Tiny robot tools powered by magnets could one day do brain surgery without cutting open the skull
- Written by Changyan He, Lecturer, School of Engineering, University of Newcastle
Most brain surgery requires doctors to remove part of the skull to access hard-to-reach areas or tumours. It’s invasive, risky, and it takes a long time for the patient to recover.
We have developed new, tiny robotic surgical tools that may let surgeons perform “keyhole surgery” on the brain. Despite their small size, our tools can mimic the full range of motion of a surgeon’s wrist, creating new possibilities for less-invasive brain surgery.
Tiny tools for brain surgery
Robotic surgical tools (around 8 millimetres in diameter) have been used for decades in keyhole surgery for other parts of the body. The challenge has been making a tool small enough (3mm in diameter) for neurosurgery.
In a project led by the University of Toronto, where I was a postdoctoral fellow, we collaborated with The Hospital for Sick Children (SickKids) in Canada to develop a set of very small neurosurgery tools.
The tools are only about 3mm in diameter. In a paper published in Science Robotics, we demonstrated these tools could grip, pull and cut tissue.
Their extremely small size is possible as they are powered not by motors but by external magnetic fields.
Current robotic surgical tools are typically driven by cables connected to electric motors. They work in much the same way as human fingers, which are manipulated by tendons in the hand connected to muscles in the wrist.
However, pulleys smaller than several millimetres wide to control the instruments are weak and prone to friction, stretch and fracture. This creates challenges in scaling down the instruments, because of difficulties in making the parts of the system, assembling the mechanisms and managing friction in the cables.
Magnetic controls
The new robotic system consists of two parts. The first is the tiny tools themselves: a gripper, a scalpel and a set of forceps. The second part is what we call a “coil table”, which is a surgical table with several electromagnetic coils embedded inside.
In this design, the patient would be positioned with their head on top of the embedded coils, and the robotic tools would be inserted into the brain via a small incision.
By altering the amount of electricity flowing into the coils, we can manipulate the magnetic fields, causing the tools to grip, pull or cut tissue as desired.
In open brain surgery, the surgeon relies on their own dexterous wrist to pivot the tools and tilt their tips to access hard-to-reach areas, such as removing a tumour inside the central cavity of the brain. Unlike other tools, our robotic neurosurgical tools can mimic this with “wristed” movements.
Surprising precision
We tested the tools in pre-clinical trials where we simulated the mechanical properties of the brain tissue they would need to work with. In some tests, we used pieces of tofu and raspberry placed inside a model of the brain.
We compared the performance of these magnetically operated tools with that of standard tools handled by trained surgeons.
We found the cuts made with the magnetic scalpel were consistent and narrow, with an average width of 0.3–0.4mm. That was even more precise than those from traditional hand tools, which ranged from 0.6 to 2.1mm.
The magnetic scalpel, shown slicing some tofu inside a model of the brain, can make cuts more precise than those done with traditional tools.
Changyan He
As for the grippers, they could pick up the target 76% of the time.
The magnetic grippers (shown here picking up some raspberry) were successful 76% of the time.
Changyan He
From the lab to the operating room
We were surprised by how well the robotic tools performed. However, there is still a long way to go until this technology could help patients. It can take years, even decades, to develop medical devices, especially surgical robots.
This study is part of a broader project based on years of work led by Eric Diller from the University of Toronto, an expert on magnet-driven micro-robots.
Now, the team wants to make sure the robotic arm and magnetic system can fit comfortably in a hospital operating room. The team also wants to make it compatible with imaging systems such as fluoroscopy, which uses x-rays. After that, the tools may be ready for clinical trials.
We’re excited about the potential for a new era of minimally invasive neurosurgical tools.
Authors: Changyan He, Lecturer, School of Engineering, University of Newcastle
