Quantification of maceration changes using post mortem MRI in fetuses

Gray-white matter contrast reversal on T1-weighted spin-echo in postmortem brain

PURPOSE

The image contrast of postmortem magnetic resonance imaging (MRI) may differ from that of antemortem MRI because of circulator arrest, changes in postmortem tissue, and low-body-temperature scanning conditions. In fact, we have found that the signal intensity of white matter (WM) on T1-weighted spin-echo (T1WSE) images of the postmortem brain was lower than that of gray matter (GM), which resulted in image contrast reversal between GM and WM relative to the living brain. However, the reason for this phenomenon is unclear. Therefore, the aim of this study is to clarify the reason why image contrast reversal occurs between GM and WM of the postmortem brain.

MATERIALS AND METHODS

Twenty-three corpses were included in the study (mean age, 60.6 years; range: 19-60 years; mean rectal temperature at scan, 6.9℃; range: 4-11℃). On a 1.5 T MRI system, postmortem T1W-SE MRI of the brain was conducted in the 23 corpses prior to medico-legal autopsy. Next, T1 and T2 of the GM and WM at the level of the basal ganglia were determined in the same participants using inversion recovery and multiple SE sequences, respectively. The proton density (PD) was also calculated from the T1 and T2 images (in the same slice).

RESULTS

T1W-SE image contrast between the GM and WM of all postmortem brains was inverted relative to the living brain. T1 (579 ms in GM and 307 ms in WM) and PD (64 in GM and 44 in WM) of the postmortem brain decreased compared with the living brain. While T1 of WM/GM remained below 1 even postmortem, the PD of WM/GM decreased. T2 (110 ms in GM and 98 ms in WM) of the postmortem brain did not differ from the living brain.

CONCLUSION

The decrease in PD of WM/GM in the postmortem brain may be the major driver of contrast reversal between the GM and WM relative to the living brain.

Body weight-based iodinated contrast immersion timing for human fetal postmortem microfocus computed tomography

Objectives

The aim of this study was to evaluate the length of time required to achieve full iodination using potassium tri-iodide as a contrast agent, prior to human fetal postmortem microfocus computed tomography (micro-CT) imaging.

Methods

Prospective assessment of optimal contrast iodination was conducted across 157 human fetuses (postmortem weight range 2-298 g; gestational age range 12-37 weeks), following micro-CT imaging. Simple linear regression was conducted to analyse which fetal demographic factors could produce the most accurate estimate for optimal iodination time.

Results

Postmortem body weight (r2 = 0.6435) was better correlated with iodination time than gestational age (r2 = 0.1384), producing a line of best fit, y = [0.0304 × body weight (g)] - 2.2103. This can be simplified for clinical use whereby immersion time (days) = [0.03 × body weight (g)] - 2.2. Using this formula, for example, a 100-g fetus would take 5.2 days to reach optimal contrast enhancement.

Conclusions

The simplified equation can now be used to provide estimation times for fetal contrast preparation time prior to micro-CT imaging and can be used to manage service throughput and parental expectation for return of their fetus.

Advances in knowledge

A simple equation from empirical data can now be used to estimate preparation time for human fetal postmortem micro-CT imaging.

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.

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.

Improving uptake of perinatal autopsy

PURPOSE OF REVIEW

Uptake of perinatal autopsy has declined in the West over the past 30 years, largely because of reduced parental acceptance of a traditional invasive autopsy. Several studies have recently investigated the decline to identify the key factors and how they may be mitigated.

RECENT FINDINGS

Three main themes were identified that have been found to improve uptake of perinatal autopsy: improved communication, in particular ensuring the consent process was conducted as a conversation with time spent talking through the procedure and allowing time for questions; health professional training to ensure staff discussing autopsy with parents have adequate understanding of the procedure and are able to convey confidence and empathy; and availability of less invasive autopsy, including noninvasive as well as minimally invasive options. These should be offered alongside standard autopsy, which some parents may still prefer.

