Localized one-dimensional single voxel magnetic resonance spectroscopy without J coupling modulations

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Biomedical Engineering

Background:

• Proton magnetic resonance spectroscopy (MRS) is crucial for metabolite analysis in vivo.
• J coupling can cause amplitude and phase distortions in MRS spectra, complicating analysis.
• Existing methods often struggle to fully suppress J modulations across various echo times.

Purpose of the Study:

• To develop a novel pulse sequence for acquiring single-voxel localized 1D ¹H MRS.
• To eliminate J coupling modulations and associated spectral distortions.
• To enable acquisition at arbitrary echo times without compromising spectral quality.

Main Methods:

• Development of the PRESSIR pulse sequence incorporating a J-refocused module.
• Suppression of J coupling evolution using a 90° pulse within a double spin echo.
• Validation using a two-compartment phantom, MRS brain phantom, and pig brain tissue.

Main Results:

• The PRESSIR sequence demonstrated comparable voxel localization accuracy to the standard PRESS sequence.
• PRESSIR spectra were virtually free from amplitude and phase distortions caused by J modulations.
• PRESS spectra exhibited significant distortions, particularly at longer echo times.

Conclusions:

• The PRESSIR sequence facilitates acquisition of in-phase MRS spectra in a single scan.
• It enhances signal intensity for J-coupled metabolites and reduces broad resonances.
• PRESSIR enables direct measurement of non-overlapping J-coupled peaks and transverse relaxation times (T2s).