Application of contrast media in post-mortem imaging (CT and MRI)

The effect of post-mortem computed tomography angiography (PMCTA) on biomarkers of coronary artery disease

Coronary atherosclerosis is due to build-up of plaque within the coronary arteries. Post-mortem computed tomography (PMCT) allows non or minimally invasive visualization of abnormalities prior to an autopsy, however PMCT-angiography (PMCTA) greatly enhances relevant findings, especially in viewing the cardiovascular system which is important in the diagnosis of coronary atherosclerosis. Contrast media used in PMCTA however has been reported to cause distortion of tissue which may interfere with post-mortem investigation outcomes. A cross sectional study to investigate the effect of PMCTA on tissue biomarkers in coronary arteries was performed involving cases brought in dead to the Institute and Accident and Emergency Unit. Sixty-three autopsy cases were included in this study, whereby 18 cases underwent PMCT while 45 cases underwent PMCTA. The subjects subsequently had a conventional autopsy where coronary artery sections were collected for standard histological examination and immunohistochemistry examination for endothelial inflammatory (CD36), prothrombogenic (TPA) and plaque stability (MMP-9) markers. The subjects consisted of 55 males and 8 females with a mean age ±SD of 49 ± 18.11 years. There were no significant differences in the coronary artery endothelial expression of CD36, MMP-9 and TPA between PMCT and PMCTA subjects. PMCTA does not alter CD36, TPA and MMP-9 markers supporting the safe use of PMCTA in post-mortem examinations.

Diagnostic accuracy of coronary artery stenosis and thrombosis assessment using unenhanced multiplanar 3D post-mortem cardiac magnetic resonance imaging

BACKGROUND

A 3D sequence was introduced to unenhanced post-mortem cardiac magnetic resonance imaging (PMCMR) to enable multiplanar coronary artery image analysis and to investigate its diagnostic accuracy for the diagnosis of coronary artery stenosis and thrombosis.

MATERIALS AND METHODS

N = 200 forensic cases with suspected coronary artery pathology underwent 3 Tesla PMCMR (sequence used: T2 weighted transversal 3D turbo spin echo) before autopsy. Main coronary artery stenosis and thrombosis were assessed in PMCMR by multiplanar image analysis by two observers. Coronary artery histology was determined as the gold standard and compared to PMCMR. Sensitivity, specificity, negative (NPV) and positive predictive values (PPV) with 95% confidence intervals were calculated.

RESULTS

For all coronary arteries combined, sensitivity was 75% (PPV 73%) for the diagnosis of stenosis and 72% (PPV 71%) for the diagnosis of thrombosis. Specificity was 92% (NPV 90%) for correct diagnosis of non-existing stenosis and 97% (NPV 97%) for non-existing thrombosis. Sensitivity for correct diagnosis of different degrees of stenosis ranged between 67% and 80% (PPVs 67-82%); specificity ranged between 96% and 99% (NPVs 96-99%).

CONCLUSION

Multiplanar PMCMR coronary artery stenosis and thrombosis assessment based on an unenhanced T2 weighted 3D sequence provide moderate sensitivity and high specificity for the diagnosis of coronary artery stenosis and/or thrombosis. Hence, 3D T2w PMCMR cannot reliably detect existing coronary artery stenosis and thrombosis but may be particularly useful for the exclusion of stenosis or thrombosis of the main coronary arteries.

Application of postmortem computed tomography angiography to settle a medical dispute after aortic dissection surgery: a forensic case report

BACKGROUND

In the present case, we applied postmortem computed tomography angiography (PMCTA) in a medical dispute involving sudden death after cardiovascular surgery.

CASE PRESENTATION

A 39-year-old man underwent aortic arch replacement combined with stented elephant trunk implantation surgery under extracorporeal circulation. All vital signs were stable and he was arranged for discharge seven days after surgery. Several days later, the patient was sent back to the hospital for chest pain and poor appetite. Unfortunately, his condition worsened and he ultimately died. PMCT scanning detect pericardial effusion. Family members suspected that the surgical sutures were not dense enough, causing the patient's postoperative bleeding and resulting in cardiac tamponade and death. PMCTA was performed before autopsy, which showed pericardial effusion. However, postmortem angiography with simulated blood pressure showed no leakage of contrast agent, which guided the subsequent autopsy and histological examinations.

CONCLUSIONS

While many previous postmortem imaging case reports have shown positive results that provided evidence of medical malpractice, the current case excludes the possibility of physician negligence and reasonably settles the medical dispute from another perspective. In short, the PMCTA approach we describe here was an effective tool that can be applied to certain medical-related forensic cases.

Clinical Anatomy and Medical Malpractice-A Narrative Review with Methodological Implications

Anatomical issues are intrinsically included in medico-legal methodology, however, higher awareness would be needed about the relevance of anatomy in addressing medico-legal questions in clinical/surgical contexts. Forensic Clinical Anatomy has been defined as "the practical application of Clinical Anatomy to the ascertainment and evaluation of medico-legal problems". The so-called individual anatomy (normal anatomy, anatomical variations, or anatomical modifications due to development, aging, para-physiological conditions, diseases, or surgery) may acquire specific relevance in medico-legal ascertainment and evaluation of cases of supposed medical malpractice. Here, we reviewed the literature on the relationships between anatomy, clinics/surgery, and legal medicine. Some methodological considerations were also proposed concerning the following issues: (1) relevant aspects of individual anatomy may arise from the application of methods of ascertainment, and they may be furtherly ascertained through specific anatomical methodology; (2) data about individual anatomy may help in the objective application of the criteria of evaluation (physio-pathological pathway, identification-evaluation of errors, causal value, damage estimation) and in final judgment about medical responsibility/liability. Awareness of the relevance of individual anatomy (risk of iatrogenic lesions, need for preoperative diagnostic procedures) should be one of the principles guiding the clinician; medico-legal analyses can also take advantage of its contribution in terms of ascertainment/evaluation.

