Clinical evaluation of a respiratory gated guidance system for liver punctures

We have previously proposed a computer guidance system for liver punctures designed for intubated (free breathing) patients. The lack of accuracy reported (1 cm) was mostly due to the breathing motion that was not taken into account. In this paper we modify our system to synchronise the guidance information on the expiratory phases of the patient and present an evaluation on 6 patients of our respiratory gated system. Firstly, we show how a specific choice of patient allows us to rigorously and passively evaluate the system accuracy. Secondly, we demonstrate that our system can provide a guidance information with an error below 5 mm during expiratory phases.