点状散乱体レンズの配列最適化における初期状態依存性

抄録

In order to promote the effect of a thrombolytic agent as a non-invasive cure for the cerebral infarction of an acute stage, a real-time adaptive ultrasonic lens constructed by arranging point-like scatterers on a lattice has been proposed. The structure was optimized from the initial arrangement of the scatterers determined by binarizing the interference pattern of the radiative wave from a point sauce at the focal point and the reference plane wave with the analogy of holography. The dependence of convergence of optimization on the initial state and on the thickness of lattice has, however, never been investigated, yet. In the present paper, four kinds of the initial states are considered, that is, the holographically generated configuration, the configuration without the scatterers on all of lattice points, the configuration with the scatterers on all of lattice points and the configuration with the randomly distributed scatterers. The convergence of optimization for three kinds of thickness, that is, the number of layers is also systematically investigated. It has been found that the initial configuration without the scatterers shows the fastest convergence and increase of the number of layers improves the ratio of the power of the ultrasound wave at a focal point to that of the background.