Longitudinal Trajectories of Regional Cerebral Blood Flow in Very Preterm Infants during Third Trimester Ex Utero Development Assessed with MRI

Neurodevelopmental outcome in preterm infants with intraventricular hemorrhages: the potential of quantitative brainstem MRI

OBJECTIVES

This retrospective study aimed to identify quantitative magnetic resonance imaging markers in the brainstem of preterm neonates with intraventricular hemorrhages. It delves into the intricate associations between quantitative brainstem magnetic resonance imaging metrics and neurodevelopmental outcomes in preterm infants with intraventricular hemorrhage, aiming to elucidate potential relationships and their clinical implications.

MATERIALS AND METHODS

Neuroimaging was performed on preterm neonates with intraventricular hemorrhage using a multi-dynamic multi-echo sequence to determine T1 relaxation time, T2 relaxation time, and proton density in specific brainstem regions. Neonatal outcome scores were collected using the Bayley Scales of Infant and Toddler Development. Statistical analysis aimed to explore potential correlations between magnetic resonance imaging metrics and neurodevelopmental outcomes.

RESULTS

Sixty preterm neonates (mean gestational age at birth 26.26 ± 2.69 wk; n = 24 [40%] females) were included. The T2 relaxation time of the midbrain exhibited significant positive correlations with cognitive (r = 0.538, P < 0.0001, Pearson's correlation), motor (r = 0.530, P < 0.0001), and language (r = 0.449, P = 0.0008) composite scores at 1 yr of age.

CONCLUSION

Quantitative magnetic resonance imaging can provide valuable insights into neurodevelopmental outcomes after intraventricular hemorrhage, potentially aiding in identifying at-risk neonates. Multi-dynamic multi-echo sequence sequences hold promise as an adjunct to conventional sequences, enhancing the sensitivity of neonatal magnetic resonance neuroimaging and supporting clinical decision-making for these vulnerable patients.

Evaluation of the effect of intraventricular haemorrhage on cerebral perfusion in preterm neonates using three-dimensional pseudo-continuous arterial spin labelling

BACKGROUND

Intraventricular haemorrhage (IVH) often arises as a cerebral complication directly related to preterm birth. The impaired autoregulation of cerebral blood flow is closely associated with IVH in preterm neonates. Three-dimensional pseudo-continuous arterial spin labelling (3D-pCASL) is a noninvasive magnetic resonance imaging (MRI) technique used for evaluating cerebral perfusion.

OBJECTIVE

This study aimed to compare cerebral blood flow values among three distinct groups using 3D-pCASL: preterm neonates with and without IVH and preterm neonates at term-equivalent age.

MATERIALS AND METHODS

A total of 101 preterm neonates who underwent conventional MRI and 3D-pCASL were included in this study. These neonates were categorised into three groups: 12 preterm neonates with IVH, 52 preterm neonates without IVH, and 37 healthy neonates at term-equivalent age. Cerebral blood flow measurements were obtained from six brain regions of interest (ROIs)-the frontal lobe, temporal lobe, parietal lobe, occipital lobe, basal ganglia, and thalamus-in the right and left hemispheres.

RESULTS

The cerebral blood flow values measured in all ROIs of preterm neonates with IVH were significantly lower than those of neonates at term-equivalent age (all P<0.05). Additionally, the cerebral blood flow in the temporal lobe was lower in preterm neonates without IVH than in neonates at term-equivalent age (16.87±5.01 vs. 19.76±5.47 ml/100 g/min, P=0.012). Furthermore, a noteworthy positive correlation was observed between post-menstrual age and cerebral blood flow in the temporal lobe (P=0.037), basal ganglia (P=0.010), and thalamus (P=0.010).

CONCLUSION

The quantitative cerebral blood flow values, as measured by 3D-pCASL, highlighted that preterm neonates with IVH had decreased cerebral perfusion. This finding underscores the potential of 3D-pCASL as a technique for evaluating the developmental aspects of the brain in preterm neonates.

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.

