MOTIVATION - Motion remains one of the most frequent contributors to image artifacts in MR studies. The motion susceptibility of MRI is well-known and has spawned a number of elegant navigation techniques. These methods, however, are tailored to specific MR acquisitions that require modified k-space trajectories or the acquisition of additional MR data, and most are unable to correct certain types of motion, for example, through-plane motion. Certain patient populations, such as pediatric or geriatric patients, are more likely to move than others. In pediatric imaging, anesthesia is used to control motion, adding substantially to exam costs and patient risks. A sequence-independent, autonomous and prospective motion correction system could greatly improve image quality for a wide spectrum of MR examinations. For pediatric imaging, in particular, we anticipate reduced reliance on anesthesia to control patient motion.
AIMS - This project aims to explore the potential to use an alternative MRI motion compensation approach, using continuous optical monitoring of patient position and updating of the MR scanner's 3D coordinate system in quasi real-time. Acquisition thus follows the movement of the patients head, providing MR scans virtually free from motion artifacts and without spin history artifacts. This approach will require the development and calibration of an MR compatible optical position capture system (Aim 1), which can be used to continually update the scanner's reference coordinate system (Aim 2). Finally, testing the new system on volunteers is necessary to assess the improvements in image quality over conventional scanning or navigator- based methods (Aim 3). METHODS - An MR-compatible optical position tracking device will be developed and mounted to common head coils. This device will lock the MR system's frame of reference to that defined by the position of the patient's head. Therefore, when patient motion occurs, the MR system will update its RF excitation, gradients, and data reception to keep pace with this motion. Over 2 years, healthy children (n=38) and adults (n=22) will be enrolled to compare conventional MR and motion-compensated MR while subjects perform movements at four predefined levels of severity. SIGNIFICANCE - The success of this project will significantly improve MR exams conducted in the presence of motion and will therefore benefit most patient populations. However, we expect that in pediatric and geriatric patients the advantages from using motion-compensated MR will be greatest. A positive outcome of this research effort will also affect patients indirectly by reducing the overall scan time or improving diagnostic capacity of the images. We are confident to show in future studies that, by using our approach, the dependence upon anesthesia in pediatric scanning can be significantly reduced. MR imaging continues to develop new approaches to minimize or eliminate motion errors that decrease image quality and increase patient exam time. This project develops a unique approach based on an optical motion detecting system that will be mounted on an MRI head coil. The optical system will track head position; correct for motion throughout image acquisition time; result in improved diagnostic image quality; and reduce, or even eliminate, the need for repeat studies due to patient head motion. ? ? ?
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