Table 1.
Nomenclature and abbreviation | Definition |
---|---|
DC component | 0th order of the transformed series in FFT. It represents the summation of signals from all input pixels. |
FFT | Fast Fourier transformation |
(Global) T-tubules | The entire tubule system, including both TE and LE. |
Global T-tubule regularity | The magnitude of the major frequency normalized to that of the DC component, calculated from skeletalized global T-tubule system of a cell. TTpower, previously defined as an index for T-tubule regularity in Wei et al. (15), is a measure of the magnitude of the major frequency without normalization. |
PIT | Pixel intensity threshold, a value used for thresholding the input image based on the intensity of pixels, to detect ROI. |
ROI | Region of interest, the intracellular region enclosed by the peripheral membrane. |
TE density | The total number of pixels of skeletalized TE divided by the total Number of pixels of intracellular area (ROI). |
LE density | The total number of pixels of skeletalized LE divided by the total number of pixels of intracellular area (ROI). |
TE spacing | The average horizontal spatial interval between TE, derived from the spatial frequency. |
TTint | Index of T-tubule integrity, which takes into account both regularity and density. For analysis of global T-tubules, TTint = global T-tubule density × global T-tubule regularity; for analysis of TE only, TTint = TE density × TE regularity. |