Longitudinal relaxation time editing for acetylcarnitine detection with 1 H-MRS.

PURPOSE: Acetylcarnitine formation is suggested to be crucial in sustaining metabolic flexibility and glucose homeostasis. Recently, we introduced a method to detect acetylcarnitine in vivo with long TE 1 H-MRS. Differences in T1 relaxation time between lipids and acetylcarnitine can be exploited for additional lipid suppression in subjects with high myocellular lipid levels.

METHODS: Acquisition of spectra with an inversion recovery sequence was alternated with standard signal acquisition to suppress short T1 metabolite signals. A proof of principle experiment was conducted in a lean subject and the new approach was subsequently tested in four overweight/obese subjects.

RESULTS: Using the new T1 editing approach, lipid signals in spectra of skeletal muscle can be (additionally) suppressed by a factor of 10 using a TI of 900 ms. Combination of the long TE protocol with the T1 editing resulted in a well-resolved acetylcarnitine peak in the obese subjects.

CONCLUSION: The T1 editing approach suppresses short T1 metabolites and offers a new contrast in 1 H-MRS. The approach should be used in combination with a long TE in subjects with high lipid contamination for accurate quantification of the acetylcarnitine concentration. Magn Reson Med 77:505-510, 2017. © 2016 International Society for Magnetic Resonance in Medicine.