Fig 1. Representative B₁ ⁺ maps and ROI placement.

Axial magnitude images (1^st column) through the center of the heart are used to select the heart (red) and cross sectional body area (blue) elliptical ROIs. The scanner routine was used to calculate RF-shim values localized to a manually drawn rectangle (green). Corresponding B₁ ⁺ maps acquired in quadrature mode pre-RF shimming and RF-shimmed are shown in the 2^nd and 3^rd columns, respectively. Data from two different animals A and B are shown in the two rows. Lengths of RL and AP were defined as the dash blue lines for RL/AP ratio calculation.