|Year : 2021 | Volume
| Issue : 1 | Page : 14-23
Application of virtopsy in forensic pathology
Wang Yucong, Zhu Haibiao, Liu Ran, Zhang Haidong, Zhao Dong, Wang Xu, Yang Tiantong
Key Laboratory of Evidence Law and Forensic Science, Ministry of Education China University of Political Science and Law; Collaborative Innovation Center of Judicial Civilization, Beijing, China
|Date of Submission||25-Oct-2020|
|Date of Decision||21-Nov-2020|
|Date of Acceptance||05-Dec-2020|
|Date of Web Publication||24-Mar-2021|
Key Laboratory of Evidence Law and Forensic Science, Ministry of Education China University of Political Science and Law, Beijing, 100088
Source of Support: None, Conflict of Interest: None
Virtopsy employs computed tomography and magnetic resonance imaging, which are commonly used in clinical medicine, to determine the cause and manner of death. Virtopsy is a multidisciplinary technique that combines forensic medicine, pathology, radiology, computer graphics, biomechanics, and physics. Virtopsy is rapidly gaining importance in forensic science and has been extensively studied in several areas of forensic pathology. In this study, we reviewed domestic and international research on causes of death, traffic injuries, medical disputes, gunshot trauma, postmortem changes, and inference of time of death to discuss with colleagues the role of virtopsy in forensic pathology.
Keywords: Computed tomography, forensic pathology, magnetic resonance imaging, virtopsy
|How to cite this article:|
Yucong W, Haibiao Z, Ran L, Haidong Z, Dong Z, Xu W, Tiantong Y. Application of virtopsy in forensic pathology. J Forensic Sci Med 2021;7:14-23
|How to cite this URL:|
Yucong W, Haibiao Z, Ran L, Haidong Z, Dong Z, Xu W, Tiantong Y. Application of virtopsy in forensic pathology. J Forensic Sci Med [serial online] 2021 [cited 2021 Jul 28];7:14-23. Available from: https://www.jfsmonline.com/text.asp?2021/7/1/14/311862
| Introduction|| |
Virtopsy is an anatomical method that uses modern medical imaging and computer technology combined with anatomical principles and technical requirements to obtain internal and external information from a corpse to clarify the cause of death without damaging or destroying the integrity of the body. The noninvasive (or minimally invasive) nature of virtopsy is its most important feature, offering many advantages over conventional gross autopsy. The resultant introduction of virtopsy into forensic pathology appraisal, therefore, has been an inevitable development.
At present, several departments, institutions, and colleges in China, such as the Academy of Forensic Science, the Beijing Public Security Bureau, the Institute of Evidence Science of China University of Political Science and Law, and the Changchun Public Security Bureau, have been equipped with devices and researchers. This has provided a solid foundation for the development of virtopsy technology in China. The authors, therefore, have collected and reviewed both domestic and international studies on virtopsy to discuss its current applications and to predict possible future trends.
| Cause of Death Analyses|| |
\Virtopsy technology allows for an examination of the inside of the airway of asphyxia deaths caused by foreign body obstruction, aiding in the initial identification of the cause of airway obstruction and thus the cause of death. In the case of suspected asphyxia, a computed tomography (CT) can be used as a preliminary screening procedure prior to autopsy to collect this information quicker and more efficiently.
Decker et al. evaluated the value of CT in the identification of asphyxia in neck compression-related deaths, such as constriction, strangulation, or throttling. In cases of strangulation, CT was similar to conventional autopsy in the detection of hyoid bone fractures and soft tissue hemorrhage but was more sensitive for microfractures. In the cases of lighter throttling forces, clear signs of neck compression are often lacking. With the development of radiological techniques, Fais et al. found that micro-CTs and the ossification of thyroid cartilage could be used to detect microfractures that would be difficult for conventional autopsy or even conventional CT to detect. In addition, magnetic resonance imaging (MRI) studies on asphyxia caused by neck compression have shown that MRIs can clearly display subcutaneous fatty tissue hemorrhages in the neck; muscle hemorrhages in the neck and larynx; and soft tissue injury in the lymph nodes, pharynx, and larynx. This easily compensates for the difficulty that conventional autopsy and CT have in detecting internal soft tissue injury comprehensively.
