Cranial ultrasound assessment of gestational age in low birthweight infants

PDFF-CNN: An attention-guided dynamic multi-orientation feature fusion method for gestational age prediction on imbalanced fetal brain MRI dataset

BACKGROUND

Fetal brain magnetic resonance imaging (MRI)-based gestational age prediction has been widely used to characterize normal fetal brain development and diagnose congenital brain malformations.

PURPOSE

The uncertainty of fetal position and external interference leads to variable localization and direction of the fetal brain. In addition, pregnant women typically concentrate on receiving MRI scans during the fetal anomaly scanning week, leading to an imbalanced distribution of fetal brain MRI data. The above-mentioned problems pose great challenges for deep learning-based fetal brain MRI gestational age prediction.

METHODS

In this study, a pyramid squeeze attention (PSA)-guided dynamic feature fusion CNN (PDFF-CNN) is proposed to robustly predict gestational ages from fetal brain MRI images on an imbalanced dataset. PDFF-CNN contains four components: transformation module, feature extraction module, dynamic feature fusion module, and balanced mean square error (MSE) loss. The transformation and feature extraction modules are employed by using the PSA to learn multiscale and multi-orientation feature representations in a parallel weight-sharing Siamese network. The dynamic feature fusion module automatically learns the weights of feature vectors generated in the feature extraction module to dynamically fuse multiscale and multi-orientation brain sulci and gyri features. Considering the fact of the imbalanced dataset, the balanced MSE loss is used to mitigate the negative impact of imbalanced data distribution on gestational age prediction performance.

RESULTS

Evaluated on an imbalanced fetal brain MRI dataset of 1327 routine clinical T2-weighted MRI images from 157 subjects, PDFF-CNN achieved promising gestational age prediction performance with an overall mean absolute error of 0.848 weeks and anR 2 $R^2$ of 0.904. Furthermore, the attention activation maps of PDFF-CNN were derived, which revealed regional features that contributed to gestational age prediction at each gestational stage.

CONCLUSIONS

These results suggest that the proposed PDFF-CNN might have broad clinical applicability in guiding treatment interventions and delivery planning, which has the potential to be helpful with prenatal diagnosis.

Development of an Ultrasound Scoring System to Describe Brain Maturation in Preterm Infants

BACKGROUND AND PURPOSE

Cerebral maturation in preterm infants predominantly occurs postnatally, necessitating the development of objective bedside markers to monitor this process. This study aimed to develop a straightforward objective Ultrasound Score of Brain Development to assess cortical development in preterm infants.

MATERIALS AND METHODS

A total of 344 serial ultrasound examinations from 94 preterm infants born at ≤ 32 weeks of gestation were analyzed to identify brain structures suitable for a scoring system.

RESULTS

Among 11 candidate structures, 3 cerebral landmarks were selected due to their correlation with gestational age: the interopercular opening (P < .001), the height of the insular cortex (P < .001), and the depth of the cingulate sulcus (P < .001). These structures can be easily visualized in a single midcoronal view in the plane through the third ventricle and the foramina of Monro. A score point from 0 to 2 was assigned to each measurement, culminating in a total score ranging from 0 to 6. The Ultrasound Score of Brain Development correlated significantly with gestational age (P < .001).

CONCLUSIONS

The proposed Ultrasound Score of Brain Development has the potential for application as an objective indicator of brain maturation in correlation with gestational age, circumventing the need to rely on individual growth trajectories and percentiles for each specific structure.

Changes in structural brain development after selective fetal growth restriction in monochorionic twins

OBJECTIVES

Fetal growth restriction (FGR) may alter brain development permanently, resulting in lifelong structural and functional changes. However, in studies addressing this research question, FGR singletons have been compared primarily to matched appropriately grown singletons, a design which is inherently biased by differences in genetic and maternal factors. To overcome these limitations, we conducted a within-pair comparison of neonatal structural cerebral ultrasound measurements in monochorionic twin pairs with selective FGR (sFGR).

METHODS

Structural cerebral measurements on neonatal cerebral ultrasound were compared between the smaller and larger twins of monochorionic twin pairs with sFGR, defined as a birth-weight discordance (BWD) ≥ 20%, born in our center between 2010 and 2020. Measurements from each twin pair were also compared with those of an appropriately grown singleton, matched according to sex and gestational age at birth.

