Reducing susceptibility artifacts in fMRI using volume-selective z-shim compensation

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Brain Function Analysis

Background:

• Susceptibility-induced magnetic field gradients (SFGs) cause significant signal loss in the orbitofrontal cortex (OFC) during gradient-echo fMRI.
• Conventional z-shim techniques can restore OFC signal but increase scan time, limiting their routine use.

Purpose of the Study:

• To develop and validate a modified, time-efficient z-shim technique for improved fMRI signal recovery in the OFC.
• To assess the feasibility of detecting OFC activation using this enhanced technique in whole-brain fMRI studies.

Main Methods:

• Implementation of a modified z-shim technique applying compensation to a selective volume with severe susceptibility artifacts.
• Conducting a functional MRI study with N=6 participants to evaluate the technique's performance.
• Acquisition of whole-brain fMRI data with a temporal resolution of 2 seconds.

Main Results:

• The modified z-shim technique successfully compensated for susceptibility-induced signal loss in the OFC.
• Detection of OFC activation was feasible with the enhanced z-shim method.
• The technique maintained high imaging efficiency, suitable for routine fMRI.

Conclusions:

• The presented modified z-shim technique offers a time-efficient solution for overcoming OFC signal loss in fMRI.
• This method enables robust detection of OFC brain activity, crucial for understanding cognitive functions.
• The technique is suitable for routine whole-brain fMRI studies requiring high temporal resolution.