The value of fetal magnetic resonance imaging in diagnosis of congenital anomalies of the fetal body: a systematic review and meta-analysis

OBJECTIVES

To undertake a systematic review to assess the accuracy of fetal MRI in diagnosis of non-CNS congenital anomalies of the fetal body in comparison with antenatal ultrasound when correlated to postnatal diagnosis.

METHODS

Searches were conducted from electronic databases, key journals and reference lists for eligible papers. Inclusion criteria was original research studies comparing the diagnostic results of antenatal ultrasound, fetal MRI and final postnatal diagnosis via imaging, surgery or post-mortem testing. Studies of CNS anomalies were excluded. Studies were assessed for risk of bias by two reviewers working independently and data was then extracted by a single reviewer.

RESULTS

12 studies were included with a total of 361 eligible patients who underwent USS and MRI and had a postnatal diagnosis. USS alone had a diagnostic accuracy of 60.6% whereas MRI had an improved diagnostic accuracy of 86.4%. The overall odds ratio was 0.86 (CI 0.202-1.519 and p-value < 0.01).

CONCLUSION

Fetal MRI makes a significant contribution to accurate diagnosis of congenital abnormalities of the fetal body; especially in genito-urinary anomalies. More research is needed to improve the evidence base for the role of fetal MRI in diagnosis of congenital anomalies in other body systems.

MRI prediction of fetal lung volumes and the impact on counselling

AIM

To assess whether lung volume percentages in congenital diaphragmatic hernia (CDH) differ depending on which formula is used to calculate the expected volume for gestation and any potential impact this may have on perinatal counselling.

MATERIALS AND METHODS

Forty-seven patients with left-sided CDH who had undergone fetal magnetic resonance imaging (MRI) at Sheffield Teaching Hospitals were reviewed. The lung volumes were measured on MRI and compared with the volumes that would be expected at the given gestation for each patient. Expected values were calculated using four formulae from the literature and the authors' in-house method. These measurements were used to calculate the percentage total lung volume observed compared with the expected lung volume in a healthy fetus of the same gestation. The differences in percentage lung volumes using these five methods were then compared with how they relate to predicted rates of survival. How predicted survival would change depending on which formula was used to calculate the percentage lung volume was investigated with a view to how this may change the counselling given to a family.

RESULTS

In 10/47 (21%) patients, there was no change in the predicted percentage chance of survival depending on which formula was used to calculate the predicted lung volume. In 37/47 (79%), the predicted chance of survival changed depending on which formula was used to calculate the expected lung volume at the given gestation. In 20 (47%) of these cases, the change in predicted survival depending on which formula used was 45% (i.e., from 25% to 70% survival in four and from 50% to 95% survival in 16) and in two cases (4%) this difference was 70% (i.e., from 25% predicted survival to 95% predicted survival).

CONCLUSION

There are several different methods for calculating expected lung volumes for any given gestation. When used to estimate the percentage lung volume in patients with CDH, there is a large difference in values depending on which method is used. This in turn leads to a large variation in predicted survival with some patients in this study having either a 25% or 95% chance of survival depending on which method is used. This has a huge impact on perinatal counselling and the difficult decisions made by families.

Robert's uterus (asymmetric septate uterus): a rare congenital Müllerian duct anomaly

Müllerian anomalies such as Robert's uterus, which was first described by the French gynaecologist Dr Helene Robert in 1969, are rare clinical entities and have been reported in <3% of the female population. Robert's uterus is a rare phenomenon with a relative dearth of reported cases. Affected individuals may present with pelvic pain and dysmenorrhoea that intensifies near menses or acutely, with severe abdominal pain to the emergency department. They are also associated with adverse pregnancy outcomes, abnormal fetal presentation, preterm labour, recurrent pregnancy loss and infertility. Although ultrasound has a role in its initial assessment, MRI is the best modality to further delineate its anatomy. It is typically managed via laparotomy and total horn resection, endometrectomy of the blind cavity or abdominal metroplasty. The authors present the case of a 40-year-old woman at 19+3 weeks gestation with acute onset of left-sided abdominal pain. A transvaginal ultrasound and MRI of the pelvis confirmed a Robert's uterus with a viable pregnancy in the upper left horn. She developed a ruptured horn with significant haemoperitoneum. An emergency laparotomy was performed and a non-viable fetus was evident. Only a few cases of pregnancy in the blind hemicavity have been reported so far. This case also highlights the importance of considering this diagnosis in young females presenting with dysmenorrhoea and normal menstrual flow. It is imperative to render a prompt diagnosis, as minimally invasive procedures may be more effective if detected before the formation of adnexal endometriomas.

Benefits and Limitations of the Minimally Invasive Postmortem: A Review of an Innovative Service Development

INTRODUCTION

Pediatric postmortem (PM) rates have significantly declined, creating a need for effective minimally invasive alternatives to correlate with parental wishes. We review the use of a minimally invasive fetal and neonatal PM service further to preliminary findings published in 2015.

MATERIALS AND METHODS

Cases taken from the mortuary electronic database from 2012 to 2017 are analyzed. The minimally invasive service consisted primarily of external examination, magnetic resonance imaging (MRI), and placental examination. Any significant conditions found noted. All pathology reports include a Relevant Condition at Death (ReCoDe) obstetric classification. Reports analyzed to determine which aspects of the service provided positive information.

RESULTS

Of 1498 perinatal postmortems, 105 (7%) were PM MRI, of which 75.24% were intrauterine fetal deaths. Relevant conditions were identified in 94 cases (89.52%), and ReCoDe categories in 80 cases (76.19%). Moreover, 90% of cases had a ReCoDe condition, with 10% unclassified. Seven cases had more than 1 ReCoDe. Main conditions related to placenta (32.5%) and umbilical cord (27.5%). The most informative elements were placental examination and MRI.

