Fetal cerebellar volume and symmetry on 3-d ultrasound: volume measurement with multiplanar and vocal techniques

Fetal brain growth and infant autistic traits

BACKGROUND

Structural differences exist in the brains of autistic individuals. To date only a few studies have explored the relationship between fetal brain growth and later infant autistic traits, and some have used fetal head circumference (HC) as a proxy for brain development. These findings have been inconsistent. Here we investigate whether fetal subregional brain measurements correlate with autistic traits in toddlers.

METHODS

A total of 219 singleton pregnancies (104 males and 115 females) were recruited at the Rosie Hospital, Cambridge, UK. 2D ultrasound was performed at 12-, 20- and between 26 and 30 weeks of pregnancy, measuring head circumference (HC), ventricular atrium (VA) and transcerebellar diameter (TCD). A total of 179 infants were followed up at 18-20 months of age and completed the quantitative checklist for autism in toddlers (Q-CHAT) to measure autistic traits.

RESULTS

Q-CHAT scores at 18-20 months of age were positively associated with TCD size at 20 weeks and with HC at 28 weeks, in univariate analyses, and in multiple regression models which controlled for sex, maternal age and birth weight.

LIMITATIONS

Due to the nature and location of the study, ascertainment bias could also have contributed to the recruitment of volunteer mothers with a higher than typical range of autistic traits and/or with a significant interest in the neurodevelopment of their children.

CONCLUSION

Prenatal brain growth is associated with toddler autistic traits and this can be ascertained via ultrasound starting at 20 weeks gestation.

Ultrasonographic Estimation of Ventricular Volume in Infants Born Preterm with Posthemorrhagic Ventricular Dilatation: A Nested Substudy of the Randomized Controlled Early Versus Late Ventricular Intervention Study (ELVIS) Trial

OBJECTIVE

To study the potential role of ventricular volume (VV) estimation in the management of posthemorrhagic ventricular dilatation related to the need for ventriculoperitoneal (VP)-shunt insertion and 2-year neurodevelopmental outcome in infants born preterm.

STUDY DESIGN

We included 59 patients from the Early vs Late Ventricular Intervention Study from 4 participating centers. VV was manually segmented in 209 3-dimensional ultrasound scans and estimated from 2-dimensional ultrasound linear measurements in a total of 1226 ultrasounds. We studied the association of both linear measurements and VV to the need for VP shunt and 2-year neurodevelopmental outcome in the overall cohort and in the 29 infants who needed insertion of a reservoir. We used general estimating equations to account for repeated measures per individual.

RESULTS

Maximum pre-reservoir VV (β coefficient = 0.185, P = .0001) and gestational age at birth (β = -0.338; P = .0001) were related to the need for VP shunt. The estimated optimal single VV measurement cut point of 17 cm3 correctly classified 79.31% with an area under the curve of 0.76 (CI 95% 0.74-0.79). Maximum VV (β = 0.027; P = .012) together with VP shunt insertion (β = 3.773; P = .007) and gestational age (β = -0.273; P = .0001) were related to cognitive outcome at 2 years. Maximum ventricular index and anterior horn width before reservoir insertion were independently associated with the need of VP shunt and the proposed threshold groups in the Early vs Late Ventricular Intervention Study trial were associated with long-term outcome.

CONCLUSIONS

Pre-reservoir VV measurements were associated with the need for VP-shunt insertion and 2-year cognitive outcome among infants born preterm with posthemorrhagic ventricular dilatation.

TRIAL REGISTRATION

ISRCTN43171322.

