Closed-Loop Magnetic Manipulation for Robotic Transesophageal Echocardiography

TL;DR

The results obtained on a realistic cardiac tissue-mimicking phantom show that the proposed framework is applicable in real conditions and can generally meet the requirements for teleoperated TEE acquisitions.

Abstract

This paper presents a closed-loop magnetic manipulation framework for robotic transesophageal echocardiography (TEE) acquisitions. Different from previous work on intracorporeal robotic ultrasound acquisitions that focus on continuum robot control, we first investigate the use of magnetic control methods for more direct, intuitive, and accurate manipulation of the distal tip of the probe. We modify a standard TEE probe by attaching a permanent magnet and an inertial measurement unit sensor to the probe tip and replacing the flexible gastroscope with a soft tether containing only wires for transmitting ultrasound signals, and show that 6-DOF localization and 5-DOF closed-loop control of the probe can be achieved with an external permanent magnet based on the fusion of internal inertial measurement and external magnetic field sensing data. The proposed method does not require complex structures or motions of the actuator and the probe compared with existing magnetic manipulation methods. We have conducted extensive experiments to validate the effectiveness of the framework in terms of localization accuracy, update rate, workspace size, and tracking accuracy. In addition, our results obtained on a realistic cardiac tissue-mimicking phantom show that the proposed framework is applicable in real conditions and can generally meet the requirements for tele-operated TEE acquisitions.

Figures (11)

• Figure 1: (a) illustrates the procedure of conventional TEE acquisitions, where the echocardiographer manually grips the flexible shaft and adjusts the knobs on the probe handle to advance and steer the probe in the esophagus. (b) shows the proposed application scenario of the MA-TEE system, where the probe tip attached to a permanent magnet and an IMU sensor is manipulated by an external permanent magnet held by a robotic manipulator for tele-operated TEE acquisitions.
• Figure 2: The commonly used DOFs of the probe in clinical TEE acquisitions.
• Figure 3: Schematic of the MA-TEE system. Combining the measurements from the IMU internal to the probe and the magnetic field sensors external to the probe, the 6-DOF pose of the probe can be estimated in real time and 5-DOF control of the probe can be achieved through interactions between the magnets in the actuator and the capsule.
• Figure 4: The magnetic control workflow of our proposed MA-TEE system. After initialization, closed-loop control of the probe is performed by continuously updating the actuator's pose based on the user-specified desired probe pose and the real-time localization results.
• Figure 5: (a) shows the experimental setup of the proposed MA-TEE system. The actuator magnet is rigidly mounted at the end-effector of a UR5 robotic arm for closed-loop control of the probe in the simulated esophagus in a cardiac phantom. The workspace of the system is above the external sensor array placed on a horizontal platform. (b) is a closer look at the MA-TEE probe prototype. All dimensions are in millimeters () and (c) illustrates its components, including a TEE transducer, a cuboid permanent magnet and an IMU. The black dashed box in the lower right corner shows a dummy transducer fabricated for use in our quantitative experiments.