CONCLUSION

Minimally invasive PMs are a viable alternative to traditional autopsy when this option is refused. However, further case analysis is needed to determine potential bias toward certain classification codes.

ESPR postmortem imaging task force: where we begin

A new task force on postmortem imaging was established at the annual meeting of the European Society of Paediatric Radiology (ESPR) in Graz, Austria, in 2015. The postmortem task force is separate from the child abuse task force as it covers all aspects of fetal, neonatal and non-forensic postmortem imaging. The main focus of the task force is the guidance and standardization of non-radiographic postmortem imaging, particularly postmortem CT and postmortem MRI. This manuscript outlines the starting point of the task force, with a mission statement, outline of current experience, and short- and long-term goals.

Initial experiences of a minimally invasive autopsy service. A report of the techniques and observations in the first 11 cases

Our goal was to set up a clinical service for minimally invasive postmortem examination for the fetal and neonatal age group. The minimally invasive service consisted of imaging, external review, placental examination, and ancillary tests that form part of the formal autopsy process. Eleven patients had imaging and relevant conditions at death successfully determined with the minimally invasive service. We conclude that a minimally invasive autopsy service for fetal and neonatal cases is possible and acceptable to patients and professionals.

Diffusion-weighted imaging and magnetic resonance proton spectroscopy following preterm birth

AIM

To study the associations between magnetic resonance proton spectroscopy (MRS) data and apparent diffusion coefficients (ADC) from the preterm brain with developmental outcome at 18 months corrected age and clinical variables.

MATERIALS AND METHODS

A prospective observational cohort study of 67 infants born before 35 weeks gestational age who received both magnetic resonance imaging of the brain between 37 and 44 weeks corrected gestational age and developmental assessment around 18 months corrected age.

RESULTS

No relationships were found between ADC values and MRS results or outcome. MRS ratios involving N-acetyl aspartate (NAA) from the posterior white matter were associated with "severe" and "moderate to severe" difficulties, and fine motor scores were significantly lower in participants with a visible lactate doublet in the posterior white matter. The presence of a patent ductus arteriosus (PDA) was the only clinical factor related to NAA ratios.

CONCLUSION

Altered NAA levels in the posterior white matter may reflect subtle white matter injury associated with neuro-developmental difficulties, which may be related to a PDA. Further work is needed to assess the longer-term neuro-developmental implications of these findings, and to study the effect of PDAs on developmental outcome in later childhood/adolescence.

CT of the neonatal head

Computed tomography (CT) is used less often than other techniques on neonatal units. However, in the acute setting, CT can be invaluable in diagnosing or excluding potentially life-threatening conditions and guiding initial management in neonates. Common indications for scanning include trauma, suspected non-accidental injury, infection, or an acute hypoxic or metabolic event. The aim of this review is to provide an overview of the normal neonatal head at CT and compare this to the common pathological abnormalities. Several key features of each condition will be highlighted. It is important to note that some pathological conditions can have overlapping features at CT and, therefore, the clinical history and additional investigations are also of key importance in determining the diagnosis.

Recurrent pseudo-TORCH appearances of the brain presenting as "Dandy-Walker" malformation

Dandy-Walker malformation (DWM) is a developmental abnormality characterized by cystic dilatation of the fourth ventricle, complete or partial agenesis of the cerebellar vermis, and enlarged posterior fossa with upward displacement of the lateral sinuses, tentorium, and torcula. Calcification of brain tissue is a feature of congenital infection, particularly those involving the TORCH ( Toxoplasma gondii , rubella virus, Cytomegalovirus, and herpesvirus) group. An autosomal-recessive congenital infection-like syndrome with intracranial and extracranial calcifications has been categorized as pseudo-TORCH syndrome. We describe two male siblings diagnosed as DWM by ultrasound and by in utero and postmortem magnetic resonance imaging (MRI) but in whom the neuropathology revealed features of intracranial necrosis and calcification in the absence of extracranial calcific deposition. The fetal anomaly was identified by routine prenatal ultrasound scan at 16 weeks. In both cases the postmortem MRI showed bilateral ventriculomegaly with distortion of the overlying cortices, enlarged posterior fossa with a cyst related to small cerebellar hemispheres, and an incomplete cerebellar vermis. The diagnosis of DWM was offered. The histology revealed hypoplastic cerebral hemispheres with poorly cellular developing cortex. The white matter and periventricular matrix were disrupted by areas of necrosis and calcification not associated with any inflammatory infiltration, organisms, inclusions, or giant cells. To our knowledge, these two male siblings are the 1st cases that show pseudo-TORCH syndrome with distinctive intracranial calcification presenting as DWM. An autosomal-recessive or X-linked inheritance needs to be considered. Our study confirms the relevance of the multidisciplinary teamwork involved in the diagnosis of these complex cases.

Is There a Causal Relationship Between Open Spinal Dysraphism and Chiari II Deformity?

BACKGROUND:

Chiari II deformity is associated with open spinal dysraphism. A causal relationship has been proposed by McLone and Knepper. This article evaluates that hypothesis.

OBJECTIVE:

To establish the frequency of Chiari II deformity in fetuses with open spinal dysraphism, assess whether meningocele sac neck area and volume influence the severity of posterior fossa changes, and assess whether the severity of associated findings (ventriculomegaly, amount of extracerebral CSF) are associated with Chiari II deformity.

METHODS:

Sixty-five fetuses with open spinal dysraphism were compared with gestationally aged matched “normal” fetuses on ultrafast MR images. Cerebellar vermis and bony posterior fossa surface area were measured on midline sagittal images. Hindbrain herniation was noted if present. In the open spinal dysraphic group, sac neck area and volume were measured. Ventriculomegaly was assessed by linear measurement of the trigone of the lateral ventricle and extracerebral CSF depth was measured maximally over the lateral surface of the cerebral hemispheres.

