How to calculate signal to noise ratio (SNR) in an MP2RAGE image (UNIT1) in multiple ROIs?

Hi everyone!

I want to calculate and compare the SNR of different ROIs in a MP2RAGE image acquired at 7T. A MP2RAGE image is the combination of 2 images acquired at different inversion times. I have the MP2RAGE image and the inv1 and inv2 images, for 2 sessions.

I have looked at the comparisons made by Dietrich et al. (2007) ( about the validity of some SNR calculation approaches. I was wondering if I can have some insights about the best approach for the special case of a MP2RAGE image.

Thank you for your help!