Steady hands and uninterrupted, sharp vision are extremely critical when performing surgery on delicate structures like the brain or hair-thin blood vessels. While surgical cameras have tremendously improved what surgeons see during operative procedures, the steady hand remains to be enhanced. New surgical technologies, including surgeon-guided robotic hands, cannot prevent accidental injuries when operating close to fragile tissue.
Researchers have shown that by delivering small, yet perceptible buzzes of electrical currents to fingertips, users can be given an accurate perception of distance-to-contact. This insight enabled users to control their robotic fingers precisely enough to gently land on fragile surfaces. The technique could be an effective way to help surgeons reduce inadvertent injuries during robot-assisted operative procedures. Surgeons will be able to get an intuitive sense of how far their robotic fingers are from contact — information they can then use to touch fragile structures with just the right amount of force.
Robot-assisted surgical systems, also known as telerobotic surgical systems, are physical extensions of a surgeon. By controlling robotic fingers with movements of their own fingers, surgeons can perform intricate procedures remotely, thus expanding the number of patients to which they can provide medical attention. Also, the tiny size of the robotic fingers means that surgeries are possible with much smaller incisions since surgeons need not make large cuts to accommodate their hands into the patient’s body for operations.
To move their robotic fingers precisely, surgeons rely on live streaming of visual information from cameras fitted on tele-robotic arms. Thus, they look into monitors to match their finger movements with those of the telerobotic fingers. In this way, they know where their robotic fingers are in space and how close these fingers are to each other; however, just visual information is not enough to guide fine finger movements, which is very critical when the fingers are in the close vicinity of the brain or other delicate tissue.
To address this problem, the team came up with an alternate way to deliver distance information that is independent of visual feedback. By passing different frequencies of electrical currents onto fingertips via gloves fitted with stimulation probes, the researchers were able to train users to associate the frequency of current pulses with distance; that is, increasing current frequencies indicated the closing distance from a test object. They then compared if users receiving current stimulation along with visual information about closing distance on their monitors did better at estimating proximity than those who received visual information alone.
The team tailored their technology according to the user’s sensitivity to electrical current frequencies; if a user was sensitive to a wider range of current frequencies, the distance information was delivered with smaller steps of increasing currents to maximize the accuracy of proximity estimation. The researchers found that users receiving electrical pulses were more aware of the proximity to underlying surfaces and could hence lower their force of contact by around 70%, performing much better than the other group. Overall, they observed that proximity information delivered through mild electric pulses was about three times more effective than the visual information alone.
The approach has the potential to significantly increase maneuverability during surgery while minimizing risks of unintended tissue damage. The technique would add little to the existing mental load of surgeons during operative procedures.