanced sequence magnetic resonance imaging

BACKGROUND

Venous leg ulcers, or static leg ulcers, are chronic wounds associated with ambulatory venous hypertension of the lower extremities as a consequence of venous valve reflux, reduce venous capacitance, poor calf venous pump, heart failure, or in conjunction with venous obstruction. A static ulcer with venous thrombosis in a pelvic or thigh vein responds favorably to anticoagulation agents. However, anticoagulation is less effective and even harmful when ambulatory venous hypertension has another cause such as venous reflux, poorly heart function, and poor calf venous pump.

METHOD

TRiggered Angiography Non-Contrast-Enhanced (TRANCE) magnetic resonance imaging (MRI) exploits differences in vascular signal intensity during the cardiac cycle for subsequent image subtraction, providing detailed radiation-free venograms without the use of contrast agents. The method is a new tool for evaluating the presence of thrombosis in the venous systems. TRANCE-MRI was employed to document the existence of venous thrombosis within the eight patients in this study. Subsequently, we used a wireless wearable near-infrared spectroscopy device to compare deep vein thrombosis-associated and non-deep vein thrombosis-associated static ulcers. The sampling depths were 5 and 10 mm, representing the dermis and subcutaneous tissue, respectively.

RESULT

There are four patients with venous leg ulcers proven with venous thrombosis by TRANCE-MRI and are classified as deep vein thrombosis group. Compared with the non-deep vein thrombosis group, the deep vein thrombosis group had less deoxyhemoglobin, less total hemoglobin, and a significantly lower H₂O signal in the 5-mm sampling depth (dermis level). And eight health participants were included as control group. Wounded patients (including deep vein thrombosis and non-deep vein thrombosis patients) have higher H₂O concentration on the 5-mm depth sampling than control group. In the 10-mm sampling depth (subcutaneous level), the deoxyhemoglobin and tissue oxygen saturation of the deep vein thrombosis group were lower than those of the non-deep vein thrombosis group, and the H₂O concentration was higher than non-deep vein thrombosis group. Patients with static foot ulcers and deep vein thrombosis had similar oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and tissue oxygen saturation than did those without deep vein thrombosis in 5-mm depth sampling (dermis level). Notably, the H₂O signal of patients with non-deep vein thrombosis-associated static ulcers was higher for the 5-mm sampling depth.

CONCLUSION

In patients with static ulcers and deep vein thrombosis, the H₂O level may be higher in the 10-mm sampling depth, indicating that those patients had more subcutaneous water. In patients with non-deep vein thrombosis static foot ulcer, the near-infrared spectroscopy (NIRS) indicated worse fluid retention in the dermis level. The H₂O value in the NIRS may be different owing to underline the cause of the venous leg ulcers.

Placental Pathology, Cerebral Blood Flow, and Intraventricular Hemorrhage in Preterm Infants: Is There a Link?

BACKGROUND

There is growing evidence to support an association between placental inflammation and neurological sequelae of preterm infants. The goal of this study is to evaluate the relationship between placental pathology, post-natal Doppler cerebral resistive indices (RI's), and intraventricular hemorrhage (IVH) in premature infants.

METHODS

In a retrospective cohort study, preterm infants born between 23 0/7 and 32 6/7 weeks' gestation at Parkland Hospital were examined with placental pathology and serial ultrasound Doppler to evaluate for the primary outcome of IVH and death.

RESULTS

A total of 255 infants were included, and 166 (65%) had at least one significant placental pathology, most commonly chorioamnionitis. Infants with placental pathologies were significantly more likely to have mothers with clinical chorioamnionitis and to have lower gestational ages. There was no observed association between placental pathology and IVH or death. Secondary analysis demonstrated that resistive indices obtained from the first and second head ultrasounds were not different in infants with IVH.

CONCLUSION

In this study, we observed a high rate of placental pathologies but no alterations in cerebral indices on ultrasound, or differences in rates of IVH or death. Additional studies are necessary to delineate the relationship between placental pathology, white matter brain injury, and outcomes.