  Atrial fibrillation (AF) and ventricular tachycardia (VT) are two of the
sustained arrhythmias that significantly affect the quality of life of
patients. Treatment of AF and VT often requires radiofrequency ablation of
heart tissues using an ablation catheter. Recent progress in ablation therapy
leverages magnetic resonance imaging (MRI) for higher contrast visual feedback,
and additionally utilizes a guiding sheath with an actively deflectable tip to
improve the dexterity of the catheter inside the heart. This paper presents the
design and validation of an MR-conditional robotic module for automated
actuation of both the ablation catheter and the sheath. The robotic module
features a compact design for improved accessibility inside the MR scanner bore
and is driven by piezoelectric motors to ensure MR-conditionality. The combined
catheter-sheath mechanism is essentially a concentric tendon-driven continuum
robot and its kinematics is modeled by the constant curvature model for
closed-loop position control. Path following experiments were conducted to
validate the actuation module and control scheme, achieving < 2 mm average tip
position error.