RESULTS:

Fifteen of 65 fetuses with open spinal dysraphism did not have Chiari II deformity. Neck area and volume of the sac did not correlate with the presence of Chiari II deformity or reduction in bony posterior fossa size.

CONCLUSION:

A relatively high proportion of fetuses with open spinal dysraphism do not have Chiari II deformity in utero. There is a lack of correlation between indicators of spinal dysraphism severity and the extent of the posterior fossa abnormality. This raises some interesting questions about the causality of the Chiari II deformity.

Magnetic resonance imaging of the fetus

Fetal magnetic resonance imaging (MRI) has become established as part of clinical practice in many centres worldwide especially when visualization of the central nervous system pathology is required. In this review we summarize the recent literature and provide an overview of fetal development and the commonly encountered fetal pathologies visualized with MRI and illustrated with numerous MR images. We aim to convey the role of fetal MRI in clinical practice and its value as an additional investigation alongside ultrasound yet emphasize the need for caution when interpreting fetal MR images especially where experience is limited.

Fetuses with ventriculomegaly diagnosed in the second trimester of pregnancy by in utero MR imaging: what happens in the third trimester?

BACKGROUND AND PURPOSE

Although MR imaging of the fetal brain has been shown to provide additional diagnostic information, the optimal timing of the study and the value of repeat studies remain unclear. The primary purpose of this study was to look for structural abnormalities of the fetal brain shown at 30-32 weeks' gestational age but not on the 20-24 weeks' study in fetuses originally referred with isolated VM. In particular, we wished to study the hypothesis that third-trimester fetal MR imaging studies would not show extra brain abnormalities compared with the second-trimester studies in this group.

MATERIALS AND METHODS

Ninety-nine women were admitted for a fetal MR study between 20-24 weeks' gestational age, and 46 of these women agreed to return for a second MR imaging examination at 30-32 weeks' gestational age. The other women were either lost to follow-up or declined the invitation to return. Two experienced observers measured the width of the trigones, and the results were compared, to test reliability. Changes in the degree of VM are reported along with changes in the diagnosis of structural brain abnormalities.

RESULTS

There was excellent reproducibility of trigone measurements between the 2 observers, with a mean absolute difference of <1 mm in the 40 fetuses that were ultimately shown to have isolated VM. Twenty-eight of 40 fetuses studied had mild VM on the first iuMR imaging examination, but in just more than half, the category of VM changed between the studies (5 had become normal-sized, 7 had progressed to moderate, 3 had become severe, and 13 remained mild). In 1 case, hypogenesis of the corpus callosum was recognized at 30-32 weeks but had not been reported on the 20-24 weeks' examination; the other 5 fetuses had brain pathology recognized on both fetal MR studies.

CONCLUSIONS

Trigone measurements can be made in a highly repeatable fashion on iuMR imaging. We have not shown any major advantage in repeating iuMR imaging at 30-32 weeks' gestation in terms of improved diagnosis of other structural brain abnormalities. With the converse of that argument, however, our data suggest that there is no advantage in delaying iuMR imaging studies to 30-32 weeks in the hope of improving detection rates.

Neonatal cochlear function: measurement after exposure to acoustic noise during in utero MR imaging

PURPOSE

To establish whether fetal exposure to the operating noise of 1.5-T magnetic resonance (MR) imaging is associated with cochlear injury and subsequent hearing loss in neonates.

MATERIALS AND METHODS

The study was performed with local research ethics committee approval and written informed parental consent. Neonatal hearing test results, including otoacoustic emission (OAE) data, were sought for all neonates delivered in Sheffield who had previously undergone in utero MR imaging between August 1999 and September 2007. The prevalence of hearing impairment in these neonates was determined, with corresponding 95% confidence intervals calculated by using the binomial exact method, and mean OAE measurements were compared with anonymized local audiometric reference data by using the t test.

RESULTS

One hundred three neonates who had undergone in utero MR imaging were identified; 96 of them had completed hearing screening assessment. Thirty-four of these babies were admitted to the neonatal intensive care unit (NICU), and one of them had bilateral hearing impairment. The prevalence of hearing impairment was 1% (one of 96; 95% confidence interval: 0.03%, 5.67%), which is in accordance with the prevalence expected, given the high proportion of babies in this study who had been in the NICU (ie, NICU graduates). In addition, for the well babies, there was no significant difference in mean OAE cochlear response compared with that for a reference data set of more than 16,000 OAE results. When NICU graduates were included in the comparison, a significant difference (P = .002) was found in one of four frequency bands used to analyze the cochlear response; however, this difference was small compared with the normal variation in OAE measurements.

CONCLUSION

The findings in this study provide some evidence that exposure of the fetus to 1.5-T MR imaging during the second and third trimesters of pregnancy is not associated with an increased risk of substantial neonatal hearing impairment.

Diffusion-weighted imaging of cerebral white matter and the cerebellum following preterm birth

AIM

The aim of this study was to determine if apparent diffusion coefficients (ADCs) generated with diffusion-weighted imaging of cerebral white matter and the cerebellum are affected by white matter damage.

METHOD

Seventy-two preterm infants (32 males, 40 females; mean gestational age at birth 30.3 wks, SD 3.0 wks; mean birthweight 1458g, SD 534g) underwent magnetic resonance imaging of the brain around term-equivalent age and were categorized into three groups: normal, overt abnormality, and diffuse excessive high signal intensity (DEHSI). ADC values were calculated from cerebral white matter, cerebellar hemispheres, and cerebellar midline, and were compared between groups. Regression analysis identified clinical parameters correlated with ADC values.

RESULTS

Imaging was normal in 27 infants, and revealed overt abnormalities in 14 and DEHSI in 31. ADC values did not differ between groups. ADC values from cerebral white matter were negatively correlated with the number of episodes of postnatal sepsis (p=0.002). ADC values from cerebellar hemispheres (p=0.007) and cerebellar midline (p=0.036) correlated with gestational age at birth.

