Linear Guides and Plastic Bearings Facilitate Motion for MRI-guided Robot

A team of researchers from the Worcester Polytechnic Institute have developed a teleoperated robot that will greatly improve the way prostate cancer is detected and treated. igus® donated parts to the project at no cost, including DryLin® linear guide systems and iglide® plastic plain bearings, which facilitate the robot’s motion.

Prostate cancer is the second most common cancer in North America and the leading type of cancer found in males. Each year approximately 1.5 million core-needle biopsies are performed, leading to a staggering 220,000 newly diagnosed cases of prostate cancer. The robotic system is specifically for prostate percutaneous procedures taking place under magnetic resonance imaging (MRI) guidance. The slave robot features a high-resolution fiber optic sensor for prostate interventions with real-time in situ needle steering capability in 3-Tesla MRI.

The robot’s needle placement robot consists of a 3-DOF Cartesian positioning module and 3-DOF needle driver module. DryLin T linear guides facilitate translational motion of the positioning module, which provides gross positioning for the robot’s needle driver. The needle driver is a vital part of the system, as it enables the rotation and translational movement of the needle cannula: a flexible tube inserted into the patient’s body cavity for MRI-guided diagnosis and therapy.

The needle driver has a needle guide sleeve, a collet locking mechanism and passive optical tracking fiducial frame. Two iglide A200 plastic plain bearings are used in the front and rear of the driver to constrain the needle guide. The iglide bearings enable the robot’s motor to rotate the needle using the collet mechanism by way of a timing belt. This rotating needle would reduce tissue damage while enhance targeting accuracy. Another 10 iglide bearings were used to create a revolute joint, also known as a “pin joint” or “hinge joint”, to provide single-axis rotation.

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