Multi-camera system for 3D forensic documentation

Single-camera photogrammetry using a mobile phone for low-cost documentation of corpses

Photogrammetry is a technique for studying and defining objects' shape, dimension, and position in a three-dimensional space using measurements obtained from two-dimensional photographs. It has gained popularity following the development of computer graphics technologies and has been applied to various branches of medicine. In this study, the authors present a method for low-cost photorealistic documentation of corpses during autopsy using single-camera photogrammetry with a mobile phone. Besides representing the body by demonstrating the injured and non-injured body parts as control, evidencing the body parts on a 3D reconstruction allows easy explanation to nonmedical experts such as lawyers.

Cost-effective 3D documentation device in forensic medicine

3D documentation in forensics and forensic medicine is being introduced more frequently in various institutes around the world. However, several institutes lack capacity in finances as well as staff to perform 3D documentations regularly. This technical paper aims to present a 3D documentation device that is low cost and easy to use and is a viable entry level solution for forensic medical departments. For this the small single-board computer Raspberry Pi 4 was used in conjunction with its high quality (HQ) camera module to create the 3DLamp - a flexible, low cost and easy to use documentation device. Besides a detailed description of the device this paper also presents four case examples where a 3D documentation was performed and analyses the acquired data and the created 3D models. It was found that the device returns feasible 3D models that appear usable for forensic 3D reconstructions.

A consistent methodology for forensic photogrammetry scanning of human remains using a single handheld DSLR camera

Due to increasingly capable algorithms and more available processing power, photogrammetry is becoming a simple, cheap, and accurate alternative to 3D optical surface scanning. With adequate application, it can be a swift documentation technique for reconstructing the geometry and body surface of deceased persons in autopsies or other forensic medical examinations. Sufficiently easy and swift 3D documentation techniques may allow 3D imaging technologies to become part of the daily routine of any forensic medical examiner or other medical personnel. This paper presents a consistent and systematic photographing methodology (as an alternative to automated or intuitive methods) for photogrammetry scanning of human remains. Although it requires manual photography, the methods presented in this paper offer a swift and easy way to capture an accurate 3D model of human remains under almost any conditions. Four different photographing procedures were tested on four subjects: (i) a systematic circular technique with 100 photos, (ii) a systematic circular technique with 50 photos, (iii) a technique loosely mimicking cameras mounted on a postmortem CT device with 98 photos, and (iv) a technique mimicking cameras mounted on a postmortem CT device with 49 photos. Measurement accuracy was tested with the aid of six adhesive control points placed at approximately the same locations on each subject. Five different distances defined by these control points were measured and compared to the measurements taken by hand. 3D photogrammetry meshes created using these techniques were also compared with point clouds acquired using a 3D laser scanner. We found that a carefully composed, tested, and systematic photographing procedure significantly improved the quality of the photogrammetry models. In terms of relative difference compared to the hand measurements, both Techniques 1 and 2 produced close results, with an average relative difference of 0.160% and 0.197% and a maximum relative difference of 0.481% and 0.481%, respectively, while models reconstructed from images taken using Techniques 3 and 4 seemed to be much less accurate, with an average relative difference of 0.398% and 0.391% and a maximum relative difference as high as 1.233% and 1.139%, respectively. This study highlights the importance of a scientifically tested methodology for obtaining high-quality 3D models in forensic applications.

Key points

Close-range photogrammetry is an easy, fast, and cheap way to acquire 3D models of human remains of forensic importance.A carefully composed, tested, and systematic photographing procedure has a key role and can greatly increase the quality of photogrammetry models.A photogrammetry-based 3D-digitalization technique could be developed and adopted as part of the daily routine during autopsies.Photogrammetry-based 3D models are much quicker to acquire, look more photorealistic, and are almost as accurate as certain laser scanner-based models.

A Virtual, 3D Multimodal Approach to Victim and Crime Scene Reconstruction

In the last two decades, forensic pathology and crime scene investigations have seen a rapid increase in examination tools due to the implementation of several imaging techniques, e.g., CT and MR scanning, surface scanning and photogrammetry. These tools encompass relatively simple visualization tools to powerful instruments for performing virtual 3D crime scene reconstructions. A multi-modality and multiscale approach to a crime scene, where 3D models of victims and the crime scene are combined, offers several advantages. A permanent documentation of all evidence in a single 3D environment can be used during the investigation phases (e.g., for testing hypotheses) or during the court procedures (e.g., to visualize the scene and the victim in a more intuitive manner). Advanced computational approaches to understand what might have happened during a crime can also be applied by, e.g., performing a virtual animation of the victim in the actual context, which can provide important information about possible dynamics during the event. Here, we present an overview of the different techniques and modalities used in forensic pathology in conjunction with crime scene investigations. Based on our experiences, the advantages and challenges of an image-based multi-modality approach will be discussed, including how their use may introduce new visualization modalities in court, e.g., virtual reality (VR) and 3D printing. Finally, considerations about future directions in research will be mentioned.

