Influence of Radiation Dose and Reconstruction Kernel on Fat Fraction Analysis in Dual-energy CT: A Phantom Study.

BACKGROUND/AIM: The quantitative evaluation of fat tissue, mainly for the determination of liver steatosis, is possible by using dual-energy computed tomography. Different photon energy acquisitions allow for estimation of attenuation coefficients. The effect of variation in radiation doses and reconstruction kernels on fat fraction estimation was investigated. MATERIALS AND METHODS: A six-probe-phantom with fat concentrations of 0%, 20%, 40%, 60%, 80%, and 100% were scanned in Sn140/100 kV with radiation doses ranging between 20 and 200 mAs before and after calibration. Images were reconstructed using iterative kernels (I26,Q30,I70). RESULTS: Fat fractions measured in dual-energy computed tomography (DECT) were consistent with the 20%-stepwise varying actual concentrations. Variation in radiation dose resulted in 3.1% variation of fat fraction. Softer reconstruction kernel (I26) underestimated the fat fraction (-9.1%), while quantitative (Q30) and sharper kernel (I70) overestimated fat fraction (10,8% and 13,1, respectively). CONCLUSION: The fat fraction in DECT approaches the actual fat concentration when calibrated to the reconstruction kerneö. Variation of radiation dose caused an acceptable 3% variation.

An algorithm for automatically generating gas, bone and foreign body visualizations from postmortem computed tomography data.

Post mortem computed tomography (PMCT) can aid in localizing foreign bodies, bone fractures, and gas accumulations. The visualization of these findings play an important role in the communication of radiological findings. In this article, we present an algorithm for automated visualization of gas distributions on PMCT image data of the thorax and abdomen. The algorithm uses a combination of region growing segmentation and layering of different visualization methods to automatically generate overview images that depict radiopaque foreign bodies, bones and gas distributions in one image. The presented method was tested on 955 PMCT scans of the thorax and abdomen. The algorithm managed to generate useful images for all cases, visualizing foreign bodies as well as gas distribution. The most interesting cases are presented in this article. While this type of visualization cannot replace a real radiological analysis of the image data, it can provide a quick overview for briefings and image reports.

The possibility of identifying brain hemorrhage in putrefied bodies with PMCT.

This paper aims to demonstrate that post-mortem CT (PMCT) can locate intracranial hemorrhages, even in decomposed cases. This is of relevance in that post-mortem decomposition is particularly damaging to the brain tissue's consistency, resulting in great difficulties to reliably diagnose and locate intracranial hemorrhages. We searched our case database of the last 11 years to find cases with decomposition of the body, where PMCT and an autopsy had been performed. We identified eleven cases according to these criteria. Postmortem interval ranged from 2 days to 2 weeks, and post-mortem radiological alteration index (RAI) was at or above 49. Eight out of eleven cases showed an intraparenchymal hemorrhage whereas the hemorrhage was extra-axial in the remaining three cases. Autopsy validated the presence of intracranial hemorrhage in all eleven cases, but location could not be confirmed due to liquid state of the brain. PMCT identified and localized intracranial hemorrhages in decomposed bodies, and in all of these cases, autopsy validated their presence. The actual cause of the hemorrhage (e.g. tumor, metastasis, vascular malformation, hypertensive hemorrhage) remained obscure. From this case series, it can be concluded that PMCT may add relevant information pertaining to localization of intracranial hemorrhages in decomposed bodies.

Pseudolesion in the right parafissural liver parenchyma on CT: The base is found in embryology and collagen content.