RESULTS

Included were 58 twin pairs with sFGR, with a median gestational age at birth of 31.7 (interquartile range, 29.9-33.8) weeks and a median birth weight of 1155 g for the smaller twin and 1725 g for the larger twin (median BWD, 32%). Compared with both the larger twin and the singleton, the smaller twin had significantly smaller cerebral structures (corpus callosum, vermis, cerebellum), less white/deep gray matter and smaller intracranial surface area and volume. Intracranial-volume discordance and BWD correlated significantly (R²  = 0.228, P < 0.0001). The median intracranial-volume discordance was smaller than the median BWD (19% vs 32%, P < 0.0001). After correction for intracranial volume, only one of the observed differences (biparietal diameter) remained significant for the smaller twin vs both the larger twin and the singleton.

CONCLUSIONS

In monochorionic twins with sFGR, neonatal cerebral ultrasound reveals an overall, proportional restriction in brain growth, with smaller cerebral structures, less white/deep gray matter and smaller overall brain-size parameters in the smaller twin. There was a positive linear relationship between BWD and intracranial-volume discordance, with intracranial-volume discordance being smaller than BWD. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The developing brain by trimester

Transient anatomical entities play a role in the maturation of brain regions and early functional fetal networks. At the postmenstrual age of 7 weeks, major subdivisions of the brain are visible. At the end of the embryonic period, the cortical plate covers the neopallium. The choroid plexus develops in concert with it, and the dorsal thalamus covers about half the diencephalic third ventricle surface. In addition to the fourth ventricle neuroepithelium the rhombic lips are an active neuroepithelial production site. Early reciprocal connections between the thalamus and cortex are present. The corticospinal tract has reached the pyramidal decussation, and the arteries forming the mature circle of Willis are seen. Moreover, the superior sagittal sinus has formed, and at the rostral neuropore the massa commissuralis is growing. At the viable preterm age of around 24 weeks PMA, white matter tracts are in full development. Asymmetric progenitor division permits production of neurons, subventricular zone precursors, and glial cells. Myelin is present in the ventral spinal quadrant, cuneate fascicle, and spinal motor fibers. The neopallial mantle has been separated into transient layers (stratified transitional fields) between the neuroepithelium and the cortical plate. The subplate plays an important role in organizing the structuring of the cortical plate. Commissural tracts have shaped the corpus callosum, early primary gyri are present, and opercularization has started caudally, forming the lateral fissure. Thalamic and striatal nuclei have formed, although GABAergic neurons continue to migrate into the thalamus from the corpus gangliothalamicum. Near-term PMA cerebral sublobulation is active. Between 24 and 32 weeks, primary sulci develop. Myelin is present in the superior cerebellar peduncle, rubrospinal tract, and inferior olive. Germinal matrix disappears from the telencephalon, except for the GABAergic frontal cortical subventricular neuroepithelium.

Development of cerebral sulci and gyri in ferrets (Mustela putorius)

The present study aimed to clarify sulcation and gyration patterns in the developing cerebrum of ferrets. While the brain weight and fronto-occipital length of the cerebral hemisphere reached a plateau by postnatal day (PD) 42, the cerebral width reached a plateau at the rostral region by PD 21, and subsequently at the caudal region by PD 42. The ferret cerebrum already showed a convoluted surface with indentations of coronal and rostral suprasylvian sulci on PD 4. The presylvian and cruciate sulci emerged by PD 10, resulting in convolutions of gyri in the rostral half of the cerebrum. The caudal half of the cerebrum was infolded by the emergence of the pseudosylvian sulcus and the rhinal fissure by PD 10, and the caudal suprasylvian and lateral sulci by PD 21. The emergence of those sulci allowed a gyration in the caudal half of the cerebrum. Sexual differences in sulcation were detected by a more distinct convolution of the visual cortex in males than in females on PD 90. Those results, therefore, suggest that the ferret cerebrum experiences cortical maturation with sulcation and gyration in a rostrocaudal gradient manner. The present paper provides neuroanatomic references for normal development of cerebral sulci and gyri in both sexes of ferrets.

