Cardiac functional magnetic resonance imaging at 7T: Image quality optimization and ultra-high field capabilities

Figure 9 The effect of changing location of the dielectric pad on B1 field homogeneity in volunteers with large body habitus. The place of the pad is indicated by the orange arrow with respect to an axial cross-section of the subject’s chest region (white circle, where subject was scanned in the supine position; A: Anterior, P: Posterior, L: Left, R: Right). Results from an overweight volunteer [body mass index = 26.1 kg/m², chest expansions = 27 cm (AP) and 30 cm (LR)], as shown on long-axis (A) and short-axis (B) slices. B1 uniformity was acceptable without using the pad (image on the left), which was similar to the case when the pad was positioned in the anterior left position of the chest (image with red frame). Changing the pad position resulted in slightly worse B1 uniformity, as shown by regions of signal nulling (white arrows). This behavior was consistent in all scanned subjects with large body habitus.