The artefacts of death: CT post-mortem findings

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.

Postmortem computed tomography of barium peritonitis due to descending colon perforation

We describe herein the findings from postmortem computed tomography (PMCT) of barium peritonitis due to descending colon perforation. The patient was a woman in her 60s who underwent upper gastrointestinal series with barium swallow for the purpose of physical examination. The patient developed abdominal pain the next day and visited a clinic, but was sent home for later follow-up. She was found dead at home 8 days after upper gastrointestinal series. Based on the corpse phenomena and police investigations of the scene of death, the patient was estimated to have died 6 days after the upper gastrointestinal series. PMCT revealed free gas within the peritoneal cavity. Barium and fat stranding were also observed around a diverticulum in the descending colon. A large amount of residual barium was seen in the ascending colon and was considered to represent antemortem constipation and delayed barium excretion. No gas was detected in the abdominal wall, cardiac chambers or hepatic vasculature. The pancreas and adrenal glands had a normal appearance. We diagnosed barium peritonitis due to descending colon perforation as the cause of death. Diverticular perforation was suspected because barium retention and fat stranding were particularly noticeable around the descending colon diverticulum. In conclusion, we have presented a rare case of postmortem diagnosis of barium peritonitis. In PMCT interpretation, distinguishing between ante- and postmortem intestinal perforations is important.

Comparison of fatal traumatic medico-legal cases with postmortem computed tomography and autopsy: A pilot study in Taiwan

In order to determine the performance of postmortem computed tomography (PMCT) in identifying traumatic-relevant macroscopic findings in medico-legal cases, this retrospective observational pilot study involving nine trauma casualties who had received PMCT prior to autopsy. The comparison of these findings in six anatomical regions as dictated in Injury Severity Score (ISS) were performed. 104 traumatic-relevant findings were identified with achievement of 51% congruent findings. PMCT and autopsy had additionally found 22 and 29 findings respectively. PMCT had highest sensitivity for extremity injury (81.82%), followed by chest (73.91%), head, neck and face (71.43%), and abdomino-pelvic area (50%). It had excellent detection rate in abnormal air collection, fracture, foreign body localization, internal ballistic and intracranial pathology. However, the solid organ and vascular injuries as well as integumentary lesions were the major drawback. In conclusion, incorporation of PMCT to autopsy in medico-legal investigation helps to preserve the most abundant traumatic-relevant injuries compared to either modality.

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.

Automated lung vessel segmentation reveals blood vessel volume redistribution in viral pneumonia

PURPOSE

It is known from histology studies that lung vessels are affected in viral pneumonia. However, their diagnostic potential as a chest CT imaging parameter has only rarely been exploited. The purpose of this study is to develop a robust method for automated lung vessel segmentation and morphology analysis and apply it to a large chest CT dataset.

METHODS

In total, 509 non-enhanced chest CTs (NECTs) and 563 CT pulmonary angiograms (CTPAs) were included. Sub-groups were patients with healthy lungs (group_NORM, n = 634) and those RT-PCR-positive for Influenza A/B (group_INF, n = 159) and SARS-CoV-2 (group_COV, n = 279). A lung vessel segmentation algorithm (LVSA) based on traditional image processing was developed, validated with a point-of-interest approach, and applied to a large clinical dataset. Total blood vessel volume in lung (TBV) and the blood vessel volume percentage (BV%) of three blood vessel size types were calculated and compared between groups: small (BV5%, cross-sectional area < 5 mm²), medium (BV5-10%, 5-10 mm²) and large (BV10%, >10 mm²).

RESULTS

Sensitivity of the LVSA was 84.6% (95 %CI: 73.9-95.3) for NECTs and 92.8% (95 %CI: 90.8-94.7) for CTPAs. In viral pneumonia, besides an increased TBV, the main finding was a significantly decreased BV5% in group_COV (n = 14%) and group_INF (n = 15%) compared to group_NORM (n = 18%) [p < 0.001]. At the same time, BV10% was increased (group_COV n = 15% and group_INF n = 14% vs. group_NORM n = 11%; p < 0.001).

CONCLUSION

In COVID-19 and Influenza, the blood vessel volume is redistributed from small to large vessels in the lung. Automated LSVA allows researchers and clinicians to derive imaging parameters for large amounts of CTs. This can enhance the understanding of vascular changes, particularly in infectious lung diseases.

Postmortem Interrogation of Cardiac Implantable Electronic Devices: A 15-Year Experience

OBJECTIVES

This study sought to define the feasibility and utility of postmortem cardiac implantable electronic device (CIED) interrogation.