Augmented reality in forensics and forensic medicine - Current status and future prospects

Forensic investigations require a vast variety of knowledge and expertise of each specialist involved. With the increase in digitization and advanced technical possibilities, the traditional use of a computer with a screen for visualization and a mouse and keyboard for interactions has limitations, especially when visualizing the content in relation to the real world. Augmented reality (AR) can be used in such instances to support investigators in various tasks at the scene as well as later in the investigation process. In this article, we present current applications of AR in forensics and forensic medicine, the technological basics of AR, and the advantages that AR brings for forensic investigations. Furthermore, we will have a brief look at other fields of application and at future developments of AR in forensics.

Identification parade in immersive virtual reality - A technical setup

Virtual Reality (VR) has sparked interest within the forensic community, where it is currently used for training purposes and in variety of forensic scenarios. In combination with efficient and user friendly full body 3-Dimensional (3D) documentation methods, VR visualisations present a viable tool for suspect witness identification. The well-known procedure of placing several persons in a room with a one-way-mirror, along with a witness on the other side of the mirror has practical disadvantages. The primary concern implicates the witness(s) and person(s) of interest coming face-to-face prior to the line-up, combined with finding sufficient persons to include within the line-up. Although image identification using printed paper partially resolved this problem, features such as body stature also marks an issue for the recognition and identification process. To test whether VR provides the technical capabilities to perform an identification parade, a total of 15 subjects were 3D documented using the multi-camera device "Photobox". From this group, one of the documented persons then interrupted a lecture, where consequently, the students were asked afterwards to identify the same person in VR and paper identification sets. It was found that the participating students were able to identify the "suspect" in both datasets. The results imply that VR technology allow users to identify persons. However, as this is a preliminary study the similarity problem was not analysed in this paper and requires further investigation to demonstrate the robustness of this approach.

The Introduction of a New Diagnostic Tool in Forensic Pathology: LiDAR Sensor for 3D Autopsy Documentation

Autopsy is a complex and unrepeatable procedure. It is essential to have the possibility of reviewing the autoptic findings, especially when it is done for medico-legal purposes. Traditional photography is not always adequate to record forensic practice since two-dimensional images could lead to distortion and misinterpretation. Three-dimensional (3D) reconstructions of autoptic findings could be a new way to document the autopsy. Besides, nowadays, smartphones and tablets equipped with a LiDAR sensor make it extremely easy to elaborate a 3D model directly in the autopsy room. Herein, a quality and trustworthiness evaluation of 3D models obtained during ten autopsies is made comparing 3D models and conventional autopsy photographic records. Three-dimensional models were realistic and accurate and allowed precise measurements. The review of the autoptic report was facilitated by the 3D model. Conclusions: The LiDAR sensor and 3D models have been demonstrated to be a valid tool to introduce some kind of reproducibility into the autoptic practice.

The forensic holodeck - Recommendations after 8 years of experience for additional equipment to document VR applications

The forensic holodeck was first introduced in 2013, using the first upcoming commercially available virtual reality gaming headsets to visualize forensic 3D reconstructions. Following the publication of this development virtual reality was introduced in case work in a variety of different ways. After 8 years of using virtual reality in a professional forensic capacity this professional practice report will show, which equipment is necessary in addition to a virtual reality setup. This mostly includes audio-visual and broadcasting technology for complete documentation of the application of virtual reality, but also some other IT equipment, which should be available for as low as 20'000 US$. Guidelines, hints and tips regarding equipment acquisition, setup and use will be provided and discussed.

The development of a low-cost photogrammetry-based 3D hand scanner

Acquiring an accurate 3D scan of the human hand is a challenging task, mainly due to the complicated geometry and the instability of the hand. In this paper, we present a low-cost photogrammetry-based scanner that is designed for scanning the human hand. The scanner has fifty modules, each has a Raspberry Pi with an 8-megapixels camera. They are uniformly positioned in two parallel frames and 96% of a hand surface can be viewed by at least 3 cameras. Using the timestamp method, we synchronize the shutters of the 50 cameras within the range of 80 ms to minimize the influence of the instability of the hand. Moreover, the scanner is easy to build with its modular design, and easy to operate with a laptop that is connected to the system by WiFi. Using a 3D printed prosthetic hand, we compared the 3D scanning accuracy of the proposed scanner with the Artec Spider® scanner. The mean absolute error between the two scans is 0.62 ± 0.28 mm. It is concluded that the proposed hand scanner can be used as a low-cost yet accurate tool in many applications, such as personalized product design.