Automatic measurements of fetal intracranial volume from 3D ultrasound scans

Three-dimensional fetal ultrasound is commonly used to study the volumetric development of brain structures. To date, only a limited number of automatic procedures for delineating the intracranial volume exist. Hence, intracranial volume measurements from three-dimensional ultrasound images are predominantly performed manually. Here, we present and validate an automated tool to extract the intracranial volume from three-dimensional fetal ultrasound scans. The procedure is based on the registration of a brain model to a subject brain. The intracranial volume of the subject is measured by applying the inverse of the final transformation to an intracranial mask of the brain model. The automatic measurements showed a high correlation with manual delineation of the same subjects at two gestational ages, namely, around 20 and 30 weeks (linear fitting R2(20 weeks) = 0.88, R2(30 weeks) = 0.77; Intraclass Correlation Coefficients: 20 weeks=0.94, 30 weeks = 0.84). Overall, the automatic intracranial volumes were larger than the manually delineated ones (84 ± 16 vs. 76 ± 15 cm3; and 274 ± 35 vs. 237 ± 28 cm3), probably due to differences in cerebellum delineation. Notably, the automated measurements reproduced both the non-linear pattern of fetal brain growth and the increased inter-subject variability for older fetuses. By contrast, there was some disagreement between the manual and automatic delineation concerning the size of sexual dimorphism differences. The method presented here provides a relatively efficient way to delineate volumes of fetal brain structures like the intracranial volume automatically. It can be used as a research tool to investigate these structures in large cohorts, which will ultimately aid in understanding fetal structural human brain development.

Association between maternal oxygenation and brain growth in fetuses with left-sided cardiac obstructive lesions

OBJECTIVE

Impaired brain growth has been observed in fetuses with left-sided obstructive lesions (LSOL). Maternal oxygenation (MO) can alter fetal cerebral oxygenation and vascular reactivity. Our aim was to observe whether brain growth improves during MO in fetuses with LSOL.

METHODS

Forty-six fetuses with LSOL and 23 control fetuses were enrolled in this prospective longitudinal study. Fetuses with LSOL were subgrouped into those with MO (LSOL-MO, n = 23) and those without MO (LSOL-nMO, n = 23). Fetal head circumference (HC) and total intracranial volume (TIV) were evaluated serially at 4-week intervals. Brain biometry and growth were analyzed using linear mixed models adjusted for gestational age and sex. Spearman's correlation coefficients were calculated to identify baseline characteristics predictive of brain growth in the LSOL-MO group.

RESULTS

Duration of MO therapy had significant interaction effects on cerebral biometry in fetuses with LSOL. TIV increased more rapidly after 8 weeks of oxygen exposure and HC was larger after 16 weeks of oxygen exposure in the LSOL-MO group compared with the LSOL-nMO group (P < 0.001). The change in TIV at the final time- point relative to the initial timepoint in the LSOL-MO group correlated negatively with the baseline pulsatility index of the middle cerebral artery (r = -0.58, P = 0.003) and baseline myocardial performance index of the left ventricle (r = -0.68, P < 0.001).

CONCLUSIONS

TIV and HC increased faster in fetuses with LSOL which had MO compared with those that did not. Lower cerebral vascular resistance and preserved left heart function at baseline may predict greater cerebral biometric growth during MO. Additional research, including larger serial studies, is needed to confirm these preliminary findings and evaluate the clinical application of MO in this population. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Subcortical Segmentation of the Fetal Brain in 3D Ultrasound using Deep Learning

The quantification of subcortical volume development from 3D fetal ultrasound can provide important diagnostic information during pregnancy monitoring. However, manual segmentation of subcortical structures in ultrasound volumes is time-consuming and challenging due to low soft tissue contrast, speckle and shadowing artifacts. For this reason, we developed a convolutional neural network (CNN) for the automated segmentation of the choroid plexus (CP), lateral posterior ventricle horns (LPVH), cavum septum pellucidum et vergae (CSPV), and cerebellum (CB) from 3D ultrasound. As ground-truth labels are scarce and expensive to obtain, we applied few-shot learning, in which only a small number of manual annotations (n = 9) are used to train a CNN. We compared training a CNN with only a few individually annotated volumes versus many weakly labelled volumes obtained from atlas-based segmentations. This showed that segmentation performance close to intra-observer variability can be obtained with only a handful of manual annotations. Finally, the trained models were applied to a large number (n = 278) of ultrasound image volumes of a diverse, healthy population, obtaining novel US-specific growth curves of the respective structures during the second trimester of gestation.

A methodological review of fetal neurosonographic studies: New directions in assessment of neurodevelopmental risk for mental health problems

Most mental disorders are now considered to have neurodevelopmental origins, with a growing body of research pointing to neural alterations that predate birth. However, lack of established methods for reliable investigation of fetal brain development has limited research into early neural vulnerability. Using a systematic approach and quantitative evaluation of study methodology, we review neurosonographic studies of fetal brain structure with objective quality measures. A total of 81 studies were identified. High quality studies were identified for measurement of the corpus callosum, cerebellum, vermis, ventricles and frontal cortex, with reference ranges provided to facilitate future clinical research. Fewer and lower quality studies were available for subcortical structures, prompting a need for further research to create reliable reference ranges. Development and adoption of reference ranges for fetal brain structures should facilitate future research in neurosonographic evaluation of fetal brain development and lead to a better understanding of neurodevelopmental risk and resilience processes for mental disorders.

