Imaging in forensic radiology: an illustrated guide for postmortem computed tomography technique and protocols

An autopsy approach to bolus deaths

BACKGROUND

The term "bolus death" or "cafe coronary" refers to a misplaced larynx or laryngeal inlet by foreign bodies, in most cases by unchewed pieces of food such as meat, sausage, or fruit. The pathophysiologic mechanism of death is still debatable - sudden reflex cardiac arrests and asphyxial suffocations are implicated. In particular, children, alcoholics, and persons with brain-related damages belong to this risk group. A defective dentition is also associated with the risk of bolus deaths.

AIM

The aim of the study was to supplement existing literature by evaluating cases of bolus deaths and determining the most likely mechanism of death in a large autopsy sample.

MATERIAL

Among 31,647 autopsies, 59 cases of cafe coronary syndrome were identified and evaluated: 38 male adults and 21 female adults between the ages of 26 and 89 years.

METHODS

A retrospective analysis of autopsies performed in the Institutes of Forensic Medicine in Rostock (1990-2014) and Munich (1990-1999) was conducted. Autopsy findings, circumstances of death, police investigations, preexisting conditions, dentition, and toxicological investigations were recorded. Then, based on the presence or absence of selected findings and surrounding circumstances, conclusions on the mechanism of death were drawn.

RESULTS

In eighty-six percent (86%), boluses of meat and sausage or meat-like chunks were observed. Of the forty-nine victims, 22 (42%) had elevated blood alcohol levels (>0.5‰) with blood alcohol concentration (BAC) levels of >0.73‰ to <3.99‰. Of the nonalcoholized decedents, 63% had neurological disorders and 11% had preexisting cardiac conditions.

CONCLUSIONS

Detecting potential bolus events upon autopsy and the resulting mechanism of nonnatural deaths are of great importance. Therefore, the medical history, resuscitation protocol, and detailed description of the scene of death are essential. Upon autopsy, the type and position as well as size and weight of the bolus and dental status of the victims should be documented in a standardized manner. Additional toxicological investigations are necessary.

Hyperdensity of the Basilar Artery on Postmortem CT: A Potential Indicator for Basilar Artery Thrombosis

Basilar artery thrombosis constitutes 1% of all types of stroke, carries a mortality rate of up to 90%, and is one of the rarer causes of sudden death. It leads to brain stem ischemia and commonly presents with impaired consciousness, cranial nerve palsy, hemiplegia or quadriplegia, and sudden collapse. Clinically, the diagnosis of basilar artery thrombosis is made on clinical symptoms, along with a hyperdense basilar artery in antemortem computed tomography (CT) scan. To our knowledge, whether a hyperdense basilar artery indicates basilar artery thrombosis on postmortem CT scan is not documented in the literature. We present a case report of a 55-year-old man who on postmortem CT scan showed a hyperdense basilar artery and was subsequently confirmed to be a fatal basilar artery thrombosis. We suggest that a hyperdense basilar artery on postmortem CT should prompt the pathologist to consider basilar artery thrombosis.

Postmortem Changes in Animal Carcasses and Estimation of the Postmortem Interval

A thorough understanding of the physical and chemical changes that occur in the body after death is critical for accurate interpretation of gross and microscopic pathology at autopsy. Furthermore, knowledge of the postmortem processes and the factors that affect them will aid in the estimation of the postmortem interval (PMI). The estimation of the PMI is important in many human and animal death investigations. Despite many decades of research, accuracy in estimation of the time of death has not significantly improved, and no single method can be reliably used to accurately estimate the time of death. Great care should be taken when formulating such an estimate, for it is dependent on multiple circumstantial and environmental factors, and the accuracy and precision of the estimate decrease as the PMI increases. The majority of the research in the field has been conducted on human bodies, but many relevant conclusions may be drawn regarding the expected postmortem changes in animals and the estimation of the PMI. The veterinary pathologist must use great caution when attempting to extrapolate data and apply formulas designed for use in humans. Methods reviewed include gross changes, microscopic changes, temperature-based methods, postmortem chemistry, molecular methods, microbial assay, ocular changes, radiography, entomology, and others. Although only several of these methods are currently practical for use in the workup of cases, it is expected that future research will result in improved techniques with enhanced accuracy in the estimation of the PMI, which will benefit both human and veterinary forensic investigations.

