Prostate Targeting: Compact Robot With Harmonic Stepper Motors for MRI-Guided Needle Therapy

The superior image quality and excellent contrast offered by Magnetic Resonance Imaging (MRI) make it an ideal tool for guiding interventional procedures, particularly in targeting tumors within soft tissues. This paper presents an innovative robotic system, tailored for Magnetic Resonance (MR) environments, leveraging the benefits of MRI's high-resolution imaging capabilities for precise tumor targeting. The robot, designed with four degrees of freedom (DOFs), is driven by four novel Harmonic Pneumatic Motors, ensuring Magnetic Resonance (MR) compatibility. This motor utilizes a harmonic gearbox mechanism, incorporating a pair of flex and circular splines, with torque generated through the deformation of the flex spline. It achieves a step size of 0.9° and delivers a maximum measured output torque of 825 mN·m. The robot's design includes a dual-stage needle guide, each stage is supported by two arms, enhancing its targeting accuracy. Experimental tests have demonstrated the robot's high positioning accuracy of 1.56 mm. Furthermore, MR testing confirms that the robot's presence results in a negligible signal-to-noise ratio (SNR) reduction, well within acceptable limits. The introduction of the Harmonic Pneumatic Motor-Driven Robot presents an improvement of compact MRI robots in the field, providing a potent combination of precision, safety, and compatibility in MRI-guided interventional procedures.