SUMMARY

This review highlights that the discussions that take place, and the options that are available to parents, can profoundly impact whether or not they consent to autopsy investigation. Further research should focus on the impact of offering less invasive options as well as evaluating the training and support materials that have recently been developed.

Determining the effect of water temperature on the T1 and T2 relaxation times of the lung tissue at 9.4 T MRI: A drowning mouse model

Japanese individuals have a unique culture of soaking in a bathtub, and forensic pathologists have experienced fatal cases due to drowning. However, T1 and T2 relaxation times of a drowning lung are poorly documented. In the present study, we investigated the relationship between drowning water temperature and T1 and T2 relaxation times of drowning lung tissues at 9.4 T MRI (Bruker, BioSpec94/20USR). The mice used as animal drowning models were directly submerged in freshwater. Water temperature was set to 8 °C-10 °C (cold), 20 °C-22 °C (normal), 30 °C, and 45 °C. The regions of interest (ROIs) on the axial section of the third slice were set at the central and peripheral areas of each-the left and the right-lung. T1 relaxation times measured immediately after death differed by the presence or absence of soaking water, except in case of cold water temperature. In the drowning groups, T1 relaxation time showed a linear dependency on water temperature. By contrast, T2 relaxation time was almost constant regardless of the presence of drowning under the same temperature condition; when compared in the lung areas of the same individuals, the times were uniformly reduced in drowning models. To minimize the effects of hypostasis and decomposition, we performed measurements immediately after death and were able to determine the noticeable difference in drowning water temperature. These results may be useful for qualitative assessments of a drowning lung and may serve as a basis when imaging the human body during forensic autopsy cases.

Postmortem MRI Evaluation of Maceration Degree of Deceased Fetus

We studied the possibilities of postmortem MRI for assessing the degree of maceration and determining the duration of intrauterine fetal death. Postmortem radiological and pathoanatomic study of the bodies of 38 stillbirths who died antenatally (main group, n=31) and intranatally (control group, n=5), who were born at gestational periods of 22-40 weeks was performed. Before the autopsy, MRI was performed in standard T1 and T2 modes. The tissue of the liver, kidney, brain, femoral muscle, lung, and skin in the hip, abdomen, and skull were studied on T1- and T2-weighted images (WI), followed by calculation of the of MR signal intensity ratio in T2- and T1-WI (SIR). The duration of intrauterine fetal death was determined based on the results of autopsy and analysis of histological preparations. It was found that the calculated values of SIR depended on the evaluated organ and the duration of intrauterine fetal death. Unfortunately, the revealed dynamics of changes in SIR does not allow unambiguous assessment of the severity of maceration processes and, accordingly, the time of fetal death due to its non-linear nature. Nevertheless, the use of SIR indicators of several organs and areas of the body makes it easier to determine the duration of intrauterine fetal death and, hence, to clarify the links of thanatogenesis of the stillborn. The advantages of post-mortem MRI compared to autopsy include non-invasive nature of the study, the possibility of archiving and subsequent multiple delayed analysis of tomograms, as well as the speed of MRI analysis, in contrast to microscopic stage of pathological examination associated with the need to prepare histological preparations.

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.

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.

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.

Perinatal post mortem ultrasound (PMUS): a practical approach

Declining rates of consent for standard perinatal autopsy has led to a rise in interest for postmortem imaging as an alternative, non-invasive method for investigation of childhood and perinatal deaths. Whilst much interest has focussed on cross-sectional techniques such as postmortem CT (PMCT) or MRI (PMMR), other modalities including postmortem ultrasound (PMUS) have been shown to have reasonable diagnostic accuracy rates, with the added benefit of being more readily accessible and affordable. There is little published information or formal guidance available on preparation for postmortem perinatal ultrasound, views to be obtained and differentiating normal postmortem change from potential abnormalities.

This article will focus on the role of perinatal postmortem ultrasound as an alternative imaging method for non-invasive autopsy, with emphasis on imaging technique, practical considerations and commonly encountered case examples.