BACKGROUND

The diagnostic yield of routine postmortem interrogation of CIEDs including pacemakers, defibrillators, and implantable loop recorders has not been established.

METHODS

The study reviewed all CIED interrogations in deceased individuals undergoing medicolegal investigation of sudden or unexplained death by the Victorian Institute of Forensic Medicine between 2005 and 2020.

RESULTS

A total of 260 patients (68.8% male, median age 72.8 years [interquartile range: 62.7-82.2 years]) underwent CIED interrogation (202 pacemakers, 56 defibrillators, and 2 loop recorders) for investigation of sudden (n = 162) or unexplained (n = 98) death. CIEDs were implanted for median of 2.0 years (interquartile range: 0.7-5.0 years), with 19 devices at elective replacement indicator and 5 at end of life. Interrogation was successful in 256 (98.5%) cases. Potential CIED malfunction was identified in 20 (7.7%) cases, including untreated ventricular arrhythmias (n = 13) and lead failures (n = 3, 2 resulting in untreated ventricular arrhythmia). Interrogation directly informed cause of death in 131 (50.4%) cases. A total of 72 (27.7%) patients had abnormalities recorded in 30 days preceding death: nonsustained ventricular tachycardia (n = 26), rapid atrial fibrillation (n = 17), elective replacement indicator or end-of-life status (n = 22), intrathoracic impedance alarms (n = 3), lead issues (n = 3), or therapy delivered (n = 1). In 6 cases in which the patient was found deceased after a prolonged period, interrogation determined time of death. In 1 case, CIED interrogation was the primary means of patient identification.

CONCLUSIONS

Postmortem CIED interrogation frequently contributes important information regarding critical device malfunction, premortem abnormalities, mechanism, and time of death or patient identity. Device interrogation should be considered for select patients with CIEDs undergoing autopsy.

Strengths and Weaknesses of Non-enhanced and Contrast-enhanced Cadaver Computed Tomography Scans in the Teaching of Gross Anatomy in an Integrated Curriculum

Cadaver-specific postmortem computed tomography (PMCT) has become an integral part in anatomy teaching at several universities. Recently, the feasibility of contrast-enhanced (CE)-PMCT has been demonstrated. The purpose of this study was to identify particular strengths and weaknesses of both non-enhanced and contrast-enhanced PMCT compared to conventional cadaver dissection. First, the students' perception of the learning effectiveness of the three different modalities have been assessed using a 34-item survey (five-point Likert scale) covering all anatomy course modules. Results were compared using the nonparametric Friedman Test. Second, the most frequent artifacts in cadaver CT scans, were systematically analyzed in 122 PMCT and 31 CE-PMCT data sets to quantify method-related limitations and characteristics. Perfusion quality was assessed in 57 vascular segments (38 arterial and 19 venous). The survey was answered by n = 257/320 (80.3%) students. Increased learning benefits of PMCT/ CE-PMCT compared to cadaver dissection were found in osteology (2/3 categories, P < 0.001), head and neck (2/5 categories, P < 0.01), and brain anatomy (3/3 categories, P < 0.01). Contrast-enhanced-PMCT was perceived particularly useful in learning vascular anatomy (10/10 categories, P < 0.01). Cadaver dissection received significantly higher scores compared to PMCT and CE-PMCT in all categories of the abdomen and thorax (7/7 categories, P < 0.001), as well as the majority of muscular anatomy (5/6 categories, P < 0.001). Frequent postmortem artifacts (total n = 28, native-phase n = 21, contrast injection-related n = 7) were identified and assessed. The results of this work contribute to the understanding of the value of integrating cadaver-specific PMCT in anatomy teaching.

Postmortem computed tomography differentiation between intraperitoneal decomposition gas and pneumoperitoneum

PURPOSE

The aim of this study is to investigate the ability of postmortem computed tomography (PMCT) to distinguish intraperitoneal decomposition gas from pneumoperitoneum due to intestinal perforation.

METHODS

This retrospective study investigated the factors affecting intraperitoneal gas in two groups of 14 decedents as detected by postmortem CT performed in the Department of Legal Medicine of Hamburg University. The first group died with a cause of death associated with intestinal perforation, and the second group with other different natural causes of death. These factors include postmortem interval, gas volume, gas distribution, radiology alteration index (RAI), and pneumoperitoneum-associated pathology.

