Verification of delay time and image compression thresholds for telesurgery

Telerobotic surgery relies on communication lines, causing delays, and video information requires pre-transmission compression. Such delays and video degradation will continue to be unavoidable making communication conditions verification essential. Understanding the network specification values required for telerobotic surgery entails determining acceptable levels of delay and degradation due to the video compression and restoration processes during surgery.

The hinotori™ surgical robot from Medicaroid was used. Eight surgeons, skilled in robotic surgery, performed gastrectomy or rectal resection on pigs. Image compression (bitrate: 120, 60, 30, 20, 10 Mbps) was random, changing encoder settings during surgery, and delay times (30, 50, 100, 150 milliseconds) were pseudo-randomly inserted, changing emulator settings. Acceptable video levels were evaluated. Subjective evaluations by surgeons and evaluators regarding image degradation and operability, and objective evaluations of image degradation and operability were given five-point ratings.

Regarding delay time, 30 and 50 millisecond periods garnered average ratings of 3.6 and 4.0, respectively, signifying that surgery was feasible. However, at 100 and 150 millisecond, average ratings were 2.9 and 2.3, respectively, indicating surgery was not feasible for the most part in these cases. The average rating for image compression was 4.0 or higher for bitrates of 20, 30, 60, and 120 Mbps, suggesting that surgery is possible even at bitrates as low as 10 Mbps, with an average rating of 4.0.

In remote robotic surgery using the hinotori™, image compression and delay time are largely acceptable, so surgery can be safely performed.