Quantifying the effects of delays on telerobotic surgical operability via brain activity measurements.

Purpose: Telesurgery, increasingly valued for enabling remote procedures post-COVID, can be critically affected by communication delays-typically negligible in conventional robot-assisted surgery due to surgeon-patient co-location. While previous studies have assessed the impact of delays on surgical performance, their effects on the operator's cognitive state remain unclear. Therefore, this study assessed delay-induced changes in telesurgery operability based on intraparietal sulcus (IPS) activity.

Methods: A virtual-reality-based surgical assistance simulator was developed using the Unity game engine to replicate the da Vinci surgical robot and colorectal suturing environment. The simulator randomly introduced seven delay conditions to assess their impact on IPS activity during suturing. Eight right-handed participants, all of whom were non-medical students with no prior surgical experience, performed suturing while their IPS activity was measured using functional near-infrared spectroscopy. The left- and right-sided IPS activities were measured separately, and the task completion time and suturing error rate were also recorded for comparison.

Results: Significance was assessed using the nonparametric Jonckheere-Terpstra test. Left- and right-sided IPS activities decreased significantly for 150-300 and 0-300 ms delays, respectively. The task completion time increased significantly for 0-300 ms delays, while the suturing error rate increased significantly for 0-100 ms delays.

Conclusion: These findings confirm that IPS activity can be used to quantify delay-induced operability changes. For delays beyond 150 ms, significant IPS changes indicated that operators perceived degraded control. However, for delays of or shorter than 150 ms, the operators' precision unconsciously declined, indicating that greater caution is required in surgical tasks.