Unlike ultrasound (US) imaging, foetal magnetic resonance imaging (MRI) is not significantly limited by maternal obesity, oligohydramnios, uterine myoma, twins, and foetal lie, which impair US visualization of the foetus. The present study aimed to introduce our foetal cardiac MRI scanning technology and over 14-years of experience on the potential utility of foetal cardiac MRI examination as an adjunct to foetal technically inadequate echocardiography (Echo). This retrospective review included 1,573 pregnant women [1,619 foetuses (46 twins)] referred for a foetal cardiac MRI because of technically limited Echo. Foetal cardiac MRI was performed using two 1.5 T units. Among the 1,619 foetuses referred for cardiac MRI, 1,379 (85.2%) cases were followed up using postnatal imaging and/ or surgery, 240 (14.8%), including three twins, had no follow-up confirmation because of pregnancy termination without autopsy or loss to follow-up. The results of the present study indicated that foetal cardiac MRI examinations can be a useful adjunct to foetal echocardiography when the technical limitations of echocardiography make it inadequate for diagnosis. The foetal cardiovascular system is the most frequently affected among congenital pathologies. Congenital heart disease (CHD) is the most common congenital anomaly and is the major cause of infant mortality 1. Prenatal diagnosis of certain types of CHD, such as transposition of the great arteries (TGA), pulmonary atresia with intact ventricle septum (PA/IVS), hypoplastic left heart syndrome (HLHS), obstructive total anomalous pulmonary veins connection (TAPVC), and other severe CHDs has been associated with improved outcomes and decreased perioperative mortality 2. Foetal cardiac examination has become a routine part of screening foetal ultrasound (US), and suspected cardiac anomalies will require more comprehensive evaluation using foetal echocardiography (Echo). Foetal magnetic resonance imaging (MRI) examinations have become useful adjuncts to ultrasound (US) exams when US diagnosis is doubtful. To date, there has been no clinical or experimental evidence that MRI has any adverse effects on the human foetus in the second or third trimester 3,4. Unlike US imaging, foetal MRI is not significantly limited by maternal obesity, oligohydramnios, uterine myoma, twins, and foetal lie, all of which impair US visualization of the foetus 5-7. The visualization of the foetal heart using MRI is complicated because of the small heart size, high heart rate, and foetal motion 4,8. Several studies revealed new techniques (such as compressed sensing, motion correction, and foetal cardiac gating) to reveal further details in MRI studies of the foetal heart and great vessels 10-13. Foetal cardiac MRI has the potential to complement echocardiography to detect cardiovascular anomalies 14,15. However, currently, there has been no report on the potential utility of foetal cardiovascular MRI as an adjunct to foetal echocardiography when echocardiography is technically limited, either from a single c...

Background: Several published studies have shown alterations of brain development in third-trimester fetuses with congenital heart disease (CHD). However, little is known about the timing and pattern of altered brain development in fetuses with CHD. Purpose: To investigate the changes in the volume of intracranial structures in fetuses with CHD by three-dimensional (3D) volumetric magnetic resonance imaging (MRI) in the earlier stages of pregnancy (median gestational age [GA], 26 weeks). Study Type: Retrospective. Population: Forty women carrying a fetus with CHD (including 20 fetuses with GA <26 weeks) and 120 pregnant women carrying a healthy fetus (including 50 fetuses with GA <26 weeks). Field Strength/Sequence: Two-dimensional single-shot turbo spin echo sequence at 1.5 -T. Assessment: Three-dimensional volumetric parameters from slice-to-volume registered images, including cortical gray matter volume (GMV), subcortical brain tissue volume (SBV), intracranial cavity volume (ICV), lateral ventricles volume (VV), cerebellum, brainstem, and extra-cerebrospinal fluid (e-CSF) were quantified by manual segmentation from one primary and two secondary observers. Statistical Tests: Volumes were presented graphically with quadratic curve fitting. Scatterplots were produced mapping volumes against GA in normal and CHD fetuses. For GA <26 weeks, Z scores were calculated and Student's t-tests were conducted to compare volumes between the normal and CHD fetuses. Results: In fetuses with CHD GMV, SBV, cerebellum, and brainstem were significantly reduced (all P < 0.05) in early stages of pregnancy (GA <26 weeks), with differences becoming progressively greater with increasing GA. Compared with normal fetuses, e-CSF, e-CSF to ICV ratio, and VV were higher in fetuses with CHD (all P < 0.05). However, ICV volume and the GMV to SBV ratio were not significantly reduced in the CHD group (P = 0.94 and P = 0.13, respectively) during the middle gestation (GA <26 weeks). Data Conclusion: There appear to be alterations of brain development trajectory in CHD fetuses that can be detected by 3D volumetric MRI in the earlier stages of pregnancy. Level of Evidence: 4 Technical Efficacy: Stage 3

