Improved B 1 homogeneity of 3 tesla breast MRI using dual-source parallel radiofrequency excitation

Abstract

Purpose: To compare breast MRI B1 homogeneity at 3 Tesla (T) with and without dual-source parallel radiofrequency (RF) excitation. Materials and Methods: After institutional review board approval, we evaluated 14 consecutive breast MR examinations performed at 3T that included three-dimensional B 1 maps created separately with conventional single-source and dual-source parallel RF excitation techniques. We measured B 1 values (expressed as % of intended B 1) on each B 1 map at nipple level in multiple bilateral locations: anterior, lateral, central, medial, and posterior. Mean whole breast and location specific B 1 values were calculated and compared between right and left breasts using paired t-test. Results: Mean whole breast B 1 values differed significantly between right and left breasts with standard single- source RF excitation (difference L-R, Δ = 9.2%; P < 0.001) but not with dual-source parallel RF excitation (Δ = 2.3%; P = 0.085). Location specific B 1 values differed significantly between right and left on single-source in the lateral (P = 0.014), central (P = 0.0001), medial (P =0.0013), and posterior (P < 0.0001) locations. Conversely, mean B 1 values differed significantly on dual-source parallel RF excitation for only the anterior (P = 0.030) and lateral (P = 0.0003) locations. Conclusion: B 1 homogeneity is improved with dualsource parallel RF excitation on 3T breast MRI when compared with standard single-source RF excitation technique. © 2012 Wiley Periodicals, Inc.