Journal for Modeling in Ophthalmology最新文献

英文中文

An imaged-based inverse finite element method to determine in-vivo mechanical properties of the human trabecular meshwork. 一种基于图像的反演有限元法确定人体小梁网的体内力学特性。

Q4 Medicine

Journal for Modeling in Ophthalmology

Pub Date : 2017-01-01

Anup D Pant, Larry Kagemann, Joel S Schuman, Ian A Sigal, Rouzbeh Amini

Aim: Previous studies have shown that the trabecular meshwork (TM) is mechanically stiffer in glaucomatous eyes as compared to normal eyes. It is believed that elevated TM stiffness increases resistance to the aqueous humor outflow, producing increased intraocular pressure (IOP). It would be advantageous to measure TM mechanical properties in vivo, as these properties are believed to play an important role in the pathophysiology of glaucoma and could be useful for identifying potential risk factors. The purpose of this study was to develop a method to estimate in-vivo TM mechanical properties using clinically available exams and computer simulations.

Design: Inverse finite element simulation.

Methods: A finite element model of the TM was constructed from optical coherence tomography (OCT) images of a healthy volunteer before and during IOP elevation. An axisymmetric model of the TM was then constructed. Images of the TM at a baseline IOP level of 11, and elevated level of 23 mmHg were treated as the undeformed and deformed configurations, respectively. An inverse modeling technique was subsequently used to estimate the TM shear modulus (G). An optimization technique was used to find the shear modulus that minimized the difference between Schlemm's canal area in the in-vivo images and simulations.

Results: Upon completion of inverse finite element modeling, the simulated area of the Schlemm's canal changed from 8,889 µm² to 2,088 µm², similar to the experimentally measured areal change of the canal (from 8,889 µm² to 2,100 µm²). The calculated value of shear modulus was found to be 1.93 kPa, (implying an approximate Young's modulus of 5.75 kPa), which is consistent with previous ex-vivo measurements.

Conclusion: The combined imaging and computational simulation technique provides a unique approach to calculate the mechanical properties of the TM in vivo without any surgical intervention. Quantification of such mechanical properties will help us examine the mechanistic role of TM biomechanics in the regulation of IOP in healthy and glaucomatous eyes.

目的:以往的研究表明，青光眼的小梁网(TM)与正常眼睛相比机械硬化。我们认为，颞叶僵硬度升高会增加房水流出的阻力，导致眼内压(IOP)升高。在体内测量TM的力学特性将是有利的，因为这些特性被认为在青光眼的病理生理中起重要作用，并可能有助于识别潜在的危险因素。本研究的目的是开发一种方法，通过临床可用的检查和计算机模拟来估计体内TM的力学特性。设计:逆向有限元模拟。方法:利用健康志愿者眼压升高前后的光学相干断层扫描(OCT)图像建立眼动膜有限元模型。建立了TM的轴对称模型。眼压基线水平为11时的TM图像和眼压升高至23 mmHg时的TM图像分别作为未变形和变形的图像处理。随后使用逆建模技术来估计TM剪切模量(G)。使用优化技术来找到剪切模量，使体内图像和模拟中施勒姆氏管面积之间的差异最小化。结果:逆向有限元建模完成后，施莱姆氏管的模拟面积从8,889µm2变化到2,088µm2，与实验测量的施莱姆氏管面积变化(从8,889µm2到2,100µm2)相似。剪切模量计算值为1.93 kPa(杨氏模量约为5.75 kPa)，与之前的离体测量值一致。结论:结合成像和计算模拟技术为计算TM的体内力学特性提供了一种独特的方法，无需任何手术干预。这些力学特性的量化将有助于我们研究TM生物力学在健康眼和青光眼IOP调节中的机制作用。

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