Name: quantification of strain in a porcine model of skin expansion using multi-view stereo and isogeometric kinematics
Uploaded: 2017-04-16T14:00:00
Description: Watch this Scientific Journal Video about Quantification of Strain in a Porcine Model of Skin Expansion Using Multi-View Stereo and Isogeometric Kinematics at JoVE.com

This work was supported by NIH grant 1R21EB021590-01A1 to Arun Gosain and Ellen Kuhl.

This protocol involves animal experiments. The protocol was approved by the IRB of Ann and Robert H. Lurie Children&#39;s Hospital of Chicago Research Center Animal Care and Use Committee to guarantee humane treatment of animals. The results for two expansion studies using this protocol have been published elsewhere 16,31.
Execution of this protocol requires a team with complementary expertise. The first part of the protocol describes ...

<ol>
	<li>Gosain, A. K., Zochowski, C. G., Cortes, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refinements+of+tissue+expansion+for+pediatric+forehead+reconstruction:+a+13-year+experience.">Refinements of tissue expansion for pediatric forehead reconstruction: a 13-year experience.</a> Plast Reconstr Surg. 124, 1559-1570 (2009).</li><li>Neumann, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+expansion+of+an+area+of+skin+by+progressive+distention+of+a+subcutaneous+balloon:+Use+of+the+Method+for+Securing+Skin+for+Subtotal+Reconstruction+of+the+Ear.">The expansion of an area of skin by progressive distention of a subcutaneous balloon: Use of the Method for Securing Skin for Subtotal Reconstruction of the Ear.</a> Plast Reconstr Surg. 19, 124-130 (1957).</li><li>De Filippo, R. 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Here we presented a protocol to characterize the deformations induced during a tissue expansion procedure in a porcine model using multi-view stereo (MVS) and isogeometric kinematics (IGA kinematics). During tissue expansion, skin undergoes large deformations going from a smooth and relatively flat surface to a dome-like 3D shape. Skin, like other biological membranes 34, responds to stretch by producing new material, increasing in area that can be then used for reconstructive purposes <sup class=...

