A computational approach to estimate postmortem interval using postmortem computed tomography of multiple tissues based on animal experiments

The estimation of postmortem interval (PMI) is a complex and challenging problem in forensic medicine. In recent years, many studies have begun to use machine learning methods to estimate PMI. However, research combining postmortem computed tomography (PMCT) with machine learning models for PMI estimation is still in early stages. This study aims to establish a multi-tissue machine learning model for PMI estimation using PMCT data from various tissues. We collected PMCT data of seven tissues, including brain, eyeballs, myocardium, liver, kidneys, erector spinae, and quadriceps femoris from 10 rabbits after death. CT images were taken every 12 h until 192 h after death, and HU values were extracted from the CT images of each tissue as a dataset. Support vector machine, random forest, and K-nearest neighbors were performed to establish PMI estimation models, and after adjusting the parameters of each model, they were used as first-level classification to build a stacking model to further improve the PMI estimation accuracy. The accuracy and generalized area under the receiver operating characteristic curve of the multi-tissue stacking model were able to reach 93% and 0.96, respectively. Results indicated that PMCT detection could be used to obtain postmortem change of different tissue densities, and the stacking model demonstrated strong predictive and generalization abilities. This approach provides new research methods and ideas for the study of PMI estimation.

Characteristics of deceased subjects transported to a postmortem imaging center due to unusual death related to epilepsy

OBJECTIVE

Patients with epilepsy have high risk of experiencing uncommon causes of death. This study aimed to evaluate patients who underwent unusual deaths related to epilepsy and identify factors that may contribute to these deaths and may also include sudden unexpected death in epilepsy (SUDEP).

METHODS

We analyzed 5291 cases in which a postmortem imaging (PMI) study was performed using plane CT, because of an unexplained death. A rapid troponin T assay was performed using peripheral blood samples. Clinical information including the cause of death suspected by the attending physician, body position, place of death, medical history, and antiseizure medications was evaluated.

RESULTS

A total of 132 (2.6%) patients had an obvious history of epilepsy, while 5159 individuals had no history of epilepsy (97.4%). Cerebrovascular disease was the cause of death in 1.6% of patients in the group with epilepsy, and this was significantly lower than that in the non-epilepsy group. However, drowning was significantly higher (9.1% vs. 4.4%). Unspecified cause of death was significantly more frequent in the epilepsy group (78.0% vs. 57.8%). Furthermore, the proportion of patients who demonstrated elevation of troponin T levels without prior cardiac disease was significantly higher in the epilepsy group (37.9% vs. 31.1%). At discovery of death, prone position was dominant (30.3%), with deaths occurring most commonly in the bedroom (49.2%). No antiseizure medication had been prescribed in 12% of cases, while 29.5% of patients were taking multiple antiseizure medications.

SIGNIFICANCE

The prevalence of epilepsy in individuals experiencing unusual death was higher than in the general population. Despite PMI studies, no definitive cause of death was identified in a significant proportion of cases. The high troponin T levels may be explained by long intervals between death and examination or by higher incidence of myocardial damage at the time of death.

PLAIN LANGUAGE SUMMARY

This study investigated unusual deaths in epilepsy patients, analyzing 5291 postmortem imaging cases. The results showed that 132 cases (2.6%) had a clear history of epilepsy. In these cases, only 22% cases were explained after postmortem examination, which is less than in non-epilepsy group (42.2%). Cerebrovascular disease was less common in the epilepsy group, while drowning was more common. Elevated troponin T levels, which suggest possibility of myocardial damage or long intervals between death and examination, were also more frequent in the epilepsy group compared to non-epilepsy group.

Living and post-mortem CT scans in the gross anatomy lab: A study investigating differences in first-year medical students' exam performance and perceptions

Basic competency in radiological imaging is essential for physicians to identify and manage diseases. An optimal place in which to include imaging in the medical curriculum is during anatomy as students can correlate the 3D anatomy from their body donors with the 2D cross-sectional anatomy. The goal of this project was to enhance first-year medical students' knowledge of cross-sectional imaging in the gross anatomy lab and to investigate whether there are benefits to learning cross sectional imaging via scans from body donors versus living individuals. Student participant performance was evaluated on laboratory practical examinations, CT image questions and spatial anatomical knowledge in the thorax and abdomen sections of gross anatomy. Students learned the cross-sectional imaging during dissections where they accessed the images relevant to their study on Pacsbin, a web-based Digital Imaging and Communication in Medicine viewer, via iPads. Results showed no statistically significant differences in practical examination scores, spatial anatomical knowledge, or identification of anatomical structures on CT image questions between participants who learned from images on body donors versus living individuals. In a questionnaire given at the end of the course, participants cited that the CT images improved their anatomical and imaging knowledge and that they felt better prepared to use imaging software and interpret diagnostic imaging results upon entering clerkships. While there were no differences in academic performance between the groups, positive outcomes regarding student perceptions of anatomical and imaging knowledge and preparedness for use of imaging software were identified in this study.

