Postexercise Lactate Clearance, T₂ Relaxation, and J-Modulation in Human Skeletal Muscle Measured With Double-Quantum...

Area of Science:

• Biophysics
• Skeletal Muscle Physiology
• Metabolic Research

Background:

• ¹H MRS lactate measurements are crucial for understanding skeletal muscle energy metabolism.
• Technical challenges, such as overlapping lipid signals, hinder accurate lactate detection.
• Novel spectral filtering techniques are needed to overcome these obstacles.

Purpose of the Study:

• To develop and validate a novel 3D localized, CH-selective double quantum filter (DQF) sequence for dynamic post-exercise lactate measurement.
• To enable single-shot measurement of cellular lactate T₂ and clearance kinetics in working skeletal muscle.
• To improve the detection and quantification of lactate signals in the presence of lipid resonances.

Main Methods:

• A novel CH-selective DQF sequence was applied to postexercise calf muscle in 11 subjects using a 7T ¹H transceiver coil.
• Acquisitions involved interleaved constant and incrementing echo times (T_E) to measure lactate decrease and T₂.
• The CH-selective sequence was compared against its nonselective variant.

Main Results:

• The CH-selective DQF sequence clearly detected lactate in 4-second single-shot spectra post-exercise.
• Lactate clearance half-life (t_1/2) was 162 ± 42 s, and T₂ was 138 ± 20 ms.
• The new sequence provided a 2.3 times higher signal compared to the nonselective variant, with accurate scalar coupling constant (J) fitting.

Conclusions:

• The developed sequence significantly enhances lactate detection and quantification in skeletal muscle post-exercise.
• This method offers time resolution comparable to ³¹P MRS, facilitating dynamic metabolic studies.
• It provides a foundation for future absolute quantification and compartmentation studies of intramuscular lactate.