Targeted radiofrequency field mapping using 3D reduced field-of-view-catalyzed double-angle method

Purpose: The aim of this study was to develop a targeted volumetric radiofrequency field (B ₁ ⁺) mapping technique to provide region-of-interest B ₁ ⁺ information. Materials and Methods: Targeted B ₁ ⁺ maps were acquired using three-dimensional (3D) reduced field-of-view (FOV) inner-volume turbo spin echo-catalyzed double-angle method (DAM). Targeted B ₁ ⁺ maps were compared with full-FOV B ₁ ⁺ maps acquired using 3D catalyzed DAM in a phantom and in the brain of a healthy volunteer. In addition, targeted volumetric abdomeninal B ₁ ⁺ mapping was demonstrated in the abdomen of another healthy volunteer. Results: The targeted reduced-FOV images demonstrated no aliasing artifacts in all experiments. Close match between targeted B ₁ ⁺ map and reference full-FOV B ₁ ⁺ map in the same region was observed, with percentage root-mean-squared error <0.4% in the phantom and <0.8% in the healthy volunteer brain. The abdominal B ₁ ⁺ maps showed small B ₁ ⁺ variation in the kidneys and liver from the healthy volunteer. Conclusion: The proposed 3D reduced-FOV catalyzed DAM provides a rapid, simple and accurate method for targeted volumetric B ₁ ⁺ mapping and can be easily implemented for applications related to radiofrequency field mapping in small targeted regions.