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Queen's students developing new neurosurgical aid
Subdural hematoma is the collection of blood escaped from injured veins inside the skull between the surface of the brain and its outer covering. That collection of blood can displace the brain and cause pressure to build up inside the skull, impinging blood circulation in brain tissue and potentially causing permanent neurological damage or death.
It’s usually caused by trauma – a blow to the head or an acceleration/deceleration-injury that forces the brain hard against the inside of the skull – and it’s a very dangerous, life-threatening condition. In most cases, the treatment is emergency surgery. A neurosurgeon needs to make an opening in the skull to drain or extract the hematoma in order to preserve blood flow to the affected areas of the brain. If the hematoma is small enough, a small burr hole or two, each just a few millimetres across, drilled through the skull is enough to do the job. Surgeons use sophisticated diagnostic imaging tools and techniques to ensure they place those burr holes precisely in the best locations. But that can be a complex and time-consuming process at a time when every second counts and not every hospital is equipped with state-of-the-art neuronavigation systems.
Now, a research group at Queen’s, Laboratory for Percutaneous Surgery (Perk Lab), is developing a new and novel suite of tools to help neurosurgeons in the operating room to visualize more easily and quickly where a hematoma is in relation to other critical structures in the head, and where best to place necessary burr holes. They’re doing it by adapting some promising consumer-level technology: the Microsoft HoloLens.
The HoloLens is an augmented reality headset introduced to consumers in 2016. Unlike consumer virtual reality headsets like the Oculus Rift or HTC Vive, that substitute visual information to create a complete virtual experience, the HoloLens projects virtual objects into the user’s real-world field of view, augmenting what the user sees but not replacing it.
“Usually a surgeon looks at two-dimensional images on a screen at the side of the operating room to mentally register the optimal positioning for burr holes,” says Queen’s undergraduate researcher, Emily Rae (Sc’ 18). “We intend to use the Microsoft HoloLens to superimpose a patient’s internal anatomy directly onto the surgeon’s view of the patient as they lay on the operating table. This technique simplifies the mental registration process because surgeons can actually see the patient’s anatomy from the scans right there on the table in front of them.”
It works like this: the surgeon looks at the patient on the operating table through the HoloLens headset and sees a holographic representation of the patient’s anatomy and hematoma superimposed over the patient’s skin. The surgeon then uses an Xbox controller to align the virtual structures in three dimensions precisely on the patient’s head. That way the surgeon can mark out where the burr holes should be placed.
“Moving forward with the project there is definitely potential to use the HoloLens in other procedures or in other fields of medicine, whether it be for training purposes or in the operating room. ”- Emily Rae (Sc '18)
Rae started exploring this application for the HoloLens in the Laboratory as an undergraduate research project last summer under the supervision of Queen’s professor and Cancer Care Ontario Research Chair, Dr. Gabor Fichtinger. Her work in the first year of this project involved mostly software development and accuracy testing conducted in the lab on mannequins. Rae will begin work on her Master’s degree at The University of Strathclyde in Glasgow in September, so Queen’s Master’s student Zac Baum (Comp ’17, MSc ’19) will be continuing work on the project moving forward through the fall.
“My side of the project are the clinical trials, which means I get to go into the operating room and interact with surgeons, residents, and medical students,” says Baum. “I put the HoloLens on the learners’ heads so they can use it to plan the surgery: how they’re going to go in, where they should place burr holes.”
The neurosurgeon for the clinical trial is Queen’s School of Medicine Assistant Professor, Dr. Ron Levy.
Baum says feedback from surgical teams is positive so far but, as with every iterative design process, there are technical challenges to overcome. First among them is that developers do not have access to the raw sensor data used by the headset's spatial tracking software. This limits the level of accuracy that is achievable for positioning virtual objects in the room relative to the user. With access to this raw data, or an improved tracking system in future versions of the headset, it's hoped that developers will be able to lock objects into place with more stability and higher accuracy.
A second challenge is that the first-generation HoloLens provides only a 35-degree field of view to display virtual objects in front of the user. This requires surgeons to position their heads such that the objects are in the field of view. While standing over an operating table looking down at a patient, this means the surgeon can no longer use their peripheral vision as they normally would, and results in an uncomfortable stance.
“We’ve had some difficulty with the holograms shifting a little as the surgeon moves around the room,” says Rae. “Microsoft is coming out with its second version of the HoloLens in a year or so. We’re hoping that those aspects will be improved. A lot of other developers are having the same issues right now.”
For Rae and Baum, this work represents their efforts moving from the theoretical to real-world application.
“It’s a very unique and different experience to see something we helped work on have a positive effect on patient outcomes, if things continue to go well,” says Baum. “Being an undergraduate student like Emily, or Master’s student like myself, going into the operating room and seeing technology that the students in our lab have on worked put to good use is very satisfying.”
It’s a satisfying process for their academic supervisor as well.
“I’m very proud of the chain of responsibility that we have been able to delegate to students in the Perk Lab and Emily and Zac are performing very efficiently, responsibly, and brilliantly,” says Dr. Fichtinger. “Undergraduates like Emily seldom see their course projects showing up the operating room, so I take pride in their achievement.”
Learn more about the The Laboratory of Percutaneous Surgery (Perk Lab)
NEW TOOLS: Queen’s Master’s student Zac Baum and undergraduate researcher Emily Rae are working on a quick and simplified technique for burr hole placement for neurosurgical applications.
AUGMENTED REALITY: The Microsoft HoloLens superimposes holographic representations of the patient’s anatomy over the surgeon’s field of view so they can more easily envision the best placement of burr holes for the treatment of subdural hematoma.
REGISTRATION: Queen’s School of Medicine neurosurgeon, Dr. Ron Levy, uses an Xbox controller to position virtual objects precisely on the on the patient’s skin to determine the best places for necessary burr holes.