Post-mortem whole-body magnetic resonance imaging of human fetuses: a comparison of 3-T vs. 1.5-T MR imaging with classical autopsy

3 Tesla Fetal MR Imaging Quality and Safety Considerations

Medical imaging, particularly fetal MR imaging, has undergone a transformative shift with the introduction of 3 Tesla (3T) clinical MR imaging systems. The utilization of higher static magnetic fields in these systems has resulted in remarkable advancements, including superior soft tissue contrast, improved spatial and temporal resolution, and reduced image acquisition time. Despite these notable benefits, safety concerns have emerged, stemming from the elevated static magnetic field strength, amplified acoustic noise, and increased radiofrequency power deposition. This article provides an overview of fetal MR imaging at 3T, its benefits and drawbacks, and the potential safety issues.

Postmortem MR in termination of pregnancy for central nervous system (CNS) anomalies

OBJECTIVES

To evaluate the concordance of conventional autopsy (CA) and postmortem magnetic resonance (MR) after termination of pregnancy (TOP) in fetuses with prenatally detected central nervous system (CNS) anomalies. Second, to determine the most informative postmortem investigation in parental counseling.

METHODS

All TOPs between 2006 and 2016 with prenatally detected CNS involvement and having a postmortem MR and CA as postmortem examinations were retrospectively analyzed and concordance levels were established.

RESULTS

Of 764 TOPs, 255 cases had a CNS anomaly detected prenatally (33.4%). Fetal genetic anomalies (n = 40) and cases without both postmortem MR and CA were excluded, leaving 68 cases for analysis.Disagreement between postmortem MR and CA was observed in 22 cases (32.4%). In eight cases (11.8%), more information was obtained by CA compared with MR. However, only two cases with major additional findings were found when compared with prenatal diagnosis. In 14 cases (20.6%), MR was superior to CA either because of additional cerebral anomalies undetected by CA (n = 5) and/or because of severe autolysis hindering pathology of the CNS (n = 9).

CONCLUSIONS

Our data point out that an adequate postmortem evaluation, valuable in parental counseling, can be provided by a postmortem MR in 97% of the cases.Key PointsAn adequate postmortem evaluation, valuable in parental counseling, can be provided by a postmortem (PM) magnetic resonance (MR) in the majority of cases.PM MR is an excellent postmortem imaging tool for the brain.In cases with brain autolysis, PM MR is often the only informative PM investigation tool.PM MR is an essential adjunct to CA in the PM evaluation of pregnancies terminated for a central nervous system (CNS) anomaly.

Post-mortem radiology in fetal and neonatal death: the diagnostic value of post-mortem MRI versus autopsy regarding non-cardiac thoracic and abdominal abnormalities

AIM

To compare the diagnostic value and accuracy of post-mortem magnetic resonance imaging (PMMRI) and autopsy for non-cardiac thoracic and abdominal abnormalities in fetal death.

MATERIALS AND METHODS

This single-institution retrospective study included all consecutive cases of fetal and perinatal death between January 2015 and December 2021 for which PMMRI followed by autopsy was conducted. These cases comprised fetuses at >18 weeks of gestation and preterm and term neonates who lived for <24 h. All PMMRI and autopsy reports were re-assessed and scored for seven non-cardiac thoracic and 52 abdominal abnormalities, and concordance between autopsy and PMMRI findings was determined as the primary outcome.

RESULTS

Eighty cases were included in this study. Fetal loss was caused by termination of pregnancy in 80% of cases. Further, the mean gestational age was 166 days (23 weeks and 5 days, range 126-283 days). The concordance between PMMRI and autopsy for non-cardiac thoracic and abdominal abnormalities was 83.1% (95% confidence interval [CI] 71.3-83.3) and 76.3% (95% CI 65.8-84.2%), respectively, with a substantial and moderate strength of agreement (Cohen's kappa = 0.63 and 0.51 respectively).

CONCLUSION

PMMRI exhibited good overall diagnostic value for non-cardiac thoracic and abdominal abnormalities, specifically large structural abnormalities. PMMRI may offer parents and physicians a valuable addition to autopsy for the detection of non-cardiac thoracic and abdominal abnormalities, or even an alternative option when parents do not consent to autopsy.

Are non-invasive or minimally invasive autopsy techniques for detecting cause of death in prenates, neonates and infants accurate? A systematic review of diagnostic test accuracy

OBJECTIVES

To assess the diagnostic accuracy of non-invasive or minimally invasive autopsy techniques in deaths under 1 year of age.

DESIGN

This is a systematic review of diagnostic test accuracy. The protocol is registered on PROSPERO.

PARTICIPANTS

Deaths from conception to one adjusted year of age.

SEARCH METHODS

MEDLINE (Ovid), EMBASE (Ovid), CINAHL (EBSCO), the Cochrane Library, Scopus and grey literature sources were searched from inception to November 2021.

DIAGNOSTIC TESTS

Non-invasive or minimally invasive diagnostic tests as an alternative to traditional autopsy.

DATA COLLECTION AND ANALYSIS

Studies were included if participants were under one adjusted year of age, with index tests conducted prior to the reference standard.Data were extracted from eligible studies using piloted forms. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies-2. A narrative synthesis was conducted following the Synthesis without Meta-Analysis guidelines. Vote counting was used to assess the direction of effect.

MAIN OUTCOME MEASURES

Direction of effect was expressed as percentage of patients per study.

FINDINGS

We included 54 direct evidence studies (68 articles/trials), encompassing 3268 cases and eight index tests. The direction of effect was positive for postmortem ultrasound and antenatal echography, although with varying levels of success. Conversely, the direction of effect was against virtual autopsy. For the remaining tests, the direction of effect was inconclusive.A further 134 indirect evidence studies (135 articles/trials) were included, encompassing 6242 perinatal cases. The addition of these results had minimal impact on the direct findings yet did reveal other techniques, which may be favourable alternatives to autopsy.Seven trial registrations were included but yielded no results.

CONCLUSIONS

Current evidence is insufficient to make firm conclusions about the generalised use of non-invasive or minimally invasive autopsy techniques in relation to all perinatal population groups.PROSPERO registration numberCRD42021223254.

Fetal brain maceration score on postmortem magnetic resonance imaging vs. conventional autopsy

BACKGROUND

Postmortem fetal magnetic resonance imaging (MRI) has been on the rise since it was proven to be a good alternative to conventional autopsy. Since the fetal brain is sensitive to postmortem changes, extensive tissue fixation is required for macroscopic and microscopic assessment. Estimation of brain maceration on MRI, before autopsy, may optimize histopathological resources.

OBJECTIVE

The aim of the study is to develop an MRI-based postmortem fetal brain maceration score and to correlate it with brain maceration as assessed by autopsy.

