The affine transformation links voxel indices to a meaningful anatomical coordinate system. Because image data are stored as an array, the same voxel position is not inherently an anatomical location until this spatial relationship is applied. Registration, segmentation, and quantitative analysis can therefore use coordinates that correspond more meaningfully to brain anatomy rather than relying only on array positions.
Image dimensions, voxel sizes, data type, and orientation determine how software reads and interprets the stored intensities. Dimensions describe the array structure, voxel sizes establish spatial scale, data type controls how values are represented, and orientation helps preserve spatial meaning. Errors or inconsistencies in these fields can compromise downstream neuroimaging analysis.
Voxel intensities provide the measured image values, while spatial metadata explains where those values belong and how large each voxel is. Either component alone is insufficient for reliable interpretation: intensities without location cannot support anatomical mapping, and spatial information without values cannot describe the image. Together, they enable measurements from MRI, functional MRI, and diffusion imaging.
A typical workflow uses the stored image and its spatial information during preprocessing, followed by operations such as registration, segmentation, and quantitative analysis. Preprocessing prepares the data for subsequent analysis, registration aligns images within a meaningful coordinate system, and segmentation separates relevant structures or regions. The resulting measurements can support clinical and biological investigations.
NIfTI supports several neuroimaging modalities, including structural MRI, functional MRI, and diffusion imaging. These modalities produce data that can be processed within related analysis workflows, although their measurements address different aspects of the brain. Using a shared format helps place modality-specific results into compatible software pipelines for preprocessing, registration, segmentation, and quantitative evaluation.
Compatibility with widely used neuroimaging software allows investigators to exchange files and apply consistent analysis workflows across studies. The header preserves dimensions, voxel sizes, data type, orientation, and affine spatial information alongside the voxel array. Retaining these details reduces ambiguity when data move between tools and helps connect image-derived measurements with clinical and biological research.