Enhanced Sensitivity of Multi-Echo Resting-State fMRI on a Cognitive-Normal Aging Cohort Using a Compact Head-Only 3T Scanner
Abstract
Purpose
Multi-echo(ME)-fMRI improves BOLD sensitivity compared with single-echo acquisitions by increasing temporal signal-to-noise ratio (tSNR) and sampling multiple-echoes in one repetition time. ME-fMRI particularly benefits from the head-only compact 3T (C3T) scanner’s high-slew-rate gradients (700 T/m/s), which shortens echo spacing that offsets the extra readout time required for ME and reduces geometric distortion. This study compared the performance of ME-fMRI acquired on a C3T scanner with a conventional whole-body 3T scanner in a large cognitive normal aging group study using resting-state fMRI.
Methods
Two age-matched healthy volunteer groups were recruited with written informed consent: one scanned on the C3T scanner (n=45, age=72.36±9.90 years), and the other on a GE Premier whole-body 3T scanner (WB3T) (n=48, age=75.15±9.77 years). ME-fMRI data were acquired using scanner-specific protocols as the gradients allow (C3T: TR=940ms; TEs=10.6/28.6/46.6ms; WB3T: TR=1350ms; TEs=16.7/43.4/70.1ms), with matched spatial resolution (2.4mm isotropic; 52 slices). T1-weighted anatomical images (1mm-isotropic) were also acquired. Pre-processing was performed using AFNI and FreeSurfer. TSNR was calculated within gray matter (GM). Fractional amplitude of low-frequency fluctuations (fALFF) was analyzed using CONN, and second-level analyses assessed correlations between fALFF and age. Statistical significance was assessed using voxel-wise threshold of p-uncorrected100.
Results
GM tSNR was significantly higher for ME-fMRI acquired on the C3T compared with the WB3T. Additionally, C3T data revealed a greater number of clusters showing significant correlations between fALFF and age. Significantly higher fALFF for C3T relative to WB3T was observed in the occipital lobe.
Conclusion
ME-fMRI acquired on the C3T demonstrates superior tSNR and improved sensitivity in fALFF analyses compared with a conventional WB3T scanner.