MATERIALS AND METHODS

This retrospective single-center study includes 79 fetuses who had postmortem MRI followed by autopsy. Maceration was scored on MRI on a numerical severity scale, based on our brain-specific maceration score and the whole-body score of Montaldo. Additionally, maceration was scored on histopathology with a semiquantitative severity scale. Both the brain-specific and the whole-body maceration imaging scores were correlated with the histopathological maceration score. Intra- and interobserver agreements were tested for the brain-specific maceration score.

RESULTS

The proposed brain-specific maceration score correlates well with fetal brain maceration assessed by autopsy (τ = 0.690), compared to a poorer correlation of the whole-body method (τ = 0.452). The intra- and interobserver agreement was excellent (correlation coefficients of 0.943 and 0.864, respectively).

CONCLUSION

We present a brain-specific postmortem MRI maceration score that correlates well with the degree of fetal brain maceration seen at histopathological exam. The score is reliably reproduced by different observers with different experience.

Comparison of postmortem whole-body contrast-enhanced microfocus computed tomography and high-field magnetic resonance imaging of human fetuses

OBJECTIVE

Although fetal autopsy is generally recommended to confirm or refute the antemortem diagnosis, parental acceptance of the procedure has fallen over time, mainly due to its invasiveness. Contrast-enhanced microfocus CT (micro-CT) and high-field magnetic resonance imaging (HF-MRI, ≥ 3 Tesla) have both been suggested as non-invasive alternatives to conventional fetal autopsy for fetuses < 20 weeks of gestation. The aim of this study was to compare these two modalities in postmortem whole-body fetal imaging.

METHODS

In this study, the imaging process and quality of micro-CT and HF-MRI were compared using both qualitative and quantitative assessments. For the qualitative evaluation, fetal anatomy experts scored 56 HF-MRI and 56 micro-CT images of four human fetuses aged 13-18 gestational weeks on two components: overall image quality and the ability to recognize and assess 21 anatomical structures. For the quantitative evaluation, participants segmented manually three organs with increasing complexity to assess interobserver variability. In addition, the signal-to-noise and contrast-to-noise ratios of five major organs were determined.

RESULTS

Both imaging techniques were able to reach submillimeter voxel size. The highest resolution of micro-CT was 22 µm (isotropic), while the highest resolution of HF-MRI was 137 µm (isotropic). The qualitative image assessment form was sent to 45 fetal anatomy experts, of whom 36 (80%) responded. It was observed that micro-CT scored higher on all components of the qualitative assessment compared with HF-MRI. In addition, the quantitative assessment showed that micro-CT had lower interobserver variability and higher signal-to-noise and contrast-to-noise ratios.

CONCLUSIONS

Our findings show that micro-CT outperforms HF-MRI in postmortem whole-body fetal imaging in terms of both quantitative and qualitative outcomes. Combined, these findings suggest that the ability to extract diagnostic information is greater when assessing micro-CT compared with HF-MRI images. We, therefore, believe that micro-CT is the preferred imaging modality as an alternative to conventional fetal autopsy for early gestation and is an indispensable tool in postmortem imaging services. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Post-mortem perinatal imaging: what is the evidence?

Post-mortem imaging for the investigation of perinatal deaths is an acceptable tool amongst parents and religious groups, enabling a less invasive autopsy examination. Nevertheless, availability is scarce nationwide, and there is some debate amongst radiologists regarding the best practice and optimal protocols for performing such studies. Much of the published literature to date focusses on single centre experiences or interesting case reports. Diagnostic accuracy studies are available for a variety of individual imaging modalities (e.g. post-mortem CT, MRI, ultrasound and micro-CT), however, assimilating this information is important when attempting to start a local service.In this article, we present a comprehensive review summarising the latest research, recently published international guidelines, and describe which imaging modalities are best suited for specific indications. When the antenatal clinical findings are not supported by the post-mortem imaging, we also suggest how and when an invasive autopsy may be considered. In general, a collaborative working relationship within a multidisciplinary team (consisting of radiologists, radiographers, the local pathology department, mortuary staff, foetal medicine specialists, obstetricians and bereavement midwives) is vital for a successful service.

Diagnostic value of virtual autopsy using pm-MRI at 3T on malformed second trimester fetuses vs classic autopsy

Objective

To determine the diagnostic value of virtual autopsy using post mortem-MRI (pm-MRI) at 3Tesla (T) compared to classic autopsy for the confirmation of fetal structural anomalies and secondly to establish which cases of termination of pregnancy would benefit mostly from a virtual autopsy.

Methods

In each of 32 fetuses included in the study, 32 anatomical structures were assessed, after termination of pregnancy in the second trimester. All cases were evaluated by prenatal ultrasonography, virtual autopsy and classic autopsy, and then divided into four groups: Cerebral Group, Cardiac Group, Renal Group and Other Group (miscellaneous group). The concordance of virtual autopsy with classic autopsy was calculated overall and for each group and each structural item. Also, the concordance between the two methods was assessed using a diagnostic error score (DgE_score), calculated as the absolute value of the difference between the number of malformations detected by classic autopsy per case (CA score) and the number of malformations detected at virtual autopsy per case (VA score).

Results

Overall virtual autopsy demonstrated a diagnostic sensitivity (Se) compared to classic autopsy of 67.33% [95% CI 57.28–76.33], with a specificity (Sp) of 98.37% [95% CI 97.33–99.09], a positive predictive value (PPV) of 81.93% [95% CI 71.95–89.52], a negative predictive value (NPV) of 96.49% [95% CI 95.11–97.57] achieving a diagnostic accuracy of 95.31% [95% CI 93.83–96.52]. Overall, no statistic significant correlation was demonstrated between DgE_score and the gestational age of the fetuses or between DgE_score and the weight of the fetuses, but a significant correlation was revealed between the virtual autopsy and classic autopsy score. The diagnostic utility of virtual autopsy using pm-MRI at 3 T as compared to classic autopsy for each category of termination of pregnancy revealed in the Cerebral Group a Se of 80.00% [95% CI 28.36–99.49], with a 96.30% [95% CI 81.03–99.91], a PPV of 80.00% [95% CI 35.75–96.64] a NPV of 96.30% [95% CI 81.81–99.34], with a diagnostic accuracy of 93.75% [95% CI 79.19% to 99.23] and a Cohen’s Kappa coefficient of 0.76 [95% CI 0.4494–1.0765]; in the Renal Group a Se and Sp of 100%, but in the Cardiac Group the Se was only 60.00% [95% CI 26.24–87.84], Sp 75% [95% CI 34.91–96.81], the PPV 75.00% [95% CI 44.92–91.69], NPV 60% [95% CI 38.87–77.96], with a diagnostic accuracy of 66.67% [95% CI 40.99–86.66] and a Cohen’s Kappa coefficient of 0.32 [95% CI -0.07–0.76].

