Actuation methods for applications in MR environments

The choice of an adequate actuation method is a central issue in the development of any mechatronic device and strongly determines the dynamic performances of the system. This choice is particularly difficult for robotic systems working within a magnetic resonance (MR) environment because of the safety and compatibility constraints imposed by the high magnetic field, switching gradients, electromagnetic pulses, and sensitive measuring equipment involved. This article analyzes actuation methods for robotic systems to be used within a magnetic resonance environment, such as systems for diagnostic and interventional MR[, neuroscience studies during functional MRI, and diagnostic fMRI. In the case of functional MRI, actuation is also required during imaging, whereas current MR-compatible interventional systems are typically moved between imaging phases. our analysis is based on a variety of actuation principles that we have tested both for MR compatibility and for the quality of force feedback that can be realized, including hydrostatic, belt, and cable transmissions as well as electrostatic and piezoelectric actuators. The results are completed with developments of other groups. A good solution to a given application often involves a combination of several actuation principles. A synthesis of characteristics and three comparative tables aid in the choice of an adequate actuation method for a given task or application. (C) 2006 Wiley Periodicals, Inc.