BACKGROUND: Computed tomography (CT) images of livers may show a hypo-attenuated structure alongside the falciform ligament, which can be a focal fatty pseudolesion and can mimic a malignancy. The preferred location is on the right parafissural site, ventral in segment IVa/b. The etiology is not clear, nor is it known how the histology of this location develops. These are evaluated in this study. METHODS: 40 adult cadavers with autopsy and / or postmortem CT in a university hospital and a forensic center were included. Liver biopsies were taken at the left side of the falciform ligament as control, and at the right side as the possible precursor of a pseudolesion; these were examined for collagen and fat content. Cadavers with steatotic (>5% fat) or fibrotic (>2% collagen) control samples were excluded. RESULTS: Significantly more collagen was present in the right parafissural liver parenchyma: median 0.68% (IQR: 0.32-1.17%), compared to the left side 0.48% (IQR: 0.21-0.75%) (p 0.008), with equal fat content and CT attenuation values. The etiophysiology goes back to the demise of the umbilical venes in the early embryonic and neonatal period. CONCLUSIONS: The right parafissural area contains more collagen and an equal amount of fat compared to the control left side. This supports the hypothesis of delayed, 'third' inflow: the postnatal change in blood supply from umbilical to portal leaves the downstream parafissural area hypoperfused leading to hypoxia which in turn results in collagen accumulation and the persistence of paraumbilical veins of Sappey.

Noninvasive in situ proton MRS in muscle tissue and bone marrow as a novel approach to identify previous freezing in a completely thawed cadaver.

The temporary or permanent storage of human bodies in freezers following a homicide is a documented method for criminal disposal of human corpses. In these cases, the detection of characteristics which indicate that a thawed cadaver or body part was previously frozen provides crucial information for forensic casework. Previous histological and radiological approaches to detect characteristics of previous freezing are based on the formation of bubble-like gas patterns, which are difficult to distinguish from common postmortem gas formation in the course of decomposition. The objective of this study was to detect changes in the muscle tissue and in the bone marrow after freezing and thawing by means of in situ proton magnetic resonance spectroscopy (1 H-MRS) to provide a noninvasive approach to detect postfreezing alterations in human cadavers. In this experimental study, the hind legs of seven sheep were used as substitutes for human tissue. One hind leg underwent 1 H-MRS before and daily after storage in a deep freezer (-20°C) and complete thawing at room temperature (study group: n = 7). The opposite hind leg was kept at room temperature and was measured daily (control group: n = 7). Spectra and relaxation times were measured using single voxel measurements in the muscle tissue and in the bone marrow. 1 H-MRS revealed several changes in the muscle tissue and in the bone marrow after freezing and thawing. A strongly reduced peak area ratio (<20) between bulk methylene and olefinic and glycerol methine and a reduced T2 relaxation time for bulk methylene (<45 ms) measured in the bone marrow were found to be indicators that a sheep leg was previously frozen and thawed independent of the postmortem interval. Noninvasive in situ 1 H-MRS in the bone marrow potentially provides a new method for detecting previous freezing or extreme cooling in cadavers.

Thoracic trauma in fatal falls from height - Traumatic pneumopericardium correlates with height of fall and severe injury.

Pneumopericardium (PPC) describes the collection of gas in the pericardial sac. In tension Pneumopericardium (tPPC), this collection of gas may lead to cardiac tamponade. PPC following blunt trauma is considered a rare finding, as reflected by the low number of case reports on the topic. We analyzed the prevalence and pathophysiology of PPC and the associated trauma in 44 cases of falls from height. We retrospectively analyzed postmortem CT data and autopsy reports of fatal falls in the period March 2014-2017. A valid estimation of the height of the fall and a documented impact on an even and hard surface were inclusion criteria. A total of 44 cases were included in the study. We identified PPC in 18 of the 44 cases, and it was associated with an increased height of the fall, alongside aortic, pericardial, and myocardial ruptures. All cases with PPC also presented with bilateral pneumothorax. Five cases presented with a "ballooning" pericardium, indicating tPPC. PPC is a common finding in cases of falls from great heights. Due to a significant correlation with height and thus impact severity, PPC may be used as a reconstructive element in medico-legal investigations. Association with trauma makes PPC a sign of severe thoracic injury in postmortem and clinical radiology.

Fatal bronchovascular fistula after lobectomy visualized through postmortem computed tomography angiography: A case report.

False aneurysm of the pulmonary artery complicated by bronchovascular fistula formation represents a rare life threating condition. We report a case of fatal hemoptysis after formation of a bronchial fistula in the late postoperative period after sleeve lobectomy. Cause of death was determined by external postmortem examination, post mortem computed tomography (PMCT) and angiography (PMCTA) without conventional autopsy.

Movement of steel-jacketed projectiles in biological tissue in the magnetic field of a 3-T magnetic resonance unit.

