Three-dimensional arbitrary voxel shapes in spectroscopy with submillisecond TEs.

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Neuroimaging

Background:

• Accurate in vivo metabolite quantification requires precise spatial and spectral selection.
• Achieving submillisecond echo times (TE) is crucial for detecting labile metabolites.

Purpose of the Study:

• To develop and validate a novel spectroscopic method for submillisecond TEs and 3D arbitrarily shaped voxels.
• To evaluate the method's performance with and without parallel excitation (PEX).

Main Methods:

• A segmented spherical shell excitation trajectory with radiofrequency weighting was employed for 3D target selection.
• Phantom measurements assessed spectral quality, signal-to-noise ratio (SNR), and outer volume suppression.
• In vivo human brain measurements were performed on a clinical system, followed by LCModel quantification.

Main Results:

• Submillisecond TE (955 µs) was achieved with excellent spectral quality and comparable SNRs in accelerated (R=2) and nonaccelerated modes.
• Outer volume signal suppression factors of 1434 (clinical) and 2246 (PEX) were observed, with spectral contamination of 10.2% and 6.5%.
• In vivo brain scans demonstrated good SNR, spatial/spectral selection, and accurate quantification of eight metabolites.

Conclusions:

• The novel spectroscopic method allows for rapid, high-quality 3D chemical analysis at submillisecond TEs.
• The technique is suitable for in vivo neurochemical profiling, offering accurate metabolite quantification.