Laser-induced liquid plasma formation and plasma-induced ablation of thrombus will occur in laser atherectomy. In order to avoid damage to blood vessels and increase the ablation rate, it is necessary to conduct simulations and experiments for the interaction process. A spatial and temporal distribution numerical model of laser-induced liquid plasma formation was constructed, and the ionization process in the range of 600μm before and after beam waist was calculated. The plasma profile showed a crescent shape shifted to the laser incident direction. It was found that compared with water, the higher extinction coefficient of blood restricted the plasma area to the focus and optical axis, and the stronger absorption capacity of plasma made the plasma shift toward the laser incident direction. The simulation results can fit the experimental results in water and blood diluent.
Excimer Laser Coronary Atherectomy (ELCA) uses 308nm laser to eliminate coronary atherosclerosis. It has a good therapeutic effect in diseases such as poor stent expansion, moderate calcification, and acute myocardial infarction. The laser catheter enters the patient's body during the operation and transmits the laser to the lesion, which plays an important role in the success of the operation. In this paper, the finite element simulation analysis of the mechanical properties of the laser catheter is carried out, and innovative optimization design is carried out on this basis. The paper first analyzes the laser catheter composite material, establishes its torsion, compression, and bending finite element model, and analyzes the influence of the microstructure on the mechanical properties of the laser catheter. Set different parameters for the helix angle, number and diameter of the optical fibers in the laser catheter, and simulate the stress conditions under three kinds of loads. The results show that the three variables have a great influence on the stress and deformation of the laser catheter composite material. Then a finite element model of the coronary artery of the heart is established, the laser catheter's movement in the coronary artery is simulated by LS-DYNA, and the effect of the laser catheter's diameter, wall thickness and elastic modulus on the stress of the laser catheter is analyzed. It is found that the laser catheter is subject to greater stress at the bending part of the aortic arch, and the diameter, wall thickness and elastic modulus of the laser catheter have a significant influence on the stress and advancing distance of the laser catheter. Finally, on the basis of simulation analysis and comprehensive consideration of various influencing factors, the parameters of the laser catheter are designed. In order to meet the stress requirements of different positions of the laser catheter, a catheter design with variable fiber helix angle is proposed.
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