In 2018, Schulze et al. determined that “the gas bubble sign” on CT after constriction could be a diagnostic indicator of neck trauma, suggesting a laryngeal fracture [Figure 1]c and [Figure 1]d. The gas bubble sign seen in radiology examinations is often associated with trauma; however, the mechanism of its formation remains unclear. The large horn of the hyoid bone and the thyroid cartilage are most prone to fractures, and some microfractures are difficult to detect under conventional anatomical visualization. However, the sensitivity of the gas bubble sign to fracture diagnosis is 79.2%, and the accuracy is 83.0%. Moreover, the researchers observed laryngeal deformity or dislocation (LDD) on CT examinations in more than half of the deaths caused by constriction [Figure 1]a and [Figure 1]b. When a fracture occurs, LDD was noted to be present in most cases (83.0%). The failure to detect this manifestation under conventional anatomical visualization may be due to unavoidable mechanical manipulation during autopsy. The application of virtopsy techniques can improve the detection rate of laryngeal fractures and serve as a powerful tool for neck trauma detection.
|Figure 1: (a) Photograph of the external effects of constriction. (b) Horizontal computed tomography reveals a fracture of the upper corner of the thyroid cartilage and a nearby “gas bubble sign” (blue arrow). (c) Computed tomography three-dimensional reconstruction (right view) showing a thyroid cartilage fracture (orange arrow). (d) Computed tomography three-dimensional reconstruction (anterior view) reveals a fracture-related dislocation of the hyoid bone (LDD, white arrows); due to the LDD, the position of the thyroid cartilage is slightly dislocated relative to the hyoid bone|
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Degeneration or trauma to the spine can lead to gas accumulation in the intervertebral discs, resulting in the “intervertebral disc vacuum phenomenon”, for which CT is the most effective test. Vasiliki et al. have suggested that the presence of the intervertebral disc vacuum phenomenon on CT is correlated with age, degenerative changes in the spine, and the type of constriction. Importantly, the presence of a centrally located intervertebral disc vacuum phenomenon suggests that the spine may have been subjected to longitudinal extension forces, which is crucial for determining the cause of death [Figure 2].
|Figure 2: (a) Sagittal computed tomography of a centrally located “intervertebral disc vacuum phenomenon.” (b) The intervertebral disc under conventional autopsy visualization. (c) “Intervertebral disc vacuum phenomenon” in pathological microscopic view|
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The distinction between hanging before death or hanging after death is another important aspect of forensic pathology. Aghayev et al. stated that pneumomediastinum and soft tissue emphysema are specific “vital reactions” to death by hanging. During hanging to death, the constrictor cable compresses the upper respiratory tract, and the victim breathes heavily due to hypoxia, which causes the alveolar pressure to increase dramatically, destroying the pulmonary barrier. Air then escapes and leaks along the bronchi into the connective tissues of the mediastinum and neck, forming pulmonary mediastinum and cervical soft tissue emphysema [Figure 3], which are reliable vital reactions to the victim's struggle and violent respiratory effort due to airway compression. This manifestation is difficult to observe in conventional autopsy but can be easily detected and documented using virtopsy techniques.
|Figure 3: Three-dimensional reconstruction of the lung showing emphysema in the right neck (thick arrow) and mediastinum (dashed arrow)|
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Drowning is another type of mechanical asphyxia and a common means of suicide, but there are homicides which involve drowning or postmortem dumping as well the assessment of drowned bodies may be necessary for criminal cases and therefore, it is important to be able to clarify the cause of death. In 2007, Levy et al. found that CTs of drowned corpses had a unique imaging manifestation of frothy airway fluid or high-attenuation sediment in the airways compared to sudden death. In China, Jian et al. conducted a controlled study by establishing a drowned rabbit model and compared it to animal models of hemorrhagic shock and mechanical asphyxia. The results showed that the lungs in the drowned group showed characteristic diffuse gross glass-like changes on CT (diffuse and uniform density-increasing opacities). There were no obvious abnormalities in the corresponding areas in the hemorrhagic shock group, and only a small portion of the mechanical asphyxia group showed similar changes. In the drowned group, the CT values and volumes of the lungs were significantly higher (P < 0.05). This suggests that the postmortem lung images, combined with the changes in lung volume and CT values, could effectively reflect the characteristic changes in the virtopsy of the lungs of antemortem drowning, providing a basis for forensic identification.
