Fetal Brain Growth in the Early Second Trimester.

BACKGROUND AND PURPOSE: Recent advances in fetal MR imaging technology have enabled acquisition of diagnostic images in the early second trimester. Interpretation of these examinations is limited by a lack of familiarity with the developmental changes that occur during these early stages of growth. This study aimed to characterize normal fetal brain growth between the 12th and 20th weeks of gestational age. MATERIALS AND METHODS: This study was conducted as an observational retrospective analysis. Data were obtained from a tertiary care center's PACS database. All fetuses included had late fetal MR imaging (>20 weeks) or postnatal MR imaging, which confirmed normality. Each MR image was manually segmented, with ROIs placed to calculate the volume of the supratentorial parenchyma, brainstem, cerebellum, ventricular CSF, and extra-axial CSF. A linear regression analysis was used to evaluate gestational age as a predictor of the volume of each structure. RESULTS: Thirty-one subjects with a mean gestational age of 17.23 weeks (range, 12-19 weeks) were studied. There was a positive, significant association between gestational age and intracranial, supratentorial parenchyma; brainstem cerebellum; intraventricular CSF; and extra-axial CSF volumes (P < .001). Growth was fastest in the supratentorial parenchyma and extra-axial CSF. Fetal sex was not associated with the volume in any of the ROIs. CONCLUSIONS: This study demonstrates distinct trajectories for the major compartments of the fetal brain in the early second trimester. The fastest growth rates were observed in the supratentorial brain and extra-axial CSF.

Contrast-enhanced subharmonic aided pressure estimation for assessment of intracranial pressure in vivo.

BACKGROUND: Intracranial pressure (ICP) monitoring in children currently requires invasive techniques. Subharmonic aided pressure estimation (SHAPE) uses contrast-enhanced ultrasound (CEUS) to measure intravascular and interstitial pressure, but utility in ICP measurements has yet to be explored. OBJECTIVE: The objective of this study was to investigate SHAPE as a novel tool for noninvasive ICP measurements in fetal lambs. MATERIALS AND METHODS: Eighteen fetal lambs at 107-139 days gestational age (term = 145 days) underwent subdural ICP catheter placement. The brain was imaged in the coronal plane in CEUS mode optimized for SHAPE, while infusing an US contrast agent into the fetal circulation. After SHAPE calibration, saline was infused via the subdural catheter to increase ICP. Five-second SHAPE cine clips were obtained at various ICPs. Subharmonic intensity values of the whole brain and thalami were correlated with ICP values using mixed effects linear regression analyses and the strength of the relationship was evaluated by Spearman's rank-order correlation. RESULTS: Forty-nine experiments produced 723 datapoints, including SHAPE intensity values and mean ICP measurements. There was a statistically significant inverse relationship between SHAPE intensity values and ICP measurements in the whole brain and thalami (median rho value - 0.58 and - 0.56, respectively). CONCLUSION: SHAPE intensity values of the brain demonstrate an inverse and statistically significant correlation with in vivo ICP measurements in an animal model.

Risks of Single Fetal Demise after Laser for Twin-Twin Transfusion Syndrome.

