A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber

Omar Curiel, Jing-Yuan Huang, Po-Chih Chen, Ji Ma, Qing Dai, Wenqi Zhou, David Lu, Holden H. Wu, Tsu-Chin Tsao · N/A · 2026

Summary

Abstract Summary

We present a MR safe, master-slave robot manipulator for abdominal interventions in the MRI chamber. A human operated 2+1-DoF master controller manipulator transmits motion and force to a 2+1-DoF slave manipulator via fluid transmission. Jointly, a digital master controller provides multimodal control capability beyond common split axis or mode switchable hybrid human-digital controller configurations found in previous studies. High input impedance, low-leakage, elastomeric fluid actuators are delegated to remote angulation control. Low-friction graphite piston cylinders are delegated to needle insertion axis remote actuation given the sub-newton force transparency and sub-millimeter motion transmission over bedside fluid piping lengths. The device enables real-time MRI guided interventions allowing manual, digital, hybrid, and collaborative control modes. Collaborative tasks such as assisted tissue penetration, fault-driven virtual fixture, and motion compensation through feedback control are presented in this paper. Preliminary MR scanner results demonstrate manipulator functional viability for an in-vivo pig experiment in bedside, manual control mode configuration.

Key Points

We present a MR safe, master-slave robot manipulator for abdominal interventions in the MRI chamber
A human operated 2+1-DoF master controller manipulator transmits motion and force to a 2+1-DoF slave manipulator via fluid transmission.
Jointly, a digital master controller provides multimodal control capability beyond common split axis or mode switchable hybrid human-digital controller configurations found in previous studies.
High input impedance, low-leakage, elastomeric fluid actuators are delegated to remote angulation control.
Low-friction graphite piston cylinders are delegated to needle insertion axis remote actuation given the sub-newton force transparency and sub-millimeter motion transmission over bedside fluid piping lengths.

System Requirements

MRI Safe and lesion reachability Force feedback Multimode control The system should be MR safe [ASTM F2503] [ 42 ] by minimizing magnetically induced forces, induced voltages, and minimizing heating on conductive materials. In addition, the robot should not induce image distortion artifacts or significant reduction in the signal-to-noise (SNR) ratio within the region of interest (ROI).

To avoid this, the slave manpulator is free of any local optical or electrical components such as rotary or linear incremental encoders.

System Requirements — A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber — ((a))

Robot Mechanics

The remote needle insertion mechanism consists of a four-bar linkage mechanism with a translating and rotating base link and with the output to coupler joint at a fixed angle. Instead of driving the input link with a prescribed torque input, the mechanism self aligns according to the displacement of the revolute joints as the base link.

The resulting mechanism can be classified as a P-RRR-P mechanism with two prismatic joints and three revolute joint.

Robot Mechanics — A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber — ((b))

MR Scan Robot Characterization

To quantify the signal to noise ratio (SNR) for the MR image feedback we perform a scan for a matrix of robot configurations that include robot near but outside the MR bore as well as inside the bore. The images were acquired using a spin echo sequence (TR/TE = 500/20ms, flip angle=90°, FOV=250mmx250mm, spatial resolution= 0.98mmx0.98mm).

Results a $0.11\%$ difference in SNR between the nominal MR images and those acquired with a bedside robot. Furthermore, while the robot is inside the bore it demonstrates a $0.59\%$ difference in SNR.

MR Scan Robot Characterization — A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber — Fig. 4 : Kinematic diagram of serial-parallel slave needle insertion robot with associated modified-DH table in table III .

Evaluation and Results

Fluid actuators are differentiated by axis. Most low-friction sliding-piston actuators suffer from fluid leakage during loaded retraction due to internal pressure reaching less than 1 atm. Fluid leakage result in force transparency and motion transmission loss due to stiffness loss by air entrapment.

For actuators used in the angulation module of both master and slave, an elastomeric piston cylinder provides the necessary sealing specifications to meet load demands of the mechanism.

Evaluation and Results — A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber — Fig. 6 : a) Needle is inserted into pig about 5-7 cm depth from the skin. b) Needle is slowly advanced forward as it nears the target. Needle reaches target depth and image clearly shows it missed the target’s centroid. c) Needle is retracted slightly and angle is adjusted in-situ to coincide needle tip with target centroid. (d) Needle angle is adjusted to realign with target path. (e) Needle advances and reaches the target centroid.

Human-In-The-Loop Needle Manipulation

The operator proceeds with a 3D MR high resolution preoperative scan to determine the needle entry site. The surgeon investigates the 3-D map to determine an optimal path considering adjacent organs, skin layer density, and local ribs. After the optimal needle-tip path is decided, the surgeon inserts the needle about 2-2.5 cm deep through the skin layer at a fixed angle and guides the needle to the target.

Surgeon manipulates the manual master manipulator to adjust the angle of the needle as it progressively advances toward the target.

Human-In-The-Loop Needle Manipulation — A Master-Salve Robot Manipulator for Needle-Based Teleoperation in MRI Chamber — Fig. 9 : Add-on rapid oscillation at different frequencies. Average peak force and deflection measured by master displacement. (Green) Pre-insertion (Red) Deflection and (Blue) Penetration.

Sources and Demonstrations

Figures are reproduced from Curiel et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.