RESULTS

The findings of this study showed the appearance of specific gas distribution patterns and a significant increase in gas volumes in the cases of intestinal perforation. Moreover, postmortem interval and the pneumoperitoneum-associated pathology could help distinguish postmortem-generated gas from pneumoperitoneum.

CONCLUSION

Based on the findings of this study, we propose that these findings can improve the proper detection of intestinal perforation cases in the future.

Unenhanced PMCT in the diagnosis of fatal traumatic brain injury in a charred body

Traffic incidents are one of the most frequent causes of death in young adults worldwide. Depending on the location of the incident, the velocity of the vehicle(s), the weather condition, traffic incidents are often complicated making the investigation of the circumstances difficult. Here we report a case of an incinerated body involved in a vehicle incident. Differential diagnosis included natural cause of death during driving, fatal traumatic injuries, death due to fire and positional asphyxia. The body was submitted to PMCT prior to autopsy as part of a research protocol (N. 1388/2016) at the Department of Medical Imaging of the University Hospital of Heraklion in Crete, Greece. Unenhanced PMCT revealed craniofacial fractures, a thin film of subdural haemorrhage and an epidural fluid collection. The findings were interpreted as consistent with an impact to the face, causing craniofacial fractures mainly on the right side, and an acute subdural hematoma. Autopsy findings corroborated the diagnosis. The epidural hematoma was deemed to be post-mortem heat-induced. This case is an excellent example of the diagnostic value of PMCT in the medicolegal investigation of death.

Findings from machine learning in clinical medical imaging applications - Lessons for translation to the forensic setting

Machine learning (ML) techniques are increasingly being used in clinical medical imaging to automate distinct processing tasks. In post-mortem forensic radiology, the use of these algorithms presents significant challenges due to variability in organ position, structural changes from decomposition, inconsistent body placement in the scanner, and the presence of foreign bodies. Existing ML approaches in clinical imaging can likely be transferred to the forensic setting with careful consideration to account for the increased variability and temporal factors that affect the data used to train these algorithms. Additional steps are required to deal with these issues, by incorporating the possible variability into the training data through data augmentation, or by using atlases as a pre-processing step to account for death-related factors. A key application of ML would be then to highlight anatomical and gross pathological features of interest, or present information to help optimally determine the cause of death. In this review, we highlight results and limitations of applications in clinical medical imaging that use ML to determine key implications for their application in the forensic setting.

Vena caval filters for the prevention of pulmonary embolism

BACKGROUND

Pulmonary emboli (PE), or blood clots in the lungs,can be potentially fatal. Anticoagulation is the first line therapy to prevent PE. In some instances anticoagulation fails to prevent more emboli, or cannot be given because the person has a high risk of bleeding. Inferior vena caval filters (VCFs) are metal alloy devices that mechanically trap fragmented emboli from the deep leg veins en route to the pulmonary circulation. Retrievable filters are designed to be introduced and removed percutaneously. Although their deployment seems of theoretical benefit, their clinical efficacy and adverse event profile is unclear. This is the third update of a Cochrane Review first published in 2007.

OBJECTIVES

To assess the evidence for the effectiveness and safety of vena caval filters (VCFs) in preventing pulmonary embolism (PE).

SEARCH METHODS

For this review update, the Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (last searched 10 September 2019) and the Cochrane Register of Controlled Trials (CENTRAL) (2019, Issue 8) via the Cochrane Register of Studies Online. The CIS also searched MEDLINE Ovid, EMBASE Ovid, CINAHL, and AMED (1 January 2017 to 10 September 2019) and trials registries to 10 September 2019.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that examined the efficacy of VCFs in preventing PE.

DATA COLLECTION AND ANALYSIS

For this update, studies were assessed and data extracted independently. We assessed study quality with Cochrane's 'Risk of bias' tool and used the GRADE approach to assess the overall certainty of the evidence. The outcomes of interest were PE, mortality, lower limb venous thrombosis, filter-related complications and major bleeding.

