A Mobile Robotic Approach to Autonomous Surface Scanning in Legal Medicine

TL;DR

The paper presents a mobile autonomous RGB-D surface-scanning robot for external documentation in legal medicine, addressing limitations of fixed installations. By integrating a UR3 arm on a differential-drive base with an RGB-D camera and using configuration-space analysis, the system autonomously selects scanning paths to maximize body-surface coverage while minimizing time. Experimental results show that three robot-base positions yield around 94–97% coverage across body models, with real-world lab and clinical evaluations achieving roughly 91–97% coverage and mean surface-distance errors around 7 mm, demonstrating practical viability and potential to reduce manual workload. This approach complements PMCT-based internal documentation and holds promise for more efficient, autonomous, and scalable legal medicine workflows.

Abstract

Purpose: Comprehensive legal medicine documentation includes both an internal but also an external examination of the corpse. Typically, this documentation is conducted manually during conventional autopsy. A systematic digital documentation would be desirable, especially for the external examination of wounds, which is becoming more relevant for legal medicine analysis. For this purpose, RGB surface scanning has been introduced. While a manual full surface scan using a handheld camera is timeconsuming and operator dependent, floor or ceiling mounted robotic systems require substantial space and a dedicated room. Hence, we consider whether a mobile robotic system can be used for external documentation. Methods: We develop a mobile robotic system that enables full-body RGB-D surface scanning. Our work includes a detailed configuration space analysis to identify the environmental parameters that need to be considered to successfully perform a surface scan. We validate our findings through an experimental study in the lab and demonstrate the system's application in a legal medicine environment. Results: Our configuration space analysis shows that a good trade-off between coverage and time is reached with three robot base positions, leading to a coverage of 94.96 %. Experiments validate the effectiveness of the system in accurately capturing body surface geometry with an average surface coverage of 96.90 +- 3.16 % and 92.45 +- 1.43 % for a body phantom and actual corpses, respectively. Conclusion: This work demonstrates the potential of a mobile robotic system to automate RGB-D surface scanning in legal medicine, complementing the use of post-mortem CT scans for inner documentation. Our results indicate that the proposed system can contribute to more efficient and autonomous legal medicine documentation, reducing the need for manual intervention.

Figures (6)

• Figure 1: General System Setup: Schematic drawing of the mobile scanning setup (left) and the corresponding scanning workflow (right)
• Figure 2: Workspace Constraints: different workspace constraints investigated in the experiments. Full workspace (left), narrow room (middle) and access from only one side (right)
• Figure 3: Lab: Lab environment (left) with autonomous scanning system and body phantom used for surface scanning. The investigated areas of starting positions for surface scanning are shown in (b)
• Figure 4: Lab: Example of an acquired surface scan after stitching. The reference surface acquired with the hand scanner (a) is shown as well as a surface scan using only one robot base position (b) and using all robot base positions (c). In (d) a color comparison regarding the absolute surface distance to the hand-scanned reference surface is shown
• Figure 5: Legal Medicine: acquired surface scans for three different corpses. (a,e,i) show the surface extracted from the CT scan, (b,f,j) a surface scan from a single robot base position and (c,g,k) the surface scan using several robot base positions. In (d,h,l) a color comparison regarding the absolute surface distance to the registered CT-surface is shown