In neurovascular surgery the surgeon tries to restore the vascular function, in particular the blood flow (ml/s). State of the Art methods rely on tissue contact or even wrap around the vessel which is increasing the risk of complications while intervention. Optical methods could encounter this risk and provide the surgeon with curial information. Quantitative fluorescence angiography is a research focus in the institute. Hereby a camera is integrated into the microscope and records the fluorescence dynamic of Indocyanine Green (ICG) in the NIR. Experimental pre-studies have shown a mismatch of the flow value obtained by quantitative fluorescence angiography and the reference. Therefore, a Monte Carlo Multi Layer (MCML) of a vessel was developed and the mismatch could be simulated qualitatively. In this Master Thesis two aspects of the MCML are in focus for further development. First, adding fluorescence as a scattering like event and second to convert the flat multi layer structure to a radial one. At the end both models should be compared quantitatively.