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.

Magnetism of materials: theory and practice in magnetic resonance imaging

All substances exert magnetic properties in some extent when placed in an external magnetic field. Magnetic susceptibility represents a measure of the magnitude of magnetization of a certain substance when the external magnetic field is applied. Depending on the tendency to be repelled or attracted by the magnetic field and in the latter case on the magnitude of this effect, materials can be classified as diamagnetic or paramagnetic, superparamagnetic and ferromagnetic, respectively. Knowledge of type and extent of susceptibility of common endogenous and exogenous substances and how their magnetic properties affect the conventional sequences used in magnetic resonance imaging (MRI) can help recognize them and exalt or minimize their presence in the acquired images, so as to improve diagnosis in a wide variety of benign and malignant diseases. Furthermore, in the context of diamagnetic susceptibility, chemical shift imaging enables to assess the intra-voxel ratio between water and fat content, analyzing the tissue composition of various organs and allowing a precise fat quantification. The following article reviews the fundamental physical principles of magnetic susceptibility and examines the magnetic properties of the principal endogenous and exogenous substances of interest in MRI, providing potential through representative cases for improved diagnosis in daily clinical routine.

3Tesla post-mortem MRI quantification of anatomical brain structures

Quantitative post-mortem magnetic resonance imaging (PMMR) allows for measurement of T1 and T2 relaxation times and proton density (PD) of brain tissue. Quantitative PMMR values may be used for advanced post-mortem neuro-imaging diagnostics such as computer aided diagnosis. So far, the quantitative T1, T2 and PD post-mortem values of regular anatomical brain structures were unknown for a 3 Tesla PMMR application. The goal of this basic research study was to evaluate the quantitative values of post-mortem brain structures for a 3 T post-mortem magnetic resonance application with regard to various corpse temperatures. In 50 forensic cases, a quantitative PMMR brain sequence was applied prior to autopsy. Measurements of T1 (in ms), T2 (in ms), and PD (in %) values of cerebrum (Group 1: frontal grey matter, frontal white matter, thalamus, caudate nucleus, globus pallidus, putamen, internal capsule) brainstem and cerebellum (Group 2: cerebral peduncle, substantia nigra, red nucleus, pons, middle cerebellar peduncle, cerebellar hemisphere, medulla oblongata) were conducted in synthetically calculated axial PMMR brain images. Assessed quantitative values were corrected for corpse temperature. Temperature dependence was observed mainly for T1 values. ANOVA testing resulted in significant differences of quantitative values between the investigated anatomical brain structures in both groups. It can be concluded that temperature corrected 3 Tesla PMMR T1, T2 and PD values are feasible for characterization and discrimination of regular anatomical brain structures. This may provide a base for future advanced diagnostics of forensically relevant brain lesions and pathology.

Rupture of the Ascending Aorta Surgical Area Detected Using Isolated Cardiopulmonary Organ Computed Tomography Angiography: An Autopsy Case Report After Cardiac Surgery

ABSTRACT

We report cause of death after cardiac surgery using isolated cardiopulmonary organ computed tomography angiography (CTA) and a conventional autopsy. A 56-year-old man underwent aortic valve replacement and coronary artery bypass graft surgery under extracorporeal circulation. Massive bleeding occurred suddenly, and the patient died 25 days later. An autopsy revealed fibrinous exudate in the mediastinum and tight attachment of the pericardium to the heart; there were also clots and inflammatory exudate in the chest cavity. Separating the organs in the chest cavity was difficult, especially in the surgical area. We extracted the heart and lungs together and performed cardiovascular CTA and image reconstruction. Results showed spillage of the contrast agent from the anterior wall of the ascending aorta, approximately 4.5 cm from the replaced aortic valve. A histological examination confirmed that the site of contrast agent spillage was the sutured area of the ascending aorta, which was infected, necrotic, and had ruptured. Using the CTA approach for isolated cardiopulmonary organ imaging can accurately display the location of an aortic rupture, which further guides organ inspection and tissue sampling, and avoids irreversible damage to key regions. In conclusion, the approach we describe can provide evidence for determining cause of death.

Threshold-dependent iodine imaging and spectral separation in a whole-body photon-counting CT system

OBJECTIVE

To evaluate the dual-energy (DE) performance and spectral separation with respect to iodine imaging in a photon-counting CT (PCCT) and compare it to dual-source CT (DSCT) DE imaging.

METHODS

A semi-anthropomorphic phantom extendable with fat rings equipped with iodine vials is measured in an experimental PCCT. The system comprises a PC detector with two energy bins (20 keV, T) and (T, eU) with threshold T and tube voltage U. Measurements using the PCCT are performed at all available tube voltages (80 to 140 kV) and threshold settings (50-90 keV). Further measurements are performed using a conventional energy-integrating DSCT. Spectral separation is quantified as the relative contrast media ratio R between the energy bins and low/high images. Image noise and dose-normalized contrast-to-noise ratio (CNRD) are evaluated in resulting iodine images. All results are validated in a post-mortem angiography study.

RESULTS

R of the PC detector varies between 1.2 and 2.6 and increases with higher thresholds and higher tube voltage. Reference R of the EI DSCT is found as 2.20 on average overall phantoms. Maximum CNRD in iodine images is found for T = 60/65/70/70 keV for 80/100/120/140 kV. The highest CNRD of the PCCT is obtained using 140 kV and is decreasing with decreasing tube voltage. All results could be confirmed in the post-mortem angiography study.

