SE-ADM signal data from the AD converter were transferred to a personal computer (Intel Core i7, 2.8 GHz, Windows 7), and high-resolution SE-ADM images were processed from the dielectric signal and the scanning signal using the image-processing toolbox of MATLAB R2016b (MathWorks Inc., MA, USA). Original SE-ADM images were filtered using a two-dimensional Gaussian filter (GF) with a kernel size of 7 × 7 pixels and a radius of 1.2σ. Background subtraction was achieved by subtracting SE-ADM images from the filtered images using a broad GF (400 × 400 pixels, 200σ).