基于微激励光学相干弹性成像的角膜固频在体测量

Micro-Force Optical Coherence Elastography for in vivo Corneal Natural Frequency Measurement

非侵入式角膜在体弹性测量具有重要临床意义却尚无金标准。提出了基于光学相干层析(OCT)的光学相干弹性成像方法(OCE),实现了微气体(压强为10~40 Pa)脉冲激励下软组织的亚纳米-微米级振幅力学响应的高分辨观测。结合时域恢复曲线拟合模型(R-Model)和频域单自由度振动模型(SDOF-Model),测量了浓度(质量分数)为1.0%~2.0%的琼脂仿体和两名志愿者角膜的固有频率。测量结果表明:固有频率值不受激励压强大小的影响,且与杨氏模量的平方根正相关(皮尔逊相关系数为r≥0.98);SDOF-Model具有更好的可重复性,其平均离散系数(CV)为0.9%(琼脂仿体)和1.7%(人眼角膜),而R-Model的平均CV则高达8.4%(琼脂仿体)和42.6%(人眼角膜),即基于SDOF-Model的微激励OCE方法更适合人眼角膜固有频率的在体测量。

In vivo and non-invasive human corneal elasticity measurement is clinically essential,but there is no gold-standard yet.An optical coherence elastography(OCE)method is provided for tissue natural frequency characterization.A microliter(10--40 Pa)air-pulse stimulator is used to induce tissue displacements with the magnitudes ranging from sub-nanometer to micrometer,and a high-resolution optical coherence tomography(OCT)system is used to quantify the resulting tissue dynamics.Both of a temporal relaxation model(R-Model)and a single degree of freedom Voigt model(SDOF-Model)are applied for natural frequency measurements on agar phantoms with concentration(mass fraction)of 1.0%--2.0%as well as on in vivo corneas of two human subjects.The measurement results show that the natural frequency remains the same as the stimulation force is increased from 10 Pa to 40 Pa,and is positively correlated to the square root of Young’s modulus(Pearson’s correlation coefficient is r≥0.98).The SDOF-model is more precise and repeatable.The average coefficients of vitiation(CVs)are only 0.9%for agar phantoms and 1.7%for human corneas using the SDOF-Model,while the average CVs are 8.4%for agar phantoms and 42.6%for human corneas using the R-Model.Compared to the R-Model,the combination of the SDOF-Model with micro-force OCE system is more suitable for in vivo human corneal biomechanics characterization.