Pros and cons of post-mortem CT imaging on aspiration diagnosis

doi:10.1016/j.legalmed.2010.09.006

Legal Medicine

Volume 13, Issue 1, January 2011, Pages 16-21

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Abstract

Recently, the field of forensics has experienced a rapid increase in the use of modern cross-sectional imaging in forensic investigations. We examined the value of post-mortem computed tomography (CT) imaging relative to autopsy for distinguishing aspiration into the lungs from airways, from lung alterations due to other causes, and for identifying the aspirated material. We selected 54 bodies submitted to whole-body CT scanning prior to autopsy. All cases had autopsy findings of blood (31 cases), fresh water (12 cases), or gastric content (11 cases) aspiration. The radiological images were retrospectively analyzed for airway and lung aspiration. In all cases, CT imaging detected pulmonary abnormalities suggestive of aspiration. Nevertheless, analysis of the CT images alone was not able to identify the aspirated material or to distinguish pulmonary findings of aspiration from lung changes due to other causes, except for a few cases of hemo-aspiration. However, due to its ability to visualize the entire parenchyma, CT imaging was superior to autopsy in providing additional data about the distribution and severity of the aspiration as well as in detecting small abnormalities. Post-mortem CT imaging should be considered as a superior tool for forensic investigations of aspiration due to its ability to document diagnostic conclusions and to guide the forensic pathologist during lung tissue examination.

Introduction

Aspiration is defined as the inhalation of endogenous or foreign material into the deep respiratory tracts. The detection of signs of aspiration at autopsy is a common task with a high degree of forensic relevance due to the information provided about whether an injury occurred pre-mortem and/or it was the primary, or contributing cause of death.

Traditionally, the diagnosis of aspiration is based on the macroscopic inspection of the airways and lungs during autopsy [1]. However, microscopic findings of deep aspiration in alveoli and bronchioles should always accompany this diagnosis, though the histological appearance of vital aspiration foci varies depending on survival time, the size of the foci, and the nature of the aspirated material [1], [2], [3], [4], [5]. A diagnosis of aspiration as the primary or contributing cause of death can be reached only after considering the extent and quality of the histological findings.

Many authors have attempted to identify clinical CT findings of aspiration [6], [7], [8], [9], [10], [11], [12], [13] for therapy and definition of prognosis. On the contrary, few studies have focused on the appearance of aspiration in post-mortem CT images [14], [15], [16], [17]; most of them concern imaging findings of water aspiration in cases of death by drowning [15], [16]. Although Thali et al. reported post-mortem CT findings of aspiration of more than one material in the pilot paper of the Virtopsy® project [14], a comparison between different pulmonary imaging findings in cases of aspiration of diverse materials has never been conducted.

The aim of this retrospective study was to describe the post-mortem CT images of the lungs and airways in cases of aspiration (such as blood, fresh water, and gastric content) and to evaluate them with autopsy findings to identify the nature of aspirated materials and to distinguish them from changes due to other pathological causes.

Section snippets

Study population

The study was approved by the local Ethics Committee. Between January 2005 and December 2008, a total of 359 human corpses underwent multi-detector CT scanning, at the Institute of Forensic Medicine in Bern, prior to autopsy as part of the Virtopsy® project.

We reviewed the final autopsy reports related to 359 cases with the following selection criteria: documentation of blood, fresh water, and/or gastric content aspiration upon macroscopic and/or microscopic examination of airways and pulmonary

Autopsy

The results of autopsy are reported separately for the three groups.

Discussion

This study showed broad concordance between post-mortem CT and autopsy. However, there were some discrepancies in sensitivity and specificity between them, which require explanation.

Differences were noted between CT and autopsy for the assessment of the localization and amount of aspirated materials in the large airways. Two reasons are considered: (1) some cases had minimal or only a small amount of aspirated materials recognizable only by autopsy, and (2) movement of fluids within the airways

