Transmit Efficiency Across a Range of Field Strengths, Relative Permittivities and Transmit Coils

Transmit efficiency is an important parameter in MRI to determine the quality of a coil, and it is affected by many parameters such as the frequency and the shape of the patient. The presence of a High-Permittivity Helmet significantly impacts the radiofrequency fields distribution. Through numerical simulations we have evaluated the dependence of the transmit efficiency with respect to the variation of many parameters, such as the frequency, the permittivity of the helmet, and the kind of used coil: the performances of a birdcage and of an 8 dipoles transmit array are compared.