A Method to Localize RF B-1 Field in High-Field Magnetic Resonance Imaging Systems

作者：Yoo Hyoungsuk^*; Gopinath Anand; Vaughan J Thomas

来源：IEEE Transactions on Biomedical Engineering, 2012, 59(12): 3365-3371.

DOI：10.1109/TBME.2012.2208965

• Convex optimization
• high-field MRI
• magnetic resonance imaging (MRI)
• pseudoinverse
• parallel excitation
• RF B-1 field
• transmission line head coil

In high-field magnetic resonance imaging (MRI) systems, B-0 fields of 7 and 9.4 T, the RF field shows greater inhomogeneity compared to clinical MRI systems with B-0 fields of 1.5 and 3.0 T. In multichannel RF coils, the magnitude and phase of the input to each coil element can be controlled independently to reduce the nonuniformity of the RF field. The convex optimization technique has been used to obtain the optimum excitation parameters with iterative solutions for homogeneity in a selected region of interest. The pseudoinverse method has also been used to find a solution. The simulation results for 9.4- and 7-T MRI systems are discussed in detail for the head model. Variation of the simulation results in a 9.4-T system with the number of RF coil elements for different positions of the regions of interest in a spherical phantom are also discussed. Experimental results were obtained in a phantom in the 9.4-T system and are compared to the simulation results and the specific absorption rate has been evaluated.

• 出版日期2012-12