Sudden death from cardiovascular diseases
In forensic pathology, the primary criterion for determining sudden death due to coronary artery disease is the pathological manifestation of coronary atherosclerosis. Therefore, in virtopsy, the identification of coronary artery atherosclerosis is crucial.
Although the combination of a multislice CT (MSCT) and the coronary artery calcification score can be used to detect obvious arterial calcification in cases of sudden coronary death, it is difficult to assess the degree of stenosis and occlusion of coronary arteries using only a plain CT due to technical limitations. Some scholars have drawn on their clinical application experience to introduce CT angiography (CTA) into virtopsy and have obtained good results. At present, cadaveric CTA is considered an effective method for the examination of vascular lesions, the findings from which are divided into two main approaches: in vivo and in vitro.
Roberts et al. demonstrated an in vivo cadaveric CTA technique that involved inserting a urinary catheter into the left common carotid artery. In 8 of the 10 samples taken for virtopsy using this technique, there was a good correlation between the imaging findings and those of a conventional cadaveric autopsy. The authors also discussed, however, some of the shortcomings of CTA, namely, that air in the blood vessel or postmortem blood clots could cause an incomplete filling of the contrast agent. To manage this, they suggested changing the cadaveric position during contrast injection to improve coronary air blockage. Additionally, the presence of intravascular air could be considered a negative reaction to contrast that would not necessarily affect diagnostic accuracy [Figure 4].
|Figure 4: Left: Coronary computed tomography angiography shows severe focal stenosis of the left anterior descending artery; Right: Coronary computed tomography angiography shows coronary artery filled locally with contrast and gas. Although the vessel is filled with gas, the lumen can still be clearly observed|
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In a study of in vitro cadaveric CTA, Chinese scholars Qian et al. improved the in vitro cardiac CT imaging device and performed CTA on hearts that had been removed intact before autopsy. Their findings showed that the CTA technique was highly accurate in diagnosing the degree of atherosclerotic stenosis in coronary arteries [Figure 5]. Postmortem CTA can also provide a clear, objective, and visual representation of stenosis through three-dimensional (3D) reconstruction. In contrast to postmortem in vivo coronary CTA, in vitro coronary CTA can remove postmortem blood clots that obstruct the vessel, preventing the vessel from being fully blocked, thus achieving better imaging results.
|Figure 5: (a) Computed tomography three-dimensional reconstruction shows localized calcification of the left anterior descending artery with severe stenosis and severe stenosis of the right coronary artery. (b) Computed tomography multiplanar reconstruction shows localized calcification of the left anterior descending artery with severe stenosis. (c) Histopathological examination shows grade IV stenosis of the lumen of the left anterior descending artery|
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To compensate for the technical limitations of plain CT, MRI has been used to examine coronary arteries. On MRI, chemical shift artifacts along the coronary arteries of cadaveric hearts have been found to be indicative of coronary vascular patency, and that the pairs of “dark bands” that appear in their place are indicative of stenosis.
In addition to coronary atherosclerosis, myocardial infarction is a typical pathological change in sudden coronary death. In 2011, Jackowski et al. discovered that MRIs could reliably be used to visualize and distinguish chronic, subacute, and acute foci of myocardial infarction. In cases of sudden death, MRIs may even reveal ischemic lesions that are undetectable in autopsy and routine histopathology.
