Morphometric Comparison of Clavicle Outlines from 3D Bone Scans and 2D Chest Radiographs: A Shortlisting Tool to Assist Radiographic Identification of Human Skeletons

Human identification: an investigation of 3D models of paranasal sinuses to establish a biological profile on a modern UK population

Medical imaging is a valuable source for facilitating empirical research and provides an accessible gateway for developing novel forensic anthropological methods for analysis including 3D modelling. This is especially critical for the United Kingdom (UK), where methods developed from modern UK populations do not currently exist. This study introduces a new approach to assist in human identification using 3D models of the paranasal sinuses. The models were produced from a database of 500 modern CT scans provided by University College London Hospital. Linear measurements and elliptic Fourier coefficients taken from 1500 three-dimensional models across six ethnic groups assessed by one-way ANOVA and discriminant function analysis showed a range of classification rates with certain rates reaching 75-85.7% (p < 0.05) in correctly classifying age and sex according to size and shape. The findings offer insights into the potential for employing paranasal sinuses as an attribute for establishing the identification of unknown human remains in future crime reconstructions.

Technical Note: Individuals identified by radiographic comparison: A sample of demographics and the region of body used for identification in Clark County, Nevada, USA (2017-2020)

Radiographs regularly aid in identifications by comparing antemortem and postmortem images. The forensic community has widely accepted this method because radiographic images are low in cost, easily transferable, and generally believed to be uncomplicated to assess. However, there is a dearth of diverse, modern radiographic datasets as well as a deficiency in assessing population frequencies of nonmetric traits via radiographs. Further, radiographic comparisons, although typically required as a core competency of practicing forensic anthropologists, do not have standard training and education requirements. To understand the diversity and representation within an opportunistic dataset, we provide a case study of the demographics of decedents identified via radiographic comparison at the Clark County Office of the Coroner/Medical Examiner (CCOCME) in Las Vegas, NV, USA from 2017 to 2020. Additionally, we examined each region of the body used to make radiographic identifications. The sample was majority Caucasian and male, with a mean and median age at death of 64.9 years and 67.0 years, respectively. Our results indicated that this sample was not representative of the greater Clark County population. The most common body region used for comparisons was the chest, followed by the head and neck, pelvis, dentition, and the extremities. Thus, large generalizations made from these types of datasets must be implemented with caution due to the relative lack of diversity and representation. As well, current discussions regarding training and education of forensic anthropologists as they relate to radiographic comparisons are explored.

Evaluating artificial intelligence for comparative radiography

INTRODUCTION

Comparative radiography is a forensic identification and shortlisting technique based on the comparison of skeletal structures in ante-mortem and post-mortem images. The images (e.g., 2D radiographs or 3D computed tomographies) are manually superimposed and visually compared by a forensic practitioner. It requires a significant amount of time per comparison, limiting its utility in large comparison scenarios.

METHODS

We propose and validate a novel framework for automating the shortlisting of candidates using artificial intelligence. It is composed of (1) a segmentation method to delimit skeletal structures' silhouettes in radiographs, (2) a superposition method to generate the best simulated "radiographs" from 3D images according to the segmented radiographs, and (3) a decision-making method for shortlisting all candidates ranked according to a similarity metric.

MATERIAL

The dataset is composed of 180 computed tomographies and 180 radiographs where the frontal sinuses are visible. Frontal sinuses are the skeletal structure analyzed due to their high individualization capability.

RESULTS

Firstly, we validate two deep learning-based techniques for segmenting the frontal sinuses in radiographs, obtaining high-quality results. Secondly, we study the framework's shortlisting capability using both automatic segmentations and superimpositions. The obtained superimpositions, based only on the superimposition metric, allowed us to filter out 40% of the possible candidates in a completely automatic manner. Thirdly, we perform a reliability study by comparing 180 radiographs against 180 computed tomographies using manual segmentations. The results allowed us to filter out 73% of the possible candidates. Furthermore, the results are robust to inter- and intra-expert-related errors.

