Aspects of 3D surface scanner performance for post-mortem skin documentation in forensic medicine using rigid benchmark objects (original) (raw)

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 pho-togrammetry 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.

Documentation and analysis of traumatic injuries in clinical forensic medicine involving structured light three-dimensional surface scanning versus photography

Journal of Forensic and Legal Medicine, 2018

Non-contact three-dimensional (3D) surface scanning has been applied in forensic medicine and has been shown to mitigate shortcoming of traditional documentation methods. The aim of this paper is to assess the efficiency of structured light 3D surface scanning in recording traumatic injuries of live cases in clinical forensic medicine. The work was conducted in Medico-Legal Centre in Benghazi, Libya. A structured light 3D surface scanner and ordinary digital camera with close-up lens were used to record the injuries and to have 3D and two-dimensional (2D) documents of the same traumas. Two different types of comparison were performed. Firstly, the 3D wound documents were compared to 2D documents based on subjective visual assessment. Additionally, 3D wound measurements were compared to conventional measurements and this was done to determine whether there was a statistical significant difference between them. For this, Friedman test was used. The study established that the 3D wound documents had extra features over the 2D documents. Moreover; the 3D scanning method was able to overcome the main deficiencies of the digital photography. No statistically significant difference was found between the 3D and conventional wound measurements. The Spearman's correlation established strong, positive correlation between the 3D and conventional measurement methods. Although, the 3D surface scanning of the injuries of the live subjects faced some difficulties, the 3D results were appreciated, the validity of 3D measurements based on the structured light 3D scanning was established. Further work will be achieved in forensic pathology to scan open injuries with depth information.

Using structured light three-dimensional surface scanning on living individuals: Key considerations and best practice for forensic medicine A R T I C L E I N F O

Journal of Forensic and Legal Medicine, 2018

Non-contact three-dimensional (3D) surface scanning methods have been applied to forensic medicine to record injuries and to mitigate ordinary photography shortcoming. However, there are no literature concerning practical guidance for 3D surface scanning of live victims. This paper aimed to investigate key 3D scanning issues of the live body to develop a series of scanning principles for future use on injured victims. The Pico Scan 3D surface scanner was used on live test subjects. The work focused on analysing the following concerns: (1) an appropriate 3D scanning technique to scan different body areas, (2) the ideal number of scans, (3) scanning approaches to access various areas of the body and (4) elimination of environmental background noise in the acquired data. Results showed that scanning only a required surface of the body area in the stable manner was more efficient when compared to complete 360°-scanning; therefore, it used as a standard 3D scanning technique. More than three scans were sufficient when trying to obtain an optimal wireframe mode presentation of the result. Three different approaches were suggested to provide access to the various areas of the body. Undertaking scanning using a black background eliminated the background noise. The work demonstrated that the scanner will be promising to reconstruct injuries from different body areas, although the 3D scanning of the live subjects faced some challenges.

Testing photogrammetry-based techniques for three-dimensional surface documentation in forensic pathology

Three-dimensional surface technologies particularly close range photogrammetry and optical surface scanning have recently advanced into affordable, flexible and accurate techniques. Forensic postmortem investigation as performed on a daily basis, however, has not yet fully benefited from their potentials. In the present paper, we tested two approaches to 3D external body documentation – digital camera-based photogrammetry combined with commercial Agisoft PhotoScan1 software and stereophotogrammetry- based Vectra H11, a portable handheld surface scanner. In order to conduct the study three human subjects were selected, a living person, a 25-year-old female, and two forensic cases admitted for postmortem examination at the Department of Forensic Medicine, Hradec Kra´ love´ , Czech Republic (both 63-year-old males), one dead to traumatic, self-inflicted, injuries (suicide by hanging), the other diagnosed with the heart failure. All three cases were photographed in 3608 manner with a Nikon 7000 digital camera and simultaneously documented with the handheld scanner. In addition to having recorded the pre-autopsy phase of the forensic cases, both techniques were employed in various stages of autopsy. The sets of collected digital images (approximately 100 per case) were further processed to generate point clouds and 3D meshes. Final 3D models (a pair per individual) were counted for numbers of points and polygons, then assessed visually and compared quantitatively using ICP alignment algorithm and a cloud point comparison technique based on closest point to point distances. Both techniques were proven to be easy to handle and equally laborious. While collecting the images at autopsy took around 20 min, the post-processing was much more time-demanding and required up to 10 h of computation time. Moreover, for the full-body scanning the post-processing of the handheld scanner required rather time-consuming manual image alignment. In all instances the applied approaches produced high-resolution photorealistic, real sized or easy to calibrate 3D surface models. Both methods equally failed when the scanned body surface was covered with body hair or reflective moist areas. Still, it can be concluded that single camera close range photogrammetry and optical surface scanning using Vectra H1 scanner represent relatively low-cost solutions which were shown to be beneficial for postmortem body documentation in forensic pathology.

