Utilization of 3-T fetal magnetic resonance imaging in clinical practice: a single-institution experience

Neonatal Anthropometric Measurements: A Comparison of Neonates With 3-T Fetal MRI Exposure, With 1.5-T Fetal MRI Exposure, and Without In-Utero MRI Exposure

Background: Fetal MRI is increasingly performed at 3 T. Nonetheless, safety concerns persist regarding potential increased risk of intrauterine growth restriction from in-utero 3-T MRI exposure. Objective: To compare neonatal anthropometric measurements between newborns who underwent 3-T fetal MRI, newborns who underwent 1.5-T fetal MRI, and newborns without in utero MRI exposure. Methods: This single-center retrospective study included gravid patients who underwent fetal ultrasound and possible 1.5-T or 3-T fetal MRI within 10 days from January 2017 to January 2022. For each included patient who also underwent 3-T fetal MRI, one matched patient who also underwent 1.5-T MRI and two matched patients without in-utero MRI exposure, were randomly selected. Matching was based on gestational age per the fetal ultrasound. Neonatal anthropometric characteristics were compared among groups. Results: The final sample included 416 patients (mean age, 32±5 years), 104 in the 3-T MRI group, 104 in the 1.5-T MRI group, and 208 in the MRI-unexposed group. Mean gestational age at the time of fetal ultrasound used for matching was 27 weeks 2 days in the 3-T group, 25 weeks 2 days in the 1.5-T group, and 26 weeks 0 days in the MRI-unexposed group (p=.07). The distribution of indications for fetal MRI was not significantly different between the 3-T and 1.5-T groups (p=.62). Mean gestational age at delivery was 37 weeks 5 days in the 3-T group, 38 weeks 0 day in the 1.5-T group, and 38 weeks 2 days in the unexposed group (p=.51). No significant difference (p=.09) was observed among groups in mean neonatal weight (3-T: 3120±753 g; 1.5-T: 3104±704 g; unexposed: 2967±614 g); neonatal weight percentile (3-T: 45±27; 1.5-T: 42±26; MRI: 41±24); neonatal head circumference (3-T: 34±3 cm; 1.5-T: 34±3 cm; unexposed: 34±2 cm), or neonatal head circumference percentile (3-T: 48±29; 1.5-T: 42±23; unexposed: 43±30). Conclusion: There were no significant differences in neonatal anthropometric measurements among newborns who underwent in-utero 3-T MRI, newborns who underwent in-utero 1.5-T MRI, and newborns without in-utero MRI exposure. Clinical Impact: The results support the safety of 3-T MRI with respect to growth of the developing fetus.

Effect of magnet strength on fetal brain biometry - a single-center retrospective MRI-based cohort study

PURPOSE

Abnormal fetal brain measurements might affect clinical management and parental counseling. The effect of between-field-strength differences was not evaluated in quantitative fetal brain imaging until now. Our study aimed to compare fetal brain biometry measurements in 3.0 T with 1.5 T scanners.

METHODS

A retrospective cohort of 1150 low-risk fetuses scanned between 2012 and 2021, with apparently normal brain anatomy, were retrospectively evaluated for biometric measurements. The cohort included 1.5 T (442 fetuses) and 3.0 T scans (708 fetuses) of populations with comparable characteristics in the same tertiary medical center. Manually measured biometry included bi-parietal, fronto-occipital and trans-cerebellar diameters, length of the corpus-callosum, vermis height, and width. Measurements were then converted to centiles based on previously reported biometric reference charts. The 1.5 T centiles were compared with the 3.0 T centiles.

RESULTS

No significant differences between centiles of bi-parietal diameter, trans-cerebellar diameter, or length of the corpus callosum between 1.5 T and 3.0 T scanners were found. Small absolute differences were found in the vermis height, with higher centiles in the 3.0 T, compared to the 1.5 T scanner (54.6th-centile, vs. 39.0th-centile, p < 0.001); less significant differences were found in vermis width centiles (46.9th-centile vs. 37.5th-centile, p = 0.03). Fronto-occipital diameter was higher in 1.5 T than in the 3.0 T scanner (66.0th-centile vs. 61.8th-centile, p = 0.02).

