QUEST – amplitude values

[Gasper Zupan]

I am using spectroscopy date from our Philips 3T MR (Dicom format). I produced metabolite list in NMRSCOPE-B and afterwards I ran QUEST quantization tool. Everything worked quite amazing (especially considering that I am a newbie in this field) but I got very small amplitudes – range of around 5e-5 or e-4.

Its probably hard to pinpoint what went wrong over the internet but still: if anybody has an idea what might be wrong or where I did a mistake, please write it 🙂

Thank you,
Gasper

[Michal Jablonski]

Dear Gasper,

Small amplitudes are perfectly fine – QUEST just does not know what is the reference level.

In order to bring your amplitudes to the correct level please use in results mode “Options/Relative amplitudes” functions. You could fix the amp by any known metabolite (e.g. Cr should be 5.2) or user water reference from an external file (unsuppressed water signal).
Select the option that suits you the best.

Best regards
Michal Jablonski
jMRUI developer

[Gasper Zupan]

Thank you Michal!

I have one more question not directly related to the topic, but I dont want to open new thread just for it.

In NMRSCOPEB, when you open Pulse sequence – Protocol and you get parameters of a sequence, e.g. PRESS, some abbreviation are written that I am not familliar with and therefore I can not look them up in our MRI data: TE1_us, TR_us, TP_us and D1_us.

If anyone would be so kind to explain those to me I would be very grateful. We are using Philips 3TX Achieva.

[Anna Orzylowska]

Hi Michal,
I have also a question uder the same topic:
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.
Kind regards,
Anna

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