Lactate and β-hydroxybutyrate are important MRS-visible biomarkers for the energy metabolism of the human brain. A major obstacle for their unambiguous detection and quantification in vivo is their inherently low concentration and spectral overlap with resonances from lipids and macromolecules. In this work, we demonstrate the improved detectability of lactate and β-hydroxybutyrate with MEGA-sLASER compared to MEGA-PRESS at the clinical field strength of 3 T. The method is validated by numerical simulations, in vitro measurements and in vivo experiments on healthy subjects. It is demonstrated that MEGA-sLASER offers an SNR increase of approximately 70% for lactate and β-hydroxybutyrate detection compared to MEGA-PRESS in various brain regions. This increased SNR translates into reduced Cramér-Rao lower bounds for quantification and enables a more robust detection of subtle changes in the (brain) energy metabolism. The sensitivity of the method for detection of β-hydroxybutyrate concentration changes is demonstrated through measurements before and during a ketogenic diet while the sensitivity for detection of lactate concentration changes is shown by measurements before and after an intensive anaerobic exercise.
Keywords: MEGA-sLASER; anaerobic exercise; difference editing; energy metabolism; ketogenic diet; lactate; lipid contamination; β-hydroxybutyrate.
© 2019 John Wiley & Sons, Ltd.