CONCLUSION

Intrinsically acquired DE data are able to provide iodine images similar to conventional DSCT. However, PCCT thresholds should be chosen with respect to tube voltage to maximize image quality in retrospectively derived image sets.

KEY POINTS

• Photon-counting CT allows for the computation of iodine images with similar quality compared to conventional dual-source dual-energy CT. • Thresholds should be chosen as a function of the tube voltage to maximize iodine contrast-to-noise ratio in derived image sets. • Image quality of retrospectively computed image sets can be maximized using optimized threshold settings.

Longitudinal comparison of ascites attenuation between antemortem and postmortem computed tomography

OBJECTIVE

To investigate the changes in ascites attenuation between antemortem (AMCT) and postmortem computed tomography (PMCT) analyses of the same subjects.

METHODS

Thirty-five subjects who underwent unenhanced or enhanced AMCT within 7 days before death, unenhanced PMCT, and autopsy were evaluated. In each subject, ascites attenuation was measured at similar sites on AMCT and PMCT. Attenuation changes were evaluated in 42 unenhanced AMCT/PMCT site pairs (23 subjects) and 20 enhanced AMCT/PMCT site pairs (12 subjects). Factors contributing to CT attenuation changes were also assessed, including the time interval between AMCT and PMCT, serum albumin level, estimated glomerular filtration rate, and ascites volume.

RESULTS

Significantly elevated CT attenuation was observed between enhanced AMCT and PMCT (12.2 ± 6.3 vs. 18.7 ± 10.4 Hounsfield units; paired t-test, p = 0.006), but not between unenhanced AMCT and PMCT (13.5 ± 8.9 vs. 13.4 ± 9.3; p = 0.554). A significant inverse association was observed between the degree of CT attenuation change and the time interval between enhanced AMCT and PMCT (Spearman's rank correlation coefficient, r = -0.56, p = 0.01).

CONCLUSIONS

We confirmed an elevated level of ascites attenuation on PMCT relative to AMCT in subjects who underwent enhanced AMCT shortly before death.

A comparison on the detection accuracy of ante mortem computed tomography vs. autopsy for the diagnosis of pelvic ring injury in legal medicine

A detailed knowledge on the exact morphology of pelvic injuries provided crucial information in understanding the mechanisms of injury and has influence on the natural course and subsequent mortality. However, forensic medical literature investigating pelvic fractures in detail is scarce to date. This case series aims to compare the accuracy in detecting pelvic injuries using autopsy and ante mortem computed tomography (CT). Nineteen deceased patients with CT scans of pelvic fractures were included retrospectively. Pelvic injuries were independently assessed by a board-certified radiologist (R) and a board-certified trauma surgeon (T), both using the ante mortem CT scans, and by a board-certified forensic pathologist using autopsy (A) results without knowledge of the CT scan findings. No patient had died causatively from a pelvic fracture. Most injuries of the pelvis were present in the pubic rami (16/18) and sacral bone (13/18), followed by the sacroiliac joint (9/18) and iliac bone fractures (8/18). Ilium fractures (A:100%;R:67%;T:67%) and injuries of the sacroiliac joint (A:83%;R:50%;T:42%) were best detected via autopsy. The diagnosis of sacral fractures (A:19%;R:94%;T:88%) and fractures of the pubic rami (A:67%;R:96%;T:96%) were most often missed in autopsy. The results show deficits in the assessment of the pelvic injury for both CT and autopsy. Autopsy was superior in detecting injuries of the sacroiliac joint, but inferior in detecting sacral and pubic bone fractures. For an encompassing evaluation of ligamento-skeletal pelvic injuries, the complementary use of both CT and autopsy is recommended.

Postmortem imaging as a complementary tool for the investigation of cardiac death

In the past 2 decades, modern radiological methods, such as multiple detector computed tomography (MDCT), MDCT-angiography, and cardiac magnetic resonance imaging (MRI) were introduced into postmortem practice for investigation of sudden death (SD), including cases of sudden cardiac death (SCD). In forensic cases, the underlying cause of SD is most frequently cardiovascular with coronary atherosclerotic disease as the leading cause. There are many controversies about the role of postmortem imaging in establishing the cause of death and especially the value of minimally invasive autopsy techniques. This paper discusses the state of the art for postmortem radiological evaluation of the heart compared to classical postmortem examination, especially in cases of SCD. In SCD cases, postmortem CT is helpful to estimate the heart size and to visualize haemopericardium and calcified plaques and valves, as well as to identify and locate cardiovascular devices. Angiographic methods are useful to provide a detailed view of the coronary arteries and to analyse them, especially regarding the extent and location of stenosis and obstruction. In postsurgical cases, it allows verification and documentation of the patency of stents and bypass grafts before opening the body. Postmortem MRI is used to investigate soft tissues such as the myocardium, but images are susceptible to postmortem changes and further work is necessary to increase the understanding of these radiological aspects, especially of the ischemic myocardium. In postsurgery cases, the value of postmortem imaging of the heart is reportedly for the diagnostic and documentation purposes. The implementation of new imaging methods into routine postmortem practice is challenging, as it requires not only an investment in equipment but, more importantly, investment in the expertise of interpreting the images. Once those requirements are implemented, however, they bring great advantages in investigating cases of SCD, as they allow documentation of the body, orientation of sampling for further analyses and gathering of other information that cannot be obtained by conventional autopsy such as a complete visualization of the vascular system using postmortem angiography.Key pointsThere are no established guidelines for the interpretation of postmortem imaging examination of the heartAt present, postmortem imaging methods are considered as less accurate than the autopsy for cardiac deathsPostmortem imaging is useful as a complementary tool for cardiac deathsThere is still a need to validate postmortem imaging in cardiac deaths by comparing with autopsy findings.

