Fig. 4

Graphical illustration of the different steps representing the two key-features of non-rigid registration algorithm based on points. On the right, a zoom on a squared region of interest is presented to visualise the described procedure. a The feature points (or coordinates) are extracted on the reference and moving images. b An artificial grid is added on both images and, finally, c the features points are summed to the nodes of the artificial grid in both, reference and moving images