Measuring Quantitative Cerebral Blood Flow in Healthy Children: A Systematic Review of Neuroimaging Techniques

Cerebral blood flow (CBF) is an important hemodynamic parameter to evaluate brain health. It can be obtained quantitatively using medical imaging modalities such as magnetic resonance imaging and positron emission tomography (PET). Although CBF in adults has been widely studied and linked with cerebrovascular and neurodegenerative diseases, CBF data in healthy children are sparse due to the challenges in pediatric neuroimaging. An understanding of the factors affecting pediatric CBF and its normal range is crucial to determine the optimal CBF measuring techniques in pediatric neuroradiology. This review focuses on pediatric CBF studies using neuroimaging techniques in 32 articles including 2668 normal subjects ranging from birth to 18 years old. A systematic literature search was conducted in PubMed, Embase, and Scopus and reported following the preferred reporting items for systematic reviews and meta-analyses (PRISMA). We identified factors (such as age, gender, mood, sedation, and fitness) that have significant effects on pediatric CBF quantification. We also investigated factors influencing the CBF measurements in infants. Based on this review, we recommend best practices to improve CBF measurements in pediatric neuroimaging. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 2.

Cerebral blood flow patterns in preterm and term neonates assessed with pseudo-continuous arterial spin labeling perfusion MRI

In preterm (PT) infants, regional cerebral blood flow (CBF) disturbances may predispose to abnormal brain maturation even without overt brain injury. Therefore, it would be informative to determine the spatial distribution of grey matter (GM) CBF in PT and full-term (FT) newborns at term-equivalent age (TEA) and to assess the relationship between the features of the CBF pattern and both prematurity and prematurity-related brain lesions. In this prospective study, we obtained measures of CBF in 66 PT (51 without and 15 with prematurity-related brain lesions) and 38 FT newborns through pseudo-continuous arterial spin labeling (pCASL) MRI acquired at TEA. The pattern of GM CBF was characterized by combining an atlas-based automated segmentation of structural MRI with spatial normalization and hierarchical clustering. The effects of gestational age (GA) at birth and brain injury on the CBF pattern were investigated. We identified 4 physiologically-derived clusters of brain regions that were labeled Fronto-Temporal, Parieto-Occipital, Insular-Deep GM (DGM) and Sensorimotor, from the least to the most perfused. We demonstrated that GM perfusion was associated with GA at birth in the Fronto-Temporal and Sensorimotor clusters, positively and negatively, respectively. Moreover, the presence of periventricular leukomalacia was associated with significantly increased Fronto-Temporal GM perfusion and decreased Insular-DGM perfusion, while the presence of germinal matrix hemorrhage appeared to mildly decrease the Insular-DGM perfusion. Prematurity and prematurity-related brain injury heterogeneously affect brain perfusion. ASL MRI may, therefore, have strong potential as a noninvasive tool for the accurate stratification of individuals at risk of domain-specific impairment.

Rapid anatomical imaging of the neonatal brain using T2 -prepared 3D balanced steady-state free precession

PURPOSE

To develop a new approach to 3D gradient echo-based anatomical imaging of the neonatal brain with a substantially shorter scan time than standard 3D fast spin echo (FSE) methods, while maintaining a high SNR.

METHODS

T2 -prepration was employed immediately prior to image acquisition of 3D balanced steady-state free precession (bSSFP) with a single trajectory of center-out k-space view ordering, which requires no magnetization recovery time between imaging segments during the scan. This approach was compared with 3D FSE, 2D single-shot FSE, and product 3D bSSFP imaging in numerical simulations, plus phantom and in vivo experiments.

RESULTS

T2 -prepared 3D bSSFP generated image contrast of gray matter, white matter, and CSF very similar to that of reference T2 -weighted imaging methods, without major image artifacts. Scan time of T2 -prepared 3D bSSFP was remarkably shorter compared to 3D FSE, whereas SNR was comparable to that of 3D FSE and higher than that of 2D single-shot FSE. Specific absorption rate of T2 -prepared 3D bSSFP remained within the safety limit. Determining an optimal imaging flip angle of T2 -prepared 3D bSSFP was critical to minimizing blurring of images.

CONCLUSION

T2 -prepared 3D bSSFP offers an alternative method for anatomical imaging of the neonatal brain with dramatically reduced scan time compared to standard 3D FSE and higher SNR than 2D single-shot FSE.

A practical guide to optimize arterial spin labeling in neonates at 1.5 Tesla: what the radiologist needs to know

Arterial spin labeling magnetic resonance imaging is highly suited to the exploration of brain perfusion in neonates and has the potential to provide relevant complementary information to neuroimaging studies, with insights into neurodevelopmental outcomes. Applying this technique within the first days of life is challenging and requires specific technical adaptations. The literature on this topic is scarce and heterogeneous, especially on 1.5-T scanners, limiting widespread clinical adoption. This paper aims to describe a simple approach for arterial spin labeling in neonates, with key considerations for radiologists.

