Abstract: An optical image-based tracking system determines the position and orientation of objects such as biological materials or medical devices within or on the surface of a human body undergoing Magnetic Resonance Imaging (MRI). Three-dimensional coordinates of the object to be tracked are obtained initially using a plurality of MR-compatible cameras. A calibration procedure converts the motion information obtained with the optical tracking system coordinates into coordinates of an MR system. A motion information file is acquired for each MRI scan, and each file is then converted into coordinates of the MRI system using a registration transformation. Each converted motion information file can be used to realign, correct, or otherwise augment its corresponding single MR image or a time series of such MR images.