High-resolution human diffusion tensor imaging using 2-D navigated multishot SENSE EPI at 7 T.

Area of Science:

• Magnetic Resonance Imaging
• Medical Physics
• Neuroimaging

Background:

• Parallel imaging combined with partial Fourier acquisition enhances diffusion-weighted single-shot EPI, standard at 1.5-3 T.
• High field (7 T) MRI faces challenges like off-resonance effects and reduced T2* relaxation, causing artifacts.
• Multishot EPI reduces artifacts but complicates motion correction due to phase aliasing.

Purpose of the Study:

• To introduce a novel acquisition and reconstruction method for diffusion-weighted multishot EPI at high magnetic field strength (7 T).
• To address challenges in motion correction for accelerated, diffusion-weighted multishot EPI.
• To improve image quality and reduce artifacts in 7 T diffusion imaging.

Main Methods:

• Developed a modified Sensitivity Encoding (SENSE) algorithm, termed Image Reconstruction Using Image-space Sampling function (IRIS).
• Utilized a multishot approach for k-space traversal to accelerate data acquisition.
• Incorporated 2-D navigator phase information for correcting shot-to-shot phase errors in vivo.

Main Results:

• Successfully reconstructed highly aliased diffusion-weighted data from human studies at 7 T.
• Achieved submillimeter in-plane resolution in the final images.
• Demonstrated significant reduction in ghosting, blurring, and off-resonance artifacts compared to conventional methods.

Conclusions:

• The IRIS method provides an effective solution for diffusion-weighted multishot EPI at 7 T.
• This technique overcomes limitations of conventional methods, enabling high-quality imaging at ultra-high fields.
• Facilitates improved diagnostic capabilities in neuroimaging and other applications requiring high-resolution diffusion MRI.