Fig. 4.

(a) US and (b) axial CT images of markers implanted in the liver. (c) Liver marker positions recorded from CT images (See Video 1, MPEG, 1.25 MB [URL: http://dx.doi.org/10.1117/1.JMI.1.2.025001.1] for a 3-D rotational view). (d) Reproducibility of marker positions after repeated robotic placement with the real probe, model probe after returning to the same position or force, and when no probe was in place, from left to right, respectively.