INTRODUCTION: The aim of the study was to determine if markers of donor placental insufficiency and recipient cardiac dysfunction increase the risk for single fetal demise (SFD) after laser for twin-twin transfusion syndrome (TTTS). METHODS: Single-center retrospective review of patients who had laser for TTTS. Risk factors for donor and recipient demise within 1 week were compared in pregnancies with SFD and pregnancies with dual survival using χ2 or Fisher's exact test. Multivariate logistic regression was then performed. RESULTS: Of 398 procedures, 305 (76.6%) had dual survival, 36 (9.0%) had donor demise, 28 (7.0%) had recipient demise, and 9 (2.3%) had dual demise. The remaining 20 (5.0%) patients had complicated courses with pregnancy loss or further intervention. In the 64 pregnancies with SFD, 29 (81%) in the donor group and 20 (71%) in the recipient group occurred in the first postoperative week. For the donor demise group, estimated fetal weight (EFW) <10%, EFW <3%, EFW <1%, EFW discordance >25%, and EFW discordance >30% did not increase the risk for donor demise except in cases that also had umbilical artery absent or reversed end diastolic flow (AREDF). Donor AREDF was the only independent risk factor for early donor demise. For the recipient demise group, recipient abnormal venous Dopplers were associated with increased risk while EFW discordance >25% was associated with decreased risk of recipient loss. DISCUSSION/CONCLUSION: In our cohort, donor growth restriction did not increase the risk of early donor demise after laser unless there was also donor AREDF. Donor AREDF was an independent risk factor for donor demise likely due to the severity of placental insufficiency. Abnormal recipient venous Doppler indices increased the risk of early recipient loss while a large intertwin discordance decreased the risk. This may be explained by profound overload in cases with recipient abnormal venous Doppler velocimetry and a lower risk of substantial fluid shifts from a relatively smaller donor territory when there is a large discordance.

Fetal thoracic teratomas: mediastinal or pericardial?

BACKGROUND: Mediastinal and pericardial teratomas have overlapping imaging features that may make accurate prenatal diagnosis challenging. OBJECTIVE: To identify prenatal imaging features that may aid in distinguishing between mediastinal and pericardial teratomas. MATERIALS AND METHODS: Prenatally diagnosed pericardial and mediastinal teratomas evaluated at our fetal center from 1995 to 2020 were included in this Institutional Review Board-approved study. Lesion volume was calculated using prospectively reported ultrasound (US) measurements and the formula of a prolate ellipsoid, which was then normalized to head circumference. Prenatal US and magnetic resonance imaging (MRI) studies were anonymized with two fetal imagers reviewing the US studies and two different fetal imagers reviewing the MRI studies. These experienced reviewers scored location of the mass in the craniocaudal axis and in the transverse axis. MRI reviewers also scored the presence of inferior cardiac compression by the lesion and whether there was identifiable thymic tissue. Reviewer disagreements were resolved by consensus review. RESULTS: Eleven pericardial teratomas and 10 mediastinal teratomas were identified. All cases underwent detailed fetal anatomic US and fetal echocardiogram and 10/11 (91%) pericardial teratomas and 8/10 (80%) mediastinal teratomas underwent fetal MRI. Median volume was higher for mediastinal teratomas compared to pericardial teratomas (42.5 mL [interquartile range (IQR) 15.9 - 67.2 mL] vs. 8.1 mL [IQR 7.7 - 27.7 mL], P=0.01) and median volume/head circumference was also statistically higher in mediastinal teratomas (1.33 [IQR 0.78 - 2.61] vs. 0.43 [IQR 0.38 - 1.10], P=0.01). Logistic regression analysis demonstrated a statistical difference between teratoma types with respect to location in the craniocaudal axis by both modalities with mediastinal teratomas more commonly located in the upper and upper-middle thorax compared to pericardial teratomas, which were more commonly found in the middle thorax (US, P=0.03; MRI, P=0.04). Logistic regression analysis also demonstrated a statistical difference between teratoma types with respect to position along the transverse axis by both modalities with mediastinal teratomas more commonly located midline or left paramedian and pericardial teratomas more often right paramedian in location (US, P<0.01; MRI, P=0.02). Inferior cardiac compression observed by MRI was associated more commonly with mediastinal teratomas compared to pericardial teratomas (87.5% [7/8] vs. 10% [1/10], P<0.01). Identifiable thymus by MRI was more commonly observed in cases of pericardial teratomas, however, this difference was not statistically significant (P=0.32). CONCLUSION: Mediastinal teratomas are associated with larger lesion size and inferior cardiac compression when compared to pericardial teratomas. These features combined with lesion location in the craniocaudal and transverse axes may allow for more accurate prenatal diagnosis and optimal perinatal and surgical management.

