The Lung Cancer Cells Refractive Index Of Theoretical Calculation And Simulation Based On Optical Tweezers System

Lung cancer is a kind of malignant tumor with high mortality rate, now CT imagingis the main method which is based on early discovery, early diagnosis and early treatmentin order to improve the survival rate. But the clinical imaging qualitative diagnosis had ahigh rate of false positive and misdiagnosis. Imaging diagnosis used biological tissuechanges in the optical properties to reflect the changes of its physiological state. At thecellular scale,”refractive index” is the optical paramenter to reveal such changes. Theexact understanding of lung cancer cells refractive index is more important to improveCT qualitative diagnosis accuracy. To this end, in this paper proposes a method based onoptical tweezers to calculate the refractive index of lung cancer cells and the theoreticalcalculations and error analysis for it.First, search on the stable capture conditions o f cells in the optical trap, to analysisthe optical gradient force in theoretical, and choose the optical trapping force calculationmodel according to the characteristics of lung cancer cells, simulate and analysis theaxial force, according to the simulation results discuss the influence of optical tweezerssystem parameters to the axial force. The results showed that: a prerequisite for lungcancer cells captured were the relative refractive index of cells and the surroundingmedium greater than1; small laser waist or large laser power will form a stable axialcapture, but a very small waist is difficult to achieve because of the constraints ofdiffraction, when the power is too large, it is easy to change cell damage and biologicalcharacteristics; uptake of cells to different wavelength of light have great influence tocapture stability on the axial. The above conclusions will provide s theoretical basis ofselecting appropriate parameters of the optical tweezers system to make the lung cancercells are stabilized captured in the optical trap.Based on geometrical ray theory, use the variable step size simpson method tocalculate and simulate the lung cancer cells axial optical trapping force, use the stableequilibrium point to calculate the relationship between optical trap stiffness and therefractive index in theoretical and make curve fitting. The fitting result showed that: thevariation of the optical trap stiffness and lung cancer cells refractive index fitting betterwith the cubic polynomial curve. In the optical trap treat lung cancer cells as the particles doing Brownian motion,use the method of Monte-Carlo to thermal driving force analysis method to simulatedisplacement versus time relations sequence of lung cancer cells in optical trap. Calibrateoptical trap stiffness and then to calculate the refractive index of lung cancer cells,analysis the error. The result showed that: the error of three calibration methods tocalculate the refractive index of lung cancer cells within+2.5%, it is indicate thatsimulation data is feasible. And the mean square displacement method has the strongestanti-jamming capability, that is the more appropriate method through calibrate opticaltrap stiffness to solve the refractive index of lung cancer cells.