Intrauterine fetal MR versus postmortem MR imaging after therapeutic termination of pregnancy: evaluation of the concordance in the detection of brain abnormalities at early gestational stage

BACKGROUND AND PURPOSE

Fetal postmortem MR Imaging (pmMRI) has been recently used as an adjuvant tool to conventional brain autopsy after termination of pregnancy (TOP). Our purpose was to compare the diagnostic performance of intrauterine MRI (iuMRI) and pmMRI in the detection of brain anomalies in fetuses at early gestational age (GA).

MATERIAL AND METHODS

We retrospectively collected 53 fetuses who had undergone iuMRI and pmMRI for suspected brain anomalies. Two pediatric neuroradiologists reviewed iuMRI and pmMRI examinations separately and then together. We used Cohen's K to assess the agreement between pmMRI and iuMRI. Using the combined evaluation iuMRI+pMRI as the reference standard, we calculated the "correctness ratio." We used Somers' D to assess the cograduation between postmortem image quality and time elapsed after fetus expulsion.

RESULTS

Our data showed high agreement between iuMRI and pmMRI considering all the categories together, for both observers (K1 0.84; K2 0.86). The correctness ratio of iuMRI and pmMRI was 79% and 45% respectively. The major disagreements between iuMRI and pmMRI were related to postmortem changes as the collapse of liquoral structures and distorting phenomena. We also found a significant cograduation between the time elapsed from expulsion and pmMRI contrast resolution and distortive phenomena (both p < 0.001).

CONCLUSIONS

Our study demonstrates an overall high concordance between iuMRI and pmMRI in detecting fetal brain abnormalities at early GA. Nevertheless, for the correct interpretation of pmMRI, the revision of fetal examination seems to be crucial, in particular when time elapsed from expulsion is longer than 24 h.

KEY POINTS

• IuMRI and pmMRI showed overall high concordance in detecting fetal brain abnormalities at early GA. • PmMRI corroborated the antemortem diagnosis and it could be a valid alternative to conventional brain autopsy, only when the latter cannot be performed. • Some caution should be taken in interpreting pmMR images when performed after 24 h from fetal death.

Neonatal imaging using an on-site small footprint MR scanner

With its soft-tissue definition, multiplanar capabilities and advanced imaging techniques, magnetic resonance imaging (MRI) for neonatal care can provide better understanding of pathology, allowing for improved care and counseling to families. However, MR imaging in neonates is often difficult due to patient instability and the complex support necessary for survival. In our institution, we have installed a small footprint magnet in the neonatal intensive care unit (NICU) to minimize patient risks and provide the ability to perform MR imaging safely in this population. With this system, we have been able to provide more information with regard to central nervous system disorders, abdominal pathology, and pulmonary and airway abnormalities, and have performed postmortem imaging as an alternative or supplement to pathological autopsy. In our experience, an MR scanner situated within the NICU has allowed for safer and more expedited imaging of this vulnerable population.

Perinatal death investigations: What is current practice?

Perinatal death (PD) is a devastating obstetric complication. Determination of cause of death helps in understanding why and how it occurs, and it is an indispensable aid to parents wanting to understand why their baby died and to determine the recurrence risk and management in subsequent pregnancy. Consequently, a perinatal death requires adequate diagnostic investigation. An important first step in the analysis of PD is to identify the case circumstances, including relevant details regarding maternal history, obstetric history and current pregnancy (complications are evaluated and recorded). In the next step, placental examination is suggested in all cases, together with molecular cytogenetic evaluation and fetal autopsy. Investigation for fetal-maternal hemorrhage by Kleihauer is also recommended as standard. In cases where parents do not consent to autopsy, alternative approaches such as minimally invasive postmortem examination, postmortem magnetic resonance imaging, and fetal photographs are good alternatives. After all investigations have been performed it is important to combine findings from the clinical review and investigations together, to identify the most probable cause of death and counsel the parents regarding their loss.