Author: Ged Ridgway (198.28.92.---)
Date: 10-25-07 10:22
Dear all,
Are there any limits on the sizes of NIfTI files, for example if the number of voxels, elements, or bytes exceeds the capacity of the int32 data type?
This is particularly relevant for 5D data. In 3D, an int32 limit could be surpassed by 1300x1300x1300 voxels, but this very large by current standards; however, consider a 5D dataset of multivariate observations for a number of subjects. As one example, data with 180x180x180 voxels (not unreasonable for 1mm-isotropic MRI, and high field structural MR could easily exceed this), 64 subjects, and multivariate 6-vectors stored at each voxel would have more elements than int32 can count. As another example, a 4D time-series of (univariate) single-precision floating-point data for 100 scans of the same voxel dimensions would have more *bytes* than int32 could index. These examples don't seem completely outrageous... but I'd be interested to hear what others have to say...
Possibly everything should be okay as long as individual dimensions are within the integer limits, which would almost always be true, but I wonder if many implementations might combine the five dimensions to create a single int32 index for the elements? What does the canonical nifti c-library do?
Many thanks,
Ged.
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