The developing role of fetal magnetic resonance imaging in the diagnosis of congenital cardiac anomalies: A systematic review

Fetal Organ Anomaly Classification Network for Identifying Organ Anomalies in Fetal MRI

Rapid development in Magnetic Resonance Imaging (MRI) has played a key role in prenatal diagnosis over the last few years. Deep learning (DL) architectures can facilitate the process of anomaly detection and affected-organ classification, making diagnosis more accurate and observer-independent. We propose a novel DL image classification architecture, Fetal Organ Anomaly Classification Network (FOAC-Net), which uses squeeze-and-excitation (SE) and naïve inception (NI) modules to automatically identify anomalies in fetal organs. This architecture can identify normal fetal anatomy, as well as detect anomalies present in the (1) brain, (2) spinal cord, and (3) heart. In this retrospective study, we included fetal 3-dimensional (3D) SSFP sequences of 36 participants. We classified the images on a slice-by-slice basis. FOAC-Net achieved a classification accuracy of 85.06, 85.27, 89.29, and 82.20% when predicting brain anomalies, no anomalies (normal), spinal cord anomalies, and heart anomalies, respectively. In a comparison study, FOAC-Net outperformed other state-of-the-art classification architectures in terms of class-average F1 and accuracy. This work aims to develop a novel classification architecture identifying the affected organs in fetal MRI.

A Dedicated 36-Channel Receive Array for Fetal MRI at 3T

Due to a lack of fetal imaging coils, the standard commercial abdominal coil is often used for fetal imaging, the performance of which is limited by its insufficient coverage, element number, and Signal-to-noise ratio (SNR). In this paper, a dedicated 36-channel coil array, of which size can best fit the body sizes of pregnancy gestation from 20 to 37+ weeks, was designed for fetal imaging at 3T. SNR with full phase encoding and G-factor denoted as noise amplification for parallel imaging were quantitatively evaluated by phantom studies. Compared with a commercial abdominal coil array, the proposed 36-channel fetal array provides not only SNR improvements in full phase encoding (with 10% in the region where the whole fetal body was located, and up to 40% in the edge region where the fetal brain and heart may appear) but also an augmented parallel imaging capability and remarkable SNR improvements at high acceleration factors.

Factors influencing bacteraemia in patients with isomerism and CHD: the effects of functional splenic status and antibiotic prophylaxis

BACKGROUND

"Heterotaxy syndrome", best segregated as isomerism, is characterised by laterality defects of the thoraco-abdominal organs, causing functional impairment. In particular, the spleen is frequently affected, increasing susceptibility to bacteraemia. This study explored factors that may increase the risk of bacteraemia in patients with isomerism.

METHODS

We identified patients with CHD and isomerism. Review of outpatient, inpatient, and surgical records was conducted to collect data and determine trends in the cohort. A Cox regression analysis was conducted to determine factors influencing freedom from bacteraemia (Fig 1).

RESULTS

We identified 83 patients with CHD and isomerism - 17 (20%) who had documented episodes of bacteraemia with a total of 21 episodes. A majority (86%) were nosocomial. The median age at the time of bacteraemia was 4 months. Although splenic anatomy did appear to influence the risk of bacteraemia in univariate analysis, this significance was lost with multivariate analysis. None of the other factors was significantly associated in either univariate or multivariate analysis.

CONCLUSION

Specific factors such as splenic anatomy, atrial appendage isomerism, and antibiotic prophylaxis status are not significantly associated with the risk of bacteraemia in patients with CHD and isomerism. Nosocomial infections represent a majority of bacteraemia in these patients.

Fetal cardiac cine imaging using highly accelerated dynamic MRI with retrospective motion correction and outlier rejection

PURPOSE

Development of a MRI acquisition and reconstruction strategy to depict fetal cardiac anatomy in the presence of maternal and fetal motion.

METHODS

The proposed strategy involves i) acquisition and reconstruction of highly accelerated dynamic MRI, followed by image-based ii) cardiac synchronization, iii) motion correction, iv) outlier rejection, and finally v) cardiac cine reconstruction. Postprocessing entirely was automated, aside from a user-defined region of interest delineating the fetal heart. The method was evaluated in 30 mid- to late gestational age singleton pregnancies scanned without maternal breath-hold.

RESULTS

The combination of complementary acquisition/reconstruction and correction/rejection steps in the pipeline served to improve the quality of the reconstructed 2D cine images, resulting in increased visibility of small, dynamic anatomical features. Artifact-free cine images successfully were produced in 36 of 39 acquired data sets; prolonged general fetal movements precluded processing of the remaining three data sets.

CONCLUSIONS

The proposed method shows promise as a motion-tolerant framework to enable further detail in MRI studies of the fetal heart and great vessels. Processing data in image-space allowed for spatial and temporal operations to be applied to the fetal heart in isolation, separate from extraneous changes elsewhere in the field of view. Magn Reson Med 79:327-338, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Neonatal management and outcomes of prenatally diagnosed CHDs

OBJECTIVES

The aim of this study was to determine the probability of intervention at birth after prenatal diagnosis of CHD.

