Finally, what does a 1H-MRS precisely measure?

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1

Dear MRS experts,

I already asked some of you (@PGMM, @admin, …), but with no consensus explanation: What is exactly done during H-MRS quantification? I mean do we quantify only the free metabolites (or unbound) or the free metabolites + the metabolite in complex with them receptors (bound metabolites)?

Thank you,

Frederic

2

We quantify the concentration of metabolites based on the concentration of H( in H-MRS) in their structures.The metabolites need to be mobile and atleast 4 mM in order to be detected.

3

Thanks for your reply @NNeda.
Do you have any reference to the fact that in 1H-MRS, the most likely metabolites to be quantified are only the free or unbound metabolites?

4

Very briefly, bound molecules exhibit very small T2, and their signal has decayed substantially after the echo times we can achieve. See De Graaf, In Vivo NMR Spectroscopy, Chapter 3 “Dynamic Aspects”

and also

The line width of resonances are inversely proportional to the T2* relaxation time, which is
related to the rotational mobility of the metabolite. Metabolites with low mobility (e.g. bound
to macromolecular structures) give rise to very short T2 relaxation times and hence broad resonances, which can be unobservable in conventional NMR spectra.
De Graaf, In Vivo NMR Spectroscopy (Chapter 9)

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