Fig. 11

‘Partition-encoding aliasing’ in 3D imaging. Demonstration of partition-encoding aliasing (or “wraparound”) due to slab excitation profile imperfections. An ideal but impossible excitation profile would be as in (a), exactly matching the FOV in the slab direction. Using a narrower excitation pulse (b) loses SNR in the edge partitions, whilst in (c) exciting signal outside the FOV leads to wraparound contamination of many more partitions. A more realistic ideal scenario than (a) is shown in (d) whereby only the outermost partitions are affected by wraparound and these are usually not displayed. Due to timing constraints in 3D FPP, and therefore the short RF pulses used, avoiding results such as (e) is a distinct challenge