CONCLUSIONS

The increasing use of 3.0 T MRI for fetal imaging poses a potential bias when using 1.5 T-based charts. We elucidate those biometric measurements are comparable, with relatively small between-field-strength differences, when using manual biometric measurements. Small inter-magnet differences can be related to higher spatial resolution with 3 T scanners and may be substantial when evaluating small brain structures, such as the vermis.

Fetal cardiovascular blood flow MRI: techniques and applications

Fetal cardiac MRI is challenging due to fetal and maternal movements as well as the need for a reliable cardiac gating signal and high spatiotemporal resolution. Ongoing research and recent technical developments to address these challenges show the potential of MRI as an adjunct to ultrasound for the assessment of the fetal heart and great vessels. MRI measurements of blood flow have enabled the assessment of normal fetal circulation as well as conditions with disrupted circulations, such as congenital heart disease, along with associated organ underdevelopment and hemodynamic instability. This review provides details of the techniques used in fetal cardiovascular blood flow MRI, including single slice and volumetric imaging sequences, post-processing and analysis, along with a summary of applications in human studies and animal models.

Maternal blood inflammatory marker levels increased in fetuses with ventriculomegaly

Background

Fetal ventriculomegaly (VM) is one of the most common abnormalities of the central nervous system (CNS), which can be significantly identified by brain anomalies prenatally by magnetic resonance imaging (MRI). Aberrant white blood cells (WBCs) levels indicate that the maternal is suffering from the infection. Previous studies have confirmed that prenatal infection can affect fetal brain structure, but there is no research revealed the association between maternal blood parameters with fetal VM until now.

Methods

We measured the width of the lateral ventricle of 142 fetuses, which were divided into the fetal VM group (n = 70) and the normal lateral ventricle group (n = 72). We compared maternal blood cell levels between the two groups and investigate potential biomarkers of fetal VM.

Result

High levels of maternal WBC and neutrophil (NE#) levels were observed in fetuses with VM (p < 0.001), while lymphocyte percentage, monocytes (MO#), neutrophil/lymphocyte ratio (NLR), and platelet were also increased in the fetal VM group (p = 0.033, 0.027, 0.034, and 0.025, respectively). receiver-operator curve (ROC) analysis suggested that WBC and NE# counts might be useful to distinguish fetuses with enlarged lateral ventricles (AUC = 0.688, 0.678, respectively).

Conclusion

The current study emphasizes the importance of maternal infection for fetal brain growth, which could provide important information for prenatal diagnosis of CNS anomalies. Future research needs longitudinal analysis and exploration of the influence of maternal blood inflammatory marker levels on fetal brain development.

Magnetic resonance imaging of the monkey fetal brain in utero

Non-human primates (NHPs) are the closest living relatives of the human and play a critical role in investigating the effects of maternal viral infection and consumption of medicines, drugs, and alcohol on fetal development. With the advance of contemporary fast MRI techniques with parallel imaging, fetal MRI is becoming a robust tool increasingly used in clinical practice and preclinical studies to examine congenital abnormalities including placental dysfunction, congenital heart disease (CHD), and brain abnormalities non-invasively. Because NHPs are usually scanned under anesthesia, the motion artifact is reduced substantially, allowing multi-parameter MRI techniques to be used intensively to examine the fetal development in a single scanning session or longitudinal studies. In this paper, the MRI techniques for scanning monkey fetal brains in utero in biomedical research are summarized. Also, a fast imaging protocol including T2-weighted imaging, diffusion MRI, resting-state functional MRI (rsfMRI) to examine rhesus monkey fetal brains in utero on a clinical 3T scanner is introduced.

Clinical Applications of Fetal MRI in the Brain

Fetal magnetic resonance imaging (MRI) has become a widely used tool in clinical practice, providing increased accuracy in prenatal diagnoses of congenital abnormalities of the brain, allowing for more accurate prenatal counseling, optimization of perinatal management, and in some cases fetal intervention. In this article, a brief description of how fetal ultrasound (US) and fetal MRI are used in clinical practice will be followed by an overview of the most common reasons for referral for fetal MRI of the brain, including ventriculomegaly, absence of the cavum septi pellucidi (CSP) and posterior fossa anomalies.