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 (B 1 ) 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 (T 1 ); and (ii) the effect of using different flip angle ratios for B 1 mapping. Results of phantom studies show that B 1 correction using small flip angle pairs ≤ 60° with TR  =  5000 ms can allow for accurate estimation of T 1 up to about 1500 ms; and that increasing the ratio of the two flip angles used for B 1 correction resulted in more accurate estimation of T 1 . These modifications allow 3-dimensional (3D) B 1 mapping to be consistently performed with the same 3D spoiled gradient echo sequence used for T 1 mapping in dynamic contrast-enhanced MRI.