Currently, the vast majority of magnetic resonance imaging and functional imaging studies are conducted at relatively low magnetic fields of 1.5 or 3.0 Tesla. However, theoretical considerations as well as experimental evidence have suggested that there is a fundamental dependence of image signal to noise ratios, functional imaging contrast and spatial specificity on the magnetic field strength. More recently, it has been suggested that even routine anatomic imaging has potential advantages at high magnetic fields. Thus far, in humans, functional imaging studies have only been done at fields as high as 7 Tesla. Much of the experimental data suggesting advantages for higher field studies have been acquired using animal models. While animal studies provide us with data that can elucidate the biophysics of MRI/fMRI in certain cases, they are not necessarily fully applicable to the human brain. Furthermore, almost all of the studies in humans or animals at high magnetic fields have been done using limited field of views and / or a single or few slices. Shorter T2*s, increased susceptibility effects, increased physiological noise, increased SAR, and inhomogeneous B1 fields can all hinder the advantages offered by high magnetic fields. To alleviate some of the problems associated with these issues and thereby making high field imaging more attractive for general applications of the whole brain, technical development is required. With the recent growth and development of parallel imaging and parallel imaging techniques, including transmit and receive coil arrays, many of these problems commonly observed at high magnetic fields can be addressed. In addition, sequence modification and new sequence design can also help to significantly reduce the technical problems associated with high field studies. The general aim of this proposal is development of fMRI and MRI techniques for whole brain acquisitions at high magnetic fields (7 T &9.4 T). In achieving this aim, fMRI/MRI studies will be conducted at the ultra-high magnetic field of 9.4 Tesla for the first time in humans. Furthermore, we will systematically compare the advantages of higher field systems with lower field systems (3 T) for general applications.
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