Fully Compensated Dynamic Shim System for In Vivo MRI and MRS

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DESCRIPTION (provided by applicant): Functional MRI, diffusion MRI and MR spectroscopy and spectroscopic imaging have great potential for the study and diagnosis of disease and injury, and guiding surgical therapy. All of these methods benefit greatly from the added sensitivity, resolution and contrast from high field strength magnets (3T and above). However, the advantages of higher magnetic fields have not been fully realized due to the increasingly confounding effects of magnetic field inhomogeneity (MFI) caused by magnetic susceptibility differences between air and tissue. MFI leads to signal loss and spatial distortion in MRI and loss in spectral resolution and sensitivity in MRS. The loss of reliability due to these artifacts is a major reason why these techniques have not seen wide use in clinical applications. Current methods of magnetic field homogenization (i.e. shimming) work well on small volumes but are inadequate over larger objects, like the entire human brain. Over the last five years, the MR group at Yale University has developed the technique of dynamic shim updating (DSU) which allows greatly improved magnetic field homogeneity over extended regions. Dynamic shim updating divides a global 3D problem into a number of slices over which adequate magnetic field homogeneity can be achieved. Dynamically updating the pre-determined slice shims in sync with the multi-slice MRI sequence ensures optimal homogeneity for all slices. Given the maturity of the technique, as well as the increasing demand for improved magnetic field homogeneity, it is the goal of this Phase I STTR proposal to develop DSU into a commercially viable method. As all of the previous developments were performed on Yale-specific equipment, the first step towards commercialization is the development, construction and testing of a stand-alone DSU unit. Once the feasibility of the stand- alone DSU unit has been established, the road towards commercialization will be traveled in a future Phase II STTR application. Since MFI affects many facets of in vivo NMR, the successful implementation of DSU will have major impacts on almost all aspects of MRI and MRS and can thus be labeled as highly significant.