A Robotic Platform to Navigate MRI-guided Focused Ultrasound System

Focused ultrasound (FUS) technology attracts increasing interests accrediting to its non-invasive and painless treatment of tumors. Magnetic resonance imaging (MRI) guidance has been introduced to monitor this procedure, thus allowing the ultrasound foci to be precisely controlled. However, manual positioning of the FUS transducers is challenging, especially for the intra-operative (intra-op) adjustment in the MRI room. Currently, there are very few devices capable to provide robotic transducer positioning for the treatment of abdominopelvic organ diseases under MRI. The high intensity focused ultrasound (HIFU) spot would have to be "steered" to ablate large (>Ø 3.5 cm) or multiple tumors (e.g., in liver). To this end, we proposed a hydraulic-driven tele-operated robot platform that enables 5-DoF manipulation of the FUS transducer. Even operated close to the MRI iso-center, the robot can guarantee zero electromagnetic (EM) artifact to the MR image. Our proof-of-concept robot prototype can offer a large workspace (100 mm × 100 mm × 35 mm) for FUS foci steering. Accurate manipulation (0.2 mm in translation, 0.4° in rotation) of the FUS transducer holder is achieved using rolling diaphragm-sealed hydraulic actuators. The robot control responsiveness (from 0.1 to 4 Hz) is also evaluated to show the potential to compensate for the spot tracking error induced by respiratory motion. We also demonstrate the use of wireless radiofrequency (RF) markers to continuously register the robot task space in the MRI coordinates.