Overdiscrete echo-planar spectroscopic imaging with correlated higher-order phase correction

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging
• Spectroscopy

Background:

• Proton Magnetic Resonance Spectroscopic Imaging (¹H MRSI) is crucial for non-invasive brain analysis.
• Existing methods often suffer from artifacts and limited signal-to-noise ratio (SNR), hindering detailed investigation.
• Fast and accurate ¹H MRSI at 3 Tesla (3T) is highly desirable for clinical applications.

Purpose of the Study:

• To develop and validate a robust methodology for accelerated ¹H MRSI of the brain at 3T.
• The goal is to achieve improved SNR and minimize phase-related artifacts.

Main Methods:

• An accelerated echo-planar spectroscopic imaging (EPSI) acquisition scheme was employed.
• This was combined with an overdiscrete reconstruction framework incorporating interleaved water reference scans.
• A generalized high-order spatial-temporal phase correction was implemented, estimated from reference scans and interpolated using a polynomial basis.

Main Results:

• The methodology successfully eliminated spectral artifacts caused by phase disturbances.
• In vivo experiments demonstrated mean SNR gains of 3.18 and 1.19 compared to standard reconstructions.
• EPSI with interleaved water acquisition proved robust to system instabilities and potential patient motion, with effective single-step phase distortion correction.

Conclusions:

• The overdiscrete reconstruction framework with high-order phase correction effectively corrects for B0 inhomogeneities, drift, eddy currents, and vibrations.
• This advanced reconstruction method, coupled with EPSI, significantly enhances measurement stability, SNR, spectral linewidth, and artifact removal in brain ¹H MRSI.