There are multiple definitions:

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

   • calculated based on the local variability within the tissue region of interest
   • CNR, fMRI, fSNR, MRA, ROI, SNR
   • Signal analysis, Medical imaging
   • 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
   • CNR, fMRI, fSNR, MRA, SNR
   • Medical imaging, Brain (dys)function
   • https://doi.org…93019-1/50015-0
   • https://doi.org…93019-1/50015-0