Infracranial radiographic comparison for human identification: A study of image quality and tissue shielding effects

In this study, we explore how image resolution and tissue shielding can impact correct classification rates (CCRs) of infracranial radiographic comparisons undertaken using small field-of-view radiographs. Thirty-six identification arrays (using clavicles and seventh cervical vertebra) were constructed with each array comprised of five radiographs: one X-ray of a single dry bone (postmortem [PM] skeletal image) and four simulated antemortem [AM] radiographs (radiographs taken pre-skeletization). One AM radiograph in each array represented the ground truth match to the PM radiograph (=25% rate of randomly selecting the correct match). Radiographs were digitally manipulated, so that four varieties of decreasing blur (Gaussian blur = 12-0 pr across 24 arrays), and, for PM clavicles, four varieties of decreasing hard tissue shielding (opacity of 40-0% across 12 arrays) existed. Arrays were evaluated, for their correct PM/AM pair, by 8 anthropologists trained in chest radiograph comparison (CXR; either currently or formerly competency certified by the Defense POW/MIA Accounting Agency CXR training program), 28 current American Board of Forensic Anthropology (ABFA) diplomates and 30 novices. Analysts' CCRs substantially improved when Gaussian blur was <10 pr (55% CCR at >10 pr vs. 89% for <10 pr). Tissue shielding effects increased CCRs on average by +10% for each -10% opacity step (between 40-0% opacity). The CXR anthropologists were the most tolerant of the more challenging identification contexts (highest blur and opacity), reconfirming that analyst training and expertise is an important factor, especially when poorer quality radiographic images are the subject of analysis.

Infra-cranial radiographic comparison for human identification: A study of analyst expertise

Radiographic comparison for identification is widely utilized. However, these methods are qualitative and subject to analyst ability to correctly read and interpret radiographs. With regards to infra-cranial radiographs, few studies have been conducted to explore the role of practitioner expertize on correct classification rates (CCRs). Here, we undertake two such studies using forensic anthropologists [American Board of Forensic Anthropology (ABFA) certified, practicing but not board-certified anthropologists, and chest radiograph comparison (CXR) anthropologists trained via the Defense POW/MIA Accounting Agency CXR competency training program] and compare their results to novices. To ensure participants only referred to the same skeletal morphology, we cropped radiographs to single bones. An array of four simulated antemortem radiographs was presented to each assessor with each postmortem radiograph. Assessors evaluated arrays for a correct match, which was always present, yielding a 25% rate for random correct selections. Study 1 used anteroposterior C7, posteroanterior second metacarpal, and lateral calcaneus radiographs (three arrays each for nine arrays total), which yielded 86, 81, 69, and 68% mean CCRs for CXR experts, ABFA anthropologists, non-ABFA anthropologists and novices, respectively. Study 2 used anteroposterior C7 and left clavicles (three arrays each for six arrays total), yielding mean CCRs of 100, 96, and 84% for CXR experts, ABFA anthropologists and novices, respectively. As reflected by the CCRs, expertise is clearly a factor for radiographic comparisons, evident not just between novices and anthropologists, but also between anthropologists. We recommend all radiographic comparison analysts be subject to competency/proficiency tests prior to their engagement for forensic casework.

Next-generation osteometric sorting: Using 3D shape, elliptical Fourier analysis, and Hausdorff distance to optimize osteological pair-matching

Determining which bilateral bones belong to the same person based on shape and size similarity is called pair-matching and it is instrumental for sorting commingled skeletons. To date, pair-matching has popularly been accomplished by visual inspection and/or linear caliper measurements; however, attention is turning increasingly to computational analysis. In this paper, we investigate a fast three-dimensional (3D) computerized shape-analysis method for whole-bone pair-matching using a test sample of 14 individuals (23 femora, 26 humeri, and 26 tibiae). Specifically, the method aims to find bilateral pairs using, as the shape signature criterion, a single 3D outline that snakes around each bone's perimeter as described by a 3D elliptical Fourier analysis function. This permits substantial 3D-point-cloud data reduction, that is, to 0.02% of the starting c.500,000 point cloud or just 100 points, while preserving key 3D shape information. The mean Hausdorff distance (Hd) was applied to measure the distance between each mirrored right-side outline to every left-side outline in pairwise fashion (132, 168 and 169 comparisons, respectively). Both thresholds and lowest Hd were investigated as pair-match criteria, with the lowest Hd producing the best performance results for searches jointly utilizing right-left and left-right directions for comparison: true positive rates of 1.00 (10/10), 1.00 (12/12), and 0.92 (11/12) for the femora, humeri, and tibiae, respectively. The computational time to calculate 469 pairwise 3D comparisons on a single stock-standard Intel^® Core™ i7-4650U CPU @ 1.70 GHz was 5 s. This short data processing time makes the method viable for real-world application.

