MRI of human heads appears possible to 9.4T, and whole body imaging shows potential at 7T according to preliminary results from the University of Minnesota. The next benchmark for human imaging will be at 11.747. The Larmor wavelength in muscle and brain tissue dielectrics at 300,400, and 500 MHz are approximately 12cm, 9cm, and 7cm respectively. By conventional methods and thinking, these wavelengths might preclude the possibility of safe and successful human scale imaging. RF interference patterns from a conventional, uniform field volume coil would create severe image inhomogeneities. RF losses to the tissue conductor and the tissue dielectrics to 500 MHz would result in increased heating concerns for conventional pulse protocols. Innovative methods and technology being developed at the University of Minnesota may not only solve some of these problems, but may actually use the short wavelengths to significant new advantages. By controlling the currents in individual RF coil elements, in phase, magnitude, frequency, and time, the RF field can be manipulated to optimize signal from a targeted region of interest for SNR, SAR, CNR, homogeneity, or other criteria. Such ?B1 shimming"""""""" will be automated much like magnetic field BO shimming is today. To develop and employ such methods to achieve the full potential of body imaging at 7T and head imaging at 9.4T are the overall aims of this proposal.
Showing the most recent 10 out of 38 publications