INTERPRETATION

ADC values from white matter are not altered in preterm infants with DEHSI but are negatively correlated with the number of episodes of postnatal sepsis. ADC values in the cerebellum are not altered by white matter damage, but are affected by preterm birth itself.

A prospective study of fetuses with isolated ventriculomegaly investigated by antenatal sonography and in utero MR imaging

BACKGROUND AND PURPOSE

Fetal ventriculomegaly (VM) is important because of its high prevalence and high risk of association with other brain abnormalities. The purpose of this article was to investigate the hypotheses that including in utero MR imaging (iuMR) in the diagnostic pathway for fetuses with isolated VM on antenatal imaging will show other brain abnormalities in a high proportion of cases and that these will have a significant effect on clinical management.

MATERIALS AND METHODS

One hundred forty-seven pregnant women were recruited prospectively from 8 fetomaternal centers in Britain. All of the fetuses had VM diagnosed on sonography but no other abnormality. iuMR was performed, and the results of the examinations were compared with those of sonography. Two fetomaternal experts made independent assessments of the effects of any new diagnoses on clinical management.

RESULTS

Categoric assessments of ventricular size were the same in approximately 90% of fetuses. Other abnormalities were shown in 17% of fetuses. The most frequent additional brain abnormality shown on iuMR was agenesis of the corpus callosum. Severe VM was associated with an approximately 10-fold increase in the risk of another brain abnormality being present when compared with fetuses with mild VM. The most profound effects on clinical management, however, were found in cases of mild VM.

CONCLUSIONS

This work supports our hypotheses by showing a high detection rate of other brain pathology when iuMR was used to supplement antenatal sonography (17%). In a high proportion of cases, the detection of the extra pathology would have led to significant changes in clinical management.

Cranial vault defects: the description of three cases that illustrate a spectrum of anomalies

Three cases of cranial vault defects in fetuses are described. All 3 cases underwent postmortem examination, and in 2 of them postmortem magnetic resonance imaging was also performed. The phenotypical differences between the cases illustrate a spectrum of cranial vault defects, associated anomalies, and pathogenic mechanisms involved in the etiology of this rare malformation. All 3 cases were male, and the cranial vault defects corresponded to exencephaly with acrania/acalvaria caused by amniotic band syndrome, acalvaria, and acrania presenting in a chorangiopagus parasiticus twin.

Less invasive autopsy: benefits and limitations of the use of magnetic resonance imaging in the perinatal postmortem

The decline in the postmortem (PM) autopsy rate in the United Kingdom paralleled the change in public perception of this procedure after the organ retention crisis in 2000. The introduction of magnetic resonance imaging (MRI) in the fetal, perinatal, and pediatric autopsy led some investigators to propose that MRI could replace the conventional PM. We assessed the role of MRI in fetal autopsy as an addition or a potential replacement method to the conventional PM and to evaluate the benefits and limitations of each technique. We retrospectively reviewed the PM and MRI examination of 100 fetuses. The MRI was limited to the brain or brain and spinal cord. Forty-six cases involved termination of pregnancy; 30 were intrauterine fetal deaths/stillbirths; 16 were premature deliveries followed by neonatal death; and 8 were miscarriages. The mean gestational age of all cases was 25.54 weeks (range: 13-41 weeks). In 54 of the 90 full PMs, there was a complete agreement between the MRI and autopsy findings on the morphology of the brain and spine. Despite this agreement, the information gained at the PM was relevant to find the cause or mechanism of death in 20 of 54 cases (37%). In 24 autopsies the MRI added valuable information to the autopsy. However, if MRI had been the only investigation, essential information would have been lost in 17 of 24 cases (71%). In 12 cases the PM was clearly superior to the MRI. The integrated result obtained from the traditional autopsy remains crucial in determining the cause or mechanism of the malformation or of the fetal/perinatal death and accordingly is important for the counseling offered to parents regarding the recurrence risk for future pregnancies.

SNR phase order k-space encoding (SPOKE)

A method of determining the phase-encode order for MR Fourier-encoded imaging is described, which provides an additional option for optimizing images from samples with signals that change during data acquisition. Examples are in hyperpolarized helium gas imaging of the lungs where polarization is lost with each RF pulse or the signal changes observed in rapid dynamic studies with T(1) or T(2)* contrast agents when mixing is taking place. The method uses a single frequency-encoded projection in the proposed phase-encoding direction. The projection is subsequently sorted into signal-to-noise ratio (SNR) order. The indices of the sorted array are then used to create the phase-encode table to be used for the scan. This phase table is sorted in descending SNR order for signals that decrease during data acquisition and in ascending order for signals that increase during data acquisition. Simulations suggest that this technique can produce higher resolution than centric-ordered phase encoding at the expense of increased modulation (ghosting) artifact for dynamically changing signals. Initial practical implementation of the technique has been carried out on a dedicated 0.2-T Niche MR system, and the test object results agree well with simulations. Hyperpolarized 3-He lung images have also been acquired and postprocessed using the SNR phase order k-space encoding (SPOKE) methodology and show potential for improved imaging with high flip angles where polarization is rapidly lost. Applications may also be found for 3D volumetric acquisitions where two dimensions can be SPOKE encoded.

The value of in-utero magnetic resonance imaging in ultrasound diagnosed foetal isolated cerebral ventriculomegaly

AIM

To assess whether magnetic resonance imaging (MRI) is a useful adjunct to ultrasound (US) when imaging cases of foetal isolated cerebral ventriculomegaly. To assess whether, in such cases, ventricular morphology is a useful indicator for the underlying pathology, as has recently been suggested.

