xASL_wrp_CreateBiasfield submodule should be checked for whether it is up-to-date, as there were a few issues along the way:

1. @ line 47:

   pGMname = fullfile(x.D.TemplateDir, 'rc1T1.nii')

should instead be

pGMname = fullfile(x.D.MapsSPMmodifiedDir, 'rc1T1.nii')

There may be other such file location related issues.

2. xASL_stat_RobustMean within the CreateBiasfield submodule encounters a fatal error at line 78:

   NotOutliers = ~(Deviation>ThresholdDeviation)';

Deviation has dimensions (121, 145, 121, nScan) ; This is based on the input image IM having those dimensions.

The docstring of RobustMean suggests that the input template should be 2D not 4D, so I am assuming that the IM in CreateBiasfield, line 113:

NoOutliers = xASL_stat_RobustMean(IM); % use SoS function

Is either incorrectly configured as 4D or some preprocessing needs to take place to make it a 2D, presumably into shape (2122945, nScan). Was the intent to have the preceeding line 107 instead as?:

IM(:, ScanN) = xASL_im_IM2Column(xASL_io_Nifti2Im(FileName), x.WBmask);

3. Assuming such a fix, the submodule seems to proceed with "Rescaling CBF images for intensity biasfield ..." encounters a fatal error at ~line 297:

   'Index exceeds the number of array elements (3).

   Error in xASL_wrp_CreateBiasfield (line 297)
   IM{iSite}(:,iNext(iSite)) = xASL_im_IM2Column(xASL_io_Nifti2Im(FileName),x.WBmask);

Is the variable iNext around that area supposed to be only a vector of placeholder ones of length 3? Was the intent to have it the same length as the number of Sites, nSites? The submodule concludes (successfully?) when this change is made.

4. If qCBF files start out as .nii.gz , then Biasfield_Multipl* files are possibly mislabelled with the extension .nii.gz while suspiciously having a filesize akin to uncompressed .nii files (>= 5 MB).