PURPOSE: The fact that ferromagnetic bullets can move in air or gelatine when subjected to magnetic resonance (MR) units is well known. A previous study showed that the movement of 7.5-mm GP 11 Suisse bullets also depends on their orientation toward the gantry. In order to compare the movement in gelatine to that in real tissue, we decided to measure the movement of these bullets, as well as 9-mm Luger bullets, in the brain and liver. METHODS: The GP 11 and 9-mm Luger bullets were inserted into the fresh calf brain or pig liver either vertically or horizontally in the x- or z-axis to the gantry. Before and after exposure to a 3-T MR unit, their position was documented by CT. RESULTS: GP 11 bullets rotated more readily and in general proved to be more mobile than the 9-mm Luger. All GP 11 bullets and a large amount of the 9-mm Luger bullets exited the brain. Sliding toward the gantry was easier for 9-mm Luger bullets in the brain than in the liver. CONCLUSIONS: The orientation of a ferromagnetic object influences its mobility in a strong magnetic field. Tipping is easier than sliding for longish ferromagnetic projectiles, probably due to the lesser tissue resistance. The bullets moved more readily in biological tissue, especially brain tissue, compared to gelatine, thus implying that gelatine is not a suitable substitute for soft tissues when examining the movement of ferromagnetic objects in MR units.

Automatic entry point planning for robotic post-mortem CT-based needle placement.

INTRODUCTION: Post-mortem computed tomography guided placement of co-axial introducer needles allows for the extraction of tissue and liquid samples for histological and toxicological analyses. Automation of this process can increase the accuracy and speed of the needle placement, thereby making it more feasible for routine examinations. To speed up the planning process and increase safety, we developed an algorithm that calculates an optimal entry point and end-effector orientation for a given target point, while taking constraints such as accessibility or bone collisions into account. TECHNIQUE: The algorithm identifies the best entry point for needle trajectories in three steps. First, the source CT data is prepared and bone as well as surface data are extracted and optimized. All vertices of the generated surface polygon are considered to be potential entry points. Second, all surface points are tested for validity within the defined hard constraints (reachability, bone collision as well as collision with other needles) and removed if invalid. All remaining vertices are reachable entry points and are rated with respect to needle insertion angle. Third, the vertex with the highest rating is selected as the final entry point, and the best end-effector rotation is calculated to avoid collisions with the body and already set needles. DISCUSSION: In most cases, the algorithm is sufficiently fast with approximately 5-6 s per entry point. This is the case if there is no collision between the end-effector and the body. If the end-effector has to be rotated to avoid collision, calculation times can increase up to 24 s due to the inefficient collision detection used here. In conclusion, the algorithm allows for fast and facilitated trajectory planning in forensic imaging.

[Wound Ballistics ­ a Brief Overview]. / Wundballistik - eine Kurzübersicht.

Wound ballistics examines the specific effect, namely the wound profile, of bullets on the body by firing at synthetic models made of ordnance gelatine, glycerin soap and synthetic bones, validated with real cases from (battlefield) surgery and forensic pathology. Wound profile refers to the penetration depth, the bullet deformation/ fragmentation, the diameter of the permanent and the temporary wound cavity. Knowing these features and the used ammunition a surgeon can rapidly assess the amount damage within a patient. The forensic pathologist can draw conclusions as to the used ammunition based on the wound profile. By measuring of the destructive capability of different ammunition types, wound ballistics lays the foundation for guidelines concerning the maximum effect of military ammunition.

Development of CT-guided biopsy sampling for time-dependent postmortem redistribution investigations in blood and alternative matrices--proof of concept and application on two cases.