MATERIALS AND METHODS

A retrospective analysis was undertaken of 30 cases of isolated ventriculomegaly diagnosed using US and referred for in utero MRI. The gestational age of each case was noted and the MRI report. Both ventricles were measured and each case was categorized according to severity and morphology. The MRI report was compared to the final diagnosis.

RESULTS

Of the 30 cases evaluated 18 had mild ventriculomegaly (<15 mm; gestational age range 20-31 weeks, mean 22.8, median 22) and 12 had severe ventriculomegaly (>15 mm; gestational age range 21-37 weeks, mean 28, median 28.5). Additional abnormalities were found in 50% of cases overall (44% mild, 58% severe) using MRI.

CONCLUSIONS

Using MRI additional abnormalities were identified in 50% of the foetuses. The morphology of the cases did not suggest underlying pathology in this group. In utero MRI is a useful adjunct to US in cases of foetal cerebral ventriculomegaly referred after initial diagnosis using US.

Imaging the fetal spine using in utero MR: diagnostic accuracy and impact on management

BACKGROUND

In-utero MR imaging (iuMR) has entered the clinical arena during the last decade. It is used mainly for imaging fetal brain abnormalities.

OBJECTIVE

To report our experience of imaging the fetal spine and spinal cord in fetuses with known or suspected abnormalities diagnosed on US imaging.

MATERIALS AND METHODS

Prospective imaging and retrospective analysis of the possible impact on management of 50 consecutive fetuses with spinal abnormalities detected by antenatal US imaging.

RESULTS

In 40 (80%) of 50 fetuses, iuMR and US imaging were in complete agreement. In the other 10 fetuses (20%), iuMR provided additional information or changed the diagnosis, including 8 fetuses where the iuMR could find no abnormality and was found to be correct by later follow-up.

CONCLUSION

IuMR is useful in fetuses with a suspected spinal abnormality. The clinical impact of iuMR may be numerically less than with brain abnormalities, but is still sufficient to warrant its use, especially if there is any uncertainty about the US imaging, and particularly as a relatively high proportion of diagnoses on US imaging are false-positives.

Post-mortem MRI of the foetal spine and spinal cord

AIMS

To compare the findings of post-mortem magnetic resonance imaging (MRI) of the foetal spine with autopsy with a view to using post-mortem MRI as an alternative or adjunct to autopsy, particularly in foetal and neonatal cases.

MATERIALS AND METHODS

The brains and spines of 41 foetuses, with a gestational age range of 14-41 weeks, underwent post-mortem MRI before autopsy. Post-mortem MRI of the brain consisted of T2-weighted sequences in three orthogonal planes and MRI of the spine consisted of T2-weighted sequence in the sagittal and axial planes in all cases and coronal planes in selected cases.

RESULTS

Thirty of 41 (78%) foetal spines were found to be normal at autopsy and on post-mortem MRI. Eleven of 41 (22%) foetal spines were abnormal: eight foetuses had myelomeningocoeles and Chiari 2 deformities, one foetus had limited dorsal myeloschisis, one foetus had caudal regression syndrome, and one had diastematomyelia. The post-mortem MRI findings concurred with the autopsy findings in 10/11 of the abnormal cases, the disagreement being the case of diastematomyelia that was shown on post-mortem MRI but was not diagnosed at autopsy.

CONCLUSIONS

In this series, post-mortem MRI findings agreed with the autopsy findings in 40/41(98%) cases and in one case the post-mortem MRI demonstrated an abnormality not demonstrated at autopsy.

Simultaneous parallel inclined readout image technique

Sensitivity-encoded phase undersampling has been combined with simultaneous slice excitation to produce a parallel MRI method with a high volumetric acquisition acceleration factor without the need for auxiliary stepped field coils. Dual-slice excitation was produced by modulating both spin and gradient echo sequences at +/-6 kHz. Frequency aliasing of simultaneously excited slices was prevented by using an additional gradient applied along the slice axis during data acquisition. Data were acquired using a four-channel receiver array and x4 sensitivity encoding on a 1.5 T MR system. The simultaneous parallel inclined readout image technique has been successfully demonstrated in both phantoms and volunteers. A multiplicative image acquisition acceleration factor of up to x8 was achieved. Image SNR and resolution was dependent on the ratio of the readout gradient to the additional slice gradient. A ratio of approximately 2:1 produced acceptable image quality. Use of RF pulses with additional excitation bands should enable the technique to be extended to volumetric acquisition acceleration factors in the range of x16-24 without the SNR limitations of pure partially parallel phase reduction methods.

Normal fetal lumbar spine on postmortem MR imaging

BACKGROUND AND PURPOSE

There is an increasing interest in use of postmortem MR imaging as an adjunct or alternative to autopsy. Before evaluating spinal pathology on postmortem MR imaging, it is important to have knowledge of the normal appearance of the fetal spine at different gestational ages. The aim of this study is to describe the MR imaging appearances of normal development of the fetal spine at different gestational ages.

METHODS

Postmortem MR imaging was performed on 30 fetuses ranging from 14 to 41 gestational weeks. There was no structural abnormality of the spine in these fetuses on MR imaging or at autopsy. Fast spin-echo T2-weighted MR imaging of the lumbar spine was performed in the coronal plane in all cases and supplemented by sagittal and/or axial imaging. The following parameters were measured: height of the L1/2 disk and L2 vertebral body and area of ossification center in L2 vertebral body as well as area of vertebral body. The signal intensity of the disk space and the vertebral level of conus termination were also assessed.

RESULTS

The height and area of the vertebral body increased linearly with gestational age (P <.01). The increase in disk space was proportionally greater than the increase in vertebral body height as gestational age increased (P <.01). The disk space appeared as a linear low-signal-intensity area in fetuses < or = 21 weeks gestation but increasingly developed high signal intensity in the disk after 21 weeks. The size of the ossification center increased with gestational age (P <.01), and the ratio of ossification center to the overall size of the vertebral body also increased with gestational age (P <.01). In fetuses less than 35 weeks of age, the conus lay between L2 and L5 level, whereas in fetuses more than 35 weeks of age, the conus lay between L1/2 and L2/3 level.

