Documenting 3D Surfaces in Forensic Pathology

Abstract

Two three-dimensional surface technologies close-range photogrammetry and optical surface scanning have lately evolved into procedures that are more versatile, less expensive, and more precise. Yet, the promise of these techniques has not yet been completely realized in the routine of forensic post-mortem inquiry. In the present investigation, we contrasted the performance of stereophotogrammetry-based Vectra H11, a portable handheld surface scanner, and digital camera-based photogrammetry coupled with industry-standard Agisoft PhotoScan1 software. A 25-year-old woman who was still alive and two 63-year-old male forensic cases who had been admitted for post-mortem examination at the Department of Forensic Medicine in Hradec Králové, Czech Republic, were the subjects of the study. One of the men had died from traumatic, self-inflicted injuries (suicide by hanging), and the other had been diagnosed with heart failure. All three examples were captured simultaneously using a Nikon 7000 digital camera and a handheld scanner in 3608 styles. Both techniques were employed to record the pre-autopsy phase of the forensic cases as well as at various stages of the autopsy. The collected sets of digital pictures underwent additional processing to produce point clouds and 3D meshes (around 100 in each case). One pair of points and polygons from each person's final 3D model was counted. Then, using the ICP alignment algorithm and a cloud point comparison method based on the nearest point-to-point distances, they were assessed visually and statistically.

Introduction

Verbal description combined with two-dimensional photography is the gold standard for post-mortem inspection, utilised to record the corpse's state of preservation, the presence of distinctive somatic features, external and internal injuries, and/or pathological abnormalities. The meticulous and exact documentation of the initial pre-autopsy state, perishable findings, and sequential steps of an autopsy are essential for the preservation of forensic evidence as well as the capacity for other specialists to review the initial conclusions, prevent misdiagnoses, and uphold a high level of quality control.

3D Surface Documentation

It is well recognized that 2D photography falls short on a number of fronts when compared to 3D surface documentation. It gives physical evidence a three-dimensional representation in which all three dimensions are equally present and unaltered. 3D surface data are ideally suited to be the subject when comparing various types of forensic evidence, such as pattern injuries against injury-inflicting tools in weapon analysis, bone injuries, identification, or advanced morphometric analysis.

Many technologies with relatively steep learning curves can be used to perform modern three-dimensional surface documentation. The human body may be measured using technologies such as radio sources, laser or white light scanning, passive photogrammetry, video imaging with infrared sensors, or touch measurement. Laser beams are used in laser surface scanners to scan the surface slowly before reflecting back to a light sensor For the majority of systems, the method requires that the scanned object remain immobile for a longer period of time. While examining crime scenes, bodies, and skeletal remains, as well as other sorts of forensic evidence like weapons (a shotgun, a knife), or personal things, this is possible but not advised when working with living individuals. One of the main drawbacks of laser scanning technology is that, absent a device with an optical camera system, such as NextEngine, or the application of the texture to the surface using an appropriate editing program, such as Meshlab, the resulting 3D digital models lack information about the original texture coloring.

3D Optical Surface Scanning

In contrast, 3D optical surface scanning systems take images of the object's surface reflecting light from different angles using two or more optical camera units (passive photogrammetry). Surface depth information may then be altered and high-resolution texture added by computing 3D surface points using digital images collected by converged cameras in accordance with fundamental triangulation principles. Alternately, they are made up of a camera system and a projection device that emits structured light, like a pattern or a succession of patterns, and whose images are then recorded on the surface. The distortion of the light pattern and the camera calibration settings are the sources of depth data. The stereo-photogrammetry procedure, which is easily achieved with dead human bodies but offers minimal difficulty or discomfort when photographing living humans, just requires a second or two for the scanned object to be motionless. Structured light-based sensors, such as ATOS scanners, require more regulated environments since they create high-resolution surface data of various volumes. This is helpful in forensic pathology, where it may be necessary to document a whole body or a moderately impressed skull fracture on a regular basis.

Submission link:- https://www.iomcworld.com/forensic-pathology/submit-manuscript.html