Conclusions

The results support virtual autopsy using pm-MRI at 3T as a reliable alternative to classic autopsy for the non-forensic analysis of second trimester fetuses. Analyzing the diagnostic utility of virtual autopsy using pm-MRI at 3 T for the confirmation of prenatal ultrasound findings in second trimester fetuses as compared to classic autopsy, the best results were obtained in the Cerebral and Renal Group. Reserved results were found in the Cardiac Group. Therefore, for the pregnancies with termination of pregnancy for cerebral or renal abnormalities, virtual autopsy by pm-MRI at 3T can be taken into consideration as a first-line investigation to confirm the prenatal findings.

Micro-CT yields high image quality in human fetal post-mortem imaging despite maceration

BACKGROUND

Current clinical post-mortem imaging techniques do not provide sufficiently high-resolution imaging for smaller fetuses after pregnancy loss. Post-mortem micro-CT is a non-invasive technique that can deliver high diagnostic accuracy for these smaller fetuses. The purpose of the study is to identify the main predictors of image quality for human fetal post-mortem micro-CT imaging.

METHODS

Human fetuses were imaged using micro-CT following potassium tri-iodide tissue preparation, and axial head and chest views were assessed for image quality on a Likert scale by two blinded radiologists. Simple and multivariable linear regression models were performed with demographic details, iodination, tissue maceration score and imaging parameters as predictor variables.

RESULTS

258 fetuses were assessed, with median weight 41.7 g (2.6-350 g) and mean gestational age 16 weeks (11-24 weeks). A high image quality score (> 6.5) was achieved in 95% of micro-CT studies, higher for the head (median = 9) than chest (median = 8.5) imaging. The strongest negative predictors of image quality were increasing maceration and body weight (p < 0.001), with number of projections being the best positive imaging predictor.

CONCLUSIONS

High micro-CT image quality score is achievable following early pregnancy loss despite fetal maceration, particularly in smaller fetuses where conventional autopsy may be particularly challenging. These findings will help establish clinical micro-CT imaging services, addressing the need for less invasive fetal autopsy methods.

Diagnostic quality of 3Tesla postmortem magnetic resonance imaging in fetuses with and without congenital heart disease

BACKGROUND

Postmortem confirmation of prenatally diagnosed congenital heart disease after termination of pregnancy and evaluation of potential cardiac defects after spontaneous fetal or neonatal death are essential. Conventional autopsy rates are decreasing, and 1.5Tesla magnetic resonance imaging has demonstrated limited diagnostic accuracy for postmortem cardiovascular assessment.

OBJECTIVE

This study aimed to evaluate the feasibility and image quality of cardiac 3Tesla postmortem magnetic resonance imaging and to assess its diagnostic accuracy in detecting fetal heart defects compared with conventional autopsy. Secondarily, the study aimed to explore whether clinical factors affect the quality of 3Tesla postmortem magnetic resonance imaging.

STUDY DESIGN

A total of 222 consecutive fetuses between 12 and 41 weeks' gestation, who underwent 3Tesla postmortem magnetic resonance imaging and conventional autopsy after spontaneous death or termination of pregnancy for fetal malformations, were included. First, 3Tesla postmortem magnetic resonance imaging of each fetus was rated as diagnostic or nondiagnostic for fetal cardiac assessment by 2 independent raters. The image quality of individual cardiac structures was then further evaluated by visual grading analysis. Finally, the presence or absence of a congenital heart defect was assessed by 2 radiologists and compared with autopsy results.

RESULTS

Overall, 87.8% of 3Tesla postmortem magnetic resonance imaging examinations were rated as diagnostic for the fetal heart. Diagnostic imaging rates of individual cardiac structures at 3Tesla postmortem magnetic resonance imaging ranged from 85.1% (atrioventricular valves) to 94.6% (pericardium), with an interrater agreement of 0.82 (0.78-0.86). Diagnostic imaging of the fetal aortic arch and the systemic veins at 3Tesla postmortem magnetic resonance imaging was possible from 12+5 weeks' gestation onward in 90.1% and 92.3% of cases, respectively. A total of 55 fetuses (24.8%) had at least 1 cardiac anomaly according to autopsy, 164 (73.9%) had a normal heart, and in 3 fetuses (1.4%), autopsy was nondiagnostic for the heart. Considering all examinations rated as diagnostic, 3Tesla postmortem magnetic resonance imaging provided high diagnostic accuracy for the detection of fetal congenital heart defects with a sensitivity of 87.8%, a specificity of 97.9%, and concordance with autopsy of 95.3%. 3Tesla postmortem magnetic resonance imaging was less accurate in young fetuses (<20 weeks compared with ≥20 weeks; P<.001), in fetuses with low birthweight (≤100 g compared with >100 g; P<.001), in cases after spontaneous fetal death (compared with other modes of death; P=.012), in cases with increasing latency between death and 3Tesla postmortem magnetic resonance imaging (P<.001), and in cases in which there was a high degree of maceration (maceration score of 3 compared with a score from 0 to 2; P=.004).

CONCLUSION

Diagnostic 3Tesla postmortem magnetic resonance imaging assessment of the fetal heart is feasible in most fetuses from 12 weeks' gestation onward. In diagnostic images, sensitivity and, particularly, specificity in the detection of congenital heart disease are high compared with conventional autopsy. Owing to its high diagnostic accuracy, we suggest that 3Tesla postmortem magnetic resonance imaging may serve as a suitable imaging modality with which to direct a targeted conventional autopsy when pathology resources are limited or to provide a virtual autopsy when full autopsy is declined by the parents.

A pragmatic evidence-based approach to post-mortem perinatal imaging

Post-mortem imaging has a high acceptance rate amongst parents and healthcare professionals as a non-invasive method for investigating perinatal deaths. Previously viewed as a 'niche' subspecialty, it is becoming increasingly requested, with general radiologists now more frequently asked to oversee and advise on appropriate imaging protocols. Much of the current literature to date has focussed on diagnostic accuracy and clinical experiences of individual centres and their imaging techniques (e.g. post-mortem CT, MRI, ultrasound and micro-CT), and pragmatic, evidence-based guidance for how to approach such referrals in real-world practice is lacking. In this review, we summarise the latest research and provide an approach and flowchart to aid decision-making for perinatal post-mortem imaging. We highlight key aspects of the maternal and antenatal history that radiologists should consider when protocolling studies (e.g. antenatal imaging findings and history), and emphasise important factors that could impact the diagnostic quality of post-mortem imaging examinations (e.g. post-mortem weight and time interval). Considerations regarding when ancillary post-mortem image-guided biopsy tests are beneficial are also addressed, and we provide key references for imaging protocols for a variety of cross-sectional imaging modalities.