The fetal lamb model of congenital diaphragmatic hernia shows altered cerebral perfusion using contrast enhanced ultrasound.

BACKGROUND: Neurodevelopmental impairment is common in survivors of congenital diaphragmatic hernia (CDH). Altered cerebral perfusion in utero may contribute to abnormal brain development in CDH patients. METHODS: 5 fetal lambs with surgical left-CDH and 5 controls underwent transuterine cranial Doppler and contrast enhanced ultrasound (CEUS). Global and regional perfusion metrics were obtained. Biometric and perfusion data were compared between groups via nonparametric Mann Whitney U test and Spearman's rank order correlation. RESULTS: No significant differences in cerebral Doppler measurements were identified between groups. By CEUS, CDH animals demonstrated significantly decreased global brain perfusion and increased transit time. With focal regions-of-interest (ROIs), there was a tendency towards decreased perfusion in the central/thalamic region in CDH but not in the peripheral brain parenchyma. Transit time was significantly increased in both ROIs in CDH, whereas flux rate was decreased in the central/thalamic region but not the peripheral brain parenchyma. Biometric CDH severity was correlated to perfusion deficit. There was no difference in cardiomyocyte histology. CONCLUSION: The fetal lamb model of CDH shows altered cerebral perfusion as measured by CEUS, correlating to disease severity. This suggests a physiological abnormality in fetal cerebrovascular perfusion that may contribute to abnormal brain development and neurodevelopmental impairment in survivors.

Neonatal gastrointestinal emergencies: a radiological review.

BACKGROUND: Abdominal emergencies in neonates require surgical management in almost all cases and complications may include bowel perforation, sepsis, shock, and even death. Radiological imaging has become a very important aid in the clinical setting as it shortens time to diagnosis. OBJECTIVE: The objective of this review is to discuss the more prevalent neonatal gastrointestinal emergencies, review appropriate imaging options, and illustrate common radiological presentations of these entities. CONCLUSION: Despite advancements in imaging techniques, it is important to keep in mind that neonates have a higher susceptibility to the adverse effects of ionizing radiation, and therefore radiography and ultrasonography remain the main diagnostic modalities for ruling out the diseases with the worst prognosis. Other modalities (fluoroscopy, computed tomography, and magnetic resonance imaging) may have limited use in very specific conditions. All providers in an emergency department should be familiar with the basic radiological findings that may indicate a gastrointestinal emergency, especially in health institutions that do not have 24-h radiologist coverage.

Contrast-enhanced ultrasound: a comprehensive review of safety in children.

Contrast-enhanced ultrasound (CEUS) has been increasingly used in pediatric radiology practice worldwide. For nearly two decades, CEUS applications have been performed with the off-label use of gas-containing second-generation ultrasound contrast agents (UCAs). Since 2016, the United States Food and Drug Administration (FDA) has approved the UCA Lumason for three pediatric indications: the evaluation of focal liver lesions and echocardiography via intravenous administration and the assessment of vesicoureteral reflux via intravesical application (contrast-enhanced voiding urosonography, ceVUS). Prior to the FDA approval of Lumason, numerous studies with the use of second-generation UCAs had been conducted in adults and children. Comprehensive protocols for clinical safety evaluations have demonstrated the highly favorable safety profile of UCA for intravenous, intravesical and other intracavitary uses. The safety data on CEUS continue to accumulate as this imaging modality is increasingly utilized in clinical settings worldwide. As of August 2021, 57 pediatric-only original research studies encompassing a total of 4,518 children with 4,906 intravenous CEUS examinations had been published. As in adults, there were a few adverse events; the majority of these were non-serious, although very rarely serious anaphylactic reactions were reported. In the published pediatric-only intravenous CEUS studies included in our analysis, the overall incidence rate of serious adverse events was 0.22% (10/4,518) of children and 0.20% (10/4,906) of all CEUS examinations. Non-serious adverse events from the intravenous CEUS were observed in 1.20% (54/4,518) of children and 1.10% (54/4,906) of CEUS examinations. During the same time period, 31 studies with the intravesical use of UCA were conducted in 12,362 children. A few non-serious adverse events were encountered (0.31%; 38/12,362), but these were most likely attributable to the bladder catheterization rather than the UCA. Other developing clinical applications of UCA in children, including intracavitary and intralymphatic, are ongoing. To date, no serious adverse events have been reported with these applications. This article reviews the existing pediatric CEUS literature and provides an overview of safety-related information reported from UCA uses in children.