Diagnostic Accuracy of Postmortem CT of Children: A Retrospective Single-Center Study

OBJECTIVE. The objective of our study was to determine the diagnostic accuracy of postmortem CT in children compared with standard autopsy. MATERIALS AND METHODS. This single-center retrospective study reviewed un-enhanced whole-body postmortem CT examinations of children less than 16 years old with corresponding autopsy reports irrespective of the clinical indication for referral for postmortem CT. Perinatal deaths were excluded. Postmortem CT was reported by experienced postmortem radiologists who were blinded to autopsy findings, with the primary outcome being concordance for the main pathologic diagnosis or findings leading to a cause of death. Autopsy performed by pediatric pathologists was the reference standard. RESULTS. One hundred thirty-six patients (74 [54.4%] male and 62 [45.6%] female patients) were included. The mean age of the 136 patients was 2 years 1 month (range, 2 days-14.7 years). A cause of death at autopsy was found for 77 of the 136 (56.6%) patients. Postmortem CT depicted a correct cause of death in 55 of 77 (71.4%) patients; (55/136 overall [40.4%]), with the majority attributable to traumatic brain or body injuries. For major pathologic findings, diagnostic accuracy rates were a sensitivity of 71.4% (95% CI, 60.5-80.3%), specificity of 81.4% (95% CI, 69.6-89.3%), positive predictive value of 83.3% (95% CI, 72.6-90.4%), negative predictive value of 68.6% (95% CI, 57.0-78.2%), and concordance rate of 75.7% (95% CI, 67.9-82.2%). The sensitivity of postmortem CT versus autopsy was highest for intracranial (75.6%; 95% CI, 60.7-86.2%) and musculoskeletal (98.4%; 95% CI, 91.4-99.7%) abnormalities and lowest for cardiac (31.3%; 95% CI, 14.2-55.6%) and abdominal (53.8%; 95% CI, 29.1-78.6%) findings. CONCLUSION. Postmortem CT gives an acceptable diagnostic concordance rate with autopsy of 71.4%, although identification of the cause of death overall was low at 40.4%. The highest accuracy rates were for intracranial and musculoskeletal abnormalities.

State of the art in post-mortem computed tomography: a review of current literature

Computed tomography (CT) and other advanced diagnostic imaging techniques are gaining popularity in forensic pathology. This paper aims to define and offer complete and easily accessible "state of the art" for post-mortem computed tomography (PMCT), by reviewing the latest international literature. The proposed format answers the "five Ws" that follows: (1) What: We report the different kinds of CT scan and settings generally used in post-mortem imaging. The machine most employed is a 8/16-slice spiral CT, usually without contrast enhancement. The introduction of some variables, such as CT-guided biopsies, post-mortem ventilation, and PMCT angiography is becoming increasingly useful. (2) Why: Literature highlights the many advantages of PMCT. Limitations can be partly overcome by modern imaging techniques and combined evaluation with traditional autopsy. (3) Who: Most authors agree that collaboration between different specialists, i.e., radiologists and pathologists, is the best scenario, since radiologic, anatomic, and forensic skills are needed simultaneously. The most important human factor is "teamwork". (4) When: Literature provides no absolute limits for performing PMCT. Some authors have tested PMCT as a replacement for conventional autopsy but found some limitations. Others evaluated PMCT as a guide or screening tool for traditional autopsy. (5) Where: Many research groups around the world have performed studies on the use of PMCT. Although few countries adopt PMCT in routine practice, its use is rapidly spreading.

Diagnostic accuracy of postmortem computed tomography, magnetic resonance imaging, and computed tomography-guided biopsies for the detection of ischaemic heart disease in a hospital setting

Aims

The autopsy rate worldwide is alarmingly low (0-15%). Mortality statistics are important, and it is, therefore, essential to perform autopsies in a sufficient proportion of deaths. The imaging autopsy, non-invasive, or minimally invasive autopsy (MIA) can be used as an alternative to the conventional autopsy in an attempt to improve postmortem diagnostics by increasing the number of postmortem procedures. The aim of this study was to determine the diagnostic accuracy of postmortem magnetic resonance imaging (MRI), computed tomography (CT), and CT-guided biopsy for the detection of acute and chronic myocardial ischaemia.

Methods and results

We included 100 consecutive adult patients who died in hospital, and for whom next-of-kin gave permission to perform both conventional autopsy and MIA. The MIA consists of unenhanced total-body MRI and CT followed by CT-guided biopsies. Conventional autopsy was used as reference standard. We calculated sensitivity and specificity and receiver operating characteristics curves for CT and MRI as the stand-alone test or combined with biopsy for detection of acute and chronic myocardial infarction (MI). Sensitivity and specificity of MRI with biopsies for acute MI was 0.97 and 0.95, respectively and 0.90 and 0.75, respectively for chronic MI. MRI without biopsies showed a high specificity (acute: 0.92; chronic: 1.00), but low sensitivity (acute: 0.50; chronic: 0.35). CT (total Agatston calcium score) had a good diagnostic value for chronic MI [area under curve (AUC) 0.74, 95% confidence interval (CI) 0.64-0.84], but not for acute MI (AUC 0.60, 95% CI 0.48-0.72).

Conclusion

We found that the combination of MRI with biopsies had high sensitivity and specificity for the detection of acute and chronic myocardial ischaemia.

