Sunram 5: A Magnetic Resonance-Safe Robotic System for Breast Biopsy, Driven by Pneumatic Stepper Motors

Sunram 5 is the fifth generation MR safe robotic system for breast biopsy. It has five degrees of freedom and is driven by six linear and curved pneumatic stepper motors plus three singular cylinders, all constructed by rapid prototyping techniques. A stepper motor consists of two or three pneumatic cylinders that act on a straight or curved toothed rack. The design, production and evaluation of both single pneumatic cylinders and various types stepper motors are described in detail in this chapter, including design aspects such as the optimal geometries of cylinders, pistons, seals and teeth. Control strategies are also discussed such as how multiple motors inside the Sunram 5 can be controlled to achieve both high speed and high accuracy, despite the relatively low stepping frequencies associated with long pneumatic lines between controller and motor in an MRI setting. This way, Sunram 5 provides fast and precise needle insertions under near-realtime MRI guidance, resulting in improved accuracy and efficiency in MRI-guided breast biopsy procedures.