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Quantitative analysis of pulmonary structures in PMCT; Stereological comparison of drowning compared to opioid-overdose cases.
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Citation Excerpt :
GGO is defined as an area with increased attenuation with visible bronchial and/or vessel margins [22]. GGO occur due to a change of density in the lung tissue and has been described in several studies on PMCT in drowning as both pathological and non-pathological findings [17, 19, 23–26]. Consolidations are areas with a higher density, compared to GGOs, and without visible bronchial and vessel margins.
The aim of this study, was to introduce stereology as a versatile and robust tool for quantitative image analysis of volume and attenuation characteristics (Hounsfield Units (HU's)), in a blinded control case study investigating lungs of drowning victims compared to a control group on post mortem computed tomography (PMCT) data.
PMCT scans of the lungs from 14 drowned cases and 14 matched opioid-overdose-controls was included. Quantitative CT-analysis was performed using a stereological approach adapted to PMCT data that allowed for precise extraction of volume and HU-values using stereological point-probes assigned manually to individual lung-structures. Qualitative radiological image interpretation performed by a trained radiologist was compared to the quantitative analyses.
No significant difference was found for total lung volume, volumes of consolidations, ground glass opacities, bronchi, and air-filled lung tissue. When comparing drowning cases with opioid overdose cases as controls, the extracted HU-values did not show statistically significant changes in mean attenuation characteristics. No major discrepancies were found between the quantitative analysis and qualitative analysis.
Conventional radiological evaluation of PMCT images rely on the radiologists’ ability to distinguish normal from pathological. Quantitative image analysis offers, to name a few, precise estimations of structure volume and HU-statistics. Although the used 14 matched cases data failed to significantly aid the diagnosis of drowning statistically, we envisage that quantitative PMCT analysis using stereology could become a valuable tool to improve objective forensic radiological interpretation.
Planned complex suicide combining pistol head shot and train suicide and Virtopsy examination
2022, Forensic Imaging
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In the context of the extensive blunt trauma due to the body being run over by the train, the lungs exhibited multiple pneuomatoceles. The lower lobe of the right lung appeared to contain a nodular patchy ground-glass pattern, consistent with aspiration of gastric content and subsequent bronchiolitis [19–21]. Due to the information brought about by the police investigation and medicolegal examination in conjunction, no evidence for homicidal involvement was found.
This case report focuses on the findings in what appeared to be a planned complex pistol head shot and train suicide. The post mortem computed tomography (PMCT) scan in this instance yielded two interesting skull fragments among the many fragments of a highly fragmented body and head. These two fragments, based on initial resolution, appeared to show findings consistent with a firearm shot to the head. Upon reconstruction of higher resolution data, the necessary discrimination of non-gunshot related semi-circular fragment rims and firearm-related beveling matched the macroscopic aspect of the skull fragments. As a first lesson to be learned, a thorough examination of PMCT data in relatively high degrees of fragmentation may have to inspect all bone edges also for relatively subtle changes, possibly indicative of sharp force trauma or gunshot trauma. To that end, individual bone fragments should be placed on the scanner table carefully and with proper spacing, to expose their edges. Only this allows to capture data that avoids edge overlaps or edge collisions and that allows for optimal checking of the edges of all bone fragments for possible semicircular defects in the PMCT data. A second technical lesson to be learned is that particularly in instances of high fragmentation of at least parts of a body, resolution may have to be at least as good as maximally achievable. To that end, availability of the raw data to reconstruct images with maximal image quality rather than using a trade-off between lesser cost and lesser yield may be a key issue. A third lesson to be learned is that findings in relatively highly fragmented bodies as consequence of an apparent form of injury - fire/thermal, fall from great height, collision with a train - for other forms of trauma - sharp force trauma, firearm injury - may have to interpreted with caution, particularly with regard to what can be ruled out.
Virtual autopsy as a screening test before traditional autopsy: The verona experience on 25 Cases
2018, Journal of Pathology Informatics
Background: Interest has grown into the use of multidetector computed tomography (CT) and magnetic resonance imaging as an adjunct or alternative to the invasive autopsy. We sought to investigate these possibilities in postmortem CT scan using an innovative virtual autopsy approach. Methods: Twenty-five postmortem cases were scanned with the Philips Brilliance CT-64 and then underwent traditional autopsy. The images were interpreted by two blinded forensic pathologists assisted by a radiologist with the INFOPSY® Digital Autopsy Software System which provides three-dimensional images in Digital Imaging and Communications in Medicine format. Diagnostic validity of virtual autopsy (accuracy rate, sensitivity, specificity, and predictive values) and concordance between the two forensic pathologists (kappa intraobserver coefficients) were determined. Results: The causes of death at traditional autopsies were hemorrhage due to traumatic injuries (n = 8), respiratory failure (5), asphyxia due to drowning (4), asphyxia due to hanging or strangulation (2), heart failure (2), nontraumatic hemorrhage (1), and severe burns (1). In two cases, the cause of death could not be ascertained. In 15/23 (65%) cases, the cause of death diagnosed after virtual autopsy matched the diagnosis reported after traditional autopsy. In 8/23 cases (35%), traditional autopsy was necessary to establish the cause of death. Digital data provided relevant information for inferring both cause and manner of death in nine traumatic cases. The validity of virtual autopsy as a diagnostic tool was higher for traumatic deaths than other causes of death (accuracy 84%, sensitivity 82%, and specificity 86%). The concordance between the two forensic pathologists was almost perfect (>0.80). Conclusions: Our experience supports the use of virtual autopsy in postmortem investigations as an alternative diagnostic practice and does suggest a potential role as a screening test among traumatic deaths.
