Quantification and correction of respiration induced dynamic field map changes in fMRI using 3D single shot...

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Respiration introduces dynamic changes in magnetic field maps within the brain.
• These field map variations contribute to physiological noise in functional Magnetic Resonance Imaging (fMRI).
• Such noise can obscure the underlying Blood Oxygenation Level Dependent (BOLD) signal.

Purpose of the Study:

• To quantify respiration-induced dynamic field map changes in the brain.
• To investigate the impact of these changes on the magnitude signal (physiological noise).
• To evaluate the effectiveness of dynamic off-resonance correction in reducing signal fluctuations.

Main Methods:

• Utilized a single-shot whole-brain imaging technique with 100 ms temporal resolution.
• Measured dynamic off-resonance maps derived from incremental changes in image phase.
• Applied these maps to dynamically update the off-resonance corrected image reconstruction.

Main Results:

• Identified a global resonance offset and a head-to-foot gradient as primary components of respiration-induced changes.
• Demonstrated an average reduction of approximately 30% in magnitude signal fluctuations after correction.
• Validated the efficacy of dynamic off-resonance correction in mitigating physiological noise.

Conclusions:

• Single-shot 3D imaging enables robust quantification of dynamic off-resonance changes in the brain.
• Correction for these dynamic off-resonance changes effectively removes physiological noise.
• This technique improves the reliability of T2*-weighted fMRI by reducing signal fluctuations related to dynamic point spread function changes.