Three-dimensional magnetic resonance imaging of the postmortem fetal heart

Utility of a modified vascular corrosion casting technique in the diagnosis of fetal total anomalous pulmonary venous connection

Total anomalous pulmonary venous connection (TAPVC) is a rare congenital cardiac malformation, and prenatal detection of TAPVC malformation remains a challenging. TAPVC can be easily missed or misdiagnosed in prenatal examinations. This study was aimed to use the modified vascular corrosion casting technique to prepare fetal cardiovascular casts with TAPVC and investigate the utility of cardiovascular casting for the demonstration of fetal TAPVC. The retrospective study enrolled twenty fetuses (22 to 29 + 4 gestational weeks) with TAPVC diagnosed by prenatal echocardiography and casting technique from May 2015 to May 2020. Pre- and postnatal medical records, including results obtained by prenatal ultrasound, postpartum computed tomography angiography, as well as anatomic and cardiovascular casting findings were carefully reviewed and analyzed. In twenty cases, 80% (16/20) had intra- or extracardiac malformations. The TAPVC types were supracardiac (n = 8), cardiac (n = 6), infracardiac (n = 4), and mixed (n = 2). The diagnosis of 1 case each of supracardiac and cardiac TAPVC was modified to partial anomalous pulmonary venous connection; additionally, 4 malformations were missed and 2 were misdiagnosed, including an anomalous left brachiocephalic vein in supracardiac TAPVC, abnormal inflow of the hepatic vein and a double inferior vena cava in infracardiac TAPVC; and bilateral ductus arteriosus in infracardiac TAPVC; a tetralogy of Fallot in cardiac TAPVC that was corrected to right ventricular double outlet; and an absence of ductus arteriosus that was misdiagnosed as slim ductus arteriosus. Comparing with ultrasound, casting technique has its own superiority in exhibiting TAPVC abnormalities, especially in certain types such as course, origin and absence abnormalities of ductus. Postpartum cardiovascular casts can accurately depict the branch structure of the heart's larger vessels, and may be used as a clinical assessment and teaching method in complex cardiac malformations.

Fetal postmortem imaging: an overview of current techniques and future perspectives

Fetal death because of miscarriage, unexpected intrauterine fetal demise, or termination of pregnancy is a traumatic event for any family. Despite advances in prenatal imaging and genetic diagnosis, conventional autopsy remains the gold standard because it can provide additional information not available during fetal life in up to 40% of cases and this by itself may change the recurrence risk and hence future counseling for parents. However, conventional autopsy is negatively affected by procedures involving long reporting times because the fetal brain is prone to the effect of autolysis, which may result in suboptimal examinations, particularly of the central nervous system. More importantly, fewer than 50%-60% of parents consent to invasive autopsy, mainly owing to the concerns about body disfigurement. Consequently, this has led to the development of noninvasive perinatal virtual autopsy using imaging techniques. Because a significant component of conventional autopsy involves the anatomic examination of organs, imaging techniques such as magnetic resonance imaging, ultrasound, and computed tomography are possible alternatives. With a parental acceptance rate of nearly 100%, imaging techniques as part of postmortem examination have become widely used in recent years in some countries. Postmortem magnetic resonance imaging using 1.5-Tesla magnets is the most studied technique and offers an overall diagnostic accuracy of 77%-94%. It is probably the best choice as a virtual autopsy technique for fetuses >20 weeks' gestation. However, for fetuses <20 weeks' gestation, its performance is poor. The use of higher magnetic resonance imaging magnetic fields such as 3-Tesla may slightly improve performance. Of note, in cases of fetal maceration, magnetic resonance imaging may offer diagnoses in a proportion of brain lesions wherein conventional autopsy fails. Postmortem ultrasound examination using a high-frequency probe offers overall sensitivity and specificity of 67%-77% and 74%-90%, respectively, with the advantage of easy access and affordability. The main difference between postmortem ultrasound and magnetic resonance imaging relates to their respective abilities to obtain images of sufficient quality for a confident diagnosis. The nondiagnostic rate using postmortem ultrasound ranges from 17% to 30%, depending on the organ examined, whereas the nondiagnostic rate using postmortem magnetic resonance imaging in most situations is far less than 10%. For fetuses ≤20 weeks' gestation, microfocus computed tomography achieves close to 100% agreement with autopsy and is likely to be the technique of the future in this subgroup. The lack of histology has always been listed as 1 limitation of all postmortem imaging techniques. Image-guided needle tissue biopsy coupled with any postmortem imaging can overcome this limitation. In addition to describing the diagnostic accuracy and limitations of each imaging technology, we propose a novel, stepwise diagnostic approach and describe the possible application of these techniques in clinical practice as an alternative or an adjunct or for triage to select cases that would specifically benefit from invasive examination, with the aim of reducing parental distress and pathologist workload. The widespread use of postmortem fetal imaging is inevitable, meaning that hurdles such as specialized training and dedicated financing must be overcome to improve access to these newer, well-validated techniques.