METHODS

A 10-year retrospective study including all foetuses with a prenatally diagnosed CHD and those delivered in a tertiary-care cardiac centre between January, 2002 and December, 2011 was carried out. Patients were classified into eight groups according to the anticipated risk of neonatal intervention.

RESULTS

The need for urgent intervention and/or PGE1 infusion within the first 48 hours of life was 47% (n=507/1080): 72% (n=248) for CHD at risk for a Rashkind procedure, 77% (n=72) for CHD with ductal-dependent pulmonary flow, 13% (n=22) for CHD with potentially ductal-dependent pulmonary flow, 94% (n=62) for CHD with ductal-dependent systemic flow, 29% (n=88) for CHD with potentially ductal-dependant systemic flow, 50% (n=4) for total anomalous pulmonary venous connection, and 17% (n=1) for CHD with atrio-ventricular block. In all, 34% of the patients received PGE1 infusion and 21.4% underwent urgent catheter-based or surgical interventions; 10% of patients without anticipated risk (n=10) underwent an early intervention; 6.7% (n=73) of the patients died; and 55% (n=589) had an intervention before discharge from hospital.

CONCLUSION

Half of the neonates with foetal CHD benefited from an urgent intervention or PGE1 infusion at birth. We recommend scheduled delivery and in utero transfer for transposition of the great arteries, double-outlet right ventricle with sub-pulmonary ventricular septal defect, total anomalous pulmonary venous connection, CHD with atrio-ventricular block with heart rate <50, all ductal-dependant lesions, and CHD with potentially ductal-dependant systemic flow.

Characteristics of Hospitalizations for the Glenn Procedure in Those With Isomerism Compared to Those Without

Isomerism, also known as heterotaxy, is a unique clinical entity in which there are mirror imaged findings in the thoracic. In the abdomen, the arrangement of organs can be random. The anatomic findings also have functional consequences. Isomerism has been known to increase morbidity and mortality in those with functionally univentricular hearts. The aim of this study was to determine the impact of isomerism on the Glenn hospitalization. Data from the 1997 to 2012 Kids' Inpatient Database were utilized for this cross-sectional study. Admissions during which a Glenn procedure was done were identified. Next, these admissions were separated into those with and without isomerism. Admission characteristics were then compared in a univariate fashion as well as by regression analysis. Length of hospitalization, cost of hospitalization, extracorporeal membrane oxygenation, and inpatient mortality were the outcomes of interest. A total of 4959 admissions with a Glenn procedure were identified. Of these, 450 were associated with isomerism. The median age at which the Glenn procedure was done was 10 and 13 months in those without and with isomerism, respectively. Neither univariate nor regression analysis demonstrated any significant difference in length of hospitalization, cost of hospitalization, need for extracorporeal membrane oxygenation, and inpatient mortality between those with and without isomerism. Isomerism does not impact the characteristics of the Glenn hospitalization. Those with isomerism did tend to be older when they underwent the Glenn procedure.

Evolution of ventricular outpouching through the fetal and postnatal periods: Unabating dilemma of serial observation or surgical correction

Ventricular outpouching is a rare finding in prenatal sonography and the main differential diagnoses are diverticulum, aneurysm, and pseudoaneurysm in addition to congenital cysts and clefts. The various modes of fetal presentation of congenital ventricular outpouching include an abnormal four-chamber view on fetal two-dimensional echocardiogram, fetal arrhythmia, fetal hydrops, and pericardial effusion. Left ventricular aneurysm (LVA)/nonapical diverticula are usually isolated defects. Apical diverticula are always associated with midline thoracoabdominal defects (epigastric pulsating diverticulum or large omphalocele) and other structural malformations of the heart. Most patients with LVA/congenital ventricular diverticulum remain clinically asymptomatic but they can potentially give rise to complications such as ventricular tachyarrhythmias, systemic embolism, sudden death, spontaneous rupture, and severe valvular regurgitation. The treatment of asymptomatic LVA and isolated congenital ventricular diverticulum is still undefined. In this review, our aim is to outline a systematic approach to a fetus detected with ventricular outpouching. Starting with prevalence and its types, issues in fetal management, natural course and evolution postbirth, and finally the perpetual dilemma of serial observation or surgical correction is discussed.

Radiologic Considerations in Heterotaxy: The Need for Detailed Anatomic Evaluation

So-called "heterotaxy" is a laterality defect characterized by isomerism of the thoracic organs and random arrangement of the abdominal organs. These findings go beyond anatomic curiosity and have functional implications. It is, thus, of the utmost importance to be able to properly identify these findings. Radiologic studies can be invaluable in determining anomalies in the central nervous, pulmonary, cardiovascular, gastrointestinal, genitourinary, and immunologic systems in patients with isomerism. Here, we review findings associated with isomerism and their importance in the setting of isomerism with the aim of ensuring that radiologists effectively describe findings in these patients and that cardiologists understand the wide variety of congenital malformations that may be present.

