Computational modeling of laser thrombolysis for stroke treatment

Many aspects of the physical processes involved in a pulsed laser interacting with an occlusion in the intra-cranial vascular system, e.g., a blood clot, are included in the simulation codes LATIS and LATIS3D. Laser light propagation and thermo-mechanical effects on the occlusion can be calculated by these codes. The hydrodynamic response uses a realistic equation of state which includes melting and evaporation. Simple material strength and failure models now included in these codes are required to describe clot breakup. The goal is to ascertain the feasibility of laser thrombolysis, and to help optimize the laser parameters for such therapy. In this paper detailed numerical results for laser interaction with water is considered as an initial model for laser thrombolysis of soft blood clots which have high water content. Three regimes of water response to increasing laser energy are considered: (1) the linear stress pulse, (2) the nonlinear evaporation bubble, and (3) the nonlinear inertial bubble. It is shown that later in time the inertial bubble evolves into a slowly growing cavitation bubble. More physical processes will be added in the near future to better model realistic occlusion-vessel wall geometries.