The postmortem CTA technique has also been applied to identify cases of sudden death due to pulmonary embolism. In one study, circulation was restored to a cadaver that had been dead for 15 min by applying chest compressions, allowing for a CTA to be performed. The images collected confirmed the presence of a pulmonary embolism [Figure 6].
|Figure 6: Horizontal computed tomography shows the site of pulmonary artery embolism (white arrow)|
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For autopsies after sudden death from cardiovascular disease, the measurement of cardiac parameters is equally important. MRI technology can be used to measure the thickness of the ventricular wall and the circumference of the heart valves. Despite obvious differences in values compared to autopsy measurements, (e.g., the myocardial wall is thicker on cardiac MRI in situ than at autopsy), the two have a strong correlation.
With the recent development of minimally invasive puncture sampling techniques, the development of virtopsy for sudden cardiovascular death has also been promoted. Ross et al. conducted whole-body CTA examinations supplemented by CT-guided puncture sampling on 20 cases of acute chest pain diagnosed before death. The results of CTA combined with puncture sampling in 19 cases were consistent with those of conventional autopsy judgments. In seven of these cases, CT-guided puncture sampling also provided additional histopathological information that further confirmed the cause of death. The results indicated that postmortem CTA combined with CT-guided puncture biopsy has a broad application in the identification of sudden death from cardiovascular diseases.
Sudden death from respiratory system diseases
There are many causes of sudden death from respiratory system diseases, with various types of pneumonia being the most common. Postmortem MSCT and MRI can show laryngeal edema and occlusion at the level of the vocal cords, severe pneumonia and atelectasis in both lungs, bronchiectasis, and swelling of the pharyngeal tonsils, all of which correspond to the findings of conventional autopsy and can be confirmed by histological and microbiological examinations. Although there are few virtopsy studies involving such sudden deaths, the expected value of virtopsy in the identification of sudden death from respiratory diseases cannot be overlooked due to the unique technical advantages of CT and other radiological examinations in pulmonary imaging.
Sudden death from central nervous system diseases
Yen et al. performed CT and MRI scans on 57 cadavers and evaluated the value of virtopsy in cranial autopsy. They demonstrated that the results of virtopsy were comparable to those of conventional autopsy. Due to the unique and powerful postprocessing capabilities of CT, data could be easily obtained, and MRIs obtained some information not detected by conventional autopsy.
In traditional craniocerebral anatomy, the examination of liquefied brain tissue is a major challenge for forensic pathologists, as the liquefaction of brain tissue makes it impossible to determine disease or injury from a broad view, and obtaining satisfactory results from microscopic examination is often difficult. Tschui et al. performed MRI brain examinations on 35 decomposed adult cadavers and found that even in the late stages of decomposition, the anatomical structure of the brain was accurately interpreted using MRI imaging [Figure 7]. This is undoubtedly the greatest advantage of virtopsy in the field of craniocerebral autopsy.
|Figure 7: (a) Conventional autopsy visualization of softened brain tissue. (b) Magnetic resonance imaging of softened brain tissue: Gray and white matter are significantly easier to distinguish than on autopsy. (c) Conventional autopsy visualization of liquefied brain tissue. (d) Magnetic resonance imaging of liquefied brain tissue: Midline, gray and white matter, and a portion of the superior sagittal sinus are demonstrated, and obvious intracranial pathological changes are excluded. The arrow shows the accumulation of putrefied gas|
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For the most common cerebrovascular accidents in central nervous system diseases, conventional autopsies can often reveal the general location of intracranial hemorrhage or cerebral infarction, but it is difficult to look for specific diseased blood vessels. Franckenberg et al. performed CTA and magnetic resonance angiography (MRA) on a man who died of an unknown cause. Despite the presence of normal postmortem brain tissue edema, the radiological examination showed cerebral vascular malformations, extensive cerebral hemorrhage and edema, and ventricular stenosis. MRA is of better quality than CTA, allowing better assessment of soft tissue and brain parenchymal lesions [Figure 8]a, [Figure 8]b, [Figure 8]c, [Figure 8]d.
