Ghost peaks simulation and reduction in high-resolution echo-planar spectroscopic imaging with flyback readout

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Image Processing

Background:

• Echo-planar spectroscopic imaging (EPSI) is susceptible to Nyquist ghost spectral lines, which degrade spectral quality by reducing true peak intensity and signal-to-noise ratio.
• Ghost peaks arise from energy transfer in interleaved flyback gradient echo trains, complicating spectral analysis.

Purpose of the Study:

• To simulate Nyquist ghost spectral lines in EPSI using interleaved flyback gradient echo trains.
• To develop and validate methods for reducing ghost peaks in EPSI.
• To assess the impact of echo variations on ghost peak formation.

Main Methods:

• Simulated ghost spectral lines by reorganizing raw EPSI data into interleaved echo trains.
• Investigated the influence of temporal shifts, magnitude, and phase variations of echoes on ghost peak formation.
• Applied iterative zero-order phase corrections to reduce ghost peaks.

Main Results:

• Zero-order phase corrections significantly decreased ghost peak magnitudes.
• True spectral peak magnitudes were increased following phase correction.
• The proposed methods demonstrated effectiveness in phantom and in vivo (rat) studies.

Conclusions:

• Iterative zero-order phase corrections effectively reduce Nyquist ghost spectral lines in EPSI.
• The developed methods enhance spectral quality for applications like water-fat spectroscopy and imaging.
• The approach is suitable for high spatial and spectral resolution imaging.