A fatal case of electrocution with unique forensic radiological postmortem findings

PURPOSE

Documentation of forensic radiological observations in postmortem imaging of electrical injuries is not common yet and is less prevalent compared to other forms of burn injuries. However, electrical injuries have high morbidity and mortality. The objective of this case report was the visualization and evaluation of unique electrocution-related injuries by postmortem contrast and non-contrast enhanced imaging compared to a forensic autopsy.

METHODS

Forensic imaging included whole-body postmortem computed tomography (PMCT), PMCT-angiography (PMCTA), postmortem magnetic resonance tomography (PMMR), and PMMR-angiography (PMMRA). Initial external inspection and subsequent autopsy were performed.

RESULTS

Imaging results revealed intestinal mucosal pathologies, particularly of the gastric vascular integrity and remarkable rhabdomyolysis of the striated muscles of the extremities. Furthermore, PMCT and PMCTA revealed a hepatic lesion with perihepatic free fluid. The results from external inspection and autopsy correlated to the well-known pathologies of electrocution in the course of a high-voltage incident.

CONCLUSION

Postmortem imaging visualized electrocution-related injuries and aided substantially in the medico-legal investigation. These findings, particularly of the rhabdomyolysis in magnetic resonance tomography, may support the future image interpretation of cases with electrical injuries-in the living and the deceased.

Postmortem CT versus forensic autopsy: frequent discrepancies of tracheobronchial content findings

In their daily forensic casework, the authors experienced discrepancies of tracheobronchial content findings between postmortem computed tomography (PMCT) and autopsy to an extent previously unnoticed in the literature. The goal of this study was to evaluate such discrepancies in routine forensic cases. A total of 327 cases that underwent PMCT prior to routine forensic autopsy were retrospectively evaluated for tracheal and bronchial contents according to PMCT and autopsy findings. Hounsfield unit (HU) values of tracheobronchial contents, causes of death, and presence of pulmonary edema were assessed in mismatching and matching cases. Comparing contents in PMCT and autopsy in each of the separately evaluated compartments of the respiratory tract low positive predictive values were assessed (trachea, 38.2%; main bronchi, 40%; peripheral bronchi, 69.1%) indicating high discrepancy rates. The majority of tracheobronchial contents were viscous stomach contents in matching cases and low radiodensity materials (i.e., HU < 30) in mismatching cases. The majority of causes of death were cardiac related in the matching cases and skull/brain trauma in the mismatching cases. In mismatching cases, frequency of pulmonary edema was significantly higher than in matching cases. It can be concluded that discrepancies in tracheobronchial contents observed between PMCT and routine forensic autopsy occur in a considerable number of cases. Discrepancies may be explained by the runoff of contents via nose and mouth during external examination and the flow back of tracheal and main bronchial contents into the lungs caused by upright movement of the respiratory tract at autopsy.

Postmortem-computed tomography and postmortem-computed tomography-angiography: a focused update

The use of multidetector CT (MDCT) represents a reality routinely used in several forensic institutes, for the numerous advantages that this diagnostic tool can provide; costs are becoming increasingly lower; data acquisition is always faster and once acquired may be revalued at any time. However, there are also some diagnostic limitations, for example, the visualization of the vascular system or a limited soft tissue contrast. In order to overcome these limitations, in recent years, contrast medium has been introduced in postmortem cases, with the development of several techniques of PMCT angiography (PMCTA) and standardized protocols to make them easily reproducible. The aim of this review is to highlight the advantages and pitfalls of PMCT and PMCTA in forensic investigation, taking into consideration the broad spectrum of applications both for natural and unnatural deaths and the numerous methods currently used. Secondly, in the light of the considerable progress in this field and the attempt to develop standardized protocols of PMCTA, the authors aim to evaluate the diagnostic value of PMCTA in comparison both to PMCT and conventional autopsy.

