Measurement of the optical properties of the skull in the wavelength range 650-950 nm

Abstract

The optical properties of samples of bone from pig skull have been measured over the wavelength range 650-950 nm. The scattering phase function was measured on thin samples of the bone using a goniometer, and a value for the mean cosine g, of the scattering angle, was calculated. The scattering and absorption coefficients, mu s and mu a were then determined from measurements of diffuse reflectance and transmittance made with a pair of integrating spheres, by a step-wise search through a table of diffuse reflectance and transmittance versus mu a and mu s generated by a Monte Carlo model incorporating the measured scattering phase function. Values for g measured on six samples varied from 0.925 +/- 0.014 at 650 nm to 0.945 +/- 0.013 at 950 nm. Corresponding values for mu a and mu s measured on 18 samples were mu a = 0.04 +/- 0.002 mm-1, mu s = 35 +/- 0.7 mm-1 at 650 nm to mu a = 0.05 +/- 0.002 mm-1, mu s = 24 +/- 0.6 mm-1 at 950 nm.

Light transmittance of the periodontium

“…The attenuation coefficients calculated in this study were lower than the equivalent attenuation coefficients of skulls [44,45] and skin [46,47] reported in previous studies. The discrepancies may be attributed to the difference in experimental design including selection of light source and detector, experimental setup, and the materials and sample preparation.…”

In-vivo multilaboratory investigation of the optical properties of the human head

“…In literature there are studies reporting on ex-vivo or post-mortem measurements for the characterization of the human head optical properties, [15][16][17][18][19][20] but they are not representative of an in-vivo condition.…”

Transcranial Light Emitting Diode Therapy (TCLT) and its Effects on Neurological Disorders

“…Jagdeo et al [40] showed that this radiation range can penetrate soft tissues, bone, and brain parenchyma in a study using cadavers preserved in formalin. According Firbank et al [41], the absorption coefficient of radiation in the 650 nm and 950 nm range is between 0.02 and 0.05 mm -1 in the skull, while the scattering coefficient has a linear decrease from 35 mm -1 at 650 nm wavelength to 25 mm -1 at 950 nm wavelength. Similarly, the absorption and scattering coefficients of brain white and gray matter for the same region of the spectrum do not differ greatly [42].…”