Human fetal whole-body postmortem microfocus computed tomographic imaging

Perinatal autopsy is the standard method for investigating fetal death; however, it requires dissection of the fetus. Human fetal microfocus computed tomography (micro-CT) provides a generally more acceptable and less invasive imaging alternative for bereaved parents to determine the cause of early pregnancy loss compared with conventional autopsy techniques. In this protocol, we describe the four main stages required to image fetuses using micro-CT. Preparation of the fetus includes staining with the contrast agent potassium triiodide and takes 3-19 d, depending on the size of the fetus and the time taken to obtain consent for the procedure. Setup for imaging requires appropriate positioning of the fetus and takes 1 h. The actual imaging takes, on average, 2 h 40 min and involves initial test scans followed by high-definition diagnostic scans. Postimaging, 3 d are required to postprocess the fetus, including removal of the stain, and also to undertake artifact recognition and data transfer. This procedure produces high-resolution isotropic datasets, allowing for radio-pathological interpretations to be made and long-term digital archiving for re-review and data sharing, where required. The protocol can be undertaken following appropriate training, which includes both the use of micro-CT techniques and handling of postmortem tissue.

Developmental Differences Between the Limbic and Neocortical Telencephalic Wall: An Intrasubject Slice-Matched 3 T MRI-Histological Correlative Study in Humans

The purpose of the study was to investigate the interrelation of the signal intensities and thicknesses of the transient developmental zones in the cingulate and neocortical telencephalic wall, using T2-weighted 3 T-magnetic resonance imaging (MRI) and histological scans from the same brain hemisphere. The study encompassed 24 postmortem fetal brains (15-35 postconceptional weeks, PCW). The measurements were performed using Fiji and NDP.view2. We found that T2w MR signal-intensity curves show a specific regional and developmental stage profile already at 15 PCW. The MRI-histological correlation reveals that the subventricular-intermediate zone (SVZ-IZ) contributes the most to the regional differences in the MRI-profile and zone thicknesses, growing by a factor of 2.01 in the cingulate, and 1.78 in the neocortical wall. The interrelations of zone or wall thicknesses, obtained by both methods, disclose a different rate and extent of shrinkage per region (highest in neocortical subplate and SVZ-IZ) and stage (highest in the early second half of fetal development), distorting the zones' proportion in histological sections. This intrasubject, slice-matched, 3 T correlative MRI-histological study provides important information about regional development of the cortical wall, critical for the design of MRI criteria for prenatal brain monitoring and early detection of cortical or other brain pathologies in human fetuses.

Post-mortem confirmation of fetal brain abnormalities: challenges highlighted by the MERIDIAN cohort study

OBJECTIVES

To assess and analyse the concordance between post-mortem findings and in utero magnetic resonance imaging (iuMRI) in the MERIDIAN (MRI to enhance the diagnosis of fetal developmental brain abnormalities in utero) cohort.

DESIGN

Prospective cohort study.

SETTING

Fetal medicine units in the UK.

POPULATION

Pregnant women with a diagnosis of fetal brain abnormality identified on ultrasound at 18 weeks of gestation or later.

METHODS

All pregnancies from the MERIDIAN study that resulted in a abortion were included and the rate of uptake and success of post-mortem examinations were calculated. In the cases in which diagnostic information about the fetal brain was obtained by post-mortem, the results were compared with the diagnoses from iuMRI.

MAIN OUTCOME MEASURE

Outcome reference diagnosis from post-mortem examination.

RESULTS

A total of 155 from 823 pregnancies (19%) ended in a termination of pregnancy and 71 (46%) had post-mortem brain examinations, 62 of which were diagnostically adequate. Hence, the overall rate of successful post-mortem investigation was 40%, and for those cases there was a concordance rate of 84% between iuMRI and post-mortem examination. Detailed information is provided when the results of the post-mortem examination and the iuMRI study differed.

CONCLUSIONS

We have shown tissue-validation of radiological diagnosis is hampered by a low rate of post-mortem studies in fetuses aborted with brain abnormalities, a situation further compounded by a 12% rate of autopsy being technically unsuccessful. The agreement between iuMRI and post-mortem findings is high, but our analysis of the discrepant cases provides valuable clues for improving how we provide information for parents. TWEETABLE ABSTRACT: iuMRI should be considered a reliable indicator of fetal brain abnormalities when post-mortem is not performed.

Postmortem microfocus computed tomography for noninvasive autopsies: experience in >250 human fetuses

Background

Noninvasive imaging autopsy alternatives for fetuses weighing <500 grams are limited. Microfocus computed tomography has been reported as a viable option in small case series with the potential to avoid an invasive autopsy. Implementation of postmortem microfocus computed tomography in a large cohort as part of routine clinical service has yet been unreported, and realistic “autopsy prevention rates” are unknown.

Objective

This study aimed to describe the range of abnormalities detectable on fetal microfocus computed tomography in a clinical setting and additional findings identified on the antenatal ultrasound and to estimate the invasive autopsy avoidance rate (ie, cases in which imaging was sufficient to deem autopsy unnecessary).

Study Design

A prospective observational case series of all fetuses referred for microfocus computed tomography imaging at a single institution was conducted for 3 years (2016–2019). Imaging was reported by 2 pediatric radiologists before autopsy, with “decision to proceed” based on the specialist perinatal pathologists’ judgment and parental consent. Agreement rates between microfocus computed tomography and antenatal ultrasound were evaluated, and where feasible, diagnostic accuracy for microfocus computed tomography was calculated using autopsy as a reference standard.

Results

A total of 268 fetuses were included (2–350 grams body weight; 11–24 weeks’ gestation), with cause for demise in 122 of 268 (45.5%). Of the 122 fetuses, 64 (52.5%) exhibited fetal anomalies. Although 221 of 268 (82.5%) fetuses had consent for invasive autopsy, only 29 of the 221 (13.1%) underwent this procedure, which implied an autopsy avoidance rate of 192 of 221 (86.9%). Complete agreement was present for all brain, thoracic, and abdominal pathologies, whereas sensitivity and specificity for cardiac anomalies were 66.7% and 91.7%, respectively. Microfocus computed tomography and antenatal ultrasound agreement was found in 219 of 266 cases (81.9%), with partial agreement in 21 of 266 (7.9%) and disagreement in 26 of 266 (10.5%), mostly because of additional cardiac, soft tissue, or genitourinary findings by microfocus computed tomography, which were not seen on the ultrasound.

Conclusion

Fetal microfocus computed tomography imaging is a viable and useful tool for imaging early gestational fetuses and can avoid the need for invasive autopsy. Confirmation of antenatal diagnoses is achieved in most cases, and additional anomalies may also be detected.

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.

Maceration determines diagnostic yield of fetal and neonatal whole body post-mortem ultrasound

OBJECTIVES

To determine factors in nondiagnostic fetal and neonatal post-mortem ultrasound (PMUS) examinations.

METHODS

All fetal and neonatal PMUS examinations were included over a 5-year study period (2014-2019). Nondiagnostic image quality by body parts (brain, spine, thorax, cardiac, and abdomen) was recorded and correlated with patient variables. Descriptive statistics and logistic regression analyses were performed to identify significant factors for nondiagnostic studies.

