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 decade, 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. DSU 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. Following a successful completion of the Phase I STTR grant, the current Phase II application continues the work towards commercialization of DSU. Specifically, DSU hardware will be further improved and combined with professional software to automatically set up the unit. Since DSU is significantly more complicated than regular shimming, additional software will be provided for the every day operation of the unit by standard MR users. Since MFI affects almost all facets of in vivo NMR, the successful commercialization of DSU will have major impacts on the clinical application of MRI and MRS and can thus be labeled as highly significant.
Magnetic resonance imaging (MRI) and spectroscopy (MRS) are the leading techniques to obtain high-quality images and metabolic profiles of intact human tissues in health and disease. Unfortunately, spatial variations in magnetic field strength introduced by the sample can severely degrade the quality of MRI and MRS data, such that distinction of normal from diseased tissues may be compromised. Current technology is not able to completely cancel the spatial magnetic field variations. The current project focuses on the development of novel technology that can significantly reduce spatial magnetic field variations, thus leading to greatly increased MRI and MRS data quality.
|Boer, Vincent O; Klomp, Dennis W J; Juchem, Christoph et al. (2012) Multislice Â¹H MRSI of the human brain at 7 T using dynamic Bâ‚€ and Bâ‚ shimming. Magn Reson Med 68:662-70|