Ultrasound-guided navigation of a magnetic microrobot using acoustic phase analysis

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 closed-loop MR control, we propose a US contrast enhancement mechanism for MR visualization in heterogeneous and dynamic 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 closed-loop control of medical MRs in-vivo.

Real-time 3D optoacoustic tracking of cell-sized magnetic microrobots circulating in the mouse brain vasculature

“…To this end, several studies presented tracking of micro- and millirobots using established medical imaging modalities, such as magnetic resonance imaging ( 25 ), x-ray computed tomography ( 26 ), ultrasound (US) ( 27 ), optical imaging ( 28 , 29 ), and positron emission tomography ( 30 ). However, sensitive detection and 3D tracking of microrobots in the vascular system is hampered by their small size and inadequate spatiotemporal resolution of the imaging systems.…”