Translational research in pediatric contrast-enhanced ultrasound.

The role of contrast-enhanced ultrasound (CEUS) imaging is being widely explored by various groups for its use in the pediatric population. Clinical implementation of new diagnostic or therapeutic techniques requires extensive and meticulous preclinical testing and evaluation. The impact of CEUS will be determined in part by the extent to which studies are oriented specifically toward a pediatric population. Rather than simply applying principles and techniques used in the adult population, these studies are expected to advance and augment preexisting knowledge with pediatric-specific information. To further develop this imaging modality for use in children, pediatric-focused preclinical research is essential. In this paper we describe the development and implementation of the pediatric-specific preclinical animal and phantom models that are being used to evaluate CEUS with the goal of clinical translation to children.

Emerging contrast-enhanced ultrasound applications in children.

Ultrasound contrast agent (UCA) use in radiology is expanding beyond traditional applications such as evaluation of liver lesions, vesicoureteral reflux and echocardiography. Among emerging techniques, 3-D and 4-D contrast-enhanced ultrasound (CEUS) imaging have demonstrated potential in enhancing the accuracy of voiding urosonography and are ready for wider clinical adoption. US contrast-based lymphatic imaging has been implemented for guiding needle placement in MR lymphangiography in children. In adults, intraoperative CEUS imaging has improved diagnosis and assisted surgical management in tumor resection, and its translation to pediatric brain tumor surgery is imminent. Because of growing interest in precision medicine, targeted US molecular imaging is a topic of active preclinical research and early stage clinical translation. Finally, an exciting new development in the application of UCA is in the field of localized drug delivery and release, with a particular emphasis on treating aggressive brain tumors. Under the appropriate acoustic settings, UCA can reversibly open the blood-brain barrier, allowing drug delivery into the brain. The aim of this article is to review the emerging CEUS applications and provide evidence regarding the feasibility of these applications for clinical implementation.

Contrast-enhanced ultrasound of the pediatric brain.

Brain contrast-enhanced ultrasound (CEUS) is an emerging application that can complement gray-scale US and yield additional insights into cerebral flow dynamics. CEUS uses intravenous injection of ultrasound contrast agents (UCAs) to highlight tissue perfusion and thus more clearly delineate cerebral pathologies including stroke, hypoxic-ischemic injury and focal lesions such as tumors and vascular malformations. It can be applied not only in infants with open fontanelles but also in older children and adults via a transtemporal window or surgically created acoustic window. Advancements in CEUS technology and post-processing methods for quantitative analysis of UCA kinetics further elucidate cerebral microcirculation. In this review article we discuss the CEUS examination protocol for brain imaging in children, current clinical applications and future directions for research and clinical uses of brain CEUS.

Contrast-Enhanced Brain Ultrasound Perfusion Metrics in the EXTra-Uterine Environment for Neonatal Development (EXTEND): Correlation With Hemodynamic Parameters.

