Development of the minimally invasive paediatric & perinatal autopsy

Introduction Perinatal autopsy contributes useful clinical information to patient management in approximately 40% of cases but remains poorly accepted due to parental concerns regarding disfigurement. Post-mortem imaging is an alternative, but 1.5 T MRI lacks resolution below 18 gestational weeks. Additionally, the Royal College of Pathologists autopsy guidelines recommend extensive tissue sampling as part of the investigation of fetal loss, which imaging alone cannot provide. Possible mitigating strategies include micro-CT for phenotyping small fetuses and laparoscopic techniques to obtain tissue samples. Interrogation of the evidence base for tissue sampling in different clinical scenarios is necessary to develop evidence-based practice and recommendations. Methods Minimally Invasive Autopsy with Laparoscopy (MinImAL) was performed in 103 cases. Micro-CT was optimised in extracted organs and the diagnostic accuracy evaluated in 20 fetuses. The Great Ormond Street Autopsy Database was retrospectively interrogated to investigate the yield of internal examination and visceral histology to the cause of death in 5,311 cases. Results MinImAL examination is reliable (97.8% successfully completed, 91/93) with good tissue sampling success rates (100% in lung, kidney, heart). Micro-CT offers an accurate method of scanning small fetuses (97.5% agreement with autopsy, 95% CI, 96.6-98.4) with fewer non-diagnostic indices than standard autopsy in < 14 weeks gestation (22/440 vs 48/348 respectively; p<0.001). Histology of macroscopically normal viscera is valuable in the investigation of infant and childhood deaths. However, it provides almost no useful information relevant to cause of death or main diagnosis (<1%) in fetal cases. Conclusions MinImAL examination offers a reliable method of internal examination and tissue sampling, which may be acceptable when standard autopsy is declined. Micro-CT provides an accurate, non-invasive method for phenotyping early gestation fetal anatomy. Histological sampling of macroscopically normal visceral organs is valuable when investigating infant or child deaths but of limited value in fetal loss and hence should not be routinely performed

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

Post-mortem micro-CT for non-invasive autopsies: Experience in > 250 human fetuses

BACKGROUND: Non-invasive 'imaging' autopsy alternatives for fetuses weighing <500g are limited. Micro-CT has been reported as a viable option in small case series with the potential to avoid an invasive autopsy. Implementation of post-mortem micro-CT in a large cohort, as part of routine clinical service has yet been unreported and realistic 'autopsy prevention rates' are unknown. OBJECTIVE: To describe the range of abnormalities detectable on fetal micro-CT in a clinical setting, additional findings identified over the antenatal ultrasound, and to estimate the invasive 'autopsy avoidance rate' (i.e. cases where imaging was sufficient to deem autopsy unnecessary). STUDY DESIGN: A prospective observational case series was conducted over 3 years (2016 - 2019), of all fetuses referred for micro-CT imaging at a single institution. Imaging was reported by two paediatric radiologists prior to autopsy, with "decision to proceed" based on specialist perinatal pathologists' judgement and parental consent. Agreement rates between micro-CT and antenatal ultrasound were evaluated, and where feasible, diagnostic accuracy for micro-CT was calculated using autopsy as reference standard. RESULTS: 268 fetuses were included (2-350g weight; 11 - 24 weeks gestation), with cause for demise in 122/268 (45.5%). Of these, 64/122 (52.5%) demonstrated fetal anomalies. Although 221/268 (82.5%) had consent for invasive autopsy, only 29/221 (13.1%) underwent this procedure giving an 'autopsy avoidance rate' of 192/221 (86.9%). Complete agreement was present for all brain, thoracic and abdominal pathologies, whilst sensitivity and specificity for cardiac anomalies were 66.7% and 91.7% respectively. Micro-CT and antenatal ultrasound agreement was found in 219/266 (81.9%) cases, with partial agreement in 21/266 (7.9%) and disagreement in 26/266 (10.5%), mostly due to additional cardiac, soft tissue or genito-urinary findings by micro-CT, not seen at ultrasound. CONCLUSIONS: Fetal micro-CT imaging is a viable and useful tool for imaging early gestational fetuses, and can avoid the need for invasive autopsy. Confirmation of antenatal diagnoses are achieved in the majority, and additional anomalies may also be detected

