A Study of the Relationship Between B1-Field Uniformity, Body Aspect Ratio and SAR for Whole-Body RF Shimming at 3.0T

Zhiyong Zhai¹, Michael Morich¹, Gordon DeMeester¹, Paul R. Harvey²

In a 3T whole body MRI system, the body tissue dielectric effects become important. It can considerably decrease B1-field homogeneity and affect image quality. Experiments show that B1-field non-uniformity varies with a scanning subjects loading position and body shape. To study the optimal B1 shimming methods for various subjects with different body shapes, while keeping SAR within RF safety limits, the FDTD method is used to evaluate the relationship between the optimized |B1+|-field, the whole-body SAR and the maximum local SAR for human body models with different aspect ratios. Results are compared to the conventional quadrature driven case.