TABLE II.

Constants and parameters for diffuse light transport.

			Value/typical value
			in biological tissue
Quantity	Symbol	Units	for λ = 850 nm
Radiance	I(r, t, s)	W/(cm2·sr)	n/a
Planck’s constant	h	J·s	6.626 × 10−34
Speed of light in a vacuum	c	m/s	2.998 × 108
Index of refraction	n	Dimensionless	1.4
Speed of light in biological tissue	v = c/n	cm/ns	21.4
Absorption coefficient	μa	cm−1	0.2 (gray mattera)
Scattering coefficient	μs	cm−1	67 (gray mattera)
Anisotropy of scattering factor	g	Dimensionless	0.9
Reduced scattering coefficient	μs′ = (1 − g)μs	cm−1	6.7
Transport mean free path	L = 1/(μa + μs′)	cm	0.14
Fluence rate	Φ(r, t)	W/cm2	n/a
Photon diffusion coefficient	D = v/3(μa + μs′)	cm2/ns	1.03

^aReference 75.