The polar regions of the solar corona exhibit during solar minima very faint ray-like structures which apparently outline the lines of polar magnetic field. Usually they are named plumes in the solar coronal literature. In order to understand the spatio-temporal characteristics of these plumes we analyze a sequence of 400 continuous observations covering a period of 3 days. For such analysis we are using Hough transform methods and a multiresolution context. The main result of this work is the fractal structure of the electron density distribution in the coronal hole as well as the fractal characteristics of its temporal evolution. The simulation of sequences of coronal images projected from 3D distributions allows a refinement of the physical parameters.