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Cross modality correspondence

PET-MRI correspondence

When sharing MRI data alongside with PET data, please pay specific attention to the format the MR images are in. It is important to note whether the MR images have been unwarped in order to correct for gradient non-linearities, indicated by the NonlinearGradientCorrection metadata field (see Magnetic Resonance Imaging Data - Sequence Specifics). The reason for this is that the MRI needs to be corrected for nonlinear gradients in order to fit the accompanying PET scans for co-registration (Knudsen et al. 2020, doi:10.1177/0271678X20905433; Norgaard et al. 2019, doi:10.1016/j.neuroimage.2019.05.055).

MRS-MRI correspondence

It is typical to acquire high-resolution 3D anatomical MR images alongside MRS data for voxel/slab placement, co-registration, and partial-volume tissue correction of metabolite concentrations. To avoid incorrectly matching an MRS dataset with a corresponding anatomical MR image, it is RECOMMENDED that the field AnatomicalImage be included in the MRS sidecar JSON files.