|Figure 8: (a-c)Cranial computed tomography angiography and magnetic resonance angiography show cerebral artery malformation (red arrows and red circles), (c)midline deviation (white arrows),(c and d) and massive hemorrhage on the left side of the brain (black asterisks)|
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Death by burning, freezing, and electric shock
Death by burning
Heat can cause tissue damage and even death. Bakker et al. performed CT scans of 50 cadavers retrieved from a fire and found that CT was valuable in assessing soft tissue and bone injuries and in locating gases or foreign bodies. In addition, CT can reveal typical changes in the burned parts of the body, such as skull fractures and epidural thermal hematomas. However, it is difficult to detect signs of superficial thermal injury and soot and burns in the airway. Histological and toxicological tests are needed to identify the vital reaction of the body in a fire and to determine the exact cause of death.
When performing a traditional autopsy, experts are often at a loss when confronted with severe burns or even carbonization. However, CT and MRI examinations can reveal pathological changes in carbonized cadavers, and virtopsy has enormous potential as a tool for carbonized autopsies.
Death by freezing
Iliopsoas hemorrhage is a rather specific vital reaction to frostbite. As early as 1979, Dirnhofer et al. proposed iliopsoas hemorrhage as a diagnostic criterion for death from hypothermia and considered it a specific manifestation of frostbite. In 2008, Aghayev et al. performed MSCT and MRI on three cases of frostbite and found hemorrhages in the left psoas major and bilateral iliopsoas muscles, confirming the presence of hemorrhage found by conventional autopsy [Figure 9], proving that iliopsoas hemorrhage may be a specific manifestation of hypothermic death. Some foreign scholars have recently suggested that the hemorrhaging of other core skeletal muscles besides the iliopsoas may also be a unique feature of hypothermic death. Therefore, virtopsy enables us to more clearly, comprehensively, and intuitively detect skeletal muscle hemorrhage in suspected victims of death by freezing and more efficiently determine the cause of death.
|Figure 9: (a) Magnetic resonance imaging demonstrating high-intensity signals of the left psoas major muscle (thick arrows) and bilateral iliac muscles (thin arrows). (b) Conventional autopsy visualization of a psoas major muscle hemorrhage (thick arrows)|
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Death by electric shock
Death by electric shock is most often caused by accidents or catastrophes but can also result from suicide and homicide. The typical pathological changes are skin damage (current spots and skin metallization), and tissue damage caused by current flowing through the organs and muscles. Baumeister et al. performed a comprehensive imaging examination of a case of death by electric shock. Except for the inability to detect lightning pattern marks on the surface, the results of virtopsy were consistent with those of superficial cadaver examination and conventional autopsy, demonstrating clear pathological manifestations of electric shock injuries such as current inlets [Figure 10]. In particular, rhabdomyolysis, which is difficult to observe under conventional autopsy visualization, found on MRI provided the strongest evidence that the deceased suffered an electric shock injury [Figure 11]. Moreover, CTA can also detect significant perihepatic and gastric contrast (intravenous) deposits. The authors considered these manifestations to be the result of contrast medium extravasation, attributed to the defects of liver parenchyma and gastric mucosa caused by heat or electricity. In the autopsy, only scattered punctate hemorrhages were detected in the gastric mucosa. These findings confirm the capability of virtopsy to visualize electric trauma and thus provide support for the identification of cause of death by electric shock.
|Figure 10: Computed tomography three-dimensional reconstruction shows the same electrical inlets(white arrows in 10-a) and outlets (white arrows in 10-b) of the cadaveric limbs as a conventional autopsy(white arrows in 10-cdef)|
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|Figure 11: (a) The autopsy picture shows the superficial and deep soft tissue defects of the limbs (arrows) and lightning strike patterns (ellipses). (b) Computed tomography three-dimensional reconstruction shows soft tissue destruction consistent with autopsy (arrows). (c) Computed tomography three-dimensional skeletal reconstruction shows femoral fractures (arrows). (d) Coronal magnetic resonance imaging shows high-intensity signal within the skeletal muscle caused by rhabdomyolysis due to electric shock (arrows) and diffuse systemic edema|
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| Application in Traffic Injury Cases|| |
The use of MSCT and MRI in the identification of cause of death in traffic accidents can reveal cardiac injuries caused by blunt force, proving that MSCT and MRI are effective tools for virtopsy diagnosis. In 2009, Buck et al. applied MRI to perform virtopsy on five road traffic accident victims and proposed that MRI could be applied to detect bone contusions [Figure 12], which could serve as reference for determining the collision location of traffic accidents.
