不同方法测量不规则瘢痕面积的比较

目的对比不同测量方法在测量不规则瘢痕面积时的优缺点,以确定不规则瘢痕面积测量标准。方法对不规则瘢痕面积进行数字化扫描,运用坐标纸读取法、Auto CAD像素法、Photoshop套索像素法、Photoshop魔棒填充像素法及福昕PDF阅读软件测量法进行测量,从测量时间、可重复性、是否可以全程记录及是否可以溯源等方面进行比较分析。结果采用上述瘢痕面积测量方法的结果差异无统计学意义,但在测量时间、同一人多次重复性及多人测量可重复性上差异存在统计学意义,仅福昕PDF阅读软件可以溯源。结论上述方法均可应用于瘢痕测量,但是各有利弊,还需针对司法鉴定开发新的测量软件。     

结构光三维扫描技术测量损伤瘢痕的法医学应用

目的验证结构光三维扫描技术测量体表规则或不规则损伤瘢痕的长度和面积的准确性与可靠性,探讨其法医学应用价值。方法采用软尺、游标卡尺+细线法、结构光三维扫描法分别对30例模拟条状瘢痕与50例伤后条状瘢痕的长度进行测量,以长×宽、薄膜描记结合坐标纸法、像素法、结构光三维扫描法分别测量35例模拟片状瘢痕及15例伤后片状瘢痕的面积,并进行统计学分析。结果结构光三维扫描法测量的模拟条状瘢痕长度与标准长度差异无统计学意义;对表面曲率较大且大面积不规则模拟片状瘢痕和伤后片状瘢痕进行测量时,结构光三维扫描法测量结果与标准面积差异无统计学意义。使用结构光三维扫描法对50例伤后条状瘢痕长度进行测量时,两名操作人员测量结果的相关系数为0.998,同一操作者两次测量结果的相关系数为1.000,与游标卡尺+细线法测量结果的相关系数为0.996。结论采用结构光三维扫描技术测量可获取体表瘢痕的立体信息,对瘢痕长度和面积的测量不受部位、体表曲率及人为因素的影响,测量结果准确可靠,具有独特的优势。     

三维测量法在体表损伤法医学鉴定中的研究及应用

目的通过三维扫描技术法,实现精确体表损伤瘢痕的表面积与长度,探讨其法医学鉴定中的应用价值。方法采用定制的结构光三维扫描仪采集体表损伤三维数据,通过多视角正交法点选损伤区域,跨网格抗锯齿优化,自动计算表面积。结果测量结果对比工业级Geomagic Studio在同一标准件扫描和计算误差在毫米小数点后两位。结论采用三维测量对体表损伤表面积测量结果精确可靠,并可适用于不规则的器官和表面损伤测量,提高法医学鉴定的准确性。     

应用CT三维重组技术判定胸骨性别的研究

目的建立利用三维重组形态学指标判定胸骨性别来源的方法,并对其判定效果进行评价,考察虚拟骨骼的法医学应用价值。方法应用胸部螺旋CT扫描图像,通过多层面重组法获取胸骨的二维影像,结合容积再现技术得出的三维模型,分别测量胸骨的全长、柄长、体长、柄最大宽、体最大宽、柄最大厚、体最大厚、体上端厚等8项指标,并计算出3个比值指标;筛选出其中有性别差异的指标,建立性别判别方程并评价其判别效果。结果 11个指标的性别差异均具有统计学意义(P0.05),但以胸骨全长、胸骨体长、体最大厚及柄最大宽的判别效果较好。所建方程组中,全指标、长度指标判别方程及逐步判别方程的判别率较高,88.6%的判定率与近期国外有关性别判定研究的报道结果基本一致。结论应用多层螺旋CT三维重组技术判定国人胸骨性别具有较高的可行性和准确性,该技术有望应用于胸骨年龄推断及其它虚拟骨骼的研究。     

Application of non-contact scanning to forensic podiatry: A feasibility study

Foot impression evidence recovered from crime scenes can be available in the form of barefoot prints, sock-clad footprints, or as impressions within footwear. In some cases, suspects leave their footwear at the scene of the crime, and the insoles from the footwear can be important in linking a person to the footwear. The application of 3D data-collecting technology is becoming more and more popular within forensic science and has been used to recover footwear impression evidence. The present study is a feasibility study to discover if 3D data capturing devices can be applied to insoles; to capture the footprint impression for measurement using the Gunn method (a method used in forensic podiatry casework). Three different methods of data capture were conducted; Adobe Photoshop, MeshLab, and calipers used directly on the insole. Paired t-tests and Intraclass Correlation Coefficient (ICC) were conducted for all three data capture methods. Seven measurements used in this study were significantly different across all three methods. ICC scores were moderate to excellent for the Photoshop method, poor to good for the 3D method, and moderate to excellent for the Direct method.     

