RELAST
Development of a system for detecting reduced hypertrophy during scar formation
Project context
As part of the joint project “Promoting atrophic scar repair with elastin mRNA-based therapeutics” a measurement system was developed to detect reduced hypertrophy during scar formation. In clinical research, subjective scales are still frequently used to assess scars [1–3]. In recent years, the use of stereoscopic imaging techniques has been proposed [4]; however, previous approaches were either not accurate enough or not practical for real-world use.
Imaging system
The goal was to develop a robust, practical system capable of capturing the spatial structure of scar tissue. For this purpose, a camera system with an integrated lighting unit was developed that automatically illuminates the field of view from four different directions and captures an image for each direction. The acquisition cycle takes less than one second and enables measurement of parameters that correlate with scar hypertrophy.
Computer vision and analysis
The computations are based on the shape-from-shading method [5]. The method assumes constant illumination from defined directions – ensured by the device design. In addition, a continuous surface is assumed, which is generally true for scar tissue. More challenging is the assumption of constant albedo, i.e., uniform light reflection from the surface [6]. Since skin surfaces can be smooth and reflective, we evaluated whether image correction methods enable consistent analysis.
The generated images are homogenized and form the basis for algorithms that quantify skin structure and hypertrophy of the scar tissue. This approach enables an objective assessment of scar structure that can be compared with clinical data.
3D visualization of measurement results
The hardware development of the measurement system for detecting reduced hypertrophy was successfully completed. The system is available to clinical research under laboratory conditions to precisely measure scar structures and their conspicuousness. Functionality has been demonstrated on sample specimens.
Example of 3D visualization of the achieved measurement results
Download and funding
The full report is available at: TIB – Development of a measurement system for scars (final report)
Funded under reference E! 12338 RELAST by: the Eurostars-2 joint programme with co-funding from the European Union Horizon 2020 research and innovation programme.
References
- Beausang E, Floyd H, Dunn KW, Orton CI, Ferguson MW. A new quantitative scale for clinical scar assessment. Plast Reconstr Surg. (1998) 102:1954–61.
- van de Kar AL, Corion LUM, Smeulders MJC, Draaijers LJ, van der Horst CMAM, van Zuijlen PPM. Reliable and feasible evaluation of linear scars by the patient and observer scar assessment scale. Plast Reconstr Surg. (2005) 116:514–22.
- Verhaegen PDHM, van der Wal MBA, Middelkoop E, van Zuijlen PPM. Objective scar assessment tools: a clinimetric appraisal. Plast Reconstr Surg. (2011) 127:1561–70. doi: 10.1097/PRS.0b013e31820a641a.
- Peake M, Pan K, Rotatori RM, Powell H, Fowler L, James L, Dale E. Incorporation of 3D stereophotogrammetry as a reliable method for assessing scar volume in standard clinical practice. Burns. 2019 Nov;45(7):1614–1620.
- Zhang R, Tsai P, Cryer J, Shah M. Shape from Shading: A Survey. IEEE Transactions on PAMI, 21(08), Aug 1999, pp. 690–706.
- Pentland AP. Local shading analysis. IEEE Transactions on Pattern Analysis and Machine Intelligence, 6:170–187, 1984.