An exploratory study toward the contribution of 3D surface scanning for association of an injury with its causing instrument

3D surface scanning is a technique brought forward for wound documentation and analysis in order to identify injury-causing tools in legal medicine and forensic science. Although many case reports have been published, little is known about the methodology employed by the authors. The study reported here is exploratory in nature, and its main purpose was to get a first evaluation of the ability of an operator, by means of 3D surface scanning and following a simple methodology, to correctly exclude or associate an incriminated tool as the source of a mock wound. Based on these results, an assessment of the possibility to define a structured methodology that could be suitable for this use was proposed. Blunt tools were used to produce 'wounds' on watermelons. Both wounds and tools were scanned with a non-contact optical surface 3D digitising system. Analysis of the obtained 3D models of wounds and tools was undertaken separately. This analytical phase was followed by a qualitative and a quantitative comparison. Results showed that in more than half of the cases, we obtained a correct association but the prevalence of wrong association was still high due to mark deformation and other limitations. Even if the findings of this exploratory study cannot be generalised, they suggest that the simple and direct comparison process is not reliable enough for a systematic routine application. The article highlights the importance of an analysis phase preceding the comparison step. Limitations of the technique, ensuring needs and possible paths for improvement are also expounded.

Postmortem CT Angiography Compared with Autopsy: A Forensic Multicenter Study

Purpose

To determine if postmortem computed tomography (CT) and postmortem CT angiography help to detect more lesions than autopsy in postmortem examinations, to evaluate the strengths and weaknesses of each method, and to define their indications.

Materials and Methods

Postmortem CT angiography was performed on 500 human corpses and followed by conventional autopsy. Nine centers were involved. All CT images were read by an experienced team including one forensic pathologist and one radiologist, blinded to the autopsy results. All findings were recorded for each method and categorized by anatomic structure (bone, organ parenchyma, soft tissue, and vascular) and relative importance in the forensic case (essential, useful, and unimportant).

Results

Among 18 654 findings, autopsies helped to identify 61.3% (11 433 of 18 654), postmortem CT helped to identify 76.0% (14 179 of 18 654), and postmortem CT angiography helped to identify 89.9% (16 780 of 18 654; P < .001). Postmortem CT angiography was superior to autopsy, especially at helping to identify essential skeletal lesions (96.1% [625 of 650] vs 65.4% [425 of 650], respectively; P < .001) and vascular lesions (93.5% [938 of 1003] vs 65.3% [655 of 1003], respectively; P < .001). Among the forensically essential findings, 23.4% (1029 of 4393) were not detected at autopsy, while only 9.7% (428 of 4393) were missed at postmortem CT angiography (P < .001). The best results were obtained when postmortem CT angiography was combined with autopsy.

Conclusion

Postmortem CT and postmortem CT angiography and autopsy each detect important lesions not detected by the other method. More lesions were identified by combining postmortem CT angiography and autopsy, which may increase the quality of postmortem diagnosis.

Online supplemental material is available for this article.

Can virtual autopsy with postmortem CT improve clinical diagnosis of cause of death? A retrospective observational cohort study in a Dutch tertiary referral centre

OBJECTIVE

To investigate whether virtual autopsy with postmortem CT (PMCT) improves clinical diagnosis of the immediate cause of death.

DESIGN

Retrospective observational cohort study.

INCLUSION CRITERIA

inhospital and out-of-hospital deaths over the age of 1 year in whom virtual autopsy with PMCT and conventional autopsy were performed.

EXCLUSION CRITERIA

forensic cases, postmortal organ donors and cases with incomplete scanning procedures. Cadavers were examined by virtual autopsy with PMCT prior to conventional autopsy. The clinically determined cause of death was recorded before virtual autopsy and was then adjusted with the findings of virtual autopsy. Using conventional autopsy as reference standard, we investigated the increase in sensitivity for immediate cause of death, type of pathology and anatomical system involved before and after virtual autopsy.

SETTING

Tertiary referral centre.

PARTICIPANTS

86 cadavers that underwent conventional and virtual autopsy between July 2012 and June 2016.

INTERVENTION

PMCT consisted of brain, cervical spine and chest-abdomen-pelvis imaging. Conventional autopsy consisted of thoracoabdominal examination with/without brain autopsy.

PRIMARY AND SECONDARY OUTCOME MEASURES

Increase in sensitivity for the immediate cause of death, type of pathology (infection, haemorrhage, perfusion disorder, other or not assigned) and anatomical system (pulmonary, cardiovascular, gastrointestinal, other or not assigned) involved, before and after virtual autopsy.

RESULTS

Using PMCT, the sensitivity for immediate cause of death increased with 12% (95% CI 2% to 22%) from 53% (41% to 64%) to 64% (53% to 75%), with 18% (9% to 27%) from 65% (54% to 76%) to 83% (73% to 91%) for type of pathology and with 19% (9% to 30%) from 65% (54% to 76%) to 85% (75% to 92%) for anatomical system.

CONCLUSION

While unenhanced PMCT is an insufficient substitute for conventional autopsy, it can improve diagnosis of cause of death over clinical diagnosis alone and should therefore be considered whenever autopsy is not performed.

Post-mortem MR angiography: quantitative investigation and intravascular retention of perfusates in ex situ porcine hearts

As the implementation of minimally invasive imaging techniques in both forensic and pathological practice increases, research in this area focuses on addressing recognised diagnostic weaknesses of current approaches. Assessment of sudden cardiac death (SCD) can be considered one such area in which post-mortem imaging still shows diagnostic weaknesses. We hypothesise that magnetic resonance imaging (MRI) with an angiographic adjunct may improve the visualisation and interpretation of cardiac pathologies in a post-mortem setting. To systematically investigate this hypothesis, selected perfusates (paraffin oil, Gadovist®;-doped physiological solution and polyethylene glycol (PEG)) were injected into the left anterior descending (LAD) artery of ex situ porcine hearts to assess the visualisation of perfusates in MRI as well as their intravascular retention over 12 h. Morphological images were acquired and quantitative T₁ maps were generated from inversion recovery data. Visualisation of vascular structure and image quality were assessed using signal-to-noise and contrast-to-noise ratios. Intravascular retention was assessed both visually and statistically using a volume of interest (VOI) approach to analyse significant changes in signal intensity in and around the filled LAD artery, as well as changes in the longitudinal relaxation time (T₁) in adjacent myocardium. In addition to presenting possible mechanisms explaining perfusate extravasation given the increased permeability of post-mortem vessels, the potential diagnostic consequences of this phenomenon and the importance of contrast stability and extended intravascular retention are discussed. In light of our findings and these considerations, paraffin oil emerged as the preferred perfusate for use in post-mortem MR angiography.