CONCLUSION

Understanding the normal growth and signal-intensity characteristics of the fetal spine on postmortem MR imaging is essential before studying abnormal fetal spine.

Post-mortem fetal MRI: what do we learn from it?

Post-mortem magnetic resonance (MR) imaging is of increasing interest not only as an alternative to autopsy but as a research tool to aid the interpretation and diagnosis of in utero MR images. The information from the post-mortem MR has allowed the development of imaging sequences applicable to in utero imaging and neonatal imaging. It has established brain development during gestation and has provided data on this to which in utero MR can be compared. The detail available from the post-mortem images is such that brain development can be studied in a non-invasive manner, a permanent record on the normal and abnormal areas is available and a greater understanding of developmental abnormalities is possible.

The OEIS complex: two case reports that illustrate the spectrum of abnormalities and a review of the literature

We present two cases of OEIS (omphalocele, exstrophy, imperforate anus, spinal defects) complex -MIM 258040 and a review of the literature. Case 1 was a 14-year-old girl who presented at 30 weeks' gestation. An ultrasound examination showed an omphalocele and spina bifida; the bladder was not visualised. She went into spontaneous labour two weeks later and the baby died shortly after birth. A full post-mortem examination was refused, but the mother did agree to an external examination, skin biopsy for fibroblast culture, X rays and MR imaging. The MR imaging showed a pelvic kidney, a large omphalocele containing the other kidney, liver, bowel and a fluid filled structure thought to represent an exstrophy of the bladder (EB). Case 2 was a 30-year-old woman who had an ultrasound examination at 20 weeks' gestation; this showed an omphalocele, but the bladder was not visualised. The pregnancy was subsequently terminated and a post-mortem examination showed a low set umbilical cord associated with a small omphalocele; there was an imperforate anus; a blind ending rectum terminated in the omphalocele. We conclude that these two cases illustrate the variability of the OEIS complex.

Postmortem MR imaging of the fetus: an adjunct or a replacement for conventional autopsy?

Fetal and perinatal autopsy provides essential diagnostic information not only for parents but also for medical audit and clinical trials. The autopsy rate is decreasing throughout the world for numerous reasons. Medical imaging has always been part of the autopsy process, but in the last decade there has been increased interest in imaging as additional to or a replacement for autopsy. This is especially so with the wider availability of magnetic resonance (MR) scanners that are able to provide detailed anatomy of all body structures as well as having the potential to provide information about histopathological patterns of injury. Postmortem MR imaging (MRI) provides similar information to autopsy for gross pathology of most organ systems. It often provides more information in cases of central nervous system abnormalities, but is less accurate for cardiac abnormalities. Targeted, image-guided biopsy may allow histological diagnosis following postmortem MRI.

Post-mortem MRI as an adjunct to fetal or neonatal autopsy

CONTEXT

Understanding what was wrong with a dead fetus or why a newborn child died can help the parents to grieve, while any findings can be used to inform the parents if there is a risk to future pregnancies and the level of risk. This information is mainly obtained from autopsies, but the number of parents agreeing to autopsy has dropped, which has prompted the search for adjuncts to autopsy.

STARTING POINT

The UK's Chief Medical Officer outlined the rationale for exploring alternatives to autopsy in 2000 and 2001. After wide consultation, MRI was deemed to offer the most realistic chance of making a contribution. Results so far are promising, but of insufficient depth and quality to make firm recommendations about providing a service in the future. In 2004, the UK Department of Health therefore tendered for this research to be done in fetal and neonatal (and adult) cases, and this work is due to start in 2005. WHERE NEXT? High-quality anatomical information about the brain and spine of fetuses and neonates can be easily obtained with standard MRI scanners. Most developmental and acquired abnormalities can be seen on post-mortem MRI. More work needs to be done on organs not in the central nervous system, and heart malformations, in particular, might present diagnostic problems. A possible outcome could be whole-body MRI plus targeted biopsies of abnormalities taken under image guidance as an adjunct to formal autopsy.

Corroboration of in utero MRI using post-mortem MRI and autopsy in foetuses with CNS abnormalities

AIMS

To corroborate the findings of in utero magnetic resonance imaging (MRI) with autopsy and post-mortem MRI in cases of known or suspected central nervous system (CNS) abnormalities on ultrasound and to compare the diagnostic accuracy of ante-natal ultrasound and in utero MRI.

METHODS

Twelve pregnant women, whose foetuses had suspected central nervous system abnormalities underwent in utero MRI. The foetuses were imaged using MRi before autopsy. The data were used to evaluate the diagnostic accuracy of in utero MRI when compared with a reference standard of autopsy and post-mortem MRI in 10 cases and post-mortem MRI alone in two cases.

RESULTS

The diagnostic accuracy of antenatal ultrasound and in utero MRI in correctly characterizing brain and spine abnormalities were 42 and 100%, respectively.

CONCLUSION

In utero MRI provides a useful adjuvant to antenatal ultrasound when assessing CNS abnormalities by providing more accurate anatomical information. Post-mortem MRI assists the diagnosis of macroscopic structural abnormalities.

Comparison of ultrasound and magnetic resonance imaging in 100 singleton pregnancies with suspected brain abnormalities

OBJECTIVE

To compare the diagnostic accuracy of the current reference standard-ultrasound with in utero magnetic resonance imaging, in a selected group of patients.

DESIGN

Prospective study.

SETTING

Five fetal maternal tertiary referral centres and an academic radiology unit.

SAMPLE

One hundred cases of fetuses with central nervous system abnormalities where there has been diagnostic difficulties on ultrasound. In 48 cases the women were less than 24 weeks of gestation and in 52 cases later in pregnancy.

