Fig. 4.

Variations on the scheme described in Fig. 3 may be applied. a) More ‘synthetic frames’ (highlighted in gray) may sometimes be used than shown in Fig. 3a. b) To extract near-DC information (either to generate sensitivity maps or as part of an artifact-suppression strategy), the processing may have to be repeated once or more times with filters of different bandwidths than the one in Fig. 3b. See text for more details.