PURPOSE: To improve image contrast and B1+ field homogeneity in 3 Tesla (T) breast MR. MATERIALS AND METHODS: Two practical B1+ 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 B1+ 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 B1+ field in 3T breast MR.
PURPOSE: To improve image contrast and B1+ field homogeneity in 3 Tesla (T) breast MR. MATERIALS AND METHODS: Two practical B1+ 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 B1+ 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 B1+ field in 3T breast MR.
Authors: Qing X Yang; Jinghua Wang; Xiaoliang Zhang; Christopher M Collins; Michael B Smith; Haiying Liu; Xiao-Hong Zhu; J Thomas Vaughan; Kamil Ugurbil; Wei Chen Journal: Magn Reson Med Date: 2002-05 Impact factor: 4.668
Authors: Mariya Lazebnik; Dijana Popovic; Leah McCartney; Cynthia B Watkins; Mary J Lindstrom; Josephine Harter; Sarah Sewall; Travis Ogilvie; Anthony Magliocco; Tara M Breslin; Walley Temple; Daphne Mew; John H Booske; Michal Okoniewski; Susan C Hagness Journal: Phys Med Biol Date: 2007-10-01 Impact factor: 3.609