OPTICAL MOTION DETECTION FOR MRI

摘要

Motion artefacts are a major hindrance in magnetic resonance (MR) imaging applications. The system as disclosed provides a versatile laser ranging method for the measurement of body part rotation and translation, simultaneously in three dimensions. Since optical motion detection and NMR date acquisition are inherently independent, these two systems can function efficiently in parallel. Furthermore, using these optical motion data, real- time image artefact correction can be achieved by using appropriate paramete rs to change the acquisition in real time. The system uses three laser diodes mounted on a fixed platform and generating converging beams impinging on thr ee retro-reflectors to generate three parallel but offset reflected beams the positions of which are detected by position sensing detectors providing outp ut signals indicative of the position of the beam in the plane of the detector. A mounting assembly for a frame of the reflectors is provided which mounts a frame supporting them on a headphone structure on the patient head. A calculation is provided which locates the position of the frame in the coordinates of the magnet to allow the NMR experiments to compensate for detected movement of the patient's head.