Spherical echo-planar time-resolved imaging (sEPTI) for rapid 3D quantitative T 2 * and susceptibility imaging.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Quantitative Susceptibility Mapping (QSM)

Background:

• Echo-planar imaging (EPTI) is crucial for rapid MRI but suffers from artifacts.
• Existing EPTI methods require improvements in speed and image quality for clinical applications.

Purpose of the Study:

• To develop a 3D spherical EPTI (sEPTI) acquisition and reconstruction pipeline.
• To achieve rapid, high-quality whole-brain submillimeter quantitative susceptibility mapping (QSM).

Main Methods:

• Utilized spherical k-space coverage with variable echo-spacing and ramp-sampling for efficient sEPTI acquisition.
• Incorporated iterative B0 estimation and phase correction for artifact mitigation.
• Employed a physics-informed unrolled network to enhance signal-to-noise ratio (SNR) for accelerated imaging.

Main Results:

• sEPTI achieved 1.4x faster imaging with superior image quality and quantitative map precision compared to conventional EPTI.
• Improved reconstruction performance with reduced artifacts due to B0 update and phase correction.
• The unrolled network enabled high-quality $$ and QSM quantification from single-average data, validated in healthy subjects and pediatric patients.

Conclusions:

• sEPTI enables distortion-free, whole-brain multi-echo imaging and $$ and QSM quantification at 0.75mm resolution in 90s.
• The developed pipeline demonstrates potential for broad clinical applications.
• This rapid imaging technique can significantly benefit neuroimaging research and diagnostics.