|Figure 12: Left knee of a woman injured in a traffic accident: (a) Color model of the left knee generated using three-dimensional photogrammetry and optical surface scan. (b) magnetic resonance imaging shows patellar contusion (red arrows) and knee joint effusion (blue arrows)|
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Chinese scholars Kun et al. applied virtopsy after a traffic accident in which an airbag caused the death of a driver and passengers. In this case, no injury was visualized superficially and no abnormalities such as fracture, dislocation, or hemorrhage were found on imaging of the body, but the head CT indicated that there were traumatic changes at the base of the skull and brain tissue, involving the brain stem. A comprehensive analysis indicated that death occurred from craniocerebral injury. Whiplash injury is common for vehicle occupants and MSCT and MRI have strong sensitivity to lesions of the vertebral body and spinal cord, demonstrating the value of their application in traffic accidents.
Indeed, since traffic accident identification of death is complex, involving multiple factors, such as humans, vehicles, and the environment, autopsy alone cannot be used for the determination of death for traffic accidents. In 2007, Buck et al. combined virtopsy with a high-precision 3D surface scanning technique for the first time to analyze the sequence of a traffic accident. Based on the virtopsy, they used a high-precision 3D surface scanning technique to digitize the cadaver and vehicle, build 3D models, and analyze the vehicle and human parameters as well as the damage and injury, reconstructing the accident and confirming the collision relationship [Figure 13].
|Figure 13: Analysis of the collision relationship between the bicycle and the left calf. (a) The collision relationship between physical injury and the bicycle frame screw (white arrows). (b) The collision relationship between the left tibial wedge fracture and the bicycle bumper (white arrows)|
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| Application in Medical Dispute Cases|| |
Scholars outside of China have spent years performing CT/CTA on thousands of patients who have died in hospitals in a variety of departments, including emergency medicine, cardiothoracic surgery, gastroenterology, and neurosurgery. They found a high concordance rate between postmortem CT/CTA and conventional autopsy, with an agreement rate of 93.0% between the diagnosis and the antemortem clinical diagnosis. Postmortem CT/CTA is more useful in reconstructing areas where adverse events occur during surgery, facilitating the observation of adjacent structures, the search for subtle sources of bleeding, and the evaluation of postoperative vascular perfusion. In special cases, the results of virtopsy can be compared with antemortem imaging to explain questionable diagnoses or medical practices and to determine the facts.
Neonatal deaths are also highly associated with medical disputes. Chinese scholars in one study assessed antemortem CTs of fetuses who died postpartum. The CTs showed a diffuse increase in density of opacities in both lungs, large dense shadows (consolidation), and no inflated lung tissue opacities. These findings were in accordance with the atelectasis seen in conventional gross autopsies. With reference to histopathologic examination, the cause of death was determined to be respiratory and circulatory failure due to neonatal pulmonary hyaline membrane disease. In traditional autopsies, it is sometimes necessary to use the lung float test to determine whether a newborn is alive or stillborn; conversely, virtopsy only requires a simple scan to determine the condition of the lungs, which to some extent circumvents the influence of gas produced by body decomposition on the float test.
| Application in Cases Involving Firearms and Ammunition|| |
Multislice spiral CT can guide the identification of cases involving gunshot wounds, thus eliminating the need for whole-body autopsies. CT image reconstruction techniques can accurately identify the entry and exit points of a firearm projectile and investigate the trajectory and characteristics of the projectile, which is far more intuitive than performing a traditional autopsy. From another perspective, Gibb et al. have used real cases and animal models as samples to demonstrate CT manifestations and characteristics of injuries caused by several types of firearms and ammunition that may be encountered [Figure 14], providing a theoretical basis for determining potential causes.
