Estimating relative diglyceride to triglyceride content with localized MRS at 3 T

Area of Science:

• Biomedical Engineering
• Magnetic Resonance Imaging
• Lipid Metabolism

Background:

• Proton magnetic resonance spectroscopy (MRS) is a powerful tool for in vivo metabolic studies.
• Distinguishing between diglycerides and triglycerides using MRS can be challenging due to overlapping resonances.
• Previous work demonstrated STEAM MRS at 3 Tesla can resolve triglyceride glycerol from water.

Purpose of the Study:

• To determine if STEAM MRS with an echo time (TE) of 100 ms facilitates relative quantification of diglyceride/triglyceride levels at 3 Tesla.
• To assess the accuracy of diglyceride quantification using specific STEAM MRS parameters.

Main Methods:

• Utilized stimulated echo acquisition mode (STEAM) MRS with varying echo times (TE) and a fixed mixing time (TM = 20 ms).
• Acquired spectra from phantoms containing tricaprylin (triglyceride) and dicaprylin (diglyceride) in known ratios.
• Analyzed glycerol resonances at approximately 4 ppm and 4.4 ppm to differentiate and quantify lipid species.

Main Results:

• STEAM MRS with TE = 40 ms and TE = 100 ms yielded two resolvable triglyceride glycerol resonances.
• The triglyceride contribution to the 4 ppm resonance could be estimated from the 4.4 ppm peak.
• Estimated concentration ratios of 1,3-dicaprylin/tricaprylin showed strong linear correlations (R² > 0.99) with expected ratios for both TE values.

Conclusions:

• STEAM MRS with TE = 100 ms (TM = 20 ms) enables the relative quantification of diglyceride and triglyceride levels at 3 Tesla.
• This MRS technique provides accurate estimations of lipid concentrations, valuable for metabolic research.
• The method is robust for distinguishing and quantifying mixtures of diglycerides and triglycerides.