# SNR calculation comparable to dipy? **URL:** https://community.mrtrix.org/t/snr-calculation-comparable-to-dipy/667 **Category:** Uncategorized **Created:** [January 19, 2017, 3:54pm UTC](https://community.mrtrix.org/t/snr-calculation-comparable-to-dipy/667 "2017-01-19T15:54:20Z") **Posts on this page:** 1 **Showing post:** 5
### Author: ![jdtournier](https://community.mrtrix.org/user_avatar/community.mrtrix.org/jdtournier/32/2594_2.png) [@jdtournier](https://community.mrtrix.org/u/jdtournier) #### Post date: [April 18, 2017, 8:42pm UTC](https://community.mrtrix.org/t/snr-calculation-comparable-to-dipy/667/5 "2017-04-18T20:42:22Z")
> [@mblesac](#): > > is there any minimal SNR for cSD to work on the images? It’s a difficult one to answer exactly, but in my experience when SNR drops below ~15 (as measured in the _b_=0 images within the region of interest), things start to look a bit messy. My suspicion is that at this SNR level, and when looking at _b_ ≈ 3000 s/mm², the SNR in the DW images is getting too close to 1 for comfort. At this level, even lots of measurements won’t necessarily help all that much since the Rician bias will wash out the contrast. As to where to find that information, well to be honest, there isn’t really any particular reference for that. Part of the problem is that there is an interaction with the Rician bias, but also with the _b_-value, the number of volumes acquired, the use of parallel imaging, etc, all of which complicates things a bit. So my SNR \> 15 recommendation really is just my personal experience… --- _[View the full topic](https://community.mrtrix.org/t/snr-calculation-comparable-to-dipy/667)._