Accelerated radial echo-planar spectroscopic imaging using golden angle view-ordering and compressed-sensing...

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopic Imaging
• Medical Physics

Background:

• Accelerated Magnetic Resonance Spectroscopic Imaging (MRSI) is crucial for clinical applications.
• Undersampled echo-planar spectroscopic imaging (EPSI) with compressed sensing is a common acceleration technique.
• Optimizing speed and quality in MRSI remains a key challenge.

Purpose of the Study:

• To implement and evaluate a novel, accelerated 2D radial echo-planar spectroscopic imaging (REPSI) sequence.
• To compare the performance of REPSI against an undersampled Cartesian spectroscopic sequence using compressed sensing.
• To assess the impact of undersampling and compressed sensing on image and quantitation quality.

Main Methods:

• A 2D REPSI sequence was developed using golden-angle view-ordering on a 3T MRI scanner.
• Radial and Cartesian EPSI data were acquired at multiple acceleration factors with time-equivalent durations.
• Compressed sensing with total variation regularization was used for reconstruction of prospectively and retrospectively undersampled phantom and in vivo brain data.

Main Results:

• Accelerated REPSI tolerated greater scan time reductions than Cartesian EPSI.
• REPSI achieved a 2.5-fold reduction in scan time while preserving image and quantitation quality.
• Metrics including spectral and metabolite map errors, and concentration estimates showed superior performance for REPSI (e.g., N-acetyl aspartate REPSI=9.4% vs EPSI=16.3% at acceleration factor 2.5).

Conclusions:

• Accelerated MRSI using undersampled radial echo-planar acquisitions offers superior reconstruction accuracy and quantitation compared to Cartesian EPSI.
• The REPSI approach with compressed sensing provides a better balance between imaging speed and quality.
• Radial undersampling with compressed sensing can significantly reduce 2D spectroscopic imaging acquisition time.