Light penetration in human and rabbit brains: measurements using an isotropic detector

Light attenuation in a sample of human brain has been measured using a small (0.5 mm in diameter) fiber isotropic detector and similar to that an isotropic irradiator. Two lasers, He-Ne (633 nm) and GaAs (890 nm), were used. In vivo measurements were performed with rabbit brain. Penetration depth of 633 nm light was 1.3 mm and 2.4 mm respectively for human and rabbit brain. Propagation of 890 nm light was significantly higher, penetration depth was 2.8 mm for human tissue and 5.3 for rabbit.