Phase-sensitive sodium B1 mapping

Abstract

Quantitative sodium MRI requires accurate knowledge of factors affecting the sodium signal. One important determinant of sodium signal level is the transmit B1 field strength. However, the low signal-to-noise ratio typical of sodium MRI makes accurate B1 mapping in reasonable scan times challenging. A new phase-sensitive B1 mapping technique has recently been shown to work better than the widely used dual-angle method in low-signal-to-noise ratio situations and over a broader range of flip angles. In this work, the phase-sensitive B1 mapping technique is applied to sodium, and its performance compared to the dual-angle method through both simulation and phantom studies. The phase-sensitive method is shown to yield higher quality B1 maps at low signal-to-noise ratio and greater consistency of measurement than the dual-angle method. An in vivo sodium B 1 map of the human breast is also shown, demonstrating the phase-sensitive method's feasibility for human studies. Copyright © 2010 Wiley-Liss, Inc.