RESULTS

Two hundred sixty-five PMUS examinations were included, with median gestational age of 22 weeks (12-42 wk), post-mortem weight of 363 g (16-4033 g), and post-mortem interval of 8 days (0-39 d). Diagnostic imaging quality was achieved for 178/265 (67.2%) studies. It was high for abdominal (263/265, 99.2%), thoracic (264/265, 99.6%), and spine (265/265, 100%) but lower for brain (210/265, 79.2%) and cardiac imaging (213/265, 80.4%). Maceration was the best overall predictor for nondiagnostic imaging quality (P < .0001). Post-mortem fetal weight was positively associated with cardiac (P = .0133) and negatively associated with brain imaging quality (P = .0002). Post-mortem interval was not a significant predictor.

CONCLUSIONS

Fetal maceration was the best predictor for nondiagnostic PMUS, particularly for brain and heart. Fetuses with marked maceration and suspected cardiac or brain anomalies should be prioritised for post-mortem MRI.

Novel imaging techniques to study postmortem human fetal anatomy: a systematic review on microfocus-CT and ultra-high-field MRI

Background

MRI and CT have been extensively used to study fetal anatomy for research and diagnostic purposes, enabling minimally invasive autopsy and giving insight in human fetal development. Novel (contrast-enhanced) microfocus CT (micro-CT) and ultra-high-field (≥ 7.0 T) MRI (UHF-MRI) techniques now enable micron-level resolution that combats the disadvantages of low-field MRI and conventional CT. Thereby, they might be suitable to study fetal anatomy in high detail and, in time, contribute to the postmortem diagnosis of fetal conditions.

Objectives

(1) To systematically examine the usability of micro-CT and UHF-MRI to study postmortem human fetal anatomy, and (2) to analyze factors that govern success at each step of the specimen preparation and imaging.

Method

MEDLINE and EMBASE were systematically searched to identify publications on fetal imaging by micro-CT or UHF-MRI. Scanning protocols were summarized and best practices concerning specimen preparation and imaging were enumerated.

Results

Thirty-two publications reporting on micro-CT and UHF-MRI were included. The majority of the publications focused on imaging organs separately and seven publications focused on whole body imaging, demonstrating the possibility of visualization of small anatomical structures with a resolution well below 100 μm. When imaging soft tissues by micro-CT, the fetus should be stained by immersion in Lugol’s staining solution.

Conclusion

Micro-CT and UHF-MRI are both excellent imaging techniques to provide detailed images of gross anatomy of human fetuses. The present study offers an overview of the current best practices when using micro-CT and/or UHF-MRI to study fetal anatomy for clinical and research purposes.

Key Points

• Micro-CT and UHF-MRI can both be used to study postmortem human fetal anatomy for clinical and research purposes.

• Micro-CT enables high-resolution imaging of fetal specimens in relatively short scanning time. However, tissue staining using a contrast solution is necessary to enable soft-tissue visualization.

• UHF-MRI enables high-resolution imaging of fetal specimens, without the necessity of prior staining, but with the drawback of long scanning time.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06543-8) contains supplementary material, which is available to authorized users.

Latest developments in post-mortem foetal imaging

A sustained decline in parental consent rates for perinatal autopsies has driven the development of less-invasive methods for death investigation. A wide variety of imaging modalities have been developed for this purpose and include post-mortem whole body magnetic resonance imaging (MRI), ultrasound, computed tomography (CT) and micro-focus CT techniques. These are also vital for "minimally invasive" methods, which include potential for tissue sampling, such as image guidance for targeted biopsies and laparoscopic-assisted techniques. In this article, we address the range of imaging techniques currently in clinical practice and those under development. Significant advances in high-field MRI and micro-focus CT imaging show particular promise for smaller and earlier gestation foetuses. We also review how MRI biomarkers such as diffusion-weighted imaging and organ volumetric analysis may aid diagnosis and image interpretation in the absence of autopsy data. Three-dimensional printing and augmented reality may help make imaging findings more accessible to parents, colleagues and trainees.

Postmortem fetal imaging: prospective blinded comparison of two-dimensional ultrasound with magnetic resonance imaging

OBJECTIVE

To compare the diagnostic rate and accuracy of 3-Tesla (T) postmortem magnetic resonance imaging (PM-MRI) and postmortem ultrasound (PM-US) in an unselected fetal population.

METHODS

We performed prospectively, in a blinded manner, 3-T PM-MRI and PM-US on 160 unselected fetuses at 13-41 weeks of gestation. All imaging was reported according to a prespecified template, for five anatomical regions: brain, thorax, heart, abdomen and spine. The rates of non-diagnostic results for PM-US and PM-MRI were compared and, for results that were diagnostic, we calculated sensitivity, specificity and concordance rates for each anatomical region, using conventional autopsy as the reference standard.

RESULTS

3-T PM-MRI performed significantly better than did PM-US overall and in particular for fetuses ≥ 20 weeks' gestation. Specifically, the non-diagnostic rates for PM-MRI vs PM-US were 4.4% vs 26.9% (7/160 vs 43/160; P < 0.001) for the brain, 5.2% vs 17.4% (8/155 vs 27/155; P < 0.001) for the thorax, 3.8% vs 30.6% (6/157 vs 48/157; P < 0.001) for the heart and 3.2% vs 23.6% (5/157 vs 37/157; P < 0.001) for the abdomen. For the spine, both techniques showed an equally low non-diagnostic rate. When both postmortem imaging techniques were diagnostic, they had similar accuracy, with no difference in sensitivity or specificity, and similar concordance with autopsy (PM-US, 79.5-96.5%; PM-MRI, 81.6-99.1%).

CONCLUSIONS

PM-MRI performed significantly better than PM-US in this unselected population, due mainly to a lower non-diagnostic rate. PM-MRI should remain the first-line imaging investigation for perinatal autopsy, but PM-US could be considered if MRI is not available, albeit with a higher non-diagnostic rate. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Impact of the delay between fetal death and delivery on the success of postmortem ultrasound following termination of pregnancy

OBJECTIVE

To evaluate the impact of the delay between fetal death and delivery on the nondiagnostic rates of post-mortem ultrasound (PM-US), following the termination of pregnancy (TOP).

METHODS

We reviewed 204 cases of fetal two-dimensional PM-US performed in our center as part of a post-mortem imaging research program, over the last 5 years. Informed consent was obtained from the parents for all cases. PM-US was performed and reported according to a prespecified template with operators blinded to the prenatal diagnosis. In order to calculate the precise delay between the fetal death and the delivery, we included 107 fetal TOP's ≥ 20 weeks of gestational age (GA), where feticide was performed using an injection of lidocaine 2% prior to induction of labor. Logistic regression analysis was conducted to analyze the impact of delay between fetal death and delivery (in hours), the GA at TOP (in weeks) and the method of feticide (intracardiac versus intraumbilical injection) on the PMUS nondiagnostic rates.

