Simultaneous B 0 ‐ and B 1 +‐Map acquisition for fast localized shim, frequency, and RF power determination in the heart at 3 T

High‐field (≥3 T) cardiac MRI is challenged by inhomogeneities of both the static magnetic field ( B 0 ) and the transmit radiofrequency field ( B 1 +). The inhomogeneous B fields not only demand improved shimming methods but also impede the correct determination of the zero‐order terms, i.e., the local resonance frequency f 0 and the radiofrequency power to generate the intended local B 1 + field. In this work, dual echo time B 0 ‐map and dual flip angle B 1 +‐map acquisition methods are combined to acquire multislice B 0 ‐ and B 1 +‐maps simultaneously covering the entire heart in a single breath hold of 18 heartbeats. A previously proposed excitation pulse shape dependent slice profile correction is tested and applied to reduce systematic errors of the multislice B 1 +‐map. Localized higher‐order shim correction values including the zero‐order terms for frequency f 0 and radiofrequency power can be determined based on the acquired B 0 ‐ and B 1 +‐maps. This method has been tested in 7 healthy adult human subjects at 3 T and improved the B 0 field homogeneity (standard deviation) from 60 Hz to 35 Hz and the average B 1 + field from 77% to 100% of the desired B 1 + field when compared to more commonly used preparation methods. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.