Localized two-dimensional shift correlated MR spectroscopy of human brain

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Neuroscience

Background:

• MR spectroscopy (MRS) is crucial for non-invasive metabolite analysis.
• Existing techniques face limitations in whole-body applications and metabolite specificity.
• 2D COSY sequences offer enhanced spectral resolution and metabolite identification.

Purpose of the Study:

• To develop and validate a novel 2D chemical shift correlated MR spectroscopic (COSY) sequence for whole-body applications.
• To theoretically calculate volume localization and coherence transfer efficiencies for the proposed 2D MRS sequence.
• To demonstrate the capability of the localized COSY (L-COSY) technique for in vivo human brain metabolite analysis.

Main Methods:

• A new volume localization technique (90°–180°–90°) was integrated into a 2D COSY sequence for whole-body MRS.
• Theoretical calculations using product operator formalism were performed to assess localization and coherence transfer.
• Phantom studies were conducted for sequence optimization, utilizing combined RF coils (head/surface receive, body transmit).

Main Results:

• The proposed 2D MRS sequence successfully identified J cross-peaks for key brain metabolites including NAA, Glx, mI, Cr, Ch, Asp, GABA, Tau, GSH, Thr, and MM.
• Asymmetric cross-peak intensities relative to diagonal peaks were observed, characteristic of the 2D COSY method.
• Localized COSY (L-COSY) spectra were successfully acquired from cerebral prefrontal and occipital gray/white matter regions in 15 healthy controls.

Conclusions:

• The integrated 2D COSY sequence with the novel localization technique provides efficient whole-body MRS.
• The L-COSY method enables robust detection and differentiation of various brain metabolites.
• This technique holds promise for advanced in vivo neurochemical profiling and diagnostic applications.