Uchechukwuka Diana Monu1, Pauline W.
Worters2, Kyunghyun Sung2, Kevin M. Koch3,
Garry
1Electrical Engineering,
Stanford University, Stanford, CA, United States; 2Department of
Radiology, Stanford University, Stanford, CA, United States; 3Applied
Science Lab, GE Healthcare, Waukesha, WI, United States
In MRI, the measurement of RF excitation fields is challenging. Furthermore, B0 inhomogeneities make B1 mapping near metallic implants especially difficult. Currently available B1 mapping methods that are based on gradient echo and spin echo techniques have not been successfully used around metallic implants. This is mostly due to signal loss from increased susceptibility and imaging artifacts near metal. In this work, B1 maps of phantoms were obtained using the standard gradient echo double angle method (DAM) and using the SEMAC DAM on a 1.5T whole-body MR scanner. A good comparison of these maps and matlab simulations carried out to model the error values of the SEMAC DAM, allowed for the SEMAC DAM to be subsequently applied to a metallic implant phantom at both 1.5T and 3T. The flip angle maps obtained show that the proposed technique is a valid approach for tackling the issue of B1 mapping near metallic implants.
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