METHODS

All women were imaged on a 1.5 T clinical system using a single shot fast spin echo technique. The results of antenatal ultrasound and in utero magnetic resonance were compared.

MAIN OUTCOME MEASURES

The definitive diagnosis was made either at autopsy or by postmortem magnetic resonance imaging, in cases that went to termination of pregnancy, or a combination of postnatal imaging and clinical follow up in the others.

RESULTS

In 52 of cases, ultrasound and magnetic resonance gave identical results and in a further 12, magnetic resonance provided extra information that was judged not to have had direct effects on management. In 35 of cases, magnetic resonance either changed the diagnosis (29) or gave extra information that could have altered management (6). In 11 of the 30 cases where magnetic resonance changed the diagnosis, the brain was described as normal on magnetic resonance.

CONCLUSIONS

In utero magnetic resonance imaging is a powerful tool in investigating fetal brain abnormalities. Our results suggest that in selected cases of brain abnormalities, detected by ultrasound, antenatal magnetic resonance may provide additional, clinically useful information that may alter management.

Frequency and natural history of subdural haemorrhages in babies and relation to obstetric factors

BACKGROUND

Subdural haematomas are thought to be uncommon in babies born at term. This view is mainly based on findings in symptomatic neonates and babies in whom subdural haemorrhages are detected fortuitously. We aimed to establish the frequency of subdural haemorrhages in asymptomatic term neonates; to study the natural history of such subdural haematomas; and to ascertain which obstetric factors, if any, are associated with presence of subdural haematoma.

METHODS

We did a prospective study in babies who were born in the Jessop wing of the Central Sheffield University Hospitals between March, 2001, and November, 2002. We scanned neonates with a 0.2 T magnetic resonance machine.

FINDINGS

111 babies underwent MRI in this study. 49 were born by normal vertex delivery without instrumentation, 25 by caesarean section, four with forceps, 13 ventouse, 18 failed ventouse leading to forceps, one failed ventouse leading to caesarean section, and one failed forceps leading to caesarean section. Nine babies had subdural haemorrhages: three were normal vaginal deliveries (risk 6.1%), five were delivered by forceps after an attempted ventouse delivery (27.8%), and one had a traumatic ventouse delivery (7.7%). All babies with subdural haemorrhage were assessed clinically but no intervention was needed. All were rescanned at 4 weeks and haematomas had completely resolved.

INTERPRETATION

Presence of unilateral and bilateral subdural haemorrhage is not necessarily indicative of excessive birth trauma.

Ultrafast magnetic resonance imaging of the neonate in a magnetic resonance-compatible incubator with a built-in coil

BACKGROUND

Magnetic resonance (MR) imaging of the neonate is important clinically, because this group of patients often has complex and multiple problems due to prematurity and developmental abnormalities. MR imaging usually involves moving neonates away from their controlled environment to the scanner.

OBJECTIVE

In this study we present the results of our initial experience with an MR-compatible incubator used on a 1.5-T system.

METHODS

Seven neonates were imaged at 1.5 T without sedation or anesthesia. Images were obtained by using single-shot fast spin echo, 3-dimensional Fourier transfer gradient echo, and diffusion-weighted sequences. In 4 cases, time-of-flight angiography was performed.

RESULTS

All 7 neonates were stable throughout the scan time (10-21 minutes). Experienced observers graded the images for quality, and all were graded excellent or good. In no case was the image quality poor.

CONCLUSION

Neonates can be imaged safely by using an MR-compatible incubator and fast image sequences. This method should allow neonates to be imaged by MR in sites at which a dedicated neonatal MR scanner is not available.

MR imaging of the fetal brain and spine: a maturing technology

INTRODUCTION

We describe the background and refinements to a 3-year research study designed to evaluate the role of magnetic resonance (MR) imaging in detecting and defining abnormalities of the fetal central nervous system in utero.

METHODS

We describe our experience of using ultra-fast MR imaging methods (specifically single-shot fast spin echo) in 250 fetuses at various gestational ages. All fetuses had known or suspected brain or spine abnormalities based on antenatal ultrasound imaging. We describe the ethical issues raised by this type of work and the differences in diagnostic accuracy between ultrasound and MR imaging.

RESULTS

We show that MR imaging can be performed in a clinical environment with a high degree of success: only 2 women out of 250 could not be examined (1 was claustrophobic and the other was too large for our scanner). In the 100 cases of singleton pregnancies, where detailed follow-up is available, there is a > 40% improvement in diagnostic accuracy when MR imaging is included in the fetal assessment compared to ultrasound alone.

CONCLUSION

We conclude that in utero MR imaging is a powerful tool in the assessment of fetal brain and spine abnormalities, and suggest that further work be undertaken to provide a widely available clinical service.

B1AC-MAMBA: B1 array combined with multiple-acquisition micro B0 array parallel magnetic resonance imaging

The combination of an in-plane B(1) sensitivity encoding (SENSE) technique with a simultaneous multiple-slice B(0) field step technique (multiple-acquisition micro B(0) array (MAMBA)) has produced high scan time reduction factors (R < or = 8). In this study, two slices were acquired simultaneously in combination with x2 and x4 SENSE in-plane encoding using a MAMBA stepped B(0) field coil inside a four-channel phased-array coil system. Experiments were performed on a 1.5 T Infinion system (Philips Medical Systems, Cleveland, OH). The signal-to-noise ratio (SNR) was reduced with higher R factors, as was expected from the reduced number of acquisitions used to create the unaliased images. The combination of SENSE and MAMBA offers great promise for reducing scan times through parallel acquisition while at the same time reducing the number of RF channels required by a factor equal to the number of field steps employed. The B(1) array combined with MAMBA (B(1)AC-MAMBA) technique is applicable when the length of an object is much greater than its diameter, as in scanning limbs or in whole-body screening for disease.