ObjectiveThe purpose of this study is to establish a reference of intracranial structure volumes in normal fetuses ranging from 19 to 37 weeks' gestation (mean 27 weeks).Materials and MethodsA retrospective analysis of 188 MRI examinations (1.5 T) of fetuses with a normal brain appearance (19–37 gestational weeks) from January 2018 to December 2021 was included in this study. Three dimensional (3-D) volumetric parameters from slice-to-volume reconstructed (SVR) images, such as total brain volume (TBV), cortical gray matter volume (GMV), subcortical brain tissue volume (SBV), intracranial cavity volume (ICV), lateral ventricles volume (VV), cerebellum volume (CBV), brainstem volume (BM), and extra-cerebrospinal fluid volume (e-CSFV), were quantified by manual segmentation from two experts. The mean, SD, minimum, maximum, median, and 25th and 75th quartiles for intracranial structures volume were calculated per gestational week. A linear regression analysis was used to determine the gestational weekly age-related change adjusted for sex. A t-test was used to compare the mean TBV and ICV values to previously reported values at each gestational week. The formulas to calculate intracranial structures volume derived from our data were created using a regression model. In addition, we compared the predicted mean TBV values derived by our formula with the expected mean TBV predicted by the previously reported Jarvis' formula at each time point. For intracranial volumes, the intraclass correlation coefficient (ICC) was calculated to convey association within and between observers.ResultsThe intracranial volume data are shown in graphs and tabular summaries. The male fetuses had significantly larger VV compared with female fetuses (p = 0.01). Measured mean ICV values at 19 weeks are significantly different from those published in the literature (p &lt; 0.05). Means were compared with the expected TBV generated by the previously reported formula, showing statistically differences at 22, 26, 29, and 30 weeks' gestational age (GA) (all p &lt; 0.05). A comparison between our data-derived formula and the previously reported formula for TBV showed very similar values at every GA. The predicted TBV means derived from the previously reported formula were all within the 95% confidence interval (CI) of the predicted means of this study. Intra- and inter-observer agreement was high, with an intraclass correlation coefficient larger than 0.98.ConclusionWe have shown that the intracranial structural volume of the fetal brain can be reliably quantified using 3-D volumetric MRI with a high degree of reproducibility and reinforces the existing data with more robust data in the earlier second and third stages of pregnancy.

Magnetic resonance imaging (MRI) is widely used to provide detailed information regarding fetal brain development in utero. Conventional T1-and T2weighted sequences provide anatomical details of the normal brain and demonstrate brain lesions. In addition to providing highly detailed qualitative assessments of fetal brain development, advanced MRI methods such as threedimensional high-resolution MRI, diffusion MRI, magnetic resonance spectroscopy, and functional MRI can provide quantitative morphologic assessments of tissue microstructure and functional activity. This review aims to describe normal fetal brain development and highlight current state-of-the-art MRI sequences for fetal neuroimaging. We focus on current clinical applications which can provide a better understanding of in utero impairments in fetal brain development.

BACKGROUND AND PURPOSE: Abnormal ADC values are seen in ischemic brain lesions such as acute or chronic hypoxia. We aimed to assess whether ADC values in the developing brain measured by in utero DWI were different in fetuses with congenital heart disease compared with healthy controls. MATERIALS AND METHODS:In utero DWI was performed in 50 fetuses with congenital heart disease and 100 healthy controls at a similar gestational age. Pair-wise ADC values of the ROIs were manually delineated on each side of the frontal and periatrial WM and in the basal ganglia, thalamus, and cerebellar hemisphere, as well as a single measurement in the pons. RESULTS:Fetuses with congenital heart disease had significantly lower ADC values in frontal and periatrial WM and the pons than controls (all P , .05) in the early stages of pregnancy. However, ADC values in the thalamus were higher for fetuses with congenital heart disease than for controls (gestational age, $26 weeks). For ADC values in the cerebellar hemisphere, there was no obvious significance between cases and controls (P ¼ .07) in the late stages of pregnancy. Basal ganglia ADC values were consistently not significantly different between the 2 groups during the early and late stages of pregnancy (P ¼ .47; .21). CONCLUSIONS:Abnormal brain diffusivity can be detected using in utero DWI in fetuses with congenital heart disease. Abnormal ADC values found at a mean gestational age of 26 weeks suggest structural changes, which may provide an early indicator of the impact of congenital heart disease on the developing brain. ABBREVIATIONS: CHD ¼ congenital heart disease; GA ¼ gestational age; HLHS ¼ hypoplastic left-heart syndrome; TGA ¼ transposition of the great arteries; TOF ¼ tetralogy of Fallot

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