OBJECTIVES: Contrast-enhanced ultrasound (CEUS) can provide quantitative perfusion metrics and may be useful to detect cerebral pathology in neonates and premature infants, particularly in extrauterine environments. The effect of hemodynamics on cerebral perfusion metrics is unknown, which limits the clinical application of this technology. We aimed to determine associations between systemic hemodynamics and concurrently measured brain perfusion parameters in an animal model of extrauterine support. METHODS: Nine fetal lambs were transferred to an extrauterine support device. Lumason® ultrasound contrast (0.1-0.3 ml) was administered via the umbilical vein and 90-second cine clips were obtained. Time-intensity-curves (TICs) were generated and time-dependent and area-under-curve (AUC) parameters were derived. Associations between brain perfusion metrics and hemodynamics including heart rate (HR) and mean arterial pressure (MAP) were evaluated by multilevel linear mixed-effects models. RESULTS: Eighty-six ultrasound examinations were performed and 72 examinations were quantifiable. Time-dependent measurements were independent of all hemodynamic parameters (all p ≥.05). Oxygen delivery and mean blood flow were correlated with AUC measurements (all p ≤.01). Physiologic HR and MAP were not correlated with any measurements (all p ≥.05). CONCLUSION: Detected aberrations in time-dependent CEUS measurements are not correlated with hemodynamic parameters and are thought to reflect the changes in cerebral blood flow, thus providing a promising tool for evaluation of brain perfusion. CEUS brain perfusion parameters are not correlated with physiologic HR and MAP, but AUC-dependent measurements are correlated with oxygen delivery and blood flow, suggesting that CEUS offers additional value over standard monitoring. Overall, these findings enhance the applicability of this technology.

Quantitative contrast-enhanced ultrasound of the brain on twin fetal lambs maintained by the extrauterine environment for neonatal development (EXTEND): initial experience.

BACKGROUND: With the development of an artificial environment to support the extremely premature infant, advanced imaging techniques tested in this extrauterine system might be beneficial to evaluate the fetal brain. OBJECTIVE: We evaluated the feasibility of (a) performing contrast-enhanced ultrasound (CEUS) and (b) quantifying normal and decreased brain perfusion in fetal lambs maintained on the extrauterine environment for neonatal development (EXTEND) system. MATERIALS AND METHODS: Twin premature fetal lambs (102 days of gestational age) were transferred to the EXTEND system. Twin B was subjected to sub-physiological flows (152 mL/kg/min) and oxygen delivery (15.9 mL/kg/min), while Twin A was maintained at physiological levels. We administered Lumason contrast agent into the oxygenator circuit and performed serial CEUS examinations. We quantified perfusion parameters and generated parametric maps. We also recorded hemodynamic parameters, serum blood analysis, and measurements across the oxygenator. Postmortem MRIs were performed. RESULTS: No significant changes in hemodynamic variables were attributable to CEUS examinations. On gray-scale images, Twin B demonstrated ventriculomegaly and progressive parenchymal volume loss culminating in hydranencephaly. By CEUS, Twin B demonstrated decreased peak enhancement and decreased overall parenchymal perfusion when compared to Twin A by perfusion parameters and parametric maps. Changes in perfusion parameters were detected immediately following blood transfusion. Postmortem MRI confirmed ultrasonographic findings in Twin B. CONCLUSION: In this preliminary experience, we show that CEUS of the brain is feasible in fetal lambs maintained on the EXTEND system and that changes in perfusion can be quantified, which is promising for the application of CEUS in this extrauterine system supporting the premature infant.

Fetoscopic insufflation modeled in the extrauterine environment for neonatal development (EXTEND): Fetoscopic insufflation is safe for the fetus.

BACKGROUND: Minimally invasive fetal surgery, or fetoscopy, is an alternative to open fetal surgery to repair common birth defects like myelomeningocele. Although this hysterotomy-sparing approach reduces maternal morbidity, the effects of in utero insufflation on the fetus are poorly understood. Our purpose was to determine the optimal fetal insufflation conditions. METHODS: Fetal sheep at gestational age 104 to 107 days were studied under insufflation conditions in utero and ex utero. The ex utero fetuses were cannulated via their umbilical vessels into a support device, the EXTra-uterine Environment for Neonatal Development (EXTEND). EXTEND fetuses were exposed to four different insufflation conditions for four hours: untreated carbon dioxide (CO2) (n=5), warm humidified (whCO2) (n=4), whCO2 with the umbilical cord exposed (n=3), and whCO2 without amniotic fluid (skin and cord exposed) (n=3). RESULTS: In utero insufflation led to significant increases in fetal CO2 and reductions in fetal pH. Ex utero insufflation with whCO2 did not lead to changes in fetal blood gas measurements or cerebral perfusion parameters. Insufflation with whCO2 with an exposed umbilical cord led to reduced umbilical blood flow. CONCLUSIONS: Insufflation with warm humidified CO2 with an amniotic fluid covered umbilical cord is well tolerated by the fetus without significant changes in hemodynamics or cerebral perfusion parameters. TYPE OF STUDY: Basic science LEVEL OF EVIDENCE: N/A.

