Compensatory motion scaling for time-delayed robotic surgery.

BACKGROUND Round trip signal latency, or time delay, is an unavoidable constraint that currently stands as a major barrier to safe and efficient remote telesurgery. While there have been significant technological advancements aimed at reducing the time delay, studies evaluating methods of mitigating the negative effects of time delay are needed. Herein, we explored instrument motion scaling as a method to improve performance in time-delayed robotic surgery. METHODS This was a robotic surgery user study using the da Vinci Research Kit system. A ring transfer task was performed under normal circumstances (no added time delay), and with 250 ms, 500 ms, and 750 ms delay. Robotic instrument motion scaling was modulated across a range of values (- 0.15, - 0.1, 0, + 0.1, + 0.15), with negative values indicating less instrument displacement for a given amount of operator movement. The primary outcomes were task completion time and total errors. Three-dimensional instrument movement was compared against different motion scales using dynamic time warping to demonstrate the effects of scaling. RESULTS Performance declined with increasing time delay. Statistically significant increases in task time and number of errors were seen at 500 ms and 750 ms delay (p < 0.05). Total errors were positively correlated with task time on linear regression (R = 0.79, p < 0.001). Under 750 ms delay, negative instrument motion scaling improved error rates. Negative motion scaling trended toward improving task times toward those seen in non-delayed scenarios. Improvements in instrument path motion were seen with the implementation of negative motion scaling. CONCLUSIONS Under time-delayed conditions, negative robotic instrument motion scaling yielded fewer surgical errors with slight improvement in task time. Motion scaling is a promising method of improving the safety and efficiency of time-delayed robotic surgery and warrants further investigation.