Table 2.

Technical failures of the vNAV by group for the 52 children scanned using the vNav PRESS acquisition in 2010.

Number of scans affected	Description	Total Exposed (FAS, N = 37)	Total Controls (N = 15)
5	Phase unwrapping algorithm generated a 2π phase offset, resulting in a frequency shift of 208 Hz. This rendered water suppression ineffective.	3	2
4	Ghosting in the first vNav EPI volume rendered the vNav unusable. This resulted from large shim terms set by the scanner for the voxel.	3	1
2	Water substantially over-suppressed (50% in these cases) as a result of a suboptimal pre-scan shim adjustment and resulting inappropriate water suppression adjustment.	2	0