Urbanová Petra, Hejna Petr, Jurda Mikoláš
Laboratory of Morphology and Forensic Anthropology, Department of Anthropology, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic.
Department of Forensic Medicine, Faculty of Medicine, Charles University in Prague and University Hospital Hradec Králové, Sokolská 581, 500 05 Hradec Králové, Czech Republic.
Forensic Sci Int. 2015 May;250:77-86. doi: 10.1016/j.forsciint.2015.03.005. Epub 2015 Mar 17.
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 PhotoScan(®) software and stereophotogrammetry-based Vectra H1(®), 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 Králové, 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 360° 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 20min, the post-processing was much more time-demanding and required up to 10h 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.
三维表面技术，特别是近景摄影测量和光学表面扫描，最近已发展成为经济实惠、灵活且精确的技术。然而，日常进行的法医尸检尚未充分利用其潜力。在本文中，我们测试了两种三维体表记录方法——基于数码相机的摄影测量结合商业Agisoft PhotoScan（®）软件以及基于立体摄影测量的Vectra H1（®）便携式手持式表面扫描仪。为开展该研究，选取了三名受试者，一名在世的25岁女性，以及两例在捷克共和国赫拉德茨克拉洛韦法医学系接受尸检的法医案例（均为63岁男性），一例死于外伤性自伤（上吊自杀），另一例诊断为心力衰竭。所有三个案例均使用尼康7000数码相机以360°方式拍摄，并同时用手持式扫描仪记录。除记录法医案例的尸检前阶段外，这两种技术还应用于尸检的各个阶段。收集到的数字图像集（每个案例约100张）进一步处理以生成点云和平滑网格。最终的三维模型（每人一对）计算点数和多边形数量，然后进行视觉评估，并使用ICP对齐算法和基于点到点最短距离的点云比较技术进行定量比较。事实证明，这两种技术都易于操作且同样费力。尸检时采集图像大约需要20分钟，而后期处理则耗时得多，需要长达10小时的计算时间。此外，对于全身扫描，手持式扫描仪的后期处理需要相当耗时的手动图像对齐。在所有情况下，所应用的方法都生成了高分辨率、逼真、实际尺寸或易于校准的三维表面模型。当扫描的身体表面覆盖有毛发或有反光潮湿区域时，这两种方法同样失效。尽管如此，可以得出结论，单相机近景摄影测量和使用Vectra H1扫描仪的光学表面扫描代表了成本相对较低的解决方案，已证明对法医病理学中的尸体记录有益。