[Correlation between neurological finding and gestational maturity of newborns determined by neurosonography]

INTRODUCTION

Maturity is a complex functional condition influenced especially by the development of the vital functions of a fetus, primarily by the degree of the development of its central nervous system. The aim of this investigation was to establish the gestational maturity of the nervous system by neurosonography and neurological status.

MATERIAL AND METHODS

The parameter of the neurological maturity, compared in this research are a neurological status and the degree of girification established by the ultrasound.

RESULTS

All the coefficients of correlation between the gestation age determined by the ultrasound and the establishing of the gestation based on the neurological findings show a statistically significant correlation for p < 0.01. Of particular parametres of the neurological evaluation , the most appropriate ones appeared to be reflexes (the reflex of crossed extension, Moro reflex and the reflex of the main points), then volar flexion of a hand and the poplietal corner as the indicator of the passive tonus, whereas within the area of the evaluation of the active tonus, the motility was the most valid for establishing the maturity of a neonatal. The lowest coefficients of the correlations were in the automatic walk and the active tonus of the neck flexor, which are the ones of the most common neurological indicators of hypoxic ischemic encephalopathy of a neonatal.

CONCLUSIONS

Bearing in mind that the premature babies are a risky group for existence of perinatal brain damages, we believe the neurosonographic establishing of the gestation age to be a precise and comfortable indicator of the maturity of the nervous system.

Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis). II. Gross observation of the medial surface

This study aimed to clarify chronological sequences of the appearances of sulci and gyri on the medial cerebral surface and its relation to the regional development of the cerebrum in cynomolgus monkeys. The lengths of cingulate and calcarine sulci were measured, and the ratios of these lengths to fronto-occipital length were estimated as indices of the size of the "frontoparietal" and "occipital" regions, respectively. The relative length of cingulate sulcus showed a biphasic increase: a slow phase from EDs 100 to 110, and a rapid phase from EDs 110 to 130. The gyri in the "frontoparietal region" were convoluted in the limbic cortex during the initial slow phase and in the neocortical region during the rapid phase. The relative length of calcarine sulcus lineally increased between EDs 90 and 130, and the gyri in the "occipital region" generated in a dorso-ventral manner: the gyrus convolutions occurred first in the "phylogenetically older" striate and dorsal extrastriate cortices, and then in the "phylogenetically newer" ventral extrastriate cortex. The results suggest that the chronological order of appearance of sulci and gyri is closely associated with the order of phylogenetical development of the cerebral cortex. The present study provides a standard reference for the development of cerebral sulci and gyri of cynomolgus monkeys together with our previous study (Fukunishi et al. Anat Embryol 211:757-764, 2006).

Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis)

This study aimed to clarify the development of sulci and gyri on the external surface of the cerebrum of cynomolgus monkeys. Sulcus formation began with the appearance of the lateral fissure on embryonic day (ED) 70, followed by delineations of four cerebral lobes by the emergence of the parietooccipital sulcus, central sulcus, and preoccipital notch on EDs 80-90. The following primary sulci were then visible until ED 120: the superior temporal sulcus on ED 90; the intraparietal sulcus, lunate sulcus, inferior occipital sulcus, and arcuate sulcus on ED 100; and the principle sulcus on ED 110; the occipitotemporal sulcus, anterior middle temporal sulcus, and superior postcentral dimple on ED 120. These sulci demarcated the superior temporal gyrus on ED 90, the precentral gyrus, supramarginal gyrus, and angular gyrus on ED 100, and the inferior and middle temporal gyri, postocentral gyrus, superior parietal lobule, superior, middle and inferior frontal gyri, and inferior occipital gyrus on ED 120. Except for the intermediate and lateral orbitofrontal sulci, the sulci that appeared on ED 130 and thereafter were not related to the gyrus demarcations. Intriguingly, the brain markedly gained weight on EDs 100 and 120, corresponding to the embryonic ages when almost all gyri were visible. The results suggest that a rapid growth of the cerebrum involves convolutions of the gyri by a regular sequence of the sulcus formation in cynomolgus monkeys. This study further provides a standard of reference for normal development in the cerebral cortical morphology of cynomolgus monkeys.

