Hybrid Monte Carlo simulation with ray tracing for fluorescence measurements in turbid media.

We present a hybrid Monte Carlo simulation method with geometrical ray tracing (hMC-GRT) to model fluorescence excitation and detection in turbid media by optical imaging or spectroscopy systems employing a variety of optical components. hMC-GRT computational verification was achieved via reflectance and fluorescence simulations on epithelial tissue models in comparison with a standard Monte Carlo code. The mean difference between the two simulations was less than 5%. hMC-GRT experimental verification employed depth-sensitive steady-state fluorescence measurements using an aspherical lens on two-layered tissue phantoms. hMC-GRT predictions agreed well with experimental results, achieving less than 3.5% error for measurements at the phantom surface. Verification results demonstrate that the hMC-GRT simulation has the potential to become a useful computational toolbox for designing tissue fluorescence imaging and spectroscopy systems. In addition, the hMC-GRT approach enables a wide variety of applications for computational modeling of fluorescence in turbid media. The source codes are available at https://github.com/ubioptronics/hMC-GRT.