Comparison of superficial wound documentation using 2D forensic photography, 3D photogrammetry, Botscan© and VR with real-life examination

Evidence acquisition, interpretation and preservation are essential parts of forensic case work that make a standardized documentation process fundamental. The most commonly used method for the documentation and interpretation of superficial wounds is a combination of two modalities: two-dimensional (2D) photography for evidence preservation and real-life examination for wound analysis. As technologies continue to develop, 2D photography is being enhanced with three-dimensional (3D) documentation technology. In our study, we compared the real-life examination of superficial wounds using four different technical documentation and visualization methods.

To test the different methods, a mannequin was equipped with several injury stickers, and then the different methods were applied. A total of 42 artificial injury stickers were documented in regard to orientation, form, color, size, wound borders, wound corners and suspected mechanism of injury for the injury mechanism. As the gold standard, superficial wounds were visually examined by two board-certified forensic pathologists directly on the mannequin. These results were compared to an examination using standard 2D forensic photography; 2D photography using the multicamera system Botscan©, which included predefined viewing positions all around the body; and 3D photogrammetric reconstruction based on images visualized both on screen and in a virtual reality (VR) using a head-mounted display (HMD).

The results of the gold standard examination showed that the two forensic pathologists had an inter-reader agreement ranging from 69% for the orientation and 11% for the size of the wounds. A substantial portion of the direct visual documentation showed only a partial overlap, especially for the items of size and color, thereby prohibiting the statistical comparison of these two items. A forest plot analysis of the remaining six items showed no significant difference between the methods. We found that among the forensic pathologists, there was high variability regarding the vocabulary used for the description of wound morphology, which complicated the exact comparison of the two documentations of the same wound.

There were no significant differences for any of the four methods compared to the gold standard, thereby challenging the role of real-life examination and 2D photography as the most reliable documentation approaches. Further studies with real injuries are necessary to support our evaluation that technical examination methods involving multicamera systems and 3D visualization for whole-body examination might be a valid alternative in future forensic documentation.

Clinical forensic height measurements on injured people using a multi camera device for 3D documentation

Documenting the existence, size, position and shape of injuries is an important part of medical forensic examinations. In the photography of an injury, the documentation is limited to an approximation of size and position of the injury based on a ruler included in the image. The documentation of injuries can be improved with photogrammetry, which allows the creation of scaled 3D models of an injury that can be used to not only document and visualize the injury but also to match the injury with an injury-causing object. In this paper, the multicamera device “Botscan” was used to perform 3D whole-body documentation and measure the positions of injuries. A major advantage of 3D whole-body documentation compared to photography is that the former can be performed at a later stage of the investigation. This makes the whole-body 3D documentation of injuries an important tool for re-examination.

Evaluating phone camera and cloud service-based 3D imaging and printing of human bones for anatomical education

OBJECTIVE

To evaluate the feasibility of a phone camera and cloud service-based workflow to image bone specimens and print their three-dimensional (3D) models for anatomical education.

DESIGN

The images of four typical human bone specimens, photographed by a phone camera, were aligned and converted into digital images for incorporation into a digital model through the Get3D website and submitted to an online 3D printing platform to obtain the 3D printed models. The fidelity of the 3D digital, printed models relative to the original specimens, was evaluated through anatomical annotations and 3D scanning.

SETTING

The Morphologic Science Experimental Center, Central South University, China.

PARTICIPANTS

Specimens of four typical bones-the femur, rib, cervical vertebra and skull-were used to evaluate the feasibility of the workflow.

OUTCOME MEASURES

The gross fidelity of anatomical features within the digital models and 3D printed models was evaluated first using anatomical annotations in reference to Netter's Atlas of Human Anatomy. The measurements of the deviation were quantised and visualised for analysis in Geomagic Control 2015.

RESULTS

All the specimens were reconstructed in 3D and printed using this workflow. The overall morphology of the digital and 3D printed models displayed a large extent of similarity to the corresponding specimens from a gross anatomical perspective. A high degree of similarity was also noticed in the quantitative analysis, with distance deviations ≤2 mm present among 99% of the random sampling points that were tested.

