Optimizing motion scaling and magnification in robotic surgery

BACKGROUND: Motion scaling is one possible advantage of robotic surgery. The aim of this study was to determine which scaling optimized precision and speed at different magnifications. METHODS: Three levels of motion scaling were tested at each of 3 camera magnifications. Surgically nave subjects (n = 12) were randomized as to the order of magnification level testing (3.5x, 6.5x, 9.5x) and motion scalings (10:1, 5:1, 1:1). The subjects were asked to pierce a needle through 6 printed microtargets; then accuracy and drill completion time were scored. RESULTS: At 3.5x magnification, no differences between groups were observed. At 6.5x magnification, the 5:1 scaling was superior to the 1:1 scaling in total errors, and the 10:1 scaling was significantly slower. At 9.5x magnification, 10:1 scaling resulted in fewer errors than 1:1 with no difference in time. Overall, the 10:1 and 5:1 scalings resulted in fewer errors. The 5:1 scaling resulted in less drill completion time than the 10:1 scaling. The 9.5x magnification resulted in the fewest errors. CONCLUSIONS: Motion scaling reduces the number of errors at higher magnifications, but can increase the task completion time. It is necessary to optimize both the motion scaling and magnification components of robotic systems to balance precision and speed.