Evaluation of the development of the posterior fossa in normal Chinese fetuses by using magnetic resonance imaging

The posterior fossa is an important brain structure containing the cerebellum, cerebral ventricle, and cistern. Early evaluation of the cerebellar structure and function may be valuable for early detection of fetal deformities. At present, no normal value for the fetal posterior fossa has been established yet. This study is aimed to investigate the development of the posterior fossa in normal Chinese fetuses by using magnetic resonance imaging (MRI).Pregnant women who need MRI scan were enrolled in our Hospital between January 2012 and December 2014. The fetal supero-inferior diameter (SID), anterio-posterior diameter (APD), cerebellar vermis area, cerebellar width (CW), cerebellar volume (CV), superior cerebellar cistern width, and cerebellomedullary cistern width were measured using MRI. Pearson's correlation analysis was used to detect the relationship between those parameters and gestational age. A regression analysis was performed for all parameters.A total of 92 participants were retrospectively enrolled finally. The results indicated SID, APD, cerebellar vermis area, CW, and CV were positively associated with gestational age, while no significant correlation was found between the superior cerebellar cistern width and cerebellomedullary cistern width and gestational age. Each equation was established.Our study demonstrated that MRI has the advantages over ultrasound imaging for prenatal evaluation of the fetal posterior fossa with multiple views. Normal value of the posterior fossa of Chinese fetuses was established in this study.

Three-dimensional volumetric study with VOCAL in normal and abnormal posterior fossa fetuses

Purpose: The aim of this study was to compare volumetric parameters in the abnormal and normal posterior fossa using the Virtual Organ Computer-aided AnaLysis (VOCAL™) technique to determine whether fetuses with an abnormal posterior fossa have different volumes.Methods: A prospective study was conducted on 17 fetuses with an abnormal posterior fossa including, Dandy Walker malformation (DWM) (n = 6), vermian hypoplasia (VH) (n = 3), mega cisterna magna (MCM) (n = 8), and 99 healthy control fetuses from 20 to 34 weeks' gestation. Measurement of the fetal cisterna magna and cerebellar volume was performed in the standard transcerebellar plane through the VOCAL™ method. To establish the correlation of volumes with gestational age, polynomial regression analysis was performed. For comparison between groups, univariate ANCOVA was performed using gestational age as a covariate. The reliability was analyzed by the intraclass correlation coefficient (ICC).Results: Cerebellar volume and cisterna magna volume were correlated with gestational age. Posterior fossa volume was significantly larger in DWM (p < .0001) and MCM (p < .0001) in comparison to the control group. In VH group, cisterna magna volume does not seem to expand (p = .298). Cerebellar volume does not seem to change in subgroups when the influence of gestational age is discarded (p = .09). The ratio of cerebellar volume to the cisterna magna volume decreases significantly in abnormal fetuses (p < .0001). Good intraobserver and interobserver reliabilities were found for both cerebellum and cisterna magna measurements.Conclusions: Volume analysis may have a role in discrimination of different posterior fossa pathologies.

Intra- and interobserver agreement for fetal cerebral measurements in 3D-ultrasonography