CONCLUSION

The photogrammetric digitisation workflow adapted in the present study demonstrates fairly high precision with relatively low cost and fewer equipment requirements. This workflow is expected to be used in morphological/anatomical science education, particularly in institutions and schools with limited funds or in certain field research projects involving the fast acquisition of 3D digital data on human/animal bone specimens or on other remains.

A toolbox for the rapid prototyping of crime scene reconstructions in virtual reality

Virtual reality is recently finding its way in forensic work. The required 3D data is nowadays a standard dataset available in many cases, from homicide to traffic collisions, including not only data from the scene but also of weaponry and involved persons. Current investigations use these 3D data to replicated the incident and as discussion base for forensic personal. However, modifying the scene on a 2D viewport is often cumbersome due to the loss of the third dimension. Also to perform the modifications on the scene a 3D operator is often required. Virtual reality might improve this step by its easy use and by visualising the third dimension. This publication presents a variety of tools which can be used in forensic investigations. Additionally to the tools, examples of forensic use of these tools will be presented, showing that already a small number of tools support a variety of forensic applications.

Application of Photogrammetry in Biomedical Science

Photogrammetry is an upcoming technology in biomedical science as it provides a non-invasive and cost-effective alternative to established 3D imaging techniques such as computed tomography. This review introduces the photogrammetry approaches currently used for digital 3D reconstruction in biomedical science and discusses their suitability for different applications. It aims to offer the reader a better understanding of photogrammetry as a 3D reconstruction technique and to provide some guidance on how to choose the appropriate photogrammetry approach for their research area (including single- versus multi-camera setups, structure-from-motion versus conventional photogrammetry and macro- versus microphotogrammetry) as well as guidance on how to obtain high-quality data. This review highlights some key advantages of photogrammetry for a variety of applications in biomedical science, but it also discusses the limitations of this technique and the importance of taking steps to obtain high-quality images for accurate 3D reconstruction.

Forensic 3D documentation of skin injuries using photogrammetry: photographs vs video and manual vs automatic measurements

Accurate and precise documentation of lesions is an important aspect of the forensic pathologists' work. Photogrammetry provides a useful tool to take precise measurements from photographs. These photographs are normally acquired with single camera photographs, but the procedure is quite time-consuming. Video recording has the potential to record a larger amount of image data faster. We documented 33 cadaveric skin lesions, using photographs and video recordings. The dimensions of the lesions ranged between 0.27 and 21.8 cm. The measurements of the lesions were extracted with both manual and automatic point measurements from photographs and from video frames, respectively. Very small differences (mean and median < 1 mm) were found between measurements taken in photographs versus video frames. Video frames were often blurred, preventing clear demarcation of the edges of the lesions and presenting a larger amount of noise in the 3D models. The differences between the manual point and automatic point measurements were very small (mean and median < 1 mm), but the manual procedure is to be preferred, since automatic points were not always located on the edges of the lesions. The only aspect in which video frames were superior to photographs was the recording time: video recording was almost five times faster than the photo sessions. In conclusion, this study shows that precise and comparable measurements can be extracted both from photographs and video frames. The video is the fastest method, but the use of photographs is still recommended. Manual measurements are more precise than automatic measurements and equally time-consuming.

Applying virtual reality in forensics - a virtual scene walkthrough

A major task of forensic investigations is the documentation and interpretation of evidence to reconstruct a forensically relevant incident. To accomplish this task, a scene is documented not only with photographs but also with 3D documentation technologies. The resulting 3D data are used for 3D visualization and to perform 3D reconstructions. In this article, we present an approach for using forensic 3D data in conjunction with virtual reality to perform scene walkthroughs in the context of witness or suspect interrogations. The aim is to provide a method for scene visits showing the original scene even years after the incident. These scene walkthroughs in VR can be reproduced and allow to see through the eyes of a witness by recording their behavior and actions. These recordings allow subsequent examinations and reconstruction to support the investigation and scene understanding and can be used as evidence in court.

