Forensic postmortem computed tomography in suspected unnatural adult deaths

Automatic personal identification using a single CT image

OBJECTIVES

Computer vision (CV) mimics human vision, enabling computers to automatically compare radiological images from recent examinations with a large image database for unique identification, crucial in emergency scenarios involving unknown patients or deceased individuals. This study aims to extend a CV-based personal identification method from orthopantomograms (OPGs) to computed tomography (CT) examinations using single CT slices.

METHODS

The study analyzed 819 cranial computed tomography (CCT) examinations from 722 individuals, focusing on single CT slices from six anatomical regions to explore their potential for CV-based personal identification in 69 procedures. CV automatically identifies and describes interesting features in images, which can be recognized in a reference image and then designated as matching points. In this study, the number of matching points was used as an indicator for identification.

RESULTS

Across six different regions, identification rates ranged from 41/69 (59%) to 69/69 (100%) across over 700 possible identities. Comparison of images from the same individual achieved higher matching points, averaging 6.32 ± 0.52% (100% represents the maximum possible matching points), while images of different individuals averaged 0.94 ± 0.15%. Reliable matching points are found in the teeth, maxilla, cervical spine, skull bones, and paranasal sinuses, with the maxillary sinuses and ethmoidal cells being particularly suitable for identification due to their abundant matching points.

CONCLUSION

Unambiguous identification of individuals based on a single CT slice is achievable, with maxillary sinus CT slices showing the highest identification rates. However, metal artifacts, especially from dental prosthetics, and various head positions can hinder identification.

CLINICAL RELEVANCE STATEMENT

Radiology possesses a multitude of reference images for a CV database, facilitating automated CV-based personal identification in emergency examinations or cases involving unknown deceased individuals. This enhances patient care and communication with relatives by granting access to medical history.

KEY POINTS

Unknown individuals in radiology or forensics pose challenges, addressed through automatic CV-based identification methods. A single CT slice highlighting the maxillary sinuses is particularly effective for personal identification. Radiology plays a pivotal role in automated personal identification by leveraging its extensive image database.

The current state of forensic imaging - post mortem imaging

Over the last few decades, forensic imaging has become an essential part of current forensic practice. The aim of this 4-part review is to provide a comprehensive overview of forensic imaging over the first 25 years of this century. After a brief historic review, this first part details the advantages and limitations of post-mortem imaging for the indications most frequently encountered in daily practice.

Enhanced autopsy triage (EA-Triage) in drug-related deaths: integrating quick toxicological analysis and postmortem computed tomography

The objective was to assess the diagnostic accuracy of an enhanced autopsy triage (EA-Triage) setup consisting of postmortem computed tomography (PMCT), simulated quick toxicological analysis (sQTA), external examination, and case information in determining cause of death (COD) in persons with past or current use of illegal drugs (drug-related deaths). Information on drug-related deaths selected for medico-legal autopsy in 2020-2021 at the Department of Forensic Medicine, Aarhus University, Denmark, was analyzed retrospectively. The included cases underwent conventional autopsy, PMCT, and systematic toxicological analysis. A board-certified forensic pathologist, who was blinded to the internal examination and COD from the medico-legal autopsy, determined COD based on the EA-Triage setup. 154 cases with a median age of 40.6 years (range 17-70 years, 82% males) were included. The COD determined by medico-legal autopsy and that determined by EA-Triage matched in 113 cases (73%), including those with an unknown COD. EA-Triage and medico-legal autopsy determined unknown COD in 45 (29%) and 5 cases (3%), respectively. Excluding cases with an unknown COD, EA-Triage predicted COD in 109 cases (71%); of those, 72 (66%) had no unexplained case circumstances or suspicion of a criminal act. In these 72 cases, the CODs determined by EA-Triage and medico-legal autopsy matched in 71 cases (99%), and the sensitivity and specificity for detecting lethal intoxication were 100% and 90%, respectively. EA-Triage showed strong diagnostic accuracy for determining COD in drug-related deaths. This method may be suitable for enhancing preautopsy triage and guiding police investigations at an early stage.

