Outlook on zero/ultrashort echo time techniques in functional MRI

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Biophysics

Background:

• Blood oxygenation level-dependent (BOLD) contrast using echo planar imaging (EPI) is the standard for functional MRI (fMRI).
• EPI-based fMRI faces challenges like motion sensitivity, signal dropouts, and acoustic noise.
• Alternative fMRI strategies are needed to overcome these limitations.

Purpose of the Study:

• To provide an overview of free induction decay (FID)-based fMRI techniques using zero/ultrashort echo time (TE).
• To compare the benefits and drawbacks of zero/ultrashort TE fMRI with conventional EPI-based fMRI.
• To discuss the potential of zero/ultrashort TE fMRI for future research and clinical applications.

Main Methods:

• Review of free induction decay (FID)-based functional MRI (fMRI) techniques.
• Comparison of zero/ultrashort echo time (TE) fMRI with conventional echo planar imaging (EPI)-based fMRI.
• Discussion of initial findings and ongoing developments in zero/ultrashort TE fMRI.

Main Results:

• Zero/ultrashort TE fMRI techniques inherently address many EPI-based fMRI shortcomings.
• Robust functional contrast has been demonstrated in human and animal studies using zero/ultrashort TE fMRI, primarily through inflow effects.
• These novel methods show promise for applications where EPI is limited.

Conclusions:

• Zero/ultrashort TE fMRI presents a powerful alternative to EPI-based fMRI.
• This technique is expected to advance basic, clinical, and preclinical research, particularly in challenging scenarios.
• Future applications include ultrahigh magnetic fields, awake animal studies, multimodal imaging, and non-brain fMRI.