The postmortem redistribution (PMR) phenomenon complicates interpretation in forensic toxicology. Human data on time-dependent PMR are rare and only exist for blood so far. A new method for investigation of time-dependent PMR in blood as well as in alternative body fluids and tissues was developed and evaluated using automated biopsy sampling. At admission of the bodies, introducer needles were placed in liver, lung, kidney, muscle, spleen, adipose tissue, heart, femoral vein, and lumbar spine using a robotic arm guided by a computed tomography scanner (CT). Needle placement accuracy was analyzed and found to be acceptable for the study purpose. Tissue biopsies and small volume body fluid samples were collected in triplicate through the introducer needles. At autopsy (around 24 h after admission), samples from the same body regions were collected. After mastering of the technical challenges, two authentic cases were analyzed as a proof of concept. Drug concentrations of venlafaxine, O-desmethylvenlafaxine, bromazepam, flupentixol, paroxetine, and lorazepam were determined by LC-MS/MS, and the percentage concentration changes between the two time points were calculated. Concentration changes were observed with both increases and decreases depending on analyte and matrix. While venlafaxine, flupentixol, paroxetine, and lorazepam generally showed changes above 30% and more, O-desmethylvenlafaxine and bromazepam did not undergo extensive PMR. The presented study shows that CT-controlled biopsy collection provides a valuable tool for systematic time-dependent PMR investigation, demanding only minimal sample amount and causing minimal damage to the body.

The influence of 1.5 and 3 T magnetic resonance unit magnetic fields on the movement of steel-jacketed projectiles in ordnance gelatin.

PURPOSE: Ferromagnetic bullets can move in air or gelatin in magnetic resonance (MR) units. According to our experience, ferromagnetic bullets do not always present consistent movement. We examined factors affecting ferromagnetic projectile movement in a 1.5T and a 3T MR unit, focusing in this study on the steel-jacketed Swiss ordnance ammunition 7.5 mm GP11 Suisse. METHODS: Five 7.5 mm GP11 Suisse bullets were embedded horizontally and vertically in 10 % ordnance gelatin phantoms. Before and after exposing the bullets to 1.5T (Siemens) and 3T (Philips) MR units each bullet's position was documented by a CT scan. In a second phase, the magnetic polarization of the bullets in relation to the MR units was measured by a dry magnetic portable compass (Suunto). RESULTS: Our results showed that the displacement of the bullets increased when subjected to a stronger magnetic field (max. Movement 1.5T: 24.4 mm vs. 3T: 101.5 mm) and that the position, i.e. orientation of the bullet toward the gantry, strongly influenced its mobility (horizontally embedded projectiles showed poor movement, vertically placed ones strong movement). One of the bullets presented a 180° rotation in the 3T MR unit. Magnetization and changing of the polarization of these ferromagnetic bullets is possible when subjected to MR units. CONCLUSION: In conclusion, the location of a bullet, and its orientation toward the gantry must be taken into account when assessing the risk of performing an MR examination on a gunshot victim in clinical and in forensic cases.

Computer-assisted virtual autopsy using surgical navigation techniques.

UNLABELLED: OBJECTIVE; Virtual autopsy methods, such as postmortem CT and MRI, are increasingly being used in forensic medicine. Forensic investigators with little to no training in diagnostic radiology and medical laypeople such as state's attorneys often find it difficult to understand the anatomic orientation of axial postmortem CT images. We present a computer-assisted system that permits postmortem CT datasets to be quickly and intuitively resliced in real time at the body to narrow the gap between radiologic imaging and autopsy. CONCLUSION: Our system is a potentially valuable tool for planning autopsies, showing findings to medical laypeople, and teaching CT anatomy, thus further closing the gap between radiology and forensic pathology.

CT-guided, minimally invasive, postmortem needle biopsy using the B-Rob II needle-positioning robot.

CT-guided, minimally invasive needle biopsy techniques can be used to retrieve tissue or body fluid samples for histologic tissue diagnoses in forensic investigations. The purpose of this study was an evaluation of CT-guided needle-positioning robot B-Rob II. To operate under CT guidance, we adopted the B-Rob II robotic needle placement system and its workflow. The accuracy and speed of the procedure were tested on a gelatin phantom in a series of 21 biopsies. We achieved an average needle placement accuracy of 1.8 mm (±1.1 mm) using robotic assistance. The procedure required an average of 2 min 21 s. The needle placement accuracy for minimally invasive needle biopsies using the B-Rob II biopsy robot is sufficiently accurate and fast for forensic postmortem examinations of focal organ changes. Further tests will be performed to test the feasibility of the robot for performing biopsies of focal organ changes in human bodies.

Bone marrow edema induced by a bullet after a self-inflicted accidental firing.