Accelerating computer vision-based human identification through the integration of deep learning-based age estimation from 2 to 89 years

Computer Vision (CV)-based human identification using orthopantomograms (OPGs) has the potential to identify unknown deceased individuals by comparing postmortem OPGs with a comprehensive antemortem CV database. However, the growing size of the CV database leads to longer processing times. This study aims to develop a standardized and reliable Convolutional Neural Network (CNN) for age estimation using OPGs and integrate it into the CV-based human identification process. The CNN was trained on 50,000 OPGs, each labeled with ages ranging from 2 to 89 years. Testing included three postmortem OPGs, 10,779 antemortem OPGs, and an additional set of 70 OPGs within the context of CV-based human identification. Integrating the CNN for age estimation into CV-based human identification process resulted in a substantial reduction of up to 96% in processing time for a CV database containing 105,251 entries. Age estimation accuracy varied between postmortem and antemortem OPGs, with a mean absolute error (MAE) of 2.76 ± 2.67 years and 3.26 ± 3.06 years across all ages, as well as 3.69 ± 3.14 years for an additional 70 OPGs. In conclusion, the incorporation of a CNN for age estimation in the CV-based human identification process significantly reduces processing time while delivering reliable results.

Hidden lesions: a case of burnt remains

One of the many challenging cases that forensic pathologists, anthropologists, and forensic imaging experts have to face are burnt human remains. Perpetrators frequently attempt to hide/destroy evidence and make the body unidentifiable by exposing it to fire. We present a case of a partially burnt body found in an apartment after an explosion. First, multidetector computed tomography (MDCT) images and the following autopsy revealed several lesions on the cranium. Forensic anthropologists were involved in order to specify the aetiology of the lesions observed on the cranium. Through an interdisciplinary approach bringing together MDCT scans, 3D surface scans, and anthropological analysis, it was possible to answer the questions raised during the autopsy. Analyses demonstrated that there were signs of blunt force trauma on the cranium vault that the perpetrator likely attempted to hide by exposing the body to fire. This case demonstrates the importance of close collaboration between forensic anthropologists, imaging experts, and forensic pathologists. This multidisciplinary approach allows for a better, more complete reconstitution of forensic cases.

Key points

The analyses of burnt human remains are one of the many challenging tasks that forensic pathologists and anthropologists have to face.We present an occurrence of a partially burnt body after an explosion and forensic anthropologists were asked whether the nature of the lesions observed on the cranium could be further specified.Anthropological analyses of the skull were consistent with the radiological and autopsy report. It was possible to reconstruct the various lesions on the dry bone.The case demonstrates the importance of an interdisciplinary approach and the close collaboration between forensic anthropologists, imaging experts, and forensic pathologists.

Homicides Disguised as Fire Deaths

Background

When conducting a forensic examination of burnt bodies, it is important to determine whether the victim was exposed to fire while alive or after death. The differential diagnosis between antemortem and postmortem burning is difficult and often cannot be made based on information obtained solely from the autopsy. The aim of the study is to review current literature on this topic and present clinical cases that illustrate how challenging the determination of vitality during the fire and manner of death can be.

Materials and methods

We present four cases of burnt homicide victims, illustrating the complexity of forensic determination of the cause of death in the fire and the importance of differential diagnosis of antemortem and postmortem exposure to flames.

Results

In the forensic assessment autopsy is a fundamental to determine the cause of death. When death is related to fire, particular findings during autopsy can help to suspect that the victim was alive. One of the main antemortem signs is the deposition of soot in the respiratory tract. Another important test is the toxicological analysis, which determines the level of carboxyhaemoglobin in the blood: a concentration of more than 50% indicates that the person died in the fire.

Conclusions

Forensic examination of burnt bodies requires a comprehensive and detailed assessment of all available data. The autopsy, together with additional diagnostic forensic methods, including histological examination, toxicological analysis and postmortem computed tomography, allows the exact cause of death to be determined.