Photogrammetric Documentation of Regions of Interest at Autopsy—A Pilot Study

In this pilot study, the authors tested whether photogrammetry can replace or supplement physical measurements made during autopsies and, based on such measurements, whether virtual computer models may be applicable in forensic reconstructions. Photogrammetric and physical measurements of markers denoting wounds on five volunteers were compared. Virtual models of the volunteers were made, and the precision of the markers' locations on the models was tested. Twelve of 13 mean differences between photogrammetric and physical measurements were below 1 cm, which indicates that the photogrammetric method has a high accuracy. The precision of the markers' location on the models was somewhat less, although the method is still promising and potentially superior to the current procedures used for reconstructions. The possibility to measure any distance on a body, even after the autopsy is concluded and the corpse is no longer available, is one of the biggest benefits of photogrammetry.     

Photogrammetry vs CT Scan: Evaluation of Accuracy of a Low-Cost Three-Dimensional Acquisition Method for Forensic Facial Approximation

Photogrammetry is a three-dimensional acquisition method potentially applicable to the forensic field. This possibility requires the verification of its accuracy. In this study, 3D volumes of skulls are generated to compare the photogrammetry versus the CT scan. In order to provide eligible material to the photogrammetric software, photographs were captured at a distance of 30 cm from the skull placed on a support 1 m in height and illuminated with diffused laboratory ceiling artificial light. A Nikon Coolpix P7100 camera was used. Photographs capture common elements with the previous and the next photograph so as to allow the photogrammetric software to recognize these common points between photographs and create a 3D puzzle. The Zephyr Lite (3DFlow©) software was employed to register the 3D volume. CT-based skulls are taken as a metric reference. The photogrammetry-based skulls are then enlarged according to the measurements of some landmarks or Zygion and Zygion, the distance between end of nasal and base of nasal pyramid for frontal projection, and minimum breadth of the mandibular ramus for the right lateral projection. The accuracy of the photogrammetry is compared to that of the CT scan by measuring the 3D volumes of the skulls studied. Specific landmarks are used as reference points for the measures in both frontal and lateral views. Bland–Altman graph shows homogeneity. The mean difference (1.28 mm) indicates that the measurements taken on the photogrammetry-based skull tend to slightly overestimate compared with the measurements taken on the CT-based skull.     

Forensic Terrestrial Photogrammetry from a Single Image

Abstract:  Forensic terrestrial photogrammetry is one of the most valuable and low-cost resources of spatial data available today. Due to the ephemeral crime scene characteristics, these photographs can often capture information that is never to be seen again. This paper presents a novelty approach for the documentation, analysis, and visualization of crime scenes for which only a single perspective image is available. The photogrammetric process consists of a few well-known steps in close-range photogrammetry: features extraction, vanishing points computation, camera self-calibration, 3D metric reconstruction, dimensional analysis, and interactive visualization. Likewise, the method incorporates a quality control of the different steps accomplished sequentially. As a result, several cases of study are presented in the experimental results section in order to test their viability. The full approach can be applied easily through the free software, sv3DVision, which has been evaluated by a number of police officers, forensic scientists, and forensic educators satisfactorily.     

Empirical Evaluation of the Reliability of Photogrammetry Software in the Recovery of Three-Dimensional Footwear Impressions

This paper examines the reliability of Structure from Motion (SfM) photogrammetry as a tool in the capture of forensic footwear marks. This is applicable to photogrammetry freeware DigTrace but is equally relevant to other SfM solutions. SfM simply requires a digital camera, a scale bar, and a selection of oblique photographs of the trace in question taken at the scene. The output is a digital three-dimensional point cloud of the surface and any plastic trace thereon. The first section of this paper examines the reliability of photogrammetry to capture the same data when repeatedly used on one impression, while the second part assesses the impact of varying cameras. Using cloud to cloud comparisons that measure the distance between two-point clouds, we assess the variability between models. The results highlight how little variability is evident and therefore speak to the accuracy and consistency of such techniques in the capture of three-dimensional traces. Using this method, 3D footwear impressions can, in many substrates, be collected with a repeatability of 97% with any variation between models less than ~0.5 mm.     

Determination of average vehicle speed utilizing reverse projection

Reverse projection photogrammetry has long been used to estimate the height of an individual in forensic video examinations. A natural extrapolation would be to apply the same technique on a video to estimate the speed of an object by determining the distance traveled between two points over a set amount of time. To test this theory, five digital video recorders (DVRs) were connected to a single fixed camera to record a vehicle traveling down a track. The vehicle's speed was measured through Doppler radar by a trained operator and the speedometer of the vehicle was also recorded with a video camera. The recorded video was examined and the frames that best depict the beginning and end of the vehicles course were selected. Two reverse projection photogrammetric examinations were performed on the selected frames to establish the position of the vehicle. The distance between the two points was measured, and the time elapsed between the two points was examined. The outcome provided an accurate speed result with a standard degree of uncertainty. This study proves the feasibility of using video data and reverse projection photogrammetry to determine the speed of a vehicle with a limited set of variables. Further research is needed to determine how additional variables would impact the standard degree of uncertainty.     

颅内出血体积测量方法的比较

目的探寻一种能够运用于法医临床学实践的测量颅内出血量的方法。方法比较多田公式、体视学技术和软件边界法测量颅内出血的准确性,并比较它们的实用性。结果体视学法和软件边界法的测量值是准确的,而多田公式测量不规则血肿误差很大。结论体视学法是法医临床学中测量颅内出血量最适用的方法。