The aim of this study is to evaluate intra- and interobserver agreement for measurement of intracranial, cerebellar, and thalamic volume with the Virtual Organ Computer-aided AnaLysis (VOCAL) technique in three-dimensional ultrasound images, in comparison to two-dimensional measurements of these brain structures. Three-dimensional ultrasound images of the brains of 80 fetuses at 20-24 weeks' gestational age were obtained from YOUth, a Dutch prospective cohort study. Two observers performed offline measurement of the occipitofrontal diameter, intracranial volume, transcerebellar diameter, cerebellar volume, and thalamic width, area, and volume, independently. VOCAL was used for calculation of the volumes. The two-way random, single measures intraclass correlation coefficient (ICC) was used for analysis of agreement and Bland-Altman plots were configured. Intra- and interobserver agreement was almost perfect for occipitofrontal diameter (intra ICC 0.88, 95% CI 0.82-0.92; inter ICC 0.91, 95% CI 0.85-0.94), intracranial volume (intra ICC 0.96, 95% CI 0.91-0.98; inter ICC 0.97, 95% CI 0.96-0.98) and transcerebellar diameter (intra ICC 0.91, 95% CI 0.86-0.94; inter ICC 0.86, 95% CI 0.78-0.910). For cerebellar volume, the intraobserver agreement was almost perfect (0.85, 95% CI 0.76-0.90), whereas the interobserver agreement was substantial (0.75, 95% CI 0.44-0.88). Agreement was only moderate for thalamic measurements. Bland-Altman plots for the volume measurements are normally distributed with acceptable mean differences and 95% limits of agreement. The intra- and interobserver agreement of the measurement of intracranial and cerebellar volume with VOCAL was almost perfect. These measurements are therefore reliable, and can be used to investigate fetal brain development. Thalamic measurements are not reliable enough.

Prenatal cerebellar growth trajectories and the impact of periconceptional maternal and fetal factors

STUDY QUESTION

CAN WE assess human prenatal cerebellar growth from the first until the third trimester of pregnancy and create growth trajectories to investigate associations with periconceptional maternal and fetal characteristics?

SUMMARY ANSWER

Prenatal growth trajectories of the human cerebellum between 9 and 32 weeks gestational age (GA) were created using three-dimensional ultrasound (3D-US) and show negative associations with pre-pregnancy and early first trimester BMI calculated from self-reported and standardized measured weight and height, respectively.

WHAT IS KNOWN ALREADY

The cerebellum is essential for normal neurodevelopment and abnormal cerebellar development has been associated with neurodevelopmental impairments and psychiatric diseases. Cerebellar development is particularly susceptible to exposures during the prenatal period, including maternal folate status, smoking habit and alcohol consumption.

STUDY DESIGN, SIZE, DURATION

From 2013 until 2015, we included 182 singleton pregnancies during the first trimester as a subgroup in a prospective periconception cohort with follow-up until birth. For the statistical analyses, we selected 166 pregnancies ending in live born infants without congenital malformations.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We measured transcerebellar diameter (TCD) at 9, 11, 22, 26 and 32 weeks GA on ultrasound scans. Growth rates were calculated and growth trajectories of the cerebellum were created. Linear mixed models were used to estimate associations between cerebellar growth and maternal age, parity, mode of conception, geographic origin, pre-pregnancy and first trimester BMI, periconceptional smoking, alcohol consumption, timing of folic acid supplement initiation and fetal gender.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 166 pregnancies provided 652 (87%) ultrasound images eligible for TCD measurements. Cerebellar growth rates increased with advancing GA being 0.1691 mm/day in the first trimester, 0.2336 mm/day in the second trimester and 0.2702 mm/day in the third trimester. Pre-pregnancy BMI, calculated from self-reported body weight and height, was significantly associated with decreased cerebellar growth trajectories (β = -0.0331 mm, 95% CI = -0.0638; -0.0024, P = 0.035). A similar association was found between cerebellar growth trajectories and first trimester BMI, calculated from standardized measurements of body weight and height (β = -0.0325, 95% CI = -0.0642; -0.0008, P = 0.045, respectively).

LIMITATIONS, REASONS FOR CAUTION

As the study population largely consisted of tertiary hospital patients, external validity should be studied in the general population. Whether small differences in prenatal cerebellar growth due to a higher pre-pregnancy and first trimester BMI have consequences for neurodevelopmental outcome needs further investigation.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings further substantiate previous evidence for the detrimental impact of a higher maternal BMI on neurodevelopmental health of offspring in later life.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Department of Obstetrics and Gynecology, Erasmus MC University Medical Centre and Sophia Children's Hospital Fund, Rotterdam, The Netherlands (SSWO grant number 644). No competing interests are declared.

Ultrasound lineal measurements predict ventricular volume in posthaemorrhagic ventricular dilatation in preterm infants

AIM

Posthaemorrhagic ventricular dilatation (PHVD) is monitored by conventional two-dimensional ultrasound (2DUS). The aims of this study were to determine the volume of the lateral ventricles using three-dimensional ultrasound (3DUS) in preterm infants with PHVD and to evaluate the relationship between volume and linear measurements.

