Posted in | News | Medical Robotics

Magnet-Guided Microrobots Navigate Arteries to Treat Liver Tumors

Under the direction of Gilles Soulez, a radiologist in Montreal, Canadian researchers have created a novel method for treating liver tumors with magnet-guided microrobots integrated into an MRI machine.

Dr. Gilles Soulez and Ning Li. Image Credit: Centre Hospitalier de l’Université de Montréal (CRCHUM)

The notion of delivering tiny robots directly into the bloodstream to treat human ailments is not a novel one. It is not science fiction, either.

Miniature biocompatible robots composed of magnetizable iron oxide nanoparticles have the potential to deliver highly targeted medical treatment when guided by an external magnetic field.

Up until now, there has been a technical barrier: when the tumor is situated higher than the injection site, the microrobots’ guidance is limited because their gravitational force is greater than their magnetic force.

The magnetic gradients used for navigation and the creation of MRI images are weaker despite the MRI's high magnetic field.

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

Dr. Gilles Soulez, Researcher and Director, CHUM Research Center, Radio-oncology and Nuclear Medicine Department, Université de Montréal

Toward Greater Precision

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

The most prevalent of these, hepatocellular carcinoma, is currently treated primarily with transarterial chemoembolization and accounts for 700,000 deaths annually globally.

This invasive treatment, which calls for highly skilled workers, entails inserting chemotherapy directly into the artery supplying the liver tumor and using X-ray-guided microcatheters to cut off the tumor's blood supply.

Our magnetic resonance navigation approach can be done using an implantable catheter like those used in chemotherapy. The other advantage is that the tumors are better visualized on MRI than on X-Rays.

Dr. Gilles Soulez, Researcher and Director, CHUM Research Center, Radio-oncology and Nuclear Medicine Department, Université de Montréal

Soulez and the research team worked with Urs O. Häfeli's (University of British Columbia) and Sylvain Martel’s (Polytechnique Montréal) teams on this study. Ning Li, the first author of the study, works as a Postdoctoral Fellow in Dr. Soulez’s lab.

The scientists were able to put together “particle trains,” or collections of magnetizable microrobots, because they developed an MRI-compatible microrobot injector. These are simpler to control and identify on the MRI machine’s images because they have a stronger magnetic force.

By doing this, the scientists can make sure that the treatment dose is appropriate in addition to ensuring that the train is moving in the correct direction. It is critical for radiologists to be aware of the number of microrobots because, over time, each one will carry a portion of the treatment to be administered.

A Good Sense of Direction

We carried out trials on twelve pigs in order to replicate, as closely as possible, the patient’s anatomical conditions. This proved conclusive: the microrobots preferentially navigated the branches of the hepatic artery which were targeted by the algorithm and reached their destination.

Dr. Gilles Soulez, Researcher and Director, CHUM Research Center, Radio-oncology and Nuclear Medicine Department, Université de Montréal

The team ensured that the tumor’s location in various liver regions did not affect how effective this method was.

Soulez says, “Using an anatomical atlas of human livers, we were able to simulate the piloting of microrobots on 19 patients treated with transarterial chemoembolization. They had a total of thirty tumors in different locations in their livers. In more than 95% of cases, the location of the tumor was compatible with the navigation algorithm to reach the targeted tumor.”

The clinical application of this technology is still a long way off despite the advancements in science.

Soulez says, “First of all, using artificial intelligence, we need to optimize real-time navigation of the microrobots by detecting their location in the liver and also the occurrence of blockages in the hepatic artery branches feeding the tumor.”

Researchers will also need to use software that replicates fluid flow through vessels to model blood flow, patient positioning, and magnetic field direction. This will increase the accuracy of the approach by enabling the evaluation of how these parameters affect the microrobots' transportation to the target tumor.

In 2023, 4,700 Canadians received a liver or intrahepatic bile duct cancer diagnosis, according to the Canadian Cancer Society.

Journal Reference

Li, N., (2024) Human-scale navigation of magnetic microrobots in hepatic arteries. Science Robotics.


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