Routine placental histopathology findings from women testing positive for SARS-CoV-2 during pregnancy: Retrospective cohort comparative study

OBJECTIVE: To assess the impact of maternal Coronavirus disease 2019 (COVID-19) infection on placental histopathological findings in an unselected population and evaluate the potential effect on the fetus, including the possibility of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). DESIGN: Retrospective cohort comparative study of placental histopathological findings in patients with COVID-19, compared with controls. SETTING: During the COVID-19 pandemic, placentas were studied from women at University College Hospital London who reported and/or tested positive for COVID-19. POPULATION: Of 10 508 deliveries, 369 (3.5%) women had COVID-19 during pregnancy, with placental histopathology available for 244 women. METHODS: Retrospective review of maternal and neonatal characteristics, where placental analysis had been performed. This was compared with available, previously published, histopathological findings from placentas of unselected women. MAIN OUTCOME MEASURES: Frequency of placental histopathological findings and relevant clinical outcomes. RESULTS: Histological abnormalities were reported in 117 of 244 (47.95%) cases, with the most common diagnosis being ascending maternal genital tract infection. There was no statistically significant difference in the frequency of most abnormalities compared with controls. There were four cases of COVID-19 placentitis (1.52%, 95% CI 0.04%-3.00%) and one possible congenital infection, with placental findings of acute maternal genital tract infection. The rate of fetal vascular malperfusion (FVM), at 4.5%, was higher compared with controls (p = 0.00044). CONCLUSIONS: In most cases, placentas from pregnant women infected with SARS-CoV-2 virus do not show a significantly increased frequency of pathology. Evidence for transplacental transmission of SARS-CoV-2 is lacking from this cohort. There is a need for further study into the association between FVM, infection and diabetes

Dynamic Changes in Microvascular Density Can Predict Viable and Non-Viable Areas in High-Risk Neuroblastoma

Despite aggressive treatments, the prognosis of high-risk NB remains poor. Surgical oncology needs innovative intraoperative devices to help surgeons discriminate malignant tissue from necrotic and surrounding healthy tissues. Changes within the tumor vasculature could be used intraoperatively as a diagnostic tool to guide surgical resection. Here, we retrospectively analyzed the mean vascular density (MVD) of different NB subtypes at diagnosis and after induction chemotherapy using scanned histological samples. One patient was prospectively enrolled, and an ex vivo photoacoustic imaging (PAI) scan was performed on two representative sections to assess its capacity to discriminate different tumor regions. We found that post-chemotherapy, viable areas of differentiating NBs and ganglioneuroblastomas are associated with higher MVD compared to poorly differentiated NBs. Early necrotic regions showed higher MVD than late necrotic and viable regions. Finally, calcified areas showed significantly lower MVD than any other histological component. The acquired PAI images showed a good high-resolution ex vivo 3D delineation of NB margins. Overall, these results suggest that a high-definition preclinical imaging device such as PAI could potentially be exploited to guide surgical resection by identifying different vasculature signatures

Dynamic Changes in Microvascular Density Can Predict Viable and Non-Viable Areas in High-Risk Neuroblastoma

Despite aggressive treatments, the prognosis of high-risk NB remains poor. Surgical oncology needs innovative intraoperative devices to help surgeons discriminate malignant tissue from necrotic and surrounding healthy tissues. Changes within the tumor vasculature could be used intraoperatively as a diagnostic tool to guide surgical resection. Here, we retrospectively analyzed the mean vascular density (MVD) of different NB subtypes at diagnosis and after induction chemotherapy using scanned histological samples. One patient was prospectively enrolled, and an ex vivo photoacoustic imaging (PAI) scan was performed on two representative sections to assess its capacity to discriminate different tumor regions. We found that post-chemotherapy, viable areas of differentiating NBs and ganglioneuroblastomas are associated with higher MVD compared to poorly differentiated NBs. Early necrotic regions showed higher MVD than late necrotic and viable regions. Finally, calcified areas showed significantly lower MVD than any other histological component. The acquired PAI images showed a good high-resolution ex vivo 3D delineation of NB margins. Overall, these results suggest that a high-definition preclinical imaging device such as PAI could potentially be exploited to guide surgical resection by identifying different vasculature signatures

Micro-computed tomography (micro-CT) for the assessment of myocardial disarray, fibrosis and ventricular mass in a feline model of hypertrophic cardiomyopathy.

