Investigation of active tracking for robotic arm assisted magnetic resonance guided focused ultrasound ablation

Background Focused ultrasound surgery (FUS) is a technique that does not need invasive access to the patient while allowing precise targeted therapy. Magnetic resonance (MR) guided FUS provides capabilities for monitoring treatments. Because the targeted tumours are distributed at different positions, focus repositioning becomes necessary. Methods An MR compatible robot was used to increase the operational range of FUS application. Active tracking was developed to detect the robotic arm with regard to the MR coordinate system. The purpose of this study was to construct active tracking to allow a wide spatial range of repositioning the FUS transducer that is fast and accurate. The technique was characterised and validated by a series of positioning tests to prove its efficiency for guiding the robot. Results In the calibration range, tracking achieved an RMS accuracy of 0.63 mm. Results of phantom ablation showed a focal scanning precision Δx = 0.4 ± 0.37 mm, Δy = 0.4 ± 0.28 mm and Δz = 0.7 ± 0.66 mm. Conclusions The active tracking localisation can be considered a feasible approach for the MR guided FUS system positioned by a robot. Copyright © 2016 John Wiley & Sons, Ltd.