Jernigan S R, Buckner G D, Eischen J W, Cormier D R
Department of Mechanical and Aerospace Engineering, North Carolina State University, NCSU Box 7910, Raleigh, NC 27695, USA.
J Biomech Eng. 2007 Dec;129(6):825-37. doi: 10.1115/1.2801650.
With the worldwide prevalence of cardiovascular diseases, much attention has been focused on simulating the characteristics of the human heart to better understand and treat cardiac disorders. The purpose of this study is to build a finite element model of the left atrium (LA) that incorporates detailed anatomical features and realistic material characteristics to investigate the interaction of heart tissue and surgical instruments. This model is used to facilitate the design of an endoscopically deployable atrial retractor for use in minimally invasive, robotically assisted mitral valve repair. Magnetic resonance imaging (MRI) scans of a pressurized explanted porcine heart were taken to provide a 3D solid model of the heart geometry, while uniaxial tensile tests of porcine left atrial tissue were conducted to obtain realistic material properties for noncontractile cardiac tissue. A finite element model of the LA was constructed using ANSYS Release 9.0 software and the MRI data. The Mooney-Rivlin hyperelastic material model was chosen to characterize the passive left atrial tissue; material constants were derived from tensile test data. Finite element analysis (FEA) models of a CardioVations Port Access retractor and a prototype endoscopic retractor were constructed to simulate interaction between each instrument and the LA. These contact simulations were used to compare the quality of retraction between the two instruments and to optimize the design of the prototype retractor. Model accuracy was verified by comparing simulated cardiac wall deflections to those measured by MRI. FEA simulations revealed that peak forces of approximately 2.85 N and 2.46 N were required to retract the LA using the Port Access and prototype retractors, respectively. These forces varied nonlinearly with retractor blade displacement. Dilation of the atrial walls and rigid body motion of the chamber were approximately the same for both retractors. Finite element analysis is shown to be an effective tool for analyzing instrument/tissue interactions and for designing surgical instruments. The benefits of this approach to medical device design are significant when compared to the alternatives: constructing prototypes and evaluating them via animal or clinical trials.
随着心血管疾病在全球范围内的流行，人们将大量注意力集中在模拟人类心脏的特征上，以便更好地理解和治疗心脏疾病。本研究的目的是建立一个包含详细解剖特征和逼真材料特性的左心房（LA）有限元模型，以研究心脏组织与手术器械之间的相互作用。该模型用于辅助设计一种可通过内镜展开的心房牵开器，用于微创机器人辅助二尖瓣修复手术。对一个加压的离体猪心脏进行磁共振成像（MRI）扫描，以提供心脏几何形状的三维实体模型，同时对猪左心房组织进行单轴拉伸试验，以获取非收缩性心脏组织的逼真材料特性。使用ANSYS Release 9.0软件和MRI数据构建了LA的有限元模型。选择Mooney-Rivlin超弹性材料模型来表征被动左心房组织；材料常数从拉伸试验数据中得出。构建了CardioVations Port Access牵开器和原型内镜牵开器的有限元分析（FEA）模型，以模拟每种器械与LA之间的相互作用。这些接触模拟用于比较两种器械的牵开质量，并优化原型牵开器的设计。通过将模拟的心脏壁挠度与MRI测量的挠度进行比较，验证了模型的准确性。FEA模拟显示，使用Port Access牵开器和原型牵开器分别牵拉LA所需的峰值力约为2.85 N和2.46 N。这些力随牵开器叶片位移呈非线性变化。两种牵开器引起的心房壁扩张和腔室刚体运动大致相同。有限元分析被证明是分析器械/组织相互作用和设计手术器械的有效工具。与替代方法（构建原型并通过动物或临床试验进行评估）相比，这种医疗器械设计方法的优势显著。
