在皮肤扩张使用多视点立体和Isogeometric运动学的猪模型应变的定量
Summary
该协议使用多视点立体生成三维（3D）模型进行的照片未校准序列，使得它负担得起的和调节的，以在外科手术设置。的3D模型之间应变图与基于样条的isogeometric运动学，其有利于平滑表面过度粗网格共享相同的参数化表示定量。
Abstract
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.
Introduction
组织扩张是在整形外科的常用技术，生长皮肤在体内的皮肤大缺陷1的校正。纽曼于1957年，是记录这个过程的第一个外科医生。他植入患者的皮肤下面的气囊和充气逐渐它在数周长出新的组织及铺设耳2。皮肤，像大多数生物组织，以适应所施加的力和变形，以达到机械平衡。当拉伸超过生理机制，皮肤长3，4。一个的组织扩张的中央优点是生产皮肤用适当的血管化和相同的头发轴承，机械性能，颜色和质地的周围组织5。
其推出的六十年前，皮肤expansio后n具有由塑料和重建外科医生被广泛采用，并且目前用于校正烧伤，大先天性缺陷，和乳房再造术6,7之后。然而，尽管它的广泛使用，皮肤扩张过程可以导致并发症8。这部分是由于缺乏必要了解程序的基本力学生物学，并在术前计划9，10来引导外科医生足够的定量证据。在该技术中的关键参数是填充率，填充每体积膨胀，膨胀的形状和尺寸的选择，并且该装置11，12的位置。目前术前计划主要依靠医生的经验，产生了各种各样的任意的协议，往往不同greatlÿ13，14，15。
为了解决目前的知识缺口，我们提出了一个实验方案来量化在组织扩张的猪动物模型膨胀而引起的变形。该协议依靠使用多视点立体（MVS）来重建三维（3D）几何形状不与未知摄像机位置的二维（2D）图像的序列。使用样条曲线，光滑的表面的表示由isogeometric（IGA）描述的方法导致了相应的变形地图的计算。几何形状的分析是基于在具有明确的参数16的膜的连续介质力学的理论框架。
表征生活过很长一段时间的材料有关生理变形仍然是一个具有挑战性的问题。为共同战略生物组织的成像包括立体数字图像相关，具有反射标记的商业动作捕捉系统，和双平面视频透视17，18，19。然而，这些技术要求限制性的实验设置，一般是昂贵的，并已被主要用于离体或在体内设置尖锐。皮肤具有作为薄的结构的优点。即使它由若干层组成，真皮是用于组织的机械性质并在很大程度上负责因此表面变形是最重要的20;合理的运动学假设可以对于出平面变形21,22制成。此外，皮肤已经暴露在外部环境，使其能够使用传统的成像工具来捕捉它的几何形状。 HERE我们建议使用MVS的作为负担得起的和灵活的方法来监测皮肤在数周内体内变形而没有与组织扩张协议majorly干扰。 MVS是提取对象或场景的三维表示从二维图像的具有未知相机集合角23的技术。仅在过去的三年里，一些商业代码已经出现（见的实例，材料清单）。模型重建MVS的精度高，但有错误低至2％24，使得这种方法适用于体内在长时间皮肤的运动表征。
到组织膨胀期间获得皮肤的相应的变形地图，任意两个几何构型之间的点匹配。以往，研究人员在计算生物力学已经使用有限元网格和逆分析来检索变形图25，26。此处使用的IGA方法使用，其对于薄的膜27，28的分析提供若干优点样条基函数。即，高次多项式的可用性有助于平滑地几何形状的表示，即使具有非常粗网格29,30。另外，也能够配合在相同的基础参数的所有表面补丁，规避该需要一种逆问题考虑到不匹配的离散化。
这里介绍的方法开辟了新的途径，在很长一段时间来研究有关皮肤力学体内设置。此外，我们希望，我们的方法是在开发针对在临床上的个性化治疗计划的计算工具的最终目标关键的一步。</ P>
Protocol
Representative Results
Discussion
在这里，我们提出了一个协议来表征在使用多视点立体（MVS）和isogeometric运动学（IGA运动学）猪模型的组织膨胀过程期间引起的变形。期间的组织扩张，皮肤经受大的变形从光滑和相对平坦的表面要圆顶状3D形状。皮肤，像其他生物膜34，响应通过产生新的材料伸展，在区域可随后用于重建目的35增加。因此，通过膨胀机所产生的拉伸的精确测定是至关重要?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
This work was supported by NIH grant 1R21EB021590-01A1 to Arun Gosain and Ellen Kuhl.
Materials
| Yucatan miniature swine | Sinclair Bioresources, Windham, ME | N/A | |
| Antibiotics | Santa Cruz Animal Health, Paso Robles, CA | sc-362931Rx | Ceftiofur, dosage 5mg/kg intramuscular |
| Chlorhexidine-based surgical soap | Cardinal Health, Dublin, OH | AS-4CHGL(4-32) | 4% chlorhexidine gluconate surgical hand scrub |
| Tattoo transfer medium | Hildbrandt Tattoo Supply, Point Roberts, WA | TRANSF | Stencil thermal tattoo transfer paper |
| Lidocaine with epinephrine | ACE Surgical Supply Co, Brockton, MA | 001-1423 | Lidocaine Hcl 1% (Xylocaine) – Epinephrine 1:100,000, 20ml |
| Buprenorphine | ZooPharm, Windsor, CO | 1 mg/ml sustained release, dosage 0.01 mg/kg intramuscular | |
| Digital camera | Sony | Alpha33 | Standard digital camera with 18-35mm lens, 3.5-5.6 aperture. Used in automatic mode, no flash |
| Tape measure | Medline, Mundelein, Illinois | NON171330 | Retractable tape measure, cloth, plastic case, 72inches |
| Tissue expanders | PMT, Chanhassen, MN | 03610-06-02 | 4cm x 6cm, rectangular, 120cc, 3610 series 2 stage tissue expander with standard port |
| ReCap360 | Autodesk | N/A | MVS Software, Web application: recap360.autodesk.com |
| Blender | Blender Foundation | N/A | Computer Graphics Software, open source: blender.org |
| SISL | SINTEF | N/A | C++ spline libraries, open source: https://www.sintef.no/projectweb/geometry-toolkits/sisl/ |
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