A simple B 1 correction method for dynamic contrast-enhanced MRI

The double-angle method (DAM) is commonly used as a reference standard in radiofrequency field (B1) mapping studies. This study explored two aspects of DAM: (i) use of small flip angle pairs to reduce the repetition time (TR) needed for adequate longitudinal relaxation (T1); and (ii) the effect of using different flip angle ratios for B1 mapping. Results of phantom studies show that B1 correction using small flip angle pairs ≤ 60° with TR = 5000 ms can allow for accurate estimation of T1 up to about 1500 ms; and that increasing the ratio of the two flip angles used for B1 correction resulted in more accurate estimation of T1. These modifications allow 3-dimensional (3D) B1 mapping to be consistently performed with the same 3D spoiled gradient echo sequence used for T1 mapping in dynamic contrast-enhanced MRI.