MAIN RESULTS

We identified four new studies for this update, bringing the total to six included studies involving 1388 participants. The six studies were clinically heterogeneous and we were unable to carry out meta-analysis. Only two studies were considered to be both applicable in current clinical settings and of good methodological quality. One was a randomised open-label trial studying the effect of a retrievable inferior vena caval filter plus anticoagulation versus anticoagulation alone on risk of recurrent pulmonary embolism (PE) in 399 participants over three months. There was no evidence of a difference in the rates of PE, death, lower extremity deep vein thrombosis (DVT), or bleeding at three and six months after the intervention (moderate-certainty evidence). A filter was inserted in 193 people, but could only be successfully retrieved from 153. Minor filter complications were noted at six months. The second clinically relevant study was a randomised open-label trial of 240 participants who had sustained multiple traumatic injuries, allocated to a filter or no filter, three days after injury, in conjunction with anticoagulation and intermittent pneumatic compression. Prophylactic anticoagulation was initiated in both groups when it was thought safe to do so. There was no evidence of a difference in symptomatic PE, death, or lower limb venous thrombosis rates (moderate-certainty evidence). The only major filter complication was that one person required surgical removal of the filter. We are unable to draw any conclusions from the remaining four included studies. One study showed an increased incidence of long-term lower extremity DVT at eight years. Three studies are no longer clinically applicable because they utilised permanent filters which are seldom used now, or they did not use routine prophylactic anticoagulation which is current standard practice. The fourth study compared two filter types and was terminated prematurely as one filter group had a higher rate of thrombosis compared to the other filter type.

AUTHORS' CONCLUSIONS

Two of the six identified studies were relevant for current clinical settings. One showed no evidence of a benefit of retrievable filters in acute PE for the outcomes of PE, death, DVT and bleeding during the initial three months in people who can receive anticoagulation (moderate-certainty evidence). The other study did not show any benefit for prophylactic filter insertion in people who sustained multiple traumatic injuries, with respect to symptomatic PE, mortality, or lower extremity venous thrombosis (moderate-certainty evidence). We can draw no firm conclusions regarding filter efficacy in the prevention of PE from the remaining four RCTs identified in this review. Further trials are needed to assess vena caval filter effectiveness and safety, and clinical differences between various filter types.

Postmortem Computed Tomography in Firearm Homicides: A Retrospective Case Series

Postmortem computed tomography (PMCT) is integrated into the evaluation of decedents in several American medical examiner offices and medicolegal death investigative centers in many other countries. We retrospectively investigated the value of PMCT in a series of firearm homicide cases from a statewide centralized medical examiner’s office that occurred during 2016. Autopsies were performed or supervised by board‐certified forensic pathologists who reviewed the PMCT scans prior to autopsy. PMCT scans were re‐evaluated by a forensic radiologist blinded to the autopsy findings and scored by body region (head–neck, thoracoabdominal, and extremities). Injury discrepancies were scored using a modified Goldman classification and analyzed with McNemar’s test. We included 60 males and 20 females (median age 31 years, range 3–73). Based on PMCT, 56 (79.1%) cases had injuries relevant to the cause of death in a single body region (24 head–neck region, 32 thoracoabdominal region). Out of these 56 cases, 9 had a missed major diagnosis by PMCT outside that region, including 6 extremity injuries visible during standard external examination. Yet all had evident lethal firearm injury. We showed that PMCT identifies major firearm injuries in homicide victims and excludes injuries related to the cause of death in other regions when a single body region is injured. Although PMCT has a known limited sensitivity for soft tissue and vascular pathology, it can be combined with external examination to potentially reduce or focus dissections in some of these cases depending on the circumstances and medicolegal needs.

Post-mortem MRI-based volumetry of the hippocampus in forensic cases of decedents with severe mental illness

A decrease in the volume of the hippocampus is associated with severe mental illness, especially schizophrenia, and has been studied extensively in the living using magnetic resonance imaging. Autopsy cohorts also represent a valuable data source for imaging studies. However, post-mortem magnetic resonance imaging (PMMRI) is subject to unique challenges, such as the lower core temperature of scanned subjects and the influence of decomposition processes. This study aimed to determine if results from in vivo studies could be replicated on a post-mortem cohort of decedents who suffered from severe mental illness. We included 96 decedents with either schizophrenia (n = 34), depressive disorder (n = 17), or no known psychiatric diagnosis (n = 45) from April 2015 to January 2017. All cases underwent a T2-weighted cerebral MRI less than 24 h before autopsy. We used a manual segmentation algorithm to define the hippocampus on coronal images and subsequently estimate the volume of the region. The group with schizophrenia had a statistically significant 9.5% decrease in mean hippocampal volume compared with control subjects, while the group with depression trended towards a reduced volume, but this difference was not statistically significant. Thus we were able to replicate previous results from in vivo studies. PMMRI has unique potential for research in that it can be combined with procedures possible only in the research fields of clinical pathology and forensic science, e.g. histopathological sampling.