Fig 3.

GRE images of one volunteer. Five sessions of GRE images in the same volunteer as in Fig. 2 are shown for FB and BH of pTx (RF shimming and RF design), as well as qTx. The window level and width of these images are the same in GRE images and CV maps, respectively. CV maps calculated from those five images are also shown. GRE images show variations across five sessions with FB (top and fourth row), while they are constant for BH (second and fifth row), both for RF shimming and RF design. Images are also constant in qTx (third and sixth row). As a result, CV maps have higher values in FB compared to BH and qTx, indicating a better reproducibility in BH than in FB. Note that the high-intensity area in the center of brain in qTx is better in RF design. BH, breath-holding; CV, coefficient of variation; FB, free-breathing; GRE, gradient echo; pTx, parallel transmission; qTx, quadrature transmission. RF, radiofrequency.