# Diffusion-weighted magnetic resonance spectroscopy with selective refocusing

## TL;DR

This study improves diffusion-weighted magnetic resonance spectroscopy by combining selective refocusing and spectral editing to reduce errors in measuring brain metabolites like GABA.

## Contribution

The study introduces a modified dMEGA-PRESS sequence that reduces uncertainty in diffusion data for brain metabolites affected by J-modulations.

## Key findings

- The dMEGA-PRESS sequence enabled reliable spectral editing and quantification of GABA in metabolite phantoms.
- Selective refocusing and editing reduced uncertainty in diffusion data for GABA and Glutamate in phantoms and in vivo Glutamate/Glutamine data.
- Reliable diffusion data for GABA could not be obtained from in vivo spectra due to spectral overlap challenges.

## Abstract

To reduce errors from J-modulations and spectral overlap in dMRS of brain metabolites, this study combines the use of diffusion-weighted gradients with selective refocusing and spectral editing.

Bipolar gradients were combined with spectral refocusing and editing in a dMEGA-PRESS sequence. Experimental parameters were optimised for spectral editing of GABA, with co-editing of Glutamate and Glutamine. The method was tested in metabolite phantom solutions, followed by pre-clinical experiments on rats.

The dMEGA-PRESS sequence enabled reliable spectral editing and quantification of GABA. Selective refocusing and editing resulted in reduced uncertainty in the diffusion data for GABA and Glutamate in the metabolite phantoms, and also for the combined Glutamate/Glutamine diffusion data obtained in vivo. Reliable diffusion data for GABA was not possible to obtain from the in vivo spectra.

For metabolites with significant J-modulations but without spectral overlap, selective refocusing improved the quality of diffusion data. For metabolites with spectral overlap where editing is necessary, spectral subtraction makes it more challenging to improve the quality of diffusion-weighted data.

The dMEGA-PRESS sequence reduces the uncertainty in obtained diffusion data for brain metabolites that are significantly influenced by J-modulations.

The online version contains supplementary material available at 10.1007/s10334-025-01275-x.