Abstract:

In neurovascular surgery, the surgeon tries to restore the vascular function, in particular theblood flow (ml/s). State-of-the-art methods rely on tissue contact or even wrap around thevessel which is increasing the risk of complications while intervention. Optical methodscould avoid the risks and provide the surgeon with the needed data. Quantitative fluorescenceangiography (QFA) has become an important research focus in the last years. Hereby,normally, a camera is integrated into the microscope which records the fluorescence dynamicof indocyanine green (ICG) in the near-infrared (NIR). Experimental pre-studies have showna mismatch of the flow value obtained by QFA and the reference. Therefore, a Monte Carlo(MC) simulation of the propagation of the photons in a vessel was developed to predictthis mismatch quantitatively. So far, this simulation assumes a homogeneous distributionof ICG. This thesis aims to check the validity of this assumption by computing the spatialand temporal ICG distribution via COMSOL Multiphysics. Further, the distribution canbe used as an input for the MC model to eliminate the assumption of a homogeneous ICGdistribution. For this task, 20 different simulations were conducted by variation of the radiusof the vessel model (VM) and the blood flow rate. The investigation of the homogeneousphase of the ICG distribution revealed that this phase is very short, ranging from 0.37 to 0.05seconds. These periods were so small, that the flow of the ICG molecules through the VMcan be modeled as heterogeneous.