METHODS

Serial 2DUSs and 3DUSs were performed on preterm infants with PHVD admitted to the neonatal intensive care unit at Puerta del Mar Hospital, Cádiz, Spain, from January 2013 to December 2014. The ventricular index, anterior horn width and thalamo-occipital distance were used as ventricular lineal measurements. Ventricular volume was calculated offline.

RESULTS

Serial ultrasounds from seven preterm infants were measured. Each linear measurement was significantly associated with volume, and an equation was obtained through a significant multilevel mixed-effects lineal regression model: ventricular volume (cm³ ) = -11.02 + 0.668*VI + 0.817*AHW + 0.256*TOD. Intra-observer and interobserver agreement was excellent with an intraclass correlation coefficient of 0.99.

CONCLUSION

Lateral ventricular volumes of preterm infants with PHVD could be reliably determined using 3DUS. Ventricular volume could be accurately estimated using three lineal measurements. More studies are needed to address the importance of volume determination in PHVD.

True Reproducibility of UltraSound Techniques (TRUST): systematic review of reliability studies in obstetrics and gynecology

OBJECTIVES

To examine the quality of methods used and the accuracy of the interpretation of agreement in existing studies that examine the reliability of ultrasound measurements and judgments in obstetrics and gynecology.

METHODS

A systematic search of MEDLINE was performed on 25 March 2014, looking for studies that examined the reliability of ultrasound measurements and judgments in obstetrics and gynecology with evaluation of concordance (CCC) or intraclass (ICC) correlation coefficients or kappa as a main objective.

RESULTS

Seven hundred and thirty-three records were examined on the basis of their title and abstract, of which 141 full-text articles were examined completely for eligibility. We excluded 29 studies because they did not report CCC/ICC/kappa, leaving 112 studies that were included in our analysis. Two studies reported both ICC and kappa and were counted twice, therefore, the number used as the denominator in the analyses was 114. Only 16/114 (14.0%) studies were considered to be well designed (independent acquisition and blinded analysis) and to have interpreted the results properly. Most errors occurring in the studies are likely to overestimate the reliability of the method examined.

CONCLUSIONS

The vast majority of published studies examined had important flaws in design, interpretation and/or reporting. Such limitations are important to identify as they might create false confidence in the existing measurements and judgments, jeopardizing clinical practice and future research. Specific guidelines aimed at improving the quality of reproducibility studies that examine ultrasound methods should be encouraged.

Role of 3-D ultrasound in clinical obstetric practice: evolution over 20 years

The use of 3-D ultrasound in obstetrics has undergone dramatic development over the past 20 years. Since the first publications on this application in clinical practice, several 3-D ultrasound techniques and rendering modes have been proposed and applied to the study of fetal brain, face and cardiac anatomy. In addition, 3-D ultrasound has improved calculations of the volume of fetal organs and limbs and estimations of fetal birth weight. And furthermore, angiographic patterns of fetal organs and the placenta have been assessed using 3-D power Doppler ultrasound quantification. In this review, we aim to summarize current evidence on the clinical relevance of these methodologies and their application in obstetric practice.

Automatic localization of the fetal cerebellum on 3D ultrasound volumes

PURPOSE

Assessment of the fetal cerebellar volume on 3D ultrasound data sets is very important in the clinical evaluation of the fetal growth and health. However, the irregular shape of the cerebellum and the strong artifacts of ultrasound images complicate the segmentation without manual intervention. In this paper, the authors propose an approach to locate the cerebellum automatically, which is considered as a prework of the segmentation.

METHODS

The authors present a weighted Hough transform and a constrained randomized Hough transform to detect the fetal brain midline and the skull, respectively. By combining the location information of these two structures with local image features, a constrained probabilistic boosting tree is then proposed to search the cerebellum.

RESULTS

This algorithm was tested on ultrasound volumes of the fetal head with the gestational age ranging from 20 to 33 weeks. Compared with manual measurements, this algorithm obtained a satisfactory performance with the mean Dice similarity coefficient of 0.92 and the average processing time of 0.75 s per case.