Efficacy of postmortem CT and tissue sampling in establishing the cause of death in clinical practice: a prospective observational study

AIMS

The aim of this study is to evaluate whether agreement with autopsy-determined cause of death (COD) increases by use of postmortem CT (PMCT) or PMCT in combination with postmortem sampling (PMS), when compared with clinical assessment only.

METHODS

This prospective observational study included deceased patients from the intensive care unit and internal medicine wards between October 2013 and August 2017. The primary outcome was percentage agreement on COD between the reference standard (autopsy) and the alternative postmortem examinations (clinical assessment vs PMCT or PMCT+PMS). In addition, the COD of patient groups with and without conventional autopsy were compared with respect to involved organ systems and pathologies.

RESULTS

Of 730 eligible cases, 144 could be included for analysis: 63 underwent PCMT without autopsy and 81 underwent both PMCT and autopsy. Agreement with autopsy-determined COD was significantly higher for both PMCT with PMS (42/57, 74%), and PMCT alone (53/81, 65%) than for clinical assessment (40/81, 51%; p=0.007 and p=0.03, respectively). The difference in agreement between PMCT with PMS and PMCT alone was not significant (p=0.13). The group with autopsy had a significantly higher prevalence of circulatory system involvement and perfusion disorders, and a lower prevalence of pulmonary system involvement.

CONCLUSION

PMCT and PMS confer additional diagnostic value in establishing the COD. Shortcomings in detecting vascular occlusions and perfusion disorders and susceptibility to pulmonary postmortem changes could in future be improved by additional techniques. Both PMCT and PMS are feasible in clinical practice and an alternative when autopsy cannot be performed.

Air bubble artifact: why postmortem brain MRI should always be combined with postmortem CT

Forensic pathology increasingly uses postmortem magnetic resonance imaging (PMMRI), particularly in pediatric cases. It should be noted that each (sudden and unexpected) death of an infant or child should have a forensic approach as well. Current postmortem imaging protocols do not focus adequately on forensic queries. First, it is important to demonstrate or rule out bleeding, especially in the brain. Thus, when incorporating PMMRI, a blood sensitive sequence (T2* and/or susceptibility weighted imaging (SWI)) should always be included. Secondly, as intracranial air might mimic small focal intracerebral hemorrhages, PMMRI should be preceded by postmortem CT (PMCT) since air is easily recognizable on CT. This will be illustrated by a case of a deceased 3-week-old baby. Finally, note that postmortem scans will often be interpreted by clinical radiologists, sometimes with no specific training, which makes this case report relevant for a broader audience.

Validity of postmortem computed tomography for use in forensic odontology identification casework

Forensic Odontology (FO) identification compares antemortem (AM) and postmortem (PM) dental datasets and is widely accepted as a primary identifier. Traditionally, a PM dental examination is undertaken in the same manner as a dental examination conducted for a living patient. Recently, the increased forensic application of computed tomography (CT) offers an alternative source of PM data. While charting from PMCT is widely accepted as less accurate, the impact on reconciliation is unknown. This study aims to determine if reconciliation outcome differs when PM dental data is collected from PMCT, compared with conventional PM examination. PMCT data was reviewed for 21 cases previously completed using conventional PM dental examination. Operators blinded to original identification outcomes charted from CT images before comparing to AM data to form an opinion regarding identity. Opinions formed were compared with original identification outcomes. Differences in PM dental charting between the two methods and the evidentiary value of AM and PM datasets were assessed to determine driving factors of differences in identification outcome. Compared to conventional PM dental examination, PMCT examination resulted in similar or less certain identification outcomes. Discrepancies in outcome were driven by the quality of AM and PM datasets rather than inaccuracies in charting from PMCT. Based on the results of this study, both conventional and PMCT methods of PM dental examination can reach similar identification outcomes. However, operators remained more certain in establishing identity when conducting conventional PM dental examinations especially when AM data was lacking.

