Mobile Ultrasound Tracking and Magnetic Control for Long‐Distance Endovascular Navigation of Untethered Miniature Robots against Pulsatile Flow

Abstract

Long‐distance endovascular navigation of miniature robots under the guidance of medical imaging modalities is essential for microrobotic targeted delivery in the human body. Herein, a scheme on this topic based on mobile ultrasound (US) tracking and magnetic control is proposed. Considering the narrow 2D imaging of a US probe and the fast decay of the magnetic field, the US probe is integrated with three electromagnetic coils for simultaneous long‐distance tracking and control of untethered miniature robots. To enable robust tracking with pulsatile flow, a tracking strategy consisting of tracking in and perpendicular to the image plane is designed. In the image plane, an iterative statistics‐based strategy is proposed to extract the position and orientation of the robot from the US imaging. For the direction perpendicular to the US image plane, the probe motion is automatically adjusted according to the tracking quality. Based on the real‐time tracking result, demanded rotating fields are generated by the mobile coils for helical propulsion. The proposed scheme is implemented on a full‐scale silicone phantom of human iliac and aorta arteries with blood‐mimicking fluid and pulsatile flow. Experimental results validate the robustness and the effectiveness of the proposed scheme.

Closed‐Loop Control Characterization of Untethered Small‐Scale Helical Device in Physiological Fluid with Dynamic Flow Rates

“…In this work, we report a closed-loop control strategy to navigate the USHD in physiological fluid with dynamic flow rates using ultrasound imaging. Compared with other USHD in the blood vessel phantom, [10,18,29] we model the dynamic flow as the bounded exogenous disturbance signal and quantify the ultrasound images noise using CNR, and then we analyze closed-loop control characterization of the USHD inside a blood vessel phantom at different penetration depths with dynamic flow. In addition, our PMR system has large workplace, and we don't need to consider the problem of electromagnetic coil heating, so it can be used to drive the USHD for a long time.…”

“…∠m∶ ¼ ∠BðpÞ. (10) The relationship between the applied field and the orientation of the USHD can be used to design a closed-loop control system to change field rotation axis and orients it toward the desired reference position. In this case, a prescribed trajectory along the vessel will provide waypoints.…”

“…[6,7] Compared with traditional surgery, USHDs are expected to enable interventions with minimal trauma and relatively fast postoperative recovery. For medical USHDs, many proposed actuation mechanisms have been studied, such as magnetic fields, [8][9][10] chemical fuels, [11,12] light energy, [13] enzymatic, [14] and acoustic wave. [15] Among these actuation mechanisms, USHDs driven by magnetic fields have been extensively studied for two key reasons.…”

Control of Self-Winding Microrobot Using an Electromagnetic Drive System: Integration of Movable Electromagnetic Coil and Permanent Magnet

“…Briefly, the requirement for two layers with distinct physical properties, such as Young's modulus, coefficient of thermal expansion, density, and pH, leads to constraints associated with material selection and extended printing times [20][21][22][23]. Utiliz- Using a delta-driven structure, multiple coils are strategically positioned close to the starting point of the designated track [17][18][19]. These coils generate the required magnetic field to align the microrobot for motion.…”

Magnetically Actuated Continuum Medical Robots: A Review

“…[71,112,113] Another platform is the DeltaMag system, which integrates an array of three electromagnets into a parallel manipulator (Figure 5f ). [114][115][116] The enlarged workspace is realized by motion control, and the field generation is achieved by current control. It has the ability to produce both static and dynamic magnetic fields.…”