Prognostic value of diffusion-weighted magnetic resonance imaging of brain in fetal growth restriction: results of prospective multicenter study

Is the rabbit a natural model of fetal growth restriction? Morphological and functional characterization study using diffusion-weighted MRI and stereology

INTRODUCTION

Rabbits are routinely used as a natural model of fetal growth restriction (FGR); however, no studies have confirmed that rabbits have FGR. This study aimed to characterize the fetoplacental unit (FPU) in healthy pregnant rabbits using diffusion-weighted MRI and stereology. A secondary objective of the study was to describe the associations among findings from diffusion-weighted MRI (DW-MRI), fetal weight measurement and histological analysis of the placenta.

METHODS

Pregnant rabbits underwent DW-MRI under general anesthesia on embryonic day 28 of pregnancy. MR imaging was performed at 3.0 T. The apparent diffusion coefficient (ADC) values were calculated for the fetal brain, liver, and placenta. The placenta was analyzed by stereology (volume density of trophoblasts, the maternal blood space and fetal vessels). Each fetus and placenta were weighed. Two groups of fetuses were defined according to the position in the uterine horn (Cervix group versus Ovary group).

RESULTS

We analyzed 20 FPUs from 5 pregnant rabbits. Fetuses and placentas were significantly lighter in the Cervix group than in the Ovary group (34.7 ± 3.7 g vs. 40.2 ± 5.4 g; p = 0.02). Volume density analysis revealed that the percentage of fetal vessels, the maternal blood space and trophoblasts was not significantly affected by the position of the fetus in the uterine horn. There was no difference in ADC values according to the position of the fetus in the uterine horn, and there was no correlation between ADC values and fetal weight.

DISCUSSION

The findings of a multimodal evaluation of the placenta in a rabbit model of FGR suggested is not a natural model of fetal growth restriction.

Diffusion-Weighted MRI of the Fetal Brain in Fetal Growth Restriction With Maternal Preeclampsia or Gestational Hypertension

BACKGROUND

The fetal neurodevelopmental microstructural alterations of intrauterine exposure to preeclampsia (PE) or gestational hypertension (GH) remain unknown.

PURPOSE

To evaluate the differences in diffusion-weighted imaging (DWI) of the fetal brain between normotensive pregnancies and PE/GH pregnancies, with a focus on PE/GH pregnancies with fetal growth restriction (FGR).

STUDY TYPE

Retrospective matched case-control study.

POPULATION

40 singleton pregnancies with PE/GH complicated by FGR, and 3 paired control groups (PE/GH without FGR, normotensive FGR, normotensive pregnancies) (28-38 gestational weeks).

FIELD STRENGTH/SEQUENCE

DWI with single-shot echo-planar imaging at 1.5 Tesla.

ASSESSMENT

The apparent diffusion coefficient (ADC) values were calculated in the centrum semi-ovale (CSO), parietal white matter (PWM), frontal white matter (FWM), occipital white matter (OWM), temporal white matter (TWM), basal ganglia, thalamus (THAL), pons, and cerebellar hemisphere.

STATISTICAL TESTS

Student t test or Wilcoxon matched test was used to reveal the difference of ADC values among the investigated brain regions. A correlation between gestational age (GA) and ADC values was determined by linear regression analysis.

RESULTS

Compared with fetuses in PE/GH without FGR and those with normotensive pregnancies, fetuses in the PE/GH with FGR group had significantly lower average ADC measurements of supratentorial regions (1.65 ± 0.09 vs. 1.71 ± 0.10 10-3  mm2 /sec; vs. 1.73 ± 0.11 10-3  mm2 /sec, respectively). Regions of significantly decreased ADC values in the fetal brain included CSO, FWM, PWM, OWM, TWM and THAL in cases of PE/GH with FGR. ADC values from supratentorial regions in PE/GH pregnancies were not significantly correlated with GA (P = 0.12, 0.26); however, this trend was statistically significant in the normotensive groups.

DATA CONCLUSION

ADC values may indicate fetal brain developmental alterations in PE/GH with FGR fetuses but more microscopic and morphological studies are necessary to provide additional evidence to offer a different interpretation of this trend in fetal brain.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY STAGE: 3.

Harnessing the Power of Advanced Fetal Neuroimaging to Understand In Utero Footprints for Later Neuropsychiatric Disorders

Adverse intrauterine events may profoundly impact fetal risk for future adult diseases. The mechanisms underlying this increased vulnerability are complex and remain poorly understood. Contemporary advances in fetal magnetic resonance imaging (MRI) have provided clinicians and scientists with unprecedented access to in vivo human fetal brain development to begin to identify emerging endophenotypes of neuropsychiatric disorders such as autism spectrum disorder, attention-deficit/hyperactivity disorder, and schizophrenia. In this review, we discuss salient findings of normal fetal neurodevelopment from studies using advanced, multimodal MRI that have provided unparalleled characterization of in utero prenatal brain morphology, metabolism, microstructure, and functional connectivity. We appraise the clinical utility of these normative data in identifying high-risk fetuses before birth. We highlight available studies that have investigated the predictive validity of advanced prenatal brain MRI findings and long-term neurodevelopmental outcomes. We then discuss how ex utero quantitative MRI findings can inform in utero investigations toward the pursuit of early biomarkers of risk. Lastly, we explore future opportunities to advance our understanding of the prenatal origins of neuropsychiatric disorders using precision fetal imaging.

