Surgical mechatronics systems in a MRI environment promise a popular strategy for minimize invasive treatment. We developed an image guided MRI compatible manipulator with ultrasound motors used inside the MRI gantry. MRI compatibility is important in the development of a manipulator, since the effects of magnetic materials and the influence of electromagnetic wave leakage on MRI images should be considered. We evaluated the effect of electromagnetic waves on MR images and clarified the RF immunity level of the image. We also describe an electromagnetic wave shield required for MRI compatibility. We measured the leakage of electromagnetic waves as a novel way of evaluating MRI compatibility based on the results of our findings of RF immunity on images. We also quantified the MR compatibility of the manipulator based on MR images and electromagnetic wave measurements. The decrease in the signal-to-noise ratio (SNR) and distortion, caused by the manipulator inside a 0.2 T MRI gantry, and electromagnetic wave leakage to the actuator were evaluated. The results showed that MR images were only distorted for less than 2 pixels, and that the SNR decreased by 0.6%. Electromagnetic wave leakage at a resonance frequency band of 0.2 T MRI was undetectable. Therefore, the manipulator has high MRI compatibility and could be driven while acquiring MR images. This evaluation method is effective for developing novel MRI compatible mechatronics systems for use during the acquisition of MR images.