RESULTS

The delay between fetal death and delivery increased the nondiagnostic rate of PM-US for cerebral examinations (OR: 1.04, IC 95%: 1.01-1.08, p < .05). For PM-US cardiac examination, the delay did not influence the nondiagnostic rate. However, GA (OR: 1.25, IC 95%: 1.10-1.46, p < .01) and feticide with intracardiac injection (OR: 4.29, IC 95%: 1.68-12.02, p < .01) were associated with higher nondiagnostic rates. For noncardiac thoracic and abdominal examinations, none of the studied variables influenced the nondiagnostic rate.

CONCLUSION

The success rate of cerebral PM-US was influenced by the delay between fetal death and delivery, suggesting a possible advantage of performing the feticide closer to the delivery where the examination of the brain is planned. For cardiac abnormalities, feticide by intraumbilical, rather than intracardiac injection improves diagnostic rates of cardiac PM-US.

Micro-computed tomography: a new diagnostic tool in postmortem assessment of brain anatomy in small fetuses

PURPOSE

The aim of our study was to evaluate the postmortem micro-CT anatomy of early fetal human fetal brains, either in situ or isolated.

METHODS

We studied 12 ex vivo specimens, 9 whole human fetuses (9-18 GW), and 3 isolated samples (16-26 GW). Specimens were fixed in formalin, then immersed in Lugol solution. Images were evaluated by two neuroradiologists. The depiction of CNS structures was defined based on the comparison between micro-CT images and a reference histologic anatomical Atlas of human brain development.

RESULTS

Micro-CT provided informative high-resolution brain images in all cases, with the exception of one case (9 weeks) due to advanced maceration. All major CNS structures (i.e., brain hemispheres, layering, ventricles, germinal neuroepithelium, basal ganglia, corpus callosum, major cranial nerves, and structures of the head and neck) were recognizable.

CONCLUSIONS

Micro-CT imaging of the early fetal brain is feasible and provides high-quality images that correlate with the histological Atlas of the human brain, offering multiplanar and volumetric images that can be stored and shared for clinical, teaching, and research purposes.

Automated data extraction and report analysis in computer-aided radiology audit: practice implications from post-mortem paediatric imaging

AIM

To determine local departmental adherence to the paediatric post-mortem magnetic resonance imaging (MRI) protocols, using a customised automated computational approach.

MATERIALS AND METHODS

A retrospective review of 460 whole-body post-mortem MRI examinations performed at Great Ormond Street Hospital for Children over a 5.5-year period was assessed for adherence to a full or abbreviated imaging sequence protocol. A simple computer program was developed to batch process DICOM (digital imaging and communications in medicine) files, extracting imaging sequence details, followed by natural language processing (NLP) of authorised reports to automate information extraction of diagnostic image quality.

RESULTS

The program was able to extract study parameters from the entire dataset (approximately 80 GB of data) in a few hours, and retrieve information on diagnostic image quality using NLP with an overall diagnostic accuracy for data extraction of 96.7% (445/460, 95% confidence interval [CI]: 94.7-98%). The full imaging protocol was adhered to in 305/460 (66.3%) cases, and an abbreviated protocol in 140/460 (30.4%) cases. Overall, 423/460 (91.9%) of studies were of diagnostic quality. These included 298/305 (97.7%) of the full protocol, 111/140 (79.3%) of the abbreviated protocol. In only five cases were the examinations non-diagnostic for all body systems, all of whom weighed <100 g (24.7-72 g) and imaged using the abbreviated protocol.

CONCLUSION

The present study demonstrated a successful application of an automated approach for data collection for audit and quality assessment purposes using paediatric post-mortem imaging as a specific example. Re-audit of these data following change implementation will be straightforward now that the automated workflow is clearly established.

Potential clinical benefits and limitations of fetal virtopsy using high-field MRI at 7 Tesla versus stereomicroscopic autopsy to assess first trimester fetuses

OBJECTIVE

The aim of this study was to establish the diagnostic accuracy of high-field magnetic resonance imaging (MRI) at 7 Tesla (T) compared with that of stereomicroscopic autopsy for assessing first trimester fetuses.

METHODS

Nine consecutive cases of first trimester fetuses resulting from spontaneous and therapeutic pregnancy termination were considered. The cases were divided into two groups according to gestational age: the Embryo Group with cases of nine to 10 gestational weeks (GWs) and the Fetus Group with cases of 13 GWs. The first group was scanned using three-dimensional fast imaging with steady state precession (3D FISP), and the second group was scanned using a two-dimensional (2D) turbo spin-echo high-resolution T2-weighted imaging (T2 WI) protocol. A radiologist and two embryologists interpreted the images. All cases were evaluated by invasive autopsy, with pathologist blinded to the imaging results. In total, the database included 270 items for evaluation (9 cases × 30 structures/case).

RESULTS

The global agreement between fetal high-field virtopsy and microscopic or stereomicroscopic autopsy was evaluated using 225 evaluation items visible by both methods. Overall, using microscopic examination and stereomicroscopic autopsy as the gold standard, fetal high-field virtopsy had a sensitivity of 94.6% [95% CI, 87.2-98.3] and a specificity of 97.6% [95% CI, 95-98.8]. The positive predictive value (PPV) was 93% [95% CI, 85.7-96.6], and the negative predictive value (NPV) was 98.2% [95% CI, 95.7-99.4]. Cohen kappa coefficient of agreement was k = 0.92 [95% CI, 0.82-0.97], and the McNemar test showed p = 1.00.

CONCLUSIONS

Virtual autopsy using high-field MRI at 7 T can be considered a safe alternative approach to stereomicroscopic autopsy for the assessment of fetal structural anomalies at the end of the first trimester of pregnancy.

Is traditional perinatal autopsy needed after detailed fetal ultrasound and post-mortem MRI?

OBJECTIVE

To determine the additional yield from autopsy following prenatal ultrasound and post-mortem magnetic resonance imaging (PMMR) for structural abnormalities.

METHOD

PMMR was performed on consecutive fetuses over a 6-year period. Prenatal ultrasound and PMMR findings were categorised as concordant, partially concordant or discordant findings. The yield of new and clinically significant information from autopsy was assessed. Diagnostic accuracies for both modalities were calculated, using autopsy as reference standard.

RESULTS

Our study consisted of 81 fetuses. PMMR and prenatal ultrasound findings were concordant in 44/81 (54.3%), partially concordant in 26/81 (32.1%) and discordant in 11/81 (13.6%) cases. In 19/81 cases (23%), autopsy provided additional information, which appeared clinically significant in 12 cases. In 10 of those 12 cases, there was discordance between PMMR and ultrasound. In only 2 of 44 cases where ultrasound and PMMR were concordant, did autopsy provide clinically significant information. Diagnostic accuracy rates for ultrasound were sensitivity of 76.8% (66.6%, 84.6%), specificity of 92.5% (88.9%, 95.0%). For PMMR the sensitivity was 79.0% (68.9%, 86.5%), specificity 97.9% (95.5%, 99.0%). PMMR had a significantly higher concordance rate with autopsy than ultrasound (89.0 vs 93.8%; P < .001).

