Abstract
Microrobots (MRs) have attracted significant interest for their potentialities in diagnosis and non-invasive intervention in hard-to-reach body areas. Fine control of biomedical MRs requires real-time feedback on their position and configuration. Ultrasound (US) imaging stands as a mature and advantageous technology for MRs tracking, but it suffers from disturbances due to low contrast resolution. To overcome these limitations and make US imaging suitable for monitoring and tracking MRs, we propose a US contrast enhancement mechanism for MR visualization in echogenic backgrounds (e.g., tissue). Our technique exploits the specific acoustic phase modulation produced by the MR characteristic motions. By applying this principle, we performed real-time visualization and position tracking of a magnetic MR rolling on a lumen boundary, both in static flow and opposing flow conditions, with an average error of 0.25 body-lengths. Overall, the reported results unveil countless possibilities to exploit the proposed approach as a robust feedback strategy for monitoring and tracking biomedical MRs in-vivo.
Highlights
Microrobots (MRs) have attracted significant interest for their potentialities in diagnosis and noninvasive intervention in hard-to-reach body areas
The translation of microrobotics technologies to the clinics is hampered by the lack of suitable medical imaging strategies to provide robust and precise feedback for monitoring and control p urposes[4,5]
The proposed US contrast enhancement strategy employed for imaging and tracking is based on the specific acoustic phase modulation produced by MR motions
Summary
Microrobots (MRs) have attracted significant interest for their potentialities in diagnosis and noninvasive intervention in hard-to-reach body areas. Several medical imaging techniques have been considered for this p urpose[10], ranging from traditional techniques (e.g., M RI11 or radiation-based12) to innovative ones, such as p hotoacoustic[13] or magnetic particle imaging[14] In this framework, medical ultrasound (US) stands as a mature technology that combines real-time capabilities with a good spatial resolution (100–500 μm), deep tissue imaging (up to 25 cm far from the probe), no adverse health effects, and low equipment cost[15], being a good candidate for tracking microrobots (MRs) inside the body. Exploiting the specific acoustic phase modulation produced by characteristic MR motions, e.g., vibrations, can help to address this limitation by enabling to isolate MR displacements from background motions, and enabling robust MR d etection[30] This strategy can provide a contrast-enhancing mechanism for improved MR tracking in echogenic and dynamic backgrounds, where traditional US imaging modalities fail. The proposed detection strategy allowed to perform continuous MR tracking even in the presence of high contrast imaging artifacts by robustly detecting its centroid position over time and deriving features such as size and rotation frequency
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