Strengthening the role of forensic anthropology in personal identification: Position statement by the Board of the Forensic Anthropology Society of Europe (FASE)

In this position statement, the Board members of the Forensic Anthropology Society of Europe (FASE) argue that forensic anthropology methods can be used as means of personal identification, particularly in situations with limited availability of traditional identification methods (i.e. dactyloscopy, odontology, and molecular genetic analysis). This statement has been issued taking into account the international migration crises related to thousands of deaths worldwide, in which the utility of these traditional means of identification has been sporadic to non-existent. The statement is however not limited to deaths related to the migration crises, as similar problems may occur in fatalities en masse such as in natural disasters and armed conflicts, and on a smaller scale in cases of homeless or otherwise socioeconomically disadvantaged persons. The number of reports on personal identification based on sound anthropological methodology is increasing in the scientific literature. However, more research is needed to develop evidence-based standard operating procedures and statistical frameworks. It remains essential to raise awareness among forensic practitioners, law enforcement, and judiciary professionals on the utility of forensic anthropology in cases where it can provide sufficient information for identification.

Mitochondrial DNA haplogrouping to assist with the identification of unknown service members from the World War II Battle of Tarawa

The World War II Battle of Tarawa, 1943, was a devastating conflict that resulted in losses of more than 1100 American and 4690 Japanese troops. The United States government aims to identify and repatriate the remains of all missing American service members through the Defense Prisoner of War/Missing in Action (POW/MIA) Accounting Agency (DPAA) and its partners such as the Armed Forces Medical Examiner System's Armed Forces DNA Identification Laboratory (AFMES-AFDIL). Remains associated with the Battle of Tarawa have been recovered from field excavations conducted by History Flight, a DPAA strategic partner, as well as from the National Memorial Cemetery of the Pacific (NMCP) in Hawaii where unknowns have been disinterred for identification. DNA testing at the AFMES-AFDIL has produced mitochondrial DNA (mtDNA) sequences from 1027 case samples to date. Haplogroup assignments indicate that more than one third (36.2 %) of field-collected samples are likely of Asian maternal ancestry. Therefore the field collections from the Tarawa battlefield comprise the remains of American service members but also those of foreign nationals from Asia. The mtDNA of the NMCP unknowns is similar in ancestry proportion to the family reference sample distribution. The DPAA uses the ancestry information gleaned from mtDNA sequence data in conjunction with anthropological evidence to make foreign national determinations. In this way, mtDNA haplogrouping is used to sort the commingled and fragmentary remains recovered from Tarawa between Americans and foreign nationals, which are then repatriated to their country of origin.

The Utility of Skeletal and Surgical Features for the Personal Identification Process: A Pilot Study

This pilot study provides a conceptual framework for the application of the anthropological analysis of skeletal features and surgical interventions for the purpose of identification in cases of unknown deceased individuals with unavailable fingerprint, genetic or odontological antemortem data. The study sample includes 276 individuals with known demographic and clinical information from the Italian CAL Milano Cemetery Skeletal Collection. In the sample, 124 (45%) individuals showed one or more skeletal features that may be potentially individualizing. Of these, 79% showed two and more features, which occurred in a multitude of different combinations. Skeletal findings may provide useful postmortem information that can be compared with antemortem witness statements and clinical imaging. However, more research into the utility of dry bone findings and the availability of comparative material, including imaging, and epidemiological data needs to be undertaken before skeletal features can be implemented into identification protocols and databases.