|Figure 14: Left: computed tomography three-dimensional reconstruction shows fractures in right ribs 2–4 (white circles); Right: computed tomography three-dimensional reconstruction shows scattered bullets (blue-green)|
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| Postmortem Changes and Inference of Time of Death|| |
The postmortem changes observed on CT have a certain pattern [Table 1]. For early cadaveric changes, CTs usually clearly show hypostasis of internal organs (i.e., the separation of blood into serum and red blood cells by gravity), which usually appears on CT as a layering of different densities in blood vessels or organs (most often in the lungs). However, hypostasis in the vasculature is often mistaken for thrombosis. Therefore, the researchers explain that hypostasis is mainly found in the lower parts of blood vessels and heart chambers, while thrombi usually have a round or oval outline, often independent of their location. Compared with internal organs, the CT examination of blood gravitational fall effect on skin and subcutaneous tissue is less effective and may only show an increased density of subcutaneous fat and dermal tissue in the image, not allowing for a clear view of cadaveric ecchymoses like in conventional autopsy.
Cadaveric rigor mortis and algor mortis usually do not cause changes to skeletal muscle density, size, or shape under CT; therefore, CT is seldom used to detect them.
Although the liver and kidneys are the first organs to undergo autolysis, on CT examination, they have a normal appearance and structure until putrefaction gas is produced. CT features of brain autolysis are most typical, including blurring and loss of the gray-white matter junction, decrease of brain tissue density, and loss of the sulci and ventricles. During this period, the brain may show only mild softening in routine autopsies, with no obvious abnormalities in appearance. Therefore, CT is highly sensitive in detecting organ autolysis.
The most common of the mid-to late-stage changes are putrefaction. In addition to the intestinal cavity, the intestinal wall, mesentery, and portal venous system are usually the first places where putrefactive gas is observed on CT, and putrefactive fluid is also found in the pleural and peritoneal cavities. However, according to the experience of some authors, the putrefactive gas detected by CT is usually widely and symmetrically distributed throughout the body, and smaller volumes (10–20 mL) of pleural and peritoneal fluid are usually considered normal.
In later stages, when cadavers are heavily putrefactive, the formation of adipocere has a characteristic low-density appearance on CT. Since adipocere formation often coexists with putrefaction, CT findings may show both processes, revealing images of fully or partially decomposed organs and an intact skeletal structure surrounded by subcutaneous fat. Some insects or animals that damage cadavers tend to be attracted to moist areas of the body, such as the mucosae or injuries of the nasal and oral cavities, where irregular foreign body shadows of soft tissue density can be observed on CT.
Charlier et al. examined postmortem changes in the abdominal cavity of the cadaver. The changes in abdominal CT mainly involve the intestinal wall, mesentery, and the portal venous system, showing dilated intestines, a small amount of fluid in the abdominal cavity (liquefied fat and/or decomposition and exudation), and the production of putrefactive gas. In late mummified cadavers, the CT shows collapsed abdominal connective tissues and organs that are barely recognizable in shape and appearance, and in some cases, structural destruction of the abdominal wall due to insect activity.
The inference of time of death plays a vital role in determining the time frame and delimiting the scope of the investigation. Estimating the time of death requires the study of these postmortem changes. As the time of death increases, the CT density of different tissues may change regularly. Koopmanschap et al. have suggested that the density of cerebrospinal fluid and vitreous humor on CT increased with the postmortem interval, and cerebrospinal fluid density on CT was significantly correlated (r2 = 0.65). Nishiyama et al. started with the changes in density of the brain parenchyma and found that 58.6% and 98.4% of postmortem CT scans showed postmortem changes such as unclear brainstem structure and blurred gray matter-white matter junction, respectively, compared with antemortem CT scans. Subsequently, a significant decrease in gray matter density was found within 70 min of death, suggesting cytotoxic brain edema. Over 120 min after death, the density of white matter, lenticular nuclei, and thalamus increased dramatically [Figure 15].