Description of misdiagnosis and missed diagnosis of fetal complex heart malformations by prenatal echocardiography combined with postnatal cardiovascular casting

OBJECTIVE

To compare prenatal echocardiography with postnatal cardiovascular casting for detection of fetal cardiovascular malformations, and to discuss the causes of prenatal misdiagnosis and missed diagnosis.

METHODS

We retrospectively identified patients from 2013 to 2018 at our Maternal-Fetal Medicine Center who were reported to have a fetal diagnosis of severe congenital heart malformations (CHMs). Subjects had postnatal confirmation of CHMs. Prenatal and postnatal medical records, including ultrasound results and casting findings, were reviewed and analyzed.

RESULTS

Postnatal casting showed that all 35 fetuses had complex CHMs. In these 35 cases, 90 cardiovascular malformations were found by postnatal casting, and 69 were detected by prenatal echocardiography. Among the other 21 cardiovascular malformations, 7 were misdiagnosed and 14 diagnoses were missed by prenatal ultrasound.

CONCLUSION

Prenatal echocardiography may lead to misdiagnosis and missed diagnoses, especially in cases with great arterial branching anomalies. Postnatal casting can demonstrate the configuration of the great vessels and smaller branches directly. Thus, understanding of such malformations via postnatal casting may help to improve prenatal diagnostic accuracy.

Conventional vs virtual autopsy with postmortem MRI in phenotypic characterization of stillbirths and fetal malformations

OBJECTIVE

To compare virtual autopsy using postmortem magnetic resonance imaging (MRI) with conventional autopsy with respect to phenotypic characterization of stillbirths and malformed fetuses, and acceptability to parents.

METHODS

This was a prospective diagnostic evaluation study, conducted from June 2013 to June 2015, including stillbirths and pregnancies terminated owing to fetal malformation at ≥ 20 weeks' gestation, for which parental consent to both conventional autopsy and postmortem MRI was obtained. Cases of maternal and obstetric cause of fetal demise were excluded. Whole-body postmortem MRI (at 1.5 T) was performed prior to conventional autopsy. Taking conventional autopsy as the diagnostic gold standard, postmortem MRI findings alone, or in conjunction with other minimally invasive prenatal and postmortem investigations, were assessed and compared for diagnostic accuracy.

RESULTS

Parental consent for both conventional autopsy and postmortem MRI was obtained in 52 cases of which 43 were included in the analysis. In 35 (81.4%) cases, the final diagnosis based on virtual autopsy with postmortem MRI was in agreement with that of conventional autopsy. With conventional autopsy as the reference standard, sensitivity, specificity, positive and negative predictive values of postmortem MRI were, respectively: 77.7%, 99.8%, 97.4% and 98.0% for whole-body assessment; 93.1%, 99.0%, 87.1% and 99.5% for the nervous system; 61.0%, 100.0%, 100.0% and 96.7% for the cardiovascular system; 91.1%, 100.0%, 100.0% and 98.0% for the pulmonary system; 80.6%, 99.8%, 96.7% and 98.7% for the abdomen; 96.2%, 99.7%, 96.2% and 99.7% for the renal system; and 66.7%, 100.0%, 100.0% and 97.2% for the musculoskeletal system. Virtual autopsy was acceptable to 96.8% of families as compared with conventional autopsy to 82.5%.

CONCLUSIONS

Virtual autopsy using postmortem MRI and other minimally invasive investigations can be an acceptable alternative to conventional autopsy when the latter is refused by the parents. Postmortem MRI is more acceptable to parents and can provide additional diagnostic information on brain and spinal cord malformations. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

The use of magnetic resonance in the hospital and coronial pediatric postmortem examination

The role of magnetic resonance imaging (MRI) has rapidly progressed from being a research tool to an ancillary pre-autopsy imaging technique and now an adjunct of the postmortem (PM) examination. In this review, we describe our experience with the use of PM MRI over the last 6 years in more than 300 fetal PM examinations, initially as research and finally the most recent use in 30 pediatric coronial autopsies. The pediatric pathologist and the neonatal and fetal radiologist retrospectively measured the impact on diagnosis at each stage of the development of the technique together. All imaging techniques have the advantage of being non-invasive, more acceptable to the public, especially certain religious groups and provide a permanent record of the features observed.

Post mortem magnetic resonance imaging in the fetus, infant and child: a comparative study with conventional autopsy (MaRIAS Protocol)

Background

Minimally invasive autopsy by post mortem magnetic resonance (MR) imaging has been suggested as an alternative for conventional autopsy in view of the declining consented autopsy rates. However, large prospective studies rigorously evaluating the accuracy of such an approach are lacking. We intend to compare the accuracy of a minimally invasive autopsy approach using post mortem MR imaging with that of conventional autopsy in fetuses, newborns and children for detection of the major pathological abnormalities and/or determination of the cause of death.