A Comprehensive Review of Medical Imaging Equipment Used in Cadaveric Studies

Medical imaging techniques have led to great advances in clinical anatomy and forensic pathology. New and emerging technologies allow healthcare professionals to view and understand the human body from different perspectives. This gives way to new and improved interventions, treatment plans, and an overall understanding of the human body. Herein, we present a comprehensive review of the various medical imaging equipment used in cadaveric studies along with their individual strengths and limitations.

A guide for effective anatomical vascularization studies: useful ex vivo methods for both CT and MRI imaging before dissection

The objective of this study was to develop a simple and useful injection protocol for imaging cadaveric vascularization and dissection. Mixtures of contrast agent and cast product should provide adequate contrast for two types of ex vivo imaging (MRI and CT) and should harden to allow gross dissection of the injected structures. We tested the most popular contrast agents and cast products, and selected the optimal mixture composition based on their availability and ease of use. All mixtures were first tested in vitro to adjust dilution parameters of each contrast agent and to fine-tune MR imaging acquisition sequences. Mixtures were then injected in 24 pig livers and one human pancreas for MR and computed tomography (CT) imaging before anatomical dissection. Colorized latex, gadobutrol and barite mixture met the above objective. Mixtures composed of copper sulfate (CuSO₄ ) gadoxetic acid (for MRI) and iodine (for CT) gave an inhomogeneous signal or extravasation of the contrast agent. Agar did not harden sufficiently for gross dissection but appears useful for CT and magnetic resonance imaging (MRI) studies without dissection. Silicone was very hard to inject but achieved the goals of the study. Resin is particularly difficult to use but could replace latex as an alternative for corrosion instead of dissection. This injection protocol allows CT and MRI images to be obtained of cadaveric vascularization and anatomical casts in the same anatomic specimen. Post-imaging processing software allow easy 3D reconstruction of complex anatomical structures using this technique. Applications are numerous, e.g. surgical training, teaching methods, postmortem anatomic studies, pathologic studies, and forensic diagnoses.

The role of angiography in the congruence of cardiovascular measurements between autopsy and postmortem imaging

INTRODUCTION

Postmortem CT angiography is the method of choice for the postmortem imaging investigations of the cardiovascular (CV) system. However, autopsy still remains the gold standard for CV measurement. Nevertheless, there are not any studies on CV measurements on the multi-phase postmortem angiography (MPMCTA) which includes comparisons with autopsy. Therefore, the aim of this study is to compare CV measurements between the native CT scan and the three phases of the MPMCTA to find out which of these modalities correlate the best with autopsy measurements.

METHODS

For this study, we selected retrospectively 50 postmortem cases that underwent both MPMCTA and autopsy. A comparison was carried out between the CV measurements obtained with imaging (aorta; heart cavities and cardiac wall thicknesses; maximum cardiac diameter and cardiothoracic ratio) and at the autopsy (aorta; cardiac valves, ventricular thicknesses, and weight).

RESULTS

Our results show that the dynamic phase displays an advantage for the measurement of the aortas. However, the MPMCTA is not accurate to measure the cardiac wall thicknesses. The measurements of the heart cavities show no correlation with the heart valves. The cardiothoracic ratio measured by the MPMCTA shows no correlation with the heart weight. Nevertheless, the maximum cardiac diameter exhibits a correlation with the latter on the venous and dynamic phase.

CONCLUSIONS

These results show that only few CV parameters measured with imaging correlate with measurement obtained at the autopsy. These results indicate that in order to better estimate values obtained at the autopsy, we need to define new reference values for the CV measurement on MPMCTA.

State of the art in post-mortem forensic imaging in China

The autopsy and histopathologic examination are traditional and classic approaches in forensic pathology. In recent years, with the tremendous progresses of computer technology and medical imaging technology, the developed post-mortem computer tomography, post-mortem magnetic resonance imaging and other new methods provide non-invasive, intuitive, high-precision examining methods and research tools for the forensic pathology. As a result, the reconstruction of the injury as well as the analysis of injury mechanism has been essentially achieved. Such methods have become popular in the research field of forensic science and related work has also been carried out in China. This paper reviews the development and application of abovementioned post-mortem forensic imaging methods in China based on the relevant literature.

CT-scan vs. 3D surface scanning of a skull: first considerations regarding reproducibility issues

Three-dimensional surface scanning (3DSS) and multi-detector computed tomography (MDCT) are two techniques that are used in legal medicine for digitalizing objects, a body or body parts such as bones. While these techniques are more and more commonly employed, surprisingly little information is known about the quality rendering of digitalized three-dimensional (3D) models provided by each of them. This paper presents findings related to the measurement precision of 3D models obtained through observation of a study case, where a fractured skull reconstructed by an anthropologist was digitalized using both post-mortem imaging methods. Computed tomography (CT) scans were performed using an 8-row MDCT unit with two different slice thicknesses. The variability of 3D CT models superimposition allowed to assess the reproducibility and robustness of this digitalization technique. Furthermore, two 3D surface scans were done using a professional high resolution 3D digitizer. The comparison of 3D CT-scans with 3D surface scans by superimposition demonstrated several regions with significant differences in topology (average difference between +1.45 and -1.22 mm). When comparing the reproducibility between these two digitalizing techniques, it appeared that MDCT 3D models led in general to greater variability for measurement precision between scanned surfaces. Also, the reproducibility was better achieved with the 3D surface digitizer, showing 3D models with fewer and less pronounced differences (from +0.32 to -0.31 mm). These experiments suggest that MDCT provides less reproducible body models than 3D surface scanning. But further studies must be undertaken in order to corroborate this first impression, and possibly explain the reason for these findings.