TECHNICAL NOTE GENERAL Determining the Effectiveness of Noncontact Three-Dimensional Surface Scanning for the Assessment of Open Injuries

Journal of Forensic Sciences, 2019

Noncontact three-dimensional (3D) surface scanning methods are used within forensic medicine to record traumas and other related findings. A structured light scanning technique is one of these methods and the most suitable for the forensic field. An assessment of the efficiency of different structured light scanners with forensic injuries is essential to validate this technique for wound documentation. The purpose of this study was to evaluate the capability of the HP structured light scanner Pro S3 for digitizing open injuries having complicated areas and depths. Fifteen simulated injuries on mannequins were scanned and assessed. Comparisons between 3D and direct wound measurements were made. The results showed that the technique was able to create detailed 3D results of the extensive injuries. Statistical significance tests revealed no difference between the two measurement methods. Because the scanner is applicable for routine work, it should be considered to confirm the same results on real cadavers and actual wounds.

Bite mark documentation and analysis: the forensic 3D/CAD supported photogrammetry approach

Forensic Science International, 2003

Bite mark identification is based on the individuality of a dentition, which is used to match a bite mark to a suspected perpetrator. This matching is based on a tooth-by-tooth and arch-to-arch comparison utilising parameters of size, shape and alignment. The most common method used to analyse bite mark are carried out in 2D space. That means that the 3D information is preserved only two dimensionally with distortions. This paper presents a new 3D documentation, analysis and visualisation approach based on forensic 3D/CAD supported photogrammetry (FPHG) and the use of a 3D surface scanner. Our photogrammetric approach and the used visualisation method is, to the best to our knowledge, the first 3D approach for bite mark analysis in an actual case. The documentation has no distortion artifacts as can be found with standard photography. All the data are documented with a metric 3D measurement, orientation and subsequent analysis in 3D space. Beside the metrical analysis between bite mark and cast, it is possible using our method to utilise the topographical 3D feature of each individual tooth. This means that the 3D features of the biting surfaces and edges of each teeth are respected which is-as shown in our case-very important especially in the front teeth which have the first contact to the skin. Based upon the 3D detailed representation of the cast with the 3D topographic characteristics of the teeth, the interaction with the 3D documented skin can be visualised and analysed on the computer screen. #

Virtopsy: Expert opinion based on 3d surface and radiological scanning and documentation in forensic medicine

2008

Apart from forensic medical examinations (external examination and autopsy), three-dimensional technologies and high-tech methods are gaining more and more importance in accident and crime investigations. Radiological imaging and 3D surface scanning deliver highly precise 3D data of accident victims and damaged vehicles. Based on these digital data computer-assisted, drawn-to-scale analysis of the injuries of the body and damages to the vehicle allow for the reconstruction of the course of accident. In the present work a collision between a car and a cyclist was analyzed with the described methods. The body of the accident victim was scanned with MSCT and 3D optical surface scanning. The accident car and the bicycle were also digitized with the surface scanner. The accident scene was documented by the use of a 3D laser scanner and photogrammetry. With the real data based reconstruction the collision position of the vehicles and the course of the accident could be determined. Furthermore, an external institution used the collected data to estimate the velocity of the car at time of collision.

Forensic 3D documentation of bodies: Simple and fast procedure for combining CT scanning with external photogrammetry data

A B S T R A C T This study presents a procedure for combining 3D models obtained from CT scanning (internal and external data) and photogrammetry (external data). 3D data were acquired at different times, without the support of reference points. The procedure has been tested on 30 injured areas caused by different wounding mechanisms. The alignment of the different 3D models was in most of the cases very precisely (mean distance around 1 mm, SD around or lower than 2 mm). Ad hoc procedures should be followed in case of injuries on the head, joints and back.