ADAPTIVE TECHNIQUES FOR MR IMAGING OF MOVING STRUCTURES

We propose to further develop adaptive correction methods for MR imaging in the presence of motion, as demonstrated in the previous grant cycle. These correction techniques can in theory provide a complete correction for the effects of object motion in many applications, unattainable by conventional artifact reduction methods. Our work to date has shown, however, that practical implementation requires attention to nonidealities such as spatially-dependent phase shifts due to off-resonance phenomena and to other critical application-specific issues. Work will be done in four projects: (1) Resolution-Critical MRI. Practical adaptive motion correction techniques will be developed for technically- demanding, high resolution applications for MRI where small fields of view are needed. (2) General Global Motion Correction. We will develop and implement a generalized method for multi-axis motion correction, using real time processing of azimuthal (nonlinear projection) navigator echoes and intra-acquisition modification of scan parameters to dynamically displace and reorient the imaging frame of reference. (3) Thoracoadominal MRI. Development will be continued on retrospective and real-time adaptive motion correction techniques to provide improved image quality in high resolution abdominal MR imaging by addressing the effects of respiratory motion. (4) High Resolution MR Angiography. We will apply adaptive motion correction techniques to technically challenging applications of MR angiography. Specifically, we propose to integrate real-time navigator-echo based respiratory motion correction techniques with coronary artery MR angiography sequences. The common objective of these projects is to lock the frame of reference of the image acquisition process to the clinical region of interest, and to strip away motion-related effects that continue to limit the potential applications of MRI. We anticipate that these developments will reduce the need for sedation or anesthesia, improve the reliability, and increase the effective spatial resolution of a variety of clinical MRI examinations.