CONCLUSION

Where PMMR and ultrasound are concordant, there is little additional yield from autopsy.

Postmortem magnetic resonance imaging vs autopsy of second trimester fetuses terminated due to anomalies

Introduction

Our aim was to investigate the accuracy of postmortem fetal magnetic resonance imaging (MRI) compared with fetal autopsy in second trimester pregnancies terminated due to fetal anomalies. A secondary aim was to compare the MRI evaluations of two senior radiologists.

Material and methods

This was a prospective study including 34 fetuses from pregnancies terminated in the second trimester due to fetal anomalies. All women accepted a postmortem MRI and an autopsy of the fetus. Two senior radiologists performed independent evaluations of the MRI images. A senior pathologist performed the fetal autopsies. The degree of concordance between the MRI evaluations and the autopsy reports was estimated as well as the consensus between the radiologists.

Results

Thirty‐four fetuses were evaluated. Sixteen cases were associated with the central nervous system (CNS), five were musculoskeletal, one cardiovascular, one was associated with the urinary tract, and 11 cases had miscellaneous anomalies such as chromosomal aberrations, infections and syndromes. In the 16 cases related to the CNS, both radiologists reported all or some, including the most clinically significant anomalies in 15 (94%; CI 70%‐100%) cases. In the 18 non‐CNS cases, both radiologists reported all or some, including the most clinically significant anomalies in six (33%; CI 5%‐85%) cases. In 21 cases (62%; CI 44%‐78%), both radiologists held opinions that were consistent with the autopsy reports. The degree of agreement between the radiologists was high, with a Cohen's Kappa of 0.87.

Conclusions

Postmortem fetal MRI can replace autopsy for second trimester fetuses with CNS anomalies. For non‐CNS anomalies, the concordance is lower but postmortem MRI can still be of value when autopsy is not an option.

Postmortem examination of human fetuses: comparison of two-dimensional ultrasound with invasive autopsy

OBJECTIVE

To assess the diagnostic accuracy of postmortem ultrasound performed by operators blinded to prenatal findings and to invasive autopsy results in fetuses at different gestational ages and to investigate the effect of various parameters on its diagnostic success.

METHODS

We performed postmortem two-dimensional ultrasound examination, blinded to clinical details, on 163 fetuses at 13-42 weeks' gestation. Logistic regression analysis was used to investigate the effect of: (i) gestational age at postmortem ultrasound, (ii) presence of maceration and (iii) mode of death, on whether the exam succeeded or failed to reach a diagnosis. In 123 cases in which invasive autopsy was available, the diagnostic accuracy of ultrasound in detecting major organ abnormalities was evaluated, using invasive autopsy as the gold standard.

RESULTS

For the fetal brain, postmortem ultrasound exam was non-diagnostic in significantly more fetuses with maceration (39.5%; 17/43) vs those without maceration (20.0%; 24/120) (P = 0.013). For the fetal thorax, the exam was non-diagnostic in 34.1% (15/44) of fetuses < 20 weeks of gestation and in 10.9% (13/119) of fetuses ≥ 20 weeks (P < 0.001). For the heart and abdominal organs, there was no association between non-diagnostic postmortem ultrasound and the variables tested. For fetuses < 20 weeks, specificity of postmortem ultrasound examination was 83.3% for detection of anomalies of the brain, 68.6% for the thorax and 77.4% for the heart. For fetuses ≥ 20 weeks, sensitivity and specificity were, respectively, 61.9% and 74.2% for detection of anomalies of the brain, 29.5% and 87.0% for the thorax and 65.0% and 83.1% for the heart. For the fetal abdominal organs, sensitivity was 60.7% and specificity 75.8%, and postmortem ultrasound was particularly useful for detection of abnormalities of the kidneys, irrespective of gestational age.

CONCLUSION

Although maceration may lead to failure of postmortem ultrasound examination in some cases, this technique achieves diagnostically acceptable levels of accuracy for fetal brain and abdominal organs, compared with conventional autopsy. It may therefore play a role as a first-line examination before other virtual autopsy techniques are indicated. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

High resolution isotropic diffusion imaging in post-mortem neonates: a feasibility study

OBJECTIVE:

To investigate the potential of advanced diffusion weighted imaging (DWI) in post-mortem MRI (PMMR) at 3T.

METHODS:

We acquired PMMR brain and body imaging in 12 neonates, mean gestational age 33.4 weeks (range 29-37 weeks) at 3T and 1.5T. Head and body diffusion imaging at 1.5T consisted of bipolar diffusion encoding and single-shot spin-echo echo-planar imaging (SE-EPI) for acquisition (echo time (TE) 96 ms; repetition time (TR) 2700 ms; voxel size 1.8 x 1.8 mm in-plane with slice thickness 5 mm; b-values of 500 and 1000 s/mm² applied in three orthogonal directions; total acquisition time 2:12). A whole-body 3T diffusion imaging protocol using monopolar diffusion encoding and simultaneous multislice EPI acquisition with gradients applied in 12 uniformly distributed directions was obtained (TE 53.4 ms; TR 5600 ms; 1.8 mm isotropic; multiband factor 2; b-values of 250, 750, 1250 and 1750 s/mm²; acquisition time 2:09 for a single b-value).

RESULTS:

There was significant improvement in image quality in multiband, multislice diffusion PMMR protocol. On visual assessment of image quality, 1.5T DWI scored poorly (mean 2.4 SD ± 0.47), and all 3T b-values individually scored significantly higher (p < 0.001) apart from b = 250 s/mm² which was not significantly different.

CONCLUSION:

Recent advances in diffusion sequences and hardware utilising higher field strengths and gradient performance allows whole-body diffusion PMMR imaging at high resolution with improved image quality compared to the current clinical approach.

ADVANCES IN KNOWLEDGE:

We have demonstrated feasibility of a multislice, multiband quantitative diffusion imaging sequence in the perinatal post-mortem setting. This will allow more detailed and quantitative clinical PMMR investigations using diffusion MRI in the future.

The use of whole body diffusion-weighted post-mortem magnetic resonance imaging in timing of perinatal deaths

Objectives

Diffusion-weighted MRI provides information regarding body water movement following death, which may be an imaging marker of post-mortem interval (time since death; PMI) or maceration (degree of tissue degradation during intra-uterine retention) in perinatal deaths. Our aim was to evaluate the relationship between maceration, PMI and body organ apparent diffusion coefficient (ADC) values in a cohort of subjects across a wide gestational range.

