New Method Prevents Accidental Injuries in Robot-Assisted Procedures

Sharp, uninterrupted vision and steady hands are very important when conducting surgeries on fragile structures like hair-thin blood vessels and the brain.

Although surgical cameras have enhanced the processes that surgeons view at the time of operative procedures, the “steady hand” is yet to be improved—for example, the latest surgical technologies, such as advanced surgeon-guided robotic hands, cannot avoid unintentional injuries that are caused in the delicate tissues close to them during operation.

In a recent study reported in the January issue of the Scientific Report journal, scientists at Texas A&M University have demonstrated that users can be given a precise perception of the distance to contact by sending small but noticeable pulses of electrical currents to their fingertips. This understanding allowed the users to precisely handle their robotic fingers so that they land softly on delicate surfaces.

According to the scientists, this method may provide an effective way for surgeons to minimize accidental injuries that are caused at the time of robot-assisted operative procedures.

One of the challenges with robotic fingers is ensuring that they can be controlled precisely enough to softly land on biological tissue. With our design, 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.

Hangue Park, Assistant Professor, Department of Electrical and Computer Engineering, Texas A&M College of Engineering

Also called telerobotic surgical systems, the robot-assisted surgical systems are a surgeon’s physical extensions. Surgeons can perform complicated procedures remotely by regulating the robotic fingers through the movements of their own fingers. This would allow the surgeons to widen the number of patients who require their medical attention.

The small size of the robotic fingers also implies that surgeries can be performed with relatively smaller cuts since surgeons no longer have to make large incisions to fit their hands in the patient’s body at the time of the operations.

To accurately move their robotic fingers, surgeons often depend on live streaming of visual data from cameras fixed onto the telerobotic arms. Therefore, the surgeons look into the monitors to match the movements of their fingers with those of the telerobotic fingers. In this manner, they know the exact location of the robotic fingers in space and the proximity of these fingers to one another.

But Park also observed that mere visual data is not sufficient to direct the fine movements of the robotic fingers and this is particularly crucial when the fingers are very close to fragile tissues, including the brain.

Surgeons can only know how far apart their actual fingers are from each other indirectly, that is, by looking at where their robotic fingers are relative to each other on a monitor. This roundabout view diminishes their sense of how far apart their actual fingers are from each other, which then affects how they control their robotic fingers.

Hangue Park, Assistant Professor, Department of Electrical and Computer Engineering, Texas A&M College of Engineering

To overcome this issue, Park and his research group developed an alternative method to send remote data that is not dependent on visual feedback. When the researchers passed varying frequencies of electrical currents onto the fingertips through gloves equipped with stimulation probes, they were able to train the users to relate the frequency of the electrical currents with distance, which means increasing frequencies of the electrical current denoted the closing distance from a test object.

The researchers subsequently compared if users, who are receiving both current stimulation and visual data about the closing distance on their monitors, did better at predicting the proximity than those who received only the visual data.

Together with his research team, Park also customized the new technology as per the user’s sensitivity to the frequencies of the electrical current. This means, if a user was susceptible to a broader range of electrical current frequencies, the distance data would be sent with smaller steps of incremental currents to increase the precision of proximity estimation.

The scientists observed that the users who received electrical pulses were much more aware of the proximity to the underlying surfaces and could reduce their contact force by about 70%, thus performing relatively better than the other group.

On the whole, the researchers noted that proximity data sent via gentle electric pulses was around three times more effective than that of the visual data alone.

According to Park, their innovative technique could dramatically increase maneuverability during surgical procedures and, at the same time, minimize the risks of any accidental damage caused to the tissues. Park also stated that their method would add little to the surgeons’ existing mental load during surgical procedures.

Our goal was to come up with a solution that would improve the accuracy in proximity estimation without increasing the burden of active thinking needed for this task. When our technique is ready for use in surgical settings, physicians will be able to intuitively know how far their robotic fingers are from underlying structures, which means that they can keep their active focus on optimizing the surgical outcome of their patients.

Hangue Park, Assistant Professor, Department of Electrical and Computer Engineering, Texas A&M College of Engineering

Other study contributors include Ziqi Zhao, Minku Yeo, and Stefan Manoharan from the Department of Electrical and Computer Engineering at Texas A&M College of Engineering and Seok Chang Ryu from Ewha Womans University based in South Korea.

Video Credit: Texas A&M College of Engineering

Journal Reference:

Zhao, Z., et al. (2020) Electrically-Evoked Proximity Sensation Can Enhance Fine Finger Control in Telerobotic Pinch. Scientific Reports. doi.org/10.1038/s41598-019-56985-9.