超声弹性成像应用在角膜疾病诊断中的有限元分析

弹性成像在医学成像领域具有广阔的应用前景．在本文中，有限元法被用于模拟角膜组织的超声弹性成像，通过改变角膜病变组织与正常组织杨氏模量的数值大小及分布，模拟角膜病变的不同情形，分析计算各种不同情形时的应变、应力和位移分布，并对仿真结果进行分析．当角膜正常组织与病变组织的杨氏模量之比为1:4时，病变区域中心的应变为-0.00854，而对应正常角膜相同位置的应变为-0.02277，为病变区域中心的应变值的2.67倍．病变区域中心的应力为0.04337，而对应正常角膜相同位置的应力为0.02729，相当于病变区域中心的应力值的0.64倍．当角膜正常组织与病变组织的杨氏模量之比为4:1时，情况刚好相反．基于角膜组织的粘弹性，优化了角膜组织模型．结果表明，利用应变压缩方法可以实现离体组织的弹性成像，超声弹性成像中病变组织与正常组织的生物力学响应差异明显，研究结果可为弹性成像在眼科临床应用上提供理论指导．

Finite Element Analysis of Ultrasound Elastography in the Diagnosis of Corneal Diseases

Elastography has broad application prospects in the field of medical imaging. Ultrasound elastography of corneal tissue was simulated by the finite element method in this article. The different situations of corneal disease were simulated by changing the magnitude and distribution of the Young's modulus of the corneal diseased tissue as well as the normal tissues. In this way, the strain, stress and displacement distribution in various situations were calculated and analyzed. The results showed that when the ratio of Young's modulus of the normal corneal tissue to that of the diseased tissue is 1:4, the strain at the center of the lesion area is -0.00854, while the strain corresponding to the same position of the normal cornea is -0.02277. This value is 2.67 times of that at the center of the lesion area. The stress in the center of the lesion area is 0.04337, and the stress corresponding to the same position of the normal cornea is 0.02729, which is 0.64 times of that in the center of the lesion area. When the ratio of Young's modulus of the normal corneal tissue to that of the diseased tissue is 4:1, it is the other way round. Considering the viscoelasticity of the corneal tissue, the tissue model was optimized. The results showed that the elastography of isolated tissues can be achieved by the micro-strain compression method, and the biomechanical responses of the diseased tissue and the normal tissue in ultrasound elastography are significantly different from each other. The results can provide theoretical guidance for the clinical application of elastography in ophthalmology.