Improved B1 homogeneity of 3 Tesla breast MRI using dual-source parallel radiofrequency excitation

Purpose: To compare breast MRI B(1) 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 dual-source parallel RF excitation on 3T breast MRI when compared with standard single-source RF excitation technique.