CONCLUSIONS

The results demonstrate that the proposed method is an automatic, fast, and accurate tool for searching the fetal cerebellum on ultrasound volumes.

Reference ranges of fetal spleen biometric parameters and volume assessed by three-dimensional ultrasound and their applicability in spleen malformations

AIM

The aims of this article are to establish three-dimensional ultrasonographic nomograms of normal fetal spleen size and to evaluate the clinical application value.

METHODS

An observational, cross-sectional study was performed on 455 women with a normal singleton pregnancy between 18 and 38 weeks' gestational age (GA). Fetal spleen volume was measured using three-dimensional ultrasound equipped with virtual organ computer-aided analysis, and biometric parameters were assessed in multiplanar mode to create reference ranges to GA. Thirty cases were randomly selected to conduct reliability analyses via intraobserver and interobserver ultrasonographic measurement. Moreover, 50 cases of suspected splenic malformations were evaluated by the newly established nomograms and followed up subsequently.

RESULTS

Using regression formulas, we found that fetal spleen size increased with GA. We observed strong reliability in intraobserver and interobserver volume measurements with intraclass correlation coefficients of 0.994 and 0.962. Bland-Altman analyses showed narrow limits of agreement [intraobserver: (-3.2 to 3.5)%; interobserver: (-3.2 to 4.3)%]. Of the 50 cases with suspected splenic malformations, six cases of splenomegaly and one case of splenic cyst were diagnosed.

CONCLUSION

Three-dimensional ultrasound nomograms of normal fetal spleen size across a range of GA have a strong diagnostic value. Volume measurements with good reliability were optimal in clinical practice.

Multidimensional analysis of fetal posterior fossa in health and disease

Fetal magnetic resonance imaging (MRI) is now routinely used to further investigate cerebellar malformations detected with ultrasound. However, the lack of 2D and 3D biometrics in the current literature hinders the detailed characterisation and classification of cerebellar anomalies. The main objectives of this fetal neuroimaging study were to provide normal posterior fossa growth trajectories during the second and third trimesters of pregnancy via semi-automatic segmentation of reconstructed fetal brain MR images and to assess common cerebellar malformations in comparison with the reference data. Using a 1.5-T MRI scanner, 143 MR images were obtained from 79 normal control and 53 fetuses with posterior fossa abnormalities that were grouped according to the severity of diagnosis on visual MRI inspections. All quantifications were performed on volumetric datasets, and supplemental outcome information was collected from the surviving infants. Normal growth trajectories of total brain, cerebellar, vermis, pons and fourth ventricle volumes showed significant correlations with 2D measurements and increased in second-order polynomial trends across gestation (Pearson r, p < 0.05). Comparison of normal controls to five abnormal cerebellum subgroups depicted significant alterations in volumes that could not be detected exclusively with 2D analysis (MANCOVA, p < 0.05). There were 15 terminations of pregnancy, 8 neonatal deaths, and a spectrum of genetic and neurodevelopmental outcomes in the assessed 24 children with cerebellar abnormalities. The given posterior fossa biometrics enhance the delineation of normal and abnormal cerebellar phenotypes on fetal MRI and confirm the advantages of utilizing advanced neuroimaging tools in clinical fetal research.

3D morphometric analysis of human fetal cerebellar development

To date, growth of the human fetal cerebellum has been estimated primarily from linear measurements from ultrasound and 2D magnetic resonance imaging (MRI). In this study, we use 3D analytical methods to develop normative growth trajectories for the cerebellum in utero. We measured cerebellar volume, linear dimensions, and local surface curvature from 3D reconstructed MRI of the human fetal brain (N = 46). We found that cerebellar volume increased approximately 7-fold from 20 to 31 gestational weeks. The better fit of the exponential curve (R (2) = 0.96) compared to the linear curve (R (2) = 0.92) indicated acceleration in growth. Within-subject cerebellar and cerebral volumes were highly correlated (R (2) = 0.94), though the cerebellar percentage of total brain volume increased from approximately 2.4% to 3.7% (R (2) = 0.63). Right and left hemispheric volumes did not significantly differ. Transcerebellar diameter, vermal height, and vermal anterior to posterior diameter increased significantly at constant rates. From the local curvature analysis, we found that expansion along the inferior and superior aspects of the hemispheres resulted in decreased convexity, which is likely due to the physical constraints of the dura surrounding the cerebellum and the adjacent brainstem. The paired decrease in convexity along the inferior vermis and increased convexity of the medial hemisphere represents development of the paravermian fissure, which becomes more visible during this period. In this 3D morphometric analysis of the human fetal cerebellum, we have shown that cerebellar growth is accelerating at a greater pace than the cerebrum and described how cerebellar growth impacts the shape of the structure.

