Estimation of optical pathlength through tissue from direct time of flight measurement

TLDR

Quantitation of near‑infrared spectroscopic data in scattering tissues requires knowledge of the optical pathlength. The study demonstrates that the optical pathlength can be directly estimated from the time of flight of picosecond light pulses. Monte Carlo simulations and phantom experiments show that the mean time‑dispersed pulse correlates with the pathlength used in spectroscopic calculations, and time‑of‑flight measurements across a rat head yield a pathlength of 5.3 ± 0.3 times the head diameter.

Abstract

Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3+or-0.3 times the head diameter.