Patient‐to‐patient variation of susceptibility‐induced B 0 field in bilateral breast MRI

Purpose: To evaluate intersubject variability of susceptibility‐induced static field inhomogeneity in breast and to assess effectiveness of whole‐body high‐order shimming applied to bilateral breast. Materials and Methods: A fast, computationally efficient method to calculate susceptibility‐induced static field from anatomical images was developed. The method was validated against the conventional multiecho B 0 mapping method and was used to generate data for linear and higher‐order shim simulation on 13 volunteers. Results: Most volunteers showed a significant anterior–posterior B 0 gradient. The majority of the subjects also exhibited a statistically significant left–right gradient. The second‐ and third‐order shimming provided only minor (<5% each) improvement in B 0 homogeneity. Conclusion: The shape of the air–tissue boundary determines most of the observed B 0 distribution in bilateral breast. Despite significant variability among subjects, a common feature traceable to generic anatomy exists in the linear gradient. Nonlinear variation of susceptibility‐induced B 0 field occurs over a relatively short length scale and is likely best shimmed by slice‐dependent or localized shimming. J. Magn. Reson. Imaging 2012;36:873–880. © 2012 Wiley Periodicals, Inc.