fMRI activation optimization in the setting of brain tumor-induced neurovascular uncoupling using resting state BOLD ALFF.

AIM: To demonstrate that a novel resting state BOLD ALFF (the amplitude of low-frequency fluctuation)-based correction method can substantially enhance the detectability of motor task activation in the presence of tumor-induced neurovascular uncoupling (NVU).

METHODS: Twelve de novo brain tumor patients who underwent comprehensive clinical BOLD fMRI exams including task fMRI and resting state fMRI (rsfMRI) were evaluated. Each patient displayed decreased/absent task fMRI activation in the primary ipsilesional primary motor cortex in the absence of corresponding motor deficit or suboptimal task performance, consistent with NVU. Z-score maps for the motor tasks were obtained from general linear model (GLM) analysis (reflecting motor activation vs. rest). ALFF maps were calculated from rsfMRI data using the REST (version 1.8) toolkit. Precentral and postcentral gyri in contralesional (CL) and ipsilesional (IL) hemispheres were parcellated using an Automated Anatomical Labeling (AAL) template for each patient. A novel ALFF-based correction method was used to identify the NVU affected voxels in the ipsilesional primary motor cortex (PMC), and a correction factor was applied to normalize the baseline Z-scores for these voxels.

RESULTS: In all cases, substantially greater activation was seen on post ALFF correction motor activation maps within the ipsilesional precentral gyri than in the pre ALFF correction activation maps.

CONCLUSION: We have demonstrated the feasibility of a new resting state ALFF-based technique for effective correction of brain tumor-related NVU in the primary motor cortex.