Contrast-to-Noise Ratio on filaments

Filaments are grouped in sets of four differing by relative direction against the anode-cathode one. For every group the number of visible filaments is shown as well as the min, max and average CNR.

For each filament of a group, CNR is calculated using the following formula.

$CNR = \frac{|\mu_D-\mu_B|}{\sigma_B}$

where:

• $\mu_D$: mean pixel value of the detail ROI
• $\mu_B$: mean pixel value of the background ROI
• $\sigma_B$: standard deviation of pixel values of the background ROI