Abstract
This work presents an approach for the localization and control of helical robots during removal of superficial blood clots inside in vitro and ex vivo models. The position of the helical robot is estimated using an array of Hall-effect sensors and precalculated magnetic field map of two synchronized rotating dipole fields. The estimated position is used to implement closed-loop motion control of the helical robot using the rotating dipole fields. We validate the localization accuracy by visual feedback and feature tracking inside the in vitro model. The experimental results show that the magnetic localization of a helical robot with diameter of 1 mm can achieve a mean absolute position error of 2.35 ± 0.4 mm (n = 20). The simultaneous localization and motion control of the helical robot enables propulsion toward a blood clot and clearing at an average removal rate of 0.67 ± 0.47 mm3/min. This method is used to localize the helical robot inside a rabbit aorta (ex vivo model), and the localization accuracy is validated using ultrasound feedback with a mean absolute position error of 2.6 mm.
Highlights
In this work, we localize helical robots with a diameter of 1 mm using an array of Hall-effect sensors and the precalculated magnetic field map of a permanent magnet-based robotic system.[26]
The simultaneous localization and motion control of the helical robot enables propulsion toward a blood clot and clearing at an average removal rate of 0.67 6 0.47 mm3/min. This method is used to localize the helical robot inside a rabbit aorta, and the localization accuracy is validated using ultrasound feedback with a mean absolute position error of 2.6 mm
The helical robot is actuated using two rotating dipole fields and localized while it is swimming inside a catheter segment or a rabbit aorta via an array of Hall-effect sensors
Summary
Our system (Fig. 2) comprises in vitro and ex vivo models of the blood vessel, a permanent magnet-based robotic system, and an array. Blood clots (1-h-old) are inserted into the catheter segment in each trial and PBS is injected at a flow rate of 10 ml/h, using a dual syringe pump (Genie Plus, GT-4201D-12, Kent Scientific, Connecticut, USA). This flow rate is devised based on the administration and infusion rates for adult patients.[35]. The relation between the geometric shape of the robot and the swimming speed has been characterized experimentally by Zhang et al and Tottori et al.[6,7] The robot is actuated using two synchronized rotating dipole fields These fields are generated using permanent NdFeB magnets with a diameter of 20 mm and length of 20 mm, and axial magnetization. The distance between the adjacent sensors is 1 mm, and their sensitivity is 0.1 mT within a range of 6130 mT (Table I)
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