Sunram 5: the new MR safe robotic system for breast biopsy

"During the Surgical Robot Challenge at the international Hamlyn Symposium in London, Univeristy of Twente researchers revealed the latest version of the Sunram series. The robot, named Sunram 5, is more accurate and faster, which means biopsy can be performed in an even better way.The Sunram 5 is driven by air-pressure-powered cylinders. Thanks to the use of hoses to supply the air, the controls of the robot can be placed outside of the MRI scanner. The design of the robot has been fully adapted to the current MRI setting. For instance, the robot is compact, which means it can be attached to the current breast compression system in various orientations. That way, the robot can easily reach any area in the breast. Another new feature are the so-called dual-speed motors, which allow for both faster and more accurate movements. This means accuracy has improved to 0.1mm, and the robot can move from start to its target location in about 10 seconds. Moreover, a safety mechanism has been designed which retracts the needle from the breast when the controller measures a mains voltage or air pressure failure.

The development of Sunram 5 is in the hands of: Vincent Groenhuis MSc, Dr. Françoise J. Siepel, Marcel K. Welleweerd MSc, and Prof.dr.ir. Stefano Stramigioli of the Robotics and Mechatronics (RAM) lab at the University of Twente. Moreover, there was close cooperation with Dr. Jeroen Veltman, radiologist at the Ziekenhuis Groep Twente (ZGT), in order to adapt the design to clinical practice as much as possible. Abe van der Werf of Machnet B.V. was involved for the breast fixation system."

"The five degree of freedom manipulator is actuated by six pneumatic stepper motors, measures 107 x 72 x 56 mm and has a mass of 260 g. Two of the motors have a relatively large step size of 1.7 mm, allowing for high-speed lateral and needle insertion movements. These motors are coupled with small-step motors (step size 0.3 mm) to maintain sub-millimeter accuracy in the same direction. Each stepper motor consists of two or three pneumatic cylinders which alternatingly press against a straight or curved rack to make discrete steps[2]. Besides these six stepper motors three individual cylinders are also present to fire the biopsy gun and activate the needle ejection safety mechanism."

Source: University of Twente, Hamlyn Symposium Proc.