Effect of malaria on placental volume measured using three-dimensional ultrasound: a pilot study

BACKGROUND

The presence of malaria parasites and histopathological changes in the placenta are associated with a reduction in birth weight, principally due to intrauterine growth restriction. The aim of this study was to examine the feasibility of studying early pregnancy placental volumes using three-dimensional (3D) ultrasound in a malaria endemic area, as a small volume in the second trimester may be an indicator of intra-uterine growth restriction and placental insufficiency.

METHODS

Placenta volumes were acquired using a portable ultrasound machine and a 3D ultrasound transducer and estimated using the Virtual Organ Computer-aided AnaLysis (VOCAL) image analysis software package. Intra-observer reliability and limits of agreement of the placenta volume measurements were calculated. Polynomial regression models for the mean and standard deviation as a function of gestational age for the placental volumes of uninfected women were created and tested. Based on these equations each measurement was converted into a z -score. The z-scores of the placental volumes of malaria infected and uninfected women were then compared.

RESULTS

Eighty-four women (uninfected = 65; infected = 19) with a posterior placenta delivered congenitally normal, live born, single babies. The mean placental volumes in the uninfected women were modeled to fit 5th, 10th, 50th, 90th and 95th centiles for 14-24 weeks' gestation. Most placenta volumes in the infected women were below the 50th centile for gestational age; most of those with Plasmodium falciparum were below the 10th centile. The 95% intra-observer limits of agreement for first and second measurements were ± 37.0 mL and ± 25.4 mL at 30 degrees and 15 degrees rotation respectively.

CONCLUSION

The new technique of 3D ultrasound volumetry of the placenta may be useful to improve our understanding of the pathophysiological constraints on foetal growth caused by malaria infection in early pregnancy.

A review of fetal volumetry: the need for standardization and definitions in measurement methodology

Volume charts of fetal organs and structures vary considerably among studies. This review identified 42 studies reporting normal volumes, namely for fetal brain (n = 3), cerebellum (n = 4), liver (n = 6), femur (n = 2), lungs (n = 15), kidneys (n = 3) and first-trimester embryo (n = 9). The differences among median volumes were expressed both in percentage form and as standard deviation scores. Wide discrepancies in reported normal volumes make it extremely difficult to diagnose pathological organ growth reliably. Given its magnitude, this variation is likely to be due to inconsistencies in volumetric methodology, rather than population differences. Complicating factors include the absence of clearly defined anatomical landmarks for measurement; inadequate assessment and reporting of method repeatability; the inherent difficulty in validating fetal measurements in vivo against a reference standard; and a multitude of mutually incompatible three-dimensional (3D) imaging formats and software measuring tools. An attempt to standardize these factors would improve intra- and inter-researcher agreement concerning reported volumetric measures, would allow generalization of reference data across different populations and different ultrasound systems, and would allow quality assurance in 3D fetal biometry. Failure to ensure a quality control process may hamper the wide use of 3D ultrasound.

Development of the human fetal cerebellum in the second trimester: a post mortem magnetic resonance imaging evaluation

The cerebellum is one of the most important structures in the posterior cranial fossa, but the characterization of its development by magnetic resonance imaging (MRI) is incomplete. We scanned 40 fetuses that had no morphological brain disorder at 14-22 weeks of gestation using 7.0 T MRI. Amira 4.1 software was used to determine morphological parameters of the fetal cerebellum, which included the cerebellar volume (CV), transverse cerebellar diameter (TCD), and the length and width of the vermis. The relationship between these measurements and gestational age (GA) was analysed. We found that the primary fissure was visible at week 14 of gestation. From week 16, the prepyramidal fissure, the secondary fissure and the dentate nucleus could be identified. The posterolateral fissure and the fourth ventricle were recognized at week 17, whereas the tentorium of the cerebellum was visible at week 20. The relationships between GA and CV, TCD, and the width and length of the vermis were described adequately by second-order polynomial regression curves. The ratios between TCD and vermis length and between TCD and vermis width decreased with GA. These results show that 7.0 T MRI can show the trajectory of cerebellar development clearly. They increase our understanding of normal cerebellar development in the fetus, and will facilitate the diagnosis of pathological intrauterine changes in the cerebellum.

