High Multiband Acceleration Degrades Resting‐State Functional MRI Reliability and Signal Quality Under Anesthesia

Background and Purpose Resting‐state fMRI (rs‐fMRI) is increasingly used to map brain networks in patients under anesthesia, but technical factors can affect its utility. We evaluated the effects of sevoflurane, multiband acceleration, and scan duration on rs‐fMRI signal quality and within‐subject reliability under anesthesia. Methods We retrospectively analyzed 64 clinical rs‐fMRI scans acquired under anesthesia, with or without sevoflurane and multiband factor 5 acceleration. Temporal signal‐to‐noise ratio (tSNR) was used as a measure of signal quality. For each patient, the scan was split in half, and seed‐based connectivity maps were generated for the primary motor cortex (M1), posterior cingulate cortex (PCC), and subgenual anterior cingulate cortex (sgACC). Split‐half spatial correlations were used to assess within‐subject reliability. Group comparisons examined differences in tSNR and reliability across conditions, and correlations with scan duration were tested. Results Multiband acceleration was associated with significantly lower tSNR ( U = 652.0, p = 8.9 × 10─ 6 ) and reduced split‐half reliability for M1 ( p = 0.019), PCC ( p = 0.010), and sgACC ( p = 0.0064). Sevoflurane showed no significant effect on tSNR or reliability. Longer scan duration correlated with improved reliability for M1 ( r = 0.38, p = 0.003) but not for PCC or sgACC. No correlation was found between tSNR and reliability. Conclusion Hight multiband acceleration reduces both signal quality and reliability of rs‐fMRI under anesthesia. Sevoflurane had no measurable effect. The lack of correlation between tSNR and reliability underscores the need for more robust metrics when evaluating scan quality.