Study Of The Physical Characteristics Of Biological Tissues Based On Photoacoustic Effect

The change of biological tissue pathological condition often leads to changes in physical properties of biological tissue.The physical parameters of biological tissue characterization gives an effectively index to pathological state of biological tissue.Through the research on the physical characteristics of the tissue,it can provide the critical information for the diagnosis and prevention of related diseases.Photoacoustic signal of biological tissue is generated by laser irradiation on tissue.According to photoacoustic effect and the principle of vibration and wave,there may be have relationship between the photoacoustic signal and the physical characteristics of the tissue.We can obtain related parameters of biological tissue pathological condition from the photoacoustic signal.In order to explore the relationship between the photoacoustic signal and the physical characteristics of biological tissue,in this paper,the following work mainly be researched.Firstly,the relationship between the elastic characteristics of biological tissue and the frequency of optical signal and the relationship between the damping characteristics of the biological tissue and the time domain characteristics of photoacoustic signal are derived in theory.According to the formula,the theoretical value of photoacoustic signal is obtained by using MATLAB simulation.Secondly,from the scanning imaging of printing black grid with 200?m width and rat ear obtaining by the Acoustic-resolution photoacoustic microscopy,the black grid width of the scanning imaging has the consistence with the actual width,and the vessel of scanning position could be clearly distinguished from the surrounding tissue.Thirdly,the experimental samples of different concentration(6%,8%,10%,12%,and 14%)were used to study the frequency of photoacoustic signal generated by different vibration sources.The results show that the frequency of the photoacoustic signal is increased with the increase of sample elastic modulus,and the elastic modulus of the sample is also linearly dependent to the square of the frequency of photoacoustic signal,and the linear correlation is consistent with the theoretical calculation results;Finally,the damping effect caused by different hardness is studied on same vibration sources.The experimental results show that the greater the hardness of the peripheral tissue is,the faster the oscillation attenuation rate of the oscillating source is,the greater the peak attenuation coefficient of the photoacoustic signal is,the less the time is used.In a word,in this paper elastic characteristics has been studied on theoretical and experimental aspects through the time domain and frequency domain characteristics of photoacoustic signal and quantified by specific patameters based on Acoustic-resolution photoacoustic microscopy.It lays the theoretical foundation for the future of the photoacoustic elastography.Based on the theory and experiment,the paper studied the relationship between the elastic properties of the tissue phantom and the photoacoustic signal,and the elastic measurement of animal tissue and blood vessel and Photoacoustic elasticity imaging will be the next step.