Does superficial fat affect metabolite concentrations determined by MR spectroscopy with water referencing?

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Recent reports indicate local fat depots cause frequency-dependent signal attenuation in brain magnetic resonance spectroscopy (MRS).
• This reported effect, if general, could challenge the validity of internal reference signals and quantitative MRS.
• Investigating this potential artifact is crucial for reliable MRS applications.

Purpose of the Study:

• To verify the reported frequency-dependent signal attenuation in brain MRS caused by local fat depots.
• To identify potential causes of the reported effect.
• To assess the continued validity of quantitative MRS and water referencing.

Main Methods:

• Data acquisition using varied settings: two field strengths, two MR scanner vendors, different water suppression sequences, RF coils, localization sequences, and echo times.
• Utilized lipid/metabolite phantoms for controlled experiments.
• Systematic replication attempts under diverse conditions.

Main Results:

• The reported frequency-dependent signal attenuation in brain MRS could not be reproduced across any tested acquisition settings.
• No significant evidence was found to support the hypothesis that local fat depots generally cause substantial signal attenuation in quantitative MRS.
• The experiments demonstrated robustness of MRS quantification under various parameters.

Conclusions:

• The previously reported effect of fat depots causing signal attenuation in brain MRS was not reproducible.
• Quantitative MRS and the use of water referencing remain valid and reliable techniques under standard acquisition conditions.
• This study reaffirms the utility of MRS for accurate metabolite quantification in the brain.