Comparison of forensic photo-documentation to a photogrammetric solution using the multi-camera system "Botscan"

As forensic science technologies progress, digital photography has become outdated for certain documentations that require exact measurements. Recording three-dimensional objects on a two-dimensional photograph leads to a potential loss of relevant information. Photogrammetry has been utilized to record persons, objects or crime scenes and prevents this loss. Photogrammetry enables accurate documentation and visualization of events or matching of injuries and injury-causing instruments. To reduce inaccuracies during photogrammetric recording, a multi camera device, Botscan by Botspot, can be used to record living persons in three-dimensional space (3D). The device can record a full body in a fraction of a second, which leads to a significant reduction of inaccuracies due to movement. Photogrammetric measurements were compared with measurements from forensic photographs to evaluate the applicability of this device for medical forensic documentation of injuries. For this purpose, a mannequin fitted with different types of artificial injuries was used as an example. The results showed that the photogrammetric measurements obtained using the software Agisoft PhotoScan were more accurate than the measurements from the forensic photographs.

Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstructions: Living and dead subjects

Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutions many years ago and has proved to be a useful tool. 3D models of bones, skin, internal organs and bullet paths can rapidly be generated using post-processing software. These 3D models reflect the individual physiognomics and can be used to create whole-body 3D virtual animations. In such way, virtual reconstructions of the probable ante-mortem postures of victims can be constructed and contribute to understand the sequence of events. This procedure is demonstrated in two victims of gunshot injuries. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. Whole-body PMCT was performed and 3D reconstructions of bones, relevant internal organs and bullet paths were generated. Using 3ds Max software and a human anatomy 3D model, a virtual animated body was built and probable ante-mortem postures visualized. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident: one in the left arm and two in the thorax. Only CT scans of the thorax, abdomen and the injured arm were provided by the hospital. Therefore, a whole-body 3D model reflecting the anatomical proportions of the patient was made combining the actual bones of the victim with those obtained from the human anatomy 3D model. The resulted 3D model was used for the animation process. Several probable postures were also visualized in this case. It has be shown that in Case #1 the lesions and the bullet path were not consistent with an upright standing position; instead, the victim was slightly bent forward, i.e. he was sitting or running when he was shot. In Case #2, one of the bullets could have passed through the arm and continued into the thorax. In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem postures based on both PMCT and clinical CT.

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.

Forensic 3D documentation of skin injuries

An accurate and precise documentation of injuries is fundamental in a forensic pathological context. Photographs and manual measurements are taken of all injuries during autopsies, but ordinary photography projects a 3D wound on a 2D space. Using technologies such as photogrammetry, it is possible to create 3D detailed, to-scale, true-color documentation of skin injuries from 2D pictures. A comparison between the measurements of 165 lesions taken during autopsies and on photogrammetrically processed pictures was performed. Different types of lesions were considered: 38 blunt force injuries, 58 sharp force injuries, and 69 gunshot injuries. In all cases, very low differences were found with mean ≤ 0.06 cm and median ≤ 0.04 cm; a mean difference of 0.13 cm was found for the blunt force injuries. Wilcoxon signed-rank test showed no statistically significant differences between the two measurement methods (p > 0.05). The results of intra- and inter-observer tests indicated perfect agreement between the observers with mean value differences of ≤ 0.02 cm. This study demonstrated the validity of using photogrammetry for documentation of injuries in a forensic pathological context. Importantly, photogrammetry provides a permanent 3D documentation of the injuries that can be reassessed with great accuracy at any time. Such 3D models may also be combined with 3D reconstruction obtained from post-mortem CT scans for a comprehensive documentation of the lesion (internal and external information) and ultimately used for virtual reconstruction.

Finite Element Model and Validation of Nasal Tip Deformation

Nasal tip mechanical stability is important for functional and cosmetic nasal airway surgery. Palpation of the nasal tip provides information on tip strength to the surgeon, though it is a purely subjective assessment. Providing a means to simulate nasal tip deformation with a validated model can offer a more objective approach in understanding the mechanics and nuances of the nasal tip support and eventual nasal mechanics as a whole. Herein we present validation of a finite element (FE) model of the nose using physical measurements recorded using an ABS plastic-silicone nasal phantom. Three-dimensional photogrammetry was used to capture the geometry of the phantom at rest and while under steady state load. The silicone used to make the phantom was mechanically tested and characterized using a linear elastic constitutive model. Surface point clouds of the silicone and FE model were compared for both the loaded and unloaded state. The average Hausdorff distance between actual measurements and FE simulations across the nose were 0.39 ± 1.04 mm and deviated up to 2 mm at the outermost boundaries of the model. FE simulation and measurements were in near complete agreement in the immediate vicinity of the nasal tip with millimeter accuracy. We have demonstrated validation of a two-component nasal FE model, which could be used to model more complex modes of deformation where direct measurement may be challenging. This is the first step in developing a nasal model to simulate nasal mechanics and ultimately the interaction between geometry and airflow.