Submillimeter balanced SSFP BOLD-functional MRI accelerated with 3D stack-of-spirals at 9.4 T

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Functional MRI

Background:

• Balanced steady-state free precession (bSSFP) is valuable for functional neuroimaging.
• Conventional spoiled gradient-echo sequences have limitations in speed and resolution for ultrahigh-field functional studies.

Purpose of the Study:

• To enhance the speed of balanced SSFP (bSSFP) acquisition using segmented 3D stack-of-spirals for functional brain studies at ultrahigh fields.
• To achieve higher spatio-temporal resolution imaging for improved detection of brain activity.

Main Methods:

• An accelerated 3D stack-of-spirals sequence with water excitation for fat suppression was employed.
• Iterative reconstruction with corrections for system imperfections (e.g., B0 inhomogeneity) was used.
• Optimized protocols at submillimeter (0.6-mm, 0.8-mm isotropic) and 1.2-mm isotropic resolutions were evaluated.

Main Results:

• Water excitation and model-based iterative reconstruction improved image quality.
• BOLD-related signal changes were optimized by balancing echo time (TE) and repetition time (TR) for sensitivity and speed.
• Reproducible neural activations were detected with a median signal change of approximately 4% at submillimeter resolutions.

Conclusions:

• 3D stack-of-spirals enables passband bSSFP functional imaging at significantly higher spatial and temporal scales.
• This technique offers advantages over conventional spoiled gradient-echo train sequences for ultrahigh-field functional neuroimaging.