Methods/Design

We recruited 400 consecutive fetuses, newborns and children referred for conventional autopsy to one of the two participating hospitals over a three-year period. We acquired whole body post mortem MR imaging using a 1.5 T MR scanner (Avanto, Siemens Medical Solutions, Enlargen, Germany) prior to autopsy. The total scan time varied between 90 to 120 minutes. Each MR image was reported by a team of four specialist radiologists (paediatric neuroradiology, paediatric cardiology, paediatric chest & abdominal imaging and musculoskeletal imaging), blinded to the autopsy data. Conventional autopsy was performed according to the guidelines set down by the Royal College of Pathologists (UK) by experienced paediatric or perinatal pathologists, blinded to the MR data. The MR and autopsy data were recorded using predefined categorical variables by an independent person.

Discussion

Using conventional post mortem as the gold standard comparator, the MR images will be assessed for accuracy of the anatomical morphology, associated lesions, clinical usefulness of information and determination of the cause of death. The sensitivities, specificities and predictive values of post mortem MR alone and MR imaging along with other minimally invasive post mortem investigations will be presented for the final diagnosis, broad diagnostic categories and for specific diagnosis of each system.

Clinical Trial Registration

NCT01417962

NIHR Portfolio Number: 6794

Current applications of fetal cardiac imaging technology

PURPOSE OF REVIEW

Over the last few years, great progress has been made in imaging technology, which is changing the way prenatal visualization of the fetal heart is used for diagnosis and therapy.

RECENT FINDINGS

This paper reviews recent clinical research using these new techniques, namely dynamic three-dimensional (4D) echocardiography, myocardial Doppler imaging, B-flow ultrasonography, endoscopic ultrasound, and magnetic resonance imaging. Of them, 4D echocardiography is the most significant development and is discussed in greater detail. This includes real-time volumetric data acquisition using matrix-array transducer technology, motion artefact elimination using spatio-temporal image correlation, and various display options. The advantages and limitations of each are also addressed.

SUMMARY

These techniques can provide (1) sequential assessment of the entire heart using a full 4D dataset, (2) 4D delineation of trabeculation patterns on the ventricular walls, en-face dynamic shapes of ventricular septal defects and spatially complex malformations, (3) derivation of cardiac indices to myocardial contractility and strain rate by Doppler tissue imaging, and/or (4) the use of transoesophageal ultrasound to guide in-utero cardiac intervention. All of these techniques expand our ability to evaluate the morphology and function of the in-utero heart.

MRI in fetal necropsy

The fetal autopsy involves a series of investigations of the corpse, most of which are noninvasive and acceptable to the majority of parents and their physicians. The value of the perinatal autopsy is manyfold and well established, and the results can provide a basis for parental and family counseling, inform future obstetric management, and provide audit for prenatal care. Many techniques originally developed for diagnosis, such as histology, biochemical tests, photography, x-rays, and cytogenetic karyotyping, have become standard tools in perinatal autopsies. However, there has been an inexorable decline in the autopsy consent rate over the last 30 years due to social and cultural factors, and perhaps ignorance of the benefits to be derived from the examination. Growing evidence suggests that postmortem fetal MRI can assist the pathologist at autopsy, and in many cases can obviate the need for dissection or at least minimize and focus it. For the majority of cases in which no consent for surgical autopsy is given, MRI together with other noninvasive postmortem tests can provide a great deal of the information that was previously available only from autopsy.

Use of a confidence scale in reporting postmortem fetal magnetic resonance imaging

OBJECTIVES

Postmortem magnetic resonance imaging (MRI) may be an alternative to conventional autopsy. However, it is unclear how confident radiologists are in reporting such studies. We sought to determine the confidence with which radiologists report on various fetal organs by developing a scale to express their confidence of normality and abnormality, and to place this in the context of a pathological diagnosis of whether the organ was in fact normal or abnormal.

METHODS

Thirty fetuses, aged 16-39 gestational weeks and weighing 61-3270 g, underwent postmortem MRI prior to conventional autopsy. MRI studies were reported by two radiologists with access to the clinical and sonographic history: a neuroradiologist, reporting head and neck, and a pediatric radiologist, reporting thorax, abdomen and pelvis. Radiologists used a scale (0 = definitely abnormal, 100 = definitely normal, 50 = unable to comment) to indicate their confidence of anatomical structures being normal or abnormal, using a checklist. Conventional autopsies were performed by pediatric pathologists blinded to the MRI findings, and these were considered the reference standard.

