Inner-volume echo volumar imaging (IVEVI) for robust fetal brain imaging.

Area of Science:

• Magnetic Resonance Imaging
• Fetal Neuroscience
• Medical Imaging Technology

Background:

• Fetal functional MRI (fMRI) using conventional sequences is hampered by motion artifacts, leading to significant data loss.
• High temporal resolution is crucial for overcoming fetal and maternal motion during fMRI acquisition.

Purpose of the Study:

• To evaluate the feasibility of echo volumar imaging (EVI) combined with inner volume (IV) imaging (IVEVI) for fetal brain MRI.
• To assess IVEVI's ability to achieve high temporal resolution and freeze fetal head motion.

Main Methods:

• Modified multi-echo echo-planar imaging sequence with orthogonal excitation and refocusing for localized excitation.
• Shifted k-space center for T2* weighting and time efficiency; tested single- and multi-shot variants.
• Controlled acoustic noise and used image-based shimming to minimize B0 inhomogeneities in the fetal brain.

Main Results:

• Single-shot IVEVI achieved 3.5 × 3.5 × 5.0 mm³ resolution in fetal scans, with a readout duration of 383 ms.
• Multi-shot IVEVI demonstrated reduced geometric distortions compared to single-shot, but increased motion sensitivity.
• Effective echo times comparable to fetal gray matter T2* at 3T were achieved.

Conclusions:

• Fetal EVI presents challenges, particularly regarding acoustic noise and motion sensitivity.
• Multi-shot IVEVI reduces susceptibility-induced distortions but requires further optimization to improve motion sensitivity.
• Future research should focus on enhancing multi-shot IVEVI variants for robust fetal brain imaging.