Postmortem Computed Tomography Is a Reliable, Reproducible, and Accurate Method in Measuring Body Length

ABSTRACT

Currently, traditional body length measurement at postmortem analysis involves processes, which are susceptible to human error and not reviewable or reproducible in case of data loss. Many facilities are now adopting routine postmortem computed tomography (PMCT) scanning, which provides a permanent and reviewable radiological record of body dimensions. Previous literature has validated the use of PMCT in estimating body and organ weights, but not in body length measurement. This retrospective study aimed to determine whether body length can be accurately and reliably measured when compared with traditional measurements in 50 consecutive adult cases. Our findings revealed that body length measured using PMCT had high intrarater and interrater reliability across different experience levels in raters (Pearson correlation coefficient and interclass correlation: >0.99, P < 0.01). Although body lengths measured using PMCT were significantly shorter (mean, -1.2 cm; 95% confidence interval, -1.75 to -0.65 cm; P < 0.05), it was deemed clinically insignificant and correlated well with those measured at postmortem examination (Pearson correlation coefficient and interclass correlation, >0.97; P < 0.01). While care will need to be taken to ensure the body in the body bag is in reasonable anatomical position for scanning purposes, overall, body length measured uniform PMCT is reliable, reproducible, and accurate.

Distinguishing true from pseudo hematoma in the cervical spinal canal using postmortem computed tomography

Spinal cord injury is difficult to detect directly on postmortem computed tomography (PMCT) and it is usually diagnosed by indirect findings such as a hematoma in the spinal canal. However, we have encountered cases where the hematoma-like high-attenuation area in the cervical spinal canal was visible on PMCT, while no hematoma was observed at autopsy; we called it a "pseudo hematoma in the cervical spinal canal (pseudo-HCSC)." In this retrospective study, we performed statistical analysis to distinguish true from pseudo-HCSC. The cervical spinal canal was dissected in 35 autopsy cases with a hematoma-like high-attenuation area (CT values 60-100 Hounsfield Unit (HU)) in the spinal canal from the first to the fourth cervical vertebrae in axial slices of PMCT images. Of these 22 had a hematoma and 13 did not (pseudo-HCSC). The location and length of the hematoma-like high-attenuation and spinal cord areas were assessed on reconstructed PMCT images, true HCSC cases had longer the posterior hematoma-like area and shorter the spinal cord area in the midline of the spinal canal (P < 0.05). Furthermore, we found that true HCSC cases were more likely to have fractures and gases on PMCT while pseudo-HCSC cases were more likely to have significant facial congestion (P < 0.05). We suggest that pseudo-HCSC on PMCT is related to congestion of the internal vertebral venous plexus. This study raises awareness about the importance of distinguishing true HCSC from pseudo-HCSC in PMCT diagnosis, and it also presents methods for differentiation between these two groups.

The effect of post-mortem computed tomography angiography (PMCTA) on biomarkers of coronary artery disease

Coronary atherosclerosis is due to build-up of plaque within the coronary arteries. Post-mortem computed tomography (PMCT) allows non or minimally invasive visualization of abnormalities prior to an autopsy, however PMCT-angiography (PMCTA) greatly enhances relevant findings, especially in viewing the cardiovascular system which is important in the diagnosis of coronary atherosclerosis. Contrast media used in PMCTA however has been reported to cause distortion of tissue which may interfere with post-mortem investigation outcomes. A cross sectional study to investigate the effect of PMCTA on tissue biomarkers in coronary arteries was performed involving cases brought in dead to the Institute and Accident and Emergency Unit. Sixty-three autopsy cases were included in this study, whereby 18 cases underwent PMCT while 45 cases underwent PMCTA. The subjects subsequently had a conventional autopsy where coronary artery sections were collected for standard histological examination and immunohistochemistry examination for endothelial inflammatory (CD36), prothrombogenic (TPA) and plaque stability (MMP-9) markers. The subjects consisted of 55 males and 8 females with a mean age ±SD of 49 ± 18.11 years. There were no significant differences in the coronary artery endothelial expression of CD36, MMP-9 and TPA between PMCT and PMCTA subjects. PMCTA does not alter CD36, TPA and MMP-9 markers supporting the safe use of PMCTA in post-mortem examinations.

Pericardial Effusion Detection on Post-Mortem Computed Tomography Images Using Convolutional Neural Networks

Pericardial effusion can be a sign of significant underlying diease and, in some cases, may lead to death. Post-mortem computed tomography (PMCT) is a well-established tool to assist death investigation processes in the forensic setting. In practice, the scarcity of well-trained radiologists is a challenge in processing raw whole-body PMCT images for pericardial effusion detection. In this work, we propose a Pericardial Effusion Automatic Detection (PEAD) framework to automatically process raw whole-body PMCT images to filter out the irrelevant images with heart organ absent and focus on pericardial effusion detection. In PEAD, the standard convolutional neural network architectures of VGG and ResNet are carefully modified to fit the specific characteristics of PMCT images. The experimental results prove the effectiveness of the proposed framework and modified models. The modified VGG and ResNet models achieved superior detection accuracy than the standard architecture with reduced processing speed.