RESULTS

Most normal fetal organs had high scores on postmortem MRI, with median confidence scores above 80. However, the atrioventricular valves, duodenum, bowel rotation and pancreas proved more difficult to assess, with median scores of 50, 60, 60 and 62.5, respectively. Abnormal cardiac atria and ventricles, kidneys, cerebral hemispheres and corpus callosum were always detected with high or moderate degrees of confidence (median scores of 2.5, 5, 0, 0 and 30 respectively). However, in two cases with abnormal cardiac outflow tracts, both cases scored 50. Kappa values, assessing agreement between MRI diagnoses of abnormality and autopsy, were high for the brain (0.83), moderate for the lungs (0.56) and fair for the heart (0.33).

CONCLUSIONS

This scoring system represents an attempt to define the confidence of radiologists to report varying degrees of normality and abnormality following z ex-utero fetal MRI. While most fetal anatomy is clearly visualized on postmortem MRI, radiologists may lack confidence reporting such studies and there are particular problems with assessment of some cardiac and gastrointestinal structures, both normal and abnormal.

Three-dimensional MRI of the male urethrae with implanted artificial sphincters: initial results

The aim of this study was to develop a method for simultaneous 3D visualization of a new type of artificial urethral sphincter (AUS) and adjacent urinary structures. Serial MR tomograms were acquired from seven men after AUS implantation. 3D reconstruction was performed by thresholding original (positive) and inverted (negative) image intensity and by subsequently fusing positive and negative images. Results show that the bladder, cuff and balloons of the AUS of originally high intensity were imaged in 3D by thresholding the positive datasets. The urethrae and corpora cavernosa penis of originally low intensity were displayed in 3D by thresholding the negative datasets. Fusion of the positive and negative datasets allowed simultaneous visualization of the AUS complex and adjacent urinary structures. All the structures of interest were also clearly seen by interactive multiplanar reformatting. Coronal tomographic datasets provided better 3D and reformatted 2D images than sagittal and transverse datasets. This technique offers a simple means for evaluating the complex urethral anatomy and the AUS, and has potential for improved 3D visualization of many other complex morphological and pathological conditions.

Investigating perinatal death: a review of the options when autopsy consent is refused

Autopsy remains the best method of investigating perinatal deaths. Recent years have, however, seen a decline in autopsy rates. This review looks at some of the options available for investigating perinatal deaths when the family decline to give consent for standard autopsy.

New fetal cardiac imaging techniques

Rapid advances in graphics computing and micro-engineering have offered new techniques for prenatal cardiac imaging. Some of them can be non-invasively applied to both clinical and laboratory settings, including dynamic three-dimensional echocardiography, myocardial Doppler imaging, harmonic ultrasound imaging, and B-flow sonography. With clinical constraints, a few others have been mainly used in laboratories, such as endoscopic ultrasound, magnetic resonance imaging and biomicroscopy. Appropriate use and co-use of these new tools will not only provide unique information for better clinical assessment of fetal cardiac disease but also offer new ways to improved understanding of cardiovascular development and pathogenesis.

Fetus and uteroplacental unit: fast MR imaging with three-dimensional reconstruction and volumetry--feasibility study

In 22 fetuses, three-dimensional reconstruction was performed on the basis of T2-weighted magnetic resonance (MR) data sets by using a surface-rendering technique. Fetuses and uteroplacental units were segmented manually; volumes were calculated automatically. Three-dimensional reconstruction and volumetry of the fetus and uteroplacental unit are feasible with MR data sets. MR estimates correlated closely with ultrasonographic fetal biometric estimates and birth weight.

Simultaneous use of two ultrasound scanners for motion-gated three-dimensional fetal echocardiography

The aim of this study was to determine whether or not simultaneous use of an additional Doppler transducer could provide sufficient cardiovascular motion information without significantly interfering with three-dimensional (3-D) cardiac structural data acquisition by a primary two-dimensional (2-D) transducer. To determine sources of interference, paired transducers were activated alternatively and simultaneously in and out of a water bath, with and without electrical insulating and electromagnetic shielding. To determine factors affecting interference, pairs were tested on a phantom with different separating distances and angles between paired ultrasound (US) beams and under different 2-D depths and Doppler scales. Results show that the dominant source of interference is acoustic cross talk. The severity was mainly affected by transducer pairing and by separating distances and angles, and the pattern by display settings. With optimised settings, sufficient structural and motion data were obtained simultaneously in 9 of 12 fetal hearts, and detailed 3-D views could be reconstructed free of motion artefacts, confirming the feasibility of using the method for motion-gated 3-D fetal cardiac imaging. New scanner design strategy was then proposed.

Novel fetal imaging techniques

Fetal imaging technology is evolving rapidly, and new techniques are being evaluated to establish their role in the assessment of the fetus. It is essential that these methods of fetal imaging are carefully assessed to ascertain if they provide additional information to assist in the clarification or understanding of fetal disease states that is not already provided by current conventional imaging techniques.