B1 transmission-field inhomogeneity and enhancement ratio errors in dynamic contrast-enhanced MRI (DCE-MRI) of the breast at 3T

• Published in: Journal of magnetic resonance imaging Vol. 31; no. 1; pp. 234 - 239
• Main Authors: Azlan, Che A., Di Giovanni, Pierluigi, Ahearn, Trevor S., Semple, Scott I.K., Gilbert, Fiona J., Redpath, Thomas W.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.01.2010; Wiley Subscription Services, Inc
• Subjects: Adult; Algorithms; B1-field inhomogeneity; Breast - anatomy & histology; breast tumor; Contrast Media; dynamic contrast-enhanced MRI; Female; high-field MRI; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Imaging, Three-Dimensional - methods; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 1053-1807; 1522-2586
• DOI: 10.1002/jmri.22018

Purpose: To quantify B1 transmission‐field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T1‐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. Materials and Methods: A total of 25 volunteers underwent breast imaging at 3T and the B1 transmission‐fields were mapped. Gel phantoms that simulate pre‐ and postcontrast breast tissue T1 were developed. The effects of B1‐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 B1 transmission‐field field is always reduced toward the volunteer's right side. The median B1‐field in the right breast is reduced around 40% of the expected B1‐field. For some volunteers the amplitude was reduced by more than 50%. Computer simulation and experiment showed that a reduction in B1‐field decreases ER. This reduction increases with both B1‐field error and contrast agent uptake. Conclusion: B1 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. J. Magn. Reson. Imaging 2010;31:234–239. © 2009 Wiley‐Liss, Inc.