Figure 1

The result of applying 3D median filtering using a kernel size of 5 × 5 × 5 pixels. (A) Shows the original data, of size 234 × 256 pixels, where each pixel is 27 nm. (B) Shows the median filtered data. The filtering eliminates the fine structure in the image, which can be considered noise for the purpose of contour extraction. However the major contours are well preserved