Patient-to-patient variation of susceptibility-induced B₀ field in bilateral breast MRI.
OBJECTIVE
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.


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.


CONCLUSIONS
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.
GE Global Research, Niskayuna, New York, USA. lsk@ge.com
Seung-Kyun
SK
Lee
Ileana
I
Hancu
D000328:Adult; D000465:Algorithms; D001940:Breast / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult