Angiography is a widely used medical imaging technique that allows medical researchers and doctors to capture the vascular network (i.e., blood vessels) using contrast agents, substances that enhance the visibility of specific structures inside the body when exposed to X-rays or other imaging approaches. Conventional angiography techniques rely on contrast agents that are distributed through blood vessels, leveraging the natural flow of blood in the body.
Despite their widespread use, these approaches have significant limitations. For instance, they struggle to visualize upstream regions (i.e., regions in blood vessels that are against the direction of the blood flow) or areas that are blocked by materials (e.g., blood clots). This inability to visualize some regions limits the use of angiography for diagnosing and planning the treatment of some vascular conditions, including narrowed vessels, blood clots and abnormal connections between vessels.
Researchers at the Shenzhen Institute of Artificial Intelligence and Robotics for Society and the Chinese University of Hong Kong recently introduced a new method for exploring and reconstructing vascular networks utilizing swarms of magnetic microrobots. Their proposed approach, outlined in a paper published in Nature Machine Intelligence, enables the 3D imaging of vascular networks, including upstream regions and blocked areas.
“Angiography is essential in interventional operations to image the vascular network. Passive contrast agents applied in angiography highly rely on the flow direction, making the imaging of upstream regions and embolic branches challenging,” wrote Xingzhou Du, Yibin Wang and their colleagues in their paper.
“Active imaging is demanded for the accurate localization of blockages and lesions in vascular networks. Here an active exploration and reconstruction strategy is proposed, enabling full imaging of three-dimensional (3D) vascular networks with flow and blockage.”
Compared to conventional techniques that rely on passive contrast agents (i.e., substances that passively move following the blood flow), the approach devised by the researchers relies on swarms of active agents. These active agents are essentially magnetic particles, which can be controlled using external magnetic fields, reaching areas that cannot be accessed by passive agents.
“The strategy implements magnetic particle swarms as active agents, which can be guided on demand towards the desired directions,” wrote the researchers. “An image processing unit is developed to capture the 3D position of the swarm inside the vessel. A simultaneous mapping and exploration sequence is proposed to realize the exploration, and the entire structure of the 3D vascular network is reconstructed after obtaining the position data.”
Du, Wang and their colleagues evaluated the potential of their new active imaging technique in a series of tests, which yielded promising results. Notably, their technique was found to produce detailed 3D reconstructions of vascular systems, even in the presence of blockages.
“The proposed strategy is validated in vascular networks with different structures and conditions, and it enables the thorough exploration and reconstruction of regions that cannot be accessed by passive contrast agents,” wrote the researchers. “This strategy is promising in locating stenoses, thrombi and fistulae in vascular systems.”
In the future, the new microrobot swarm-based imaging approach devised by this team of researchers could be tested in further experiments and eventually deployed in health care facilities. Ultimately, it could significantly advance the diagnosis and treatment of a variety of vascular conditions, helping doctors to rapidly locate blood clots and other vascular abnormalities, to then plan targeted interventions.
More information:
Xingzhou Du et al, Active exploration and reconstruction of vascular networks using microrobot swarms, Nature Machine Intelligence (2025). DOI: 10.1038/s42256-025-01012-y
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Magnetic microrobot swarm enables 3D imaging of vascular networks (2025, April 9)
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