Can Quadruple Quantum Filtering Enhance Lactate Detection?

Motivation: Metabolites exhibiting J-coupling (like lactate) can be selectively detected against overlapping signals using multi-quantum filtering (MQF). Accurate modelling of such spin systems under realistic RF and gradient pulses is crucial for optimizing signal yield, background suppression and quantification. Goal(s): Improve MQF sequences to mitigate the inherent 50 % signal loss of double-quantum filters. Approach: The effect of realistic RF-pulses (hard/selective, various phases) and gradients on an AX3 system’s higher-order coherences was investigated. Semi-LASER-based spin-echo sequences were simulated in pyGAMMA and tested on a 7T scanner. Results: Quadruple-quantum coherences maintain near-100 % signal, outperforming traditional DQF. Simulations and phantom experiments agreed within 6 %. Impact: Quadruple-quantum filtering of lactate can retain its full signal, promising faster and more precise lactate quantification in human tissues. This could significantly improve the monitoring of glycolytic and oxidative metabolism and thus the understanding of underlying mechanisms in disease.