There are multiple definitions:

1. apparent signal-to-noise ratio(English)

   • CNR, fMRI, fSNR, MRA, SNR
   • Signal analysis
   • https://doi.org…93019-1/50015-0
   • https://doi.org….1002/mrm.25097

2. anatomical signal-to-noise ratio(English)

   • defined as the signal in a voxel divided by the standard deviation of the signal across a region without structure, generally selected to be a region outside the brain in air
   • fSNR, MRA, SNR, CNR, fMRI, fSNR, MRA, SNR
   • Medical imaging, Brain (dys)function
   • https://doi.org…93019-1/50015-0
   • https://doi.org…93019-1/50015-0