Breast MR imaging at 3 t with dual-source radiofrequency transmission offers superior b1 homogeneity: An intraindividual comparison with breast mr imaging at 1.5 T1

摘要

Purpose: To evaluate and compare B1 homogeneity for breast magnetic resonance (MR) imaging performed at 3 T with dualsource radiofrequency (RF) transmission to 1.5-T MR imaging and 3-T MR imaging with quadrature transmission. Materials and Methods: This prospective study received institutional review board approval and patients provided informed consent. Women (n = 25; mean age, 53 years; range, 30-68 years) suspected of having breast lesions underwent breast MR imaging examinations on comparable 1.5-T and 3-T clinical systems between February and May 2012. B1 maps were obtained at 1.5 T and at 3 T with quadrature and dualsource RF transmission. Intrabreast differences and differences in mean B1 values between right and left breasts were investigated by using two-sided multivariate analysis of variance with interaction; t tests were used to compare the differences between measured whole-breast mean B1 values and requested B1 values. Results: With quadrature transmission at 1.5 T and 3 T, the mean B1 values showed a statistically significant difference: leftbreast measured B1 was 28.9% of requested B1 value at 1.5 T and 213.7% at 3 T (P < .001), whereas right-breast measured B1 was +5.4% of requested B1 value at 1.5 T (P < .001) and +2.7% at 3 T (P = .01). With dual-source RF transmission at 3 T, mean B1 values across the breasts were not statistically different, nor were the measured B1 values compared with requested B1 values (left breast, 20.6%; right breast, 20.7%). At 3 T with dual-source transmission, slight intrabreast local variations in B1 were recorded. Conclusion: MR imaging at 3 T with dual-source RF transmission offered an overall B1 homogeneity for breast imaging that was better than that obtained at 1.5 T and with quadrature transmission.