We present a case of a postmortem finding of bone marrow edema in postmortem magnetic resonance imaging (PMMR) indirectly induced by a bullet, which barely missed the bone of a 92-year-old man found kneeling in front of his bed of a tidy apartment. Additionally, a selective postmortem computed tomography angiography (PMCTA) of the left leg was performed, visualizing a laceration of the left femoral vein by the bullet with consecutive contrast media extravasation. A vast pulmonary fat embolism was diagnosed and together with the blood loss found to be the cause of death.

Gas at postmortem computed tomography--an evaluation of 73 non-putrefied trauma and non-trauma cases.

Postmortem computed tomography (PMCT) has become an important complement in investigating forensic cases allowing an accurate detection of gas accumulations. The present study investigated the presence and distribution of gas in a large number of non-putrefied cases of traumatic and non-traumatic deaths. Furthermore the possibility of pneumobilia secondary to blunt abdominal trauma was studied. Retrospectively, 73 cases, underwent a whole-body PMCT prior to autopsy. These were divided into four groups: penetrating trauma (20 gunshot cases, 13 stabbing cases), blunt abdominal trauma (20 cases) and a control group of 20 non-trauma cases. Exclusion criteria were visible signs of decomposition. Each group was screened for gas accumulations in the vascular system, internal organs, soft tissues and body cavities. Gas accumulations were present in 98% of the trauma cases, compared to 80% of the control group. The most affected structures and/or organs in the trauma group were soft tissues, vessels and the liver. In most cases of the trauma group gas was associated with open injuries and lacerations of vessels. Furthermore, in the gunshot group gas was frequently seen in the intracranial cavity. Pneumobilia occurred in one case of the blunt trauma group; in that control group gas was also seen, but less frequently. Gas accumulation showed a strong association with traumatic events, but even the majority of non-trauma cases showed gas accumulations. Despite the exclusion of cases with visible decomposition signs, a putrefactive origin of gas was assumed in some cases. Gas accumulations are a frequent finding in PMCT with a higher incidence in (open) trauma cases. Even though a differentiation between putrefactive and traumatic gas accumulations is still difficult, knowledge of the circumstance surrounding the case may help identify the origin of gas.

Sudden death after chest pain: feasibility of virtual autopsy with postmortem CT angiography and biopsy.

PURPOSE: To determine the potential of minimally invasive postmortem computed tomographic (CT) angiography combined with image-guided tissue biopsy of the myocardium and lungs in decedents who were thought to have died of acute chest disease and to compare this method with conventional autopsy as the reference standard. MATERIALS AND METHODS: The responsible justice department and ethics committee approved this study. Twenty corpses (four female corpses and 16 male corpses; age range, 15-80 years), all of whom were reported to have had antemortem acute chest pain, were imaged with postmortem whole-body CT angiography and underwent standardized image-guided biopsy. The standard included three biopsies of the myocardium and a single biopsy of bilateral central lung tissue. Additional biopsies of pulmonary clots for differentiation of pulmonary embolism and postmortem organized thrombus were performed after initial analysis of the cross-sectional images. Subsequent traditional autopsy with sampling of histologic specimens was performed in all cases. Thereafter, conventional histologic and autopsy reports were compared with postmortem CT angiography and CT-guided biopsy findings. A Cohen κ coefficient analysis was performed to explore the effect of the clustered nature of the data. RESULTS: In 19 of the 20 cadavers, findings at postmortem CT angiography in combination with CT-guided biopsy validated the cause of death found at traditional autopsy. In one cadaver, early myocardial infarction of the papillary muscles had been missed. The Cohen κ coefficient was 0.94. There were four instances of pulmonary embolism, three aortic dissections (Stanford type A), three myocardial infarctions, three instances of fresh coronary thrombosis, three cases of obstructive coronary artery disease, one ruptured ulcer of the ascending aorta, one ruptured aneurysm of the right subclavian artery, one case of myocarditis, and one pulmonary malignancy with pulmonary artery erosion. In seven of 20 cadavers, CT-guided biopsy provided additional histopathologic information that substantiated the final diagnosis of the cause of death. CONCLUSION: Postmortem CT angiography combined with image-guided biopsy, because of their minimally invasive nature, have a potential role in the detection of the cause of death after acute chest pain.