Evaluating control modes for constrained robotic surgery

Minimally invasive surgery (MIS) constrains instrument motions to 4 DOF by precluding lateral motion at the incision. Robotic MIS systems can interpose arbitrary mappings between the surgeon's motions at the master controller and the motions of instrument tips within the patient's body. Our goal was to find the interface that was easiest to learn. We investigated the effects of different coordinate frame mappings (screen-mapped versus instrument-mapped) and master dexterities (6 DOF versus 4 DOF) by means of performance measures on simple surgical tasks. All four mode-dexterity combinations had approximately the same time-to-completion. The combination of instrument-based mapping and 4 DOF master had lower error rate and lower subjective workload. This mode most clearly reproduces the task constraints within the patient's body.