Researchers from the University of Leeds in the UK have developed miniature, laser carrying robots that can travel deep into the lungs, giving them the potential to transform the treatment of lung cancer using a minimally invasive approach. The personalized, ultra-soft magnetic tentacles measure just 2.4 mm in diameter and are driven by two external permanent magnets.
“My group has been working on magnetic actuation for the last 18 years,” Professor Pietro Valdastri, director of the STORM Lab at the University of Leeds, tells Inside Precision Medicine.
“This is a strategy that allows extreme miniaturization for the robot that goes inside the body as it gets moved by external magnetic fields [removing the] need to integrate structures like cables to create motion,” he explains. “In the past, we worked with a single magnet inside the body of the patient and a single larger magnet outside, controlling the one inside in a wireless fashion. More recently, we got interested in using more complex fields with two external permanent magnets to control multiple points of a soft robot inside the body of the patient.”
This unique aspect of the work allows the researchers to shape and control a tentacle to reach deep into the lungs.
The magnetic tentacles are delivered to the lungs via a standard 6 mm diameter bronchoscope and the tip of the bronchoscope is localized using a magnetic field sensor. At the same time, integrated shape sensing uses an optical sensor to provide information about the shape of the tentacle. With this, the researchers can ensure the tentacle has the correct shape. If it needs to be changed, the external field can be corrected to make this happen.
Once inserted, the magnetic particles use a process called autonomous navigation to reach the tumor.
“We have a navigation plan based on pre-operative imaging,” says Valdastri. “In other words, the patient goes for a magnetic resonance imaging or computed tomography (CT) scan, then we take the images of the lungs and we recreate a 3D volume from where we extract a map of the bronchi and plan the path that the tentacle should navigate.
“Thanks to this plan and the integrated shape sensing, we can navigate the tentacle autonomously,” he notes, likening the process to that of an autonomous car driving from point A to point B following a pre-planned route but adapting to the real-world scenario thanks to real-time sensing—in this case the integrated shape sensing.
To test the robots, Valdastri and team first created an anatomically accurate 3D printed model of a lung using CT imaging data. They report in Nature Communications Engineering that the magnetic tentacles successfully navigated four representative sub-segmental bronchi in the left bronchial tree and four in the right bronchial tree. The authors note that these areas “are problematic to explore with standard rigid tools without deforming the surrounding anatomy, which may result in more invasive navigation and mistargeting of the tumor, since targeting is performed via localization in a precomputed map of the bronchi and deformation may impact its efficacy.”
They then showed that it was possible to deploy a 1064 nm laser light, via optical fibers embedded in the tentacle, that had sufficient power to cause heating for photothermal ablation of a tumor.
Finally, the team evaluated the approach in three diverse branches of excised cadaveric lungs and showed that, thanks to the small diameter, the tentacles could travel 37% deeper into the lung with less tissue damage than a standard semi-rigid catheter.
The report’s co-author, Dr Giovanni Pittiglio, who carried out the research while conducting his PhD at the University of Leeds’s School of Electronic and Electrical Engineering, says: “Our goal was, and is, to bring curative aid with minimal pain for the patient.
“Remote magnetic actuation enabled us to do this using ultra-soft tentacles which can reach deeper, while shaping to the anatomy and reducing trauma.”
Each of tentacles are magnetized in a way that would allow it to navigate in the specific anatomy of a single patient, as extracted from pre-operative imaging. This means that a new set needs to be fabricated for each patient, but Valdastri notes that the process is fast and inexpensive, taking place in just a few hours using silicone plastic.
The researchers now need to evaluate the technology in animal models to assess the effect breathing might have on the magnetic navigation. These tests, which may take up to 2 years will also evaluate safety.
“After that, we can pursue first-in-human trials on a limited number of volunteers to show safety, then, if all is successful, large human trials to compare our technology with the clinical standard,” said Valdastri. “So, pending financial support, the earliest this technology can reach patients is about 4 to 5 years.”
The researchers are also investigating whether two magnetic tentacles can be used and controlled independently so that one could move a camera, while the other could direct a laser onto a tumor. These experiments are being carried out using a replica of a skull as a model for endonasal brain surgery.
Zaneta Koszowska, a researcher in the University of Leeds School of Electronic and Electrical Engineering, and team showed that they were able to simulate the removal of a benign tumor on the pituitary gland at the base of the cranium, proving for the first time ever that it is possible to control two of the robots in one confined area of the body.
Their findings are published in Advanced Intelligent Systems.
