ABSTRACT
Objective To assess the accuracy and reliability of the two 3D measuring methods, structured-light scanning and single-camera photogrammetry in forensic body surface damage and scar measurement. Methods The measuring results of 86 injuries by the ruler method, structured-light scanning and single-camera photogrammetry were compared and evaluated. The area measuring results of 13 simulated scars by the structured-light scanning, single-camera photogrammetry, Photoshop lasso pixel method and PDF reading software were compared and evaluated. The time consumed was recorded. The known specification information of the stickers was used as the standard value to compare the measuring accuracy of the ruler method, structural-light scanning and single-camera photogrammetry, and to calculate the root mean square error （RMSE）. The consistency evaluation of intraclass correlation coefficient （ICC） for the repeatability of 3 measuring results obtained by different operators and the same operator. Results The differences in results of the two 3D measuring methods and the ruler method had no statistical significance; the differences between measuring results made by the structured-light scanning, single-camera photogrammetry and PDF reading software and that of the Photoshop lasso pixel method had no statistical significance. The post-processing of the single-camera photogrammetry consumed more time than that of other methods. When the long-distance group （10-40 cm） was measured, the results obtained by the ruler method were shorter than the standard value. The RMSE value results were structured-light scanning < single-camera photogrammetry < ruler method. The ICC value intragroup and intergroup were greater than 0.99. Conclusion Both structured-light scanning and single-camera photogrammetry can be applied in recording and measuring forensic body surface damage. The former has better performance in measurement accuracy and stability, while the latter has better color performance but longer post-processing time.
Subject(s)
Humans , Cicatrix , Imaging, Three-Dimensional , Photogrammetry , Reproducibility of Results , SoftwareABSTRACT
Objective To study the mechanism of rib fracture caused by landing on different parts of the trunk using finite element method, and to provide some new techniques and new ideas for the reconstruction of the whole process of falls from height. Methods The finite element method was used to study the rib fracture of human security model THUMS4.0 caused by landing on different parts of the trunk. Then the model was compared with actual cases and the mechanism of rib fracture caused by falls from height was analyzed from a biomechanical point of view. Results There were some differences in the stress and strain distribution as well as the rib fracture sites when different parts touched the ground. Ribs on both sides of the body were fractured when the front of the trunk touched the ground, and the fractures were mainly located in the junction of the ribs and costal cartilage and the midaxillary line area. When the right anterior part of the trunk touched the ground, rib fracture occurred first on the side that touched the ground, and rib fractures were mainly located in the area from the right midaxillary line to the posterior axillary line, and junction of ribs on both sides and costal cartilage. When the back of the trunk touched the ground, the fracture sites were mainly located on the back of the ribs on both sides. When the right posterior part of the trunk touched the ground, multiple rib fractures were likely to occur in the parts that touched the ground. The plastic strains were mainly concentrated at the fracture sites, while the von Mises stresses were not only concentrated at the fracture sites, but also at other sites. Conclusion There are some differences in rib fracture location sites and injury mechanisms when different parts of the trunk touch the ground.