While most MRI data with multi-channel coils is saved and converted to images only in its combined state, one can reconstruct both magnitude and phase data from each coil separately.
My understanding is that coil-level data is necessary for quantitative susceptibility mapping with SWI data, which is why BEP-004 proposes the addition of a "coil" entity. However, coil-level data can also be used in other modalities, including fMRI, where phase-based denoising can be improved by incorporating coil-level phase data (which @CesarCaballeroGaudes and @ostanley most likely know more about than me).
While most MRI data with multi-channel coils is saved and converted to images only in its combined state, one can reconstruct both magnitude and phase data from each coil separately.
My understanding is that coil-level data is necessary for quantitative susceptibility mapping with SWI data, which is why BEP-004 proposes the addition of a "coil" entity. However, coil-level data can also be used in other modalities, including fMRI, where phase-based denoising can be improved by incorporating coil-level phase data (which @CesarCaballeroGaudes and @ostanley most likely know more about than me).