Montreal, February 14, 2024—Canadian researchers led by Montreal radiologist Gilles Soulez have developed a novel approach to treat liver tumours using magnet-guided microrobots in an MRI device.

The idea of injecting microscopic robots into the bloodstream to heal the human body is not new. It’s also not science fiction.

Guided by an external magnetic field, miniature biocompatible robots, made of magnetizable iron oxide nanoparticles, can theoretically provide medical treatment in a very targeted manner.
Until now, there has been a technical obstacle: the force of gravity of these microrobots exceeds that of the magnetic force, which limits their guidance when the tumour is located higher than the injection site.

While the magnetic field of the MRI is high, the magnetic gradients used for navigation and to generate MRI images are weaker.

“To solve this problem, we developed an algorithm that determines the position that the patient’s body should be in for a clinical MRI to take advantage of gravity and combine it with the magnetic navigation force,” said Dr. Gilles Soulez, a researcher at the CHUM Research Centre and director of the radiology, radio-oncology and nuclear medicine department at Université de Montréal.

“This combined effect makes it easier for the microrobots to travel to the arterial branches which feed the tumour,” he said. “By varying the direction of the magnetic field, we can accurately guide them to sites to be treated and thus preserve the healthy cells.”

Toward greater precision

Published in Science Robotics, this proof of concept could change the interventional radiology approaches used to treat liver cancers.

The most common of these, hepatocellular carcinoma, is responsible for 700,000 deaths per year worldwide, and is currently most often treated with transarterial chemoembolization.

Requiring highly qualified personnel, this invasive treatment involves administering chemotherapy directly into the artery feeding the liver tumour and blocking the blood supply to the tumour using microcatheters guided by X-ray.

“Our magnetic resonance navigation approach can be done using an implantable catheter like those used in chemotherapy,” said Soulez. “The other advantage is that the tumours are better visualized on MRI than on X-rays.”

For this study, Soulez and his research team collaborated with those of Sylvain Martel (Polytechnique Montreal) and Urs O. Häfeli’s (University of British Columbia). The study’s first author, Ning Li, is a postdoctoral fellow in Dr. Soulez’s laboratory.

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