SU-G-IeP1-11: Resting-State Fluctuation of BOLD Signal Amplitude for Mapping Cerebrovascular Reactivity in Presurgical Functional MRI.
PURPOSE
Cerebrovascular reactivity (CVR) MRI with hypercapnia challenges, such as a breath-hold (BH) task, has been proposed to indicate areas with neurovascular uncoupling potentials for presurgical functional MRI (fMRI). This study aimed to explore the use of resting-state (RS) fMRI, in particular, the RS fluctuation of amplitude (RSFA) for detecting the impaired CVR and compare with BH MRI in patients with gliomas.


METHODS
The BH and RS fMRI from six patients as part of their presurgical fMRI studies were analyzed. Functional images were coregistered to the 3D T1-weighted images and spatially smoothed using a 4-mm Gaussian kernel. A band-pass filter (0.01-0.08 Hz) was then applied to the RS time series. Temporal standard deviations of the BH and the filtered RS signal changes were computed for each voxel to indicate CVR and subsequently transformed to Z-scores. For quantitative comparison, a region of interest (ROI) with significant CVR in the sensorimotor cortex on the contralateral side of the tumor was determined for each patient as Z-scores greater than 50% of the local maxima. In addition, a tumor ROI was determined by referencing the T2 FLAIR and post-contrast T1-weighted images of each patient.


RESULTS
Significant cross-subject correlations between the BH CVR and RSFA were found in both the sensorimotor and tumor ROIs (r=0.59, p<0.05 and r=0.83, p<0.05, respectively). Within individuals, voxel-based analyses showed significant correlations between two methods in both ROIs in all patients. The spatial patterns of BH CVR and RSFA maps appeared similar across the brain with sparse local discrepancies.


CONCLUSION
The RSFA derived from RS-fMRI is a promising method for probing impaired CVR in presurgical fMRI mapping. Unlike BH, RS-fMRI is less dependent on patient performance. In addition, with its proven relation to neural activity, RSFA of certain frequency bands has potentials to better indicate the neurovascular uncoupling.