Saturated double‐angle method for rapid B1+ mapping

Abstract

For in vivo magnetic resonance imaging at high field (≥3 T) it is essential to consider the homogeneity of the active B₁ field (B₁+), particularly if surface coils are used for RF transmission. A new method is presented for highly rapid B₁+ magnitude mapping. It combines the double angle method with a B₁‐insensitive magnetization‐reset sequence such that the choice of repetition time (TR) is independent of T₁ and with a multislice segmented (spiral) acquisition to achieve volumetric coverage with adequate spatial resolution in a few seconds. Phantom experiments confirmed the accuracy of this technique even when TR ≪ T₁, with the side effect being lowered SNR. The speed of this method enabled B₁+ mapping in the chest and abdomen within a single breath‐hold. In human cardiac imaging, the method enabled whole‐heart coverage within a single 16‐s breath‐hold. Results from phantoms and healthy volunteers at 1.5 T and 3 T are presented. Magn Reson Med, 2006.