Red and NIR light dosimetry in the XXXX deep brain.

@entity1 @entity75 @entity191
UNASSIGNED: Photobiomodulation (PBM) appears promising to treat the hallmarks of @entity191 ( @entity191 ) in cellular or animal models. We measured light propagation in different areas of @entity191 -relevant deep brain tissue during transcranial, transsphenoidal illumination (at 671 and 808  nm) of a cadaver head and modeled optical parameters of @entity1 brain tissue using Monte-Carlo simulations. Gray matter, white matter, cerebrospinal fluid, ventricles, thalamus, pons, cerebellum and skull bone were processed into a mesh of the skull (158  *  201  *  211 voxels; voxel side length: 1  mm). Optical parameters were optimized from simulated and measured fluence rate distributions. The estimated  eff for the different tissues was in all cases larger at 671 than at 808  nm, making latter a better choice for light delivery in the deep brain. Absolute values were comparable to those found in the literature or slightly smaller. The effective attenuation in the ventricles was considerably larger than literature values. Optimization yields a new set of optical parameters better reproducing the experimental data. A combination of PBM via the sphenoid sinus and oral cavity could be beneficial. A 20-fold higher efficiency of light delivery to the deep brain was achieved with ventricular instead of transcranial illumination. Our study demonstrates that it is possible to illuminate deep brain tissues transcranially, transsphenoidally and via different application routes. This opens therapeutic options for sufferers of @entity191 or other @entity75 necessitating light therapy.
