AVWUTILS - Miscellaneous Image Utilities | ![]() |
AVWUTILS is a set of useful command-line utilities which allow the conversion, processing etc. of Analyze/AVW and Nifti format data sets. Many of them work on both 3D and 4D data. For each of these programs, type just the program name to get the usage help.
The different AVWUTILS programs are:
avg152
standard images - equivalent to the appropriate
sform or qform in a Nifti file having a negative
determinant).
In Nifti files it is possible to independently report or modify the qform or sform fields. However, the FSL3.3 output routines will try to keep qform and sform matrices the same whenever one would otherwise be unset. Therefore it is not possible, for instance, to delete only the qform, as if the sform is set then doing this will result in the qform being set equal (or nearly equal) to the sform. This is currently done to aid interoperability with other packages. If both qform and sform are given different values though, these are preserved by the output routines.
This command does not change the data storage at all - only the
orientation information in the header.
It is also possible to use avwswapdim to swap the left-right order of the data, in which case a warning will be output. Also, in this case, it will not change the left-right ordering (i.e. radiological/neurological) information in the header. Therefore after swapping left-right (e.g. using -x y z as arguments) the viewed image in FSLView or slices will be different. If the header information is also appropriately swapped (by using avworient) then the image will display as it originally did, although the data will be stored in a different order. With this command it is possible to change incorrectly reconstructed data to match its header description, or to swap between neurological and radiological storage (if used in conjunction with avworient), but please use with extreme care - otherwise the left and right sides of the image may be set incorrectly!
Finally, changes to the left-right ordering by swapping other axes besides the x-axis can also be done, and these will issue the same warning. However, when doing this, avwswapdim also modifies the header information about the ordering in the first voxel dimension (x) in order to maintain the previous left-right ordering in the header. This can result in confusing outputs, and so avwswapdim should not be used to change left-right ordering except by swapping the x axis. Other reorderings can be done by: (1) changing into the standard image orientation (axial) - without swapping the left-right order; (2) swapping left-right, which will now be the x axis; and (3) swapping back into the original slicing (e.g. sagittal) with another avwswapdim that does not swap the left-right order. Note that whenever a left-right order swap would occur, avwswapdim will issue a warning message.