Abstract

Photobiomodulation (PBM) is a promising approach to treat Parkinson’s disease (PD) symptoms in cellular or animal models. Unfortunately, little information is available on the optical parameters playing a role in the light dosimetry during PBM. We conducted a study to determine the effective attenuation coefficient µ_eff of PD-relevant human deep brain tissues at 671 and 808 nm, using a multichannel fluence rate-meter comprising sub-millimeter isotropic detectors. The first step involved measurements of tissue modifications induced by postmortem situation and tissue storage on rabbit brains. The parameter µ_eff was measured using various tissue conditions (in vivo, immediately after sacrifice, after six weeks’ storage at −20°C or in 10 % formaldehyde solution) on eight female New Zealand white rabbits. In the second step, fluence rate was measured at various locations of a frozen human deep brain when the deep brain was illuminated from the sphenoidal sinus. The results were processed by an iterative Monte-Carlo algorithm to generate sets of optical parameters, and results collected on rabbit brains were used to extrapolate the µ_eff value that would be observed in human deep brain tissues in vivo. Under all tissue conditions, the value of µ_eff at 808 nm was smaller than that at 671 nm. After long-term storage for six weeks at −20°C, µ_eff decreased, on average by 15 to 25 % at all wavelengths, while it increased by 5 to 15 % at all wavelengths after storage in formaldehyde. Therefore, a reasonable estimate of in vivo human deep brain µ_eff values at 671 and 808 nm can be obtained by multiplying the data we report by 120 %.

© 2015 SPIE