IEEE Trans Biomed Eng. 2021 Sep;68(9):2637-2644. doi: 10.1109/TBME.2020.3044066. Epub 2021 Aug 19.
Estimating the elasticity distribution in the cornea is important because corneal elasticity is usually influenced by corneal pathologies and surgical treatments, especially for early corneal sclerosis. Because the thickness of the cornea is typically less than 1 mm, high-resolution ultrasound elastography as well as the Lamb wave model is required for viscoelastic property estimation. In the present study, an array high-frequency ultrasound (HFUS) elastography method based on ultrafast ultrasound imaging was proposed for estimating the viscoelastic properties of porcine cornea.
The elastic wave was generated by an external vibrator, after which the wave propagation image was obtained using a 40-MHz array transducer. Viscoelasticity estimation was performed by fitting the phase velocity curve using the Lamb wave model. The performance of the proposed HFUS elastography system was verified using 2-mm-thick thin-layer gelatin phantoms with gelatin concentrations of 7% and 12%. Ex vivo experiments were carried out using fresh porcine cornea with artificial sclerosing.
Experimental results showed that the estimated elasticity was close to the standard value obtained in the phantom study when the Lamb wave model was used for elasticity measurement. However, the error between the standard elasticity values and the elasticity values estimated using group shear wave velocity was large. In the ex vivo eyeball experiments, the estimated elasticities and viscosities were respectively 9.1 ± 1.3 kPa and 0.5 ± 0.10 Pa·s for a healthy cornea and respectively 15.9 ± 2.1 kPa and 1.1 ± 0.12 Pa·s for a cornea with artificial sclerosis. A 3D HFUS elastography was also obtained for distinguishing the region of sclerosis in the cornea.
The experimental results demonstrated that the proposed HFUS elastography method has high potential for the clinical diagnosis of corneal diseases compared with other HFUS single-element transducer elastography systems.
评估角膜的弹性分布很重要，因为角膜弹性通常受到角膜病变和手术治疗的影响，尤其是在早期角膜硬化时。由于角膜的厚度通常小于 1 毫米，因此需要高分辨率的超声弹性成像和兰姆波模型来估计粘弹性特性。本研究提出了一种基于超快超声成像的阵列高频超声（HFUS）弹性成像方法，用于估计猪眼角膜的粘弹性。
弹性波由外部振动器产生，然后使用 40MHz 阵列换能器获得波传播图像。通过使用兰姆波模型拟合相速度曲线来进行粘弹性估计。使用 7%和 12%浓度的 2mm 厚的薄层明胶体模验证了所提出的 HFUS 弹性成像系统的性能。使用人工硬化的新鲜猪眼角膜进行了离体实验。
实验结果表明，当使用兰姆波模型进行弹性测量时，所估计的弹性值与体模研究中的标准值接近。但是，标准弹性值与群剪切波速度估计的弹性值之间的误差较大。在离体眼球实验中，健康角膜的估计弹性和粘度分别为 9.1±1.3kPa 和 0.5±0.10Pa·s，人工硬化角膜的估计弹性和粘度分别为 15.9±2.1kPa 和 1.1±0.12Pa·s。还获得了 3D HFUS 弹性成像，以区分角膜硬化区域。
与其他 HFUS 单元素换能器弹性成像系统相比，实验结果表明，所提出的 HFUS 弹性成像方法在角膜疾病的临床诊断中具有很高的潜力。
