Steady hands and uninterrupted, sharp vision are critical when performing surgery on delicate
structures like the brain or hair-thin blood vessels.
While surgical cameras have improved what surgeons see during operative procedures,
the “steady hand” remains to be enhanced — new surgical technologies, including sophisticated
surgeon-guided robotic hands, cannot prevent accidental injuries when operating close to
fragile tissue.
In a new study published in the journal Scientific Reports, researchers at Texas A&M University
show 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 researchers said that this technique might be an effective way to help surgeons reduce
inadvertent injuries during 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 this new 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.
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 that 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 for their hands
in the patient’s body during operations.
To move their robotic fingers precisely, surgeons rely on live streaming of visual information
from cameras fitted on telerobotic 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 critical
when the fingers are in the close vicinity of the brain or other delicate tissue.
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.
To address this problem, the research 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 researchers also tailored their technology according to the user’s sensitivity to electrical
current frequencies.
In other words, 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 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.
This novel approach has the potential to significantly increase maneuverability during surgery while
minimizing risks of unintended tissue damage.