Comparison of findings identified at traditional invasive autopsy and postmortem computed tomography in suicidal hangings

Cases of suicidal hanging are a common death referred for medico-legal autopsy throughout the world. Although some advocate using postmortem computed tomography (PMCT) without traditional invasive autopsy (TIA) to investigate such deaths, others reject this approach. There is currently limited evidence to guide practice. In this context, the TIA reports and PMCT images of 50 cases of suspected suicidal hanging during an 11-month period were reviewed. The reviewers were blinded to the findings of the other modality. A Cohen’s Kappa coefficient (K) was calculated to assess agreement between TIA and PMCT across a range of pertinent findings. This analysis demonstrated perfect agreement for identification of a ligature (K = 1.00) and a strong level of agreement for identification of a ligature suspension point (K = 0.832) but only a minimal level of agreement for overall ligature mark (K = 0.223). PMCT demonstrated a weak level of agreement for fractures of hyoid bone (K = 0.555) and thyroid cartilage (K = 0.538). Three probable fractures not identified at TIA were identified on PMCT. TIA was shown to be superior in the identification of intramuscular and laryngeal fracture–related haemorrhage/bruising whereas PMCT was superior to TIA in identifying body gas deposition. There was overall good correlation between the natural disease and trauma identified elsewhere in the body during the TIA and PMCT. The study demonstrates that PMCT can assist the investigation of suspected suicidal hangings. However, the accuracy of many findings is limited, and if it is used as an alternative to the TIA, potentially pertinent findings, such as fractures of the laryngeal cartilages, could be missed.

Sensitivity and specificity of post-mortem computed tomography in skull fracture detection-a systematic review and meta-analysis

Post-mortem computed tomography (PMCT) has been increasingly used as routine examination in forensic pathology. No recent review of the growing number of papers on the ability of PMCT to detect skull fracture exists, and original papers report sensitivities from 0.85 to 1.00. This systematic review (PROSPERO: CRD42021233264) aims to provide a meta-analysis of sensitivity and specificity of PMCT in skull fracture detection. We searched PubMed, MEDLINE and Embase for papers published between January 2000 and August 2021 reporting raw numbers, sensitivity and specificity or Abbreviated Injury Score for PMCT compared to autopsy. Papers without both PMCT and autopsy, no separate reporting of the neuro-cranium, exclusively on children, sharp trauma, gunshot or natural death as well as case reports and reviews were excluded. Two authors independently performed inclusion, bias assessment and data extraction. QUADAS-2 was used for bias assessment and a random effects models used for meta-analysis. From 4.284 hits, 18 studies were eligible and 13 included in the meta-analysis for a total of 1538 cases. All deceased were scanned on multi-slice scanners with comparable parameters. Images were evaluated by radiologists or pathologists. Intra- and inter-observer analyses were rarely reported. In summary, sensitivity of PMCT for detection of fractures in the skull base was 0.87 [0.80; 0.92] with specificity 0.96 [0.90; 0.98], and sensitivity for the vault was 0.89 [0.80; 0.94] with specificity 0.96 [0.91; 0.98]. The mixed samples are a limitation of the review.

Sudden Death in Adults: A Practical Flow Chart for Pathologist Guidance

The medico-legal term "sudden death (SD)" refers to those deaths that are not preceded by significant symptoms. SD in apparently healthy individuals (newborn through to adults) represents a challenge for medical examiners, law enforcement officers, and society as a whole. This review aims to introduce a useful flowchart that should be applied in all cases of SD. Particularly, this flowchart mixes the data obtained through an up-to-date literature review and a revision of the latest version of guidelines for autopsy investigation of sudden cardiac death (SCD) in order to support medico-legal investigation. In light of this review, following the suggested flowchart step-by-step, the forensic pathologist will be able to apply all the indications of the scientific community to real cases. Moreover, it will be possible to answer all questions relative to SD, such as: death may be attributable to cardiac disease or to other causes, the nature of the cardiac disease (defining whether the mechanism was arrhythmic or mechanical), whether the condition causing SD may be inherited (with subsequent genetic counseling), the assumption of toxic or illicit drugs, traumas, and other unnatural causes.