Technical note: Interest of focused fields in post-mortem computed tomography using photorealistic images for age at death estimation from the pubic symphysis

INTRODUCTION

The morphological assessment of the pubic symphysis using the Suchey-Brooks method is considered a reliable age at death indicator. Age at death estimation methods can be adapted to the images obtained from post-mortem computed tomography (PMCT). The aim of this study is to evaluate the utility of pubic symphysis photorealistic images obtained through Global illumination rendering (GIR) for age at death estimation from whole-body PMCT and from focused PMCT on the pubic bone.

MATERIALS AND METHODS

We performed virtual age at death estimation using the Suchey Brooks method from both the whole-body field of view (Large Field of View: LFOV) and the pubis-focused field of view (Small and Field of View: SFOV) of 100 PMCT. The 3D photorealistic images were evaluated by three forensic anthropologists and the results were statistically evaluated for accuracy of the two applied PMCT methods and the intra- and inter-observer errors.

RESULTS

When comparing the two acquisitions of PMCT, the accuracy rate reaches 98.5% when using a pubic-focused window (SFOV) compared to 86% with a whole-body window (LFOV). Additionally, the intra- and inter-observer variability has demonstrated that the focused window provides better repeatability and reproducibility.

CONCLUSION

Adding a pubic-focused field of view to standard PMCT and processing it with GIR appears to be an applicable technique that increases the accuracy rate for age at death estimation from the pubic symphysis.

Postmortem computed tomography imaging of negative pressure pulmonary edema induced by rice cakes: A case report

Airway obstruction by foreign bodies or laryngospasms often results in negative pressure pulmonary edema (NPPE). NPPE can develop despite the removal of airway obstruction. This is well-known among clinicians, particularly anesthesiologists, emergency physicians, pediatricians, and radiologists. Computed tomography (CT) features of NPPE include diffuse central ground-glass opacities and thickening of the bronchovascular bundles and bronchial walls. NPPE can also occur after strangulation or smothering with a plastic bag, and is sometimes fatal. Nevertheless, no reports of NPPE are available in forensic journals, and forensic practitioners may not be dedicating the necessary attention to this condition. Recently, the use of postmortem CT as an auxiliary imaging modality for autopsies has increased among forensic institutions in Japan. Understanding the mechanisms and CT findings of NPPE will be useful for forensic practitioners. Herein, we present a case wherein the postmortem CT image revealed NPPE resulting from the obstruction of the airway induced by rice cakes.

Post-mortem Imaging of Brain/Spine Injuries: The Importance of a Comprehensive Forensic Approach

In forensic investigations, the limitations of the traditional purely autoptic approach can be overcome through post-mortem imaging (virtopsy). Virtospy has several applications to the investigation of brain and spinal injuries, whose analysis can be of forensic interest, especially in cases of suspected malpractice. In this scoping review, we briefly describe the main applications of the two most common post-mortem radiological techniques (computed tomography (CT) and magnetic resonance imaging (MRI)) to the forensic investigation of brain and spinal injuries in cases of medical malpractice or traumatic (accidental/homicidal/suicidal) deaths. Although CT represents the traditional approach to post-mortem imaging, MRI is proving to be a valuable tool to investigate brain and spinal injuries and lesions. These post-mortem radiological techniques can also be used to guide the surgeons in simulated surgical procedures on corpses in the context of training programs, thus helping operators to improve technical and non-technical skills and to reduce the risk of avoidable errors.

Knowledge and attitudes of Polish prosecutors and general Polish population in regard to post-mortem computed tomography in 2019

Post-mortem computer tomography (PMCT) is an imaging technique that is gaining popularity both worldwide and in Poland. It provides certain benefits in death investigation that a conventional autopsy is not able to, however, it has significant limitations. As PMCT and post-mortem computed angiography (PMCTA) continue to develop in this country, it is critical to become aware what people know and think about these imaging techniques, especially the prosecutors who officially order such examinations to be performed. In 2019, two concurrent surveys were administered to Polish prosecutors and general Polish population, respectively, regarding their current knowledge and opinions on PMCT. The results were collected both online and on paper, and then subjected to analysis. In total, 92 prosecutors and 227 non-prosecutors responded to the survey. The present authors observed that while prosecutors were more likely to have heard of this examination than the general public, their knowledge was often inadequate or incorrect. Conventional autopsy was still held as the gold standard in death investigation. However, a good popular sentiment towards PMCT was shown, and a desire to learn more about it - not just among prosecutors, but among the general public as well. The present authors' recommendation is that more courses and training should be organised for Polish prosecutors to compensate this knowledge gap.