Practical Methods for ImprovingB+1Homogeneity in 3 Tesla Breast Imaging

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To improve image contrast and Symbol field homogeneity in 3 Tesla (T) breast MR.

Materials and Methods:

Two practical Symbol shimming methods for 3T breast MR are presented; low-cost passive shimming using local pads of high dielectric permittivity (εr from 0 to 100), and two-channel radiofrequency (RF) shimming (adjusting Q-I amplitude ratios and phase differences of 0 to −4 dB and 90 to 45 degrees), as well as a combination of both methods. The technique has been studied both in simulation using a numerical body model with added mammary tissue and in vivo in six subjects.


Large improvements are observed with both methods, leading to a decrease in left–right Symbol asymmetry ratio of 1.24 to 1.00 (simulation) and from 1.26 to 1.01 (in vivo). RF safety was not adversely affected.


Both RF shimming and dielectric shimming were shown to improve inhomogeneity in the Symbol field in 3T breast MR.

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