Modern post-mortem imaging: an update on recent developments

Modern post-mortem investigations use an increasing number of digital imaging methods, which can be collected under the term "post-mortem imaging". Most methods of forensic imaging are from the radiology field and are therefore techniques that show the interior of the body with technologies such as X-ray or magnetic resonance imaging. To digitally image the surface of the body, other techniques are regularly applied, e.g. three-dimensional (3D) surface scanning (3DSS) or photogrammetry. Today's most frequently used techniques include post-mortem computed tomography (PMCT), post-mortem magnetic resonance imaging (PMMR), post-mortem computed tomographic angiography (PMCTA) and 3DSS or photogrammetry. Each of these methods has specific advantages and limitations. Therefore, the indications for using each method are different. While PMCT gives a rapid overview of the interior of the body and depicts the skeletal system and radiopaque foreign bodies, PMMR allows investigation of soft tissues and parenchymal organs. PMCTA is the method of choice for viewing the vascular system and detecting sources of bleeding. However, none of those radiological methods allow a detailed digital view of the body's surface, which makes 3DSS the best choice for such a purpose. If 3D surface scanners are not available, photogrammetry is an alternative. This review article gives an overview of different imaging techniques and explains their applications, advantages and limitations. We hope it will improve understanding of the methods.

A fatal case of oxygen embolism in a hospital

This case reports on a 68-year-old man who was found dead in hospital next to his bed. Before this, he had been treated with intravenous antibiotics for pneumonia. The body was found with a peripheral venous catheter connected to a nasal cannula delivering oxygen (O₂) from the wall.

Extensive medico–legal examinations were performed, including post-mortem computed tomography (CT), complete conventional autopsy, histological and immunohistochemistry analysis, toxicological analysis and post-mortem chemistry. Additionally, CT-guided gas sampling was performed at multiple sites to collect samples for gas analysis.

During the external examination, massive subcutaneous emphysema was visible over the entire surface of the body. The CT scan revealed the presence of gas throughout the vascular system, and in the subcutaneous and muscular tissues. The autopsy confirmed the presence of lobar pneumonia and multiple gas bubbles in the vascular system.

The gas analysis results showed a subnormal concentration of oxygen, confirming the suspected pure O₂ embolism. Moreover, the carbon dioxide (CO₂) concentration in the gas sample from the heart was elevated to a level similar to those found in scuba diving fatalities. This could come from degassing of dissolved CO₂ that accumulated and was trapped in the cardiac cavity. Based on the results of the different exams performed, and especially the gas analysis results, it was concluded that the cause of death was O₂ embolism.

The effect of post-mortem computed tomography angiography (PMCTA) using water-soluble, iodine-based radiographic contrast on histological analysis of the liver, kidneys and left ventricle of the heart

The purpose of this study was to investigate the impact of post-mortem computed-tomography angiography (PMCTA) on the histology of the liver, kidneys and heart. Multiple tissue cores were collected from the liver, left and right kidneys and left ventricle utilizing CT-guided biopsy. Subsequent whole body PMCTA was performed using a solution of polyethylene glycol and iodinated radiographic contrast, and an embalming pump. Corresponding biopsy cores were collected at autopsy, and blinded histology analysis assessing for PMCTA-induced histology artefact was performed. The blinded analysis of pre-PMCTA and post-PMCTA biopsy samples demonstrated that whole body PMCTA had no effect on the histological analyses of the liver (0%, CI = 0-13.7%), left ventricle of the heart (0%, CI = 0-36.9%) and right kidney (0%, CI = 13.2%), however likely caused increased Bowman's capsule spaces in the left kidney of one case (4%, CI = 0.01-20.4%). Other artefactual histological changes identified included eosinophilic material in the liver, whiter interstitium and dilated tubules in kidney samples, and autolysis-related changes, however these could not be categorically attributed to the PMCTA procedure. PMCTA causes zero or minimal effect to the histological examination of the liver, left kidney, right kidney and left ventricle, and as such performing PMCTA prior to autopsy is unlikely to impact autopsy histological results in these organs.

Variations in the anatomy of the vertebral artery cervical loop segment - a potential predisposing factor for traumatic basal subarachnoid hemorrhage?

Fatal traumatic basal subarachnoid hemorrhage (TBSAH) is a characteristic forensic pathological entity, the investigation of which requires special techniques. In Liverpool, post-mortem room angiography is undertaken, followed by complete removal of the vertebral arteries and histological examination. It has been observed that the arterial anatomy can be highly variable, particularly the length and course of the loop segments located between the C2 vertebra and the dura. In a number of cases of TBSAH the loop segments of torn vessels have appeared relatively short. Having observed this phenomenon subjectively in our case work, a radiological study was undertaken with the aim of quantifying vertebral artery loop anatomy variation in a 'normal' population. Multiphase post-mortem computed tomography angiography (MPMCTA) scans of 98 subjects were reviewed and the lengths of the different portions of the loop segments (foramen magnum to the upper border of C1, between C1 and C2, and the bony foramina themselves) of each vertebral artery were measured using semi-automated vessel analysis software. The measurements obtained provide objective evidence of marked anatomical variation, with some loop segments more than twice the length of others. These results are important because a short vertebral artery loop segment might be a significant factor in predisposing an individual to TBSAH following a blow to the head or neck.

