University of Utah Health Uses 3D Images and Automated Drill for Precise Brain Surgeries

Typically, I think of surgical procedures and getting my car fixed as two very different things, and they absolutely are, though both require precision and specific tools. But thanks to some groundbreaking research by a team at the University of Utah Health (U of U Health), a computer-driven, automated drill, like the kinds used to machine auto parts, could be used in future brain surgeries. The drill developed by the researchers can actually decrease the standard amount of time for one type of complex cranial surgery by 50 times, which gets the patient off the operating table faster and reduces the amount of a time the wound is open. The drill, which makes clean, fast, and safe cuts, can help lower the percentages of human error, chance of infection, and overall surgical cost.

Cranial surgeries can be especially complex, and surgeons usually add several hours to a procedure, because they need to use slow hand drills in order to make intricate openings. William Couldwell, MD, PhD, a U of U neurosurgeon, explained why a hand drill is used, and also the need to make the process much more efficient with a new kind of device.

William T. Couldwell, MD, PhD

“It was like doing archaeology. We had to slowly take away the bone to avoid sensitive structures,” Couldwell said.

“We knew the technology was already available in the machine world, but no one ever applied it to medical applications.”

Couldwell led an interdisciplinary research team as they worked to develop the robotic drill, which was made from scratch specifically for the neurosurgical unit; the team also developed innovative software that actually lays out a safe cutting path for the drill.

“My expertise is dealing with the removal of metal quickly, so a neurosurgical drill was a new concept for me. I was interested in developing a low-cost drill that could do a lot of the grunt work to reduce surgeon fatigue,” said A.K. Balaji, PhD and associate professor in mechanical engineering at U of U Health.

The research team published its findings in a paper, titled “Computer-aided design/computer-aided manufacturing skull base drill,” in the Journal of Neurosurgery; University of Utah co-authors include:

• William T. Couldwell, MD, PhD, Department of Neurosurgery
• Joel D. MacDonald, MD, Department of Neurosurgery
• Alagar K. Balaji, PhD, Department of Mechanical Engineering
• Bradley C. Hansen, PhD, Department of Mechanical Engineering
• Aniruddha Lapalikar, MS, Department of Mechanical Engineering
• Bharat Thakkar, MS, Department of Mechanical Engineering
• Charles L. Thomas, PhD, Department of Mechanical Engineering

The abstract reads, “The authors have developed a simple device for computer-aided design/computer-aided manufacturing (CAD-CAM) that uses an image-guided system to define a cutting tool path that is shared with a surgical machining system for drilling bone. Information from 2D images (obtained via CT and MRI) is transmitted to a processor that produces a 3D image. The processor generates code defining an optimized cutting tool path, which is sent to a surgical machining system that can drill the desired portion of bone. This tool has applications for bone removal in both cranial and spine neurosurgical approaches. Such applications have the potential to reduce surgical time and associated complications such as infection or blood loss. The device enables rapid removal of bone within 1 mm of vital structures. The validity of such a machining tool is exemplified in the rapid (< 3 minutes machining time) and accurate removal of bone for transtemporal (for example, translabyrinthine) approaches.”

In layman’s terms, a patient’s CT scan is used to collect bone data, which is then transformed into a 3D image; additionally, the exact location of sensitive structures like nerves and major arteries and veins is pinpointed in the 3D image. Surgeons take this information and program the drill’s cutting path, taking care to add in safety barriers within 1 mm of these sensitive locations.

Balaji explained, “The software lets the surgeon choose the optimum path from point A to point B, like Google Maps. Think of the barriers like a construction zone. You slow down to navigate it safety.”

Schematic of a method for using the automated drill system for surgery. NC = numeric control.

Just like a CNC mill, the drill quickly and accurately removes most of the bone; Couldwell said the process was similar to “Monster Garage,” except the surgeon is machining a skull instead of a car part. To test the drill out, Couldwell applied it to the complex translabyrinthine opening, a “jigsaw-like shape that circumnavigates the ear.”

“The access is through the temporal bone which is a hard bone with strange angles,” said Balaji.

The translabyrinthine surgery, which exposes benign but slow-growing tumors that form around the auditory nerves, is performed thousands of times a year. Couldwell said that surgeons need a lot of skill and experience to do so – the cutting path has to avoid facial nerves and the venous sinus, and risks include the patient losing facial movement.

Couldwell said, “We thought this procedure would be a perfect proof of principle to show the accuracy of this technology.”

An experienced surgeon can typically perform this difficult procedure, using a hand drill, in about two hours. However, by using the newly developed drill and 3D image planning system, that time can be reduced to less than three minutes, which lowers the chance for infection, reduces surgeon fatigue and surgery costs, and improves post-operative recovery.

The 3D images are displayed in a graphic interface so the surgeon can indicate the portion of bone or soft tissue to be machined.

The U of U Health research team focused on speed for the new drill, but also on safety: the device also features an automatic emergency shut-off switch, and monitors the facial nerve for any signs of irritation during the surgery.

Couldwell said, “If the drill gets too close to the facial nerve and irritation is monitored, the drill automatically turns off.”

A Technology Initiative Grant through the University of Utah funded the research, and the team is looking to commercialize the drill so it’s available in more hospitals for more procedures.

“This drill can be used for a variety of surgeries, like machining the perfect receptacle opening in the bone for a hip implant,” Couldwell explained.

Balaji was interested in the project due to the drill’s possible applications.

Balaji said, “I was motivated by the fact that this technology could democratize health care by leveling the playing field so more people can receive quality care.”

We’ve seen MRI and CT scan data used to make 3D images and models for surgical procedures before, but never quite like this. To take a look at the robotic drill in action, check out the U of U Health video. What do you think of this technology? Discuss in the U of U forum at 3DPB.com.