  Surgical resection of hepatic tumours is not always possible, since it
depends on different factors, among which their location inside the liver
functional segments. Alternative techniques consist in local use of chemical or
physical agents to destroy the tumour. Radio frequency and cryosurgical
ablations are examples of such alternative techniques that may be performed
percutaneously. This requires a precise localisation of the tumour placement
during ablation. Computer-assisted surgery tools may be used in conjunction
with these new ablation techniques to improve the therapeutic efficiency,
whilst they benefit from minimal invasiveness. This paper introduces the
principles of a system for computer-assisted hepatic tumour ablation and
describes preliminary experiments focusing on data registration evaluation. To
keep close to conventional protocols, we consider registration of pre-operative
CT or MRI data to intra-operative echographic data.