Repères échographiques de gyration cérébrale fœtale normale

PURPOSE

Define normal sulcation patterns and their chronological order of appearance on transabdominal ultrasound by comparing them with brain maturation references available in fetopathological studies and MRI findings.

PATIENTS AND METHODS

By means of a prospective study, 158 normal fetal brains aged 21 to 34 gestational weeks have been analyzed with standardized data by transabdominal ultrasound in eleven different views using axial, coronal and sagittal orientation.

RESULTS

The sequential development of cerebral sulci has been described according to the gestational age. This chronology was consistent with anatomo-pathologic references presenting a mean late period of one week and with MRI but without any late period. This study is available on the following website:

CONCLUSION

This ultrasound study provides accurate landmarks and imaging features of normal fetal brain sulcation. The analysis and the knowledge of this sulcation provide better understanding of the brain cortex maturation and may be helpful in diagnosing brain diseases.

Superfetation as a cause of growth discordance in a multiple pregnancy

A triplet pregnancy is described, in which the diagnosis of in utero growth restriction is questioned after postnatal suspicion of superfetation, by using neurosonography and ophthalmic examination to aid gestational age assessment.

Assessment of gestational age and neuromaturation

Neuromaturation is the functional development of the central nervous system (CNS). It is by its very nature a dynamic process, a continuous interaction between the genome and first the intrauterine environment, then the extrauterine environment. Understanding neuromaturation and being able to measure it is fundamental to infant neurodevelopmental assessment. Fetal and preterm neuromaturation has become easier to observe with the advent of prenatal ultrasonography and neonatal intensive care units. A number of measures of degree of fetal maturation have been developed and used to estimate gestational age (GA) at birth. The most reliable measures of GA are prenatal measures, especially from the first trimester. Postnatal GA measurements tend to be least accurate at the extremes of gestation, that is, in extremely preterm and post-term infants. Observations of measures of neuromaturation in infants born to mothers with pregnancy complications, including intrauterine growth restriction, multiple gestation, and chronic hypertension, have led to the discovery that stressed pregnancies may accelerate fetal pulmonary and CNS maturation. This acceleration of neuromaturation does not occur before 30 weeks' gestation and has a cost with respect to cognitive limitations manifested in childhood. The ability to measure fetal and preterm neuromaturation provides an assessment of neurodevelopmental progress that can be used to reassure parents or identify at risk infants who would benefit from limited comprehensive follow-up and early intervention services. In addition, measures of neuromaturation have the potential to provide insight into mechanisms of CNS injury and recovery, much-needed early feedback in intervention or treatment trials and a measure of early CNS function for research into the relationships between CNS structure and function.

The role of MRI in the evaluation of the fetal brain with an emphasis on biometry, gyration and parenchyma

The aim of this review is to emphasize the role of fetal MR in the evaluation of the supratentorial space. The advantages of MRI compared to US are stressed in three fields of application: cerebral biometry, sulcation and cerebral parenchyma. In each field, normal data are displayed and MR applications with patterns of the main pathologies are briefly described.

Fetal MRI: normal gestational landmarks for cerebral biometry, gyration and myelination

PURPOSE

Up until the last 10 years, normal cerebral gestational landmarks were assessed by ultrasonographic and fetopathologic studies. The purpose of this paper is to display the possibilities provided by fetal MRI in the evaluation of fetal cerebral biometry, normal sulcation and myelination.

METHODS

Two hundred and twenty-five fetuses (with a normal brain) were studied prospectively using a standardised method. The gestational age ranged from 22 to 38 weeks. The main data concerning biometry of various cerebral structures at those terms are given.

DISCUSSION

In contrast to ultrasound, MRI allows measurements of brain (and not skull), which are available independently of the position of the fetal head. The timing of the appearance of the different sulci is also available using MRI. It is considered to be a good marker of fetal brain maturation. The biochemical modifications contemporary to myelination make it possible to evaluate this phenomenon in the fetal brain using MRI.