Imaging for homicide investigations

The authors present the opportunities of the application of post-mortem imaging, focusing on post-mortem computed tomography and post-mortem computed tomography angiography in modern forensic investigation of homicide cases. The paper is based on scientific publications related to the subject from ca. the past 10 years, supplemented by the authors' own experiences. The article is illustrated with reconstructions based on the authors' own cases related to homicide due to ballistic/sharp/blunt trauma. As is shown, the results of evaluation of post-mortem computed tomography allow better diagnosis, documentation and visualisation of forensic examinations.

The correlation of epicardial adipose tissue on postmortem CT with coronary artery stenosis as determined by autopsy

The goal of this study was to assess whether epicardial and paracardial adipose tissue volumes, as determined by computed tomography (CT), correlate with coronary artery stenosis as determined by autopsy. The postmortem CT data and autopsy findings of 116 adult human decedents were retrospectively compared. Subjects were classified into three groups according to their degree of coronary artery stenosis: ≥50, <50%, and no stenosis. Epicardial and paracardial adipose tissue volumes were calculated based on manual segmentation after threshold based masking. In addition, epicardial adipose tissue thickness was measured using a caliper. All three parameters (thickness of epicardial fat and volumes of both epicardial and paracardial fat) were compared among the three groups and correlated with the degree of coronary artery stenosis. The group with no coronary artery stenosis showed the lowest mean values of epicardial adipose tissue volume, while the coronary artery stenosis ≥50 % group showed the highest volume. All measured variables (thickness of epicardial fat and volumes of both epicardial and paracardial fat) correlated significantly with the grade of coronary artery stenosis, even after controlling for BMI, however, epicardial adipose tissue volume exhibited the strongest correlation. This study reveals that there is an association between the degree of coronary artery stenosis and the amount of epicardial fat tissue: The larger the volume of epicardial fat, the higher the degree of coronary artery stenosis.

Smaller but denser: postmortem changes alter the CT characteristics of subdural hematomas

PURPOSE

The aim of this study was to investigate if (1) the volume of subdural hematomas (SDH), midline shift, and CT density of subdural hematomas are altered by postmortem changes and (2) if these changes are dependent on the postmortem interval (PMI).

MATERIALS AND METHODS

Ante mortem computed tomography (AMCT) of the head was compared to corresponding postmortem CT (PMCT) in 19 adults with SDH. SDH volume, midline shift, and hematoma density were measured on both AMCT and PMCT and their differences assessed using Wilcoxon-Signed Rank Test. Spearman's Rho Test was used to assess significant correlations between the PMI and the alterations of SDH volume, midline shift, and hematoma density.

RESULTS

Mean time between last AMCT and PMCT was 109 h, mean PMI was 35 h. On PMCT mean midline displacement was decreased by 57% (p < 0.001); mean SDH volume was decreased by 38% (p < 0.001); and mean hematoma density was increased by 18% (p < 0.001) in comparison to AMCT. There was no correlation between the PMI and the normalization of the midline shift (p = 0.706), the reduction of SDH volume (p = 0.366), or the increase of hematoma density (p = 0.140).

CONCLUSIONS

This study reveals that normal postmortem changes significantly affect the extent and imaging characteristics of subdural hematoma and may therefore affect the interpretation of these findings on PMCT. Radiologists and forensic pathologists who use PMCT must be aware of these phenomena in order to correctly interpret PMCT findings in cases of subdural hemorrhages.

Postmortem angiography in computed tomography and magnetic resonance imaging in a case of fatal hemorrhage due to an arterio-venous malformation in the brain

Autopsy is the traditional gold standard for determining the cause and manner of death in a forensic death investigation. However, postmortem imaging plays an ever-growing role in preliminary examination, even replacing conventional autopsy in some cases. This case report presents a case of massive intra-axial brain hemorrhage due to an arterio-venous malformation. The cause and manner of death were exclusively determined by postmortem radiology. Based on radiological findings, the autopsy was considered redundant and cancelled by the public prosecutor.