  This paper introduces the principles of computer assisted percutaneous renal
puncture, that would provide the surgeon with an accurate pre-operative 3D
planning on CT images and, after a rigid registration with space-localized
echographic data, would help him to perform the puncture through an intuitive
2D/3D interface. The whole development stage relied on both CT and US images of
a healthy subject. We carried out millimetric registrations on real data, then
guidance experiments on a kidney phantom showed encouraging results.