Association of Cerebral Blood Flow and Brain Tissue Relaxation Time With Neurodevelopmental Outcomes of Preterm Neonates: Multidelay Arterial Spin Labeling and Synthetic MRI Study

OBJECTIVES

Both cerebral blood flow (CBF) and brain tissue relaxation times are known to reflect maturation in the neonatal brain. However, we do not yet know if these factors are associated with neurodevelopmental outcomes. The objective of this study was to acquire CBF and relaxation time in preterm neonates, using multidelay arterial spin labeling and synthetic magnetic resonance imaging (MRI), and show their association with later neurodevelopmental outcomes.

MATERIALS AND METHODS

In this prospective study, preterm neonates were recruited, and multidelay arterial spin labeling and synthetic MRI were performed between September 2017 and December 2018. These neonates underwent the Bayley Scales of Infant Development test at 18 months of age, and both cognitive and motor outcome scores were measured. Transit time-corrected CBF and T1 and T2 relaxation time values were measured for different brain regions. The measured values were correlated with gestational age (GA) at birth and corrected GA at the MRI scan. Simple and multiple linear regression analyses were performed for the measured values and neurodevelopmental outcome scores.

RESULTS

Forty-nine neonates (median [interquartile range] GA, 30 [2] weeks, 209 [17] days; 28 boys) underwent MRI scans at or near term-equivalent age (median [interquartile range] corrected GA, 37 [2] weeks, 258 [14] days). Transit time-corrected CBF (coefficient, 0.31-0.59) and relaxation time (coefficient, -0.39 to -0.86) values showed significant correlation with corrected GA but not with GA. After controlling for GA, the frontal white matter CBF in preterm neonates showed a negative relationship with cognitive outcome scores (β = -0.97; P = 0.029). Frontal white matter T1 relaxation times showed a positive relationship with cognitive outcome scores (β = 0.03; P = 0.025) after controlling for GA.

CONCLUSIONS

Higher CBF values and lower T1 relaxation times in frontal white matter were associated with poorer cognitive outcomes. As quantitative neuroimaging markers, CBF and relaxation times may help predict neurodevelopmental outcomes in preterm neonates.

Change and clinical significance of serum cortisol, BNP, and PGE-2 levels in premature infants with patent ductus arteriosus

BACKGROUND

To analyze the change and clinical significance of cortisol, B-type brain natriuretic peptide (BNP), and prostacyclin-2 (PGE-2) levels in premature infants with patent ductus arteriosus (PDA).

METHODS

A total of 67 cases of premature infants admitted to our hospital from January 2018 to April 2020 were included, all of whom developed PDA (PDA group). According to the presence or absence of symptoms, they were divided into the symptomatic group (28 cases) and the asymptomatic group (39 cases). In addition, 62 premature infants without PDA who were born in our hospital during the same period were selected as the control group. The expression levels of cortisol, BNP, and PGE-2 in infants in different groups and between infants with symptoms and without symptoms were analyzed, along with the risk factors leading to PDA in preterm infants. The value of cortisol, BNP, and PGE-2 in the diagnosis of PDA in premature infants was also analyzed.

RESULTS

Compared with the control group, cortisol in the PDA group was significantly decreased (P<0.05), while the levels of BNP and PGE-2 were significantly increased (P<0.05). The cortisol level in the asymptomatic group was significantly higher than that in the symptomatic group, while the levels of BNP and PGE-2 were opposite, and the differences were statistically significant (P<0.05). Logistic regression analysis showed that birth weight <1,200 g, decreased cortisol, increased BNP, and increased PGE-2 were independent risk factors leading to PDA in preterm infants, and the differences were statistically significant (P<0.05). Receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of cortisol+BNP+PGE-2 in the diagnosis of PDA in premature infants were 75.60% and 73.10%, respectively. The area under the curve (AUC) value was 0.759 (95% CI: 0.611-0.859), which was significantly higher than the AUC values of the 3 tests alone (P<0.05).

CONCLUSIONS

The expression of cortisol decreased in premature infants with PDA, while the levels of BNP and PGE-2 significantly increased. Dynamic detection of the changes in these levels can provide an important reference for the early diagnosis of PDA and for the assessment of disease progression.