  MR-guided microwave ablation (MWA) has proven effective in treating
hepatocellular carcinoma (HCC) with small-sized tumors, but the
state-of-the-art technique suffers from sub-optimal workflow due to speed and
accuracy of needle placement. This paper presents a compact body-mounted
MR-conditional robot that can operate in closed-bore MR scanners for accurate
needle guidance. The robotic platform consists of two stacked Cartesian XY
stages, each with two degrees of freedom, that facilitate needle guidance. The
robot is actuated using 3D-printed pneumatic turbines with MR-conditional bevel
gear transmission systems. Pneumatic valves and control mechatronics are
located inside the MRI control room and are connected to the robot with
pneumatic transmission lines and optical fibers. Free space experiments
indicated robot-assisted needle insertion error of 2.6$\pm$1.3 mm at an
insertion depth of 80 mm. The MR-guided phantom studies were conducted to
verify the MR-conditionality and targeting performance of the robot. Future
work will focus on the system optimization and validations in animal trials.
