Development of Dual-Polarity GRAPPA for Echo Planar Imaging Methods

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The diagnosis and treatment of neuropsychiatric disorders critically depends on characterizing neurological function and the ow of blood in the brain. Functional MRI using the EPI sequence is the current imaging standard for investigating brain function. At ultrahigh eld strength, 7 Tesla, the study of brain function and perfusion is limited by imaging artifacts that are inherent in the EPI data acquisition process. One dominant artifact is EPI ghosting which manifests as copies of the measured signal displaced from the original source location. In certain cases, these displaced copies can appear as ripple artifacts that may change over course of an imaging session, introducing temporal instability into the data. These artifacts appear more prominently at higher magnetic eld strength, particularly when imaging structures deep within the brain. We recently presented a new method, Dual-Polarity GRAPPA (DPG), that ef ciently models and corrects the data sampling inconsistencies that cause ghost and ripple artifacts. This proposal seeks to apply this new method to clinical applications where these artifacts appear, including functional, perfusion, and diffusion studies. In Aim 1, we will apply the new DPG method to clinical protocols for functional, perfusion, and diffusion studies on 3 Tesla scanners, and characterize the signal loss, temporal stability, motion sensitivity, and artifact levels compared to conventional methods. In addition, we will incorporate the DPG method into a new EPI acquisition mechanism that acquires multiple image slices simultaneously. In Aim 2, we well apply these techniques to advanced research diffusion and functional protocols for 7 Tesla scanners, and test the methods' ability to restore signal data that is lost using current image acquisition methods. The success of our proposal will be identi ed by the ability to characterize an improvement in temporal stability in functional, diffusion, and perfusion imaging applications. The successful completion of this project will directly improve imaging studies at both 3T and 7T eld strength, by improving sensitivity in methods that image the inferior frontal cortex and temporal lobes.