1. An image registration method for use in medical imaging, the method including the steps of: providing a sequence of images each one including a digital representation of a body-part under analysis, selecting a reference image within the sequence, the remaining images of the sequence defining moving images, and re-aligning at least one portion of a moving image with respect to the reference image, wherein the step of re-aligning includes: a) defining a delimitation mask identifying a region on the reference image with which the at least one portion of the moving image has to be re-aligned, and a feature mask identifying a further region on the reference image within which the re-alignment is calculated, b) determining an optimized transformation for compensating a displacement of the moving image with respect to the reference image by optimizing a similarity measure between: b1) a first computation region identified on the reference image by a computation mask and a second computation region identified by the computation mask on the moving image transformed according to a proposed transformation, the computation mask being determined by the intersection between the delimitation mask transformed according to the proposed transformation and the feature mask, or b2) a first computation region identified by a computation mask on the reference image transformed according to a proposed transformation and a second computation region identified by the computation mask on the moving image, the computation mask being determined by the intersection between the feature mask transformed according to the proposed transformation and the delimitation mask, or b3) a first computation region identified on the reference image by a computation mask transformed according to the reverse of a proposed transformation and a second computation region identified by the computation mask on the moving image, the computation mask being determined by the intersection between the feature mask transformed according to the proposed transformation and the delimitation mask, and c) transforming the at least one portion of the moving image according to the optimized transformation.