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

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.

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.

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.

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.