could anyone comment on whether these appear to be usable data? we are seeing a very large bump in what we believe is the lipid/macromolecule section of spectra around 1ppm but the FWHM for NAA is 5.9 and the SNR for NAA is 140 which suggest the data might be good quality? we are new to interpreting the quality of data so any comments on how to look at spectra / qm parameters and draw conclusions are appreciated
thank you in advance
440 averages (14 min)
3 x 3 x3 voxel size
location: visual cortex
I don’t love it, but I agree this is borderline usable. You could also reduce the fit range to 1.7 to 4 ppm in the job file. (This is a good reminder that Osprey’s model doesn’t handle large random lipids with the same grace as LCModel does - we’re working on it…).
I thinknthat your spectrum has a huge lipid contamination for unstable outer volume suppression.
These are not macromolecules tgey are artifacts.
The contamination is important and thus the NAA signal might be also contaminated. I would not use tgese type of data. Sorry for being so direct :(.
Excellent example of “ask 10 spectroscopists, get 20 opinions”, and why we all need to find ways to replace opinion with evidence. Thanks @cudalbu
Did your volunteer move? Can you check the data repetition by repetition (i.e. average by average)?
Usually you can notice a change in phase for these extracranial lipids in individual scans.
Roland Kreis has a nice review on these and Ivan Tkac a nice talk at the MRS workshop 2018. You can find all this in the educ content on the MRSHUB
@cudalbu This is a sequence that does not use OVS or sat bands by default, so I would assume that the voxel was just placed a smidge too close to the scalp in the first place.
we are actually acquiring data live at this very moment to debug this artifact and as soon as we moved the voxel away from the scalp the bump disappeared … mystery solved!
We are a super team located at different corners of the globe :). This MRSHUB is amazing.
Congratulations for identifying the problem