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