Micro-computed tomography (micro-CT) is a high-resolution imaging modality that provides accurate tissue characterization. Hypertrophic cardiomyopathy (HCM) occurs as a spontaneous disease in cats, and is characterized by myocardial hypertrophy, disarray and fibrosis, as in humans. While hypertrophy/mass (LVM) can be objectively measured, fibrosis and myocyte disarray are difficult to assess. We evaluated the accuracy of micro-CT for detection and quantification of myocardial disarray and fibrosis by direct comparison with histopathology. 29 cat hearts (12 normal and 17 HCM hearts) underwent micro-CT and pathologic examination. Myocyte orientation was assessed using structure tensor analysis by determination of helical angle (HA), fractional anisotropy (FA) and myocardial disarray index (MDI). Fibrosis was segmented and quantified based on comparison of gray-scale values in normal and fibrotic myocardium. LVM was obtained by determining myocardial volume. Myocardial segments with low FA, low MDI and disruption of normal HA transmural profile on micro-CT were associated with myocardial disarray on histopathology. FA was consistently lower in HCM than normal hearts. Assessment of fibrosis on micro-CT closely matched the histopathologic evaluation. LVM determined by micro-CT was higher in HCM than normal hearts. Micro-CT can be used to detect and quantify myocardial disarray and fibrosis and determine myocardial mass in HCM

Feature Selection To Facilitate Surgical Planning From MRI Of Placenta Accreta Spectrum Disorder

Feature Selection Models provide a ranking of pathological MRI markers able to predict the outcome of Placenta Accreta Spectrum Disorder, which could be used to aid in clinical decision-making and improve maternal outcome. The potential being to reduce the workload of radiologists by establishing the most clinically relevant pathological MRI markers that predict outcome. Our results found three pathological markers to have the highest ranking to the outcomes with an average accuracy of 75% using a Random Forest Selection Model and Boruta algorithm

Photoacoustic imaging of the human placental vasculature

Minimally invasive fetal interventions require accurate imaging from inside the uterine cavity. Twin‐to‐twin transfusion syndrome (TTTS), a condition considered in this study, occurs from abnormal vascular anastomoses in the placenta that allow blood to flow unevenly between the fetuses. Currently, TTTS is treated fetoscopically by identifying the anastomosing vessels, and then performing laser photocoagulation. However, white light fetoscopy provides limited visibility of placental vasculature, which can lead to missed anastomoses or incomplete photocoagulation. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, two PA systems were used to visualize chorionic (fetal) superficial and subsurface vasculature in human placentas. The first system comprised an optical parametric oscillator for PA excitation and a 2D Fabry‐Pérot cavity ultrasound sensor; the second, light emitting diode arrays and a 1D clinical linear‐array ultrasound imaging probe. Volumetric photoacoustic images were acquired from ex vivo normal term and TTTS‐treated placentas. It was shown that superficial and subsurface branching blood vessels could be visualized to depths of approximately 7 mm, and that ablated tissue yielded negative image contrast. This study demonstrated the strong potential of PA imaging to guide minimally invasive fetal therapies. [Image: see text

Lessons learned from pre-clinical testing of xenogeneic decellularized esophagi in a rabbit model

Summary Decellularization of esophagi from several species for tissue engineering is well described, but successful implantation in animal models of esophageal replacement has been challenging. The purpose of this study was to assess feasibility and applicability of esophageal replacement using decellularized porcine esophageal scaffolds in a new pre-clinical model. Following surgical replacement in rabbits with a vascularizing muscle flap, we observed successful anastomoses of decellularized scaffolds, cues of early neovascularization, and prevention of luminal collapse by the use of biodegradable stents. However, despite the success of the surgical procedure, the long-term survival was limited by the fragility of the animal model. Our results indicate that transplantation of a decellularized porcine scaffold is possible and vascular flaps may be useful to provide a vascular supply, but long-term outcomes require further pre-clinical testing in a different large animal model