Table 1. Mathematical formulations, descriptions, and physiological correlate of spatial frequency parameters.

Adapted from Pearson et al. (2017).

Parameter	Mathematical Formulation	Mathematical Description	Tissue Indicator(s)
Peak spatial frequency radius (PSFR)	$\sqrt{u_{max}^2+v_{max}^2}$, where umax, vmax are directional vectors in frequency domain	Distance from origin to peak of maximum frequency amplitude in 2-D Fourier spectrum	Dominant frequency of banded fascicular organization pattern
Mmax	max(F(u,v))	Value of the maximum frequency amplitude in 2-D Fourier spectrum	Strength of frequency of most prominent banded pattern of tissue
Mmax Percent	$\raisebox{1ex}{$max\left(F\right(u,v\left)\right)$}\!\left/ \!\raisebox{-1ex}{$\iint F\left(u,v\right)dudv$}\right.$	Ratio of Mmax to total intensity of pixels in 2-D Fourier spectrum	Contribution of most prominent fascicle pattern compared to total background
Sum	∬F(u,v)dudv	Sum of frequency amplitudes in 2-D Fourier spectrum	Equivalent to total image brightness