Contributions of forensic anthropology to positive scientific identification: a critical Review

This review covers previous and current literature on the impact of forensic anthropologists on the positive scientific identification of human remains and aims to provide an understanding of what information a forensic anthropologist can contribute to an investigation. Forensic anthropologists looking to identify human remains study traits of the skeleton and any orthopedic devices present. In order to obtain a positive scientific identification, evidence that is both sufficiently unique to the individual and comparable to available antemortem data from that individual must be found. The increased availability of radiographs, scans and implants in recent decades has facilitated the identification process. When these records are unavailable, other techniques, such as craniofacial superimposition and facial approximation, can be employed. While these methods may assist the identification process, they are most useful for exclusion of certain individuals and gathering leads from the public. Forensic anthropologists have heavily relied on the skull and its complexities for identification – typically focusing on the frontal sinus and other unique traits. Post-cranial remains can provide important information about bone density, possible disease and other characteristics that may also be utilized. Techniques used to positively identify individuals are not limited to medicolegal death investigations, and have been useful in other legal contexts. In the future, a team approach, utilizing all the information gathered by multiple forensic scientists – including forensic anthropologists – will most likely become more common.

An Automated Two-dimensional Pairwise form Registration Method for Pair-matching of Fragmented Skeletal Remains

This study introduces an automated pairwise method for osteological pair-matching of fragmented skeletal remains using two-dimensional fragmented outlines extracted from photographs. The form data are used in pairwise iterative closest point registrations with rigid transformations. A modified version of the average Hausdorff distance is calculated to remove any coordinate correspondences with outline fracture margins, which allow the distance analysis of fragmented outlines. A dilation modification to the Hausdorff distance is proposed creating a greater separation between true- and false-pairs. The sample consists of 122 calcanei (61 pairs) from the UI-Stanford collection. Performance statistics are provided for simulated fragmented and complete assemblages. Results indicate up to 98% accuracy for fragmented and complete assemblages. The dilated Hausdorff distance performed similarly across assemblages, but showed a slight decrease in performance for the complete assemblage. This approach provides a useful short listing tool to reduce the number of visual comparisons required in large commingled assemblages.

Virtual anthropology - a brief review of the literature and history of computed tomography

Computed tomography (CT) has influenced numerous fields since its inception in the 1970s. The field of palaeoanthropology significantly benefited from this efficient and non-invasive medium in terms of the conservation, reconstruction and analysis of fossil human remains. Over the past decade, there has been a steady increase in the number of forensic anthropological studies incorporating virtual osteological analyses. Because of the increasing importance of these modern cross-sectional imaging techniques and the requirement for standardized parameters in forensic science, we deemed it important to outline the history and development of CT applications in these related academic areas. The present paper outlines the history of “virtual anthropology” and osteological multi-detector CT in the context of palaeoanthropology and forensic anthropology.

Critical issues in the historical and contemporary development of forensic anthropology in Australia: An international comparison

The aim of this brief critical qualitative analysis is to examine the development of forensic anthropology in Australia, at a time of significant change in the discipline. It will briefly summarise its historical establishment, making comparative reference to other regions-particularly the United Kingdom and United States, and the influence of the Bali Bombings of 2002, Indian Ocean earthquake and tsunami of 2004 and Black Saturday Bushfires of 2009. The analysis goes on to consider key factors in research in forensic anthropology in the United States, and the development of standards and regulation in the US and UK. The significance of research in post-mortem diagenesis in Brazil-a country sharing aspects of climate, soil types and demography with Australia-is also considered, as well as the significance of patterns of casework encountered in Australia compared with those of other jurisdictions. While forensic anthropology as a discipline has grown remarkably in recent years, this analysis suggests that research and training tailored to the specific pattern of casework encountered in Australia is now essential to support the development of national standards in science, education, and professional regulation. The significance of the establishment of the first taphonomy research facility outside of the US-the Australian Facility for Taphonomic Experimental Research-is briefly considered with reference to what this facility may offer to the development of forensic anthropology in Australia.

Elliptical Fourier analysis: fundamentals, applications, and value for forensic anthropology

The numerical description of skeletal morphology enables forensic anthropologists to conduct objective, reproducible, and structured tests, with the added capability of verifying morphoscopic-based analyses. One technique that permits comprehensive quantification of outline shape is elliptical Fourier analysis. This curve fitting technique allows a form's outline to be approximated via the sum of multiple sine and cosine waves, permitting the profile perimeter of an object to be described in a dense (continuous) manner at a user-defined level of precision. A large amount of shape information (the entire perimeter) can thereby be collected in contrast to other methods relying on sparsely located landmarks where information falling in between the landmarks fails to be acquired. First published in 1982, elliptical Fourier analysis employment in forensic anthropology from 2000 onwards reflects a slow uptake despite large computing power that makes its calculations easy to conduct. Without hurdles arising from calculation speed or quantity, the slow uptake may partly reside with the underlying mathematics that on first glance is extensive and potentially intimidating. In this paper, we aim to bridge this gap by pictorially illustrating how elliptical Fourier harmonics work in a simple step-by-step visual fashion to facilitate universal understanding and as geared towards increased use in forensic anthropology. We additionally provide a short review of the method's utility for osteology, a summary of past uses in forensic anthropology, and software options for calculations that largely save the user the trouble of coding customized routines.