Pediatric contrast-enhanced ultrasound: optimization of techniques and dosing.

When performing contrast-enhanced ultrasound (CEUS), ultrasound (US) scanner settings, examination technique, and contrast agent dose and administration must be optimized to ensure that high-quality, diagnostic and reproducible images are acquired for qualitative and quantitative interpretations. When carrying out CEUS in children, examination settings should be tailored to their body size and specific indications, similar to B-mode US. This review article details the basic background knowledge that is needed to perform CEUS optimally in children, including considerations related to US scanner settings and US contrast agent dose selection and administration techniques.

Two's Company: Multiple Thoracic Lesions on Prenatal US and MRI.

BACKGROUND: Congenital pulmonary airway malformations (CPAM), bronchopulmonary sequestrations (BPS), and CPAM-BPS hybrid lesions are most commonly solitary; however, >1 lung congenital lung lesion may occur. OBJECTIVES: To assess the frequency of multiple congenital thoracic anomalies at a high-volume referral center; determine prenatal ultrasound (US) and magnetic resonance imaging (MRI) features of these multifocal congenital lung lesions that may allow prenatal detection; and determine the most common distribution or site of origin. METHODS: Database searches were performed from August 2008 to May 2019 for prenatally evaluated cases that had a final postnatal surgical diagnosis of >1 congenital lung lesion or a lung lesion associated with foregut duplication cyst (FDC). Lesion location, size, echotexture, and signal characteristics were assessed on prenatal imaging and correlated with postnatal computed tomographic angiography and surgical pathology. -Results: Of 539 neonates that underwent surgery for a thoracic lesion, 35 (6.5%) had >1 thoracic abnormality. Multiple discrete lung lesions were present in 19 cases, and a lung lesion associated with an FDC was present in 16. Multifocal lung lesions were bilateral in 3 cases; unilateral, multilobar in 12; and, unilobar multisegmental in 4. Median total CPAM volume/head circumference ratio for multifocal lung lesions on US was 0.66 (range, 0.16-1.80). Prenatal recognition of multifocal lung lesions occurred in 7/19 cases (36.8%). Lesion combinations were CPAM-CPAM in 10 cases, CPAM-BPS in 5, CPAM-hybrid in 2, hybrid-hybrid in 1, and hybrid-BPS in 1. Of 5 unilateral, multifocal lung lesions, multifocality was prenatally established through identification of a band of normal intervening lung or intrinsic differences in lesion imaging features. CONCLUSIONS: Although less common, multiple thoracic abnormalities can be detected prenatally. Of multifocal lung lesions, the most common combination was CPAM-CPAM, with a unilateral, multilobar distribution. Prenatal recognition is important for pregnancy counseling and postnatal surgical management.

Neurologic outcomes of the premature lamb in an extrauterine environment for neonatal development.

BACKGROUND/PURPOSE: Neurologic injury remains the most important morbidity of prematurity. Those born at the earliest gestational ages can face a lifetime of major disability. Perinatal insults result in developmental delay, cerebral palsy, and other profound permanent neurologic impairments. The EXTracorporeal Environment for Neonatal Development (EXTEND) aims to transition premature neonates through this sensitive period, but it's impact on neurologic development requires analysis. METHODS: Fetal sheep were maintained in a fluid-filled environment for up to 28 days. Physiologic parameters were measured continuously; tissues were subsequently fixed and preserved for myelin quantification, glial cell staining, and structural assessment via magnetic resonance. Surviving animals were functionally assessed. RESULTS: No evidence of fetal brain ischemia or white matter tract injury associated with the EXTEND system was detected, and the degree of myelination was regionally appropriate and consistent with age matched controls. No evidence of neurologic injury or immaturity was visible on magnetic resonance; animals that transitioned from the system had no persistent neurologic deficits. CONCLUSIONS: No evidence of major neurologic morbidity was found in animals supported on the EXTEND system, though more work needs to be done in order to verify its safety during critical periods of neurologic development.

Ex Utero Extracorporeal Support as a Model for Fetal Hypoxia and Brain Dysmaturity.

BACKGROUND: Congenital heart disease (CHD) is associated with abnormal fetal brain development, a phenomenon that may be related to decreased cerebral oxygen delivery in utero. We used an artificial womb model to test the hypothesis that decreasing fetal oxygen delivery would reproduce physiologic changes identified in fetuses with CHD. METHODS: Experimental (hypoxemic) fetal lambs (mean gestational age, 111 ± 3 days; n = 4) and control animals (112 days; n = 5) were maintained in the artificial womb for a mean of 22 ± 6 days. Oxygen delivery was reduced to 15.6 ± 1.0 mL/kg/min in the hypoxemia animals versus 21.6 ± 2.0 mL/kg/min in the control animals. Blood chemistry analysis and sonographic evaluation were performed daily. An additional control group (n = 7) was maintained in utero and harvested for analysis at gestational age 134 ± 4 days. RESULTS: Physiologic variables were monitored continuously, and no statistical differences between the groups were identified. Fetal oxygen delivery and arterial partial pressure of oxygen were remarkably lower in the experimental group longitudinally. Increased umbilical artery and decreased middle cerebral artery resistance resulted in a lower cerebral to umbilical resistance ratio, similar to the brain sparing effect observed in human fetuses with CHD. Experimental brains were smaller than control brains in relation to the calvarium on magnetic resonance. CONCLUSIONS: Sustained hypoxemia in fetal sheep leads to altered cerebrovascular resistances and loss of brain mass, similar to human fetuses with CHD. This unique model provides opportunities to investigate the pathologic process underlying CHD-associated brain dysmaturity and to evaluate potential fetal neuroprotective therapies.

Novel Computerized Analytic Technique for Quantification of Amniotic Fluid Volume in Fetal MRI.

OBJECTIVE. Fetal MRI is increasingly used in the evaluation of suspected congenital anomalies. Assessment of amniotic fluid volume (AFV) is crucial, but no automated quantitative technique is currently available for MRI. The purpose of this study was to develop and evaluate an analytic technique for quantifying AFV in fetal MRI. MATERIALS AND METHODS. Two MRI phantoms containing known quantities of synthetic amniotic fluid were created. A 3D steady-state free precession sequence was used for 1.5-T MRI of the phantoms and as part of a standard clinical fetal MRI protocol. Software was developed and used to retrospectively calculate AFV for the phantom and 20 clinical MRI examinations. Times to completion were recorded. AFV was also calculated by a manual hand-tracing method. To evaluate performance, paired t tests were used to compare computer-generated measurements with known phantom volumes. Intraclass correlation coefficients were calculated to assess agreement between computer-generated and manual measurements. RESULTS. There was no significant difference between computer-generated measurements of known AFV in the MRI phantoms (p > 0.11). When the software program was applied to the clinical MRI examinations, the mean time to complete AFV measurement was 110 seconds. There was excellent reliability between total AFV calculated by the two software users and by means of manual measurements (intraclass correlation coefficient, 0.995; p < 0.01). CONCLUSION. The computerized analysis evaluated in this study rapidly and accurately quantifies AFV in fetal MRI. The results are concordant with known phantom volumes and manual measurements. The technique is promising for objective MRI evaluation of AFV and has the potential to improve prenatal diagnosis and management.