Figure 4: a) Sagittal slice of the 27 3D B₁⁺ predictions using the default shim setting (left) and the 4kT-UP (right). Library: B₁⁺ maps 1-22, test-cases: B₁⁺ maps 23-27. The 4kT-UP results in a homogeneous FA in the heart ROI of all 5 test cases. Moreover, the 4kT-UP achieves a homogeneous FA also in surrounding tissues such as the aorta. b-c) Boxplot of the FA spread in the 3D heart ROI of all 27 subjects for default (b) and 4kT-UP (c) demonstrating the FA homogeneity across all B₁⁺ predictions using the 4kT-UP pulse.

Figure 5: B₁⁺ predictions and reconstructed, respiration corrected 3D GRE images for two unseen test cases with 4kT-UP. These two volunteers were not part of the optimization. The 3D images are free of breathing artefacts and demonstrate, despite some differences close to the coil elements, the feasibility to achieve a homogeneous calibration-free FA of the whole heart. The remaining signal changes in the AP direction of the acquired images are a result of receive (B₁^-) variations.