|Figure 15: Computed tomography values of brain tissue after death divided into three groups according to the interval from death to computed tomography scan (a. 48–70 min, b. 71–120 min, and c. 121–433 min). Within 70 min of death, the gray matter computed tomography values decreased (cool color) with time; in contrast, the computed tomography values (warm color) that increased with time were observed mainly in the white matter, lenticular nucleus, and thalamus more than 120 min after death|
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Both studies of postmortem changes and time of death inferences need to be confirmed by a large amount of data. In a review of the progress of postmortem CT image characteristics, Chinese scholars Dong et al. also suggested that exploring and studying the characteristics of postmortem changes on CT remains necessary to improve identification of cause of death, look for patterns of changes to provide reference standards for postmortem CT diagnoses, and expand the application of virtopsy in forensic pathology.
| Summary|| |
Strengths of virtopsy
Whether with CT, MRI, or angiography, virtopsy has the potential to replace traditional autopsies due to their unique imaging capabilities, which allow them to obtain information that is difficult to find when using conventional autopsies.
The information obtained through virtopsy can be preserved for a long time and can be retrieved and used at any time even after the body has been cremated or buried. Considering the limited radiological expertise of some appraisers, information in the form of electronic data can also be transmitted via the Internet, and experts can be hired for remote consultation in difficult cases. In practice, the examination of complex cases often requires the participation of multiprofessional technicians in traces, physics, and chemistry. The digital information provided by virtopsy can more easily be combined with other new digital technology and applied to the reconstruction of traffic accident scenes, collision relationship restorations, and ballistic analyses.
With the advancement of technology, the operation of imaging examinations tends to be simpler, which undoubtedly reduces the difficulty of virtopsy. The appraiser can obtain autopsy data through simple steps such as positioning, locating, and scanning, which greatly improves the operational error tolerance compared to traditional autopsies. With the ease of operation as a strength, virtopsy can be used to guide and optimize the postmortem work, thus avoiding complicated and expensive follow-up operations and reducing the cost of criminal proceedings.
In some special cases, virtopsy greatly reduces the risk of infections contracted from blood or other tissue fluids through in situ noninvasive (or minimally invasive) techniques, circumventing potential concerns based on folklore, beliefs, and culture, decreasing a family's resistance to assessment.
Limitations of virtopsy
Due to technical principles, virtopsy lacks some of the information obtained by the appraiser through touch, smell, and sight during traditional autopsies, and it cannot completely replace cellular examination methods in forensic evidence, pathology, toxicology, and microbiology.
Although domestic and international standards have been issued for the application of virtopsy, such as the Operational Procedures for Forensic Virtopsy issued by the Judicial Forensics Administration of the Ministry of Justice of the People's Republic of China, there is a large gap between these standards and the detailed clinical practice and pathways in clinical medicine. In practice, appraisers need to be selecting test methods and performing operations in a more standardized manner.
It is important to acknowledge that the investment required to perform virtopsy is considerable. Whether in terms of equipment or training of professionals, it remains difficult for China's grassroots police or small-and medium-sized institutes to carry out virtopsy.
| Conclusion|| |
Currently, virtopsy should be a complement to traditional autopsy and viewed as part of the study of forensic pathology. Similar to the relationship between medical imaging and clinical medicine, where medical imaging is routinely used as an adjunct to corroborate diagnoses and provide clinical direction, virtopsy can be a powerful tool in forensic pathology identification, providing direction and evidence for identification.
This article was originally released in Chinese language in the Chinese Journal of Forensic Medicine.
Financial support and sponsorship
Double First Class–Training of Top Talents; (2011-051040) National Natural Science Foundation of China (81971796, 81871523); Beijing Natural Science Foundation of China (7192121,7182022); Open Project of Shanxi Key Laboratory of Forensic Science; Projects Funded by Hubei Key Laboratory of Forensic Science (Hubei University of Police); Academic Innovation Team of Young Teachers of China University of Political Science and Law (19CXTD04, 18CXTD09).
Conflicts of interest
Prof. Dong Zhao and Prof. Xu Wang are editorial board members of Journal of Forensic Science and Medicine.
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