Postmortem Computed Tomography and Computed Tomography Angiography: Cardiothoracic Imaging Applications in Forensic Medicine

Pediatric forensic postmortem computed tomography: basics to advanced

The approach to postmortem computed tomography (CT) differs significantly from that of diagnostic CT in living patients. Elimination of artifacts such as noise and beam hardening as well as optimization of tissue contrast requires alteration of exposure parameters from protocols designed to limit radiation dose in children. Multiple scans may be performed, and detailed post-processing can be used to enhance subtle findings such as small intracranial extra axial collections and non-displaced fractures. Basics of postmortem CT technique are discussed here as well as advanced techniques in scanning and post-processing.

Postmortem contrast-enhanced computed tomography via direct large-vessel puncture

The aim of this study was to assess the usefulness of postmortem contrast-enhanced CT (PMeCT) performed via direct large-vessel puncture when routine postmortem CT suggests a vascular lesion as the cause of death. PMeCT was performed in 9 cases (4 male, 5 female) with a mean age of 76 years (range 52-92) at the time of death. The mean time elapsed since death was 29.1 h (12.0-72.0). The location of the target vessel for puncture was determined based on the CT table position and a grid placed on the body surface. An 18-G spinal needle was advanced to the puncture site, and the needle tip was confirmed to have reached the intended blood vessel. Using negative pressure with a 20-ml syringe, the needle tip was advanced until reverse bleeding was confirmed. Diluted contrast medium was injected slowly to ensure its dispersion within the blood vessels. Following confirmation of no extravasation, additional doses of diluted contrast agent were injected in 3-4 divided doses, with CT scans obtained at each step to track the distribution of contrast agent over time. PMeCT was successful in all cases, revealing cardiac tamponade in 7 (ascending aortic dissection, n = 6; cardiac rupture, n = 1), thoracic aortic aneurysm rupture, n = 1, and iliac artery aneurysm rupture, n = 1. There were no cases of procedure-related extravasation (pseudo-lesions). When postmortem CT reveals pericardial hematoma or bleeding in the thoracic or abdominal cavity, PMeCT can identify the source of bleeding.

The value of PMCTA in the diagnosis of coronary atherosclerosis in isolated human hearts

Postmortem computed tomography (PMCT) has a limited value in investigating coronary artery disease, despite several obvious advantages over the conventional autopsy. To address this issue, postmortem computed tomography angiography (PMCTA) has been introduced into various studies, where it has been used to investigate natural and unnatural deaths involving vascular damage, occlusion, or other pathologies of the vascular system. To investigate the application value of PMCTA in the diagnosis of coronary artery stenosis in ex situ hearts, the water-based contrast media were injected into isolated hearts, scaned, and finally compared with gold standards (autopsy and histology findings of the coronary artery). This study involved 16 subjects from the Academy of Forensic Science who were suspected to have died of sudden death without traumatic injuries. Unenhanced PMCT was performed first, followed by PMCTA using a water-based contrast agent, injected into the coronary arteries of isolated hearts using a self-designed angiography device. The image data were reconstructed into three-dimensional (3D) angiography images using software in the angiography facility. The 3D images were recorded and evaluated by two radiologists and then statistically analysed. The results of PMCTA were consistent with the gold standards for the diagnosis of coronary artery stenosis (P > 0.05). However, water-based contrast media can only be used to examine the pathological changes of blood vessels, which may have limitations in the diagnosis of causes of death such as myocardial oedema. PMCTA can be used as a new method to evaluate the degree of coronary atherosclerosis in addition to traditional autopsy. The 3D reconstruction technique reveals the coronary artery lesions more objectively and vividly and provides the opportunity to re-read the data at any time.

Key points

The methods and parameters for coronary angiography in isolated human hearts were standardized based on the previous researcher.PMCTA in isolated human hearts is including the 3D reconstruction technique that reveals the coronary artery lesions more objectively and vividly, and provides the opportunity to re-read the data at anytime.PMCTA could only be used to examine the pathological changes of blood vessels, which might have limitations for the diagnosis of causes of death.PMCTA in isolated human hearts can be viewed as an auxiliary method for establishing the cause of death, which can provide an assessment of degree and extent of arterial stenosis and accurately help determine the abnormal location.

Post-mortem Computed Tomographic Angiography in Equine Distal Forelimbs: A Feasibility Study

In-depth understanding of pathophysiological processes occurring in the vasculature of the equine distal limb is of great importance to improve both diagnostic and therapeutic approaches to diseases. To gain further insights, a model allowing high-resolution 3D-visualization of the vasculature is necessary. This pilot study evaluated the feasibility of restoring vascular perfusion in frozen-thawed distal equine cadaver limbs without prior preparation using computer tomographic imaging (CT). Five frozen-thawed, radiographically normal forelimbs were perfused with a lipophilic contrast agent through the median artery and radial vein in three phases (arterial, venous, and arterial-venous combined (AVC) dynamic). For comparison, one additional limb was perfused with a hydrosoluble contrast agent. The CT-studies (16-slice MDCT, 140 kV, 200 mA, 2 mm slice thickness, 1 mm increment, pitch 0.688) were evaluated at 11 specified regions for visualization of the vasculature and presence of artifacts or anatomic variations. The protocol used in this study proved to be feasible and provided good visualization (93.1%) of vasculature with low rates of artifacts. During the different phases, vascular visualization was similar, but while filling defects decreased in the later phases, extravasation worsened in the 2 limbs where it was observed. Subjectively, the best quality of angiographic images was achieved during the AVC dynamic phase. Perfusion with hydrosoluble contrast resulted in significantly lower vascular visualization (74.0%) and higher artifact rates. This study shows that reperfusion of frozen-thawed equine distal limbs with a lipophilic contrast agent allows for high-quality 3D-visualization of the vasculature and may serve as a model for in situ vascular evaluation in the future.

Lighting up forensic science by aggregation-induced emission: A review

Forensic science requires a fast, sensitive, and anti-interfering imaging tool for on-site investigation and bio-analysis. The aggregation-induced emission (AIE) phenomenon exhibits remarkable luminescence properties (large Stokes shift, diverse molecular structures, and high photo-stability), which can provide a viable solution for on-site analysis, while at the same time overcoming the problem of aggregation-caused quenching (ACQ). Based on the outstanding performance in chemical analysis and bio-sensing, AIE materials have great prospects in the field of forensic science. Therefore, the application of AIE in forensic science has been summarized for the first time in this article. After a brief introduction to the concept and development of AIE, its applications in the determination of toxic or hazardous substances, based on data on poisoning deaths, has been summarized. Subsequently, besides the bio-imaging function, other applications of AIE in analyzing markers related to forensic genetics, forensic pathology, (focusing on the corpse) and clinical forensics (focusing on the living) have been discussed. In addition, applications of AIE molecules in criminal investigations, including recognition of fingerprints and blood stains, detection of explosives and chemical warfare agents, and anti-counterfeiting have also been presented. It is hoped that this review will light up the future of forensic science by stimulating more research work on the suitability of AIE materials in advancing forensic science.