I have a question concerning calculation of absolute amplitudes in QUEST and AQSES:
When I use “Relative amplitudes/water amplitude” and select water unsupressed signal as a reference, what is the unit of calculated amplitude for metabolites? It is not marked in the table after the calculation, but I suppose that I get the amplitude in terms of mmol/l?
I am not sure about the units, because I get very strange concentrations as the result:
1. For 100 mmol/l Gln phantom, when I calculate the concentration in reference to water I get 2.071×10^3! Similar huge values also for other phantoms.
2. Calculating metabolites from in vivo spectra gives more reasonable numbers, but still 2-3 times too high above the expected concentrations.
What would be the problem in this matter?
And also, what are the possible values for “Acquisition correction” and “Tissue correction” to be used in calculating concentration in reference to water?
I will really appreciate your help.
Thank you very much Michal for your response.
Unfotrunately, I am not able to use the Clinical Examination and DICOM plugins, because we work on Bruker animal system, and apparently such data format is not respected by the plugins (I cannot load my data with the plugins).
I saw in many publications where QUEST was used, that analysts are quantifying absolute concetrations in reference to unsupressed water signal. So I am curious, what else could be done with such a workflow, to get the closest to real concentrations?
Another way could be using one chosen metabolite as reference (ex Cr or NAA), but unfortunately I do not have biochemical data to be sure of exact reference concentration.
Are there any additional ways to quantify the absolute amplitudes?