Low field strength magnetic resonance imaging of the neonatal brain

BACKGROUND

Magnetic resonance (MR) imaging of the neonate has been restricted by the need to transport the sick baby to the large magnetic resonance scanners and often the need for sedation or anaesthesia in order to obtain good quality images. Ultrasound is the reference standard for neonatal imaging.

OBJECTIVE

To establish a dedicated neonatal MR system and compare the clinical usefulness of MR imaging with ultrasound imaging.

DESIGN

Prospective double blind trial.

SETTING

Neonatal intensive care unit, Sheffield.

MAIN OUTCOME MEASURES

Imaging reports.

PATIENTS

134 premature and term babies.

RESULTS

In 56% of infants with pathology suspected on clinical grounds, MR provided additional useful clinical information over and above that obtained with ultrasound.

CONCLUSION

Infants can be safely imaged by dedicated low field magnetic resonance on the neonatal intensive care unit without the need for sedation at a cost equivalent to ultrasound.

Interleaved pulsed MAMBA: a new parallel slice imaging method

A method of acquiring slices in parallel is described which uses interleaved sets of pulsed B(0) field coils to generate discrete regions of uniform field within the main magnetic field known as interleaved MAMBA (multiple acquisition micro B(0) array). Simulations of a number of coil designs were performed using the Biot-Savart law. A six-step coil was built and interfaced to a 0.17 T Niche MRI system and the field steps measured using an imaging technique. Measured field steps were in good agreement with the values predicted by simulation. The coil design was then scaled up by a factor of three, interfaced to a 1.5 T whole-body MRI system, and scans of the hands and arms of volunteers were acquired from up to four field steps using standard spin and gradient echo sequences. Images were also acquired simultaneously from two field steps with no frequency encode aliasing and one excitation. The one-dimensional interleaved pulsed MAMBA step field technique shows great promise for enabling many slices to be acquired simultaneously along the axis of the coil for rapid volumetric studies without the need for multiple shot Hadamard encoding. Extension of interleaved coil design to two or three dimensions is feasible, which could provide full spatial coverage combined with ultra-rapid data acquisition.

Fractures of the lateral process of the talus--the value of lateral tomography

We present three cases of fractures of the lateral process of the talus, where routine anteroposterior and lateral radiographs showed an abnormality but were insufficient to assess the degree of bony injury, which is important for clinical management. Lateral tomography provided good diagnostic and anatomical detail. The diagnosis and treatment of this unusual and often missed fracture is discussed.

Allograft rejection in athymic nude rats by transferred T cell subsets. II. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to an isolated MHC class I disparity

Athymic PVG-rnu/rnu (RT1c) rats were grafted with skin bearing isolated MHC disparities 7-14 days in advance of cell transfer. The ability of naive CD4+ or CD8+ thoracic duct lymphocytes to induce rejection was assessed by adoptive transfer of one or both T cell subsets into nude recipients bearing congenic PVG.r1 (MHC class I-only disparity, Aa) or PVG.r19 (class I and II-only disparity, Aa B/Da) skin grafts. Recipients of purified CD4+ TDL always rejected r19 allografts, whereas CD8+ TDL were ineffective against this class I + II difference. Neither the injection of CD4+ TDL nor CD8+ TDL alone resulted in destruction of r1 skin grafts. However, rejection of r1 tissue was observed in 63% of cases (19/30) when both CD4+ and CD8+ TDL were present in the nude recipients. Rejection of r1 skin was also induced in some recipients when CD8+ TDL were transferred 8 weeks in advance of CD4+ TDL. In contrast, sequential transfer in the reverse order apparently induced tolerance in the CD4+ population--i.e., surviving r1 skin grafts on 8 week CD4+ T cell-reconstituted nude recipients were not rejected following the subsequent transfer of CD8+ TDL. We conclude that CD4+ T cells were required for rejection of both class I and class II differences. In the presence of a class II difference, CD4+ T cells function autonomously to initiate both the inducer and effector stages of rejection. When the disparity is confined to class I, CD8+ T cells are required (probably at the effector stage) but are dependent on CD4+ T cells for help. There was no evidence of CD4+ effector T cells that could recognize class I directly within the graft.

Allograft rejection in athymic nude rats by transferred T-cell subsets. I. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to complete allogeneic incompatibilities

PVG.rnu/rnu nude rats were pre-grafted with two allogeneic skin grafts, AO(RTlu) and BN(RTln), 6-14 days in advance of cell transfer. Cellular requirements for rejection were established by transferring graded numbers of B cell-depleted (Ig-) thoracic duct lymphocytes (TDL) or purified W3/25+ (CD4+) or OX8+ (CD8+) TDL subsets. Allografts were rejected by 10(5) to 5 x 10(6) Ig- TDL in a dose-dependent fashion. A similar dose-response relationship was found by transferring 5 x 10(5) to 5 x 10(6) Ig- OX8- TDL (purified by depletion of B cells and OX8+ cells). Larger numbers of Ig- OX8- TDL (10-30 x 10(6)) did not significantly accelerate rejection. W3/25+ TDL alone (10(5)), highly purified by fluorescence-activated cell sorting (FACS), were sufficient to induce allograft rejection in this athymic nude rat model. In contrast, 10 times more FACS purified OX8+ TDL (10(6)) were unable to initiate skin graft rejection despite the complete class I and class II MHC incompatibilities. Furthermore, the addition of 10(6) OX8+ cells did not accelerate or retard the rejection induced by 10(5) W3/25+ cells alone. Pre-grafted nude recipients, irradiated (500 R) 2 hr before W3/25+ TDL injection, in order to eliminate putative nude T cells, rejected allografts on the same day as unirradiated controls. We conclude that when confronted with complete MHC disparities, CD4+ T cells are necessary and sufficient to induce skin allograft rejection whereas CD8+ T cells do not appear to contribute.