BIDS error [Code 54] BOLD_NOT_4D

Dear BIDS experts,

In our study in which we tested different sequence variants, I acquired single-volume EPIs.
Related to the naming of these files, I already got a very helpful suggestion Single volume EPI data that worked perfectly!

However, I did notice that I am getting the following errors from the BIDS validator which makes sense as I do only have one volume.

   **[Code 54] BOLD_NOT_4D**
    Bold scans must be 4 dimensional.

    **[Code 75] NIFTI_PIXDIM4**
    NIfTI file's header is missing time dimension information.

I do not know how I should rename these files as the sequence was identical to the resting-state sequence but these acquisitions consisted of a single volume.

Thanks a lot in advance!!


Hi Merve,

It looks like you decided to use the bold suffix for good reasons, so I would just recommend adding a singleton fourth dimension to your one-volume BOLD files.


Hi @tsalo,

Thanks a lot for your quick reply!

Actually, I was thinking that I already had the 4th dimension. When I check my hdr info using the commands from FSL (with fslinfo or fslhd), I see the following:

dim1		128
dim2		128
dim3		24
dim4		1

Or did I misunderstand you?

Thanks a lot,


That does seem like it should be good. I don’t use FSL often, but I assume it doesn’t add empty dimensions to the header info. Is it possible that some of your files are 3D, while others are 4D? The validator should show a list of the files for which the BOLD_NOT_4D and NIFTI_PIXDIM4 errors were found.

Thanks for the reply!

Yes, in more detail the relevant hdr info looks like this

dim1 128
dim2 128
dim3 24
dim4 1
dim5 0
dim6 0
dim7 0
pixdim0 -1.000000
pixdim1 1.000000
pixdim2 1.000000
pixdim3 5.000000
pixdim4 2.312000
pixdim5 0.000000
pixdim6 0.000000
pixdim7 0.00000

Actually, all of my single-volume EPIs have the same hdr info…Which other tool would you recommend to check this?