Abstract: Current MRI technologies require subjects to remain largely motionless for achieving high quality magnetic resonance (MR) scans, typically for 5-10 minutes at a time. However, lying absolutely still inside the tight MR imager (MRI) tunnel is a difficult task, especially for children, very sick patients, or the mentally ill. Even motion ranging less than 1 mm or 1 degree can corrupt a scan. This invention involves a system that adaptively compensates for subject motion in real-time. An object orientation marker, preferably a retro-grate reflector (RGR), is placed on a patients' head or other body organ of interest during MRI. The RGR makes it possible to measure the six degrees of freedom (x, y, and z-translations, and pitch, yaw, and roll), or “pose”, required to track the organ of interest. A camera-based tracking system observes the marker and continuously extracts its pose.