Elasticity Measurement Method Of Heterogeneous Biomaterials Based On Rayleigh Wave Optical Coherence Tomography

Elasticity of biological tissue provides important information for pathological studies and diagnosis and treatment of diseases.Most biological tissue is heterogeneous consisting of complex components.It is very difficult to quantitatively measure the elastic modulus of each component at the same time using the existing testing techniques with non-destructive and high accuracy.Optical Coherence Tomography(OCT)can image the tissue with high resolution,fast speed and about 2 mm penetration.The penetration depth of Rayleigh wave in tissues is about one wavelength,so it has dispersion characteristics when it propagates in layered media.Based on the different imaging modes of OCT and the propagation characteristics of Rayleigh wave in heterogeneous tissues,we develop an experimental method of Optical Coherence Elastography(OCE)for measuring the elasticity of layered tissue at the same time.The main work is as follows:Firstly,according to the absorption and scattering characteristics of laser in biological tissue,homogeneous and layered phantoms were made to simulate biological tissue.Secondly,an OCE experimental technique is developed based on the dispersion property of Rayleigh wave in layered media and the multi-dimensional data acquisition mode of OCT system for quantitative measurement of the Young's modulus of vertical heterogeneous tissue.The attenuation characteristic of Rayleigh wave is tested by measuring the OCT phase changes with depth in a stratified phantom at different frequencies.The reconstruction technology of three-dimensional data is proposed to measure the lateral heterogeneous tissues.Velocity-position-time maps in different depth can be obtained,which shows the velocity of Rayleigh wave propagating from one material to another.Young's modulus of each material can then be measured quantitatively.The accuracy of Rayleigh wave OCE testing technology is verified by tensile test.The difference between the two experimental result was less than 5%.Finally,the elastic properties of pork tissues in different parts were measured by using the Rayleigh wave OCE technique.The results showed that Young's modulus of skin,adipose,muscle and connective tissue were 208.02 kPa,361.14 kPa,284.07 kPa and 46.92 kPa,respectively.The Rayleigh wave OCE developed in this thesis is easy to use and has high sensitivity.It provides a new experimental method for biomechanical testing.It can accurately measure Young's modulus of various components in layered biological tissue.Because the amplitude of the Rayleigh wave excitation is only 2 ?m,which will not cause damage to most tissue under test.Thus,it has the potential to be applied to in vivo elasticity testing of biological tissue such as skin.