Three-dimensional (3D) ultrasound--a useful imaging technique in the assessment of neonatal brain

Clinical application of ultrasound began about fifty years ago. From one-dimensional A-mode, through two-dimensional real time and Doppler examinations, a new era in clinical ultrasonography then began in the late eighties. Development of computer technology enabled introduction of 3D ultrasonography into clinical practice. In obstetrics ultrasound revolutionized fetal follow-up, but it was as important for the detection of intracranial pathology during the neonatal period and infancy. Two-dimensional real time ultrasonography was [table: see text] an exciting method that changed our understanding of the prevalence and pathophysiology of brain pathology in premature and term infants. Will application of 3D ultrasonography bring any substantial improvement to neuroimaging diagnostics in the newborn period? This article attempts to find the answer to this question, despite the limitations set by the short period of application of 3D neurosonography in neonates. The advantages of 3D brain ultrasonography application in neonates are: quicker and observer independent data acquisition, the possibility of off-line data analysis, projection of 3D data on a 2D plane with volumetric, color and power Doppler studies. Unavailability of equipment is the main reason why 3D ultrasonography was performed in only half of the newborns in whom it was indicated. Cost of equipment prevents introduction of 3D as a standard diagnostic procedure in neonates, although its diagnostic value is indisputable.

Fetal cerebral cortex: normal gestational landmarks identified using prenatal MR imaging

BACKGROUND AND PURPOSE

Few investigators have analyzed the MR imaging patterns of fetal gyration. Our purpose was to establish, with a large prospective series, the normal sulcation landmarks according to gestational age by using in utero MR imaging and to correlate our findings with established neuroanatomic timetables.

METHODS

A standardized fetal cerebral MR examination was performed in 173 normal fetuses at 22 to 38 weeks' gestation. Eight T1- and T2-weighted coronal, axial, and sagittal slices were obtained for each fetus and systematically analyzed. The sequential development of the different fissures and sulci of the cerebral cortex with respect to gestational age were tabulated.

RESULTS

Sulcation of the medial, lateral, and inferior surfaces of the brain was depicted, and a timetable for the MR depiction of the primary and secondary sulci was established for the 22- to 38-week gestational period. This timetable was in good agreement with the neuroanatomic standards of reference, with a mean lag time of 1 week.

CONCLUSION

This analysis of fetal brain sulcation in a large series of fetuses contributes to a better understanding of the maturation of the fetal cortex on MR imaging studies. It furthermore provides a standard of reference that can be used to assess the normality of fetal sulcation and to diagnose gyrational abnormalities with prenatal MR imaging.

Cortical maturation in normal and abnormal fetuses as assessed with prenatal MR imaging

PURPOSE

To establish the appearance of normal fetal cortical development in utero and compare it with the appearance of abnormal cortical development.

MATERIALS AND METHODS

Magnetic resonance (MR) images of the brain in 53 normal and 40 abnormal fetuses at 14-38 weeks gestational age (GA) were reviewed. The GAs at the time of MR imaging visualization of the fissures or sulci were compared with the GA guidelines based on neuroanatomic studies.

RESULTS

In normal fetuses, the sulcation landmarks appeared on MR images in the order predicted by using anatomic studies, with a 0-8-week lag in the MR imaging visualization of the sulci compared with the reported time of visualization of the sulci in anatomic specimens. When landmarks were grouped by range of GAs, the expected MR imaging sulcation landmarks in the group with younger GAs than the actual GA were seen in 50 of 53 (94%) normal fetuses, in five of nine fetuses (56%, P < .05) with isolated mild ventriculomegaly, and in 24 of 31 fetuses (77%, P < .05) with other CNS anomalies.

CONCLUSION

Normal fetal cortical maturation at MR imaging follows a predictable course that is slightly delayed compared with that described in neuroanatomic specimens. This maturation is often further delayed in fetuses with CNS abnormalities.

