Towards Robot-Assisted MRI-Guided Lumbar Injections

Lumbar epidural injection requires precise needle placement to ensure efficient drug delivery into the epidural space. MRI-compatible robotic systems offer unique advantages for this procedure by combining the advantages of intraoperative MRI guidance with the precision and dexterity of robotic assistance. This paper presents a 4-degree-of-freedom (DOF) MRI-compatible robotic system designed to assist surgeons in performing lumbar injections with improved accuracy and consistency. The proposed system features a modular architecture comprising an actuation unit, a two-layer linkage mechanism, and a needle placer. The kinematics of the system were derived, and a control framework incorporating backlash compensation was implemented. A workspace analysis was conducted, with the effective workspace found to be ±72.9 mm (medial-lateral) and ±32.5 mm (superior-inferior), and a tilting range exceeding 25°. As a proof of concept, the prototype was experimentally evaluated to validate its mechanical performance. The results demonstrated sub-millimeter precision with an average deviation from a mean location of 0.33 mm, confirming the feasibility of accurate and repeatable needle guidance, and marking a step toward clinical translation of robot-assisted MRI-guided lumbar injection procedures.