Abstract-This article introduces a robotic manipulator to realize robot-assisted intra-cardiac catheterization in magnetic resonance imaging (MRI) environment. MRI can offer highresolution images to visualize soft tissue features such as scars or edema. We hypothesize that robotic catheterization, combined with the enhanced monitoring of lesions creation using MRI intraoperatively, will significantly improve the procedural safety, accuracy and effectiveness. This is designed particularly for cardiac electrophysiological (EP) intervention, which is an effective treatment of arrhythmia. We present the first MR Safe robot for intra-cardiac EP intervention. The robot actuation features small hysteresis, effective force transmission and quick response, which has been experimentally verified for its capability to precisely tele-manipulate a standard clinically used EP catheter. We also present timely techniques for real-time positional tracking in MRI and intra-operative image registration, which can be integrated with the presented manipulator to improve the performance of tele-operated robotic catheterization.Index Terms-MR Safe robot, robot-assisted intervention, MR image registration, positional tracking in MRI.

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Magnetic resonance imaging (MRI)-guided intervention has drawn increasing attention over the last decade.It is accredited to the capability of monitoring any physiological change of soft tissue with the high-contrast MR images. This also gives rise to the demand for precise tele-manipulation of interventional instruments. However, there is still lack of choices of MR safe actuators that provide high-fidelity robot manipulation. In this paper, we present a three-cylinder hydraulic motor using rolling-diaphragm-sealed cylinders, which can provide continuous bidirectional rotation with unlimited range. Both kinematics and dynamics models of the presented motor were studied, which facilitate its overall design optimization and position/torque control. Motor performance, such as step response, frequency response, and accuracy, were experimentally evaluated. We also integrate the motor into our catheter robot prototype designed for intra-operative MRI-guided cardiac electrophysiology (EP), which can provide full-degree-of-freedom and precise manipulation of a standard EP catheter.