Temperature dependence of viscosity, relaxation times (T1, T2) and simulated contrast for potential perfusates in post-mortem MR angiography (PMMRA)

Developments in post-mortem imaging increasingly focus on addressing recognised diagnostic weaknesses, especially with regard to suspected natural deaths. Post-mortem MR angiography (PMMRA) may offer additional diagnostic information to help address such weaknesses, specifically in the context of sudden cardiac death. Complete filling of the coronary arteries and acceptable contrast with surrounding tissue are essential for a successful approach to PMMRA. In this work, the suitability of different liquids for inclusion in a targeted PMMRA protocol was evaluated. Factors influencing cooling of paraffinum liquidum + Angiofil® (6 %) in cadavers during routine multiphase post-mortem CT angiography were investigated. The temperature dependence of dynamic viscosity (8–20 °C), longitudinal (T₁) and transverse (T₂) relaxation (1–23 °C) of the proposed liquids was quadratically modelled. The relaxation behaviour of these liquids and MR scan parameters were further investigated by simulation of a radiofrequency (RF)-spoiled gradient echo (GRE) sequence to estimate potentially achievable contrast between liquids and post-mortem tissue at different temperatures across a forensically relevant temperature range. Analysis of the established models and simulations indicated that based on dynamic viscosity (27–33 mPa · s), short T₁ relaxation times (155–207 ms) and a minimal temperature dependence over the investigated range of these parameters, paraffin oil and a solution of paraffin oil + Angiofil® (6 %) would be most suitable for post-mortem reperfusion and examination in MRI.

Forensic 3D Visualization of CT Data Using Cinematic Volume Rendering: A Preliminary Study

OBJECTIVE

The 3D volume-rendering technique (VRT) is commonly used in forensic radiology. Its main function is to explain medical findings to state attorneys, judges, or police representatives. New visualization algorithms permit the generation of almost photorealistic volume renderings of CT datasets. The objective of this study is to present and compare a variety of radiologic findings to illustrate the differences between and the advantages and limitations of the current VRT and the physically based cinematic rendering technique (CRT).

MATERIALS AND METHODS

Seventy volunteers were shown VRT and CRT reconstructions of 10 different cases. They were asked to mark the findings on the images and rate them in terms of realism and understandability.

RESULTS

A total of 48 of the 70 questionnaires were returned and included in the analysis. On the basis of most of the findings presented, CRT appears to be equal or superior to VRT with respect to the realism and understandability of the visualized findings. Overall, in terms of realism, the difference between the techniques was statistically significant (p < 0.05). Most participants perceived the CRT findings to be more understandable than the VRT findings, but that difference was not statistically significant (p > 0.05).

CONCLUSION

CRT, which is similar to conventional VRT, is not primarily intended for diagnostic radiologic image analysis, and therefore it should be used primarily as a tool to deliver visual information in the form of radiologic image reports. Using CRT for forensic visualization might have advantages over using VRT if conveying a high degree of visual realism is of importance. Most of the shortcomings of CRT have to do with the software being an early prototype.

Morphometric analysis of stab wounds by MSCT and MRI after the instillation of contrast medium

OBJECTIVE

To analyze the morphology and depth of stab wounds experimentally produced on human legs amputated for medical reasons using multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) after the instillation of a single contrast medium solution (CMS).

MATERIALS AND METHODS

For morphological analysis, MSCT and MRI scans were performed before and after the instillation of CMS into the wound cavity. Depth measurements were performed on the sagittal view only after CMS instillation. Subsequently, each wound was dissected using the layer-by-layer technique and the depth was measured by a ruler. One-way between-groups pairwise analysis of variance (ANOVA) and Bland-Altman plot analysis were used for comparing radiological and anatomical measurements.

RESULTS

Unenhanced MSCT images did not identify the wound channels, whereas unenhanced MRI evidenced the wound cavity in 50 % of cases. After the instillation of CMS, both MSCT and MRI depicted the wound channel in all the investigated stabbings, although the morphology of the cavity was irregular and did not resemble the shape of the blade. The radiological measurements of the wounds' depth, after the application of CMS, exhibited a high level of agreement (about 95 % at Bland-Altman plot analysis) with the anatomical measurements at dissection. A similar systematic underestimation, however, has been evidenced for MSCT (average 11.4 %; 95 % CI 7-17) and MRI (average 9.6 %; 95 % CI 6-13) data after the instillation of CMS with respect to wound dissection measurements.

CONCLUSION

MSCT and MRI after the instillation of CMS can be used for depicting the morphometric features of stab wounds, although depth measurements are affected by a slight systematic underestimation compared to layer-by-layer dissection.

Whole-body post-mortem computed tomography angiography of a newborn revealing transposition of great arteries

The number of medico-legal post-mortem examinations referring to newborns is considerably low: In the case of the Chair and Department of Forensic Medicine of the author's origin, the autopsy rate of such cases is less than 1%. Even experienced forensic pathologists can find the technical autopsy procedure of a newborn quite difficult. Post-mortem imaging using unenhanced post-mortem computed tomography (PMCT) gives only a limited opportunity to help in conventional autopsy examination. By adding contrast medium (CA) administration, we can significantly expand diagnostic capabilities. However, the post-mortem computed tomography angiography (PMCTA) technique has already been developed mostly in adult death cases (as considerably much more frequent), and no standardised protocol for examination of children exists. The authors present the dual-phase PMCTA examination of a newborn by manual CA administration using the access to umbilical vessels (vein and artery) unveiling transposition of the great arteries (TGA). The results are presented as multiplanar reformatted (MPR) images and three-dimensional (3D) images by volume/surface-rendered reconstructions, giving a contribution towards proving the value of forensic imaging in post-mortem examinations of heart and vascular malformations in newborns.