Anatomical and diffusion-weighted imaging of brain abnormalities in third-trimester fetuses with cytomegalovirus infection

OBJECTIVES

In this study of cytomegalovirus (CMV)-infected fetuses with first-trimester seroconversion, we aimed to evaluate the detection of brain abnormalities using magnetic resonance imaging (MRI) and neurosonography (NSG) in the third trimester, and compare the grading systems of the two modalities. We also evaluated the feasibility of routine use of diffusion-weighted imaging (DWI) fetal MRI and compared the regional apparent diffusion coefficient (ADC) values between CMV-infected fetuses and presumed normal, non-infected fetuses in the third trimester.

METHODS

This was a retrospective review of MRI and NSG scans in fetuses with confirmed first-trimester CMV infection performed between September 2015 and August 2019. Brain abnormalities were recorded and graded using fetal MRI and NSG grading systems to compare the two modalities. To investigate feasibility of DWI, a four-point rating scale (poor, suboptimal, good, excellent) was applied to assess the quality of the images. Quantitative assessment was performed by placing a freehand drawn region of interest in the white matter of the frontal, parietal, temporal and occipital lobes and the basal ganglia, pons and cerebellum to calculate ADC values. Regional ADC measurements were obtained similarly in a control group of fetuses with negative maternal CMV serology in the first trimester, normal brain findings on fetal MRI and normal genetic testing.

RESULTS

Fifty-three MRI examinations of 46 fetuses with confirmed first-trimester CMV infection were included. NSG detected 24 of 27 temporal cysts seen on MRI scans, with a sensitivity of 78% and an accuracy of 83%. NSG did not detect abnormal gyration visible on two (4%) MRI scans. Periventricular calcifications were detected on two MRI scans compared with 10 NSG scans. While lenticulostriate vasculopathy was detected on 11 (21%) NSG scans, no fetus demonstrated this finding on MRI. MRI grading correlated significantly with NSG grading of brain abnormalities (P < 0.0001). Eight (15%) of the DWI scans in the CMV cohort were excluded from further analysis because of insufficient quality. The ADC values of CMV-infected fetuses were significantly increased in the frontal (both sides, P < 0.0001), temporal (both sides, P < 0.0001), parietal (left side, P = 0.0378 and right side, P = 0.0014) and occipital (left side, P = 0.0002 and right side, P < 0.0001) lobes and decreased in the pons (P = 0.0085) when compared with non-infected fetuses. The ADC values in the basal ganglia and the cerebellum were not significantly different in CMV-infected fetuses compared with normal controls (all P > 0.05). Temporal and frontal ADC values were higher in CMV-infected fetuses with more severe brain abnormalities compared to fetuses with mild abnormalities.

CONCLUSIONS

Ultrasound and MRI are complementary during the third trimester in the assessment of brain abnormalities in CMV-infected fetuses, with a significant correlation between the grading systems of the two modalities. On DWI in the third trimester, the ADC values in several brain regions are abnormal in CMV-infected fetuses compared with normal controls. Furthermore, they seem to correlate in the temporal area and, to a lesser extent, frontal area with the severity of brain abnormalities associated with CMV infection. Larger prospective studies are needed for further investigation of the microscopic nature of diffusion abnormalities and correlation of different imaging findings with postnatal outcome. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

The Influence of Various Cerebral and Extracerebral Pathologies on Apparent Diffusion Coefficient Values in the Fetal Brain

BACKGROUND AND PURPOSE

The changing MRI signal accompanying brain maturation in fetal brains can be quantified on apparent diffusion coefficient (ADC) maps. Deviations from the natural course of ADC values may reflect structural pathology. The purpose of this study was to determine the influence of fetal pathologies on the ADC values in different regions of the fetal brain and their evolution with increasing gestational age.

METHODS

This was a retrospective study of 291 fetuses evaluated between the 14th and the 40th week of gestation using diffusion‐weighted imaging (DWI). Fetuses with normal MRI findings but sonographically suspected pathology or fetuses with abnormalities not affecting the brain were analyzed in the control group and compared to fetuses suffering from different pathologies like hydrocephalus/ventriculomegaly, brain malformations, infections, ischemia/hemorrhage, diaphragmatic hernias, and congenital heart disease. Pairwise ADC measurements in each side of the white matter (WM) of the frontal, parietal, and occipital lobes, in the basal ganglia and the cerebellum, as well as a single measurement in the pons were performed and were plotted against gestational age.

RESULTS

In the control group, brain maturation followed a defined gradient, resulting in lower ADC values in the most mature regions. Each disorder group experienced abnormal patterns of evolution of the ADC values over time deviating from the expected course.

CONCLUSIONS

The ADC values in different regions of the fetal brain and their evolution with increasing gestational age are influenced by pathologies compromising the cerebral maturation.