The applicants proposed to develop tailored Radio Frequency (RF) pulse methods for the mitigation of magnetic susceptibility artifacts in gradient echo (GE) functional MR imaging (Fmri). The project has been motivated by the necessity for fRMI acquisition techniques in brain areas of vital importance for psychiatric and neuroscientific investigations but are, however, currently inaccessible to fMRI due to severe image degradation from magnetic susceptibility artifacts. As part of the research plan, magnetic susceptibility effects in the brain will first be measured and quantified. Susceptibility artifact characterization will include the acquisition of MR images on humans and also the development of theoretical models. From these characterizations, tailored RF pulse techniques will be systematically developed to image these regions. Other susceptibility artifact mitigation techniques, including gradient compensation and data post-processing, will also be implemented and compared to tailored RF pulse methods. This project will lead to valuable new methods capable of imaging brain regions with large magnetic susceptibility variations in an accurate manner free of artifacts. Success in developing the methods described in this application will overcome a major limitation of Fmri, making feasible a broad range of clinical applications not previously possible. Many common disorders, such as schizophrenia, obsessive compulsive disorder, depression, anorexia, and ADHD, which appear to involve disturbances in orbital frontal, striatal, and thalamic regions, will benefit from these techniques. Tailored RF pulse methodology for fMRI represents an undeveloped technology that has the potential for a broad impact both in neuroscientific research and in clinical investigations. Therefore, it is appropriate that this R21 application be reviewed by the National Institute of Mental Health as a response to PA-98-050 "Neuroscience Technology Development."