title: B1 transmission-field inhomogeneity and enhancement ratio errors in dynamic contrast-enhanced MRI (DCE-MRI) of the breast at 3T.
abstract: OBJECTIVE
  To quantify B(1) transmission-field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T(1)-weighted spoiled gradient echo and to assess the resulting errors in enhancement ratio (ER) measured in dynamic contrast-enhanced MRI (DCE-MRI) studies of the breast.
  
  
  METHODS
  A total of 25 volunteers underwent breast imaging at 3T and the B(1) transmission-fields were mapped. Gel phantoms that simulate pre- and postcontrast breast tissue T(1) were developed. The effects of B(1)-field inhomogeneity on ER, as measured using a 3D spoiled gradient echo sequence, were investigated by computer simulation and experiments on gel phantoms.
  
  
  RESULTS
  It was observed that by using the patient orientation and MR scanner employed in this study, the B(1) transmission-field field is always reduced toward the volunteer's right side. The median B(1)-field in the right breast is reduced around 40% of the expected B(1)-field. For some volunteers the amplitude was reduced by more than 50%. Computer simulation and experiment showed that a reduction in B(1)-field decreases ER. This reduction increases with both B(1)-field error and contrast agent uptake.
  
  
  CONCLUSIONS
  B(1) transmission-field inhomogeneity is a critical issue in breast imaging at 3T and causes errors in quantifying ER. These errors would be sufficient to reduce the conspicuity of a malignant lesion and could result in reduced sensitivity for cancer detection.
authors.affiliation: Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Scotland, UK. azlan.ahmad@abdn.ac.uk
authors.forename: Che A
authors.initials: CA
authors.lastname: Azlan
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Di Giovanni
authors.forename: Trevor S
authors.initials: TS
authors.lastname: Ahearn
authors.forename: Scott I K
authors.initials: SI
authors.lastname: Semple
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Gilbert
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Redpath
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001940:Breast / Q000033:anatomy & histology*; D003287:Contrast Media; 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
chemical_list: D003287:Contrast Media