Fetal Magnetic Resonance Imaging of Malformations Associated with Heterotaxy

Magnetic resonance imaging (MRI) is increasingly used as an investigation during fetal life, particularly for assessment of intracranial masses, congenital diaphragmatic hernia, myelomeningocele, and abdominal masses. As the number of scans increases, so is the variety of congenital malformations being recognized. It is axiomatic that interpretation of the findings is enhanced when attention is paid to the likely findings in the setting of known syndromes, this information then dictating the need for additional acquisition of images. One such syndrome is so-called "visceral heterotaxy", in which there is typically an isomeric, rather than a lateralized, arrangement of the thoracic and abdominal organs. Typically associated with complex congenital cardiac malformations, heterotaxy can also involve the central nervous system, and produce pulmonary, gastrointestinal, immunologic, and genitourinary malformations. In this review, we discuss how these findings can be demonstrated using fetal MRI.

Pattern-based approach to fetal congenital cardiovascular anomalies using the transverse aortic arch view on prenatal cardiac MRI

Fetal echocardiography is the imaging modality of choice for prenatal diagnosis of congenital cardiovascular anomalies. However, echocardiography has limitations. Fetal cardiac magnetic resonance imaging (MRI) has the potential to complement US in detecting congenital cardiovascular anomalies. This article draws on our experience; it describes the transverse aortic arch view on fetal cardiac MRI and important clues on an abnormal transverse view at the level of the aortic arch to the diagnosis of fetal congenital cardiovascular anomalies.

Preliminary experience with cardiovascular magnetic resonance in evaluation of fetal cardiovascular anomalies

BACKGROUND

The cardiovascular system is the part of the fetal anatomy that most frequently suffers from congenital pathology. This study shows our preliminary experience with fetal cardiovascular magnetic resonance (CMR) to evaluate congenital cardiovascular abnormalities.

METHODS

Between January 2006 and June 2011, Prenatal routine obstetric ultrasound (US), echocardiography and CMR data from 68 pregnant women carrying fetuses with congenital cardiovascular anomalies were compared with postnatal diagnoses (postnatal imagings, surgery and autopsy). All prenatal CMR was performed at 1.5 T. Imaging sequences included steady-state free-precession (SSFP) sequences, real-time SSFP and single-shot turbo spin echo (SSTSE) sequences. The images were analyzed with an anatomic segmental approach by two radiologists.

RESULTS

Fetal CMR yielded the same diagnosis as postnatal findings in 79% (54/68) of patients. The diagnostic sensitivity of routine obstetric US for cardiac anomalies was 46% (31/68). The diagnostic sensitivity of fetal echocardiographic examination by a fetal cardiac specialist was 82% (56/68). In 2 (3%) of 68 cases, diagnoses with both echocardiography and CMR were incorrect when compared with postnatal diagnosis. In ten (15%) cases, diagnosis at echocardiography was incorrect and that at CMR was correct. In twelve (18%) cases, diagnosis at echocardiography was correct and that at CMR was incorrect. Ten cases missed or misdiagnosed by echocardiography but correctly diagnosed by fetal CMR included asplenia syndrome (n = 2), interrupted inferior vena cava of polysplenia syndrome (n = 1), tricuspid incompetence (n = 1), double outlet right ventricle (n = 2), double aortic arch (n = 1), right pulmonary artery hypoplasia (n = 1), right-sided aortic arch of tetralogy of Fallot (n = 1) and hypoplastic left heart syndrome of a twin fetus (n = 1).

CONCLUSION

Fetal CMR is a promising diagnostic tool for assessment of congenital cardiovascular abnormalities, especially in situations that limit echocardiography.

Dynamic imaging of the fetal heart using metric optimized gating

PURPOSE

Advances in fetal cardiovascular magnetic resonance imaging have been limited by the absence of a reliable cardiac gating signal. The purpose of this work was to develop and validate metric-optimized gating (MOG) for cine imaging of the fetal heart.

THEORY AND METHODS

Cine MR and electrocardiogram data were acquired in healthy adult volunteers for validation of the MOG method. Comparison of MOG and electrocardiogram reconstructions was performed based on the image quality for each method, and the difference between MOG and electrocardiogram trigger times. Fetal images were also acquired, their quality evaluated by experienced radiologists, and the theoretical error in the MOG trigger times were calculated.

RESULTS

Excellent agreement between electrocardiogram and MOG reconstructions was observed. The experimental errors in adult MOG trigger times for all five volunteers were ± (7, 25, 17, 8, and 13) ms. Fetal images captured normal and diseased cardiac dynamics.

CONCLUSION

MOG for cine imaging of the fetal myocardium was developed and validated in adults. Using MOG, the first gated MR images of the human fetal myocardium were obtained. Small moving structures were visualized during radial contraction, thus capturing normal fetal cardiac wall motion and permitting assessment of cardiac function.

Multimodality Imaging in Congenital Heart Disease: an Update

The increasing number of survivors of congenital heart disease (CHD) has been paralleled by advancement of imaging modalities used for the ongoing assessment of these patients. There has been a large body of literature describing new approaches to non-invasive assessment of CHD. We will review new applications of well established as well as novel techniques for the management and understanding of CHD.