Coffee grounds have a variety of uses besides getting you buzzed, from removing smells from your fridge to fertilizing your garden. Nose and throat surgery isn't an obvious addition to that list, but a new invention by engineers at Vanderbilt University uses crushed coffee beans to make head surgery imaging technology more accurate.
"We originally called it the coffee helmet," says Richard Hendrick, a graduate student in the university's Medical Engineering and Discovery Lab, of his team's "granular jamming cap." The coffee-filled cap was created to solve a problem of technological precision.
In the past decade, image-guided surgery has revolutionized nose and throat surgeries, allowing doctors to track their instruments inside a patient's body in real time to avoid unnecessary cutting, especially in delicate endoscopic surgeries that work with tools inserted through the nose or through very small incisions. Today, the technology is used in nearly one million neurosurgical procedures annually. To work, however, surgeons need to be able to precisely map the area being operated on before the surgery. They CT or MRI scan their patient's head to build a 3-D model, and then they use a computer program to line up the model with the real patient on the operating table.
Often, this "registration" process is done by attaching targets called "fiducials," akin to the dots worn by actors who are transformed into CGI characters, to the patient's head to track his or her skull features. A camera above the patient realigns the 3D model based on the position of the dots, allowing doctors to look at a screen during the surgery and see in real-time where they are inside a patient’s head.
When done right, Hendrick says, these scanning technologies are accurate "down to less than a millimeter," but when observing surgeries, he and his team saw cases where surgeons would end up running their tools into areas that their screens told them they shouldn't be running into, meaning that the scanning was wrong. This can lead to the surgeries taking longer because surgeons can’t trust their tools anymore, Hendrick noted, and could cause accidental damage from misplaced cutting.
"We were looking at it like, 'What the heck is going on?'" says Hendrick. Eventually, they realized that the problem was with the registration process, specifically those dots. Any accidental movement of the dots during the scanning or surgery throws off the alignment of the 3D model, Hendrick says, and it was shockingly easy for that movement to happen because human skin is pliable and flexible and the skull is smooth and hard to grasp. Even a tight swim cap, Hendrick’s team found, was susceptible to small wiggles, whether from involuntary movement by a patient or cables snagging the cap, and a miscalibration of even millimeters could be enough to lead to a bad cut.
"The head is pretty much like an egg," Hendrick says. "There's not much geometry that we can grab onto well."
To solve this problem, Hendrick's team turned for inspiration to an innovative device created by Cornell University engineers in 2010. This "universal robotic gripper" uses a balloon filled with coffee grounds attached to a vacuum to create a "hand" that can grasp anything. The balloon and grounds are loose until the vacuum is activated, which pulls the coffee particles against each other tightly, forming an ad hoc solid. If the balloon is pressed against an object while loose, then activating the vacuum causes the coffee grounds to form a tight grip around that object.
Hendrick's team created a cap filled with coffee grounds to do the same thing with the head. When the air is vacuumed out of the cap, it forms a rigid seal on the head, preventing the dots attached to the cap from moving.
"It's really, really formed in a rigid way to the anatomy," says Hendrick, who has tried on the cap several times, describing it as feeling like having something “rock hard” attached to your head, but without any pain. “It's become something that's really improved the accuracy of these registrations by quite a bit.”
Hendrick's team has applied for a patent for its device, and is now looking for an industry partner to help get regulatory approval for it and bring it into operating rooms in the next few years. Soon, coffee could play a role in surgeries besides keeping the doctors awake.