Tissue expansion is a common technique in plastic and reconstructive surgery that grows skin in vivo for the correction of large cutaneous defects 1. Neumann, in 1957, was the first surgeon to document this procedure. He implanted a balloon below the skin of a patient and inflated it gradually over a period of several weeks to grow new tissue and resurface an ear 2. Skin, like most biological tissues, adapts to applied forces and deformations in order to reach mechanical homeostasis. When stretched beyond the physiological regime, skin grows 3,4. One of the central advantages of tissue expansion is the production of skin with proper vascularization and the same hair bearing, mechanical properties, color, and texture as the surrounding tissue 5.
After its introduction six decades ago, skin expansion has been widely adopted by plastic and reconstructive surgeons and is presently used to correct burns, large congenital defects, and for breast reconstruction after mastectomy 6,7. Yet, despite its widespread use, skin expansion procedures can lead to complications 8. This is partly due to the lack of sufficient quantitative evidence needed to understand the fundamental mechanobiology of the procedure and to guide the surgeon during preoperative planning 9,10. Key parameters in this technique are the filling rate, filling volume per inflation, the selection of the shape and size of the expander, and the placement of the device 11,12. Current preoperative planning relies largely on the physician&#39;s experience, resulting in a wide variety of arbitrary protocols that often differ greatly 13,14,15.
To address the current knowledge gaps, we present an experimental protocol to quantify expansion-induced deformation in a porcine animal model of tissue expansion. The protocol relies on the use of multi-view stereo (MVS) to reconstruct three-dimensional (3D) geometries out of sequences of two-dimensional (2D) images with unknown camera positions. Employing splines, representation of smooth surfaces leads to the calculation of the corresponding deformation maps by means of an isogeometric (IGA) description. The analysis of the geometry is based on the theoretical framework of continuum mechanics of membranes having an explicit parameterization 16.
Characterizing physiologically relevant deformations of living materials over long periods of time still remains a challenging problem. Common strategies for imaging of biological tissues include stereoscopic digital image correlation, commercial motion capture systems with reflective markers, and biplane video fluoroscopy 17,18,19. However, these techniques require a restrictive experimental setup, are generally expensive, and have been primarily used for ex vivo or acute in vivo settings. Skin has the advantage of being a thin structure. Even though it consists of several layers, the dermis is largely responsible for the mechanical properties of the tissue and thus the surface deformation is of primary importance 20; reasonable kinematical assumptions can be made regarding the out of plane deformation 21,22. Moreover, skin is already exposed to the outside environment, making it possible to use conventional imaging tools to capture its geometry. Here we propose the use of MVS as an affordable and flexible approach to monitor in vivo deformations of skin over several weeks without interfering majorly with a tissue expansion protocol. MVS is a technique that extracts 3D representations of objects or scenes from a collection of 2D images with unknown camera angles 23. Only in the last three years, several commercial codes have appeared (see list of materials for examples). The high accuracy of the model reconstruction with MVS, with errors as low as 2% 24, makes this approach suitable for the kinematic characterization of skin in vivo over long periods of time.
To obtain the corresponding deformation maps of skin during tissue expansion, points between any two geometric configurations are matched. Conventionally, researchers in computational biomechanics have used finite element meshes and inverse analysis to retrieve the deformation map 25,26. The IGA approach employed here uses spline basis functions which offer several advantages for the analysis of thin membranes 27,28. Namely, the availability of high degree polynomials facilitates representations of smooth geometries even with very coarse meshes 29,30. Additionally, it is possible to fit the same underlying parameterization to all the surface patches, which circumvents the need for an inverse problem to account for non-matching discretizations.
The method described here opens new avenues to study skin mechanics in relevant in vivo settings over long periods of time. In addition, we are hopeful that our methodology is an enabling step towards the ultimate goal of developing computational tools for personalized treatment planning in the clinical setting.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Yucatan miniature swine</td>
			<td style="width:263px;">Sinclair Bioresources, Windham, ME</td>
			<td style="width:141px;">N/A</td>
			<td style="width:197px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Antibiotics</td>
			<td>Santa Cruz Animal Health, Paso Robles, CA</td>
			<td style="width:141px;">sc-362931Rx</td>
			<td>Ceftiofur, dosage 5mg/kg intramuscular</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chlorhexidine-based surgical soap</td>
			<td style="width:263px;">Cardinal Health, Dublin, OH</td>
			<td>AS-4CHGL(4-32)</td>
			<td>4% chlorhexidine gluconate surgical hand scrub</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Tattoo transfer medium&#160;</td>
			<td style="width:263px;">Hildbrandt Tattoo Supply, Point Roberts, WA</td>
			<td>TRANSF</td>
			<td>Stencil thermal tattoo transfer paper</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lidocaine with epinephrine</td>
			<td style="width:263px;">ACE Surgical Supply Co, Brockton, MA</td>
			<td style="width:141px;">001-1423</td>
			<td>Lidocaine Hcl 1% (Xylocaine) - Epinephrine 1:100,000, 20ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Buprenorphine</td>
			<td style="width:263px;">ZooPharm, Windsor, CO</td>
			<td style="width:141px;"></td>
			<td>1 mg/ml sustained release, dosage 0.01 mg/kg intramuscular</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Digital camera</td>
			<td style="width:263px;">Sony</td>
			<td style="width:141px;">Alpha33&#160;</td>
			<td>Standard digital camera with 18-35mm lens, 3.5-5.6 aperture. Used in automatic mode, no flash</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tape measure</td>
			<td style="width:263px;">Medline, Mundelein, Illinois</td>
			<td style="width:141px;">NON171330</td>
			<td>Retractable tape measure, cloth, plastic case, 72inches</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tissue expanders</td>
			<td style="width:263px;">PMT, Chanhassen, MN</td>
			<td style="width:141px;">03610-06-02</td>
			<td>4cm x 6cm, rectangular, 120cc, 3610 series 2 stage tissue expander with standard port</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ReCap360</td>
			<td style="width:263px;">Autodesk</td>
			<td style="width:141px;">N/A</td>
			<td>MVS Software, Web application: recap360.autodesk.com</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blender</td>
			<td style="width:263px;">Blender Foundation</td>
			<td style="width:141px;">N/A</td>
			<td>Computer Graphics Software, open source: blender.org</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SISL</td>
			<td style="width:263px;">SINTEF</td>
			<td style="width:141px;">N/A</td>
			<td>C++ spline libraries, open source: https://www.sintef.no/projectweb/geometry-toolkits/sisl/</td>
		</tr>
	</tbody>
</table>

quantification of strain in a porcine model of skin expansion using multi-view stereo and isogeometric kinematics

Tissue expansion is a popular technique in plastic and reconstructive surgery that grows skin in vivo for correction of large defects such as burns and giant congenital nevi. Despite its widespread use, planning and executing an expansion protocol is challenging due to the difficulty in measuring the deformation imposed at each inflation step and over the length of the procedure. Quantifying the deformation fields is crucial, as the distribution of stretch over time determines the rate and amount of skin grown at the end of the treatment. In this manuscript, we present a method to study tissue expansion in order to gain quantitative knowledge of the deformations induced during an expansion process. This experimental protocol incorporates multi-view stereo and isogeometric kinematic analysis in a porcine model of tissue expansion. Multi-view stereo allows three-dimensional geometric reconstruction from uncalibrated sequences of images. The isogeometric kinematic analysis uses splines to describe the regional deformations between smooth surfaces with few mesh points. Our protocol has the potential to bridge the gap between basic scientific inquiry regarding the mechanics of skin expansion and the clinical setting. Eventually, we expect that the knowledge gained with our methodology will enable treatment planning using computational simulations of skin deformation in a personalized manner.

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. Figure 2 illustrates the three steps of MVS model reconstruction. The starting point is a collection of photographs from a static scene. The animal with the tattooed grids...

Watch this Scientific Journal Video about Quantification of Strain in a Porcine Model of Skin Expansion Using Multi-View Stereo and Isogeometric Kinematics at JoVE.com

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

This protocol uses multi-view stereo to generate three-dimensional (3D) models out of uncalibrated sequences of photographs, making it affordable and adjustable to a surgical setting. Strain maps between the 3D models are quantified with spline-based isogeometric kinematics, which facilitate representation of smooth surfaces over coarse meshes sharing the same parameterization.

Tissue expansion is a popular technique in plastic and reconstructive surgery that grows skin in vivo for correction of large defects such as burns and ...

Research

JoVE Journal

Bioengineering

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