A Large-Sample Test of a Semi-Automated Clavicle Search Engine to Assist Skeletal Identification by Radiograph Comparison

In 2014, a morphometric capability to search chest radiograph databases by quantified clavicle shape was published to assist skeletal identification. Here, we extend the validation tests conducted by increasing the search universe 18-fold, from 409 to 7361 individuals to determine whether there is any associated decrease in performance under these more challenging circumstances. The number of trials and analysts were also increased, respectively, from 17 to 30 skeletons, and two to four examiners. Elliptical Fourier analysis was conducted on clavicles from each skeleton by each analyst (shadowgrams trimmed from scratch in every instance) and compared to the search universe. Correctly matching individuals were found in shortlists of 10% of the sample 70% of the time. This rate is similar to, although slightly lower than, rates previously found for much smaller samples (80%). Accuracy and reliability are thereby maintained, even when the comparison system is challenged by much larger search universes.

Evolution of Forensic Anthropological Methods of Identification

Forensic identification of human remains has long been a core contribution of forensic anthropologists to death investigations. The array and scientific robusticity of the identification methods employed by the anthropologist has evolved in the last several decades, and as with other nonidentification methods, anthropologists have embraced the progression toward the use of validated and statistically defensible methods for identification. This article presents an overview of the role that the forensic anthropologist plays in the identification of human remains and the evolution of anthropological methods of identification.

Skeletal idiopathic osteosclerosis helps to perform personal identification of unknown decedents: A novel contribution from anatomical variants through CT scan

Personal identification consists of the comparison of ante-mortem information from a missing person with post-mortem data obtained from an unidentified corpse. Such procedure is based on the assessment of individualizing features which may help in providing a conclusive identification between ante-mortem and post-mortem material. Anatomical variants may provide important clues to correctly identify human remains. Areas of idiopathic osteosclerosis (IO), or dense bone islands (DBIs) characterized by radiopaque areas of dense, trabeculated, non-inflamed vital bone represent one of these, potentially individualizing, anatomical features. This study presents a case where the finding of DBI was crucial for a positive identification through CT-scan. A decomposed body was found in an apartment in June 2014 in advanced decomposition and no dental records were available to perform a comparison for positive identification. Genetic tests were not applicable because of the lack of relatives in a direct line. The analysis of the only ante-mortem documentation, a CT-scan to the deceased dating back to August 2009, showed the presence of three DBIs within the trabecular bone of the proximal portion of the right femur. The same bony district was removed from the corpse during the autopsy and analysed by CT-scan, which verified the presence of the same features. Forensic practitioners should therefore be aware of the great importance of anatomical bone variants, such as dense bone islands for identification purposes, and the importance of advanced radiological technique for addressing the individualizing potential of such variants. We propose that anatomical variants of the human skeleton should be considered as being "primary identification characteristics" similar to dental status, fingerprints and DNA.

Quantification of perspective-induced shape change of clavicles at radiography and 3D scanning to assist human identification

Change in perspective between antemortem and postmortem imaging sessions (radiograph to radiograph and surface scan to radiograph) may cause different 2D renderings of the same osseous element complicating comparisons for identification. In this study, clavicle shape changes due to radiographic positioning and 3D laser scanning were examined in 20 right-side specimens, as pertinent to chest radiograph comparisons. Results indicate substantial changes in clavicle form with short source-to-image receptor distance, elevation of the element from the image receptor, and movement of the element away from the center beam (10% mean square for shape). Although quantitative shape differences were small when the clavicle was in close opposition to the image receptor (3% mean square), important qualitative differences remained with large distances from the center beam (e.g., conoid tubercle presence/absence). The significance of these results for image superimposition and computer-automated-shape-based searches of radiographic libraries to find matching candidates is discussed.