Characterization of living skin using multi-view stereo and isogeometric analysis

Abstract

Skin is our interface with the outside world. In its natural environment, it displays unique mechanical characteristics such as prestretch and growth. While there is a general agreement on the physiological importance of these features, they remain poorly characterized, mainly because they are difficult to access with standard laboratory techniques. Here we present a new, inexpensive technique to characterize living skin using multi-view stereo and isogeometric analysis. Based on easy-to-create hand-held camera images, we quantify prestretch, deformation, and growth in a controlled porcine model of chronic skin expansion. Over a period of five weeks, we gradually inflate an implanted tissue expander, take weekly photographs of the experimental scene, reconstruct the geometry from a tattooed surface grid, and create parametric representations of the skin surface. After five weeks of expansion, our method reveals an average area prestretch of 1.44, an average area stretch of 1.87, and an average area growth of 2.25. Area prestretch is maximal in the ventral region with 2.37, area stretch and area growth are maximal above the center of the expander with 4.05 and 4.81. Our study has immediate impact on understanding living skin to optimize treatment planning and decision making in plastic and reconstructive surgery. Beyond these direct implications, our experimental design has broad applications in clinical research and basic sciences: It serves as a simple, robust, low cost, easy-to-use tool to reconstruct living membranes, which are difficult to characterize in a conventional laboratory setup.

Mathematical and computational modelling of skin biophysics: a review

“…An attractive feature of computational models is the ability to quantify physical parameters required to obtain a specific outcome. For example, Prof. Kuhl's group at Stanford University has pioneered the development of mechanobiological adaptation models for skin to optimize the outcome of reconstructive surgery procedures in children [61][62][63][64][65][66][67] Streamline plots representing the maximum (coloured) and minimum (white) principal strain vectors in a finite deformation 2D plane-strain image-based finite-element model of the skin subjected to 20% in-plane compression (adapted from [20]). Grey arrows indicate the direction and location of the applied load.…”

A mechanistic insight into the mechanical role of the stratum corneum during stretching and compression of the skin

“…A wide array of experimental and clinical measurement techniques are used to characterise particular aspects of skin biology and biophysics (Alexiades-Armenakas, 2007;Batisse et al, 2002;Bellemere et al, 2009;Delalleau et al, 2006;Diridollou et al, 2000;Gunner et al, 1979;Hendriks et al, 2006;Jor et al, 2013;Limbert and Simms, 2013;Tonge et al, 2013a;Tonge et al, 2013b;Wan Abas, 1994). Nevertheless, complementary approaches based on mathematical and computational modelling techniques offer promising avenues to further our understanding of the skin (Areias et al, 2003;Bischoff et al, 2000;Boissieux et al, 2000;Buganza Tepole and Kuhl, 2014;Cavicchi et al, 2009;Duan et al, 2000;Evans, 2009;Flynn and McCormack, 2008a, b;Flynn andMcCormack, 2009, 2010;Hendriks et al, 2006;Hendriks et al, 2003;Kuwazuru et al, 2008;Larrabee and Galt, 1986a, b;Larrabee and Sutton, 1986;Lévêque and Audoly, 2013;Tepole et al, 2014a;Tepole et al, 2014b;Tepole et al, 2011;Zöllner et al, 2013).…”

Quantification of Strain in a Porcine Model of Skin Expansion Using Multi-View Stereo and Isogeometric Kinematics

“…This methodology has been successfully employed to study the deformation induced by different expander geometries: rectangle, sphere and crescent expanders 31,32 . The results corresponding to the sphere and crescent expanders are discussed next.…”

“…Having a protocol to accurately estimate expansion-induced deformation and capable of resolving large strains, 3D shapes, and regional variations, opens new avenues to study the mechanical regulation of skin growth, and can eventually lead to quantitative preoperative planning tools. Towards that goal, we developed a non-invasive, affordable, and flexible methodology to measure deformation in a porcine model of skin expansion 32 .…”

“…If the expanded area moves outside of the grid, the expander should be deflated and removed. This problem has been encountered using the protocol in one out of eight grids 31,32 . Expanders can also leak if they are defective or punctured during the inflation protocol.…”