Virtopsy Computed Tomography in Trauma: Normal Postmortem Changes and Pathologic Spectrum of Findings
2015, Current Problems in Diagnostic Radiology
Citation Excerpt :
Although both qualitative and quantitative CT studies to determine the etiology of air space opacities in PMCT have been described in the literature, correlation with time and mechanism of injury is most essential to understand the significance of the lung parenchyma findings.33,34 The diagnosis of aspiration pneumonia may be suggested if similar attenuating fluid is noted in the airways, esophagus, and stomach, with opacities in dependent portions of the lung35 (Fig 22). Similarly, drowning can be suspected if, along with frothy fluid in airways, fluid is also noted in paranasal sinuses and mastoid air cells, with high-density lung opacities.36
Virtopsy or virtual autopsy is an emerging technique, developed to supplement traditional forensic autopsy. Virtopsy can be done by using imaging techniques such as computed tomography (CT) and magnetic resonance imaging. Virtopsy CT comprises a pan-body noncontrast CT scan obtained after death. Virtopsy CT is useful in trauma cases as it can provide an overview of injuries sustained by the victim; detect craniofacial, cerebral, thoracic, and osseous injuries; and suggest putative causes of death. This can reduce the time taken for forensic autopsy and sometimes obviate the need for a forensic autopsy. However, virtopsy CT reporting is not exactly synonymous with interpreting antemortem contrast-enhanced CT images as postmortem decompositional changes also occur. Awareness of imaging appearances of both postmortem putrefactive changes and pathologic findings is essential to avoid errors in interpretation and enable estimation of cause of death in patients with trauma.
Postmortem volumetric CT data analysis of pulmonary air/gas content with regard to the cause of death for investigating terminal respiratory function in forensic autopsy
2014, Forensic Science International
Citation Excerpt :
Recent advances in forensic radiology include postmortem imaging using computed tomography (CT) and magnetic resonance imaging (MRI), which provides a noninvasive procedure to detect bone and visceral lesions (virtual autopsy) as well as various possibilities to analyze the status of viscera before autopsy [1–9].
Postmortem CT (PMCT) is useful to investigate air/gas distribution and content in body cavities and viscera. The present study investigated the procedure to estimate total lung air/gas content and aeration ratio as possible indices of terminal respiratory function, using three-dimensional (3-D) PMCT data analysis of forensic autopsy cases without putrefactive gas formation (within 3 days postmortem, n = 75), and analyzed the volumetric data with regard to the cause of death. When 3-D bilateral lung images were reconstructed using an image analyzer, combined lung volume was larger in drowning (n = 12) than in alcohol/sedative-hypnotic intoxication (n = 8) and sudden cardiac death (SCD; n = 10), and intermediate in other cases, including mechanical asphyxiation (n = 12), fire fatalities due to burns (n = 6) and carbon monoxide intoxication (n = 7), fatal methamphetamine abuse (n = 7), hyperthermia (heatstroke; n = 6) and fatal hypothermia (cold exposure; n = 7). Air/gas content of the lung as detected using HU interval between −2000 and −400 (‘effective’ lung aeration areas) and between −2000 and −191 (total lung aeration areas) as well as the ratios to total lung volume (‘effective’ and total lung aeration ratios, respectively) was higher in mechanical asphyxiation, drowning, fatal burns and hypothermia (cold exposure) than in SCD, and was intermediate in other cases. ‘Effective’ and total lung aeration ratios may be useful for comparisons between specific causes of death to discriminate between hypothermia (cold exposure) and drug intoxication, and between SCD and other causes of death, respectively. These findings provide interesting insights into potential efficacy of PMCT data analyses of lung volume and CT density as well as lung air/gas content and aeration ratio with regard to the cause of death, as possible indicators of terminal respiratory function, as part of virtual autopsy of the viscera in situ.
Sudden death in a case of sickle cell anemia: Post-mortem computed tomography and autopsy correlation from a radiologist's perspective
2013, Legal Medicine
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We have illustrated that the radiologist was able to detect the positive as well as ruling out the important negative findings related to SCA based on his clinical radiology background. There are several reports in the literature describing the added value of post-mortem imaging prior to autopsy, highlighting the agreement between imaging and autopsy findings [10–12]. In this case, these important post-mortem imaging findings provide crucial information to the forensic pathologist and the possible cause of death is most probably related to complication of SCA.
Sickle cell anemia (SCA) is a hemolytic disease characterized by the production of abnormal hemoglobin chains and distorted red blood cell morphology or sickling. “Sickle cell crisis” includes vaso-occlusive crisis, a plastic crisis, sequestration crisis, haemolytic crisis and often culminating in serious complications, organ damage and even sudden death. Post-mortem computed tomography (PMCT) findings of sickle cell disease have never been reported in literature. This case of sudden death from acute hemolytic crisis in SCA where post-mortem computed tomography (PMCT) and autopsy findings complemented each other, both revealing findings invisible to the other and both crucial to the case.

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Pros and cons of post-mortem CT imaging on aspiration diagnosis

Abstract

Introduction

Section snippets

Study population

Autopsy

Discussion

Forensic Sci

Forensic Sci Int

J Forensic Leg Med

Leg Med (Tokyo)

Eur J Radiol

Forensic histopathology

Forensic pathology

A review of 80 barium meal examinations in patients with rheumatoid arthritis: were they necessary?

Br J Clin Pract

Aspiration of food and vomit

Q J Med

MDCT evaluation of foreign bodies and liquid aspiration pneumonia in adults

AJR Am J Roentgenol

Near drowning: thin-section CT findings in six patients

J Comput Assist Tomogr

Radiographic pulmonary changes in neardrowning

Radiology