Materials

Whole body post-mortem MRI with diffusion-weighted imaging (DWI) sequences were performed at 1.5 T, with b values of 0, 500 and 1000 mm²/s. Mean ADC values were calculated from regions of interest (ROIs) placed in the lungs, myocardium, spleen, renal cortex, liver and psoas muscle by two independent readers. Multivariable regression analysis was performed against PMI, gestational age, post-mortem weight, maceration score and gender.

Results

Eighty perinatal deaths were imaged with mean gestational age of 32 weeks (18–41 weeks), of which 49 (61.3%) were male. The mean PMI was 8 days (1–18 days). Maceration scores were statistically significant predictive factors for ADC values in all included body organs except the lungs, but PMI was not a predictor for ADC values in any body organ. In the absence of maceration (n = 14), PMI was not statistically associated with ADC values in any of the body areas. The ratio of agreement in the majority of body areas was close to 1 (range between 0.95 and 1.10).

Conclusion

Maceration, not PMI, is significantly associated with ADC values in perinatal deaths. Further research is needed to understand organ-specific changes in the post-mortem period.

Postmortem fetal magnetic resonance imaging: where do we stand?

Abstract

Postmortem fetal magnetic resonance imaging (PMFMRI) is increasingly used thanks to its good overall concordance with histology paralleling the rising incidence of parental refusal of autopsy. The technique could become a routine clinical examination but it needs to be standardized and conducted by trained radiologists. Such radiologists should be aware of not only the (congenital and acquired) anomalies that can involve the fetus, but also of the “physiological” postmortem changes. In this article, we intend to focus on the contribution of PMFMRI based on the existing literature and on our own experience, as we presently perform the technique routinely in our clinical practice.

Key Points

• Concordance rates between PMFMRI and autopsy are high for detecting fetal pathologies.

• PMFMRI is more acceptable for parents than traditional autopsy.

• PMFMRI is becoming widely used as a part of the postmortem investigations.

• A dedicated radiologist needs to learn to interpret correctly a PMFMRI.

• PMFMRI can be easily realized in daily clinical practice.

Postmortem microfocus computed tomography for early gestation fetuses: a validation study against conventional autopsy

BACKGROUND

Perinatal autopsy provides useful clinical information in up to 40% of cases. However, there is a substantial unmet clinical need with regards to postmortem investigation of early gestation fetal loss for parents for whom standard autopsy is either not available or not acceptable. Parents dislike the invasive nature of autopsy, but current clinical imaging techniques do not provide high-enough imaging resolution in small fetuses. We hypothesized that microfocus computed tomography, which is a rapid high-resolution imaging technique, could give accurate diagnostic imaging after early gestation fetal loss.

OBJECTIVE

The objective of the study was to evaluate the diagnostic accuracy of microfocus computed tomography for noninvasive human fetal autopsy for early gestation fetuses, with the use of conventional autopsy as the reference standard.

STUDY DESIGN

We compared iodinated whole body microfocus computed tomography in 20 prospectively recruited fetuses (11-21 weeks gestation from 2 centers) with conventional autopsy in a double-blinded manner for a main diagnosis and findings in specific body organs. Fetuses were prepared with 10% formalin/potassium tri-iodide. Images were acquired with a microfocus computed tomography scanner with size-appropriate parameters. Images were evaluated independently by 2 pediatric radiologists, who were blinded to formal perinatal autopsy results, across 40 individual indices to reach consensus. The primary outcome was agreement between microfocus computed tomography and conventional autopsy for overall diagnosis.

RESULTS

Postmortem whole body fetal microfocus computed tomography gave noninvasive autopsy in minutes, at a mean resolution of 27μm, with high diagnostic accuracy in fetuses at <22 weeks gestation. Autopsy demonstrated that 13 of 20 fetuses had structural abnormalities, 12 of which were also identified by microfocus computed tomography (92.3%). Overall, microfocus computed tomography agreed with overall autopsy findings in 35 of 38 diagnoses (15 true positive, 18 true negative; sensitivity 93.8% [95% confidence interval, 71.7-98.9%], specificity 100% [95% confidence interval, 82.4-100%]), with 100% agreement for body imaging diagnoses. Furthermore, after removal of nondiagnostic indices, there was agreement for 700 of 718 individual body organ indices that were assessed on microfocus computed tomography and autopsy (agreement, 97.5%; 95% confidence interval, 96.1-98.4%), with no overall differences between fetuses at ≤14 or >14 weeks gestation (agreement, 97.2% and 97.9%, respectively). Within first-trimester fetal loss cases (<14 weeks gestation), microfocus computed tomography analysis yielded significantly fewer nondiagnostic indices than autopsy examination (22/440 vs 48/348, respectively; P<.001).

CONCLUSION

Postmortem whole-body fetal microfocus computed tomography gives noninvasive, detailed anatomic examinations that are achieved in minutes at high resolution. Microfocus computed tomography may be preferable to magnetic resonance imaging in early gestation fetuses and may offer an acceptable method of examination after fetal loss for parents who decline invasive autopsy. This will facilitate autopsy and subsequent discussions between medical professionals who are involved in patient care and counselling for future pregnancies.

High resolution post-mortem MRI of non-fixed in situ foetal brain in the second trimester of gestation: Normal foetal brain development

PURPOSE

To describe normal foetal brain development with high resolution post-mortem MRI (PMMRI) of non-fixed foetal brains.

METHODS

We retrospectively collected PMMRIs of foetuses without intracranial abnormalities and chromosomal aberrations studied after a termination of pregnancy due to extracranial abnormalities or after a spontaneous intrauterine death. PMMRIs were performed on a 3-T scanner without any fixation and without removing the brain from the skull. All PMMRIs were evaluated in consensus by two neuroradiologists.

RESULTS

Our analysis included ten PMMRIs (median gestational age (GA): 21 weeks; range: 17-28 weeks). At 19 and 20 weeks of GA, the corticospinal tracts are recognisable in the medulla oblongata, becoming less visible from 21 weeks. Prior to 20 weeks the posterior limb of the internal capsule (PLIC) is more hypointense than surrounding deep grey nuclei; starting from 21 weeks the PLIC becomes isointense, and is hyperintense at 28 weeks. From 19-22 weeks, the cerebral hemispheres show transient layers: marginal zone, cortical plate, subplate, and intermediate, subventricular and germinal zones.

CONCLUSION

PMMRI of non-fixed in situ foetal brains preserves the natural tissue contrast and skull integrity. We assessed foetal brain development in a small cohort of foetuses, focusing on 19-22 weeks of gestation.

KEY POINTS

• Post-mortem magnetic resonance imaging (PMMRI) of non-fixed head is feasible. • PMMRI of unfixed in situ foetal brains preserves the natural tissue contrast. • PMMRI provide a good depiction of the normal foetal brain development. • PMMRI of unfixed in situ foetal brains preserves the skull integrity. • PMMRI pattern of foetal brain development at early gestational age is described.