Reliability of fetal cardiac volumetry using spatiotemporal image correlation: assessment of in-vivo and in-vitro measurements

OBJECTIVE

To assess the reliability of measurement of fetal cardiac ventricular volume, stroke volume, and ejection fraction with four-dimensional ultrasound using spatiotemporal image correlation (STIC).

METHODS

Volume datasets were collected from two sources: 24 from fetuses over a range of gestational ages and 12 from a miniature balloon model. Datasets were analyzed by three observers, repeatedly in 12 fetal datasets and all balloon datasets. Volume calculations were obtained by manually tracing multiple parallel slices (three-dimensional (3D) slice method). Measurement error was assessed by calculating standard errors of measurement (SEM) and coefficients of variation (CV). Reliability was assessed by calculating interobserver and intraobserver intraclass correlation coefficients (ICC).

RESULTS

Measurement errors of balloon volumes were small and reliability was good (SEM <or= 0.07 mL, ICC 0.98-1.00). Fetal ventricle volume measurement error ranged from 0.09 to 0.20 mL and CV from 14.6 to 28.3%. Ventricular volume reliabilities for intra- and interobserver comparisons were greater than or equal to 0.94 and 0.75, respectively. Fetal stroke volume measurement error (SEM 0.17 mL), CV (21.9%) and reliability were measured (intraobserver ICC: left ventricle stroke volume (LVSV), 0.93 vs. right ventricle stroke volume (RVSV), 0.88; interobserver ICC: LVSV, 0.75 vs. RVSV, 0.86). The measurement error decreased with increasing operator experience. The reliability of ejection fraction calculations was poor (ICC < 0.7) for intra- and interobserver comparisons.

CONCLUSIONS

Volume measurements obtained with STIC and 3D slice methods using a balloon model were reliable. In the fetus, measurement errors decreased with increasing operator experience, and reliability was better for stroke volume than for ejection fraction.

Fetal transverse cerebellar diameter measured by ultrasound does not differ between genders

PURPOSE

The aim of this study was to determine the correlation between fetal transverse cerebellar diameter (TCD) and gestational age of male and female fetus in women under low-risk prenatal care between the 13th and 40th week of gestation.

METHODS

A cross-sectional study was carried out with 184 pregnant women, at the age of 18 years or more, gestational age ranging from 13 to 40 weeks, with a single fetus. A single TCD measurement by ultrasound was used for each fetus. Correlations between fetal TCD and gestational age were determined for the whole sample and each gender separately.

RESULTS

We identified 102 males and 82 female fetuses. A linear correlation was observed between fetal TCD and gestational age for the whole sample (r = 96.9%; p < 0.001). A significant linear correlation was also observed for both males (r = 97.0%; p < 0.001) and females (r = 96.9%; p < 0.001). Comparing the regression lines between genders, no significant difference was observed.

CONCLUSIONS

The data of this study suggest TCD fetal ultrasound as a predictive biometric parameter of gestational age independently of fetal gender in the last two trimesters of a pregnancy.

Automatic segmentation of the cerebellum of fetuses on 3D ultrasound images, using a 3D Point Distribution Model

Analysis of fetal biometric parameters on ultrasound images is widely performed and it is essential to estimate the gestational age, as well as the fetal growth pattern. The use of three dimensional ultrasound (3D US) is preferred over other tomographic modalities such as CT or MRI, due to its inherent safety and availability. However, the image quality of 3D US is not as good as MRI and therefore there is little work on the automatic segmentation of anatomic structures in 3D US of fetal brains. In this work we present preliminary results of the development of a 3D Point Distribution Model (PDM), for automatic segmentation, of the cerebellum in 3D US of the fetal brain. The model is adjusted to a fetal 3D ultrasound, using a genetic algorithm which optimizes a model fitting function. Preliminary results show that the approach reported is able to automatically segment the cerebellum in 3D ultrasounds of fetal brains.