Cerebellar vermis measurement at cranial sonography for assessing gestational age in the newborn weighing less than 2000 grams

Prognosis of the very low birth weight infant depends more on gestational age than birth weight, but clinical assessment of gestational age of very low birth weight infants is inaccurate. We wished to determine how well cerebellar vermis dimensions might predict gestational age in infants of birth weight less than 2000 g. We obtained suitable midline sagittal images of the cerebellar vermis at cranial sonography, performed via the anterior or posterior fontanelle, in 41 infants, from the regional neonatal intensive care unit whose gestational age was known. We measured the cerebellar vermis area and diameter on the hard-copy image provided the margins of the vermis were clearly visible, the cerebellar tonsils were excluded from the image, and the anterior and posterior divisions of the corpus medullare were visible on the image. Vermis diameter was measured from the base of the fourth ventricle to the junction of folium and tuber vermis. Vermis area was calculated using a stereological method using a test system of regularly spaced points randomly placed over a magnified image of the cerebellar vermis. We generated regression equations for estimating gestational age using combinations of birth weight, vermis area, or vermis diameter for the 26 infants with birth weight of less than 2000 g for whom the cerebellar vermis measurements were obtained within one week of birth. Vermis area and diameter correlated very highly. They both can be used for predicting gestational age. The addition of either vermis area or diameter to birth weight improves accuracy of gestational age assessment. If birth weight was presumed to be unknown, cerebellar vermis area or diameter allow prediction of gestational age to within +/- 1.3 weeks (1 standard error) or +/- 2.5 weeks, using a 95% prediction interval. If the same method of reporting is applied to the New Ballard Score, the New Ballard Score predicts gestational age +/- 1.7 weeks (1 standard error) or +/- 3.4 weeks, using a 95% prediction interval.

Neural migration disorders studied by cerebral ultrasound and colour Doppler flow imaging

Cerebral ultrasound and colour Doppler flow imaging (CDFI) were used to diagnose a wide spectrum of anomalies of cell migration (17 patients): presumed lissencephaly (n = 12); schizencephaly of both fused (n = 2) and open lips (n = 2); hemimegalencephaly (n = 1); and subependymal type grey matter heterotopia (n = 12). The patients with grey matter heterotopia had irregular ventricular margins (n = 10), periventricular hyperechogenic bands (n = 12), and/or periventricular hyperechogenic nodules (n = 7). Some patients had more than one type of migration disorder as well as other central nervous system malformations. Cerebral ultrasound diagnoses were confirmed by magnetic resonance imaging (MRI) or necropsy. It is concluded that colour Doppler flow imaging is a worthwhile addition to the assessment of brain surface anomalies.

Assessment of gestational age in newborns by neurosonography

Current methods for estimating gestational age using clinical parameters can be inaccurate in prematurity. A simplified ultrasonographic system, based on cerebral sulcal development, for clinically determining fetal maturation in newborns was developed and studied in 148 newborns (92 appropriate-for-gestational-age, 54 small-for-gestational-age and 2 large-for-gestational age). This ultrasonographic sulcal method correlates better with the gestational age by dates than by the Dubowitz scoring system in the neonates less than 30 weeks' gestation. There are significant correlations between gestational age assessed by dates and by sonographic sulcal age in both appropriate-for-gestational-age (R = 0.91, P less than 0.001) and small-for-gestational-age newborns (R = 0.92, P less than 0.001). Maternal hypertension during pregnancy is a significant risk factor associated with accelerated fetal cerebral maturation in 12 neonates. Although overestimate of gestational age may occur in neonates born to mothers with hypertension, cranial ultrasonography is an accurate and convenient method of estimating gestational age in neonates.

Sonographic cerebral sulcal development in premature newborns

Cranial ultrasound examinations with 5.0 and 7.5 mHZ transducers during the first 3 days of life on 60 appropriate-for-date newborns with gestational age 24-36 wks were performed to determine the sulcal development of cerebral cortex in utero. The sulci appeared and developed in sequence. All the calcarine fissure and most of the anterior part of cingulate sulcus began to appear before 28 wks. At 28-31 wks all the whole cingulate sulcus and postrolandic sulcus, and most of the inferior temporal sulcus and covering of insula were ready to be observed. All of the insular sulci and tertiary sulci, and most of the secondary sulci from cingulate sulcus appeared after 31 wks. As cortical organization advanced, the discrepancy in the age of sulcal appearance between neuroanatomic and ultrasonic studies became less striking by the last trimester. Ultrasonic examination of the cortical sulci provides a noninvasive and convenient means to stage the normal cerebral maturation, and can be helpful in the detection of pathology in sulcal formations.