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

PRLog (Press Release) – May 25, 2011 – 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.

A perfect picture with plastics
Since the robot operates inside a 3-Tesla, closed-bore MRI machine with only a 500-millimeter cylinder diameter, there were a number of elements that had to be taken into consideration during the design process.

Just In Hevi-Rail®: Linear Bearing of all Trades in Heavy ...

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today ! Design Versatility: Hevi-Rail® combined bearings allow for several unique design applications and handling tasks within the industrial market. Jib cranes, lift units and warehouse handling systems make up a small percentage of the many different ways Hevi-Rail bearings are applied to improve factory performance and operation by streamlining assembly and eliminating machine shut downs. Material Handling: Other linear guide products rely on precise parallel alignment to reliably handle linear motion tasks; such as material handling, lifting and adjustment. This requires the installer to conduct a thorough and painstaking checking and re-checking of the monorails to ensure maximum parallelism. Apart from the time spent checking parallelism and realigning, this is also a very costly process. The linear guides also need to be preloaded beforehand for assured system rigidity; however, when dealing with large loads, the preload causes fretting and catastrophic failure in ball-type linear guides and complete stalling in plain bearing products due to exceeding moment load. With Hevi-Rail®, the unique combined bearing design allows the bearings to float within the rail, thereby eliminating the need for precise alignment and effectively reducing installation time. Telescopic Applications: For high load telescopic handling, Hevi-Rail can support cantilevered loads up to 700 lbs. (318 Kg) extending out 90’’ (2.3 meters). Recently, PBC Linear collaborated with a customer to design a new racking system for shipping containers. Previously, the containers were simply filled and shipped, leaving the materials loose inside and able to shift around in transit. PBC worked with the design team to create a racking system that could be extended/retracted for easy loading and unloading using Hevi-Rail combined bearings to handle the extended load and operate under extremely low maintenance.

Tenth International Conference on Adaptive Structures and Technologies, October 11-13, 1999, Paris, France

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