Scientists use microrobots in MRI device to treat liver cancer

New Delhi: Researchers in Canada have developed a novel approach to treat liver cancers using magnet-guided microrobots in an MRI device.

Guided by an external magnetic field, miniature biocompatible robots, made of iron oxide nanoparticles, can theoretically provide medical treatment in a very targeted manner, the researchers said.

However, 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, they said.

"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 Gilles Soulez, a researcher at the University of Montreal.

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

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technology that produces three-dimensional detailed anatomical images.

The new approach, published in the journal Science Robotics, could change the interventional radiology approaches used to treat liver cancers, the researchers said.

The most common of these, hepatocellular carcinoma, is responsible for seven lakh deaths per year worldwide, and is currently most often treated with transarterial chemoembolization, they said.

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, according to the researchers.

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

Thanks to the development of an MRI-compatible microrobot injector, the scientists were able to assemble "particle trains," aggregates of magnetisable microrobots. As these have a greater magnetic force, they are easier to pilot and detect on the images provided by the MRI device.

In this way, the scientists can ensure not only that the train is going in the right direction, but also that the treatment dose is adequate.

"We carried out trials on 12 pigs in order to replicate, as closely as possible, the patient's anatomical conditions," said Soulez.

"This proved conclusive: the microrobots preferentially navigated the branches of the hepatic (liver) artery which were targeted by the algorithm and reached their destination," he added.